Fast Low-angle Shot Sequence Research Articles

T1ρ relaxation mapping in osteochondral lesions of the talus: a non-invasive biomarker for altered biomechanical properties of hyaline cartilage?

BackgroundTo evaluate T1ρ relaxation mapping in patients with symptomatic talar osteochondral lesions (OLT) and healthy controls (HC) at rest, with axial loading and traction.MethodsParticipants underwent 3-T ankle magnetic resonance imaging at rest and with 500 N loading and 120 N traction, without axial traction for a subcohort of 17/29 HC. We used a fast low-angle shot sequence with variable spin-lock intervals for monoexponential T1ρ fitting. Cartilage was manually segmented to extract T1ρ values.ResultsWe studied 29 OLT patients (age 31.7 ± 7.5 years, 15 females, body mass index [BMI] 25.0 ± 3.4 kg/m2) and 29 HC (age 25.2 ± 4.3 years, 17 females, BMI 22.5 ± 2.3 kg/m2. T1ρ values of OLT (50.4 ± 3.4 ms) were higher than those of intact cartilage regions of OLT patients (47.2 ± 3.4 ms; p = 0.003) and matched HC cartilage (48.1 ± 3.3 ms; p = 0.030). Axial loading and traction induced significant T1ρ changes in the intact cartilage regions of patients (loading, mean difference -1.1 ms; traction, mean difference 1.4 ms; p = 0.030 for both) and matched HC cartilage (-2.2 ms, p = 0.003; 2.3 ms, p = 0.030; respectively), but not in the OLT itself (-1.3 ms; p = 0.150; +1.9 ms; p = 0.150; respectively).ConclusionIncreased T1ρ values may serve as a biomarker of cartilage degeneration in OLT. The absence of load- and traction-induced T1ρ changes in OLT compared to intact cartilage suggests that T1ρ may reflect altered biomechanical properties of hyaline cartilage.Trial registrationDRKS, DRKS00024010. Registered 11 January 2021, https://drks.de/search/de/trial/DRKS00024010.Relevance statementT1ρ mapping has the potential to evaluate compositional and biomechanical properties of the talar cartilage and may improve therapeutic decision-making in patients with osteochondral lesions.Key PointsT1ρ values in osteochondral lesions increased compared to intact cartilage.Significant load- and traction-induced T1ρ changes were observed in visually intact regions and in healthy controls but not in osteochondral lesions.T1ρ may serve as an imaging biomarker for biomechanical properties of cartilage.Graphical

Post‐Myocardial Infarction Remodeling and Hyperkinetic Remote Myocardium in Sheep Measured by Cardiac MRI Feature Tracking

BackgroundCardiac MRI feature tracking (FT) allows objective assessment of segmental left ventricular (LV) function following a myocardial infarction (MI), but its utilization in sheep, where interventions can be tested, is lacking.PurposeTo apply and validate FT in a sheep model of MI and describe post‐MI LV remodeling.Study TypeAnimal model, longitudinal.Animal ModelEighteen lambs (6 months, male, n = 14; female, n = 4; 25.2 ± 4.5 kg).Field Strength/SequenceTwo‐dimensional balanced steady‐state free precession (bSSFP) and 3D inversion recovery fast low angle shot (IR‐FLASH) sequences at 3 T.AssessmentSeven lambs underwent test–retest imaging to assess FT interstudy reproducibility. MI was induced in the remaining 11 by coronary ligation with MRI being undertaken before and 15 days post‐MI. Injury size was measured by late gadolinium enhancement (LGE) and LV volumes, LV mass, ejection fraction (LVEF), and wall thickness (LVWT) were measured, with FT measures of global and segmental radial, circumferential, and longitudinal strain.Statistical TestsSampling variability, inter‐study, intra and interobserver reproducibility were assessed using Pearson's correlation, Bland–Altman analyses, and intra‐class correlation coefficients (ICC). Diagnostic performance of segmental strain to predict LGE was assessed using receiver operating characteristic curve analysis. Significant differences were considered P < 0.05.ResultsInter‐study reproducibility of FT was overall good to excellent, with global strain being more reproducible than segmental strain (ICC = 0.89–0.98 vs. 0.77–0.96). MI (4.0 ± 3.7% LV mass) led to LV remodeling, as evident by significantly increased LV volumes and LV mass, and significantly decreased LVWT in injured regions, while LVEF was preserved (54.9 ± 6.9% vs. 55.6 ± 5.7%; P = 0.778). Segmental circumferential strain (CS) correlated most strongly with LGE. Basal and mid‐ CS increased significantly, while apical CS significantly decreased post‐MI.Data ConclusionFT is reproducible and compensation by hyperkinetic remote myocardium may manifest as overall preserved global LV function.Evidence LevelN/ATechnical EfficacyStage 2

Automated deep learning segmentation of high-resolution 7 Tesla postmortem MRI for quantitative analysis of structure-pathology correlations in neurodegenerative diseases.

