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Background: Arterial spin labeling (ASL) allows non‐invasive quantification of myocardial blood flow (MBF). Double‐ECG gating (DG) ASL is more robust to heart rate variability than single‐ECG gating (SG), but its reproducibility requires further investigation. Moreover, the existence of multiple quantification models hinders its application. Frequency‐offset‐corrected‐inversion (FOCI) pulses provide sharper edge profiles than hyperbolic‐secant (HS), which could benefit myocardial ASL. Purpose: To assess the performance of MBF quantification models for DG compared to SG ASL, to evaluate their reproducibility and to compare the effects of HS and FOCI pulses. Study Type: Prospective. Subjects: Sixteen subjects (27 ± 8 years). Field Strength/Sequence: 1.5 T/DG and SG flow‐sensitive alternating inversion recovery ASL. Assessment: Three models for DG MBF quantification were compared using Monte Carlo simulations and in vivo experiments. Two models used a fitting approach (one using only a single label and control image pair per fit, the other using all available image pairs), while the third model used a T1 correction approach. Slice profile simulations were conducted for HS and FOCI pulses with varying B0 and B1. Temporal signal‐to‐noise ratio (tSNR) was computed for different acquisition/quantification strategies and inversion pulses. The number of images that minimized MBF error was investigated in the model with highest tSNR. Intra and intersession reproducibility were assessed in 10 subjects. Statistical Tests: Within‐subject coefficient of variation, analysis of variance. P‐value <0.05 was considered significant. Results: MBF was not different across acquisition/quantification strategies (P = 0.27) nor pulses (P = 0.9). DG MBF quantification models exhibited significantly higher tSNR and superior reproducibility, particularly for the fitting model using multiple images (tSNR was 3.46 ± 2.18 in vivo and 3.32 ± 1.16 in simulations, respectively; wsCV = 16%). Reducing the number of ASL pairs to 13/15 did not increase MBF error (minimum = 0.22 mL/g/min). Data Conclusion: Reproducibility of MBF was better for DG than SG acquisitions, especially when employing a fitting model. Level of Evidence: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

Background: MR elastography (MRE) may provide quantitative imaging biomarkers of lumbar back muscles (LBMs), complementing MRI in spinal diseases by assessing muscle mechanical properties. However, reproducibility analyses for MRE of LBM are lacking. Purpose: To assess technical failure, within‐day and inter‐day reproducibility, robustness with the excitation source positioning, and inter‐observer agreement of MRE of muscles. Study Type: Prospective. Subjects: Seventeen healthy subjects (mean age 28 ± 4 years; 11 females). Field Strength/Sequence: 1.5 T, gradient‐echo MRE, T1‐weighted turbo spin echo. Assessment: The pneumatic driver was centered at L3 level. Four MRE were performed during two visits, 2–4 weeks apart, each consisting of two MRE with less than 10 minutes inter‐scan interval. At Visit 1, after the first MRE, the coil and driver were removed, then reinstalled. The MRE was repeated. At Visit 2, following the first MRE, only the driver was moved down 5 cm. The MRE was repeated. Two radiologists segmented the multifidus and erector spinae muscles. Statistical Tests: Paired t‐test, analysis of variance, intraclass correlation coefficients (ICCs). P‐values <0.05 were considered statistically significant. Results: Mean stiffness of LBM ranged from 1.44 to 1.60 kPa. Mean technical failure rate was 2.5%. Inter‐observer agreement was excellent (ICC ranging from 0.82 [0.64–0.96] to 0.99 [0.98–0.99] in the multifidus, and from 0.85 [0.69–0.92] to 0.99 [0.97–0.99] in the erector spinae muscles). Within‐day reproducibility was fair in the multifidus (ICC: 0.53 [0.47–0.77]) and good in the erector spinae muscles (ICC: 0.74 [0.48–0.88]). Reproducibility after moving the driver was excellent in both multifidus (ICC: 0.85 [0.69–0.93]) and erector spinae muscles (ICC: 0.84 [0.67–0.92]). Inter‐day reproducibility was excellent in the multifidus (ICC: 0.76 [0.48–0.89]) and poor in the erector spinae muscles (ICC: 0.23 [−0.61 to 0.63]). Data Conclusion: MRE of LBM provides measurements of stiffness with fair to excellent reproducibility and excellent inter‐observer agreement. However, inter‐day reproducibility in the multifidus muscles indicated that the herein used MRE protocol may not be optimal for this muscle. Evidence Level: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

Background: Maximum diameter measurements are used to assess the rupture risk of abdominal aortic aneurysms (AAAs); however, these are not precise enough to predict all ruptures. Four‐dimensional (4D) flow MRI‐derived parameters provide additional information by visualizing hemodynamics in AAAs but merit further investigation before they are clinically applicable. Purpose: To assess the reproducibility of 4D flow MRI‐derived hemodynamics, to investigate possible correlations with lumen and maximum diameter, and to explore potential relationships with vorticity and aneurysm growth. Study Type: Prospective single‐arm study. Population: A total of 22 (71.5 ± 6.1 years, 20 male) asymptomatic AAA patients with a maximum diameter of at least 30 mm. Field Strength/Sequence: A 3.0 T/Free‐breathing 4D flow MRI phase‐contrast acquisition with retrospective ECG‐gating. Assessment: Patients underwent two consecutive 4D flow MRI scans 1‐week apart. Aortic volumes were segmented from time‐averaged phase contrast magnetic resonance angiographies. Reproducibility was assessed by voxelwise analysis after registration. Mean flow velocity, mean wall shear stress (WSS), mean lumen diameter, and qualitative vorticity scores were assessed. In addition, Dixon MRI and retrospective surveillance data were used to study maximum diameter (including thrombus), intraluminal thrombus volume (ILT), and growth rate. Statistical Tests: For reproducibility assessment, Bland–Altman analyses, Pearson correlation, Spearman's correlation, and orthogonal regression were conducted. Potential correlations between hemodynamics and vorticity scores were assessed using linear regression. P < 0.05 was considered statistically significant. Results: Test–retest median Pearson correlation coefficients for flow velocity and WSS were 0.85 (IQR = 0.08) m/sec and 0.82 (IQR = 0.10) Pa, respectively. Mean WSS significantly correlated with mean flow velocity (R = 0.75) and inversely correlated with mean lumen diameter (R = −0.73). No significant associations were found between 4D flow MRI‐derived hemodynamic parameters and maximum diameter (flow velocity: P = 0.98, WSS: P = 0.22). Data Conclusion: A 4D flow MRI is robust for assessing the hemodynamics within AAAs. No correlations were found between hemodynamic parameters and maximum diameter, ILT volume and growth rate. Level of Evidence: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: Different MR elastography (MRE) systems may produce different stiffness measurements, making direct comparison difficult in multi‐center investigations. Purpose: To assess the repeatability and reproducibility of liver stiffness measured by three typical MRE systems. Study Type: Prospective. Population/Phantoms: Thirty volunteers without liver disease history (20 males, aged 21–28)/5 gel phantoms. Field Strength/Sequence: 3.0 T United Imaging Healthcare (UIH), 1.5 T Siemens Healthcare, 3.0 T General Electric Healthcare (GE)/Echo planar imaging‐based MRE sequence. Assessment: Wave images of volunteers and phantoms were acquired by three MRE systems. Tissue stiffness was evaluated by two observers, while phantom stiffness was assessed automatically by code. The reproducibility across three MRE systems was quantified based on the mean stiffness of each volunteer and phantom. Statistical Tests: Intraclass correlation coefficients (ICC), coefficients of variation (CV), and Bland–Altman analyses were used to assess the interobserver reproducibility, the interscan repeatability, and the intersystem reproducibility. Paired t‐tests were performed to assess the interobserver and interscan variation. Friedman tests with Dunn's multiple comparison correction were performed to assess the intersystem variation. P values less than 0.05 indicated significant difference. Results: The reproducibility of stiffness measured by the two observers demonstrated consistency with ICC > 0.92, CV < 4.32%, Mean bias < 2.23%, and P > 0.06. The repeatability of measurements obtained using the electromagnetic system for the liver revealed ICC > 0.96, CV < 3.86%, Mean bias < 0.19%, P > 0.90. When considering the range of reproducibility across the three systems for liver evaluations, results ranged with ICCs from 0.70 to 0.87, CVs from 6.46% to 10.99%, and Mean biases between 1.89% and 6.30%. Phantom studies showed similar results. The values of measured stiffness differed across all three systems significantly. Data Conclusion: Liver stiffness values measured from different MRE systems can be different, but the measurements across the three MRE systems produced consistent results with excellent reproducibility. Evidence Level: 1 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: Monoexponential apparent diffusion coefficient (ADC) and biexponential intravoxel incoherent motion (IVIM) analysis of diffusion‐weighted imaging is helpful in the characterization of breast tumors. However, repeatability/reproducibility studies across scanners and across sites are scarce. Purpose: To evaluate the repeatability and reproducibility of ADC and IVIM parameters (tissue diffusivity (Dt), perfusion fraction (Fp) and pseudo‐diffusion (Dp)) within and across sites employing MRI scanners from different vendors utilizing 16‐channel breast array coils in a breast diffusion phantom. Study Type: Phantom repeatability. Phantom: A breast phantom containing tubes of different polyvinylpyrrolidone (PVP) concentrations, water, fat, and sponge flow chambers, together with an MR‐compatible liquid crystal (LC) thermometer. Field Strength/Sequence: Bipolar gradient twice‐refocused spin echo sequence and monopolar gradient single spin echo sequence at 3 T. Assessment: Studies were performed twice in each of two scanners, located at different sites, on each of 2 days, resulting in four studies per scanner. ADCs of the PVP and water were normalized to the vendor‐provided calibrated values at the temperature indicated by the LC thermometer for repeatability/reproducibility comparisons. Statistical Tests: ADC and IVIM repeatability and reproducibility within and across sites were estimated via the within‐system coefficient of variation (wCV). Pearson correlation coefficient (r) was also computed between IVIM metrics and flow speed. A P value <0.05 was considered statistically significant. Results: ADC and Dt demonstrated excellent repeatability (<2%; <3%, respectively) and reproducibility (both <5%) at the two sites. Fp and Dp exhibited good repeatability (mean of two sites 3.67% and 5.59%, respectively) and moderate reproducibility (mean of two sites 15.96% and 13.3%, respectively). The mean intersite reproducibility (%) of Fp/Dp/Dt was 50.96/13.68/5.59, respectively. Fp and Dt demonstrated high correlations with flow speed while Dp showed lower correlations. Fp correlations with flow speed were significant at both sites. Data Conclusion: IVIM reproducibility results were promising and similar to ADC, particularly for Dt. The results were reproducible within both sites, and a progressive trend toward reproducibility across sites except for Fp. Level of Evidence: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

