Gradient-recalled Echo Magnetic Resonance Research Articles

Cerebral microbleeds in acute ischemic stroke after intravenous thrombolysis and their impact on short term outcome of stroke

Objectives Strong evidence suggests the occurrence of cerebral microbleeds (CMBs) in 5–13% of stroke patients within the first week after stroke onset. The aim of this work was to study risk factors associated with occurrence of CMBs in patients with stroke who received intravenous thrombolysis, and to clarify their impact on the clinical outcome. Methods This prospective observational study was conducted on 61 acute ischemic stroke patients eligible for treatment with recombinant tissue plasminogen activator (rt-PA). Assessment of stroke-related neurologic deficit was done using National Institute of Health Stroke Scale (NIHSS). Assessment of stroke related disability after 3 months from stroke onset was done using Modified Rankin Scale (mRS). CMBs were detected by T2*-weighed gradient-recalled echo (T2*-GRE) and susceptibility-weighted imaging (SWI) magnetic resonance imaging (MRI) sequences. Results There was a statistically significant impact of age, mean arterial pressure (MAP) at stroke onset, history of hypertension (HTN), and white matter changes assessed by Fazekas scale on the occurrence of CMBs in the included stroke patients (P-value= 0.002, <0.001, <0.001, 0.008 respectively). There was no statistically significant difference between patients with favorable and those with unfavorable outcome regarding the total number of CMBs (P-value =0.542). There was also no statistically significant difference between patients who developed complications from rt-PA and those who didn’t develop regarding the total number of CMBs (P-value =0.186). Conclusion Cerebral microbleeds are more likely to occur in older stroke patients and in those who had high MAP at stroke onset, history of HTN, and white matter changes.

Quantitative MRI identifies lesional and non-lesional abnormalities in MOGAD.

Myelin oligodendrocyte glycoprotein antibody-associated disease (MOGAD) is a distinct central nervous system (CNS) disorder that shares features with multiple sclerosis (MS) and may be misdiagnosed as MS. MOGAD and MS share a frequently relapsing clinical course and lesions with inflammatory demyelinating pathology. One key feature of MS pathology is tissue damage in normal-appearing white matter (NAWM) outside of discrete lesions, whereas the extent to which similar non-lesional damage occurs in MOGAD is not known and could be assessed using qGRE. The goal of this study was to examine the brains of people with MOGAD using quantitative gradient-recalled echo (qGRE) magnetic resonance imaging and to compare tissue damage with MS patients matched for disability. MOGAD and MS patients were recruited to match in terms of age and disability. Similarly aged healthy control (HC) data were drawn from existing studies. qGRE brain imaging of HC (N=15), MOGAD (N=17), and MS (N=15) patients was used to examine the severity and extent of tissue damage within and outside of discrete lesions. The qGRE metric R2t* is sensitive to changes in tissue microstructure and was measured in white matter lesions (WMLs), NAWM, cortical (CGM) and deep gray matter (DGM). Statistical inference was performed with linear models. R2t* was reduced in CGM (p=0.00047), DGM (p=0.0055) and NAWM (p=0.0019) in MOGAD and MS compared to similar regions in age-matched HCs. However, the degree of R2t* reduction in all these regions was less in the MOGAD patients compared with MS. WMLs in MOGAD demonstrated reduced R2t* compared to NAWM but this reduction was modest compared to changes associated with WMLs in MS (p=0.026). These results demonstrate abnormalities in lesional and non-lesional CNS tissues in MOGAD that are not detectable on standard MRI. The abnormalities seen in NAWM, CGM, and DGM were less severe in MOGAD compared to MS. MOGAD-related WMLs showed reduced R2t*, but were less abnormal than WMLs in MS. These data reveal damage to non-lesional tissues in two different demyelinating diseases, suggesting that damage outside of WMLs may be a common feature of demyelinating diseases. The lesser degree of R2t* abnormality in MOGAD tissues compared to MS suggests less underlying tissue damage and may underlie the greater propensity for recovery in MOGAD.

Deep learning-based Accelerated and Noise-Suppressed Estimation (DANSE) of quantitative Gradient-Recalled Echo (qGRE) magnetic resonance imaging metrics associated with human brain neuronal structure and hemodynamic properties.