Postmortem MRI allows brain anatomy to be examined at high resolution and to link pathology measures with morphometric measurements. However, automated segmentation methods for brain mapping in postmortem MRI are not well developed, primarily due to limited availability of labeled datasets, and heterogeneity in scanner hardware and acquisition protocols. In this work, we present a high-resolution dataset of 135 postmortem human brain tissue specimens imaged at 0.3 mm3 isotropic using a T2w sequence on a 7T whole-body MRI scanner. We developed a deep learning pipeline to segment the cortical mantle by benchmarking the performance of nine deep neural architectures, followed by post-hoc topological correction. We evaluate the reliability of this pipeline via overlap metrics with manual segmentation in 6 specimens, and intra-class correlation between cortical thickness measures extracted from the automatic segmentation and expert-generated reference measures in 36 specimens. We also segment four subcortical structures (caudate, putamen, globus pallidus, and thalamus), white matter hyperintensities, and the normal appearing white matter, providing a limited evaluation of accuracy. We show generalizing capabilities across whole-brain hemispheres in different specimens, and also on unseen images acquired at 0.28 mm3 and 0.16 mm3 isotropic T2*w fast low angle shot (FLASH) sequence at 7T. We report associations between localized cortical thickness and volumetric measurements across key regions, and semi-quantitative neuropathological ratings in a subset of 82 individuals with Alzheimer's disease (AD) continuum diagnoses. Our code, Jupyter notebooks, and the containerized executables are publicly available at the project webpage (https://pulkit-khandelwal.github.io/exvivo-brain-upenn/).

Coronary Microvascular Dysfunction and Diffuse Myocardial Fibrosis in Patients With Type 2 Diabetes Using Quantitative Perfusion MRI.

Imaging techniques that quantitatively and automatically measure changes in the myocardial microcirculation in patients with diabetes are lacking. To detect diabetic myocardial microvascular complications using a novel automatic quantitative perfusion MRI technique, and to explore the relationship between myocardial microcirculation dysfunction and fibrosis. Prospective. 101 patients with type 2 diabetes mellitus (T2DM) (53 without and 48 with complications), 20 healthy volunteers. 3.0T; modified Look-Locker inversion-recovery sequence; saturation recovery sequence and dual-bolus technique; segmented fast low-angle shot sequence. All participants underwent MRI to determine the rest myocardial blood flow (MBF), stress MBF, myocardial perfusion reserve (MPR), and extracellular volume (ECV), which represents the extent of myocardial fibrosis. Kolmogorov-Smirnov test, Shapiro-Wilk test, Kruskal-Wallis H test, Mann-Whitney U test, chi-square test, Spearman correlation coefficient, multivariable linear regression analysis. P < 0.05 was considered statistically significant. The rest MBF was not significantly different between the T2DM without complications group (1.1, IQR: 0.9-1.3) and the control group (1.1, 1.0-1.3) (P = 1.000), but it was significantly lower in the T2DM with complications group (0.8, 0.6-1.0) than in both other groups. The stress MBF and MPR were significantly lower in the T2DM without complications group (1.9, 1.5-2.3, and 1.7, 1.4-2.1, respectively) than in the control group (3.0, 2.6-3.5, and 2.7, 2.4-3.1, respectively), and were also significantly lower in the T2DM with complications group (1.1, 0.9-1.4, and 1.4, 1.2-1.8, respectively) than in the T2DM without complications group. A decrease in MBF and MPR were significantly associated with an increase in the ECV. Quantitative perfusion MRI can evaluate myocardial microcirculation dysfunction. In T2DM, there was a significant decrease in both MBF and MPR compared to healthy controls, with the decrease being significantly different between T2DM with and without complications groups. The decrease of MBF was significantly associated with the development of myocardial fibrosis, as determined by ECV. 2 TECHNICAL EFFICACY: Stage 3.

Voxel-Based Morphometry of Progressive Supranuclear Palsy Using a 3D Fast Low-angle Shot Localizer Image: A Comparison with Magnetization-Prepared Rapid Gradient Echo.