Background: Uncontrollable body movements are typical symptoms of Parkinson's disease (PD), which results in inconsistent findings regarding resting‐state functional connectivity (rsFC) networks, especially for group difference clusters. Systematically identifying the motion‐associated data was highly demanded. Purpose: To determine data censoring criteria using a quantitative cross validation‐based data censoring (CVDC) method and to improve the detection of rsFC deficits in PD. Study Type: Prospective. Subjects: Forty‐one PD patients (68.63 ± 9.17 years, 44% female) and 20 healthy controls (66.83 ± 12.94 years, 55% female). Field Strength/Sequence: 3‐T, T1‐weighted gradient echo and EPI sequences. Assessment: Clusters with significant differences between groups were found in three visual networks, default network, and right sensorimotor network. Five‐fold cross‐validation tests were performed using multiple motion exclusion criteria, and the selected criteria were determined based on cluster sizes, significance values, and Dice coefficients among the cross‐validation tests. As a reference method, whole brain rsFC comparisons between groups were analyzed using a FMRIB Software Library (FSL) pipeline with default settings. Statistical Tests: Group difference clusters were calculated using nonparametric permutation statistics of FSL‐randomize. The family‐wise error was corrected. Demographic information was evaluated using independent sample t‐tests and Pearson's Chi‐squared tests. The level of statistical significance was set at P < 0.05. Results: With the FSL processing pipeline, the mean Dice coefficient of the network clusters was 0.411, indicating a low reproducibility. With the proposed CVDC method, motion exclusion criteria were determined as frame‐wise displacement >0.55 mm. Group‐difference clusters showed a mean P‐value of 0.01 and a 72% higher mean Dice coefficient compared to the FSL pipeline. Furthermore, the CVDC method was capable of detecting subtle rsFC deficits in the medial sensorimotor network and auditory network that were unobservable using the conventional pipeline. Data Conclusion: The CVDC method may provide superior sensitivity and improved reproducibility for detecting rsFC deficits in PD. Level of Evidence: 1 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: Simultaneous multi‐slice diffusion‐weighted imaging (SMS‐DWI) can shorten acquisition time in abdominal imaging. Purpose: To investigate the agreement and reproducibility of apparent diffusion coefficient (ADC) from abdominal SMS‐DWI acquired with different vendors and different breathing schemes. Study Type: Prospective. Subjects: Twenty volunteers and 10 patients. Field Strength/Sequence: 3.0 T, SMS‐DWI with a diffusion‐weighted echo‐planar imaging sequence. Assessment: SMS‐DWI was acquired using breath‐hold and free‐breathing techniques in scanners from two vendors, yielding four scans in each participant. Average ADC values were measured in the liver, pancreas, spleen, and both kidneys. Non‐normalized ADC and ADCs normalized to the spleen were compared between vendors and breathing schemes. Statistical Tests: Paired t‐test or Wilcoxon signed rank test; intraclass correlation coefficient (ICC); Bland–Altman method; coefficient of variation (CV) analysis; significance level: P < 0.05. Results: Non‐normalized ADCs from the four SMS‐DWI scans did not differ significantly in the spleen (P = 0.262, 0.330, 0.166, 0.122), right kidney (P = 0.167, 0.538, 0.957, 0.086), and left kidney (P = 0.182, 0.281, 0.504, 0.405), but there were significant differences in the liver and pancreas. For normalized ADCs, there were no significant differences in the liver (P = 0.315, 0.915, 0.198, 0.799), spleen (P = 0.815, 0.689, 0.347, 0.423), pancreas (P = 0.165, 0.336, 0.304, 0.584), right kidney (P = 0.165, 0.336, 0.304, 0.584), and left kidney (P = 0.496, 0.304, 0.443, 0.371). Inter‐reader agreements of non‐normalized ADCs were good to excellent (ICCs ranged from 0.861 to 0.983), and agreement and reproducibility were good to excellent depending on anatomic location (CVs ranged from 3.55% to 13.98%). Overall CVs for abdominal ADCs from the four scans were 6.25%, 7.62%, 7.08, and 7.60%. Data Conclusion: The normalized ADCs from abdominal SMS‐DWI may be comparable between different vendors and breathing schemes, showing good agreement and reproducibility. ADC changes above approximately 8% may potentially be considered as a reliable quantitative biomarker to assess disease or treatment‐related changes. Level of Evidence: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: There exist several fMRI quality assurance measures to assess scanner stability. Because they have practical and/or theoretical limitations, a different and more practical measure for instability would be desirable. Purpose: To develop and test a sensitive, reliable and widely applicable temporal instability measure (TIM) for fMRI quality assurance. Study Type: Technical development. Phantom: Spherical gel phantom. Population: A total of 120 datasets from a local Philips scanner with two different receive‐only head coils (32ch and 8ch, 60 datasets per coil) were collected as well as 29 additional datasets with three different receive‐only head coils (20ch, 32ch, and 64ch) from two additional sites with GE (seven runs with 32ch) and Siemens scanners (seven runs with 32ch and Multiband imaging, five runs with 20ch, 32ch, and 64ch) were borrowed. Field Strength/Sequence: 2D Echo‐planar‐imaging (EPI). Assessment: A new TIM was proposed that is based on the eigenratio of the correlation coefficient matrix, where each entry of the matrix is a correlation coefficient between two time‐points of the time‐series. Statistical Tests: Nonparametric bootstrap resampling was used twice to estimate confidence intervals (CI) of the TIM values and to assess the improved sensitivity of this measure. Differences in coil performance were assessed via a nonparametric bootstrap two‐sample t‐test. P‐values <0.05 were considered significant. Results: The TIM values ranged between 60 parts‐per‐million and 10,780 parts‐per‐million across all 149 experiments. The mean CI was 2.96% and 2.16% for the 120 and 29 fMRI datasets, respectively (the repeated bootstrap analysis gave 2.9% and 2.19%, respectively). The 32ch coils of the local Philips data provided more stable measurements than the 8ch coil (observed two‐sample t‐values = 26.36, −0.2 and −6.2 for TIM, tSNR, and RDC, respectively. PtSNR = 0.58). Data Conclusion: The proposed TIM is particularly useful for multichannel coils with spatially nonuniform receive sensitivity and overcomes several limitations of other measures. As such, it provides a reliable test for ascertaining scanner stability for fMRI experiments. Evidence Level: 5. Technical Efficacy: Stage 1. [ABSTRACT FROM AUTHOR]

Background: The recommended technique for breast diffusion‐weighted imaging (DWI) acquisitions is not sufficiently standardized in clinical practice. Purpose: To investigate the intraobserver and interobserver reproducibility of DWI measurements, diffusion‐kurtosis imaging (DKI) parameters, and image quality evaluation in breast lesions between single‐shot echo‐planar imaging (ss‐EPI) and readout‐segmented echo‐planar imaging (rs‐EPI). Study Type: Prospective. Population: A total of 295 women with 209 malignant and 86 benign breast lesions. Field Strength/Sequence: A 3‐T; fat‐saturated T2‐weighted MR imaging (T2WI); multi‐b‐value DWI with both ss‐EPI and rs‐EPI readouts; T1‐weighted dynamic contrast‐enhanced MRI (DCE‐MRI). Assessment: Mean kurtosis (MK), mean diffusion (MD), and apparent diffusion coefficient (ADC) values were measured for each lesion on ss‐EPI and rs‐EPI, respectively. Image quality was visually evaluated regarding image sharpness, geometric distortion, lesion conspicuity, visualization of anatomic structures, and overall quality. Quantitative and qualitative analyses were performed twice with a time interval of 2 weeks. Statistical Tests: Intraobserver and interobserver reproducibility were evaluated using intra‐class correlation coefficients (ICC), within‐subject coefficient of variation (wCV), and Bland–Altman plots. Results: MK, MD, and ADC quantitative parameters for breast lesions showed excellent intraobserver and interobserver reproducibility, with ICCs >0.75 and wCV values ranging from 2.51% to 7.08% for both sequences. The wCV values in both intraobserver and interobserver measurements were higher in the ss‐EPI sequence (3.63%–7.08%) than that of the rs‐EPI sequence (2.51%–3.62%). The wCV values differed in subgroups with different histopathological types of lesions, breast density, lesion morphology, and lesion sizes, respectively. Furthermore, rs‐EPI (ICCs, 0.76–0.97; wCV values, 2.41%–6.04%) had better intraobserver and interobserver reproducibility than ss‐EPI (ICCs, 0.54–0.90; wCV values, 6.18%–13.69%) with regard to image quality. Data Conclusion: Compared to the ss‐EPI, the rs‐EPI sequence showed higher intraobserver and interobserver reproducibility for quantitative diffusion‐related parameters and image quality assessments measured in breast DWI and DKI. Evidence Level: 2. Technical Efficacy: Stage 2. [ABSTRACT FROM AUTHOR]

Background: Manually segmenting cardiac structures is time‐consuming and produces variability in MRI assessments. Automated segmentation could solve this. However, current software is developed for adults without congenital heart defects (CHD). Purpose: To evaluate automated segmentation of left ventricle (LV) and right ventricle (RV) for pediatric MRI studies. Study Type: Retrospective comparative study. Population: Twenty children per group of: healthy children, LV‐CHD, tetralogy of Fallot (ToF), and univentricular CHD, aged 11.7 [8.9–16.0], 14.2 [10.6–15.7], 14.6 [11.6–16.4], and 12.2 [10.2–14.9] years, respectively. Sequence/Field Strength: Balanced steady‐state free precession at 1.5 T. Assessment: Biventricular volumes and masses were calculated from a short‐axis stack of images, which were segmented manually and using two fully automated software suites (Medis Suite 3.2, Medis, Leiden, the Netherlands and SuiteHeart 5.0, Neosoft LLC, Pewaukee, USA). Fully automated segmentations were manually adjusted to provide two further sets of segmentations. Fully automated and adjusted automated segmentation were compared to manual segmentation. Segmentation times and reproducibility for each method were assessed. Statistical Tests: Bland Altman analysis and intraclass correlation coefficients (ICC) were used to compare volumes and masses between methods. Postprocessing times were compared by paired t‐tests. Results: Fully automated methods provided good segmentation (ICC > 0.90 compared to manual segmentation) for the LV in the healthy and left‐sided CHD groups (eg LV‐EDV difference for healthy children 1.4 ± 11.5 mL, ICC: 0.97, for Medis and 3.0 ± 12.2 mL, ICC: 0.96 for SuiteHeart). Both automated methods gave larger errors (ICC: 0.62–0.94) for the RV in these populations, and for all structures in the ToF and univentricular CHD groups. Adjusted automated segmentation agreed well with manual segmentation (ICC: 0.71–1.00), improved reproducibility and reduced segmentation time in all patient groups, compared to manual segmentation. Data Conclusion: Fully automated segmentation eliminates observer variability but may produce large errors compared to manual segmentation. Manual adjustments reduce these errors, improve reproducibility, and reduce postprocessing times compared to manual segmentation. Adjusted automated segmentation is reasonable in children with and without CHD. Evidence Level: 3. Technical Efficacy: Stage 2. [ABSTRACT FROM AUTHOR]

Background: Decreased cerebrovascular reactivity, measured as changes in blood‐oxygen‐level‐dependent (BOLD) signal, is a potential new cerebral amyloid angiopathy (CAA) severity marker. Before clinical application, the effect of aging on BOLD parameters, and reproducibility and test–retest reliability of these parameters should be assessed. Purpose: Assess the effect of healthy aging on cerebrovascular reactivity (BOLD amplitude, time to peak, and time to baseline). And determine reproducibility and test–retest reliability of these parameters. Study Type: Prospective‐observational. Population: Eighty‐six healthy adults (mean age 56 years, 55% female), 10 presymptomatic D‐CAA mutation carriers (mean age 34 years, 70% female), and 10 symptomatic D‐CAA mutation carriers (mean age 54 years, 70% female). Field Strength/Sequence: 3‐T, three‐dimensional (3D) T1‐weighted MRI and gradient echo BOLD fMRI. Assessment: To assess test–retest reliability of BOLD parameters, i.e. BOLD amplitude, time to peak, and time to baseline, BOLD fMRI scans were repeated three times immediately after each other, in both controls and mutation carriers. To assess reproducibility, BOLD fMRI scans were repeated with a 3‐week interval for each subject. Statistical Tests: Linear regression analyses and two‐way mixed absolute agreement intra‐class correlation approach. Results: Healthy aging was associated with decreased BOLD amplitude (β = −0.711) and prolonged time to baseline (β = 0.236) in the visual cortex after visual stimulation Reproducibility of BOLD amplitude was excellent (ICC 0.940) in the subgroup of healthy adults. Test–retest reliability for BOLD amplitude was excellent in healthy adults (ICC 0.856–0.910) and presymptomatic D‐CAA mutation carriers (ICC 0.959–0.981). In symptomatic D‐CAA mutation carriers, test–retest reliability was poor for all parameters (ICCs < 0.5). Data Conclusion: Healthy aging is associated with decreased cerebrovascular reactivity, measured by changes in BOLD response to visual stimulation. The BOLD amplitude appears to be a robust measurement in healthy adults and presymptomatic D‐CAA mutation carriers, but not in symptomatic D‐CAA mutation carriers. [ABSTRACT FROM AUTHOR]

