Ehman, Richard L.

ABSTRACTBackgroundPercutaneous transluminal angioplasty and stenting (PTAS) in patients with carotid stenosis may have potential effects on brain parenchyma. However, current studies on parenchymal changes are scarce due to the need for advanced imaging modalities. Consequently, the alterations in brain parenchyma following PTAS remain an unsolved issue.PurposeTo investigate changes to the brain parenchyma using magnetic resonance elastography (MRE).Study TypeProspective.Population13 patients (6 women and 7 men; 39 MRI imaging sessions) with severe unilateral carotid stenosis patients indicated for PTAS were recruited between 2021 and 2024.Field Strength/SequenceNoncontrast MRI sequences including MRE (spin echo) were acquired using 3 T scanners.AssessmentAll patients underwent MRE before (preprocedural), within 24 h (early postprocedural) and 3 months after (delayed postprocedural) PTAS. Preprocedural and delayed postprocedural ultrasonographic peak systolic velocity (PSV) was recorded. MRE stiffness and damping ratio were evaluated via neural network inversion of the whole brain, in 14 gray matter (GM) and 12 white matter (WM) regions.Statistical TestsStiffness and damping ratio differences between each pair of MR sessions for each subject were identified by paired sample t tests. The correlations of stiffness and damping ratio with stenosis grade and ultrasonographic PSV dynamics were evaluated by Pearson correlation coefficients. The statistical significance was defined as p < 0.05.ResultsThe stiffness of lesion side insula, deep GM, and deep WM increased significantly from preprocedural to delayed postprocedural MRE. Increasing deep GM stiffness on the lesion side was positively correlated with the DSA stenosis grade significantly (r = 0.609). The lesion side insula stiffness increments were positively correlated with PSV decrements significantly (r = 0.664).Data ConclusionRegional brain stiffness increased 3 months after PTAS. Lesion side stiffness was positively correlated with stenosis grades in deep GM and PSV decrements in the insula.Evidence Level2.Technical EfficacyStage 2.

AbstractPurposeWhile standard MR elastography (MRE) uses harmonic mechanical waves, there are some applications in which imaging and analysis of transient mechanical motion are of interest. Wavelet MRE has been developed for detecting broadband motion from transient excitation. The goal of this study was to evaluate the accuracy and efficiency of wavelet MRE for transient displacement detection in brain MRE applications.MethodsTransient motion was induced in a gel phantom, while MRE images were acquired using bipolar motion‐encoding gradient (MEG) at multiple frequencies (20–200 Hz). Displacements were estimated using (1) combinations of multiple MEGs forming the wavelet MRE and (2) deconvolution from a single MEG. These estimated displacements were used to calculate the MRE phase for each MEG. Correlation (r2) between the calculated and acquired phases was evaluated.Three healthy volunteers were scanned twice in a clinical scanner using wavelet MRE with an occipital impact. Time‐resolved brain translation, rotation, and maximal principal strain were calculated. Repeatability was assessed both qualitatively and through Pearson correlation.ResultsWavelet MRE outperformed standard MRE in displacement estimation, showing higher correlations between calculated and acquired phase, even with fewer phase offsets. In the volunteer study, consistent temporal motion dynamics and spatial maximal principal strain distributions across repeated scans demonstrated the repeatability of wavelet MRE.ConclusionThis study validated the accuracy and efficiency of wavelet MRE for broadband motion detection and demonstrated its feasibility and repeatability in vivo. This technique shows promise for advancing our understanding of the injury risks and mechanisms associated with sports‐related head trauma.

Spatial heterogeneity of liver viscoelasticity, measured at three-dimensional vector MR elastography, positively correlated with metabolic dysfunction–associated steatotic liver disease progression.

Background and Aims: Screening for diseases can have psychological impacts, such as anxiety, and requires acceptability from the population to be effective. This study examined the perspectives on the benefits and harms of screening for metabolic dysfunction–associated steatotic liver disease (MASLD) among the general population to optimize screening practices. Approach and Results: A survey was sent to participants enrolled between 2020 and 2024 in a prospective MASLD screening study in Olmsted County, MN. The survey assessed participants' perceived anxiety, stigma, quality of life, preferred screening methods, financial concerns, and lifestyle impacts following screening and diagnosis. Of the 461 participants, 342 (74%) completed the survey. Overall, 14% of participants reported screening-related anxiety, and 14% were concerned about disclosing a potential MASLD diagnosis to others. Among those without a MASLD diagnosis, 99% felt reassured about their liver health, 48% reported an improved quality of life, and 25% made lifestyle changes pertaining to their diet, alcohol use, and physical activity. Of the 77 participants diagnosed with MASLD, 52% experienced some anxiety about their new diagnosis; however, 95% and 97% considered it important to receive an early MASLD diagnosis to mitigate the risk for cirrhosis and cardiovascular disease, respectively. Notably, 79% of diagnosed participants found the diagnosis beneficial in adopting healthier habits, with 30% achieving a >10% weight loss after screening. Conclusion: This population-based survey demonstrates that the perceived benefits of proactive MASLD screening, such as increased awareness, lifestyle changes, and early diagnosis, outweigh the harms. These findings highlight the importance of early screening through patient-centered protocols to improve health outcomes.