Voxel-based morphometry (VBM) is widely used to investigate white matter (WM) atrophy in patients with progressive supranuclear palsy (PSP). In contrast to high-resolution 3D T1-weighted imaging such as magnetization-prepared rapid acquisition with gradient echo (MPRAGE) sequences, the utility of other 3D sequences has not been sufficiently evaluated. This study aimed to assess the feasibility of using a 3D fast low-angle shot sequence captured as a localizer image (L3DFLASH) for VBM analysis of WM atrophy patterns in patients with PSP. This retrospective study included 12 patients with pathologically or clinically confirmed PSP, and 18 age- and sex-matched healthy controls scanned with both L3DFLASH and MPRAGE sequences. Image processing was conducted with the Computational Anatomy Toolbox 12 in statistical parametric mapping 12. In addition to the atrophic WM pattern of PSP on VBM, we assessed the WM volume agreement between the two sequences using simple linear regression and Bland-Altman plots. Despite the slightly larger clusters on MPRAGE, VBM using both sequences showed similar characteristics of PSP-related WM atrophy, including in the midbrain, pons, thalamus, and precentral gyrus. In contrast, VBM showed gray matter (GM) atrophy of the precuneus and right superior parietal lobule exclusively on L3DFLASH. Unlike the measured values of total intracranial volume, GM, and cerebrospinal fluid on MPRAGE, the value of WM was larger on L3DFLASH. In contrast to the total intracranial volume, brainstem, and frontal and occipital lobes, the correlation with WM volume in other regions was relatively low. However, the Bland-Altman plots demonstrated strong agreement, with over 90% of the values falling within the agreement limits. Both MPRAGE and L3DFLASH are useful for detecting PSP-related WM atrophy using VBM.

MRI compatibility testing of commercial high intensity focused ultrasound transducers

PurposeThe study aimed to compare the performance of eight commercially available single-element High Intensity Focused Ultrasound (HIFU) transducers in terms of Magnetic Resonance Imaging (MRI) compatibility. MethodsImaging of an agar-based MRI phantom was performed in a 3 T MRI scanner utilizing T2-Weighted Fast Spin Echo (FSE) and Fast low angle shot (FLASH) sequences, which are typically employed for high resolution anatomical imaging and thermometry, respectively. Reference magnitude and phase images of the phantom were compared with images acquired in the presence of each transducer in terms of the signal to noise ratio (SNR), introduced artifacts, and overall image quality. ResultsThe degree of observed artifacts highly differed among the various transducers. The transducer whose backing material included magnetic impurities showed poor performance in the MRI, introducing significant susceptibility artifacts such as geometric distortions and signal void bands. Additionally, it caused the most significant SNR drop. Other transducers were shown to exhibit high level of MRI compatibility as the resulting images closely resembled the reference images with minimal to no apparent artifacts and comparable SNR values. ConclusionsThe study findings may facilitate researchers to select the most suitable transducer for their research, simultaneously avoiding unnecessary testing. The study further provides useful design considerations for MRI compatible transducers.

Whole-body magnetic resonance imaging in two minutes: cross-sectional real-time coverage of multiple volumes.

This work describes a novel technique for rapid and motion-robust whole-body magnetic resonance imaging (MRI). The method employs highly undersampled radial fast low angle shot (FLASH) sequences to cover large volumes by cross-sectional real-time MRI with automatic slice advancement after each frame. The slice shift typically amounts to a fraction of the slice thickness (e.g., 10% to 50%) in order to generate a successive series of partially overlapping sections. Joint reconstructions of these serial images and their respective coil sensitivity maps rely on nonlinear inversion (NLINV) with regularization to the image and sensitivity maps of a preceding frame. The procedure exploits the spatial similarity of neighboring sections. Whole-body scanning is accomplished by measuring multiple volumes at predefined locations, i.e., at fixed table positions, in combination with intermediate automatic movements of the patient table. Individual volumes may take advantage of different field-of-views, image orientations, spatial and temporal resolutions as well as contrasts. Preliminary proof-of-principle applications to healthy subjects at 3 T without cardiac gating and during free breathing yield high-quality anatomic images with acquisition times of less than 100 ms. Spin-density and T1 contrasts are obtained by spoiled FLASH sequences, while T2-type (i.e., T2/T1) contrast results from refocused FLASH sequences that generate a steady state free precession (SSFP) free induction decay (FID) signal. Total measuring times excluding vendor-controlled adjustment procedures are less than two minutes for a 100 cm scan that, for example, covers the body from head to thigh by three optimized volumes and more than 1,300 images. In conclusion, after demonstrating technical feasibility the proposed method awaits clinical trials.

Correlation of brain iron deposition and freezing of gait in Parkinson's disease: a cross-sectional study.

