Search

We aimed to determine the intra-site repeatability and cross-site reproducibility of T1 and T2* relaxation times and quantitative susceptibility (χ) values obtained through quantitative parameter mapping (QPM) at 3 T. This prospective study included three 3-T scanners with the same hardware and software platform at three sites. The brains of twelve healthy volunteers were scanned three times using QPM at three sites. Intra-site repeatability and cross-site reproducibility were evaluated based on voxel-wise and region-of-interest analyses. The within-subject coefficient of variation (wCV), within-subject standard deviation (wSD), linear regression, Bland–Altman plot, and intraclass correlation coefficient (ICC) were used for evaluation. The intra-site repeatability wCV was 11.9 ± 6.86% for T1 and 3.15 ± 0.03% for T2*, and wSD of χ at 3.35 ± 0.10 parts per billion (ppb). Intra-site ICC(1, k) values for T1, T2*, and χ were 0.878–0.904, 0.972–0.976, and 0.966–0.972, respectively, indicating high consistency within the same scanner. Linear regression analysis revealed a strong agreement between measurements from each site and the site-average measurement, with R-squared values ranging from 0.79 to 0.83 for T1, 0.94–0.95 for T2*, and 0.95–0.96 for χ. The cross-site wCV was 13.4 ± 5.47% for T1 and 3.69 ± 2.25% for T2*, and cross-site wSD of χ at 4.08 ± 3.22 ppb. The cross-site ICC(2,1) was 0.707, 0.913, and 0.902 for T1, T2*, and χ, respectively. QPM provides T1, T2*, and χ values with an intra-site repeatability of <12% and cross-site reproducibility of <14%. These findings may contribute to the development of multisite studies. [ABSTRACT FROM AUTHOR]

Objectives: In the latest World Health Organization classification 2021, grade 4 adult diffuse gliomas can be diagnosed with several molecular features even without histological evidence of necrosis or microvascular proliferation. We aimed to explore whole tumor histogram-derived apparent diffusion coefficient (ADC) histogram profiles for differentiating between the presence (Mol-4) and absence (Mol-2/3) of grade 4 molecular features in histologically lower-grade gliomas. Methods: Between June 2019 and October 2022, 184 adult patients with diffuse gliomas underwent MRI. After excluding 121 patients, 18 (median age, 64.5 [range, 37–84 years]) Mol-4 and 45 (median 40 [range, 18–73] years) Mol-2/3 patients with histologically lower-grade gliomas were enrolled. Whole tumor volume-of-interest-derived ADC histogram profiles were calculated and compared between the two groups. Stepwise logistic regression analysis with Akaike's information criterion using the ADC histogram profiles with p values < 0.01 and age at diagnosis was used to identify independent variables for predicting the Mol-4 group. Results: The 90th percentile (p < 0.001), median (p < 0.001), mean (p < 0.001), 10th percentile (p = 0.014), and entropy (p < 0.001) of normalized ADC were lower, and kurtosis (p < 0.001) and skewness (p = 0.046) were higher in the Mol-4 group than in the Mol-2/3 group. Multivariate logistic regression analysis revealed that the entropy of normalized ADC and age at diagnosis were independent predictive parameters for the Mol-4 group with an area under the curve of 0.92. Conclusion: ADC histogram profiles may be promising preoperative imaging biomarkers to predict molecular grade 4 among histologically lower-grade adult diffuse gliomas. Clinical relevance statement: This study highlighted the diagnostic usefulness of ADC histogram profiles to differentiate histologically lower grade adult diffuse gliomas with the presence of molecular grade 4 features and those without. Key Points: • ADC histogram profiles to predict molecular CNS WHO grade 4 status among histologically lower-grade adult diffuse gliomas were evaluated. • Entropy of ADC and age were independent predictive parameters for molecular grade 4 status. • ADC histogram analysis is useful for predicting molecular grade 4 among histologically lower-grade gliomas. [ABSTRACT FROM AUTHOR]

Purpose: There remains no consensus normal-appearing white matter (NAWM) normalization method to compute normalized relative cerebral blood volume (nrCBV) and apparent diffusion coefficient (nADC) in brain tumors. This reader study explored nrCBV and nADC differences using different NAWM normalization methods. Methods: Thirty-five newly diagnosed glioma patients were studied. For each patient, two readers created four NAWM regions of interests: (1) a single plane in the centrum semiovale (CSOp), (2) 3 spheres in the centrum semiovale (CSOs), (3) a single plane in the slice of the tumor center (TUMp), and (4) 3 spheres in the slice of the tumor center (TUMs). Readers repeated NAWM segmentations 1 month later. Differences in nrCBV and nADC of the FLAIR hyperintense tumor, inter-/intra-reader variability, and time to segment NAWM were assessed. As a validation step, the diagnostic performance of each method for IDH-status prediction was evaluated. Results: Both readers obtained significantly different nrCBV (P <.001), nADC (P <.001), and time to segment NAWM (P <.001) between the four normalization methods. nrCBV and nADC were significantly different between CSO and TUM methods, but not between planar and spherical methods in the same NAWM region. Broadly, CSO methods were quicker than TUM methods, and spherical methods were quicker than planar methods. For all normalization techniques, inter-reader reproducibility and intra-reader repeatability were excellent (intraclass correlation coefficient > 0.9), and the IDH-status predictive performance remained similar. Conclusion: The selected NAWM region significantly impacts nrCBV and nADC values. CSO methods, particularly CSOs, may be preferred because of time reduction, similar reader variability, and similar diagnostic performance compared to TUM methods. [ABSTRACT FROM AUTHOR]

Objectives: We aimed to investigate the influence of magnetic resonance fingerprinting (MRF) dictionary design on radiomic features using in vivo human brain scans. Methods: Scan-rescans of three-dimensional MRF and conventional T1-weighted imaging were performed on 21 healthy volunteers (9 males and 12 females; mean age, 41.3 ± 14.6 years; age range, 22–72 years). Five patients with multiple sclerosis (3 males and 2 females; mean age, 41.2 ± 7.3 years; age range, 32–53 years) were also included. MRF data were reconstructed using various dictionaries with different step sizes. First- and second-order radiomic features were extracted from each dataset. Intra-dictionary repeatability and inter-dictionary reproducibility were evaluated using intraclass correlation coefficients (ICCs). Features with ICCs > 0.90 were considered acceptable. Relative changes were calculated to assess inter-dictionary biases. Results: The overall scan-rescan ICCs of MRF-based radiomics ranged from 0.86 to 0.95, depending on dictionary step size. No significant differences were observed in the overall scan-rescan repeatability of MRF-based radiomic features and conventional T1-weighted imaging (p = 1.00). Intra-dictionary repeatability was insensitive to dictionary step size differences. MRF-based radiomic features varied among dictionaries (overall ICC for inter-dictionary reproducibility, 0.62–0.99), especially when step sizes were large. First-order and gray level co-occurrence matrix features were the most reproducible feature classes among different step size dictionaries. T1 map-derived radiomic features provided higher repeatability and reproducibility among dictionaries than those obtained with T2 maps. Conclusion: MRF-based radiomic features are highly repeatable in various dictionary step sizes. Caution is warranted when performing MRF-based radiomics using datasets containing maps generated from different dictionaries. Key Points: • MRF-based radiomic features are highly repeatable in various dictionary step sizes. • Use of different MRF dictionaries may result in variable radiomic features, even when the same MRF acquisition data are used. • Caution is needed when performing radiomic analysis using data reconstructed from different dictionaries. [ABSTRACT FROM AUTHOR]

