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Purpose: T1 mapping is a widely used quantitative MRI technique, but its tissue‐specific values remain inconsistent across protocols, sites, and vendors. The ISMRM Reproducible Research and Quantitative MR study groups jointly launched a challenge to assess the reproducibility of a well‐established inversion‐recovery T1 mapping technique, using acquisition details from a seminal T1 mapping paper on a standardized phantom and in human brains. Methods: The challenge used the acquisition protocol from Barral et al. (2010). Researchers collected T1 mapping data on the ISMRM/NIST phantom and/or in human brains. Data submission, pipeline development, and analysis were conducted using open‐source platforms. Intersubmission and intrasubmission comparisons were performed. Results: Eighteen submissions (39 phantom and 56 human datasets) on scanners by three MRI vendors were collected at 3 T (except one, at 0.35 T). The mean coefficient of variation was 6.1% for intersubmission phantom measurements, and 2.9% for intrasubmission measurements. For humans, the intersubmission/intrasubmission coefficient of variation was 5.9/3.2% in the genu and 16/6.9% in the cortex. An interactive dashboard for data visualization was also developed: https://rrsg2020.dashboards.neurolibre.org. Conclusion: The T1 intersubmission variability was twice as high as the intrasubmission variability in both phantoms and human brains, indicating that the acquisition details in the original paper were insufficient to reproduce a quantitative MRI protocol. This study reports the inherent uncertainty in T1 measures across independent research groups, bringing us one step closer to a practical clinical baseline of T1 variations in vivo. [ABSTRACT FROM AUTHOR]

Purpose: Arterial spin labeling (ASL) is a widely used contrast‐free MRI method for assessing cerebral blood flow (CBF). Despite the generally adopted ASL acquisition guidelines, there is still wide variability in ASL analysis. We explored this variability through the ISMRM‐OSIPI ASL‐MRI Challenge, aiming to establish best practices for more reproducible ASL analysis. Methods: Eight teams analyzed the challenge data, which included a high‐resolution T1‐weighted anatomical image and 10 pseudo‐continuous ASL datasets simulated using a digital reference object to generate ground‐truth CBF values in normal and pathological states. We compared the accuracy of CBF quantification from each team's analysis to the ground truth across all voxels and within predefined brain regions. Reproducibility of CBF across analysis pipelines was assessed using the intra‐class correlation coefficient (ICC), limits of agreement (LOA), and replicability of generating similar CBF estimates from different processing approaches. Results: Absolute errors in CBF estimates compared to ground‐truth synthetic data ranged from 18.36 to 48.12 mL/100 g/min. Realistic motion incorporated into three datasets produced the largest absolute error and variability between teams, with the least agreement (ICC and LOA) with ground‐truth results. Fifty percent of the submissions were replicated, and one produced three times larger CBF errors (46.59 mL/100 g/min) compared to submitted results. Conclusions: Variability in CBF measurements, influenced by differences in image processing, especially to compensate for motion, highlights the significance of standardizing ASL analysis workflows. We provide a recommendation for ASL processing based on top‐performing approaches as a step toward ASL standardization. [ABSTRACT FROM AUTHOR]

Purpose: To reduce the inter‐scanner variability of diffusion MRI (dMRI) measures between scanners from different vendors by developing a vendor‐neutral dMRI pulse sequence using the open‐source vendor‐agnostic Pulseq platform. Methods: We implemented a standard EPI based dMRI sequence in Pulseq. We tested it on two clinical scanners from different vendors (Siemens Prisma and GE Premier), systematically evaluating and comparing the within‐ and inter‐scanner variability across the vendors, using both the vendor‐provided and Pulseq dMRI sequences. Assessments covered both a diffusion phantom and three human subjects, using standard error (SE) and Lin's concordance correlation to measure the repeatability and reproducibility of standard DTI metrics including fractional anisotropy (FA) and mean diffusivity (MD). Results: Identical dMRI sequences were executed on both scanners using Pulseq. On the phantom, the Pulseq sequence showed more than a 2.5× reduction in SE (variability) across Siemens and GE scanners. Furthermore, Pulseq sequences exhibited markedly reduced SE in‐vivo, maintaining scan‐rescan repeatability while delivering lower variability in FA and MD (more than 50% reduction in cortical/subcortical regions) compared to vendor‐provided sequences. Conclusion: The Pulseq diffusion sequence reduces the cross‐scanner variability for both phantom and in‐vivo data, which will benefit multi‐center neuroimaging studies and improve the reproducibility of neuroimaging studies. [ABSTRACT FROM AUTHOR]

Purpose: Quantitative multi‐parameter mapping (MPM) provides maps of physical quantities representing physiologically meaningful tissue characteristics, which allows to investigate microstructure‐function relationships reflecting normal or pathologic processes in the brain. However, the achievable spatial resolution and stability of MPM for basic research or clinical applications is severely constrained by SNR limits of the MR acquisition process, resulting in relatively long acquisition times. To increase SNR, we denoise MPM acquisitions using principal component analysis along tensors exploiting the Marchenko‐Pastur law (tMPPCA). Methods: tMPPCA denoising was applied to three sets of MPM raw data before the quantification of maps of proton density, magnetization transfer saturation, R1, and R2*. The regional SNR gain for high‐resolution MPM was investigated as well as reproducibility gains for clinically optimized protocols with moderate and high acceleration factors at different image resolutions. Results: Substantial noise reduction in raw data was achieved, resulting in reduced noise for quantitative mapping up to sixfold without introducing bias of mean values (below 1%). Scan–rescan fluctuations were reduced up to threefold. Denoising allowed to decrease the voxel volume fourfold at the same scan time or reduce the scan time twofold at same voxel volume without loss of sensitivity. Conclusions: tMPPCA denoising can (a) improve of fine spatial and temporal patterns, (b) considerably reduce scan time for clinical applications, or (c) increase resolution to potentially push cutting‐edge MPM protocols from the upper to the lower limit of the mesoscopic scale. [ABSTRACT FROM AUTHOR]

The 2015 consensus statement published by the International Society for Magnetic Resonance in Medicine (ISMRM) Perfusion Study Group and the European Cooperation in Science and Technology (COST) Action ASL in Dementia aimed to encourage the implementation of robust arterial spin labeling (ASL) perfusion MRI for clinical applications and promote consistency across scanner types, sites, and studies. Subsequently, the recommended 3D pseudo‐continuous ASL sequence has been implemented by most major MRI manufacturers. However, ASL remains a rapidly and widely developing field, leading inevitably to further divergence of the technique and its associated terminology, which could cause confusion and hamper research reproducibility. On behalf of the ISMRM Perfusion Study Group, and as part of the ISMRM Open Science Initiative for Perfusion Imaging (OSIPI), the ASL Lexicon Task Force has been working on the development of an ASL Lexicon and Reporting Recommendations for perfusion imaging and analysis, aiming to (1) develop standardized, consensus nomenclature and terminology for the broad range of ASL imaging techniques and parameters, as well as for the physiological constants required for quantitative analysis; and (2) provide a community‐endorsed recommendation of the imaging parameters that we encourage authors to include when describing ASL methods in scientific reports/papers. In this paper, the sequences and parameters in (pseudo‐)continuous ASL, pulsed ASL, velocity‐selective ASL, and multi‐timepoint ASL for brain perfusion imaging are included. However, the content of the lexicon is not intended to be limited to these techniques, and this paper provides the foundation for a growing online inventory that will be extended by the community as further methods and improvements are developed and established. [ABSTRACT FROM AUTHOR]