Background: To date, the accuracy and variability of diffusion‐weighted MRI (DW‐MRI) metrics have been reported in a limited number of scanner/protocol/coil combinations. Purpose: To evaluate the reproducibility of DW‐MRI estimates across multiple scanners and DW‐MRI protocols and to assess the effects of using an 8‐channel vs. 16‐channel breast coil in a breast phantom. Study Type: Prospective. Phantom: Breast phantom containing tubes of water and differing polyvinylpyrrolidone (PVP) concentrations with apparent diffusion coefficients (ADCs) matching breast tissue. Field Strength/Sequence: 3 T (three standard and one wide bore), three DW‐MRI single‐shot echo planar imaging protocols of varying acquired spatial resolution. Assessment: Accuracy of estimated ADCs was assessed using percent differences (PD) relative to nuclear magnetic resonance spectroscopy‐derived reference values. Coefficients of variation (CV) were calculated to determine variation across scanners. CVs based on the median standard deviation (CVM) were used to evaluate tube‐specific dispersion using 8‐ or 16‐channel coils at a single scanner. ADCs of PVP‐containing tubes were additionally normalized by the median water tube ADC to account for temperature effects. Statistical Tests: Two‐way repeated measures analysis of variance and post hoc tests were used to evaluate differences in ADC, CV, and CVM across scanners and protocols (α = 0.05). Results: ADCs were within 11% (interquartile range [IQR] 7%) of reference values and significantly improved to 2% (IQR 7%) after normalization to an internal water reference. Normalization significantly reduced interscanner variability of ADC estimates from 7% to 4%. DW‐MRI protocol did not affect ADC accuracy; however, the clinical and higher‐resolution clinical protocols resulted in the greatest (9%) and least (6%) interscanner variability, respectively. The 8‐ and 16‐channel receive coils yielded similar accuracy (PD: 12% vs. 16%) and precision (CVM: 2.7% vs. 2.9%). Data Conclusion: Normalization by an internal reference improved interscanner ADC reproducibility. High‐resolution protocols yielded comparably accurate and significantly less variable ADCs compared to a clinical standard protocol. Evidence Level: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

BackgroundQuantitative diffusion-weighted imaging (DWI) MRI is a promising technique for cancer characterization and treatment monitoring. Knowledge of the reproducibility of DWI metrics in breast tumors is necessary to apply DWI as a clinical biomarker.PurposeTo evaluate the repeatability and reproducibility of breast tumor apparent diffusion coefficient (ADC) in a multi-institution clinical trial setting, using standardized DWI protocols and quality assurance (QA) procedures.Study typeProspective.SubjectsIn all, 89 women from nine institutions undergoing neoadjuvant chemotherapy for invasive breast cancer.Field strength/sequenceDWI was acquired before and after patient repositioning using a four b-value, single-shot echo-planar sequence at 1.5T or 3.0T.AssessmentA QA procedure by trained operators assessed artifacts, fat suppression, and signal-to-noise ratio, and determine study analyzability. Mean tumor ADC was measured via manual segmentation of the multislice tumor region referencing DWI and contrast-enhanced images. Twenty cases were evaluated multiple times to assess intra- and interoperator variability. Segmentation similarity was assessed via the Sørenson-Dice similarity coefficient.Statistical testsRepeatability and reproducibility were evaluated using within-subject coefficient of variation (wCV), intraclass correlation coefficient (ICC), agreement index (AI), and repeatability coefficient (RC). Correlations were measured by Pearson's correlation coefficients.ResultsIn all, 71 cases (80%) passed QA evaluation: 44 at 1.5T, 27 at 3.0T; 60 pretreatment, 11 after 3 weeks of taxane-based treatment. ADC repeatability was excellent: wCV = 4.8% (95% confidence interval [CI] 4.0, 5.7%), ICC = 0.97 (95% CI 0.95, 0.98), AI = 0.83 (95% CI 0.76, 0.87), and RC = 0.16 * 10-3 mm2 /sec (95% CI 0.13, 0.19). The results were similar across field strengths and timepoint subgroups. Reproducibility was excellent: interreader ICC = 0.92 (95% CI 0.80, 0.97) and intrareader ICC = 0.91 (95% CI 0.78, 0.96).Data conclusionBreast tumor ADC can be measured with excellent repeatability and reproducibility in a multi-institution setting using a standardized protocol and QA procedure. Improvements to DWI image quality could reduce loss of data in clinical trials.Level of evidence2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2019;49:1617-1628.

Background: Amide proton transfer (APT) imaging is a chemical exchange saturation transfer (CEST) technique offering potential clinical applications such as diagnosis, characterization, and treatment planning and monitoring in glioma patients. While APT‐CEST has demonstrated high potential, reproducibility remains underexplored. Purpose: To investigate whether cerebral APT‐CEST with clinically feasible scan time is reproducible in healthy tissue and glioma for clinical use at 3 T. Study Type: Prospective, longitudinal. Subjects: Twenty‐one healthy volunteers (11 females; mean age ± SD: 39 ± 11 years) and 6 glioma patients (3 females; 50 ± 17 years: 4 glioblastomas, 1 oligodendroglioma, 1 radiologically suspected low‐grade glioma). Field Strength/Sequence: 3 T, Turbo Spin Echo ‐ ampling perfection with application optimized contrasts using different flip angle evolution ‐ chemical exchange saturation transfer (TSE SPACE‐CEST). Assessment: APT‐CEST measurement reproducibility was assessed within‐session (glioma patients, scan session 1; healthy volunteers scan sessions 1, 2, and 3), between‐sessions (healthy volunteers scan sessions 1 and 2), and between‐days (healthy volunteers, scan sessions 1 and 3). The mean APTCEST values and standard deviation of the within‐subject difference (SDdiff) were calculated in whole tumor enclosed by regions of interest (ROIs) in patients, and eight ROIs in healthy volunteers—whole‐brain, cortical gray matter, putamen, thalami, orbitofrontal gyri, occipital lobes, central brain—and compared. Statistical Tests: Brown‐Forsythe tests and variance component analysis (VCA) were used to assess the reproducibility of ROIs for the three time intervals. Significance was set at P < 0.003 after Bonferroni correction. Results: Intratumoral mean APTCEST was significantly higher than APTCEST in healthy‐appearing tissue in patients (0.5 ± 0.46%). The average within‐session, between‐sessions, and between‐days SDdiff of healthy control brains was 0.2% and did not differ significantly with each other (0.76 > P > 0.22). The within‐session SDdiff of whole‐brain was 0.2% in both healthy volunteers and patients, and 0.21% in the segmented tumor. VCA showed that within‐session factors were the most important (60%) for scanning variance. Data Conclusion: Cerebral APT‐CEST imaging may show good scan–rescan reproducibility in healthy tissue and tumors with clinically feasible scan times at 3 T. Short‐term measurement effects may be the dominant components for reproducibility. Level of Evidence: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

PurposeTo compare performance of sequential and Hadamard-encoded pseudocontinuous arterial spin labeling (PCASL).Materials and methodsMonte Carlo simulations and in vivo experiments were performed in 10 healthy subjects. Field strength and sequence: 5-delay sequential (5-del. Seq.), 7-delay Hadamard-encoded (7-del. Had.), and a single-delay (1-del.) PCASL, without and with vascular crushing at 3.0T. The errors and variations of cerebral blood flow (CBF) and arterial transit time (ATT) from simulations and the CBF and ATT estimates and variations in gray matter (GM) with different ATT ranges were compared. Pairwise t-tests with Bonferroni correction were used.ResultsThe simulations and in vivo experiments showed that 1-del. PCASL underestimated GM CBF due to insufficient postlabeling delay (PLD) (37.2 ± 8.1 vs. 47.3 ± 8.5 and 47.3 ± 9.0 ml/100g/min, P ≤ 6.5 × 10-6 ), while 5-del. Seq. and 7-del. Had. yielded comparable GM CBF (P ≥ 0.49). 5-del. Seq. was more reproducible for CBF (P = 4.7 × 10-4 ), while 7-del. Had. was more reproducible for ATT (P = 0.033). 5-del. Seq. was more prone to intravascular artifacts and yielded lower GM ATTs compared to 7-del. Had. without crushing (1.13 ± 0.18 vs. 1.23 ± 0.13 seconds, P = 2.3 × 10-3 ), but they gave comparable ATTs with crushing (P = 0.12). ATTs measured with crushing were longer than those without crushing (P ≤ 6.7 × 10-4 ), but CBF was not affected (P ≥ 0.16).ConclusionThe theoretical signal-to-noise ratio (SNR) gain through Hadamard encoding was confirmed experimentally. For 1-del., a PLD of 1.8 seconds is recommended for healthy subjects. With current parameters, 5-del. Seq. was more reproducible for CBF, and 7-del. Had. for ATT. Vascular crushing may help reduce variations in multidelay experiments without compromising tissue CBF or ATT measurements.Level of evidence1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;47:1119-1132.

Background: Radiomics is the high throughput analysis of medical images using computer algorithms, which specifically assess textural features. It has increasingly been proposed as a tool for the development of imaging biomarkers. However, an important acknowledged limitation of radiomics is the lack of reproducibility of features produced. Purpose: To assess reproducibility and repeatability of radiomics variables in brain MRI through a multivisit, multicenter study. Study Type: Retrospective. Population: Fourteen individuals visiting three institutions twice, 10 males with the mean age of 36.3 years and age range 25–51. Field Strength 3D T1W inversion recovery on three 1.5‐T General Electric scanners. Assessment Radiomics analysis by a consultant radiologist performed on the T1W images of the whole brain on all visits. All possible radiomics features were generated. Statistical Test: Concordance correlation coefficient (CCC) and dynamic range (DR) for all variables were calculated to assess the test–retest repeatability. Intraclass correlation coefficients (ICCs) were calculated to investigate the reproducibility of features across centers. Results: Of 1596 features generated, 57 from center 1, 15 from center 2, and 22 from center 3 had a CCC > 0.9 and DR > 0.9. Eight variables had CCC > 0.9 and DR > 0.9 in all centers. Forty‐one variables had an ICC of >0.9. No variables had CCC > 0.9, DR > 0.9, and ICC > 0.9. Data Conclusion: Repeatability and reproducibility of variables is a significant limitation of radiomics analysis in 3DT1W brain MRI. Careful selection of radiomic features is required. Level of Evidence: 4 Technical Efficacy Stage: 2 [ABSTRACT FROM AUTHOR]

Background: Three‐dimensional variable flip angle (VFA) methods are commonly used for T1 mapping of the liver, but there is no data on the accuracy, repeatability, and reproducibility of this technique in this organ in a multivendor setting. Purpose: To measure bias, repeatability, and reproducibility of VFA T1 mapping in the liver. Study Type: Prospective observational. Population: Eight healthy volunteers, four women, with no known liver disease. Field Strength/Sequence: 1.5‐T and 3.0‐T; three‐dimensional steady‐state spoiled gradient echo with VFAs; Look‐Locker. Assessment: Traveling volunteers were scanned twice each (30 minutes to 3 months apart) on six MRI scanners from three vendors (GE Healthcare, Philips Medical Systems, and Siemens Healthineers) at two field strengths. The maximum period between the first and last scans among all volunteers was 9 months. Volunteers were instructed to abstain from alcohol intake for at least 72 hours prior to each scan and avoid high cholesterol foods on the day of the scan. Statistical Tests: Repeated measures ANOVA, Student t‐test, Levene's test of variances, and 95% significance level. The percent error relative to literature liver T1 in healthy volunteers was used to assess bias. The relative error (RE) due to intrascanner and interscanner variation in T1 measurements was used to assess repeatability and reproducibility. Results: The 95% confidence interval (CI) on the mean bias and mean repeatability RE of VFA T1 in the healthy liver was 34 ± 6% and 10 ± 3%, respectively. The 95% CI on the mean reproducibility RE at 1.5 T and 3.0 T was 29 ± 7% and 25 ± 4%, respectively. Data Conclusion: Bias, repeatability, and reproducibility of VFA T1 mapping in the liver in a multivendor setting are similar to those reported for breast, prostate, and brain. Level of Evidence: 1 Technical Efficacy Stage: 1 [ABSTRACT FROM AUTHOR]