Simple Summary: Gliomas are known to present with an altered metabolic phenotype that contributes to the abnormal tumor microenvironment detectable on MRI. The aim of this study was to quantify metabolic statuses of glioma using pH- and oxygen-sensitive MRI and associate the measurements with genetic mutation and prognosis. Using the data of 159 adult glioma patients, we revealed that isocitrate dehydrogenase mutation, 1p/19q co-deletion, and epidermal growth factor receptor amplification statuses were associated with the MRI measurements revealing tissue acidosis and hypoxia, and these measurements were also associated with progression-free survival and overall survival, independent of patient age, treatment status, and isocitrate dehydrogenase mutation status. In conclusion, the pH- and oxygen-sensitive MRI is clinically feasible and potentially valuable for distinguishing glioma genotypes and provides additional prognostic value to clinical practice. Characterization of hypoxia and tissue acidosis could advance the understanding of glioma biology and improve patient management. In this study, we evaluated the ability of a pH- and oxygen-sensitive magnetic resonance imaging (MRI) technique to differentiate glioma genotypes, including isocitrate dehydrogenase (IDH) mutation, 1p/19q co-deletion, and epidermal growth factor receptor (EGFR) amplification, and investigated its prognostic value. A total of 159 adult glioma patients were scanned with pH- and oxygen-sensitive MRI at 3T. We quantified the pH-sensitive measure of magnetization transfer ratio asymmetry (MTRasym) and oxygen-sensitive measure of R2' within the tumor region-of-interest. IDH mutant gliomas showed significantly lower MTRasym × R2' (p < 0.001), which differentiated IDH mutation status with sensitivity and specificity of 90.0% and 71.9%. Within IDH mutants, 1p/19q codeletion was associated with lower tumor acidity (p < 0.0001, sensitivity 76.9%, specificity 91.3%), while IDH wild-type, EGFR-amplified gliomas were more hypoxic (R2' p = 0.024, sensitivity 66.7%, specificity 76.9%). Both R2' and MTRasym × R2' were significantly associated with patient overall survival (R2': p = 0.045; MTRasym × R2': p = 0.002) and progression-free survival (R2': p = 0.010; MTRasym × R2': p < 0.0001), independent of patient age, treatment status, and IDH status. The pH- and oxygen-sensitive MRI is a clinically feasible and potentially valuable imaging technique for distinguishing glioma subtypes and providing additional prognostic value to clinical practice. [ABSTRACT FROM AUTHOR]

Purpose: We hypothesize that myelin is more susceptible to damage over time than axons. We investigated the association between the estimated duration from the onset of multiple sclerosis (MS) plaques and myelin- and axon-related quantitative synthetic magnetic resonance imaging (SyMRI) and neurite orientation dispersion and density imaging (NODDI) metrics. Methods: We analyzed 31 patients with MS with 73 newly appeared plaques. Simple linear regression analysis was performed to assess the association between the estimated duration from the onset of plaques and quantitative MRI metrics. These metrics included the myelin volume fraction (MVF), axon volume fraction, and g-ratio in plaque and normal-appearing white matter. Results: MS plaques with a longer estimated duration from onset were significantly correlated with a lower MVF (slope = − 0.0070, R2 = 0.0970), higher g-ratio (slope = 0.0078, R2 = 0.0842) (all P values < 0.05). Conclusion: These results suggested that myelin in plaques undergoes continuous damage, more so than axons. Myelin imaging with SyMRI and NODDI may be useful for the quantitative assessment of temporal changes in MS plaques. [ABSTRACT FROM AUTHOR]

This study aimed to differentiate isocitrate dehydrogenase (IDH) mutation status with the voxel-wise clustering method of multiparametric magnetic resonance imaging (MRI) and to discover biological underpinnings of the clusters. A total of 69 patients with treatment-naïve diffuse glioma were scanned with pH-sensitive amine chemical exchange saturation transfer MRI, diffusion-weighted imaging, fluid-attenuated inversion recovery, and contrast-enhanced T1-weighted imaging at 3 T. An unsupervised two-level clustering approach was used for feature extraction from acquired images. The logarithmic ratio of the labels in each class within tumor regions was applied to a support vector machine to differentiate IDH status. The highest performance to predict IDH mutation status was found for 10-class clustering, with a mean area under the curve, accuracy, sensitivity, and specificity of 0.94, 0.91, 0.90, and 0.91, respectively. Targeted biopsies revealed that the tissues with labels 7–10 showed high expression levels of hypoxia-inducible factor 1-alpha, glucose transporter 3, and hexokinase 2, which are typical of IDH wild-type glioma, whereas those with labels 1 showed low expression of these proteins. In conclusion, A machine learning model successfully predicted the IDH mutation status of gliomas, and the resulting clusters properly reflected the metabolic status of the tumors. [ABSTRACT FROM AUTHOR]

Objectives: To evaluate the relationship between abnormal findings on abdomino-pelvic CT and adverse events in oncologic patients treated with lenvatinib, and their relationship with treatment planning. Methods: This single institutional retrospective study included 58 patients with unresectable hepatocellular carcinoma or unresectable thyroid carcinoma (mean age ± standard deviation 69.6 ± 10.0 years; range 39–84 years; 48 men) who underwent CT between October 2016 and July 2020. Two radiologists who were blinded to clinical information including the presence or absence of diarrhea evaluated the imaging findings, including the presence/absence of enteritis in each intestinal segment. Gastrointestinal adverse events (diarrhea, decreased appetite, nausea, and vomiting) and other drug-induced adverse events requiring treatment or follow-up during lenvatinib treatment were also investigated. The frequency of these adverse events was compared between the patients with and without enteritis using Fisher's exact test or the Mann–Whitney U test. Results: Enteritis was found on CT in the majority (33/58 [56.9%]) of the patients, and most of them (25/33 [75.8%]) showed duodenojejunitis. The frequency of gastrointestinal adverse events (28/33 [84.8%] vs. 13/25 [56.0%], p = 0.009), diarrhea (20/33 [60.6%] vs. 3/25 [12.0%], p < 0.001), and drug interruptions (25/33 [75.8%] vs. 10/25 [40.0%], p = 0.008) and the number of other adverse events (3.9 ± 1.7 vs. 2.3 ± 1.3, p < 0.001) were significantly higher in the patients with enteritis on CT than in those without. Conclusions: Lenvatinib-induced enteritis frequently involved the duodenum and jejunum and was related to a significantly higher frequency of treatment interruptions and gastrointestinal adverse events. [ABSTRACT FROM AUTHOR]

Recently, three-dimensional (3D) quantitative synthetic magnetic resonance imaging (MRI), which quantifies tissue properties and creates multiple contrast-weighted images, has been enabled by 3D-quantification using an interleaved Look-Locker acquisition sequence with a T2 preparation pulse (3D-QALAS). However, the relatively long scan time has hindered its introduction into clinical practice. A hybrid of compressed sensing and parallel imaging (Compressed sensing-sensitivity encoding: CS-SENSE) can accelerate 3D-QALAS; however, whether CS-SENSE affects the quantitative values acquired by 3D-QALAS remains unexplored. Therefore, this study aimed to examine the effects of reduction factors of CS-SENSE (R CSS) on the quantitative values derived from 3D-QALAS, by assessing the signal-to-noise ratio (SNR) of the quantitative maps, as well as accuracy (linearity and bias) and repeatability of measured quantitative values. In this study, the ISMRM/NIST standardized phantom was scanned on a 1.5-T MRI scanner with 3D-QALAS using R CSS in the range between 1 and 3, with intervals of 0.2, and between 3 and 10 with intervals of 0.5. The T1, T2, and proton density (PD) values were calculated from the imaging data. For each quantitative value, the SNR, the coefficient of determination (R2) of a linear regression model, the error rate, and the within-subject coefficient of variation (wCV) were calculated for each R CSS and compared. Within the clinically-relevant dynamic range of the brain of T1 and T2 (T1: 200–1400 ms; T2; 50–400 ms) and PD value of 15–100% calculated from 3D-QALAS, the effects of R CSS on quantitative values was small between 1 and 2.8, with SNR ≧ 10, R2 ≧ 0.9, error rate ≦ 10%, and wCV ≦ 10%, except for T2 values of 186.1 and 258.4 ms. CS-SENSE enabled the reduction of the scan time of 3D-QALAS by 63.5% (R CSS = 2.8) while maintaining the SNR of quantitative maps and accuracy and repeatability of the quantitative values. • The relatively long scan time of 3D-QALAS has hindered its use in clinical practice. • This study examines the effect of a hybrid of compressed sensing and parallel imaging on 3D-QALAS quantitative values. • A hybrid of compressed sensing and parallel imaging may reduce the imaging time by 63.5% and maintain quality. [ABSTRACT FROM AUTHOR]