Purpose: To demonstrate proof‐of‐concept of a T2*‐sensitized oxygen‐enhanced MRI (OE‐MRI) method at 3T by assessing signal characteristics, repeatability, and reproducibility of dynamic lung OE‐MRI metrics in healthy volunteers. Methods: We performed sequence‐specific simulations for protocol optimisation and acquired free‐breathing OE‐MRI data from 16 healthy subjects using a dual‐echo RF‐spoiled gradient echo approach at 3T across two institutions. Non‐linear registration and tissue density correction were applied. Derived metrics included percent signal enhancement (PSE), ∆R2* and wash‐in time normalized for breathing rate (τ‐nBR). Inter‐scanner reproducibility and intra‐scanner repeatability were evaluated using intra‐class correlation coefficient (ICC), repeatability coefficient, reproducibility coefficient, and Bland–Altman analysis. Results: Simulations and experimental data show negative contrast upon oxygen inhalation, due to substantial dominance of ∆R2* at TE > 0.2 ms. Density correction improved signal fluctuations. Density‐corrected mean PSE values, aligned with simulations, display TE‐dependence, and an anterior‐to‐posterior PSE reduction trend at TE1. ∆R2* maps exhibit spatial heterogeneity in oxygen delivery, featuring anterior‐to‐posterior R2* increase. Mean T2* values across 32 scans were 0.68 and 0.62 ms for pre‐ and post‐O2 inhalation, respectively. Excellent or good agreement emerged from all intra‐, inter‐scanner and inter‐rater variability tests for PSE and ∆R2*. However, ICC values for τ‐nBR demonstrated limited agreement between repeated measures. Conclusion: Our results demonstrate the feasibility of a T2*‐weighted method utilizing a dual‐echo RF‐spoiled gradient echo approach, simultaneously capturing PSE, ∆R2* changes, and oxygen wash‐in during free‐breathing. The excellent or good repeatability and reproducibility on intra‐ and inter‐scanner PSE and ∆R2* suggest potential utility in multi‐center clinical applications. [ABSTRACT FROM AUTHOR]

Purpose: To develop a portable MR perfusion phantom for quality‐controlled assessment and reproducibility of arterial spin labeled (ASL) perfusion measurement. Methods: A 3D‐printed perfusion phantom was developed that mimics the branching of arterial vessels, capillaries, and a chamber containing cellulose sponge representing tissue characteristics. A peristaltic pump circulated distilled water through the phantom, and was first evaluated at 300, 400, and 500 mL/min. Longitudinal reproducibility of perfusion was performed using 2D pseudo‐continuous ASL at 20 post‐label delays (PLDs, ranging between 0.2 and 7.8 s at 0.4‐s intervals) over a period of 16 weeks, with three repetitions each week. Multi‐PLD data were fitted into a general kinetic model for perfusion quantification (f) and arterial transit time (ATT). Intraclass correlation coefficient was used to assess intersession reproducibility. Results: MR perfusion signals acquired in the 3D‐printed perfusion phantom agreed well with the experimental conditions, with progressively increasing signal intensities and decreasing ATT for pump flow rates from 300 to 500 mL/min. The perfusion signal at 400 mL/min and the general kinetic model–derived f and ATT maps were similar across all PLDs for both intrasession and intersession reproducibility. Across all 48 experimental time points, the average f was 75.55 ± 3.83 × 10−3 mL/mL/s, the corresponding ATT was 2.10 ± 0.20 s, and the T1 was 1.84 ± 0.102 s. Intraclass correlation coefficient was 0.92 (95% confidence interval 0.83–0.97) for f, 0.96 (0.91–0.99) for ATT, and 0.94 (0.88–0.98) for T1, demonstrating excellent reproducibility. Conclusion: A simple, portable 3D‐printed perfusion phantom with excellent reproducibility of 2D pseudo‐continuous ASL measurements was demonstrated that can serve for quality‐controlled and reliable measurements of ASL perfusion. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the influence of the sodium (Na) reference tube location in a birdcage coil on the quantification of Na in the calf muscle. Two correction methods were also evaluated. Method: Eight (4 × 20 mM, 4 × 30 mM Na) reference tubes were placed along the inner surface of the coil and one (30 mM Na) tube more centrally near the tibia. In two volunteers, four repeated UTE scans were acquired. In six calf muscles, the Na concentration was calculated based on each reference tube. Flip angle mapping of a homogenous Na phantom was used for correcting intensity values. Alternatively, a normalized intensity map was used for correcting the in vivo signal intensities. Results were given as range or SD of Na concentration measurements over the reference tubes. Results: For calf Na measurements, there was limited space for positioning reference tubes away from coil B1 inhomogeneity. In both volunteers, the Na quantification depended greatly on the reference tube used with a range of up to 10 mM. The central tube location gave a Na quantification close to the mean of the other tubes. The flip angle and normalized signal intensity phantom‐based correction methods decreased the quantification variation from 14.9% to 5.0% and 10.4% to 2.7%, respectively. Both correction methods had little influence (< 2.3%) on quantification based on the central tube. Conclusion: Despite use of a birdcage coil, location of the reference tube had a great impact on Na quantification in the calf muscles. Although both correction methods did reduce this variation, placing the reference tube more centrally was found to give the most reliable results. [ABSTRACT FROM AUTHOR]