The purpose of the current study was to introduce a Deep learning-based Accelerated and Noise-Suppressed Estimation (DANSE) method for reconstructing quantitative maps of biological tissue cellular-specific, R2t*, and hemodynamic-specific, R2', metrics of quantitative gradient-recalled echo (qGRE) MRI. The DANSE method adapts a supervised learning paradigm to train a convolutional neural network for robust estimation of R2t* and R2' maps with significantly reduced sensitivity to noise and the adverse effects of macroscopic (B0 ) magnetic field inhomogeneities directly from the gradient-recalled echo (GRE) magnitude images. The R2t* and R2' maps for training were generated by means of a voxel-by-voxel fitting of a previously developed biophysical quantitative qGRE model accounting for tissue, hemodynamic, and B0 -inhomogeneities contributions to multigradient-echo GRE signal using a nonlinear least squares (NLLS) algorithm. We show that the DANSE model efficiently estimates the aforementioned qGRE maps and preserves all the features of the NLLS approach with significant improvements including noise suppression and computation speed (from many hours to seconds). The noise-suppression feature of DANSE is especially prominent for data with low signal-to-noise ratio (SNR ~ 50-100), where DANSE-generated R2t* and R2' maps had up to three times smaller errors than that of the NLLS method. The DANSE method enables fast reconstruction of qGRE maps with significantly reduced sensitivity to noise and magnetic field inhomogeneities. The DANSE method does not require any information about field inhomogeneities during application. It exploits spatial and gradient echo time-dependent patterns in the GRE data and previously gained knowledge from the biophysical model, thus producing high quality qGRE maps, even in environments with high noise levels. These features along with fast computational speed can lead to broad qGRE clinical and research applications.

Atrial cardiopathy is associated with cerebral microbleeds in ischemic stroke patients

ObjectiveCerebral microbleeds (CMB) are small accumulations of hemosiderin associated with cerebrovascular risk factors, but whether they are associated with atrial cardiopathy is not known. The goal of this study is to determine, among ischemic stroke patients, the association between study-defined atrial cardiopathy and CMB presence, location, and number.MethodsIschemic stroke patients admitted to Johns Hopkins (2015–2019) with transthoracic echocardiography and electrocardiography were included. Cerebral microbleeds were defined as small, round hypo-intensities on T2* susceptibility weighted imaging or gradient recalled echo magnetic resonance imaging sequences. Atrial cardiopathy was defined as the presence of ≥1: left atrium diameter >4.0 cm (males) or >3.8 cm (females), PR interval >200 ms, or N-terminal pro-B-type natriuretic peptide >250 pg/ml. Binary/Ordinal logistic regression models were used to determine the association between atrial cardiopathy, and cerebral microbleed presence, location (lobar/deep), or number, each, adjusted for potential confounders.ResultsPatients (N = 120) were mean age 60 years (range 22–98), 46% female, 62% black, and 39% were on anti-thrombotic medication at time of admission. 39 (32%) participants had ≥1 cerebral microbleeds. Forty-six (38%) patients had atrial cardiopathy. Atrial cardiopathy was associated with higher odds of having cerebral microbleeds (OR 2.50, 95% CI 1.02–6.15). Atrial cardiopathy was associated with lobar cerebral microbleeds (OR 2.33, 95% CI 1.01–5.37) in univariate analysis but not with deep cerebral microbleeds (OR 0.45, 95% CI 0.13–1.54), with neither association significant after adjustment. There was no difference in risk of having 1 vs. no cerebral microbleeds (RRR 2.51, 95% CI 0.75–8.37) and >1 cerebral microbleed vs none (RRR 2.57, 95% CI 0.87–7.60) among those with atrial cardiopathy.ConclusionsAtrial cardiopathy is associated with the presence, but not burden, of cerebral microbleeds in ischemic stroke patients. We cautiously suggest that atrial cardiopathy, either directly or through shared vascular risk, may contribute to the presence of CMB.