Quantitative susceptibility mapping (QSM) is a novel imaging method for detecting iron content in the brain. The study aimed determine whether the iron deposition in the brains of people with Parkinson's disease (PD) is correlated with freezing of gait (FOG). We retrospectively collected the data of 24 patients with PD from the Movement Disorders Program and 36 healthy controls (HCs) from January 2021 to December 2021. Clinical assessments included mental intelligence scales, Parkinson rating scales, motor-related scales, and clinical gait assessments. All exercise scales and gait assessments were performed in the "ON" and "OFF" states. Magnetic resonance imaging (MRI) data were collected using 3-dimensional fast low-angle shot sequences. We chose the bilateral red nucleus, substantia nigra, thalamus, putamen, caudate nucleus, and globus pallidus as regions of interest for QSM analysis. The iron deposition in the substantia nigra of the PD group was significantly higher than that of the HC group (P<0.01). In the PD group, the iron deposition in the substantia nigra of patients with FOG was significantly higher than that in patients without FOG (P=0.04). The iron deposition in the substantia nigra was positively correlated with the New Freezing of Gait Questionnaire (P=0.03). The scores for depression and anxiety of the PD group were significantly higher than those of the HC group, while the Berg balance scale score was significantly lower (P<0.01). The iron deposition in the substantia nigra of patients with PD is increased compared with that of controls and is associated with FOG. QSM can be used to detect brain iron deposition in patients with PD, which would help to explore the mechanism of abnormal neurobiological activity in FOG.

Radiomic analysis of the proximal femur in osteoporosis women using 3T MRI

IntroductionOsteoporosis (OP) results in weak bone and can ultimately lead to fracture. MRI assessment of bone structure and microarchitecture has been proposed as method to assess bone quality and fracture risk in vivo. Radiomics provides a framework to analyze the textural information of MR images. The purpose of this study was to analyze the radiomic features and its abilityto differentiate between subjects with and without prior fragility fracture.MethodsMRI acquisition was performed on n = 45 female OP subjects: 15 with fracture history (Fx) and 30 without fracture history (nFx) using a high-resolution 3D Fast Low Angle Shot (FLASH) sequence at 3T. Second and first order radiomic features were calculated in the trabecular region of the proximal femur on T1-weighted MRI signal of a matched dataset. Significance of the feature’s predictive ability was measured using Wilcoxon test and Area Under the ROC (AUROC) curve analysis. The features were correlated DXA and FRAX score.ResultA set of three independent radiomic features (Dependence Non-Uniformity (DNU), Low Gray Level Emphasis (LGLE) and Kurtosis) showed significant ability to predict fragility fracture (AUROC DNU = 0.751, p &amp;lt; 0.05; AUROC LGLE = 0.729, p &amp;lt; 0.05; AUROC Kurtosis = 0.718, p &amp;lt; 0.05) with low to moderate correlation with FRAX and DXA.ConclusionRadiomic features can measure bone health in MRI of proximal femur and has the potential to predict fracture.

Diagnostic Performance and Safety of a Novel Ferumoxytol-Enhanced Coronary Magnetic Resonance Angiography.

Currently, noninvasive arteriography for the diagnosis of coronary artery disease is clinically limited to the computed tomography scanning, where patients have to be exposed to the radiation and risks associated with iodinated contrast. We aimed to investigate the diagnostic performance and safety of a novel ferumoxytol-enhanced coronary magnetic resonance angiography (CMRA) in patients with suspected coronary artery disease. Thirty patients, 19 males, with a median age of 63 years old, and 17 with renal insufficiency, who were scheduled for invasive coronary angiography, were enrolled. Ferumoxytol was administered intravenously with a dose of 3 mg/kg during CMRA. Images were acquired with an ECG-triggered, navigator-gated, inversion recovery-prepared 3D fast low-angle shot sequence, and the image quality was assessed by a 4-point scale. Eighteen-segment coronary artery model was adopted to evaluate the visibility of the coronary arteries, and the image quality and stenosis were evaluated in nine segments. The diagnostic performance of CMRA is described as sensitivity, specificity, positive and negative predictive values, and accuracy with the invasive coronary angiography results as reference. The patients' vital signs were monitored during CMRA, and their hepatic and renal functions were followed up for 3 months to evaluate the safety of ferumoxytol. Two hundred fifty-two of the 270 study segments were identified by CMRA, and their quality score reached 3.6±0.7. Referring to the invasive coronary angiography results, the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of ferumoxytol-enhanced CMRA reached 100.0%, 66.7%, 92.3%, 100.0%, and 93.3% respectively in patient-based analysis; 91.4%, 90.9%, 86.5%, 94.3%, and 91.1%, respectively in vessel-based analysis; and 92.3%, 96.7%, 83.7%, 98.6%, and 96.0%, respectively in segment-based analysis. No ferumoxytol-related adverse event was observed during the 3-month follow-up. Ferumoxytol-enhanced CMRA demonstrated good diagnostic performance and excellent safety in the diagnosis of significant coronary stenosis, providing an alternative to coronary computed tomography angiography for the diagnosis of coronary artery disease. URL: https://www. gov; Unique identifier: NCT05032937.

Non-contrast MR angiography of pelvic arterial vasculature using the Quiescent interval slice selective (QISS) sequence.

