Citations

ABSTRACT Background Magnetic resonance elastography (MRE) has demonstrated potential in characterizing intracranial tumors, including glioblastoma. The influence of pathology on measurement consistency and interobserver agreement needs evaluation to promote MRE implementation as a quantitative biomarker. Purpose To assess repeatability and interobserver agreement of absolute and normalized magnitude of the complex shear modulus (| G *|), storage modulus ( G ′), and loss modulus ( G ″) in glioblastoma. Study Type Prospective. Population Thirteen adults (5 male, 8 female, mean age 66.23 years) with histopathologically confirmed glioblastoma. Field Strength/Sequence 3 T MRI, modified single‐shot spin‐echo echo‐planar imaging. Assessment Two same‐session MRE acquisitions were performed with patient repositioning. The solid tumor component was independently segmented by 2 observers on contrast‐enhanced T1‐weighted images co‐registered to MRE maps. Statistical Tests Repeatability was assessed using the repeatability coefficient, coefficient of variation, and Bland–Altman plots, and interobserver agreement by the intraclass correlation coefficient. The Wilcoxon signed‐rank test compared parameters and coefficients of variation between tumor‐normal‐appearing white matter and absolute and normalized measurements. Significance was set at 0.05. Results Tumor | G *| and G ′ showed repeatability coefficients of 0.07–0.08 kPa and 0.05 kPa, compared with 0.13 kPa (| G *|) and 0.15–0.16 kPa ( G ′) for normalized measurements. Coefficients of variation in tumor regions were 1.42% ± 1.12%–1.60% ± 1.41% for | G *| and 1.19% ± 0.96%–2.08% ± 2.22% for G ′, significantly lower than normalized values (4.82% ± 4.49%–4.21% ± 4.27% for | G *|; 5.12% ± 5.04%–5.45% ± 4.53% for G ′). Tumor | G *| and G ′ showed excellent interobserver agreement (intraclass correlation coefficients 0.97 and 0.95). Tumor G ″ demonstrated higher variability than | G *| and G ′ (coefficients of variation 8.58% ± 7.69%–7.51% ± 6.73%), with no significant difference between absolute and normalized measurements ( p = 0.14). Data Conclusion Tumor | G *| and G ′ are the most repeatable metrics in glioblastoma. Normalization reduces measurement repeatability due to normal‐appearing white matter variability. The small sample size ( n = 13) limits generalizability. Evidence Level 2. Technical Efficacy Stage 2.

Abstract Background Flow‐related ghost artifact from a 3D Magnetization Prepared Rapid Gradient Echo (MPRAGE) sequence results from unsaturated magnetization of incoming arterial flow. This is especially common on MR scanners equipped with smaller radiofrequency (RF) transmit coils. A high‐performance compact 3T (C3T) scanner features a smaller RF‐transmit coil (inner diameter 37 cm, length 40 cm), leading to a rapid fall‐off of the B1 field below the neck. This configuration results in more intense flow‐related ghost artifacts, especially in younger patients. Purpose The C3T scanner's smaller RF‐transmit coil provides RF field coverage over the brain region, causing bright in‐flow arterial signals and flow‐related artifacts in the conventional 3D‐MPRAGE scans. The purpose of this study is to suppress these artifacts by adding a RF saturation band (RFSB) pulses to the 3D‐MPRAGE sequence. Methods The RFSB was added to the 3D‐MPRAGE sequence as a preparation pulse option. To test the effectiveness, 37 subjects were scanned on the C3T under an IRB‐approved protocol using 3D‐MPRAGE with and without RFSB. Ten of those subjects underwent repeated scans with and without RFSB to evaluate test‐retest reliability. A consensus evaluation by two neuroradiologists was performed on all data to compare signal to noise ratio, image contrast, presence of artifacts, and diagnostic confidence. Quantitative analysis included calculating test‐retest differences by image subtraction and evaluating the variance in flow‐artifact‐induced image intensity between the scans with and without RFSB. Additionally, one subject was scanned on a whole‐body 3T scanner using a transmit/receive (T/R) head coil to demonstrate the method's applicability across different MRI platforms as a proof of concept. Results The Wilcoxon signed‐rank test of the neuroradiologist evaluations showed a significant reduction in artifacts and an improvement in diagnostic confidence in the posterior fossa region with and without RFSB ( p < 0.0001). Test–retest analysis showed that adding RFSB significantly reduced image intensity variability in the cerebellum, even among subjects without visible flow artifacts. The normalized difference decreased from 8.71% to 6.41% ( p = 0.0059), suggesting improved image reliability in regions prone to flow‐related artifacts. Additionally, similar findings were observed in scans on a whole‐body 3T with a T/R head coil, demonstrating the broader applicability of this method. Conclusion Incorporating RFSB into 3D‐MPRAGE scans effectively reduces flow‐related ghost artifact on the C3T scanner, improving image quality and diagnostic confidence. These findings suggest that the proposed method could be widely implemented across MRI systems utilizing a smaller RF‐transmit coil.

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.

Recent advancements in compact MRI scanners, portable low-field-strength MRI systems, and high-performance gradient inserts address the challenges of conventional MRI for brain imaging, providing more accessible and versatile technology.