Background: Magnetization transfer saturation (MTsat) imaging was developed to reduce T1 dependence and improve specificity to myelin, compared to the widely used MT ratio (MTR) approach, while maintaining a feasible scan time. As MTsat imaging is an emerging technique, the reproducibility of MTsat compared to MTR must be evaluated. Purpose: To assess the test–retest reproducibility of MTR and MTsat in the mouse brain at 9.4 T and calculate sample sizes potentially required to detect effect sizes ranging from 6% to 14%. Study Type: Prospective. Subjects: Twelve healthy C57Bl/6 mice. Field Strength/Sequence: 9.4 T; magnetization transfer imaging using FLASH‐3D Gradient Echo; T2‐weighted TurboRARE spin echo. Assessment: All mice were scanned at two timepoints (5 days apart). MTR and MTsat maps were analyzed using mean region‐of‐interest (ROIs: corpus callosum [CC], internal capsule [IC], hippocampus [HC], cortex [CX], and thalamus [TH]), and whole brain voxel‐wise analysis. Statistical Tests: Bland–Altman plots were used to assess biases between test–retest measurements. Test–retest reproducibility was evaluated via between and within‐subject coefficients of variation (bsCV and wsCV, respectively). Sample sizes required were calculated (significance level: 95%; power: 80%), given effect sizes ranging from 6% to 14%, using both between and within‐subject approaches. Results were considered statistically significant at P ≤ 0.05. Results: Bland–Altman plots showed negligible biases between test–retest sessions (MTR: 0.0009; MTsat: 0). ROI‐based and voxel‐wise CVs revealed high reproducibility for both MTR (ROI‐bsCV/wsCV: CC—4.5/2.8%; IC—6.1/5.2%; HC—5.7/4.6%; CX—5.1/2.3%; TH—7.4/4.9%) and MTsat (ROI‐bsCV/wsCV: CC—6.3/4.8%; IC—7.3/5.1%; HC—9.5/6.4%; CX—6.7/6.5%; TH—7.2/5.3%). With a sample size of 6, changes on the order of 15% could be detected in MTR and MTsat, both between and within subjects, while smaller changes (6%–8%) required sample sizes of 10–15 for MTR, and 15–20 for MTsat. Data Conclusion: MTsat exhibited comparable reproducibility to MTR, while providing sensitivity to myelin with less T1 dependence than MTR. Evidence Level: 2 Technical Efficacy: Stage 1 [ABSTRACT FROM AUTHOR]

Background: Glutathione (GSH) is an important brain antioxidant and a number of studies have reported its measurement by edited and nonedited localized 1H spectroscopy techniques within a range of applications in healthy volunteers and disease states. Good test–retest reproducibility is key when assessing the efficacy of treatments aimed at modulating GSH levels within the central nervous system or when noninvasively assessing changes in GSH content over time. Purpose To evaluate the intraday (in vitro and in vivo) and 1‐month apart (in vivo) test–retest reproducibility of GSH measurements from GSH‐edited MEGA‐PRESS acquisitions at 3 T in a phantom and in the brain of a cohort of middle‐aged and older healthy volunteers. Study Type: Prospective. Subjects/Phantoms: A phantom containing physiological concentrations of GSH and metabolites with overlapping spectral signatures and 10 healthy volunteers (4 F, 6 M, 55 ± 14 years old). Field strength/Sequence: GSH‐edited spectra were acquired at 3 T using the MEGA‐PRESS sequence. Assessment The phantom was scanned twice and the healthy subjects were scanned three times (on two separate days, 1 month apart). GSH was quantified from each acquisition, with the in vivo voxels placed at the primary motor cortex (PMC) and the occipital cortex (OCC). Statistical Tests: Mean coefficients of variation (CV) were used to assess short‐term (in vitro and in vivo) and longer‐term (in vivo) test–retest reproducibility. Results: In vitro, the CV was 2.3%. In vivo, the mean intraday CV was 3.3% in the PMC and 2.4% in the OCC, while the CVs at 1 month apart were 4.6% in the PMC and 7.8% in the OCC. Data Conclusion: GSH‐edited MEGA‐PRESS spectroscopy allows measurement of GSH with excellent precision. Evidence Level 1 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: Implementation of four‐dimensional flow magnetic resonance (4D Flow MR) in clinical routine requires awareness of confounders. Purpose To investigate inter‐vendor comparability of 4D Flow MR derived aortic hemodynamic parameters, assess scan‐rescan repeatability, and intra‐ and interobserver reproducibility. Study Type: Prospective multicenter study. Population: Fifteen healthy volunteers (age 24.5 ± 5.3 years, 8 females). Field Strength/Sequence: 3 T, vendor‐provided and clinically used 4D Flow MR sequences of each site. Assessment Forward flow volume, peak velocity, average, and maximum wall shear stress (WSS) were assessed via nine planes (P1–P9) throughout the thoracic aorta by a single observer (AD, 2 years of experience). Inter‐vendor comparability as well as scan‐rescan, intra‐ and interobserver reproducibility were examined. Statistical Tests: Equivalence was tested setting the 95% confidence interval of intraobserver and scan‐rescan difference as the limit of clinical acceptable disagreement. Intraclass correlation coefficient (ICC) and Bland–Altman plots were used for scan‐rescan reproducibility and intra‐ and interobserver agreement. A P‐value <0.05 was considered statistically significant. ICCs ≥ 0.75 indicated strong correlation (>0.9: excellent, 0.75–0.9: good). Results: Ten volunteers finished the complete study successfully. 4D flow derived hemodynamic parameters between scanners of three different vendors are not equivalent exceeding the equivalence range. P3–P9 differed significantly between all three scanners for forward flow (59.1 ± 13.1 mL vs. 68.1 ± 12.0 mL vs. 55.4 ± 13.1 mL), maximum WSS (1842.0 ± 190.5 mPa vs. 1969.5 ± 398.7 mPa vs. 1500.6 ± 247.2 mPa), average WSS (1400.0 ± 149.3 mPa vs. 1322.6 ± 211.8 mPa vs. 1142.0 ± 198.5 mPa), and peak velocity between scanners I vs. III (114.7 ± 12.6 cm/s vs. 101.3 ± 15.6 cm/s). Overall, the plane location at the sinotubular junction (P1) presented most inter‐vendor stability (forward: 78.5 ± 15.1 mL vs. 80.3 ± 15.4 mL vs. 79.5 ± 19.9 mL [P = 0.368]; peak: 126.4 ± 16.7 cm/s vs. 119.7 ± 13.6 cm/s vs. 111.2 ± 22.6 cm/s [P = 0.097]). Scan‐rescan reproducibility and intra‐ and interobserver variability were good to excellent (ICC ≥ 0.8) with best agreement for forward flow (ICC ≥ 0.98). Data Conclusion: The clinical protocol used at three different sites led to differences in hemodynamic parameters assessed by 4D flow. Level of Evidence: 2 Technical Efficacy Stage: 2 [ABSTRACT FROM AUTHOR]

Background: Mapping of T1 and T2 relaxation times in cardiac MRI is an invaluable tool for the diagnosis and risk stratification of a wide spectrum of cardiac diseases. Purpose: To investigate the global and regional reproducibility of native T1 and T2 mapping and to analyze the influence of demographic factors, physiological parameters, slice position, and myocardial regions on reproducibility. Study Type: Prospective single‐center cohort‐study. Population: Fifty healthy volunteers (29 female, 21 male) with a mean age of 39.4 ± 13.7 years. Field strength/Sequence: Each volunteer was investigated twice at 1.5 T using a modified look‐locker inversion‐recovery (MOLLI) sequence (T1 mapping) and a T2‐prepared steady‐state free precession (SSFP) sequence (T2 mapping). Assessment: Global T1 and T2 values were quantified for the entire left ventricle in three short‐axis slices. Regional T1 and T2 values were measured for each myocardial segment and for myocardial segments grouped by slice position and anatomical region. Statistical Tests: Test–retest reproducibility was assessed using intraclass correlation coefficient (ICC) and Bland–Altman statistics. A P value < 0.05 was considered statistically significant. Results: Reproducibility was good for global T1 values (ICC 0.88) and excellent for global T2 values (ICC 0.91). Reproducibility of T1 values was excellent (ICC 0.91) for midventricular slice and good for apical (ICC 0.86) and basal slice (ICC 0.81). Reproducibility of T1 mapping values was highest in the septum (ICC 0.90) compared to the anterior (0.81), lateral (0.86), and inferior (0.86) wall. For T2 mapping, reproducibility was good for all slice positions (ICC 0.86 for midventricular, 0.83 for basal, and 0.80 for apical slice). Reproducibility of T2 mapping was significantly lower for the inferior wall (ICC 0.58) than for septum (0.89), anterior (0.85), and lateral (0.87) wall. Data Conclusion: Native T1 and T2 mapping has good to excellent reproducibility with significant regional differences. Evidence Level: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: T1 mapping can potentially quantitatively assess the intrinsic properties of tumors. B1 correction can reduce the magnetic field inhomogeneity. Purpose: To assess the repeatability and reproducibility of B1‐corrected T1 mapping for lung cancer and the ability to identify pathological types. Study Type: Prospective reproducibility study. Population: Sixty lung cancer patients (22 with emphysema) with a total of 60 lesions (adenocarcinoma [n = 23], squamous cell carcinoma [n = 19], and small‐cell lung cancer [SCLC] [n = 18]). Field Strength/Sequence: A 3 T/B1‐corrected 3D variable flip angle T1 mapping and free‐breathing diffusion‐weighted imaging. Assessment: Intraobserver, interobserver, and test–retest reproducibility of minimum, maximum, mean, and SD of lung tumor T1 values were assessed. The correlation between mean T1 and apparent diffusion coefficient (ADC) and differences between different histological types of lung cancer were evaluated. Statistical Tests: Intraclass correlation coefficients (ICCs), within‐subject coefficients of variation (WCVs), Bland–Altman plots, Pearson's correlation coefficient (r), and analysis of variance (ANOVA). A P value <0.05 was considered to be statistically significant. Results: No significant differences were found in minimum, maximum, mean, and SD T1 values for repeated measurements (intraobserver and interobserver) and repeated examinations (P = 0.103–0.979). All parameters showed good intraobserver, interobserver and test–retest reproducibility (ICC, 0.780–0.978), except the maximum T1 value (ICC, 0.645–0.922). The mean T1 exhibited the best reproducibility and repeatability, with an average difference <6% for repeated measurements, <8% for repeated scans in lung cancer patients, and<10% for repeated scans in those with emphysema. The mean T1 correlated moderately with ADC (r = −0.580, −0.516, and −0.511 for observers A, B, and C). Both mean T1 and mean ADC were significantly different in SCLC patients compared with those in adenocarcinoma and squamous cell carcinoma patients. Data Conclusion: The mean T1 from B1‐corrected T1 mapping is a repeatable parameter with the potential to identify histological types of lung cancer and thus may be a promising imaging biomarker for characterizing lung cancer. Evidence Level: 1 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

Background: Radiomic descriptors from magnetic resonance imaging (MRI) are promising for disease diagnosis and characterization but may be sensitive to differences in imaging parameters. Objective: To evaluate the repeatability and robustness of radiomic descriptors within healthy brain tissue regions on prospectively acquired MRI scans; in a test–retest setting, under controlled systematic variations of MRI acquisition parameters, and after postprocessing. Study Type: Prospective. Subjects: Fifteen healthy participants. Field Strength/Sequence: A 3.0 T, axial T2‐weighted 2D turbo spin‐echo pulse sequence, 181 scans acquired (2 test/retest reference scans and 12 with systematic variations in contrast weighting, resolution, and acceleration per participant; removing scans with artifacts). Assessment: One hundred and forty‐six radiomic descriptors were extracted from a contiguous 2D region of white matter in each scan, before and after postprocessing. Statistical Tests: Repeatability was assessed in a test/retest setting and between manual and automated annotations for the reference scan. Robustness was evaluated between the reference scan and each group of variant scans (contrast weighting, resolution, and acceleration). Both repeatability and robustness were quantified as the proportion of radiomic descriptors that fell into distinct ranges of the concordance correlation coefficient (CCC): excellent (CCC > 0.85), good (0.7 ≤ CCC ≤ 0.85), moderate (0.5 ≤ CCC < 0.7), and poor (CCC < 0.5); for unprocessed and postprocessed scans separately. Results: Good to excellent repeatability was observed for 52% of radiomic descriptors between test/retest scans and 48% of descriptors between automated vs. manual annotations, respectively. Contrast weighting (TR/TE) changes were associated with the largest proportion of highly robust radiomic descriptors (21%, after processing). Image resolution changes resulted in the largest proportion of poorly robust radiomic descriptors (97%, before postprocessing). Postprocessing of images with only resolution/acceleration differences resulted in 73% of radiomic descriptors showing poor robustness. Data Conclusions: Many radiomic descriptors appear to be nonrobust across variations in MR contrast weighting, resolution, and acceleration, as well in test–retest settings, depending on feature formulation and postprocessing. Evidence Level: 2 Technical Efficacy: Stage 2 [ABSTRACT FROM AUTHOR]