To evaluate Quiescent Interval Slice Selective (QISS) balanced steady-state free precession (bSSFP) and QISS fast low-angle shot (FLASH) sequences for non-contrast Magnetic Resonance Angiography (MRA) of iliac arteries regarding image quality and diagnostic confidence in order to establish these sequences in daily clinical practice. A prospective study of healthy subjects (n = 10) was performed. All subjects underwent the QISS MRI protocol with bSSFP und FLASH sequences. Vessel contrast-to-background ratio (VCBR) were measured in pre-defined vessel segments. Image quality and diagnostic confidence was assessed using a Likert scale (five-point scale). Inter-reader agreement was determined using Cohen's kappa coefficient (κ). Ten healthy subjects (median age 29 years, IQR: 26.25 to 30 years) were included in this prospective study. Median MR examination time was 2:05min (IQR 1:58 to 2:16) for QISS bSSFP and 4:11min (IQR 3:57 to 4:32) for QISS FLASH. Both sequences revealed good VCBR in all examined vessel segments. VCBR (muscle tissue) were marginally higher for FLASH sequences (e.g., 0.82 vs. 0.78 in the right femoral artery, p = 0.035*), while bSSFP sequence showed significantly higher VCBR (fat tissue) in the majority of examined arterials vessels (e.g., 0.78 vs. 0.62 in right femoral artery, p = 0.001*). The image quality and diagnostic confidence of both sequences were rated as good to excellent. Moderate to good inter-reader agreement was found. QISS MRA using bSSFP and FLASH sequences are diagnostic for visualization of iliac arterial vasculature. The QISS bSSFP sequence might offer advantages due to the markedly shorter exam time and superior visualization of smaller vessels. The QISS FLASH sequence seems to be a robust alternative for non-contrast MRA since it is less sensitive to magnetic field inhomogeneities.

Multi-site comparison of parametric T1 and T2 mapping: healthy travelling volunteers in the Berlin research network for cardiovascular magnetic resonance (BER-CMR)

BackgroundParametric mapping sequences in cardiovascular magnetic resonance (CMR) allow for non-invasive myocardial tissue characterization. However quantitative myocardial mapping is still limited by the need for local reference values. Confounders, such as field strength, vendors and sequences, make intersite comparisons challenging. This exploratory study aims to assess whether multi-site studies that control confounding factors provide first insights whether parametric mapping values are within pre-defined tolerance ranges across scanners and sites. MethodsA cohort of 20 healthy travelling volunteers was prospectively scanned at three sites with a 3 T scanner from the same vendor using the same scanning protocol and acquisition scheme. A Modified Look-Locker inversion recovery sequence (MOLLI) for T1 and a fast low-angle shot sequence (FLASH) for T2 were used. At one site a scan-rescan was performed to assess the intra-scanner reproducibility. All acquired T1- and T2-mappings were analyzed in a core laboratory using the same post-processing approach and software. ResultsAfter exclusion of one volunteer due to an accidentally diagnosed cardiac disease, T1- and T2-maps of 19 volunteers showed no significant differences between the 3 T sites (mean ± SD [95% confidence interval] for global T1 in ms: site I: 1207 ± 32 [1192–1222]; site II: 1207 ± 40 [1184–1225]; site III: 1219 ± 26 [1207–1232]; p = 0.067; for global T2 in ms: site I: 40 ± 2 [39–41]; site II: 40 ± 1 [39–41]; site III 39 ± 2 [39–41]; p = 0.543). ConclusionParametric mapping results displayed initial hints at a sufficient similarity between sites when confounders, such as field strength, vendor diversity, acquisition schemes and post-processing analysis are harmonized. This finding needs to be confirmed in a powered clinical trial.Trial registration ISRCTN14627679 (retrospectively registered)

Reference ranges of myocardial T1 and T2 mapping in healthy Chinese adults: a multicenter 3T cardiovascular magnetic resonance study

BackgroundAlthough reference ranges of T1 and T2 mapping are well established for cardiovascular magnetic resonance (CMR) at 1.5T, data for 3T are still lacking. The objective of this study is to establish reference ranges of myocardial T1 and T2 based on a large multicenter cohort of healthy Chinese adults at 3T CMR. MethodsA total of 1015 healthy Chinese adults (515 men, age range: 19–87 years) from 11 medical centers who underwent CMR using 3T Siemens scanners were prospectively enrolled. T1 mapping was performed with a motion-corrected modified Look–Locker inversion recovery sequence using a 5(3)3 scheme. T2 mapping images were acquired using T2-prepared fast low-angle shot sequence. T1 and T2 relaxation times were quantified for each slice and each myocardial segment. The T1 mapping and extracellular volume standardization (T1MES) phantom was used for quality assurance at each center prior to subject scanning. ResultsThe phantom analysis showed strong consistency of spin echo, T1 mapping, and T2 mapping among centers. In the entire cohort, global T1 and T2 reference values were 1193 ± 34 ms and 36 ± 2.5 ms. Global T1 and T2 values were higher in females than in males (T1: 1211 ± 29 ms vs. 1176 ± 30 ms, p < 0.001; T2: 37 ± 2.3 ms vs. 35 ± 2.5 ms, p < 0.001). There were statistical differences in global T2 across age groups (p < 0.001), but not in global T1. Linear regression showed no correlation between age and global T1 or T2 values. In males, positive correlation was found between heart rate and global T1 (r = 0.479, p < 0.001). ConclusionsUsing phantom-validated imaging sequences, we provide reference ranges for myocardial T1 and T2 values on 3T scanners in healthy Chinese adults, which can be applied across participating sites.Trial registration URL: http://www.chictr.org.cn/index.aspx. Unique identifier: ChiCTR1900025518. Registration name: 3T magnetic resonance myocardial quantitative imaging standardization and reference value study: a multi-center clinical study.