PurposeTo implement a fully automated atlas-based method for prescribing 3D PRESS MR spectroscopic imaging (MRSI).MethodsThe PRESS selected volume and outer-volume suppression bands were predefined on the MNI152 standard template image. The template image was aligned to the subject T1 -weighted image during a scan, and the resulting transformation was then applied to the predefined prescription. To evaluate the method, H-1 MRSI data were obtained in repeat scan sessions from 20 healthy volunteers. In each session, datasets were acquired twice without repositioning. The overlap ratio of the prescribed volume in the two sessions was calculated and the reproducibility of inter- and intrasession metabolite peak height and area ratios was measured by the coefficient of variation (CoV). The CoVs from intra- and intersession were compared by a paired t-test.ResultsThe average overlap ratio of the automatically prescribed selection volumes between two sessions was 97.8%. The average voxel-based intersession CoVs were less than 0.124 and 0.163 for peak height and area ratios, respectively. Paired t-test showed no significant difference between the intra- and intersession CoVs.ConclusionThe proposed method provides a time efficient method to prescribe 3D PRESS MRSI with reproducible imaging positioning and metabolite measurements. Magn Reson Med 79:636-642, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Purpose: To evaluate multicenter repeatability and reproducibility of T1 and T2 maps generated using MR fingerprinting (MRF) in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom and in prostatic tissues. Methods: MRF experiments were performed on 5 different 3 Tesla MRI scanners at 3 different institutions: University Hospitals Cleveland Medical Center (Cleveland, OH), Brigham and Women's Hospital (Boston, MA) in the United States, and Diagnosticos da America (Rio de Janeiro, RJ) in Brazil. Raw MRF data were reconstructed using a Gadgetron‐based MRF online reconstruction pipeline to yield quantitative T1 and T2 maps. The repeatability of T1 and T2 values over 6 measurements in the International Society for Magnetic Resonance in Medicine/National Institute of Standards and Technology MRI system phantom was assessed to demonstrate intrascanner variation. The reproducibility between the 4 clinical scanners was assessed to demonstrate interscanner variation. The same‐day test–retest normal prostate mean T1 and T2 values from peripheral zone and transitional zone were also compared using the intraclass correlation coefficient and Bland–Altman analysis. Results: The intrascanner variation of values measured using MRF was less than 2% for T1 and 4.7% for T2 for relaxation values, within the range of 307.7 to 2360 ms for T1 and 19.1 to 248.5 ms for T2. Interscanner measurements showed that the T1 variation was less than 4.9%, and T2 variation was less than 8.1% between multicenter scanners. Both T1 and T2 values in in vivo prostatic tissue demonstrated high test–retest reliability (intraclass correlation coefficient > 0.92) and strong linear correlation (R2 > 0.840). Conclusion: Prostate MRF measurements of T1 and T2 are repeatable and reproducible between MRI scanners at different centers on different continents for the above measurement ranges. [ABSTRACT FROM AUTHOR]

Purpose: We developed an end‐to‐end workflow that starts with a vendor‐neutral acquisition and tested the hypothesis that vendor‐neutral sequences decrease inter‐vendor variability of T1, magnetization transfer ratio (MTR), and magnetization transfer saturation‐index (MTsat) measurements. Methods: We developed and deployed a vendor‐neutral 3D spoiled gradient‐echo (SPGR) sequence on three clinical scanners by two MRI vendors. We then acquired T1 maps on the ISMRM‐NIST system phantom, as well as T1, MTR, and MTsat maps in three healthy participants. We performed hierarchical shift function analysis in vivo to characterize the differences between scanners when the vendor‐neutral sequence is used instead of commercial vendor implementations. Inter‐vendor deviations were compared for statistical significance to test the hypothesis. Results: In the phantom, the vendor‐neutral sequence reduced inter‐vendor differences from 8% to 19.4% to 0.2% to 5% with an overall accuracy improvement, reducing ground truth T1 deviations from 7% to 11% to 0.2% to 4%. In vivo, we found that the variability between vendors is significantly reduced (p = 0.015) for all maps (T1, MTR, and MTsat) using the vendor‐neutral sequence. Conclusion: We conclude that vendor‐neutral workflows are feasible and compatible with clinical MRI scanners. The significant reduction of inter‐vendor variability using vendor‐neutral sequences has important implications for qMRI research and for the reliability of multicenter clinical trials. [ABSTRACT FROM AUTHOR]

Purpose: Cardiac-induced liver motion can bias liver ADC measurements and compromise reproducibility. The purpose of this work was to enable motion-robust DWI on multiple MR scanners and assess reproducibility of the resulting liver ADC measurements., Methods: First moment-optimized diffusion imaging (MODI) was implemented on three MR scanners with various gradient performances and field strengths. MODI-DWI and conventional Stejskal-Tanner monopolar (MONO) DWI were acquired in eight (N = 8) healthy volunteers on each scanner, and DWI repetitions were combined using three different averaging methods. For each combination of scanner, acquisition, and averaging method, ADC measurements from each liver segment were collected. Systematic differences in ADC values between scanners and methods were assessed with linear mixed effects modeling, and reproducibility was quantified via reproducibility coefficients., Results: MODI reduced left-right liver lobe ADC bias from 0.43 × 10 -3  mm 2 /s (MONO) to 0.19 × 10 -3  mm 2 /s (MODI) when simple (unweighted) repetition averaging was used. The bias was reduced from 0.23 × 10 -3  mm 2 /s to 0.06 × 10 -3  mm 2 /s using weighted averaging, and 0.14 × 10 -3  mm 2 /s to 0.01 × 10 -3  mm 2 /s using squared weighted averaging. There was no significant difference in ADC measurements between field strengths or scanner gradient performance. MODI improved reproducibility coefficients compared to MONO: 0.84 × 10 -3  mm 2 /s vs. 0.63 × 10 -3  mm 2 /s (MODI vs. MONO) for simple averaging, 0.66 × 10 -3  mm 2 /s vs. 0.50 × 10 -3  mm 2 /s for weighted averaging, and 0.61 × 10 -3  mm 2 /s vs. 0.47 × 10 -3  mm 2 /s for squared weighted averaging., Conclusion: The feasibility of motion-robust liver DWI using MODI was demonstrated on multiple MR scanners. MODI improved interlobar agreement and reproducibility of ADC measurements in a healthy cohort., (© 2024 The Author(s). Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Purpose: T 1 mapping is a widely used quantitative MRI technique, but its tissue-specific values remain inconsistent across protocols, sites, and vendors. The ISMRM Reproducible Research and Quantitative MR study groups jointly launched a challenge to assess the reproducibility of a well-established inversion-recovery T 1 mapping technique, using acquisition details from a seminal T 1 mapping paper on a standardized phantom and in human brains., Methods: The challenge used the acquisition protocol from Barral et al. (2010). Researchers collected T 1 mapping data on the ISMRM/NIST phantom and/or in human brains. Data submission, pipeline development, and analysis were conducted using open-source platforms. Intersubmission and intrasubmission comparisons were performed., Results: Eighteen submissions (39 phantom and 56 human datasets) on scanners by three MRI vendors were collected at 3 T (except one, at 0.35 T). The mean coefficient of variation was 6.1% for intersubmission phantom measurements, and 2.9% for intrasubmission measurements. For humans, the intersubmission/intrasubmission coefficient of variation was 5.9/3.2% in the genu and 16/6.9% in the cortex. An interactive dashboard for data visualization was also developed: https://rrsg2020.dashboards.neurolibre.org., Conclusion: The T 1 intersubmission variability was twice as high as the intrasubmission variability in both phantoms and human brains, indicating that the acquisition details in the original paper were insufficient to reproduce a quantitative MRI protocol. This study reports the inherent uncertainty in T 1 measures across independent research groups, bringing us one step closer to a practical clinical baseline of T 1 variations in vivo., (© 2024 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Purpose: This study is to investigate time‐resolved 13C MR spectroscopy (MRS) as an alternative to imaging for assessing pyruvate metabolism using hyperpolarized (HP) [1‐13C]pyruvate in the human brain. Methods: Time‐resolved 13C spectra were acquired from four axial brain slices of healthy human participants (n = 4) after a bolus injection of HP [1‐13C]pyruvate. 13C MRS with low flip‐angle excitations and a multichannel 13C/1H dual‐frequency radiofrequency (RF) coil were exploited for reliable and unperturbed assessment of HP pyruvate metabolism. Slice‐wise areas under the curve (AUCs) of 13C‐metabolites were measured and kinetic analysis was performed to estimate the production rates of lactate and HCO3‐. Linear regression analysis between brain volumes and HP signals was performed. Region‐focused pyruvate metabolism was estimated using coil‐wise 13C reconstruction. Reproducibility of HP pyruvate exams was presented by performing two consecutive injections with a 45‐minutes interval. Results: [1‐13C]Lactate relative to the total 13C signal (tC) was 0.21–0.24 in all slices. [13C]HCO3‐/tC was 0.065–0.091. Apparent conversion rate constants from pyruvate to lactate and HCO3‐ were calculated as 0.014–0.018 s−1 and 0.0043–0.0056 s−1, respectively. Pyruvate/tC and lactate/tC were in moderate linear relationships with fractional gray matter volume within each slice. White matter presented poor linear regression fit with HP signals, and moderate correlations of the fractional cerebrospinal fluid volume with pyruvate/tC and lactate/tC were measured. Measured HP signals were comparable between two consecutive exams with HP [1‐13C]pyruvate. Conclusions: Dynamic MRS in combination with multichannel RF coils is an affordable and reliable alternative to imaging methods in investigating cerebral metabolism using HP [1‐13C]pyruvate. [ABSTRACT FROM AUTHOR]