PurposeTo examine the reproducibility of quantitative magnetic resonance (MR) methods to estimate hepatic proton density fat-fraction (PDFF) at different magnetic field strengths.Materials and methodsThis Health Insurance Portability and Accountability Act (HIPAA)-compliant study was approved by the Institutional Review Board. Following informed consent, 25 severely obese subjects (mean body mass index [BMI]: 45 ± 4, range: 38-53 kg/m(2) ) were scanned at 1.5T and 3T on the same day. Two confounder-corrected multiecho chemical shift-encoded gradient-echo-based imaging methods were acquired to estimate PDFF over the entire liver: 3D complex-based (MRI-C) and 2D magnitude-based (MRI-M) MRI. Single-voxel MR spectroscopy (MRS) was performed in the right liver lobe. Using linear regression, pairwise comparisons of estimated PDFF were made between methods (MRI-C, MRI-M, MRS) at each field strength and for each method across field strengths.Results1.5T vs. 3T regression analyses for MRI-C, MRI-M, and MRS PDFF measurements yielded R(2) values of 0.99, 0.97, and 0.90, respectively. The best-fit line was near unity (slope(m) = 1, intercept(b) = 0), indicating excellent agreement for each case: MRI-C (m = 0.92 [0.87, 0.99], b = 1.4 [0.7, 1.8]); MRI-M (m = 1.0 [0.90, 1.08], b = -1.4 [-2.4, -0.5]); MRS (m = 0.98 [0.82, 1.15], b = 1.2 [-0.2, 3.0]). Comparing MRI-C and MRI-M yielded an R(2)  = 0.98 (m = 1.1 [1.02, 1.16], b = -1.8 [-2.8, -1.1]) at 1.5T, and R(2)  = 0.99 (m = 0.98 [0.93, 1.03], b = 1.2 [0.7, 1.7]) at 3T.ConclusionThis study demonstrates that PDFF estimation is reproducible across field strengths and across two confounder-corrected MR-based methods.

BackgroundTo assess the test-retest reproducibility of cortical mapping of T2 * relaxation rates at 7 Tesla (T) MRI. T2 * maps have been used for studying cortical myelo-architecture patterns in vivo and for characterizing conditions associated with changes in iron and/or myelin concentration.MethodsT2 * maps were calculated from 7T multi-echo T2 *-weighted images acquired during separate scanning sessions on 8 healthy subjects. The reproducibility of surface-based cortical T2 * mapping was assessed at different depths of the cortex; from pial surface (0% depth) towards gray/white matter boundary (100% depth), across cortical regions and hemispheres, using coefficients of variation (COVs = SD/mean) between each couple (scan-rescan) of average T2 * measurements.ResultsAverage cortical T2 * was significantly different among 25%, 50%, and 75% depths (analysis of variance, P < 0.001). Coefficient of variations were very low within cortical regions, and whole cortex (average COV = 0.83-1.79%), indicating a high degree of reproducibility in T2 * measures.ConclusionSurface-based mapping of T2 * relaxation rates as a function of cortical depth is reproducible and could prove useful for studying the laminar architecture of the cerebral cortex in vivo, and for investigating physiological and pathological states associated with changes in iron and/or myelin concentration.

Background: Longitudinal magnetic resonance imaging (MRI) studies have become increasingly important to assess the changes in brain morphology during normal aging and neurodegenerative disorders. However, the reliability of longitudinal morphometric changes has not been fully evaluated. Purpose: To examine the reliability of longitudinal (2‐year) changes in brain morphology determined by longitudinal voxel‐based morphometry (VBM) in healthy elderly subjects, patients with mild cognitive impairment (MCI), and patients with Alzheimer's disease (AD). Study Type: Retrospective analysis. Subjects: Twenty‐four healthy elderly subjects, 28 MCI patients, and 16 AD patients. Field Strength/Sequence: A 1.5 T, magnetization‐prepared rapid gradient‐echo. Assessment: Longitudinal (2‐year) changes in gray matter volume determined by longitudinal VBM processing, and visual assessment of image quality. Statistical Tests: Intraclass correlation coefficient (ICC) and Kruskal–Wallis test. Results: The ICC maps differed among the three groups. The mean ICC was 0.81 overall (0.86 for healthy elderly subjects, 0.75 for MCI patients, and 0.76 for AD patients). The reliability was good to excellent (ICC, 0.60–1.00) for 92% of voxels (99% for healthy elderly subjects, 83% for MCI patients, and 83% for AD patients). The image quality differed significantly among the three groups (P < 0.05). Data Conclusion: These results indicate that the reliability of longitudinal gray matter volume changes by VBM is good to excellent for most voxels. However, reliability may be affected by the disease, possibly due to differences in head motion during imaging. Evidence Level : 3 Technical Efficacy : Stage 1 [ABSTRACT FROM AUTHOR]

PurposeTo determine reproducibility of the femoral condyle cartilage volume (CV) in cross-sectional and longitudinal studies using various 3D imaging techniques at 1.5 T and 3 T.Materials and methodsIn 21 subjects with osteoarthritis, magnetic resonance imaging (MRI) including four different sequences (sagittal 3D fat suppressed spoiled gradient-echo [SPGR] at 1.5 T, fat suppressed fast low angle shot [FLASH] at 3 T, water-excitation dual echo steady state [DESS] at 3 T, and water-excitation multiecho data image combination [MEDIC] at 3 T) were acquired at baseline and ∼1 year later. The CV measured using semiautomated segmentation software by three readers was analyzed.ResultsThe mean of the interclass correlation coefficient between each reader from SPGR, FLASH, DESS, and MEDIC was 0.899, 0.948, 0.943, and 0.954, respectively. The mean CV (×10(4) mm(3) ) measured by each reader from SPGR/FLASH/DESS/MEDIC sequences was the following in this order: 1.34/1.52/1.50/1.35, 1.21/1.43/1.40/1.27, 1.22/1.37/1.36/1.22, and 1.17/1.36/1.35/1.21 by readers 1, 2, 3 (first analysis), and 3 (second analysis), respectively. There was no statistically significant difference in CV between any readers in any sequences. The CV measured on FLASH and DESS tended to be greater than that on SPGR or MEDIC.ConclusionInter- and intraobserver reproducibility of cartilage segmentation using semiautomated software was validated. Although there was no statistical significance, there was a tendency of under- or overestimating CV by each sequence.

Background: Diffusion kurtosis imaging (DKI) quantifies the non‐Gaussian diffusion of water within tissue microstructure. However, it has increased fitting parameters and requires higher b‐values. Evaluation of DKI reproducibility is important for clinical purposes. Purpose: To assess the reproducibility in whole‐brain high‐resolution DKI at varying b‐values. Study Type: Retrospective. Subjects and Phantoms: In all, 44 individuals from the test–retest Human Connectome Project (HCP) database and 12 3D‐printed phantoms. Field Strength/Sequence: Diffusion‐weighted multiband echo‐planar imaging sequence at 3T and 9.4T. magnetization‐prepared rapid acquisition gradient echo at 3T for in vivo structural data only. Assessment: From HCP data with b‐values = 1000, 2000, 3000 s/mm2 (dataset A), two additional datasets with b‐values = 1000, 3000 s/mm2 (dataset B) and b‐values = 1000, 2000 s/mm2 (dataset C) were extracted. Estimated DKI metrics from each dataset were used for evaluating reproducibility and fitting quality in white matter (WM) and gray matter (GM) based on whole‐brain and regions of interest (ROIs). Statistical Tests: DKI reproducibility was assessed using the within‐subject coefficient of variation (CoV), fitting residuals to evaluate DKI fitting accuracy and Pearson's correlation to investigate the presence of systematic biases. Repeated measures analysis of variance was used for statistical comparison. Results: Datasets A and B exhibited lower DKI CoVs (<20%) compared to C (<50%) in both WM and GM ROIs (all P < 0.05). This effect varies between DKI and DTI parameters (P < 0.005). Whole‐brain fitting residuals were consistent across datasets (P > 0.05), but lower residuals in dataset B were detected for the WM ROIs (P < 0.001). A similar trend was observed for the phantom data CoVs (<7.5%) at varying fiber orientations for datasets A and B. Finally, dataset C was characterized by higher residuals across the different fiber crossings (P < 0.05). Data Conclusion: The study demonstrates that high reproducibility can still be achieved within a reasonable scan time, specifically dataset B, supporting the potential of DKI for aiding clinical tools in detecting microstructural changes. [ABSTRACT FROM AUTHOR]

Background: Hemodynamic aorta parameters can be derived from 4D flow MRI, but this requires lumen segmentation. In both commercially available and research 4D flow MRI software tools, lumen segmentation is mostly (semi‐)automatically performed and subsequently manually improved by an observer. Since the segmentation variability, together with 4D flow MRI data and image processing algorithms, will contribute to the reproducibility of patient‐specific flow properties, the observer's lumen segmentation reproducibility and repeatability needs to be assessed. Purpose: To determine the interexamination, interobserver reproducibility, and intraobserver repeatability of aortic lumen segmentation on 4D flow MRI. Study Type: Prospective and retrospective. Population: A healthy volunteer cohort of 10 subjects who underwent 4D flow MRI twice. Also, a clinical cohort of six subjects who underwent 4D flow MRI once. Field Strength/Sequence: 3T; time‐resolved three‐directional and 3D velocity‐encoded sequence (4D flow MRI). Assessment: The thoracic aorta was segmented on the 4D flow MRI in five systolic phases. By positioning six planes perpendicular to a segmentation's centerline, the aorta was divided into five segments. The volume, surface area, centerline length, maximal diameter, and curvature radius were determined for each segment. Statistical Tests: To assess the reproducibility, the coefficient of variation (COV), Pearson correlation coefficient (r), and intraclass correlation coefficient (ICC) were calculated. Results: The interexamination and interobserver reproducibility and intraobserver repeatability were comparable for each parameter. For both cohorts there was very good reproducibility and repeatability for volume, surface area, and centerline length (COV = 10–32%, r = 0.54–0.95 and ICC = 0.65–0.99), excellent reproducibility and repeatability for maximal diameter (COV = 3–11%, r = 0.94–0.99, ICC = 0.94–0.99), and good reproducibility and repeatability for curvature radius (COV = 25–62%, r = 0.73–0.95, ICC = 0.84–0.97). Data Conclusion: This study demonstrated no major reproducibility and repeatability limitations for 4D flow MRI aortic lumen segmentation. Level of Evidence: 3 Technical Efficacy Stage: 2 [ABSTRACT FROM AUTHOR]