High-Resolution Motion-corrected 7.0-T MRI to Derive Morphologic Measures from the Human Cerebellum in Vivo.

Background The human cerebellum has a large, highly folded cortical sheet. Its visualization is important for various disorders, including multiple sclerosis and spinocerebellar ataxias. The derivation of the cerebellar cortical surface in vivo is impeded by its high foliation. Purpose To image the cerebellar cortex, including its foliations and lamination, in less than 20 minutes, reconstruct the cerebellocortical surface, and extract cortical measures with use of motion-corrected, high-spatial-resolution 7.0-T MRI. Materials and Methods In this prospective study, conducted between February 2021 and July 2022, healthy participants underwent an examination with either a 0.19 × 0.19 × 0.5-mm3, motion-corrected fast low-angle shot (FLASH) sequence (14.5 minutes) or a whole-cerebellum 0.4 × 0.4 × 0.4-mm3, motion-corrected magnetization-prepared 2 rapid gradient-echo (MP2RAGE) sequence (18.5 minutes) at 7.0 T. Four participants underwent an additional FLASH sequence without motion correction. FLASH and MP2RAGE sequences were used to visualize the cerebellar cortical layers, derive cerebellar gray and white matter segmentations, and examine their fidelity. Quantitative measures were compared using repeated-measures analyses of variance or paired t tests. Results Nine participants (median age, 36 years [IQR, 25-42 years; range, 21-62 years]; five women) underwent examination with the FLASH sequence. Nine participants (median age, 37 years [IQR, 34-42 years; range, 25-62 years]; five men) underwent examination with the MP2RAGE sequence. A susceptibility difference between the expected location of the granular and molecular cerebellar layers was visually detected in the FLASH data in all participants. The segmentations derived from the whole-cerebellum MP2RAGE sequence showed the characteristic anatomic features of the cerebellum, like the transverse fissures and splitting folds. The cortical surface area (median, 949 cm2 [IQR, 825-1021 cm2]) was 1.8 times larger, and the cortical thickness (median, 0.88 mm [IQR, 0.81-0.93 mm]) was five times thinner than previous in vivo estimates and closer to ex vivo reference data. Conclusion In vivo imaging of the cerebellar cortical layers and surface and derivation of quantitative measures was feasible in a clinically acceptable acquisition time with use of motion-corrected 7.0-T MRI. Published under a CC BY 4.0 license. Supplemental material is available for this article. See also the editorial by Dietrich in this issue.

Feasibility of flow-related enhancement brain perfusion MRI.

Brain perfusion imaging is of enormous importance for various neurological diseases. Fast gradient-echo sequences offering flow-related enhancement (FREE) could present a basis to generate perfusion-weighted maps. In this study, we obtained perfusion-weighted maps without contrast media by a previously described postprocessing algorithm from the field of functional lung MRI. At first, the perfusion signal was analyzed in fast low-angle shot (FLASH) and balanced steady-state free precession (bSSFP) sequences. Secondly, perfusion maps were compared to pseudo-continuous arterial spin labeling (pCASL) MRI in a healthy cohort. Thirdly, the feasibility of the new technique was demonstrated in a small selected group of patients with metastases and acute stroke. One participant was examined with bSSFP and FLASH sequences at 1.5T and 3T, different flip angles and slice thicknesses. Twenty-five volunteers had bSSFP imaging and pCASL MRI. Three patients with cerebral metastases and one with acute ischemic stroke had bSSFP imaging and were compared to T1 post-contrast images and CT perfusion. Frequency analyses, SNR and perfusion contrast were compared at different flip angles and slice thicknesses. Regional correlations and Sorensen-Dice overlap were calculated in the healthy cohort. Dice overlap of the pathologies in the patient cohort were calculated. The bSSFP sequence presented detectable perfusion signal within brain vessel and parenchyma together with superior SNR compared to FLASH. Perfusion contrast and its corticomedullary differentiation increased with flip angle. Mean regional correlation was 0.36 and highly significant between FREE maps and pCASL and grey and white matter Dice match were 72% and 60% in the healthy cohort. Pathologies presented good overlap between FREE perfusion-weighted and T1 post-contrast images. The feasibility of FREE brain perfusion imaging has been shown in a healthy cohort and selected patient cases with brain metastases and acute stroke. The study demonstrates a new approach for non-contrast brain perfusion imaging.