Co-deletion of 1p/19q is a hallmark of oligodendroglioma and predicts better survival. However, little is understood about its metabolic characteristics. In this study, we aimed to explore the extracellular acidity of WHO grade II and III gliomas associated with 1p/19q co-deletion. We included 76 glioma patients who received amine chemical exchange saturation transfer (CEST) imaging at 3 T. Magnetic transfer ratio asymmetry (MTRasym) at 3.0 ppm was used as the pH-sensitive CEST biomarker, with higher MTRasym indicating lower pH. To control for the confounder factors, T2 relaxometry and l-6-18F-fluoro-3,4-dihydroxyphenylalnine (18F-FDOPA) PET data were collected in a subset of patients. We found a significantly lower MTRasym in 1p/19q co-deleted gliomas (co-deleted, 1.17% ± 0.32%; non-co-deleted, 1.72% ± 0.41%, P = 1.13 × 10−7), while FDOPA (P = 0.92) and T2 (P = 0.61) were not significantly affected. Receiver operating characteristic analysis confirmed that MTRasym could discriminate co-deletion status with an area under the curve of 0.85. In analysis of covariance, 1p/19q co-deletion status was the only significant contributor to the variability in MTRasym when controlling for age and FDOPA (P = 2.91 × 10−3) or T2 (P = 8.03 × 10−6). In conclusion, 1p/19q co-deleted gliomas were less acidic, which may be related to better prognosis. Amine CEST-MRI may serve as a non-invasive biomarker for identifying 1p/19q co-deletion status. [ABSTRACT FROM AUTHOR]

Previous methods for the quantification of brain tissue properties by magnetic resonance imaging were mainly based on two-dimensional acquisitions and were thus limited to a relatively low resolution in the slice direction compared to three-dimensional (3D) acquisitions. The 3D-quantification using an interleaved Look–Locker acquisition sequence with a T2 preparation pulse (3D-QALAS) sequence may allow for simultaneous acquisition of relaxometry parameters in high spatial resolution. To evaluate bias, linearity, and day-to-day repeatability of relaxometry parameters, as well as tissue fraction maps, acquired with 3D-QALAS. Scan–rescan test of the 3D-QALAS sequence was performed on a 1.5-T scanner with the International Society for Magnetic Resonance in Medicine/National institute of Standards and Technology system phantom and 10 healthy volunteers (7 male, 3 female; mean age, 23.2 ± 3.6 years). Simple linear regression analysis, Bland–Altman plots, and intrasubject coefficients of variation (CV) were used to assess the reliability of 3D-QALAS sequence-derived parameters. The T1, T2, proton density (PD), and myelin volume fraction (MVF) of in vivo brain regions were compared with values obtained using the multidynamic multi-echo sequence. In the phantom study, the T1, T2, and PD values measured by 3D-QALAS showed strong linearity with the reference values (R2 = 0.998, 0.998, and 0.960 for T1, T2, and PD, respectively) and high repeatability (mean CV of 1.2%, 2.8%, and 2.9% for T1, T2, and PD, respectively). The T1, T2, PD, and MVF values of in vivo brain regions obtained with 3D-QALAS were highly consistent within subjects, with mean intrasubject CVs of 0.5%, 0.5%, 0.4%, and 1.6% for the T1, T2, PD, and MVF values, respectively. 3D-QALAS enables reliable measurement of T1, T2, PD, and MVF values of the whole brain in high spatial resolution across a clinically-relevant dynamic range. [ABSTRACT FROM AUTHOR]

Purpose: Accelerated myelination in the affected hemisphere has been demonstrated previously in patients with Sturge-Weber syndrome (SWS). This prospective study investigated myelin-related changes in patients with unilateral SWS using synthetic quantitative magnetic resonance imaging (qMRI). Methods: Fourteen children with unilateral SWS were categorized according to age, i.e., ≤ 2 years (group A, n = 5, mean age 1.1 years, 3 males) and > 2 years (group B, n = 9, mean age 3.9 years, 4 males). All children underwent two-dimensional synthetic qMRI. The myelin volume in the cerebral hemisphere and white matter (WM) myelin volume fraction (MVF), proton density (PD), R1 and R2 relaxation rates ipsilateral to the leptomeningeal enhancement, and/or a port-wine birthmark were compared with the corresponding values in the contralateral hemisphere. Results: In group A, 3 patients had a higher myelin volume in the ipsilateral hemisphere and a higher MVF, R1, and R2 and lower PD in the ipsilateral WM than on the contralateral side; the findings were the opposite in the remaining two patients. All patients in group B had a significantly lower myelin volume in the ipsilateral hemisphere (P < 0.05) and a lower MVF and R1 and higher PD in the ipsilateral WM than on the contralateral side (P < 0.0125). Conclusion: Higher estimated myelin was observed on the ipsilateral side in some patients aged ≤ 2 years and lower myelin on the ipsilateral side in all older patients. Synthetic qMRI might be useful for showing myelin-related abnormalities in SWS. [ABSTRACT FROM AUTHOR]

Purpose: Diffusion-weighted imaging (DWI) is a useful tool for early detection of cerebral infarction. However, recent reports have demonstrated that DWI with short effective diffusion time (∆eff) can obscure visualization of infarction.Methods: We report three cases, including four acute-to-subacute infarctions, that demonstrated reduced visualization of the infarctions on DWI with shorter ∆eff.Results: DWI was performed with different ∆eff: short and long ∆eff, using oscillating gradient spin-echo (OGSE) DWI, and intermediate ∆eff, using pulsed gradient spin-echo (PGSE) DWI. Different apparent diffusion coefficient values (due to different ∆eff) were also observed; these were considered to be the underlying causes of the under-evaluation of infarctions on DWI.Conclusion: The DWI with shorter ∆eff may obscure infarction. High-performance magnetic resonance imaging scanners with higher maximal gradient strength (Gmax) can perform DWI with shorter ∆eff than scanners with lower Gmax. Therefore, the appropriate ∆eff should be set for the detection of restricted diffusion. [ABSTRACT FROM AUTHOR]

To develop a rigid real-time prospective motion-corrected multiparametric mapping technique and to test the performance of quantitative estimates. Motion tracking and correction were performed by integrating single-shot spiral navigators into a multiparametric imaging technique, three-dimensional quantification using an interleaved Look-Locker acquisition sequence with a T2 preparation pulse (3D-QALAS). The spiral navigator was optimized, and quantitative measurements were validated using a standard system phantom. The effect of motion correction on whole-brain T1 and T2 mapping under different types of head motion during the scan was evaluated in 10 healthy volunteers. Finally, six patients with Parkinson's disease, which is known to be associated with a high prevalence of motion artifacts, were scanned to evaluate the effectiveness of our method in the real world. The phantom study demonstrated that the proposed motion correction method did not introduce quantitative bias. Improved parametric map quality and repeatability were shown in volunteer experiments with both in-plane and through-plane motions, comparable to the no-motion ground truth. In real-life validation in patients, the approach showed improved parametric map quality compared to images obtained without motion correction. Real-time prospective motion-corrected multiparametric relaxometry based on 3D-QALAS provided robust and repeatable whole-brain multiparametric mapping. [ABSTRACT FROM AUTHOR]

Despite differences in the pathogenesis and treatment of multiple sclerosis (MS) and neuromyelitis optica spectrum disorders (NMOSD), it remains difficult to distinguish them. In this study, we aimed to discriminate between MS and NMOSD using diffusion tensor imaging (DTI), free water (FW) imaging, and neurite orientation dispersion and density imaging (NODDI). Thirty patients with relapsing-remitting (RR) MS, 18 NMOSD patients with positive anti-aquaporin-4 immunoglobulin G seroreactivity, and 20 age- and sex- matched currently healthy subjects underwent MRI. The differences in the DTI (fractional anisotropy [FA], axial diffusivity [AD], mean diffusivity [MD], and radial diffusivity [RD]), FW and FW-corrected DTI, and NODDI indices between the three groups were evaluated using tract-based spatial statistics (TBSS) and region-of-interest (ROI) analyses. The ROI analysis of lesions indicated that the RRMS group had significantly higher AD, MD, RD, ISO and FW-corrected AD, and MD; and lower intracellular volume fraction (ICVF) than the NMOSD group. TBSS analysis showed increased water content in RRMS patients compared to NMOSD patients. Compared with healthy controls (HCs) using TBSS and ROI analysis, the changes in FW imaging indices were more limited than those of in DTI in RRMS patients. FW imaging and NODDI were useful for identifying the etiology of neurodegeneration- and neuroinflammation-related microstructural changes in RRMS and NMOSD patients. • We evaluated MS and NMOSD using DTI, FW imaging and NODDI. • RRMS group had significantly higher diffusivity in lesions. • RRMS group had significantly lower intracellular volume fraction in lesions. • TBSS analysis showed increased water content in RRMS group. • These results may reflect microstructural changes in MS and NMOSD. [ABSTRACT FROM AUTHOR]