Purpose: Diffusion‐weighted imaging allows investigators to identify structural, microstructural, and connectivity‐based differences between subjects, but variability due to session and scanner biases is a challenge. Methods: To investigate DWI variability, we present MASiVar, a multisite data set consisting of 319 diffusion scans acquired at 3 T from b = 1000 to 3000 s/mm2 across 14 healthy adults, 83 healthy children (5 to 8 years), three sites, and four scanners as a publicly available, preprocessed, and de‐identified data set. With the adult data, we demonstrate the capacity of MASiVar to simultaneously quantify the intrasession, intersession, interscanner, and intersubject variability of four common DWI processing approaches: (1) a tensor signal representation, (2) a multi‐compartment neurite orientation dispersion and density model, (3) white‐matter bundle segmentation, and (4) structural connectomics. Respectively, we evaluate region‐wise fractional anisotropy, mean diffusivity, and principal eigenvector; region‐wise CSF volume fraction, intracellular volume fraction, and orientation dispersion index; bundle‐wise shape, volume, fractional anisotropy, and length; and whole connectome correlation and maximized modularity, global efficiency, and characteristic path length. Results: We plot the variability in these measures at each level and find that it consistently increases with intrasession to intersession to interscanner to intersubject effects across all processing approaches and that sometimes interscanner variability can approach intersubject variability. Conclusions: This study demonstrates the potential of MASiVar to more globally investigate DWI variability across multiple levels and processing approaches simultaneously and suggests harmonization between scanners for multisite analyses should be considered before inference of group differences on subjects. [ABSTRACT FROM AUTHOR]

Purpose: Assessment of the blood--brain barrier (BBB) permeability without the need for contrast agent is desirable, and the ability to measure the permeability to small molecules such as water may further increase the sensitivity in detecting diseases. This study proposed a time-efficient, noncontrast method to measure BBB permeability to water, evaluated its test--retest reproducibility, and compared it with a contrast agent--based method. Methods: A single-delay water extraction with phase-contrast arterial spin tagging (WEPCAST) method was devised in which spatial profile of the signal along the superior sagittal sinus was used to estimate bolus arrival time, and the WEPCAST signal at the corresponding location was used to compute water extraction fraction, which was combined with global cerebral blood flow to estimate BBB permeability surface area product to water. The reliability of WEPCAST sequence was examined in terms of intrasession, intersession, and inter-vendor (Philips [Ingenia, Best, the Netherlands] and Siemens [Prisma, Erlangen, Germany]) reproducibility. Finally, we compared this new technique to a contrast agent--based method. Results: Single-delay WEPCAST reduced the scan duration from approximately 20 min to 5 min. Extract fraction values estimated from single-delay WEPCAST showed good consistency with the multi-delay method (R = 0.82, P = .004). Group-averaged permeability surface area product values were found to be 137.5 ± 9.3 mL/100 g/min. Intrasession, intersession, and inter-vendor coefficient of variation of the permeability surface area product values were 6.6 ± 4.5%, 6.9 ± 3.7%, and 8.9 ± 3.0%, respectively. Finally, permeability surface area product obtained from WEPCAST MRI showed a significant correlation with that from the contrast-based method (R = .73, P = .02). Conclusion: Single-delay WEPCAST MRI can measure BBB permeability to water within 5 min with an intrasession, intersession, and inter-vendor test--retest reproducibility of 6% to 9%. This method may provide a useful marker of BBB breakdown in clinical studies. [ABSTRACT FROM AUTHOR]

Purpose: To assess the reproducibility of percentage ventilated lung volume (%VV) measurements in healthy volunteers acquired by fluorine (19F)‐MRI of inhaled perfluoropropane, implemented at two research sites. Methods: In this prospective, ethically approved study, 40 healthy participants were recruited (May 2018‐June 2019) to one of two research sites. Participants underwent a single MRI scan session on a 3T scanner, involving periodic inhalation of a 79% perfluoropropane/21% oxygen gas mixture. Each gas inhalation session lasted about 30 seconds, consisting of three deep breaths of gas followed by a breath‐hold. Four 19F‐MR ventilation images were acquired per participant, each separated by approximately 6 minutes. The value of %VV was determined by registering separately acquired 1H images to ventilation images before semi‐automated image segmentation, performed independently by two observers. Reproducibility of %VV measurements was assessed by components of variance, intraclass correlation coefficients, coefficients of variation (CoV), and the Dice similarity coefficient. Results: The MRI scans were well tolerated throughout, with no adverse events. There was a high degree of consistency in %VV measurements for each participant (CoVobserver1 = 0.43%; CoVobserver2 = 0.63%), with overall precision of %VV measurements determined to be within ± 1.7% (95% confidence interval). Interobserver agreement in %VV measurements revealed a high mean Dice similarity coefficient (SD) of 0.97 (0.02), with only minor discrepancies between observers. Conclusion: We demonstrate good reproducibility of %VV measurements in a group of healthy participants using 19F‐MRI of inhaled perfluoropropane. Our methods have been successfully implemented across two different study sites, supporting the feasibility of performing larger multicenter clinical studies. [ABSTRACT FROM AUTHOR]