MR multitasking-based dynamic imaging for cerebrovascular evaluation (MT-DICE): Simultaneous quantification of permeability and leakage-insensitive perfusion by dynamic mapping.

To develop an MR multitasking-based dynamic imaging for cerebrovascular evaluation (MT-DICE) technique for simultaneous quantification of permeability and leakage-insensitive perfusion with a single-dose contrast injection. MT-DICE builds on a saturation-recovery prepared multi-echo fast low-angle shot sequence. The k-space is randomly sampled for 7.6min, with single-dose contrast agent injected 1.5min into the scan. MR multitasking is used to model the data into six dimensions, including three spatial dimensions for whole-brain coverage, a saturation-recovery time dimension, and a TE dimension for dynamic and quantification, respectively, and a contrast dynamics dimension for capturing contrast kinetics. The derived pixel-wise time series are converted into contrast concentration-time curves for calculation of kinetic metrics. The technique was assessed for its agreement with reference methods in and measurements in eight healthy subjects and, in three of them, inter-session repeatability of permeability and leakage-insensitive perfusion parameters. Its feasibility was also demonstrated in four patients with brain tumors. MT-DICE values of normal gray matter and white matter were in excellent agreement with reference values (intraclass correlation coefficients=0.860/0.962 for gray matter and 0.925/0.975 for white matter ). Both permeability and perfusion parameters demonstrated good to excellent intersession agreement with the lowest intraclass correlation coefficients at 0.694. Contrast kinetic parameters in all healthy subjects and patients were within the literature range. Based on dynamic mapping, MT-DICE allows for simultaneous quantification of permeability and leakage-insensitive perfusion metrics with a single-dose contrast injection.

Biomechanical Effects of Chronic Ankle Instability on the Talar Cartilage Matrix: The Value of T1ρ Relaxation Mapping Without and With Mechanical Loading.

T1ρ mapping has been proposed for the detection of early cartilage degeneration associated with chronic ankle instability (CAI). However, there are limited data surrounding the influence of ankle loading on T1ρ relaxation. To evaluate T1ρ relaxation times of talar cartilage, as an indicator of early degenerative changes, associated with CAI and to investigate the influence of acute axial in situ loading on T1ρ values in CAI patients and healthy controls. Prospective. A total of 9 patients (age=21.8 ± 2.5 years, male/female=2/7) with chronic ankle instability and 18 healthy control subjects (age=22.8 ± 3.6 years, male/female=5/13). 3 T. 3D gradient echo fast low-angle shot (FLASH) sequence augmented with a variable spin-lock preparation period. Ankle T1ρ mapping was performed without and with axial loading of 500 N. The talar cartilage was segmented in five coronal slices covering the central talocrural joint. Median talar T1ρ values were separately calculated for the medial and lateral facets. Mann-Whitney U and Wilcoxon signed-rank tests, significance level: P < 0.05. For the combined cohorts, the statistical analysis yielded significantly lower T1ρ values with loading compared to the no-load measurement for both the lateral (no load: [51.0 ± 4.0] msec, load: [49.5 ± 5.4] msec) as well as the medial compartment (no load: [50.0 ± 5.4] msec, load: [47.8 ± 6.8] msec). In the unloaded scans, the CAI patients showed significantly increased talar T1ρ values ([53.0 ± 7.4] mse ) compared to the healthy control subjects ([48.8 ± 4.1] msec) in the medial compartment. Increased talar T1ρ relaxation times in CAI patients compared to healthy controls suggest that T1ρ relaxation is a sensitive biomarker for CAI-induced early-stage cartilage degeneration. However, the load-induced T1ρ change did not prove to be a viable marker for the altered biomechanical properties of the hyaline talar cartilage. 2 LEVEL OF EFFICACY: Stage 2.

Spin Lattice (T1) and Magnetization Transfer Saturation (MTsat) Imaging to Monitor Age-Related Differences in Skeletal Muscle Tissue.