Background: Voxel-based morphometry (VBM) using magnetic resonance imaging (MR) has been used to estimate cortical atrophy associated with various diseases. However, there are mis-segmentations of segmented gray matter image in VBM. Purpose: To study a twofold evaluation of single- and multi-channel segmentation using synthetic MR images: (1) mis-segmentation of segmented gray matter images in transverse and cavernous sinuses; and (2) accuracy and repeatability of segmented gray matter images. Material and Methods: A total of 13 healthy individuals were scanned with 3D quantification using an interleaved Look–Locker acquisition sequence with a T2 preparation pulse (3D-QALAS) sequence on a 1.5-T scanner. Three of the 13 healthy participants were scanned five consecutive times for evaluation of repeatability. We used SyMRI software to create images with three contrasts: T1-weighted (T1W), T2-weighted (T2W), and proton density-weighted (PDW) images. Manual regions of interest (ROI) on T1W imaging were individually set as the gold standard in the transverse sinus, cavernous sinus, and putamen. Single-channel (T1W) and multi-channel (T1W + T2W, T1W + PDW, and T1W + T2W + PDW imaging) segmentations were performed with statistical parametric mapping 12 software. Results: We found that mis-segmentations in both the transverse and cavernous sinuses were large in single-channel segmentation compared with multi-channel segmentations. Furthermore, the accuracy of segmented gray matter images in the putamen was high in both multi-channel T1W + PDW and T1W + T2W + PDW segmentations compared with other segmentations. Finally, the highest repeatability of left putamen volumetry was found with multi-channel segmentation T1WI + PDWI. Conclusion: Multi-channel segmentation with T1WI + PDWI provides good results for VBM compared with single-channel and other multi-channel segmentations. [ABSTRACT FROM AUTHOR]

Evaluation of myelin by magnetic resonance imaging (MRI) is a difficult challenge, but holds promise in demyelinating diseases, such as multiple sclerosis (MS). Although multiple techniques have been developed, no gold standard has been established. This study aims to evaluate the correlation between synthetic MRI myelin volume fraction (SyMRIMVF) and myelin fraction estimated by other techniques, i.e., magnetization transfer saturation (MTsat), T1-weighted images divided by T2-weighted images (T1w/T2w), and radial diffusivity (RD) in patients with MS. We also compared the sensitivities of these techniques for detecting MS-related myelin damage. SyMRIMVF, MTsat, T1w/T2w, and RD were averaged on plaque, periplaque white matter, and normal-appearing white matter (NAWM). Pairwise correlation was calculated using Spearman's correlation analysis. For all segmented regions, strong correlations were found between SyMRIMVF and T1w/T2w (Rho = 0.89), MTsat (Rho = 0.82), or RD (Rho = −0.75). For each technique, the average estimated myelin differed significantly among regions, but the percentage change of NAWM from both periplaque white matter and plaque were highest in SyMRIMVF. SyMRIMVF might be suitable for myelin evaluation in MS patients, with relevant results as compared to other well-studied techniques. Moreover, it presented better sensitivity for the detection of the difference between plaque or periplaque white matter and NAWM. [ABSTRACT FROM AUTHOR]

Background and Objectives: Integrating large language models (LLMs) such as GPT-4 Turbo into diagnostic imaging faces a significant challenge, with current misdiagnosis rates ranging from 30–50%. This study evaluates how prompt engineering and confidence thresholds can improve diagnostic accuracy in neuroradiology. Methods: We analyze 751 neuroradiology cases from the American Journal of Neuroradiology using GPT-4 Turbo with customized prompts to improve diagnostic precision. Results: Initially, GPT-4 Turbo achieved a baseline diagnostic accuracy of 55.1%. By reformatting responses to list five diagnostic candidates and applying a 90% confidence threshold, the highest precision of the diagnosis increased to 72.9%, with the candidate list providing the correct diagnosis at 85.9%, reducing the misdiagnosis rate to 14.1%. However, this threshold reduced the number of cases that responded. Conclusions: Strategic prompt engineering and high confidence thresholds significantly reduce misdiagnoses and improve the precision of the LLM diagnostic in neuroradiology. More research is needed to optimize these approaches for broader clinical implementation, balancing accuracy and utility. [ABSTRACT FROM AUTHOR]

Purpose: The central sulcus is an important landmark in the brain. This study aimed to investigate the distinctive signal of the paracentral lobule (PL) on T1-weighted images (T1WIs; the white PL sign) and evaluate its usefulness as a new method of identifying the central sulcus. Methods: T1WIs of the brain of 96 participants (age, 58.9 ± 17.9 years; range, 8–87 years) scanned at 3-T MR system were retrospectively reviewed. First, we qualitatively analyzed the signal of the cortex of the PL by comparing it with that of the ipsilateral superior frontal gyrus on a 4-point grading score. Second, we compared the cortical signal intensity and gray/white-matter contrast between the PL and superior frontal gyrus. Third, we evaluated the usefulness of the PL signal for identifying the central sulcus. Results: The PL cortex was either mildly hyperintense (grade 2) or definitely hyperintense (grade 3) in comparison with that of superior frontal cortex in all participants. The signal intensity of the PL cortex was significantly higher than that of the superior frontal cortex (p < 0.001), whereas the gray/white-matter contrast of the PL was weaker than that of the superior frontal gyrus (p < 0.001). The central sulci were identified with 94.3% accuracy (181/192) using the new method. Conclusion: The white PL sign may be helpful in identifying the central sulcus, and this approach can be recognized as a new method for identification of the central sulcus. [ABSTRACT FROM AUTHOR]

Extensive gray matter (GM) involvement has been demonstrated in multiple sclerosis (MS) patients. This study was aimed to identify GM alterations in relapsing-remitting MS (RRMS) patients using synthetic quantitative MRI (qMRI). We assessed myelin volume fraction (MVF) in each voxel on the basis of R1 and R2 relaxation rates and proton density in 14 early and 28 late (disease duration ≤5 and >5 years, respectively) RRMS patients, and 15 healthy controls (HCs). The MVF and myelin volumes of GM (GM-MyVol) were compared between groups using GM-based spatial statistics (GBSS) and the Kruskal-Wallis test, respectively. Correlations between MVF or GM-MyVol and disease duration or expanded disability status scale were also evaluated. RRMS patients showed a lower MVF than HCs, predominantly in the limbic and para-limbic areas, with more extensive areas noted in late RRMS patients. Late-RRMS patients had the smallest GM-MyVol (20.44 mL; early RRMS, 22.77 mL; HCs, 23.36 mL). Furthermore, the GM-MyVol in the RRMS group was inversely correlated with disease duration (r = −0.43, p = 0.005). In conclusion, the MVF and MyVol obtained by synthetic qMRI can be used to evaluate GM differences in RRMS patients. [ABSTRACT FROM AUTHOR]

Purpose: Immune checkpoint inhibitors promote the antitumor activity of T cells; however, there is a risk of side effects. The aim of this study was to characterize the computed tomography (CT) findings of one such side effect, anti-programmed cell death-1 antibody-related enterocolitis (αPD-1-EC). Methods: This single-institution retrospective study included 21 patients with αPD-1-EC who underwent CT between January 2015 and April 2020. Two board-certified radiologists independently evaluated the CT findings, including the pattern of intestinal wall enhancement, maximum bowel wall thickness, maximum appendiceal diameter, and involvement of enterocolitis in each intestinal segment. Symptoms and their severity were also investigated. Results: Pancolitis and skip lesions involving both the rectosigmoid colon and the cecum were found in 9 patients each (42.9%). The rectum was the most frequently involved lesion (18/21, 85.7%), and appendiceal involvement was found in 11 patients (52.4%). The most frequent wall enhancement pattern was the gray pattern (i.e., mild homogeneous enhancement of the thickened bowel wall). The mean maximum diameter of the involved appendix was 9.6 ± 4.5 mm (range 4.5–18 mm). Frequent symptoms included diarrhea (21/21), fever (8/21), and abdominal pain (7/21). Other concomitant immune-related adverse events were found in 6 patients. Conclusions: Pancolitis, skip lesions, and appendiceal involvement were frequent in patients with αPD-1-EC. When combining these characteristic findings with other clinical findings, such as low-grade diarrhea, other concomitant immune-related adverse events, and anti-PD-1 therapy administration, CT may be a useful diagnostic tool for αPD-1-EC. [ABSTRACT FROM AUTHOR]