Comparison of spin-echo echo-planar imaging magnetic resonance elastography with gradient-recalled echo magnetic resonance elastography and their correlation with transient elastography

PURPOSE This study aimed to assess the agreement between liver stiffness (LS) values obtained by the gradient-recalled echo (GRE) magnetic resonance elastography (MRE) and spin-echo echo-planar imaging (SE-EPI) MRE with those of transient elastography (TE), respectively. METHODS We retrospectively included 48 participants who underwent liver MRE with both GRE and SE-EPI sequences in the same session and also TE within 1 year. We obtained LS values for MRE by drawing free-hand region of interest, and TE was performed using a FibroScan device. We assessed the relationship between the mean LS values obtained by each MRE sequence and TE using the correlation coefficients and Bland-Altman plots, respectively. We also compared LS values and technical failure rates of measured values from MRE between SE-EPI and GRE sequences using the paired t-test and McNemar's test. The MRE failure was defined as the absence of pixel value with a confidence index above 95%. RESULTS The LS values from SE-EPI and GRE sequences strongly correlated with those from TE (GRE; r = 0.73, P < .001 vs. SE-EPI; r = 0.79, P < .001). In addition, the LS values from the 2 MRE sequences showed excellent relationship (intraclass correlation coefficient, 0.94 [0.89-0.97], P < .001). The LS values from SE-EPI and GRE MRE were not significantly different (4.14 kPa vs. 3.88 kPa, P = .19). Furthermore, the technical success rate of SE-EPI MRE was superior to that of GRE (100% vs. 83.8%, P = .031). CONCLUSION The measured LS values obtained using TE correlated strongly with those obtained using GRE and SE-EPI MRE techniques, even though SE-EPI-MRE resulted a higher technical success rate than GRE-MRE. Therefore, we believe that TE, GRE, and SE-EPI MR elastography techniques may complement each other according to the appropriate individual situation.

Cerebral Microbleeds: Relationship to Antithrombotic Medications.

Cerebral microbleeds (CMBs) are represented by small areas of hemosiderin deposition, detected on brain magnetic resonance imaging (MRI), and found in ≈23% of the cognitively normal population over age of 60 years. CMBs predict risk of hemorrhagic and ischemic stroke. They correlate with increased cardiovascular mortality. In this article, we sought to determine in a population-based study whether antithrombotic medications correlate with CMBs and, if present, whether the association was direct or mediated by another variable. The study consisted of 1253 participants from the population-based Mayo Clinic Study of Aging who underwent T2* gradient-recalled echo magnetic resonance imaging. We tested the relationship between antithrombotic medications and CMB presence and location, using multivariable logistic-regression models. Ordinal logistic models tested the relationship between antithrombotics and CMB frequency. Using structural equation models, we assessed the effect of antithrombotic medications on presence/absence of CMBs and count of CMBs in the CMB-positive group, after considering the effects of age, sex, vascular risk factors, amyloid load by positron emission tomography, and apoE. Two hundred ninety-five participants (26.3%) had CMBs. Among 678 participants taking only antiplatelet medications, 185 (27.3%) had CMBs. Among 95 participants taking only an anticoagulant, 43 (45.3%) had CMBs. Among 44 participants taking an anticoagulant and antiplatelet therapy, 21 (48.8%) had CMBs. Anticoagulants correlated with the presence and frequency of CMBs, whereas antiplatelet agents were not. Structural equation models showed that predictors for presence/absence of CMBs included older age at magnetic resonance imaging, male sex, and anticoagulant use. Predictors of CMB count in the CMB-positive group were male sex and amyloid load. Anticoagulant use correlated with presence of CMBs in the general population. Amyloid positron emission tomography correlated with the count of CMBs in the CMB-positive group.