Background: The aim was to compare spin-lattice relaxation (T1) mapping from sequences with no fat suppression and three fat suppression methods and Magnetization Transfer Saturation (MTsat) mapping, to identify regional and age-related differences in calf muscle. These differences may be of clinical significance in age-related loss of muscle force. Methods: Ten young and seven senior subjects were imaged on a 3T MRI scanner using a 3D Fast Low Angle Shot sequence without and with different fat suppression and with MT saturation pulse. Bland–Altman plots were used to assess T1 maps using the fat unsuppressed sequence as the reference image. Age and regional differences in T1 and in MTsat were assessed using two-way factorial analyses of variance (ANOVAs) with Bonferroni-adjusted independent sample t-tests for post hoc analyses. Results: A significant age-related increase in T1 and decrease in MTsat was seen in the calf muscles. The largest size effect was observed in the T1 sequence with fat saturation. Conclusions: T1 increase with age may reflect increase in inflammatory processes while the decrease in MTsat may indicate that magnetization transfer may also be associated with muscle fiber macromolecules. T1 and MTsat maps of calf muscle have the potential to detect regional and age-related compositional differences in calf muscle.

Regional Left Ventricular Myocardial Injury and Function Characterisation by Cardiac Magnetic Resonance Imaging in a Sheep Model of Myocardial Infarction

Left ventricular (LV) remodelling following a myocardial infarction(MI) elicits different responses in infarct and remote LV, with prior studies reporting increased contractility in the latter. We explored the relationship between myocardial injury and its functional consequences using a combination of 3D late gadolinium enhancement (LGE), feature tracking (FT) cardiac magnetic resonance (CMR) and autopsy findings in a sheep model of MI. MI was induced in sheep (n=11) by coronary artery ligation under general anaesthesia. Baseline (pre-MI) and follow-up (15d post-MI) CMR exams were performed for cine imaging. LGE imaging was performed using a 3D inversion recovery fast low angle shot (IR-FLASH) sequence in the follow-up examination. MI size was confirmed at post-mortem. Regions of MI identified by imaging were compared with post-mortem findings using AHA LV segmentation. The sensitivity and specificity of the LGE imaging was calculated and compared to post-mortem using McNemar’s test. FT was applied to the cine imaging to quantify regional circumferential strain (CS). The percentage change in regional CS was calculated for each segment (Data: mean±SD; *p<0.05). LGE detected MI with a sensitivity of 90.6% and specificity of 96.4% (p=0.7). LV ejection fraction (EF) was 55.7±5.6% post-MI. Percentage changes in regional CS were -34.3±13.8% and -17.4±30.7% in AHA segments 13 and 16, respectively, while other segments exhibited increased CS (range=+0.1% to +28.7%). Our novel application of 3D IR-FLASH and FT provided comprehensive visualisation of LV injury and function in the setting of MI. Our data reproduces prior descriptions of compensatory increases in myocardial contractility in remote regions in STEMI patients with ≥50% EF [[1]Leung S.W. Ratajczak T.M. Abo-Aly M. Shokri E. Abdel-Latif A. Wenk J.F. Regional end-systolic circumferential strain demonstrates compensatory segmental contractile function in patients with ST-segment elevation myocardial infarction.J Biomech. 2021; 129 (110794)Crossref PubMed Scopus (1) Google Scholar] and a canine model of MI [[2]Lew W.Y. Chen Z.Y. Guth B. Covell J.W. Mechanisms of augmented segment shortening in nonischemic areas during acute ischemia of the canine left ventricle.Circ Res. 1985; 56: 351-358Crossref PubMed Scopus (112) Google Scholar].

Bone Marrow Fat Distribution in Patients With β-Thalassemia: A Study Using Chemical Shift-Based Water-Fat MRI

Molecular studies have shown the changes in bone marrow fat in relation to altered hematopoiesis. This study aims to investigate the changes in the bone marrow fat in patients affected by β-thalassemia by using chemical shift-encoded (CSE)-MRI. Twenty-three subjects, comprising of six healthy (17-31 years old) and 17 β-thalassemia subjects (19-39 years old), were scanned using a multiecho fast low angle shot sequence (0.94 × 0.94 × 3.00 mm3) and a stimulated echo acquisition mode sequence using 3T MRI. Bone marrow proton density fat fraction (PDFF) was quantified in the left femur of each subject. Regression and Bland-Altman analysis were used to analyze agreement between CSE-MRI and 1H-MRS. PDFF distribution was analyzed using Hartigan's dip test and the computed Wasserstein distances. Jonckheere-Terpstra trend analysis was performed to evaluate the effect of disease severity on PDFF distribution. An excellent agreement was found between PDFF measured using CSE-MRI with 1H-MRS (R2 = 0.91; bias =-1.41%). Healthy subjects showed left-skewed or bimodal PDFF distribution while β-thalassemia subjects showed bimodal, normal or right-skewed distribution. Jonckheere-Terpstra test shows that PDFF distribution was increasingly different from the norm as disease severity increased (TJT = 166.0, z = 3.806, p < 0.05). Increase in variability of PDFF distribution within each subject group was also seen with increasing disease severity (TJT = 169.0, z = 3.971, p < 0.05). CSE-MRI is a promising tool to demonstrate spatial changes and variability in marrow fat distribution, resulting from ineffective erythropoiesis.