Objective: To determine the feasibility and biologic correlations of dynamic susceptibility contrast (DSC), dynamic contrast enhanced (DCE), and quantitative maps derived from contrast leakage effects obtained simultaneously in gliomas using dynamic spin-and-gradient-echo echoplanar imaging (dynamic SAGE-EPI) during a single contrast injection. Materials and methods: Thirty-eight patients with enhancing brain gliomas were prospectively imaged with dynamic SAGE-EPI, which was processed to compute traditional DSC metrics (normalized relative cerebral blood flow [nrCBV], percentage of signal recovery [PSR]), DCE metrics (volume transfer constant [Ktrans], extravascular compartment [ve]), and leakage effect metrics: ΔR2,ss* (reflecting T2*-leakage effects), ΔR1,ss (reflecting T1-leakage effects), and the transverse relaxivity at tracer equilibrium (TRATE, reflecting the balance between ΔR2,ss* and ΔR1,ss). These metrics were compared between patient subgroups (treatment-naïve [TN] vs recurrent [R]) and biological features (IDH status, Ki67 expression). Results: In IDH wild-type gliomas (IDHwt—i.e., glioblastomas), previous exposure to treatment determined lower TRATE (p = 0.002), as well as higher PSR (p = 0.006), Ktrans (p = 0.17), ΔR1,ss (p = 0.035), ve (p = 0.006), and ADC (p = 0.016). In IDH-mutant gliomas (IDHm), previous treatment determined higher Ktrans and ΔR1,ss (p = 0.026). In TN-gliomas, dynamic SAGE-EPI metrics tended to be influenced by IDH status (p ranging 0.09–0.14). TRATE values above 142 mM−1s−1 were exclusively seen in TN-IDHwt, and, in TN-gliomas, this cutoff had 89% sensitivity and 80% specificity as a predictor of Ki67 > 10%. Conclusions: Dynamic SAGE-EPI enables simultaneous quantification of brain tumor perfusion and permeability, as well as mapping of novel metrics related to cytoarchitecture (TRATE) and blood–brain barrier disruption (ΔR1,ss), with a single contrast injection. Clinical relevance statement: Simultaneous DSC and DCE analysis with dynamic SAGE-EPI reduces scanning time and contrast dose, respectively alleviating concerns about imaging protocol length and gadolinium adverse effects and accumulation, while providing novel leakage effect metrics reflecting blood–brain barrier disruption and tumor tissue cytoarchitecture. Key Points: • Traditionally, perfusion and permeability imaging for brain tumors requires two separate contrast injections and acquisitions. • Dynamic spin-and-gradient-echo echoplanar imaging enables simultaneous perfusion and permeability imaging. • Dynamic spin-and-gradient-echo echoplanar imaging provides new image contrasts reflecting blood–brain barrier disruption and cytoarchitecture characteristics. [ABSTRACT FROM AUTHOR]

Purpose: Epidermal growth factor receptor (EGFR) amplification promotes gliomagenesis and is linked to lack of oxygen within the tumor microenvironment. Using hypoxia-sensitive spin-and-gradient echo echo-planar imaging and perfusion MRI, we investigated the influence of EGFR amplification on tissue oxygen availability and utilization in human gliomas. Methods: This study included 72 histologically confirmed EGFR-amplified and non-amplified glioma patients. Reversible transverse relaxation rate (R2′), relative cerebral blood volume (rCBV), and relative oxygen extraction fraction (rOEF) were calculated for the contrast-enhancing and non-enhancing tumor regions. Using Student t test or Wilcoxon rank-sum test, median R2′, rCBV, and rOEF were compared between EGFR-amplified and non-amplified gliomas. ROC analysis was performed to assess the ability of imaging characteristics to discriminate EGFR amplification status. Overall survival (OS) was determined using univariate and multivariate cox models. Kaplan-Meier survival curves were plotted and compared using the log-rank test. Results: EGFR amplified gliomas exhibited significantly higher median R2′ and rOEF than non-amplified gliomas. ROC analysis suggested that R2′ (AUC = 0.7190; P = 0.0048) and rOEF (AUC = 0.6959; P = 0.0156) could separate EGFR status. Patients with EGFR-amplified gliomas had a significantly shorter OS than non-amplified patients. Univariate cox regression analysis determined both R2′ and rOEF significantly influence OS. No significant difference was observed in rCBV between patient cohorts nor was rCBV found to be an effective differentiator of EGFR status. Conclusion: Imaging of tumor oxygen characteristics revealed EGFR-amplified gliomas to be more hypoxic and contribute to shorter patient survival than EGFR non-amplified gliomas. [ABSTRACT FROM AUTHOR]

Purpose: Synthetic MRI (SyMRI) enables automatic brain tissue and myelin volumetry based on the quantification of R1 and R2 relaxation rates and proton density. This study aimed to determine the validity of SyMRI brain tissue and myelin volumetry using various in-plane resolutions at 3T in patients with multiple sclerosis (MS). Methods: We scanned 19 MS patients and 10 healthy age- and gender-matched controls using a 3T MR scanner with in-plane resolutions of 0.8, 1.8, and 3.6 mm. The acquisition times were 5 min 8 s, 2 min 52 s, and 2 min 1 s, respectively. White matter (WM), gray matter (GM), cerebrospinal fluid (CSF), and myelin and non-WM/GM/CSF (NoN) volumes; brain parenchymal volume (BPV); and intracranial volume (ICV) were compared between different in-plane resolutions. These parameters were also compared between both groups, after ICV normalization. Results: No significant differences in measured volumes were noted between the 0.8 and 1.8 mm in-plane resolutions, except in NoN and CSF for healthy controls and NoN for MS patients. Meanwhile, significant volumetric differences were noted in most brain tissues when compared between the 3.6 and 0.8 or 1.8 mm resolution for both healthy controls and MS patients. The normalized WM volume, myelin volume, and BPV showed significant differences between controls and MS patients at in-plane resolutions of 0.8 and 1.8 mm. Conclusions: SyMRI brain tissue and myelin volumetry with in-plane resolution as low as 1.8 mm can be useful in the evaluation of MS with a short acquisition time of < 3 min. [ABSTRACT FROM AUTHOR]

Background Synthetic magnetic resonance imaging (MRI), a technique that enables creation of various contrast-weighted images from a single MRI quantification scan, is a useful clinical tool. However, there are currently no reports examining the use of contrast-enhanced synthetic MRI for detecting brain metastases. Purpose To assess whether contrast-enhanced synthetic MRI is suitable for detecting brain metastases. Material and Methods Ten patients with a combined total of 167 brain metastases who underwent quantitative MRI and conventional T1-weighted inversion recovery fast spin-echo (conventional T1IR) MRI before and after administration of a contrast agent were included in the study. Synthetic T1IR and T1-weighted (synthetic T1W) images were produced after parameter quantification. Lesion-to-white matter contrast and contrast-to-noise ratio were calculated for each image. The number of visible lesions in each image was determined by two neuroradiologists. Results The mean lesion-to-white matter contrast and mean contrast-to-noise ratio of the synthetic T1IR images were significantly higher than those of the synthetic T1W (P < 0.001 and P < 0.001, respectively) and conventional T1IR (P = 0.04 and P = 0.002, respectively) images. Totals of 130 and 124 metastases were detected in the synthetic T1IR images by the first and second radiologists, respectively. The corresponding numbers were 91 and 85 in the synthetic T1W images and 119 and 119 in the conventional T1IR images. Statistical significance was not found among detected numbers of lesions. Conclusion Synthetic T1IR imaging created better contrast compared with synthetic T1W or conventional T1IR imaging. The ability to detect brain metastases was comparable among these imaging. [ABSTRACT FROM AUTHOR]