Prevalence and Heterogeneity of Cerebrovascular Disease Imaging Lesions

ObjectiveTo report population age-specific prevalence of core cerebrovascular disease lesions (infarctions, cerebral microbleeds, and white-matter hyperintensities detected with magnetic resonance imaging); estimate cut points for white-matter hyperintensity positivity; investigate sex differences in prevalence; and estimate prevalence of any core cerebrovascular disease features. Patients and MethodsParticipants in the population-based Mayo Clinic Study of Aging aged 50 to 89 years underwent fluid-attenuated inversion recovery and T2* gradient-recalled echo magnetic resonance imaging to assess cerebrovascular disease between October 10, 2011, and September 29, 2017. We characterized each participant as having infarct, normal versus abnormal white-matter hyperintensity, cerebral microbleed, or a combination of lesions. Prevalence of cerebrovascular disease biomarkers was derived through adjustment for nonparticipation and standardization to the population of Olmsted County, Minnesota. ResultsAmong 1462 participants without dementia (median [range] age, 68 [50 to 89] y; men, 52.7%), core cerebrovascular disease features increased with age. Prevalence (95% CI) of cerebral microbleeds was 13.6% (11.6%-15.6%); infarcts, 11.7% (9.7%-13.8%); and abnormal white-matter hyperintensity, 10.7% (8.7%-12.6%). Infarcts and cerebral microbleeds were more common among men. In contrast, abnormal white-matter hyperintensity was more common among women ages 60 to 79 y and men, ages 80 y and older. Prevalence of any core cerebrovascular disease feature determined by presence of at least one cerebrovascular disease feature increased from 9.5% (ages 50 to 59 y) to 73.8% (ages 80 to 89 y). ConclusionWhereas this study focused on participants without dementia, the high prevalence of cerebrovascular disease imaging lesions in elderly persons makes assignment of clinical relevance to cognition and other downstream manifestations more probabilistic than deterministic.

Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging

Purpose To develop and characterize a tissue-mimicking phantom that enables the direct comparison of magnetic resonance (MR) and ultrasound (US) imaging techniques useful for monitoring high-intensity focused ultrasound (HIFU) treatments. With no additions, gelatin phantoms produce little if any scattering required for US imaging. This study characterizes the MR and US image characteristics as a function of psyllium husk concentration, which was added to increase US scattering. Methods Gelatin phantoms were constructed with varying concentrations of psyllium husk. The effects of psyllium husk concentration on US B-mode and MR imaging were evaluated at nine different concentrations. T1, T2, and T2* MR maps were acquired. Acoustic properties (attenuation and speed of sound) were measured at frequencies of 0.6, 1.0, 1.8, and 3.0 MHz using a through-transmission technique. Phantom elastic properties were evaluated for both time and temperature dependence. Results Ultrasound image echogenicity increased with increasing psyllium husk concentration while quality of gradient-recalled echo MR images decreased with increasing concentration. For all phantoms, the measured speed of sound ranged between 1567–1569 m/s and the attenuation ranged between 0.42–0.44 dB/(cm·MHz). Measured T1 ranged from 974–1051 ms. The T2 and T2* values ranged from 97–108 ms and 48–88 ms, respectively, with both showing a decreasing trend with increased psyllium husk concentration. Phantom stiffness, measured using US shear-wave speed measurements, increased with age and decreased with increasing temperature. Conclusions The presented dual-use tissue-mimicking phantom is easy to manufacture and can be used to compare and evaluate US-guided and MR-guided HIFU imaging protocols.

Normal Glenoid Ossification in Pediatric and Adolescent Shoulders Mimics Bankart Lesions: A Magnetic Resonance Imaging–Based Study

The purpose of this descriptive study was to define patterns of ossification and fusion of growth centers around the pediatric and adolescent glenoid as a function of age using 3-dimensional, frequency-selective, fat-suppressed spoiled gradient recalled echo magnetic resonance (MR) imaging sequences, with a particular focus on the anterior glenoid rim because of its clinical relevance as a potential confounder of glenohumeral instability. Picture Archiving and Communication System records at an urban academic tertiary care orthopaedic facility from October 2005 to December 2018 were queried for shoulder MRI in patients aged 9 to 17years. Patients were excluded if they had any diagnoses that could alter glenoid development. All images were independently evaluated by a musculoskeletal fellowship-trained radiologist. Secondary ossification centers were characterized as cartilage anlage, ossified, or fused at 3 anatomic sites: the anterior glenoid rim, coracoid, and superior glenoid rim. A total of 250MR examinations (143 males, 107 females) were assessed in this study. The glenoid develops in a predictably sequential manner with ossification at the anterior glenoid rim lagging behind the coracoid and superior glenoid rim. The earliest age of anterior glenoid rim ossification was 11years for both males (range 11-17) and females (range 11-12). Anterior glenoid rim ossification peaked at age 16 among males (34.8%, 8/23) and age 11 among females (27.3%, 3/11). Glenoid ossification and fusion progress in a predictable and chronological manner. This pattern should be used as a guideline when interpreting pediatric shoulder MRI examinations. In particular, an anterior glenoid ossification center should not be confused with an anterior glenoid injury (e.g., Bankart lesion), particularly in males 11 to 17years old and females 11 to 12years old. IV (case series).