BACKGROUND: Spinal cord involvement is infrequently reported in primary central nervous system vasculitis (PCNSV). This study describes the clinical findings, therapeutic responses, and outcomes of spinal cord involvement in a large cohort of patients with PCNSV. METHODS: We retrospectively studied 216 consecutive patients with PCNSV evaluated at the Mayo Clinic from 1983 to 2023. Spinal cord involvement was documented by histological examination or imaging. The clinical, laboratory, radiological, and pathological findings, along with management and outcomes, were compared between patients with and without spinal cord involvement. RESULTS: Of 216 patients, 10 (4.6%) had spinal cord involvement, with cerebral involvement in 9 cases. One patient (0.5%) had isolated spinal cord vasculitis. Histological evidence of vasculitis was found in all 10, with necrotizing vasculitis in 5 (50%). Magnetic resonance imaging showed thoracic abnormalities in 8 patients, cervical spine involvement in 2, conus medullaris involvement in 3, and cauda equina enhancement in 4. Compared with the 206 patients without spinal cord involvement, those with spinal cord vasculitis were more likely to present with paraparesis/tetraparesis ( P <0.001) and necrotizing vasculitis ( P =0.01) and less likely with hemiparesis ( P =0.006) and granulomatous vasculitis ( P =0.03). Patients with spinal cord involvement were more likely to have at least 1 relapse ( P <0.001) or more ( P <0.001). No differences between the 2 groups were observed regarding long-term remission, therapy response, and high disability scores (modified Rankin Scale score, 4–6) or death at last follow-up. Spinal cord involvement was associated with meningeal enhancement on brain imaging (odds ratio, 10.50) and the presence of lymphoma (odds ratio, 6.49), specifically Hodgkin lymphoma diagnosed simultaneously with PCNSV. Spinal involvement was negatively associated with increasing age (odds ratio, 0.64) and cerebral infarction on imaging (odds ratio, 0.08). CONCLUSIONS: Spinal cord involvement defines a distinct subset of patients with PCNSV.

Background: Previous reports have established a relationship between asymptomatic high-grade carotid artery stenosis (CAS) and impaired cognition. Different forms of cardiac disease have also been associated with cognitive impairment and dementia. The effect of concurrent high-grade CAS and cardiac disease on cognition is unknown. We hypothesize the presence of comorbid cardiac disease has a synergistic effect on cognitive impairment in patients with asymptomatic CAS. Methods: Patients with ≥80% internal carotid artery stenosis with no history of stroke were recruited from inpatient and outpatient practices at a single, large, comprehensive stroke center. Patients with vs without comorbid cardiac disease (coronary artery disease [CAD], CAD with history of coronary artery bypass graft [CABG] or percutaneous intervention [PCI], heart failure [HF], atrial fibrillation [AF], or valvular disease [aortic or mitral]) were identified. Cognitive assessments were performed using a battery of 14 standardized tests of attention, memory, processing speed, visual construction, language and executive function. Z-scores were generated based on age-specifc norms. Multivariable linear regression was used to compare test-specific Z-scores in patients with vs without cardiac disease controlling for age, sex, years of education and depression. Results: Thirty-three patients with asymptomatic CAS were identified (21 males, age 74+/-10 years, education=16+/-3 years). Twenty-six (79%) had cardiac disease. Patients with comorbid cardiac disease had significantly lower Z-scores across multiple tests of memory compared to patients without cardiac disease (Fig). After adjusting for age, sex, years of education and depression, significant differences persisted in tests of memory in patients with CAD [Hopkins Recognition Memory Test, β= -1.127 (95% CI: -2.234, -0.020), P=0.046], CABG [Hopkins Learning Trial Memory Test, β= -1.441 (95% CI: -2.532, -0.350), P=0.012], and valvular disease [Hopkins Learning Trials Memory Test, β= -1.121 (95% CI: -2.224, -0.018), P=0.047]. Conclusion: Cardiac disease is common among patients with asymptomatic high-grade carotid stenosis and may have a synergistic effect on impairments in memory in a manner not mediated by stroke. Further work is needed to confirm these relationships and their longterm implications on vascular brain health.

AbstractBackgroundSleep’s crucial role in maintaining brain health is increasingly recognized, particularly due to the rising prevalence of neurodegenerative diseases. It not only supports cognitive function but also aids in clearing brain metabolic waste through cerebrospinal fluid (CSF) dynamics. During sleep, especially in the non‐rapid eye movement (NREM) phase, CSF flow increases, essential for removing neurotoxic substances like amyloid‐beta proteins. This study explores the link between sleep respiratory patterns and CSF flow promotion.MethodElectroencephalography (EEG), and functional magnetic resonance imaging (fMRI) were simultaneously acquired during sleep from Gu, et al. (n = 29) (Gu et al. 2022). Respiration, measured via a respiratory belt, calculated respiratory volume (RV) as the standard deviation within a 5 second sliding window. EEG data processed delta band power (1‐4Hz) averaged across channels. Parcellated fMRI data using the brain template followed by the calculation of the averaged gray matter (GM) blood‐oxygen‐level‐dependent (BOLD) signal using the GM mask. CSF inflow was manually extracted from the fMRI’s bottom slice at the foramen magnum level. Subsequently, all signals were temporally aligned to the peak of the CSF inflow signal.ResultAt the time of CSF inflow (time = 0 sec. in the Figure 1A‐D), we observed an earlier increase in RV and EEG delta power, followed by changes in the GM BOLD signal (Figure 1). EEG and RV changes preceded the BOLD signal changes, which, in turn, preceded changes in CSF flow. Sensitivity to detect RV involvement during MRI varied with the placement of the respiratory belt, being least sensitive on the chest and more on the abdomen.ConclusionThese findings raise an interesting question on the role respiratory patterns during sleep, particularly in the NREM phase. Speculatively, RV change may influence CSF circulation during NREM sleep (Figure 1E). This enhancement in CSF flow is crucial for the clearance of metabolic waste from the brain, potentially reducing the risk of neurodegenerative diseases. Our findings indicate that respiratory volume may serve as a significant marker for CSF circulation during sleep.