Background: Patients with Parkinson's disease (PD) carrying GBA gene mutations (GBA‐PD) have a more aggressive disease course than those with idiopathic PD (iPD). Objective: The objective of this study was to investigate fiber‐specific white matter (WM) differences in nonmedicated patients with early‐stage GBA‐PD and iPD using fixel‐based analysis, a novel technique to assess tract‐specific WM microstructural and macrostructural features comprehensively. Methods: Fixel‐based metrics, including microstructural fiber density (FD), macrostructural fiber‐bundle cross section (FC), and a combination of FD and FC (FDC), were compared among 30 healthy control subjects, 16 patients with GBA‐PD, and 35 patients with iPD. Associations between FDC and clinical evaluations were also explored using multiple linear regression analyses. Results: Patients with GBA‐PD showed significantly lower FD in the fornix and superior longitudinal fasciculus than healthy control subjects, and lower FC in the corticospinal tract (CST) and lower FDC in the CST, middle cerebellar peduncle, and striatal‐thalamo‐cortical pathways than patients with iPD. Contrarily, patients with iPD showed significantly higher FC and FDC in the CST and striatal‐thalamo‐cortical pathways than healthy control subjects. In addition, lower FDC in patients with GBA‐PD was associated with reduced glucocerebrosidase enzyme activity, lower cerebrospinal fluid total α‐synuclein levels, lower Montreal Cognitive Assessment scores, lower striatal binding ratio, and higher Unified Parkinson's Disease Rating Scale Part III scores. Conclusions: We report reduced fiber‐specific WM density and bundle cross‐sectional size in patients with GBA‐PD, suggesting neurodegeneration linked to glucocerebrosidase deficiency, α‐synuclein accumulation, and poorer cognition and motor functions. Conversely, patients with iPD showed increased fiber bundle size, likely because of WM reorganization. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [ABSTRACT FROM AUTHOR]

Purpose Evaluate the effect of vaginal delivery on pelvic organ positions and vaginal cross-sectional areas. Methods MRI of 119 premenopausal women were grouped according to the number of deliveries. The distances from the three 3-reference points (bladder, uterus, and rectum) to two 2-lines (pubococcygeal-line (PCL) and midpubic-line (MPL)), length of H- and M-lines and vaginal cross-sectional area were compared between the groups. Results With increasing parity, distance from the rectum to PCL tended to increase (nullipara vs. bipara; p < 0.01). Vaginal cross-sectional area was larger in bipara and tripara than in nullipara ( p < 0.01). Conclusions Rectal position is more caudally located and vaginal cross-sectional area is larger in bipara than in nullipara. [ABSTRACT FROM AUTHOR]

Oscillating gradient spin-echo (OGSE) sequences provide access to short diffusion times and may provide insight into micro-scale internal structures of pathologic lesions based on an analysis of changes in diffusivity with differing diffusion times. We hypothesized that changes in diffusivity acquired with a shorter diffusion time may permit elucidation of properties related to the internal structure of extra-axial brain tumors. This study aimed to investigate the utility of changes in diffusivity between short and long diffusion times for characterizing extra-axial brain tumors. In total, 12 patients with meningothelial meningiomas, 13 patients with acoustic neuromas, and 11 patients with pituitary adenomas were scanned with a 3 T magnetic resonance imaging (MRI) scanner with diffusion-weighted imaging (DWI) using OGSE and pulsed gradient spin-echo (PGSE) (effective diffusion times [Δ eff ]: 6.5 ms and 35.2 ms) with b-values of 0 and 1000 s/mm2. Relative percentage changes between shorter and longer diffusion times were calculated using region-of-interest (ROI) analysis of brain tumors on λ 1 , λ 2 , λ 3 , and mean diffusivity (MD) maps. The diffusivities of PGSE, OGSE, and relative percentage changes were compared among each tumor type using a multiple comparisons Steel-Dwass test. The mean (standard deviation) MD at Δ eff of 6.5 ms was 1.07 ± 0.23 10−3 mm2/s, 1.19 ± 0.18 10−3 mm2/s, 1.19 ± 0.21 10−3 mm2/s for meningothelial meningiomas, acoustic neuromas, and pituitary adenomas, respectively. The mean (standard deviation) MD at Δ eff of 35.2 ms was 0.93 ± 0.22 10−3 mm2/s, 1.07 ± 0.19 10−3 mm2/s, 0.82 ± 0.21 10−3 mm2/s for meningothelial meningiomas, acoustic neuromas, and pituitary adenomas, respectively. The mean (standard deviation) of the relative percentage change was 15.7 ± 4.4%, 12.4 ± 8.2%, 46.8 ± 11.3% for meningothelial meningiomas, acoustic neuromas, and pituitary adenomas, respectively. Compared to meningiomas and acoustic neuromas, pituitary adenoma exhibited stronger diffusion time-dependence with diffusion times between 6.5 ms and 35.2 ms (P < 0.05). In conclusion, differences in diffusion time-dependence may be attributed to differences in the internal structures of brain tumors. DWI with a short diffusion time may provide additional information on the microstructure of each tumor and contribute to tumor diagnosis. [ABSTRACT FROM AUTHOR]

The present study describes a model-based approach for correcting off-resonance in the context of double half-echo k-space acquisitions. This technique employs center-out readouts in forward and reverse directions to reduce echo-times but is sensitive to off-resonance, which manifests as pixel shifts in both directions. Demodulating the k-space signal with a constant off-resonance term per slice removes pixel shifts and results in a marked reduction in blurring. Phantom and in vivo datasets are demonstrated from low bandwidth sodium imaging. [ABSTRACT FROM AUTHOR]

Sodium imaging typically employs ultrashort echo time radial, density adapted and cones trajectories to capture the rapidly decaying short T2 signal. The present study considers the parameter choices involved in the use of these trajectories in terms of their impact on the resolution and signal to noise ratio. Many parameters have a strong effect on these image properties, particularly the number of spokes which impacts voxel size. The present article develops an understanding of the trade-offs involved and how to choose optimal (or at least reasonable) parameter values. This has a practical role in designing clinical protocols for imaging sodium. [ABSTRACT FROM AUTHOR]

Three‐dimensional (3D) Magnetic resonance fingerprinting (MRF) permits whole‐brain volumetric quantification of T1 and T2 relaxation values, potentially replacing conventional T1‐weighted structural imaging for common brain imaging analysis. The aim of this study was to evaluate the repeatability and reproducibility of 3D MRF in evaluating brain cortical thickness and subcortical volumetric analysis in healthy volunteers using conventional 3D T1‐weighted images as a reference standard. Scan‐rescan tests of both 3D MRF and conventional 3D fast spoiled gradient recalled echo (FSPGR) were performed. For each sequence, the regional cortical thickness and volume of the subcortical structures were measured using standard automatic brain segmentation software. Repeatability and reproducibility were assessed using the within‐subject coefficient of variation (wCV), intraclass correlation coefficient (ICC), and mean percent difference and ICC, respectively. The wCV and ICC of cortical thickness were similar across all regions with both 3D MRF and FSPGR. The percent relative difference in cortical thickness between 3D MRF and FSPGR across all regions was 8.0 ± 3.2%. The wCV and ICC of the volume of subcortical structures across all structures were similar between 3D MRF and FSPGR. The percent relative difference in the volume of subcortical structures between 3D MRF and FSPGR across all structures was 7.1 ± 3.6%. 3D MRF measurements of human brain cortical thickness and subcortical volumes are highly repeatable, and consistent with measurements taken on conventional 3D T1‐weighted images. A slight, consistent bias was evident between the two, and thus careful attention is required when combining data from MRF and conventional acquisitions. [ABSTRACT FROM AUTHOR]