Gadolinium contrast medium administration does not adversely affect T2*-weighted gradient recalled echo magnetic resonance imaging of the canine brain at 1.5 Tesla.

As gadolinium-based contrast agents are paramagnetic and have T2 shortening effects, they have the potential to adversely affect gradient recalled echo sequences. The aim of this prospective, cross-sectional study was to evaluate the effects of gadolinium administration on T2*-weighted sequence diagnostic quality and signal intensity when imaging the canine brain. A total of 100 dogs underwent brain magnetic resonance imaging (MRI) including pre- and postcontrast T2*-weighted sequences acquired with a delay (Group A) or immediately (Group B) following gadolinium administration. Pre- and postcontrast images were subjectively compared. In dogs with intracranial enhancing masses, regions of interest were drawn on corresponding images and signal intensity ratios were calculated. The effect of degree and pattern of contrast enhancement, susceptibility artifacts, and time between contrast injection and T2*-weighted sequence acquisition on signal intensity ratio was evaluated. Overall 31 dogs had contrast enhancing intracranial masses. Subjectively, there was no difference in image quality of T2*-weighted sequences obtained before and after contrast medium administration. No significant signal intensity differences of intracranial contrast enhancing masses were found (Group A P=0.9999; Group B P=0.9992). Susceptibility artifacts did not differ in appearance, and there was no effect on calculated signal intensity ratio (P=0.8142). Similarly, there was no effect of degree of enhancement or contrast heterogeneity on signal intensity ratio (P=0.4413). No correlation was found between signal intensity ratio and the time to acquisition (P=0.199). Administration of gadolinium-based MRI contrast agents does not adversely affect T2*-weighted imaging of the brain in dogs at 1.5T even in the presence of contrast enhancing lesions.

Signal compartments in ultra-high field multi-echo gradient echo MRI reflect underlying tissue microstructure in the brain

Gradient recalled echo magnetic resonance imaging (GRE-MRI) at ultra-high field holds great promise for new contrast mechanisms and delineation of putative tissue compartments that contribute to the multi-echo GRE-MRI signal may aid structural characterization. Several studies have adopted the three water-pool compartment model to study white matter brain regions, associating individual compartments with myelin, axonal and extracellular water. However, the number and identifiability of GRE-MRI signal compartments has not been fully explored. We undertook this task for human brain imaging data. Multiple echo time GRE-MRI data were acquired in five healthy participants, specific anatomical structures were segmented in each dataset (substantia nigra, caudate, insula, putamen, thalamus, fornix, internal capsule, corpus callosum and cerebrospinal fluid), and the signal fitted with models comprising one to six signal compartments using a complex-valued plane wave formulation. Information criteria and cluster analysis methods were used to ascertain the number of distinct compartments within the signal from each structure and to determine their respective frequency shifts. We identified five principal signal compartments with different relative contributions to each structure's signal. Voxel-based maps of the volume fraction of each of these compartments were generated and demonstrated spatial correlation with brain anatomy.

Utility of gradient recalled echo magnetic resonance imaging for the study of myelination in cuprizone mice treated with fingolimod.

The availability of high-field-strength magnetic resonance imaging (MRI) systems has brought about the development of techniques that aim to map myelination via the exploitation of various contrast mechanisms. Myelin mapping techniques have the potential to provide tools for the diagnosis and treatment of diseases, such as multiple sclerosis. In this study, we evaluated the sensitivity of T2 *, frequency shift and susceptibility measures to myelin levels in a cuprizone mouse model of demyelination. The model was supplemented with two different dosages of fingolimod, a drug known to positively affect demyelination. A decrease in grey-white matter contrast with the cuprizone diet was observed for T2 *, frequency shift and susceptibility measures, together with myelin basic protein antibody findings. These results indicate that T2 *, frequency shift and susceptibility measures have the potential to act as biomarkers for myelination. Susceptibility was found to be the most sensitive measure to changes in grey-white matter contrast. In addition, fingolimod treatment was found to reduce the level of demyelination, with a larger dosage exhibiting a greater reduction in demyelination for the in vivo MRI results. Overall, susceptibility mapping appears to be a more promising tool than T2 * or frequency shift mapping for the early diagnosis and treatment of diseases in which myelination is implicated.