Background: Renal multiparametric magnetic resonance imaging (MRI) is a promising tool for diagnosis, prognosis, and treatment monitoring in kidney disease.Purpose: To determine intrasubject test-retest repeatability of renal MRI measurements.Study Type: Prospective.Population: Nineteen healthy subjects aged over 40 years.Field Strength/sequences: T1 and T2 mapping, R2 * mapping or blood oxygenation level-dependent (BOLD) MRI, diffusion tensor imaging (DTI), and intravoxel incoherent motion (IVIM) diffusion-weighted imaging (DWI), 2D phase contrast, arterial spin labelling (ASL), dynamic contrast enhanced (DCE) MRI, and quantitative Dixon for fat quantification at 3T.Assessment: Subjects were scanned twice with ~1 week between visits. Total scan time was ~1 hour. Postprocessing included motion correction, semiautomated segmentation of cortex and medulla, and fitting of the appropriate signal model.Statistical Test: To assess the repeatability, a Bland-Altman analysis was performed and coefficients of variation (CoVs), repeatability coefficients, and intraclass correlation coefficients were calculated.Results: CoVs for relaxometry (T1 , T2 , R2 */BOLD) were below 6.1%, with the lowest CoVs for T2 maps and highest for R2 */BOLD. CoVs for all diffusion analyses were below 7.2%, except for perfusion fraction (FP ), with CoVs ranging from 18-24%. The CoV for renal sinus fat volume and percentage were both around 9%. Perfusion measurements were most repeatable with ASL (cortical perfusion only) and 2D phase contrast with CoVs of 10% and 13%, respectively. DCE perfusion had a CoV of 16%, while single kidney glomerular filtration rate (GFR) had a CoV of 13%. Repeatability coefficients (RCs) ranged from 7.7-87% (lowest/highest values for medullary mean diffusivity and cortical FP , respectively) and intraclass correlation coefficients (ICCs) ranged from -0.01 to 0.98 (lowest/highest values for cortical FP and renal sinus fat volume, respectively).Data Conclusion: CoVs of most MRI measures of renal function and structure (with the exception of FP and perfusion as measured by DCE) were below 13%, which is comparable to standard clinical tests in nephrology.Level Of Evidence: 2 TECHNICAL EFFICACY: Stage 1. [ABSTRACT FROM AUTHOR]

Background: Radiomics in neuroimaging has gained momentum as a noninvasive prediction tool not only to differentiate between types of brain tumors, but also to create phenotypic signatures in neurological and neuropsychiatric disorders. However, there is currently little understating about the robustness and reproducibility of radiomic features in a baseline normative population. Purpose To investigate the intra‐ and interscanner reproducibility, spatial robustness, and sensitivity of radiomics on fluid attenuation inversion recovery (FLAIR) images, which are widely used in neuro‐oncology investigations. Study Type: Retrospective. Population Three separate datasets of healthy controls: 1) 87 subjects (age range 12–64 years), 2) intrascanner three timepoints, four subjects, and 3) interscanner, eight subjects at three different sites. Field Strength/Sequence: T2‐weighted FLAIR at 1.5T and 3.0T. Assessment Spatial variance across lobes, and their relation with age/gender, intra‐ and inter‐scanner reproducibility (with and without site harmonization) of radiomics. Statistical Tests: Analysis of variance (ANOVA), interclass correlation (ICC), coefficient of variation (CoV), Bland–Altman analysis. Results: Analysis of data revealed no differences between genders; however, multiple radiomic features were highly associated with age (P < 0.05). Spatial variability was also evaluated where only 29.04% gray matter and 38.7% white matter features demonstrated an ICC >0.5. Furthermore, the results demonstrated intra‐scanner reliability (ICC >0.5); however, inter‐scanner reproducibility was poor, with ICC < 0.5 for 82% gray matter and 78.5% white matter features. The inter‐scanner reliability improved (ICC < 0.5 for 39.67% gray matter and 38% white matter features) using site‐harmonization techniques. Data Conclusion: These findings suggest that, accounting for age, spatial locations in radiomics‐based analysis and use of intersite radiomics harmonization is crucial before interpreting these features for pathological inference. Level of Evidence 3. Technical Efficacy Stage 1. J. MAGN. RESON. IMAGING 2021;53:394–407. [ABSTRACT FROM AUTHOR]

Background: The diagnosis of sonographically indeterminate adnexal masses (AM) signifies a major challenge in clinical practice. Early detection and characterization have increased the need for accurate imaging evaluation before treatment.Purpose: To assess the validity and reproducibility of the ADNEX MR Scoring system in the diagnosis of sonographically indeterminate AM.Study Type: A prospective multicenter study.Population: In all, 531 women (mean age, 44 ± 11.2 years; range, 21-79 years) with 572 sonographically indeterminate AM.Field Strength/sequence: 1.5T/precontrast T1 -weighted imaging (WI) fast spin echo (FSE) (in-phase and out-of-phase, with and without fat suppression); T2 -WI FSE; diffusion-WI single-shot echo planner with b-values of 0 and 1000 s/mm2 ; and dynamic contrast-enhanced perfusion T1 -WI liver acquisition with volume acceleration (LAVA).Assessment: All MRI examinations were evaluated by three radiologists, and the AM were categorized into five scores based on the ADNEX MR Scoring system. Score 1: no AM; 2: benign AM; 3: probably benign AM; 4: indeterminate AM; 5: probably malignant AM. Histopathology and imaging follow-up were used as the standard references for evaluating the validity of the ADNEX MR Scoring system for detecting ovarian malignancy.Statistical Tests: Four-fold table test, kappa statistics (κ), and receiver operating characteristic (ROC) curve.Results: In all, 136 (23.8%) AM were malignant, and 436 (76.2%) were benign. Of the 350 AM classified as score 2, one (0.3%) was malignant; of the 62 AM classified as score 3, six (9.7%) were malignant; of the 73 AM classified as score 4, 43 (58.9%) were malignant; and of the 87 AM categorized as score 5, 86 (98.9%) were malignant. The best cutoff value for predicting malignant AM was score >3 with sensitivity and specificity of 92.9% and 94.9%, respectively. The interreader agreement of the ADNEX MR Scoring was very good (κ = 0.861).Data Conclusion: The current study supports the high validity and reproducibility of the ADNEX MR Scoring system for the diagnosis of sonographically indeterminate AM.Level Of Evidence: 1 TECHNICAL EFFICACY STAGE: 2. [ABSTRACT FROM AUTHOR]

Background: Magnetic resonance cholangiopancreatography (MRCP) is an important tool for noninvasive imaging of biliary disease, however, its assessment is currently subjective, resulting in the need for objective biomarkers.Purpose: To investigate the accuracy, scan/rescan repeatability, and cross-scanner reproducibility of a novel quantitative MRCP tool on phantoms and in vivo. Additionally, to report normative ranges derived from the healthy cohort for duct measurements and tree-level summary metrics.Study Type: Prospective.Phantoms/subjects: Phantoms: two bespoke designs, one with varying tube-width, curvature, and orientation, and one exhibiting a complex structure based on a real biliary tree. Subjects Twenty healthy volunteers, 10 patients with biliary disease, and 10 with nonbiliary liver disease.Sequence/field Strength: MRCP data were acquired using heavily T2 -weighted 3D multishot fast/turbo spin echo acquisitions at 1.5T and 3T.Assessment: Digital instances of the phantoms were synthesized with varying resolution and signal-to-noise ratio. Physical 3D-printed phantoms were scanned across six scanners (two field strengths for each of three manufacturers). Human subjects were imaged on four scanners (two fieldstrengths for each of two manufacturers).Statistical Tests: Bland-Altman analysis and repeatability coefficient (RC).Results: Accuracy of the diameter measurement approximated the scanning resolution, with 95% limits of agreement (LoA) from -1.1 to 1.0 mm. Excellent phantom repeatability was observed, with LoA from -0.4 to 0.4 mm. Good reproducibility was observed across the six scanners for both phantoms, with a range of LoA from -1.1 to 0.5 mm. Inter- and intraobserver agreement was high. Quantitative MRCP detected strictures and dilatations in the phantom with 76.6% and 85.9% sensitivity and 100% specificity in both. Patients and healthy volunteers exhibited significant differences in metrics including common bile duct (CBD) maximum diameter (7.6 mm vs. 5.2 mm P = 0.002), and overall biliary tree volume 12.36 mL vs. 4.61 mL, P = 0.0026).Data Conclusion: The results indicate that quantitative MRCP provides accurate, repeatable, and reproducible measurements capable of objectively assessing cholangiopathic change. Evidence Level: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;52:807-820. [ABSTRACT FROM AUTHOR]

Background: Fractional anisotropy (FA) and mean diffusivity (MD) are frequently used to evaluate longitudinal changes in white matter (WM) microstructure. Recently, there has been a growing interest in identifying experience-dependent plasticity in gray matter using MD. Improving registration has thus become a major goal to enhance the detection of subtle longitudinal changes in cortical microstructure.Purpose: To optimize normalization of diffusion tensor images (DTI) to improve registration in gray matter and reduce variability associated with multisession registrations.Study Type: Prospective longitudinal study.Subjects: Twenty-one healthy subjects (18-31 years old) underwent nine MRI scanning sessions each.Field Strength/sequence: 3.0T, diffusion-weighted multiband-accelerated sequence, MP2RAGE sequence.Assessment: Diffusion-weighted images were registered to standard space using different pipelines that varied in the features used for normalization, namely, the nonlinear registration algorithm (FSL vs. ANTs), the registration target (FA-based vs. T1 -based templates), and the use of intermediate individual (FA-based or T1 -based) targets. We compared the across-session test-retest reproducibility error of these normalization approaches for FA and MD in white and gray matter.Statistical Tests: Reproducibility errors were compared using a repeated-measures analysis of variance with pipeline as the within-subject factor.Results: The registration of FA data to the FMRIB58 FA atlas using ANTs yielded lower reproducibility errors in white matter (P < 0.0001) with respect to FSL. Moreover, using the MNI152 T1 template as the target of registration resulted in lower reproducibility errors for MD (P < 0.0001), whereas the FMRIB58 FA template performed better for FA (P < 0.0001). Finally, the use of an intermediate individual template improved reproducibility when registration of the FA images to the MNI152 T1 was carried out within modality (FA-FA) (P < 0.05), but not via a T1 -based individual template.Data Conclusion: A normalization approach using ANTs to register FA images to the MNI152 T1 template via an individual FA template minimized test-retest reproducibility errors both for gray and white matter.Level Of Evidence: 1 TECHNICAL EFFICACY STAGE: 1 J. Magn. Reson. Imaging 2020;52:766-775. [ABSTRACT FROM AUTHOR]

Background: Single-point macromolecular proton fraction (MPF) mapping is a recent quantitative MRI method for fast assessment of brain myelination. Information about reproducibility and sensitivity of MPF mapping to magnetic field nonuniformity is important for clinical applications.Purpose: To assess scan-rescan repeatability and a value of B0 and B1 field inhomogeneity corrections in single-point synthetic-reference MPF mapping.Study Type: Prospective.Population: Eight healthy adult volunteers underwent two scans with 11.5 ± 2.3 months interval.Field Strength/sequence: 3T; whole-brain 3D MPF mapping protocol included three spoiled gradient-echo sequences providing T1 , proton density, and magnetization transfer contrasts with 1.25 × 1.25 × 1.25 mm3 resolution and B0 and B1 mapping sequences.Assessment: MPF maps were reconstructed with B0 and B1 field nonuniformity correction, B0 - and B1 -only corrections, and without corrections. Mean MPF values were measured in automatically segmented white matter (WM) and gray matter (GM).Statistical Tests: Within-subject coefficient of variation (CV), intraclass correlation coefficient (ICC), Bland-Altman plots, and paired t-tests to assess scan-rescan repeatability. Repeated-measures analysis of variance (ANOVA) to compare field corrections.Results: Maximal relative local MPF errors without correction in the areas of largest field nonuniformities were about 5% and 27% for B0 and B1 , respectively. The effect of B0 correction was insignificant for whole-brain WM (P > 0.25) and GM (P > 0.98) MPF. The absence of B1 correction caused a positive relative bias of 4-5% (P < 0.001) in both tissues. Scan-rescan agreement was similar for all field correction options with ICCs 0.80-0.81 for WM and 0.89-0.92 for GM. CVs were 1.6-1.7% for WM and 0.7-1.0% for GM.Data Conclusion: The single-point method enables high repeatability of MPF maps obtained with the same equipment. Correction of B0 inhomogeneity may be disregarded to shorten the examination time. B1 nonuniformity correction improves accuracy of MPF measurements at 3T. Reliability of whole-brain MPF measurements in WM and GM is not affected by B0 and B1 field corrections.Level Of Evidence: 2 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2020;51:1789-1798. [ABSTRACT FROM AUTHOR]