Oscillating gradient spin-echo (OGSE) sequences enable acquisitions with shorter diffusion times. There is growing interest in the effect of diffusion time on apparent diffusion coefficient (ADC) values in patients with cancer. However, little evidence exists regarding its usefulness for differentiating between high-grade and low-grade brain tumors. The purpose of this study is to investigate the utility of changes in the ADC value between short and long diffusion times in distinguishing low-grade and high-grade brain tumors. Eleven patients with high-grade brain tumors and ten patients with low-grade brain tumors were scanned using a 3 T magnetic resonance imaging with diffusion-weighted imaging (DWI) using OGSE and PGSE (effective diffusion time [Δ eff ]: 6.5 ms and 35.2 ms) and b-values of 0 and 1000 s/mm2. Using a region of interest (ROI) analysis of the brain tumors, we measured the ADC for two Δeff (ADC Δeff) values and computed the subtraction ADC (ΔADC = ADC 6.5 ms − ADC 35.2 ms) and the relative ADC (ΔADC = (ADC 6.5 ms − ADC 35.2 ms) / ADC 35.2 ms × 100). The maximum values for the subtraction ADC (ΔADC max) and the relative ADC (rADC max) on the ROI were compared between low-grade and high-grade tumors using the Wilcoxon rank-sum test. A P -value <.05 was considered significant. The ROIs were also placed in the normal white matter of patients with high- and low-grade brain tumors, and ΔADC max values were determined. High-grade tumors had significantly higher ΔADC max and rADC max than low-grade tumors. The ΔADC max values of the normal white matter were lower than the ΔADC max of high- and low-grade brain tumors. The dependence of ADC values on diffusion time between 6.5 ms and 35.2 ms was stronger in high-grade tumors than in low-grade tumors, suggesting differences in internal tissue structure. This finding highlights the importance of reporting diffusion times in ADC evaluations and might contribute to the grading of brain tumors using DWI. [ABSTRACT FROM AUTHOR]

Purpose: The reproducibility of neurite orientation dispersion and density imaging (NODDI) metrics in the human brain has not been explored across different magnetic resonance (MR) scanners from different vendors. This study aimed to evaluate the scan–rescan and inter-vendor reproducibility of NODDI metrics in white and gray matter of healthy subjects using two 3-T MR scanners from two vendors. Methods: Ten healthy subjects (7 males; mean age 30 ± 7 years, range 23–37 years) were included in the study. Whole-brain diffusion-weighted imaging was performed with b-values of 1000 and 2000 s/mm2 using two 3-T MR scanners from two different vendors. Automatic extraction of the region of interest was performed to obtain NODDI metrics for whole and localized areas of white and gray matter. The coefficient of variation (CoV) and intraclass correlation coefficient (ICC) were calculated to assess the scan–rescan and inter-vendor reproducibilities of NODDI metrics. Results: The scan–rescan and inter-vendor reproducibility of NODDI metrics (intracellular volume fraction and orientation dispersion index) were comparable with those of diffusion tensor imaging (DTI) metrics. However, the inter-vendor reproducibilities of NODDI (CoV = 2.3–14%) were lower than the scan–rescan reproducibility (CoV: scanner A = 0.8–3.8%; scanner B = 0.8–2.6%). Compared with the finding of DTI metrics, the reproducibility of NODDI metrics was lower in white matter and higher in gray matter. Conclusion: The lower inter-vendor reproducibility of NODDI in some brain regions indicates that data acquired from different MRI scanners should be carefully interpreted. [ABSTRACT FROM AUTHOR]

Purpose: Micro fractional anisotropy (μFA) is more accurate than conventional fractional anisotropy (FA) for assessing microscopic tissue properties and can overcome limitations related to crossing white matter fibres. We compared μFA and FA for evaluating white matter changes in patients with Parkinson's disease (PD). Methods: We compared FA and μFA measures between 25 patients with PD and 25 age- and gender-matched healthy controls using tract-based spatial statistics (TBSS) analysis. We also examined potential correlations between changes, revealed by conventional FA or μFA, and disease duration or Unified Parkinson's Disease Rating Scale (UPDRS)-III scores. Results: Compared with healthy controls, patients with PD had significantly reduced μFA values, mainly in the anterior corona radiata (ACR). In the PD group, μFA values (primarily those from the ACR) were significantly negatively correlated with UPDRS-III motor scores. No significant changes or correlations with disease duration or UPDRS-III scores with tissue properties were detected using conventional FA. Conclusion: μFA can evaluate microstructural changes that occur during white matter degeneration in patients with PD and may overcome a key limitation of FA. [ABSTRACT FROM AUTHOR]

Purpose: This study aimed to evaluate the accuracy and diagnostic test performance of the U-net-based segmentation method in neuromelanin magnetic resonance imaging (NM-MRI) compared to the established manual segmentation method for Parkinson's disease (PD) diagnosis. Methods: NM-MRI datasets from two different 3T-scanners were used: a "principal dataset" with 122 participants and an "external validation dataset" with 24 participants, including 62 and 12 PD patients, respectively. Two radiologists performed SNpc manual segmentation. Inter-reader precision was determined using Dice coefficients. The U-net was trained with manual segmentation as ground truth and Dice coefficients used to measure accuracy. Training and validation steps were performed on the principal dataset using a 4-fold cross-validation method. We tested the U-net on the external validation dataset. SNpc hyperintense areas were estimated from U-net and manual segmentation masks, replicating a previously validated thresholding method, and their diagnostic test performances for PD determined. Results: For SNpc segmentation, U-net accuracy was comparable to inter-reader precision in the principal dataset (Dice coefficient: U-net, 0.83 ± 0.04; inter-reader, 0.83 ± 0.04), but lower in external validation dataset (Dice coefficient: U-net, 079 ± 0.04; inter-reader, 0.85 ± 0.03). Diagnostic test performances for PD were comparable between U-net and manual segmentation methods in both principal (area under the receiver operating characteristic curve: U-net, 0.950; manual, 0.948) and external (U-net, 0.944; manual, 0.931) datasets. Conclusion: U-net segmentation provided relatively high accuracy in the evaluation of the SNpc in NM-MRI and yielded diagnostic performance comparable to that of the established manual method. [ABSTRACT FROM AUTHOR]

Purpose: Autism spectrum disorder (ASD) is related to impairment in various white matter (WM) pathways. Utility of the recently developed two-compartment model of diffusion kurtosis imaging (DKI) to analyse axial diffusivity of WM is restricted by several limitations. The present study aims to validate the utility of model-free DKI in the evaluation of WM alterations in ASD and analyse the potential relationship between DKI-evident WM alterations and personality scales. Methods: Overall, 15 participants with ASD and 15 neurotypical (NT) controls were scanned on a 3 T magnetic resonance (MR) scanner, and scores for autism quotient (AQ), systemising quotient (SQ) and empathising quotient (EQ) were obtained for both groups. Multishell diffusion-weighted MR data were acquired using two b-values (1000 and 2000 s/mm2). Differences in mean kurtosis (MK), radial kurtosis (RK) and axial kurtosis (AK) between the groups were evaluated using tract-based spatial statistics (TBSS). Finally, the relationships between the kurtosis indices and personality quotients were examined. Results: The ASD group demonstrated significantly lower AK in the body and splenium of corpus callosum than the NT group; however, no other significant differences were identified. Negative correlations were found between AK and AQ or SQ, predominantly in WM areas related to social–emotional processing such as uncinate fasciculus, inferior fronto-occipital fasciculus, and inferior and superior longitudinal fasciculi. Conclusions: Model-free DKI and its indices may represent a novel, objective method for detecting the disease severity and WM alterations in patients with ASD. [ABSTRACT FROM AUTHOR]

Abstract Introduction Oscillating gradient spin-echo (OGSE) sequences can shorten diffusion times by replacing the long-lasting diffusion-sensitizing gradients used in pulsed gradient spin-echo (PGSE) methods with rapidly oscillating gradients. To obtain information regarding the internal structure of choroid plexus cysts that appear hyperintense on diffusion-weighted imaging (DWI), we investigated the apparent diffusion coefficient (ADC) values acquired with a shorter diffusion time using an OGSE sequence. Material and methods Twenty-seven patients with choroid plexus cysts were scanned using a 3 T magnetic resonance scanner. DWI was performed with both OGSE and PGSE, with effective diffusion times (Δ eff) of 6.5 and 35.2 ms, respectively. ADC values for choroid plexus cysts, white matter (WM), and cerebrospinal fluid (CSF) were measured. The ADC values obtained with the shorter and longer diffusion times were compared using the Wilcoxon signed-rank test. P <.05 was considered significant. Results The ADC values of choroid plexus cysts and WM were significantly higher at the Δ eff of 6.5 ms on OGSE than with the Δ eff of 35.2 ms on PGSE. The ADC values of CSF were significantly lower at the Δ eff of 6.5 ms on OGSE than with the Δ eff of 35.2 ms on PGSE. The ADC values of choroid plexus cysts were lower than the ADC values of CSF with Δ eff of 35.2 and 6.5 ms. Conclusions The dependence of ADC values on the diffusion time in choroid plexus cysts suggested spatially restricted diffusion. In measurements obtained with short diffusion times, the lower ADC values for choroid plexus cysts in comparison with the CSF indicated the presence of spatially restricted diffusion and increased cyst viscosity. [ABSTRACT FROM AUTHOR]