Two-Dimensional Spoiled Gradient-Recalled Echo Magnetic Resonance Imaging of the Liver Using Respiratory Navigator-Gating Techniques.

We assessed the feasibility of T1-weighted 2-dimensional spoiled gradient-recalled (2D SPGR) acquisition in steady-state imaging of the liver with various respiratory navigator gating techniques. A total of 12 healthy volunteers underwent in-phase and out-of-phase 2D SPGR imaging of the liver during breath-holding and free-breathing. Four techniques for respiratory navigation, 2 conventional navigator techniques and 2 self-navigator techniques, were used for free-breathing imaging. Good navigator waveforms were obtained in conventional navigation, whereas fluctuations were evident in self navigation. All of the 4 navigator-based methods provided better images in terms of background signals and visual image quality compared with images obtained with no respiratory control. However, differences remained in comparison with breath-holding. Superiority of self-navigation to conventional navigation was not shown. Navigator-gating techniques improved 2D SPGR images of the liver acquired during free-breathing, suggesting feasibility and beneficial effects, although navigator-based images were still inferior to breath-hold images.

Sex-dependent effects of uric acid on cerebral microbleed: a cross-sectional study in the general population.

Elevated serum uric acid (UA) is known to be associated with stroke. However, there is little information on the association between serum UA levels and cerebral microbleed (CMB), a precursor of stroke. Therefore, we investigated the association between UA and CMB in a general population taking into consideration sex-related differences. The subjects in this cross-sectional study consisted of 2686 individuals of 40-79 years of age (1403 men and 1283 women) who underwent regular health screenings, including brain magnetic resonance imaging, at Seoul National University Hospital Health Promotion Center. Subjects were categorized into three groups according to tertiles of UA levels by sex. The presence and location of CMB were assessed by gradient-recalled echo magnetic resonance imaging. The prevalence of CMB was 3.8%. In multivariate logistic regression analysis by sex, the highest tertile of UA in male subjects was independently associated with the presence of CMB compared with the lowest tertile of UA (adjusted odds ratio, 2.46; P = 0.013). Meanwhile, the highest tertile of UA in female subjects was inversely associated with CMB compared with the lowest tertile of UA (adjusted odds ratio, 0.39; P = 0.040). High serum UA value was associated with higher prevalence of CMB in male, but lower prevalence of CMB in female subjects.

Revisiting Grade 3 Diffuse Axonal Injury: Not All Brainstem Microbleeds are Prognostically Equal.

Recovery of functional independence is possible in patients with brainstem traumatic axonal injury (TAI), also referred to as "grade 3 diffuse axonal injury," but acute prognostic biomarkers are lacking. We hypothesized that the extent of dorsal brainstem TAI measured by burden of traumatic microbleeds (TMBs) correlates with 1-year functional outcome more strongly than does ventral brainstem, corpus callosal, or global brain TMB burden. Further, we hypothesized that TMBs within brainstem nuclei of the ascending arousal network (AAN) correlate with 1-year outcome. Using a prospective outcome database of patients treated for moderate-to-severe traumatic brain injury at an inpatient rehabilitation hospital, we retrospectively identified 39 patients who underwent acute gradient-recalled echo (GRE) magnetic resonance imaging (MRI). TMBs were counted on the acute GRE scans globally and in the dorsal brainstem, ventral brainstem, and corpus callosum. TMBs were also mapped onto an atlas of AAN nuclei. The primary outcome was the disability rating scale (DRS) score at 1year post-injury. Associations between regional TMBs, AAN TMB volume, and 1-year DRS score were assessed by calculating Spearman rank correlation coefficients. Mean±SD number of TMBs was: dorsal brainstem=0.7±1.4, ventral brainstem=0.2±0.6, corpus callosum=1.8±2.8, and global=14.4±12.5. The mean±SD TMB volume within AAN nuclei was 6.1±18.7mm3. Increased dorsal brainstem TMBs and larger AAN TMB volume correlated with worse 1-year outcomes (R=0.37, p=0.02, and R=0.36, p=0.02, respectively). Global, callosal, and ventral brainstem TMBs did not correlate with outcomes. These findings suggest that dorsal brainstem TAI, especially involving AAN nuclei, may have greater prognostic utility than the total number of lesions in the brain or brainstem.