Abstract Purpose To evaluate the test–retest repeatability of a rapid, free‐breathing two‐dimensional (2D) MR elastography (MRE) technique and to assess the reliability of the liver‐stiffness measurements compared with conventional breath‐hold MREs. Methods Fifteen and 115 participants were enrolled in the technical repeatability and measurement equivalence assessment cohorts, respectively. All participants underwent rapid free‐breathing and conventional breath‐hold 2D MRE (twice in repeatability cohort) on 1.5T scanners. Both methods have four phase offsets over one harmonic motion cycle at 60 Hz; one and 10 cycles were collected and processed in breath‐hold and free‐breathing MREs, respectively. The liver stiffness measurements of free‐breathing (LS F ) and breath‐hold MRE (LS B ) were calculated from manually drawn regions of interest. The repeatability coefficients and Spearman correlation were used to assess technical repeatability and measurement agreement between LS F and LS B . Univariable and multivariable linear regressions were performed to identify potential influencing factors, including age, sex, body mass index, and fat fraction, in the measurement agreement between LS B and LS F . Results The repeatability coefficient of free‐breathing 2D MRE is comparable to breath‐hold MRE (LS F : 20.8%, LS B : 20.4%). LS F showed a strong agreement and significant correlation with LS B (LS F = 1.01 × LS B , ρ = 0.94, p < 0.001). The measurement agreement between LS F and LS B was only significantly affected by sex ( p = 0.047) after adjusting for confounding factors of age, body mass index, and fat fraction. Conclusions The nongated, free‐breathing, multislice 2D MRE technique can provide reliable liver stiffness measurements compared with conventional breath‐hold 2D MRE. It could provide a comfortable alternative method with reliable liver stiffness measurements for patients who have difficulty in suspending respiration.

BackgroundMR elastography (MRE) at 60 Hz is widely used for staging liver fibrosis. MRE with lower frequencies may provide inflammation biomarkers.PurposeTo establish a practical simultaneous dual‐frequency liver MRE protocol at both 30 Hz and 60 Hz during a single examination and validate the occurrence of second harmonic waves at 30 Hz.Study TypeRetrospective.SubjectsOne hundred six patients (48 females, age: 50.0 ± 13.4 years) were divided as follows: Cohort One (15 patients with chronic liver disease [CLD] and 25 healthy volunteers) with simultaneous dual‐frequency MRE. Cohort Two (66 patients with CLD) with second harmonic MRE.Field Strength/Sequence3‐T, single‐ or dual‐frequency MRE at 30 Hz and 60 Hz.AssessmentLiver stiffness (LS) in both cohorts was evaluated with manually placed volumetric ROIs by two independent analyzers. Image quality was assessed by three independent readers on a 4‐point scale (0–3: none/failed, fair, moderate, excellent) based on the depth of wave propagation with 1/3 incremental penetration. The success rate was derived from the percentage of nonzero quality scores.Statistical TestsMeasurement agreement, bias, and repeatability of LS were assessed using intraclass correlation coefficients (ICCs), Bland–Altman plots, and repeatability coefficient (RC). Mann–Whitney U tests were used to evaluate the differences in image quality between different methods. A P‐value <0.05 was considered statistically significant.ResultsSuccess rate was 97.5% in Cohort One and 91% success rate for the second harmonic MRE in Cohort Two. The second harmonic and conventional MRE showed excellent agreement in LS (all ICCs >0.90). The quality scores for the second harmonic wave images were lower than those from the conventional MRE (Z = −4.523).Data ConclusionCompared with conventional and second harmonic methods, simultaneous dual‐frequency had better image quality, high success rate and the advantage of intrinsic co‐registration, while the second harmonic method can be an alternative if custom waveform is not available.Evidence Level3Technical EfficacyStage 1