Purpose: To assess the effects of blip‐up and ‐down echo planar imaging (EPI) acquisition designs, with different choices of phase‐encoding directions (PEDs) on the reproducibility of diffusion MRI (dMRI)‐derived metrics in the human brain. Methods: Diffusion MRI data in seven subjects were acquired five times, each with five different protocols. The base design included 64 diffusion directions acquired with anterior‐posterior (AP) PED, the first and second protocols added reverse phase‐encoded b=0s/mm2 posterior‐anterior (PA) PED images. The third one included 32 directions all with PED acquisitions with opposite polarity (AP and PA). The fourth protocol, also with 32 unique directions used four PEDs (AP, PA, right‐left (RL), and left‐right (LR)). The scan time was virtually identical for all protocols. The variability of diffusion MRI metrics for each subject and each protocol was computed across the different sessions. Results: The highest reproducibility for all dMRI metrics was obtained with protocol four (AP/PA‐RL/LR, ie, four‐way PED). Protocols that used only b=0s/mm2 for distortion correction, which are the most widely used designs, had the lowest reproducibility. Conclusions: An acquisition design with four PEDs, including all DWIs in addition to b=0s/mm2 images should be used to achieve high reproducibility in diffusion MRI studies. [ABSTRACT FROM AUTHOR]

Purpose: The aim of this work is to shed light on the issue of reproducibility in MR image reconstruction in the context of a challenge. Participants had to recreate the results of "Advances in sensitivity encoding with arbitrary k‐space trajectories" by Pruessmann et al. Methods: The task of the challenge was to reconstruct radially acquired multicoil k‐space data (brain/heart) following the method in the original paper, reproducing its key figures. Results were compared to consolidated reference implementations created after the challenge, accounting for the two most common programming languages used in the submissions (Matlab/Python). Results: Visually, differences between submissions were small. Pixel‐wise differences originated from image orientation, assumed field‐of‐view, or resolution. The reference implementations were in good agreement, both visually and in terms of image similarity metrics. Discussion and Conclusion: While the description level of the published algorithm enabled participants to reproduce CG‐SENSE in general, details of the implementation varied, for example, density compensation or Tikhonov regularization. Implicit assumptions about the data lead to further differences, emphasizing the importance of sufficient metadata accompanying open datasets. Defining reproducibility quantitatively turned out to be nontrivial for this image reconstruction challenge, in the absence of ground‐truth results. Typical similarity measures like NMSE of SSIM were misled by image intensity scaling and outlier pixels. Thus, to facilitate reproducibility, researchers are encouraged to publish code and data alongside the original paper. Future methodological papers on MR image reconstruction might benefit from the consolidated reference implementations of CG‐SENSE presented here, as a benchmark for methods comparison. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the repeatability and reproducibility of radiomic features extracted from MR images and provide a workflow to identify robust features. Methods: T2‐weighted images of a pelvic phantom were acquired on three scanners of two manufacturers and two magnetic field strengths. The repeatability and reproducibility of features were assessed by the intraclass correlation coefficient and the concordance correlation coefficient, respectively, and by the within‐subject coefficient of variation, considering repeated acquisitions with and without phantom repositioning, and with different scanner and acquisition parameters. The features showing intraclass correlation coefficient or concordance correlation coefficient >0.9 were selected, and their dependence on shape information (Spearman's ρ > 0.8) analyzed. They were classified for their ability to distinguish textures, after shuffling voxel intensities of images. Results: From 944 two‐dimensional features, 79.9% to 96.4% showed excellent repeatability in fixed position across all scanners. A much lower range (11.2% to 85.4%) was obtained after phantom repositioning. Three‐dimensional extraction did not improve repeatability performance. Excellent reproducibility between scanners was observed in 4.6% to 15.6% of the features, at fixed imaging parameters. In addition, 82.4% to 94.9% of the features showed excellent agreement when extracted from images acquired with echo times 5 ms apart, but decreased with increasing echo‐time intervals, and 90.7% of the features exhibited excellent reproducibility for changes in pulse repetition time. Of nonshape features, 2.0% was identified as providing only shape information. Conclusion: We showed that radiomic features are affected by MRI protocols and propose a general workflow to identify repeatable, reproducible, and informative radiomic features to ensure robustness of clinical studies. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the accuracy of T2‐based whole‐brain oxygen extraction fraction (OEF) estimation by comparing it with gold standard 15O‐PET measurements. Methods: Sixteen healthy adult subjects underwent MRI and 15O‐PET OEF measurements on the same day. On MRI, whole‐brain OEF was quantified by T2‐relaxation‐under‐spin‐tagging (TRUST) MRI, based on subject‐specific hematocrit. The TRUST OEF was compared to the whole‐brain averaged OEF produced by 15O‐PET. Agreement between TRUST and 15O‐PET whole‐brain OEF measurements was examined in terms of intraclass correlation coefficient (ICC) and in absolute OEF values. In a subset of 10 subjects, test‐retest reproducibility of whole‐brain OEF was also evaluated and compared between the two modalities. Results: Across the 16 subjects, the mean whole‐brain OEF of TRUST and 15O‐PET were 36.44 ± 4.07% and 36.45 ± 3.65%, respectively, showing no difference between the two modalities (P =.99). TRUST whole‐brain OEF strongly correlated with that of 15O‐PET (N = 16, ICC = 0.90, P = 4 × 10−7). The coefficient‐of‐variation of TRUST and 15O‐PET whole‐brain OEF measurements were 1.79 ± 0.67% and 2.06 ± 1.55%, respectively, showing no difference between the two modalities (N = 10, P =.64). Further analyses on the effect of hematocrit revealed that correlation between PET OEF and TRUST OEF with assumed hematocrit remained significant (ICC = 0.8, P < 2 × 10−5). Conclusion: Whole‐brain OEF measured by TRUST was in excellent agreement with gold standard 15O‐PET, with highly comparable accuracy and reproducibility. These findings suggest that TRUST MRI can provide accurate quantification of whole‐brain OEF noninvasively. [ABSTRACT FROM AUTHOR]