MR elastography: high rate of technical success in pediatric and young adult patients.

Magnetic resonance (MR) elastography allows the noninvasive assessment of liver stiffness, which is a surrogate for fibrosis. The purpose of this study was to describe our experience using liver MR elastography in a large pediatric population with attention to the frequency and causes of exam failure. Imaging records were searched for patients ≤18years of age who underwent 2-D gradient recalled echo (GRE) MR elastography of the liver between September 2011 and August 2015 on one of two 1.5-T MRI platforms. Imaging reports and clinical records were reviewed for failed MR elastography acquisitions, factor(s) resulting in failure and whether a subsequent successful examination had been performed. Four hundred sixty-eight MR elastography examinations were performed in 372 patients between 1.5months and 18years of age during the study period. Ninety-six percent (450/468) of the examinations were successful. There was no significant difference in mean age (12.6±3.6 vs. 11.2±4.1years, P=0.12) or body mass index (BMI) (28.2±12.4 vs. 29.5±10kg/m2, P=0.6) between patients with and without successful examinations. MR elastography failures were due to poor paddle positioning resulting in inadequate generation of hepatic shear waves (n=5), iron overload (n=4), patient inability to tolerate MRI (n=3), patient breathing/motion (n=3), artifact from implanted hardware (n=1) and technical malfunction (n=2). Seven of nine (78%) repeat examinations were successful (78%). Hepatic 2-D GRE MR elastography at 1.5T is technically robust in children. Exam failure is infrequent and largely reflects patient specific factors, some of which can be mitigated with careful technique.

Spin-echo Echo-planar Imaging MR Elastography versus Gradient-echo MR Elastography for Assessment of Liver Stiffness in Children and Young Adults Suspected of Having Liver Disease.

Purpose To compare two-dimensional (2D) gradient-recalled echo (GRE) and 2D spin-echo (SE) echo-planar imaging (EPI) magnetic resonance (MR) elastography for measurement of hepatic stiffness in pediatric and young adult patients suspected of having liver disease. Materials and Methods In this institutional review board-approved, HIPAA-compliant study, 58 patients underwent both 2D GRE and 2D SE-EPI MR elastography at 1.5 T during separate breath holds. Liver stiffness (mean of means; in kilopascals) was measured by five blinded reviewers. Pooled mean liver stiffness and region-of-interest (ROI) size were compared by using paired t tests. Intraclass correlation coefficients (ICCs) were used to assess agreement between techniques. Respiratory motion artifacts were compared across sequences by using the Fisher exact test. Results Mean patient age was 14.7 years ± 5.2 (standard deviation; age range, 0.7-20.5 years), and 55.2% (32 of 58) of patients were male. Mean liver stiffness was 2.92 kPa ± 1.29 measured at GRE MR elastography and 2.76 kPa ± 1.39 at SE-EPI MR elastography (n = 290; P = .15). Mean ROI sizes were 8495 mm2 ± 4482 for 2D GRE MR elastography and 15 176 mm2 ± 7609 for 2D SE-EPI MR elastography (n = 290; P < .001). Agreement was excellent for measured stiffness between five reviewers for both 2D GRE (ICC, 0.97; 95% confidence interval: 0.95, 0.98) and 2D SE-EPI (ICC, 0.98; 95% confidence interval: 0.96, 0.99). Mean ICC (n = 5) for agreement between 2D GRE and 2D SE-EPI MR elastography was 0.93 (range, 0.91-0.95). Moderate or severe breathing artifacts were observed on 27.5% (16 of 58) of 2D GRE images versus 0% 2D SE-EPI images (P < .001). Conclusion There is excellent agreement on measured hepatic stiffness between 2D GRE and 2D SE-EPI MR elastography across multiple reviewers. SE-EPI MR elastography allowed for stiffness measurement across larger areas of the liver and can be performed in a single breath hold. © RSNA, 2016.