Background: Arterial spin labeling (ASL) can be confounded by varying arterial transit times (ATT) across the brain and with disease. Hadamard encoding schemes can be applied to 3D pseudocontinuous ASL (pCASL) to acquire ASL data with multiple postlabeling delays (PLDs) to estimate ATT and then correct cerebral blood flow (CBF).Purpose: To assess the longitudinal reproducibility of 3D pCASL with Hadamard-encoded multiple PLDs.Study Type: Prospective, longitudinal.Population: Fifty-two healthy, right-handed male subjects who underwent imaging at four timepoints over 45 days.Field Strength/sequence: A Hadamard-encoded 3D pCASL sequence was acquired at 3.0T with seven PLDs from 1.0-3.7 sec.Assessment: ATT and corrected CBF (cCBF) were computed. Conventional uncorrected CBF (unCBF) was also estimated. Within- and between-subject coefficient of variation (wCV and bCV, respectively) and intraclass correlation coefficient (ICC) were evaluated across four time intervals: 7, 14, 30, and 45 days, in gray matter and 17 independent regions of interest (ROIs). A power analysis was also conducted.Statistical Tests: A repeated-measures analysis of variance (ANOVA) was used to compare ATT, cCBF, and unCBF across the four scan sessions. A paired two-sample t-test was used to compare cCBF and unCBF. Pearson's correlation was used to examine the relationship between the cCBF and unCBF difference and ATT. Power calculations were completed using both the cCBF and unCBF variances.Results: ATT showed the lowest wCV and bCV (3.3-4.4% and 6.0-6.3%, respectively) compared to both cCBF (10.5-11.7% and 20.6-22.2%, respectively) and unCBF (12.0-13.6% and 22.7-23.7%, respectively). wCV and bCV were lower for cCBF vs. unCBF. A significant difference between cCBF and unCBF was found in most regions (P = 5.5 × 10-5 -3.8 × 10-4 in gray matter) that was highly correlated with ATT (R2 = 0.79-0.86). A power analysis yielded acceptable power at feasible sample sizes using cCBF.Data Conclusion: ATT and ATT-corrected CBF were longitudinally stable, indicating that ATT and CBF changes can be reliably evaluated with Hadamard-encoded 3D pCASL with multiple PLDs.Level Of Evidence: 1 Technical Efficacy Stage: 2 J. Magn. Reson. Imaging 2020;51:1846-1853. [ABSTRACT FROM AUTHOR]

Magnetic resonance fingerprinting (MRF) is a powerful quantitative MRI technique capable of acquiring multiple property maps simultaneously in a short timeframe. The MRF framework has been adapted to a wide variety of clinical applications, but faces challenges in technical development, and to date has only demonstrated repeatability and reproducibility in small studies. In this review, we discuss the current implementations of MRF and their use in a clinical setting. Based on this analysis, we highlight areas of need that must be addressed before MRF can be fully adopted into the clinic and make recommendations to the MRF community on standardization and validation strategies of MRF techniques. Level of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:675-692. [ABSTRACT FROM AUTHOR]

Background: Whole-organ, noninvasive techniques for the detection and quantification of nonalcoholic fatty liver disease features have clinical and research applications. However, the effect of time of day, hydration status, and meals are unknown factors with potential to impact bias, precision, reproducibility, and repeatability of chemical shift-encoded MRI (CSE-MRI) to quantify liver proton density fat fraction (PDFF).Purpose: To assess the effect of diurnal variation on PDFF using CSE-MRI, including the effect of time of day, the effect of meals and hydration status, as well as the day to day variability.Study Type: Prospective.Subjects: Eleven healthy subjects and nine patients with observed hepatic steatosis.Field Strength/sequences: A commercial quantitative confounder-corrected CSE-MRI sequence (IDEAL IQ) and an MR spectroscopy (MRS) sequence (multiecho STEAM) were acquired at 1.5T.Assessment: MRI-PDFF and MRS-PDFF estimates were compared across six visits (before and after a controlled breakfast, before and after an uncontrolled lunch, at approximately 4 pm, and then before breakfast on the following day) with three repeated measures for a total of 360 MRI-PDFF and MRS-PDFF measurements.Statistical Tests: Linear regression, Bland-Altman analysis, and mixed effect models were used to determine the bias, precision, and repeatability of PDFF measurements.Results: No statistically significant linear trend was observed across visits for either MRI-PDFF or MRS-PDFF (P = 0.31 and 0.37, respectively). The repeatability was measured to be 0.86% for MRI-PDFF and 1.1% for MRS-PDFF over all six visits. For MRI-PDFF, the variability between all six visits (0.94%) was only slightly higher than within each visit (0.66%), with P < 0.001. For MRS-PDFF, the variability between all six visits was 1.29%, compared with 0.87% within each visit (P < 0.001).Data Conclusion: Our results may indicate that it is not necessary to control for the time of day or the fasting/fed state of the patient when measuring PDFF using CSE-MRI.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2020;51:407-414. [ABSTRACT FROM AUTHOR]

Background: Fiber tracking with diffusion-weighted MRI has become an essential tool for estimating in vivo brain white matter architecture. Fiber tracking results are sensitive to the choice of processing method and tracking criteria.Purpose: To assess the variability for an algorithm in group studies reproducibility is of critical context. However, reproducibility does not assess the validity of the brain connections. Phantom studies provide concrete quantitative comparisons of methods relative to absolute ground truths, yet do no capture variabilities because of in vivo physiological factors. The ISMRM 2017 TraCED challenge was created to fulfill the gap.Study Type: A systematic review of algorithms and tract reproducibility studies.Subjects: Single healthy volunteers.Field Strength/sequence: 3.0T, two different scanners by the same manufacturer. The multishell acquisition included b-values of 1000, 2000, and 3000 s/mm2 with 20, 45, and 64 diffusion gradient directions per shell, respectively.Assessment: Nine international groups submitted 46 tractography algorithm entries each consisting 16 tracts per scan. The algorithms were assessed using intraclass correlation (ICC) and the Dice similarity measure.Statistical Tests: Containment analysis was performed to assess if the submitted algorithms had containment within tracts of larger volume submissions. This also serves the purpose to detect if spurious submissions had been made.Results: The top five submissions had high ICC and Dice >0.88. Reproducibility was high within the top five submissions when assessed across sessions or across scanners: 0.87-0.97. Containment analysis shows that the top five submissions are contained within larger volume submissions. From the total of 16 tracts as an outcome relatively the number of tracts with high, moderate, and low reproducibility were 8, 4, and 4.Data Conclusion: The different methods clearly result in fundamentally different tract structures at the more conservative specificity choices. Data and challenge infrastructure remain available for continued analysis and provide a platform for comparison.Level Of Evidence: 5 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2020;51:234-249. [ABSTRACT FROM AUTHOR]

Background: Sodium MRI (23 Na-MRI)-derived biomarkers such as total sodium concentration (TSC) have the potential to provide information on tumor cellularity and the changes in tumor microstructure that occur following therapy.Purpose: To evaluate the repeatability and reproducibility of TSC measurements in the brains of healthy volunteers, providing evidence for the technical validation of 23 Na-MRI-derived biomarkers.Study Type: Prospective multicenter study.Subjects: Eleven volunteers (32 ± 6 years; eight males, three females) were scanned twice at each of two sites.Field Strength/sequence: Comparable 3D-cones 23 Na-MRI ultrashort echo time acquisitions at 3T.Assessment: TSC values, quantified from calibration phantoms placed in the field of view, were obtained from white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF), based on automated segmentation of coregistered 1 H T1 -weighted images and hand-drawn regions of interest by two readers.Statistical Tests: Coefficients of variation (CoVs) from mean TSC values were used to assess intrasite repeatability and intersite reproducibility.Results: Mean GM TSC concentrations (52.1 ± 7.1 mM) were ∼20% higher than for WM (41.8 ± 6.7 mM). Measurements were highly repeatable at both sites with mean scan-rescan CoVs between volunteers and regions of 2% and 4%, respectively. Mean intersite reproducibility CoVs were 3%, 3%, and 6% for WM, GM, and CSF, respectively.Data Conclusion: These results demonstrate technical validation of sodium MRI-derived biomarkers in healthy volunteers. We also show that comparable 23 Na imaging of the brain can be implemented across different sites and scanners with excellent repeatability and reproducibility.Level Of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:1278-1284. [ABSTRACT FROM AUTHOR]

Background: The spatial coefficient of variation (sCoV) of arterial spin-labeled (ASL) MRI can index cerebral blood flow spatial heterogeneity. This metric reflects delayed blood delivery-seen as a hyperintense ASL signal juxtaposed by hypointense regions.Purpose: To investigate the use of ASL-sCoV in the classification of cognitively unimpaired (CU), mild cognitive impairment (MCI), and Alzheimer's disease (AD) cohorts.Study Type: Prospective/cohort.Population: Baseline ASL images from AD neuroimaging initiative dataset in three groups of CU, MCI, and AD (N = 258).Field Strength/sequence: Pulsed ASL (PICORE QT2) images were acquired on 3 T Siemens systems (TE/TR = 12/3400 msec, TI1/2 = 700/1900 msec).Assessment: ASL-sCoV was calculated in temporal, parietal, occipital, and frontal lobes as well as whole gray matter.Statistical Tests: The primary analysis used an analysis of covariance to investigate sCoV and cognitive group (CU, MCI, AD) associations. We also evaluated the repeatability of sCoV by calculating within-subject agreement in a subgroup of CU participants with a repeat ASL. The secondary analyses assessed ventricular volume, amyloid burden, glucose uptake, ASL-sCoV, and regional CBF as cognitive group classifiers using logistic regression models and receiver operating characteristic analyses.Results: We found that global and temporal lobe sCoV differed between cognitive groups (P = 0.006). Post-hoc tests showed that temporal lobe sCoV was lower in CU than in MCI (Cohen's d = -0.36) or AD (Cohen's d = -1.36). We found that sCoV was moderately repeatable in CU (intersession intraclass correlation = 0.50; intrasession intraclass correlation = 0.88). Subsequent logistic regression analyses revealed that temporal lobe sCoV and amyloid uptake classified CU vs. MCI (P < 0.01; accuracy = 78%). Temporal lobe sCoV, amyloid, and glucose uptake classified CU vs. AD (P < 0.01; accuracy = 97%); glucose uptake significantly classified MCI vs. AD (P < 0.01; accuracy = 85%).Data Conclusion: We showed that ASL spatial heterogeneity can be used alongside AD neuroimaging markers to distinguish cognitive groups, in particular, cognitively unimpaired from cognitively impaired individuals.Level Of Evidence: 2 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:858-867. [ABSTRACT FROM AUTHOR]

Background: The relationship between blood flow characteristics and ascending aortic (AA) dilatation has not been studied in patients with a tricuspid aortic valve (TAV) without aortic stenosis.Purpose: To evaluate whether 4D flow characteristics determined in MRI are related to AA dilatation by comparing dilated AA and nondilated AA subjects with TAV.Study Type: Prospective.Population: Twenty patients with dilated AA and 20 age-matched patients with nondilated AA.Field Strength/sequence: 1.5T/4D flow, 2D flow, and anatomic images.Assessment: Altogether, 16 different 4D flow parameters were assessed in 10 planes in the thoracic aorta. Intra- and interobserver reproducibility were analyzed.Statistical Tests: Independent t-test for normally distributed and the Mann-Whitney test for skewed distributed parameters were used. A paired-samples t-test was used to compare 2D and 4D flow parameters. Intraclass correlation coefficient (ICC) was used in intra- and interobserver reproducibility analysis.Results: Aortic flow was displaced from the centerline of the aorta in the proximal and tubular planes. Flow displacement (FD) was greatest in the proximal plane of AA and was higher in dilated AA (4.5%, range 3.0-5.8%) than in nondilated AA (2.0%, 1.0-3.0%, P < 0.001). Total wall shear stress (WSS) values were 1.3 ± 0.4 times higher on the displaced side than on the opposite side of the aorta (P < 0.01). The circumferential WSS (WSSC ) ratio to total WSS was greater in dilated AA, being 0.48 ± 0.11 vs. 0.32 ± 0.09 in the inner curvature of the proximal AA (P < 0.001) and 0.37 ± 0.11 vs. 0.26 ± 0.07 in the whole aortic ring in the distal AA (P < 0.001). Depending on 4D flow parameters, reproducibility varied from excellent (ICC = 0.923) to very low (ICC = 0.204).Data Conclusion: The present study demonstrates that 4D flow measurements help to visualize the pathological flow patterns related to aortic dilatation. Flow displacement and an increased WSSc/WSS ratio are significantly associated with AA dilatation.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;50:136-145. [ABSTRACT FROM AUTHOR]