Purpose: To demonstrate proof-of-concept of a T 2 *-sensitized oxygen-enhanced MRI (OE-MRI) method at 3T by assessing signal characteristics, repeatability, and reproducibility of dynamic lung OE-MRI metrics in healthy volunteers., Methods: We performed sequence-specific simulations for protocol optimisation and acquired free-breathing OE-MRI data from 16 healthy subjects using a dual-echo RF-spoiled gradient echo approach at 3T across two institutions. Non-linear registration and tissue density correction were applied. Derived metrics included percent signal enhancement (PSE), ∆R 2 * and wash-in time normalized for breathing rate (τ-nBR). Inter-scanner reproducibility and intra-scanner repeatability were evaluated using intra-class correlation coefficient (ICC), repeatability coefficient, reproducibility coefficient, and Bland-Altman analysis., Results: Simulations and experimental data show negative contrast upon oxygen inhalation, due to substantial dominance of ∆R 2 * at TE > 0.2 ms. Density correction improved signal fluctuations. Density-corrected mean PSE values, aligned with simulations, display TE-dependence, and an anterior-to-posterior PSE reduction trend at TE 1 . ∆R 2 * maps exhibit spatial heterogeneity in oxygen delivery, featuring anterior-to-posterior R 2 * increase. Mean T 2 * values across 32 scans were 0.68 and 0.62 ms for pre- and post-O 2 inhalation, respectively. Excellent or good agreement emerged from all intra-, inter-scanner and inter-rater variability tests for PSE and ∆R 2 *. However, ICC values for τ-nBR demonstrated limited agreement between repeated measures., Conclusion: Our results demonstrate the feasibility of a T 2 *-weighted method utilizing a dual-echo RF-spoiled gradient echo approach, simultaneously capturing PSE, ∆R 2 * changes, and oxygen wash-in during free-breathing. The excellent or good repeatability and reproducibility on intra- and inter-scanner PSE and ∆R 2 * suggest potential utility in multi-center clinical applications., (© 2023 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals LLC on behalf of International Society for Magnetic Resonance in Medicine.)

Purpose: There is an absence of reproducibility studies on MRI‐based body composition analysis in current literature. Therefore, the aim of this study was to investigate the between‐scanner reproducibility and the repeatability of a method for MRI‐based body composition analysis. Methods: Eighteen healthy volunteers of varying body mass index and adiposity were each scanned twice on five different 1.5T and 3T scanners from three different vendors. Two‐point Dixon neck‐to knee images and two additional liver scans were acquired with similar protocols. Visceral adipose tissue (VAT) volume, abdominal subcutaneous adipose tissue (ASAT) volume, thigh muscle volume, and muscle fat infiltration (MFI) in the thigh muscle were measured. Liver proton density fat fraction (PDFF) was assessed using two different methods, the scanner vendor's 6‐point method and an in‐house 2‐point method. Within‐scanner test‐retest repeatability and between‐scanner reproducibility were calculated using analysis of variance. Results: Repeatability coefficients were 13 centiliters (cl) (VAT), 24 cl (ASAT), 17 cl (total thigh muscle volume), 0.53% (MFI), and 1.27‐1.37% for liver PDFF. Reproducibility coefficients were 24 cl (VAT), 42 cl (ASAT), 31 cl (total thigh muscle volume), 1.44% (MFI), and 2.37‐2.40% for liver PDFF. Conclusion: For all measures except MFI, the within‐scanner repeatability explained much of the overall reproducibility. The two methods for measuring liver fat had similar reproducibility. This study showed that the investigated method eliminates effects due to scanner differences. The results can be used for power calculations in clinical studies or to better understand the scanner‐induced variability in clinical applications. [ABSTRACT FROM AUTHOR]

Purpose: To develop a reproducible and fast method to reconstruct MR fingerprinting arterial spin labeling (MRF‐ASL) perfusion maps using deep learning. Method: A fully connected neural network, denoted as DeepMARS, was trained using simulation data and added Gaussian noise. Two MRF‐ASL models were used to generate the simulation data, specifically a single‐compartment model with 4 unknowns parameters and a two‐compartment model with 7 unknown parameters. The DeepMARS method was evaluated using MRF‐ASL data from healthy subjects (N = 7) and patients with Moymoya disease (N = 3). Computation time, coefficient of determination (R2), and intraclass correlation coefficient (ICC) were compared between DeepMARS and conventional dictionary matching (DM). The relationship between DeepMARS and Look–Locker PASL was evaluated by a linear mixed model. Results: Computation time per voxel was <0.5 ms for DeepMARS and >4 seconds for DM in the single‐compartment model. Compared with DM, the DeepMARS showed higher R2 and significantly improved ICC for single‐compartment derived bolus arrival time (BAT) and two‐compartment derived cerebral blood flow (CBF) and higher or similar R2/ICC for other parameters. In addition, the DeepMARS was significantly correlated with Look–Locker PASL for BAT (single‐compartment) and CBF (two‐compartment). Moreover, for Moyamoya patients, the location of diminished CBF and prolonged BAT shown in DeepMARS was consistent with the position of occluded arteries shown in time‐of‐flight MR angiography. Conclusion: Reconstruction of MRF‐ASL with DeepMARS is faster and more reproducible than DM. [ABSTRACT FROM AUTHOR]

Purpose: The widespread clinical application of quantitative MRI has been hindered by a lack of reproducibility across sites and vendors. Previous work has attributed this to incorrect B1 mapping or insufficient spoiling conditions. We recently proposed the controlled saturation magnetization transfer (CSMT) framework and hypothesized that the lack of reproducibility can also be attributed to magnetization transfer effects. This work seeks to validate this hypothesis and demonstrate that reproducible multivendor single‐pool relaxometry can be achieved with the CSMT approach. Methods: Three healthy volunteers were scanned on scanners from 3 vendors (GE Healthcare, Philips, Siemens). An extensive set of images necessary for joint T1 and T2 estimation were acquired with (1) each vendor default RF pulses and spoiling conditions; (2) harmonized RF spoiling; and (3) harmonized RF spoiling and CSMT pulses. Different subsets of images were used to generate 6 different T1 and T2 maps for each subject's data from each vendor. Cross‐protocol, cross‐vendor, and test/retest variability were estimated. Results: Harmonized RF spoiling conditions are insufficient to ensure good cross‐vendor reproducibility. Controlled saturation magnetization transfer allows cross‐protocol variability to be reduced from 18.3% to 4.0%. Whole‐brain variability using the same protocol was reduced from a maximum of 19% to 4.5% across sites. Both CSMT and native vendor RF conditions have a reported variability of less than 5% for repeat measures on the same vendor. Conclusion: Magnetization transfer effects are a major contributor to intersite/intrasite variability of T1 and T2 estimation. Controlled saturation magnetization transfer stabilizes these effects, paving the way for the use of single‐pool T1 and T2 as a reliable source for clinical diagnosis across sites. [ABSTRACT FROM AUTHOR]