Editorial: A New Spin on Magnetic Resonance Elastography.

The development of hepatic fibrosis is the hallmark of liver disease progression. Identifying fibrosis across the spectrum, from early stages to cirrhosis has become a major unmet need. Newer imaging techniques that measure liver elastography (stiffness) as a surrogate of fibrosis seem to outperform serum tests. The current study compares two-dimensional (2D) gradient-recalled echo magnetic resonance elastography (MRE) to three-dimensional (3D) spin-echo echo-planar imaging MRE. 3D-SE-EPI MRE was able to image more liver volume in less time with fewer technical failures. The current study demonstrates that 3D-SE-EPI MRE appears marginally superior to 2D-GRE and may evolve into the new gold standard.

Effect and Safety of Rosuvastatin in Acute Ischemic Stroke.

Background and PurposeThe benefit of statins in acute stroke remains uncertain. Statins may prevent stroke recurrence during the acute stage of stroke via pleiotropic effects. However, statins may increase the risk of intracerebral hemorrhage. We investigated the effect and safety of rosuvastatin in acute stroke patients.MethodsThis randomized, double-blind, multi-center trial compared rosuvastatin 20 mg and placebo in statin-naïve stroke patients who underwent diffusion-weighted imaging (DWI) within 48 hours after symptom onset. The primary outcome was occurrence of new ischemic lesions on DWI at 5 or 14 days.ResultsThis trial was stopped early after randomization of 316 patients due to slow enrollment. Among 289 patients with at least one follow-up imaging, the frequency of new ischemic lesions on DWI was not different between groups (rosuvastatin: 27/137, 19.7% vs. placebo: 36/152, 23.6%) (relative risk 0.83, 95% confidence interval 0.53–1.30). Infarct volume growth at 5 days (log-transformed volume change, rosuvastatin: 0.2±1.0 mm3 vs. placebo: 0.3±1.3 mm3; P=0.784) was not different, either. However, hemorrhagic infarction or parenchymal/subarachnoid hemorrhage on gradient-recalled echo magnetic resonance imaging occurred less frequently in the rosuvastatin group (6/137, 4.4%) than the placebo group (22/152, 14.5%, P=0.007). Among 314 patients with at least one dose of study medication, progression or clinical recurrence of stroke tended to occur less frequently in the rosuvastatin group (1/155, 0.6% vs. 7/159, 4.4%, P=0.067). Adverse events did not differ between groups.ConclusionsThe efficacy of rosuvastatin in reducing recurrence in acute stroke was inconclusive. However, statin use was safe and reduced hemorrhagic transformation.

Postoperative lumbar epidural abscess: conventional and advanced magnetic resonance imaging findings

A 54-year-old female patient was admitted to our departmentwithnumbnessinbothlowerextremitiesduringthepast 2 weeks. She had a history of discectomy surgery. Spinal magneticresonance(MR)imagingwasperformed.Magnetic resonance imaging revealed an extradural mass. The lesion was iso-hyperintense on T2-weighted images comparing muscle intensity (Fig. 1, Left and Right). Abscess or hematoma was considered for different diagnosis of mass. Gradient-recalled echo, diffusion- and contrast-enhanced MR imaging were performed. The mass was hyperintense on hemo sequence (Fig. 2). Thus, hematoma was excluded. On the diffusion-weighted imaging, the lesion was homogeneousincreasedsignalintensity.Theapparentdiffusioncoefficient map showed significant diffusion restriction (Fig. 3, Left and Right). The mass was also peripherally contrast enhanced (Fig. 4, Top, Bottom, and Right). With the MR imaging findings, the lesion was considered as an epidural abscess. Drainage treatment for abscess was planned. An urgent reoperation was performed. There was yellowish liquid pus in the extradural area. She was treated with evacuation of the epidural abscess. No additional pathologic findings were observed in the extradural area. Culture showed methicillin-susceptible Staphylococcus aureus. Appropriate antibiotics were administered. With an intensive treatment, the patient showed good neurologic improvement and was discharged after 8 weeks of IV antibiotic therapy.