Purpose: To test the hypothesis that "acute-period" lumbar MRI in non-elderly patients with low back pain is less frequently performed at clinics/hospitals with greater involvement of full-time radiologists in the imaging workflow.Methods: In a national-level claims database, we identified 14,819 non-elderly patients (mean age: 38.7±8.0 years) who visited clinics/hospitals for low back pain in 2013-2015. We classified the clinics/hospitals into four groups based on the level of full-time radiologist involvement and MRI ownership, and compared the frequency of acute-period lumbar MRI using hierarchical logistic regression analysis.Results: Patients visiting facilities without a full-time radiologist (n=2105) were significantly (p<0.001) more likely to undergo acute-period MRI than those visiting facilities with ≥1 radiologist partially managing imaging workflow (level-1, n=491) or ≥1 radiologist intensively involved in imaging workflow (level-2, n=1190) (15.7% vs. 6.9% and 7.3%; adjusted odds ratio of no-radiologist versus level-2: 2.93, p=0.018). No difference was observed between level-1 and level-2 involvement.Conclusions: Facilities with no full-time radiologist were more likely to perform acute-period MRI to assess for low back pain, while no difference was seen between facilities with varying levels of radiologist involvement in the imaging workflow. Radiologist involvement may contribute to optimal utilisation of medical imaging.Key Points: • Lumbar MRI was more frequently performed at facilities without full-time radiologists. • Full-time radiologists may play an important role in appropriate utilisation of imaging. • Frequency of MRI was similar between moderate and intensive radiologist involvement. [ABSTRACT FROM AUTHOR]

We report a case of splenic infarction in a patient with sickle cell traits (SCT), focusing on the computed tomography (CT) findings. The patient was an African-American man in his twenties with no past medical history who experienced sudden left upper quadrant pain while climbing a mountain (over 3000 m above sea level). Dynamic contrast-enhanced CT revealed massive non-segmental splenic infarction accompanied with nodule-like preserved splenic tissue. The region of splenic infarction did not coincide with the arterial vascular territory and differed from the features of infarction caused by large arterial embolism. In addition, thrombotic occlusion of the distal splenic vein was depicted on plain and contrast-enhanced thin-slice CT images. Early-phase contrast-enhanced images also showed inhomogeneous enhancement of the hepatic parenchyma. The patient's symptoms improved with conservative therapy. A hemoglobin electrophoresis test confirmed the diagnosis of SCT. SCT is usually asymptomatic, but hypoxic environments may induce acute splenic syndrome, which is commonly manifested as splenic infarction. We observed splenic venous thrombosis and inhomogeneous hepatic parenchymal enhancement in addition to a huge splenic infarction in our patient. To the best of our knowledge, this is the first report describing the specific imaging findings, particularly splenic venous thrombosis and inhomogeneous hepatic parenchymal enhancement, of acute splenic syndrome in a patient with previously undiagnosed SCT. These findings demonstrate the pathophysiology of SCT, and may help with the diagnosis of this disease. [ABSTRACT FROM AUTHOR]

There has been an increasing prevalence of neurodegenerative diseases with the rapid increase in aging societies worldwide. Biomarkers that can be used to detect pathological changes before the development of severe neuronal loss and consequently facilitate early intervention with disease-modifying therapeutic modalities are therefore urgently needed. Diffusion magnetic resonance imaging (MRI) is a promising tool that can be used to infer microstructural characteristics of the brain, such as microstructural integrity and complexity, as well as axonal density, order, and myelination, through the utilization of water molecules that are diffused within the tissue, with displacement at the micron scale. Diffusion tensor imaging is the most commonly used diffusion MRI technique to assess the pathophysiology of neurodegenerative diseases. However, diffusion tensor imaging has several limitations, and new technologies, including neurite orientation dispersion and density imaging, diffusion kurtosis imaging, and free-water imaging, have been recently developed as approaches to overcome these constraints. This review provides an overview of these technologies and their potential as biomarkers for the early diagnosis and disease progression of major neurodegenerative diseases. [ABSTRACT FROM AUTHOR]

Multiple sclerosis (MS) is a brain network disconnection syndrome. Although the brain network topology in MS has been evaluated using diffusion MRI tractography, the mechanism underlying disconnection in the disorder remains unclear. In this study, we evaluated the brain network topology in MS using connectomes with connectivity strengths based on the ratio of the inner to outer myelinated axon diameter (i.e., g-ratio), thereby providing enhanced sensitivity to demyelination compared with the conventional measures of connectivity. We mapped g-ratio-based connectomes in 14 patients with MS and compared them with those of 14 age- and sex-matched healthy controls. For comparison, probabilistic tractography was also used to map connectomes based on the number of streamlines (NOS). We found that g-ratio- and NOS-based connectomes comprised significant connectivity reductions in patients with MS, predominantly in the motor, somatosensory, visual, and limbic regions. However, only the g-ratio-based connectome enabled detection of significant increases in nodal strength in patients with MS. Finally, we found that the g-ratio-weighted nodal strength in motor, visual, and limbic regions significantly correlated with inter-individual variation in measures of disease severity. The g-ratio-based connectome can serve as a sensitive biomarker for diagnosing and monitoring disease progression. [ABSTRACT FROM AUTHOR]

This study aimed to discriminate between neuroinflammation and neuronal degeneration in the white matter (WM) and gray matter (GM) of patients with Parkinson's disease (PD) using free-water (FW) imaging. Analysis using tract-based spatial statistics (TBSS) of 20 patients with PD and 20 healthy individuals revealed changes in FW imaging indices (i.e., reduced FW-corrected fractional anisotropy (FAT), increased FW-corrected mean, axial, and radial diffusivities (MDT, ADT, and RDT, respectively) and fractional volume of FW (FW) in somewhat more specific WM areas compared with the changes of DTI indices. The region-of-interest (ROI) analysis further supported these findings, whereby those with PD showed significantly lower FAT and higher MDT, ADT, and RDT (indices of neuronal degeneration) in anterior WM areas as well as higher FW (index of neuroinflammation) in posterior WM areas compared with the controls. Results of GM-based spatial statistics (GBSS) analysis revealed that patients with PD had significantly higher MDT, ADT, and FW than the controls, whereas ROI analysis showed significantly increased MDT and FW and a trend toward increased ADT in GM areas, corresponding to Braak stage IV. These findings support the hypothesis that neuroinflammation precedes neuronal degeneration in PD, whereas WM microstructural alterations precede changes in GM. [ABSTRACT FROM AUTHOR]

Background: Intravoxel incoherent motion magnetic resonance imaging (IVIM) enables non-invasive measurement of brain perfusion. Purpose: To investigate whether IVIM could be used to evaluate the hemodynamic disturbance of Moyamoya disease (MMD) by comparison with the gold-standard 15O-gas positron emission tomography (PET) method. Material and Methods: Ten consecutive patients with MMD (six women; mean age = 42.8 years) and 10 age-matched healthy controls were evaluated by diffusion-weighted images with 12 different b values in the range of 0–900 s/mm2 and 15O-gas PET. Tomographic maps of IVIM parameters, perfusion fraction (f), pseudo-diffusion coefficient (D*), and f・D*, as well as cerebral blood volume (CBV), cerebral blood flow (CBF), and mean transit time (MTT) maps obtained with PET, were normalized and hemispheric gray and white matter values were calculated. IVIM parametric values were compared with PET parameters and with clinically assessed disease severity. Results: There was significant correlation between D* and MTT (r = –0.74, P < 0.001) and between f・D* and CBF (r = 0.52, P = 0.02) in the cortical areas. The f values in the white matter were significantly higher in symptomatic MMD patients than in healthy controls (P = 0.01). Conclusion: IVIM may be used to non-invasively investigate cerebral hemodynamic impairment in patients with MMD. Further evaluation is needed to establish IVIM usage in clinical settings. [ABSTRACT FROM AUTHOR]