Purpose: A properly characterized macromolecular (MM) contribution is essential for accurate metabolite quantification in FID‐MRSI. MM information can be included into the fitting model as a single component or parameterized and included over several individual MM resonances, which adds flexibility when pathologic changes are present but is prone to potential overfitting. This study investigates the effects of different MM models on MRSI reproducibility. Methods: Clinically feasible, high‐resolution FID‐MRSI data were collected in ~5 min at 7 Tesla from 10 healthy volunteers and quantified via LCModel (version 6.3) with 3 basis sets, each with a different approach for how the MM signal was handled: averaged measured whole spectrum (full MM), 9 parameterized components (param MM) with soft constraints to avoid overparameterization, or without any MM information included in the fitting prior knowledge. The test–retest reproducibility of MRSI scans was assessed voxel‐wise using metabolite coefficients of variation and intraclass correlation coefficients and compared between the basis sets. Correlations of concentration estimates were investigated for the param MM fitting model. Results: The full MM model provided the most reproducible quantification of total NAA, total Cho, myo‐inositol, and glutamate + glutamine ratios to total Cr (coefficients of variations ≤ 8%, intraclass correlation coefficients ≥ 0.76). Using the param MM model resulted in slightly lower reproducibility (up to +3% higher coefficients of variations, up to −0.1 decreased intraclass correlation coefficients). The quantification of the parameterized macromolecules did not affect quantification of the overlapping metabolites. Conclusion: Clinically feasible FID‐MRSI with an experimentally acquired MM spectrum included in prior knowledge provides highly reproducible quantification for the most common neurometabolites in healthy volunteers. Parameterization of the MM spectrum may be preferred as a compromise between quantification accuracy and reproducibility when the MM content is expected to be pathologically altered. [ABSTRACT FROM AUTHOR]

Purpose: To measure the arterial input function (AIF), an essential component of tracer kinetic analysis, in a population of patients using an optimized dynamic contrast‐enhanced (DCE) imaging sequence and to estimate inter‐ and intrapatient variability. From these data, a representative AIF that may be used for realistic simulation studies can be extracted. Methods: Thirty‐nine female patients were imaged on multiple visits before and during a course of neoadjuvant chemotherapy for breast cancer. A total of 97 T1‐weighted DCE studies were analyzed including bookend estimates of T1 and model‐fitting to each individual AIF. Area under the curve and cardiac output were estimated from each first pass peak, and these data were used to assess inter‐ and intrapatient variability of the AIF. Results: Interpatient variability exceeded intrapatient variability of the AIF. There was no change in cardiac output as a function of MR visit (mean value 5.6 ± 1.1 L/min) but baseline blood T1 increased significantly following the start of chemotherapy (which was accompanied by a decrease in hematocrit). Conclusion: The AIF in an individual patient can be measured reproducibly but the variability of AIFs between patients suggests that use of a population AIF will decrease the precision of tracer kinetic analysis performed in cross‐patient comparison studies. A representative AIF is presented that is typical of the population but retains the characteristics of an individually measured AIF. [ABSTRACT FROM AUTHOR]

Purpose: Parametric imaging methods (e.g., T1 relaxation time mapping) have been shown to be more reproducible across time and vendors than weighted (e.g., T1‐weighted) images. The purpose of this work was to more extensively evaluate the validity of this assertion. Methods: Seven volunteers underwent twice‐repeated acquisitions of variable flip‐angle T1 mapping, including B1+ calibration, on a 3T Philips Achieva and 3T Siemens Trio scanner. Intra‐scanner and inter‐vendor T1 variability were calculated. To determine T1 reproducibility levels in longitudinal settings, or after changing hardware or software, four additional data sets were acquired from two of the participants; one participant was scanned on a different 3T Siemens Trio scanner and another on the same 3T Philips Achieva scanner but after a software upgrade. Results: Intra‐scanner variability of voxel‐wise T1 values was consistent between the two vendors, averaging 0.7/0.7/1.3/1.4% in white matter/cortical gray matter/subcortical gray matter/cerebellum, respectively. We observed, however, a systematic bias between the two vendors of https://doi.org/10.0/7.8/8.6/10.0%, respectively. The T1 bias across two scanners of the same model was greater than intra‐scanner variability, although still only at 1.4/1.0/1.9/2.3%, respectively. A greater bias was identified for data sets acquired before/after software upgrade in white matter/cortical gray matter (3.6/2.7%) whereas variability in subcortical gray matter/cerebellum was comparable (1.7/1.9%). Conclusion: We established intra‐ and inter‐vendor reproducibility levels for a widely used T1 mapping protocol. We anticipate that these results will guide the design of multi‐center studies, particularly those encompassing multiple vendors. Furthermore, this baseline level of reproducibility should be established or surpassed during the piloting phase of such studies. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate the reproducibility and regional variation of parameters obtained from localized 129Xe chemical shift saturation recovery (CSSR) MR spectroscopy in healthy volunteers and patients with chronic obstructive pulmonary disease (COPD) and to compare the results to 129Xe dissolved‐phase MR imaging. Methods: Thirteen healthy volunteers and 10 COPD patients were scanned twice using 129Xe dissolved‐phase imaging, CSSR, and ventilation imaging sequences. A 16‐channel phased‐array coil in combination with the regularized spectral localization achieved by sensitivity heterogeneity (SPLASH) method was used to perform a regional analysis of CSSR data. Lung function and microstructural parameters were obtained using Patz model functions and their reproducibility was assessed. Results: The Patz model alveolar wall thickness parameter shows good reproducibility on a regional basis with a median coefficient of variation of 6.5% in healthy volunteers and 12.4% in COPD patients. Significant regional differences of lung function parameters derived from localized CSSR were found in healthy volunteers and correlations with spirometric indices were found. Conclusion: Localized 129Xe CSSR provides reproducible estimates of alveolar wall thickness and is able to detect regional differences of lung microstructure. [ABSTRACT FROM AUTHOR]

Purpose: To assess the reproducibility of biexponential R2‐relaxometry MRI for estimation of liver iron concentration (LIC) between proprietary and nonproprietary analysis methods. Methods: This single‐center retrospective study, approved by investigational review board and compliant with the Health Insurance Portability and Accountability Act, included 40 liver MRI exams in 38 subjects with suspected or known iron overload. From spin‐echo images of the liver, acquired at 5 different echo times (TE = 6–18 ms), biexponential R2 maps were calculated using 1 proprietary (FerriScan, Resonance Health Ltd., Claremont WA, Australia) and 3 nonproprietary (simulated annealing, nonlinear least squares, dictionary search) analysis methods. Each subject's average liver R2 value was converted to LIC using a previously validated calibration curve. Inter‐method reproducibility for liver R2 and LIC were assessed for linearity using linear regression analysis and absolute agreement using intraclass correlation and Bland‐Altman analysis. For point estimates, 95% confidence intervals were calculated; P values < 0.05 were considered statistically significant. Results: Linearity between the proprietary and nonproprietary methods was excellent across the observed range for R2 (20–312 s−1) and LIC (0.4–52.2 mg/g), with all coefficients of determination (R2) ≥ 0.95. No statistically significant bias was found (slope estimates ∼ 1; intercept estimates ∼ 0; P values > 0.05). Agreement between the 4 methods was excellent for both liver R2 and LIC (intraclass correlations ≥ 0.97). Bland‐Altman 95% limits of agreement in % difference between the proprietary and nonproprietary methods were ≤ 9% and ≤ 16% for R2 and LIC, respectively. Conclusion: Biexponential R2‐relaxometry MRI for LIC estimation is reproducible between proprietary and nonproprietary analysis methods. [ABSTRACT FROM AUTHOR]