Background: Assessing the multicenter variability of magnetization transfer ratio (MTR) measurements in the spinal cord of healthy controls is the first step toward investigating its clinical use as a biomarker.Purpose: To analyze the between-session, between-participant, and between-scanner variability of MTR measurements in automatically extracted regions of interest in the cervical cord of healthy controls.Study Type: Control study.Population: Forty-four participants, distributed across five MRI scanners (all from the same manufacturer). Ten participants were scanned twice in the same scanner, and 10 others were scanned twice in two different scanners.Field Strength/sequence: 3D-gradient echo images, centered on C5, without and with magnetization transfer prepulse at 3T.Assessment: We calculated the mean MTR for different vertebral levels in the whole cord (WC), as well as in the white matter and gray matter, and determined the between-session, between-participant, and between-scanner variabilities.Statistical Tests: Coefficients of variation and intraclass correlations (ICCs) for the different variabilities and their associated confidence intervals.Results: The MTR measurements for Levels C4-C6 (near the slab center) exhibited a mean value in WC of 34.6 pu and a pooled standard deviation of 0.9 pu. The between-session coefficient of variation was estimated as 2.3% (ICC = 0.63), the between-participant coefficient as 1.6% (ICC = 0.32), and the between-scanner coefficient as 0.7% (ICC = 0.05). The resulting aggregate coefficient of variation was 2.9%, which was sufficiently low to detect an MTR reduction of 1 pu between groups of about 45 participants (Type-I error rate: 0.05; Type-II error rate: 0.10).Data Conclusion: The good between-scanner reproducibility and low overall variability in cervical spinal cord MTR measurements in a control population might pave the way for multicenter analyses in various neurological diseases with moderate cohort sizes.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:1777-1785. [ABSTRACT FROM AUTHOR]

Background: Cerebral glutathione (GSH), a marker of oxidative stress, has been quantified in neurodegenerative diseases and psychiatric disorders using proton magnetic resonance spectroscopy (MRS). Using a reproducible MRS technique is important, as it minimizes the impact of measurement technique variability on the study results and ensures that other studies can replicate the results.Hypothesis: We hypothesized that very short echo time (TE) acquisitions would have comparable reproducibility to a long TE MEGA-PRESS acquisition, and that the short TE PRESS acquisition would have the poorest reproducibility.Study Type: Prospective.Subjects/phantoms: Ten healthy adults were scanned during two visits, and six metabolite phantoms containing varying concentrations of GSH and metabolites with resonances that overlap with GSH were scanned once.Field Strength/sequence: At 3T we acquired MRS data using four different sequences: PRESS, SPECIAL, PR-STEAM, and MEGA-PRESS.Assessment: Reproducibility of each MRS sequence across two visits was assessed.Statistical Tests: Mean coefficients of variation (CV) and mean absolute difference (AD) were used to assess reproducibility. Linear regressions were performed on data collected from phantoms to examine the agreement between known and quantified levels of GSH.Results: Of the four techniques, PR-STEAM had the lowest mean CV and AD (5.4% and 7.5%, respectively), implying excellent reproducibility, followed closely by PRESS (5.8% and 8.2%) and SPECIAL (8.0 and 10.1%), and finally by MEGA-PRESS (13.5% and 17.1%). Phantom data revealed excellent fits (R2 ≥ 0.98 or higher) using all methods.Data Conclusion: Our data suggest that GSH can be quantified reproducibly without the use of spectral editing.Level Of Evidence: 2 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2019;49:176-183. [ABSTRACT FROM AUTHOR]

Background: Quantitative susceptibility mapping (QSM) is an MRI postprocessing technique that allows quantification of the spatial distribution of tissue magnetic susceptibility in vivo. Contributing sources include iron, blood products, calcium, myelin, and lipid content.Purpose: To evaluate the reproducibility and consistency of QSM across clinical field strengths of 1.5T and 3T and to optimize the contrast-to-noise ratio (CNR) at 1.5T through bandwidth tuning.Study Type: Prospective.Subjects: Sixteen healthy volunteers (10 men, 6 women; age range 24-37; mean age 27.8 ± 3.2 years).Field Strengths/sequences: 1.5T and 3T systems from the same vendor. Four spoiled gradient echo (SPGR) sequences were designed with different acquisition bandwidths.Assessment: QSM reconstruction was achieved through a nonlinear morphology-enabled dipole inversion (MEDI) algorithm employing L1 regularization. CNR was calculated in seven regions of interest (ROIs), while reproducibility and consistency of QSM measurements were evaluated through voxel-based and region-specific linear correlation analyses and Bland-Altman plots.Statistical Tests: Interclass correlation, Wilcoxon rank sum test, linear regression analysis, Bland-Altman analysis, Welch's t-test.Results: CNR analysis showed a statistically significant (P < 0.05) increase in four out of seven ROIs for the lowest bandwidth employed with respect to the highest (25.18% increase in CNR of caudate nucleus). All sequences reported an excellent correlation across field strength and bandwidth variation (R ≥ 0.96, widest limits of agreement from -18.7 to 25.8 ppb) in the ROI-based analysis, while the correlation was found to be good for the voxel-based analysis of averaged maps (R ≥ 0.90, widest limits of agreement from -9.3 to 9.1 ppb).Data Conclusion: CNR of QSM images reconstructed from 1.5T acquisitions can be enhanced through bandwidth tuning. MEDI-based QSM reconstruction demonstrated to be reproducible and consistent both across field strengths (1.5T and 3T) and bandwidth variation.Level Of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1410-1420. [ABSTRACT FROM AUTHOR]

Background: Whole-brain global cerebral blood flow (CBF) determined by MRI techniques, calculated using total CBF (TCBF) from phase-contrast MRI (PC-MRI), and brain parenchyma volume (BPV) from T1 -weighted image, have become increasingly popular in many applications.Purpose/hypothesis: To determine if MRI-based measurements of whole-brain global CBF data obtained across different field strengths could be merged, TCBF and BPV data acquired at 1.5T and 3T were compared.Study Type: Prospective study.Population: Seventeen healthy subjects (eight females, aged 21-29 years old).Field Strength/sequence: Fast spoiled gradient echo (FSPGR) and PC-MRI at both 1.5T and 3T.Assessment: TCBF and BPV data acquired at 1.5T and 3T were compared.Statistical Tests: The relationships of TCBF and whole-brain global CBF between two field strengths were examined by using the Pearson correlation coefficient analysis and intraclass correlation coefficient (ICC).Results: Regression analysis revealed a strong correlation between TCBF at two field strengths (R2  = 0.78, P < 0.001), and the ICC was 0.85, suggesting measurements of TCBF at 1.5T were comparable and correlated with those at 3T. There was a significant difference in BPV between field strengths, where the white matter estimate was significantly larger at 1.5T when compared with that at 3T (P < 0.001). When TCBF was further normalized to the brain parenchyma mass to obtain whole-brain global CBF, it only showed a moderate correlation between measurements at the two field strengths (R2  = 0.46, P = 0.003) and lower ICC of 0.66, reflecting the slightly higher interstrength variability in the whole-brain global CBF measurements.Data Conclusion: TCBF measurements could be performed equally well with comparable results at both field strengths, but specific attention should be given when TCBF is further normalized to BPV to obtain whole-brain global CBF.Level Of Evidence: 1 Technical Efficacy: Stage 1 J. Magn. Reson. Imaging 2018;47:1273-1280. [ABSTRACT FROM AUTHOR]

Background: Diffusion tensor imaging (DTI) has been applied in the lumbar and sacral nerves in vivo, but information about the reproducibility of this method is needed before DTI can be used reliably in clinical practice across centers.Purpose: In this multicenter study the reproducibility of DTI of the lumbosacral nerves in healthy volunteers was investigated.Study Type: Prospective control series.Subjects: Twenty healthy subjects.Field Strength/sequence: 3T MRI. 3D turbo spin echo, and 3.0 mm isotropic DTI scan.Assessment: The DTI scan was performed three times (twice in the same session, intrascan reproducibility, and once after an hour, interscan reproducibility). At site 2, 1 week later, the protocol was repeated (interweek reproducibility). Fiber tractography (FT) of the lumbar and sacral nerves (L3-S2) was performed to obtain values for fractional anisotropy, mean, axial, and radial diffusivity.Statistical Tests: Reproducibility was determined using the intraclass correlation coefficient (ICC), and power calculations were performed.Results: FT was successful and reproducible in all datasets. ICCs for all diffusion parameters were high for intrascan (ranging from 0.70-0.85), intermediate for interscan (ranging from 0.61-0.73), and interweek reliability (ranging from 0.58-0.62). There were small but significant differences between the interweek diffusivity values (P < 0.0005). Depending on the effect size, nerve location, and parameter of interest, power calculations showed that sample sizes between 10 and 232 subjects are needed for cross-sectional studies.Data Conclusion: We found that DTI and FT of the lumbosacral nerves have intermediate to high reproducibility within and between scans. Based on these results, 10-58 subjects are needed to find a 10% change in parameters in cross-sectional studies of the lumbar and sacral nerves. The small significant differences of the interweek comparison suggest that results from longitudinal studies need to be interpreted carefully, since small differences may also be caused by factors other than disease progression or therapeutic effects.Level Of Evidence: 1 Technical Efficacy: Stage 2 J. Magn. Reson. Imaging 2018;48:951-963. [ABSTRACT FROM AUTHOR]

Background: Renal steatosis (fatty kidney) is a potential biomarker for obesity-related renal disease; however, noninvasive assessment of renal fat content remains a technical challenge.Purpose: To evaluate reproducibility and explore clinical application of renal metabolic imaging for the quantification of renal triglyceride content (TG) using proton magnetic resonance spectroscopy (1 H-MRS).Study Type: Reproducibility and clinical cohort study.Population: Twenty-three healthy volunteers (mean age 30.1 ± 13.4 years) and 15 patients with type 2 diabetes mellitus (T2DM) (mean age 59.3 ± 7.0 years).Field Strength/sequence: 3T, single-voxel point resolved spectroscopy (PRESS).Assessment: Intra- and interexamination reproducibility of renal TG was assessed in healthy volunteers, and compared to T2DM patients. Intraexamination differences were obtained by repeating the 1 H-MRS measurement directly after the first 1 H-MRS without repositioning of the subject or changing surface coil and measurement volumes. Interexamination variability was studied by repeating the scan protocol after removal and replacement of the subject in the magnet, and subsequent repositioning of body coil and measurement volumes.Statistical Tests: Reproducibility was determined using Pearson's correlation and Bland-Altman analyses. Differences in TG% between healthy volunteers and T2DM patients were assessed using the Mann-Whitney U-test.Results: After logarithmic (log) transformation, both intraexamination (r = 0.91, n = 19) and interexamination (r = 0.73, n = 9) measurements of renal TG content were highly correlated with the first renal TG measurements. Intraexamination and interexamination limits of agreement of renal log TG% were respectively [-1.36%, + 0.84%] and [-0.77%, + 0.62%]. Backtransformed limits of agreement were [-0.89%,+0.57%] and [-0.55%, + 0.43%] multiplied by mean TG for intra- and interexamination measurements. Overall median renal TG content was 0.12% [0.08, 0.22; 25th percentile, 75th percentile] in healthy volunteers and 0.20% [0.13, 0.22] in T2DM patients (P = 0.08).Data Conclusion: Renal metabolic imaging using 3T 1 H-MRS is a reproducible technique for the assessment of renal triglyceride content.Level Of Evidence: 3 Technical Efficacy: Stage 1 J. MAGN. RESON. IMAGING 2018;48:507-513. [ABSTRACT FROM AUTHOR]