Purpose: Cerebral venous oxygenation (Yv) is an important physiological parameter and has potential clinical application in many brain diseases. T2‐relaxation‐under‐spin‐tagging (TRUST) is a commonly used MRI method to measure Yv. Harmonization of this technique across MRI vendors is important for dissemination and multicenter studies of brain oxygenation and metabolism as a disease biomarker. Methods: TRUST pulse sequence components and imaging parameters were carefully matched between two major MRI vendors, Philips and Siemens. Each subject (N = 10) was scanned on both scanners within a 2.5‐h period. On each scanner, the subject was scanned in two sessions to assess intersession reproducibility. A hyperoxia challenge was also included in both sessions and on both scanners to evaluate the sensitivity of the technique to Yv changes. Measured Yv values, confidence interval of Yv estimates ( ε Y v), as well as intrasession and intersession coefficient of variation (CoV) of Yv, were compared between the two scanners. Results: Yv measured on the two vendors were highly compatible and strongly correlated (R2 = 0.957). Yv changes associated with hyperoxia challenge were significant on both scanners (P < 0.001) and were also correlated across scanners (P = 0.007). Intrasession and intersession CoV of measured Yv were less than 3% and showed no difference between scanners. ε Y v were less than 1% on both scanners and showed no difference between scanners when echo times were matched on the two scanners. Conclusion: This work suggests that harmonized TRUST MRI can yield highly compatible Yv measurements across different vendors. Magn Reson Med 80:1125–1131, 2018. © 2018 International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]

Purpose: To develop a fast and robust method for measuring T1 in the whole cervical spinal cord in vivo, and to assess its reproducibility. Methods: A spatially nonselective adiabatic inversion pulse is combined with zonally oblique-magnified multislice echo-planar imaging to produce a reduced field-of-view inversion-recovery echo-planar imaging protocol. Multi- inversion time data are obtained by cycling slice order throughout sequence repetitions. Measurement of T1 is performed using 12 inversion times for a total protocol duration of 7 min. Reproducibility of regional T1 estimates is assessed in a scan-rescan experiment on five heathy subjects. Results: Regional mean (standard deviation) T1 was: 1108.5 (±77.2) ms for left lateral column, 1110.1 (±83.2) ms for right lateral column, 1150.4 (±102.6) ms for dorsal column, and 1136.4 (±90.8) ms for gray matter. Regional T1 estimates showed good correlation between sessions (Pearson correlation coefficient = 0.89 (P value < 0.01); mean difference = 2 ms, 95% confidence interval ± 20 ms); and high reproducibility (intersession coefficient of variation approximately 1% in all the regions considered, intraclass correlation coefficient = 0.88 (P value < 0.01, confidence interval 0.71–0.95)).Conclusions: T1 estimates in the cervical spinal cord are reproducible using inversion-recovery zonally oblique-magnified multislice echo-planar imaging. The short acquisition time and large coverage of this method paves the way for accurate T1 mapping for various spinal cord pathologies. [ABSTRACT FROM AUTHOR]

Purpose To evaluate the reproducibility of indices of lung microstructure and function derived from 129Xe chemical shift saturation recovery (CSSR) spectroscopy in healthy volunteers and patients with chronic obstructive pulmonary disease (COPD), and to study the sensitivity of CSSR-derived parameters to pulse sequence design and lung inflation level. Methods Preliminary data were collected from five volunteers on three occasions, using two implementations of the CSSR sequence. Separately, three volunteers each underwent CSSR at three different lung inflation levels. After analysis of these preliminary data, five COPD patients were scanned on three separate days, and nine age-matched volunteers were scanned three times on one day, to assess reproducibility. Results CSSR-derived alveolar septal thickness (ST) and surface-area-to-volume (S/V) ratio values decreased with lung inflation level ( P < 0.001; P = 0.057, respectively). Intra-subject standard deviations of ST were lower than the previously measured differences between volunteers and subjects with interstitial lung disease. The mean coefficient of variation (CV) values of ST were 3.9 ± 1.9% and 6.0 ± 4.5% in volunteers and COPD patients, respectively, similar to CV values for whole-lung carbon monoxide diffusing capacity. The mean CV of S/V in volunteers and patients was 14.1 ± 8.0% and 18.0 ± 19.3%, respectively. Conclusion 129Xe CSSR presents a reproducible method for estimation of alveolar septal thickness. Magn Reson Med 77:2107-2113, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. [ABSTRACT FROM AUTHOR]

Purpose Poorly characterized macromolecular (MM) and baseline artefacts are known to reduce metabolite quantitation accuracy in 1H MR spectroscopic imaging (MRSI). Increasing echo time (TE) and improvements in MM analysis schemes have both been proposed as strategies to improve metabolite measurement reliability. In this study, the influence of TE and two MM analysis schemes on MRSI reproducibility are investigated. Methods An experimentally acquired baseline was collected using an inversion recovery sequence (TI = 750 ms) and incorporated into the analysis method. Intrasubject reproducibility of MRSI scans, acquired at 3 Tesla, was assessed using metabolite coefficients of variance (COVs) for both experimentally acquired and simulated MM analysis schemes. In addition, the reproducibility of TE = 35 ms, 80 ms, and 144 ms was evaluated. Results TE = 80 ms was the most reproducible for singlet metabolites with COVs < 6% for total N-acetyl-aspartate, total creatine, and total choline; however, moderate multiplet dephasing was observed. Analysis incorporating the experimental baseline achieved higher Glu and Glx reproducibility at TE = 35 ms, and showed improvements over the simulated baseline, with higher efficacy for poorer data. Conclusion Overall, TE = 80 ms yielded the most reproducible singlet metabolite estimates. However, combined use of a short TE sequence and the experimental baseline may be preferred as a compromise between accuracy, multiplet dephasing, and T2 bias on metabolite estimates. Magn Reson Med 77:34-43, 2017. © 2016 The Authors Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. [ABSTRACT FROM AUTHOR]