T1-weighted Gradient-recalled Echo Research Articles

Absence of the Susceptibility Vessel Sign with Cancer-Associated Hypercoagulability-Related Stroke.

The susceptibility vessel sign, a hypointense signal on MR T2-weighted gradient-recalled echo images, is associated with erythrocyte-predominant thrombi, which are often present in cardioembolism. In contrast, cancer-associated hypercoagulability (CAH)-related stroke, which is presumably caused by fibrin-predominant thrombi, is associated with the absence of the susceptibility vessel sign. We hypothesized that the prevalence of the susceptibility vessel sign may be helpful in distinguishing CAH-related stroke from cardioembolism. This study attempted to validate this hypothesis and investigated the usefulness of the susceptibility vessel sign in differentiating CAH-related stroke from cardioembolism. We retrospectively studied patients with both CAH-related stroke (CAH group) and cardioembolism (cardioembolism group) who had major cerebral artery occlusion on MRA that was performed within 6 hours of stroke onset. All patients visited our department from 2015 to 2021. CAH-related stroke was defined as the following: 1) complication of active cancer, 2) pretreatment D-dimer value of >3 μg/mL, 3) multiple vascular territory infarctions, and 4) lack of any other specifically identified causes of stroke. We compared susceptibility vessel sign positivity rates within each group. Multivariable logistic regression analysis was used to assess the association between the absence of the susceptibility vessel sign and CAH-related stroke. Of 691 patients with CAH-related stroke or cardioembolism, major cerebral artery occlusion was observed in 10 patients in the CAH group and 198 patients in the cardioembolism group. The absence of the susceptibility vessel sign was identified in 55 of 208 patients and was significantly more frequent in the CAH group versus the cardioembolism group (90% versus 24%, P < .05). For predicting CAH-related stroke, the absence of the susceptibility vessel sign demonstrated a sensitivity of 90% (95% CI, 59%-99%), specificity of 78% (95% CI, 71%-83%), a positive predictive value of 18% (95% CI, 10-31), a negative predictive value of 99% (95% CI, 96%-99%), and a likelihood ratio of 4.06. Multivariable logistic regression analysis revealed that the absence of the susceptibility vessel sign was independently associated with CAH-related stroke (OR, 43; 95% CI, 6.8-863; P < .01). The absence of the susceptibility vessel sign was more frequent in CAH-related stroke than in cardioembolism. These findings could potentially be helpful for clinical management and differentiating cardioembolism and CAH-related stroke.

Free-Breathing High-Resolution, Swap-Free, and Motion-Corrected Water/Fat Separation in Pediatric Abdominal MRI.

The T1-weighted GRE (gradient recalled echo) sequence with the Dixon technique for water/fat separation is an essential component of abdominal MRI (magnetic resonance imaging), useful in detecting tumors and characterizing hemorrhage/fat content. Unfortunately, the current implementation of this sequence suffers from several problems: (1) low resolution to maintain high pixel bandwidth and minimize chemical shift; (2) image blurring due to respiratory motion; (3) water/fat swapping due to the natural ambiguity between fat and water peaks; and (4) off-resonance fat blurring due to the multipeak nature of the fat spectrum. The goal of this study was to evaluate the image quality of water/fat separation using a high-resolution 3-point Dixon golden angle radial acquisition with retrospective motion compensation and multipeak fat modeling in children undergoing abdominal MRI. Twenty-two pediatric patients (4.2 ± 2.3 years) underwent abdominal MRI on a 3 T scanner with routine abdominal protocol and with a 3-point Dixon radial-VIBE (volumetric interpolated breath-hold examination) sequence. Field maps were calculated using 3D graph-cut optimization followed by fat and water calculation from k-space data by iteratively solving an optimization problem. A 6-peak fat model was used to model chemical shifts in k-space. Residual respiratory motion was corrected through soft-gating by weighting each projection based on the estimated respiratory motion from the center of the k-space. Reconstructed images were reviewed by 3 pediatric radiologists on a PACS (picture archiving and communication systems) workstation. Subjective image quality and water/fat swapping artifact were scored by each pediatric radiologist using a 5-point Likert scale. The VoL (variance of Laplacian) of the reconstructed images was used to objectively quantify image sharpness. Based on the overall Likert scores, the images generated using the described method were significantly superior to those reconstructed by the conventional 2-point Dixon technique ( P < 0.05). Water/fat swapping artifact was observed in 14 of 22 patients using 2-point Dixon, and this artifact was not present when using the proposed method. Image sharpness was significantly improved using the proposed framework. In smaller patients, a high-quality water/fat separation with sharp visualization of fine details is critical for diagnostic accuracy. High-resolution golden angle radial-VIBE 3-point Dixon acquisition with 6-peak fat model and soft-gated motion correction offers improved image quality at the expense of an additional ~1-minute acquisition time. Thus, this technique offers the potential to replace the conventional 2-point Dixon technique.

Functional and Morphological Brain Alterations in Dysthyroid Optic Neuropathy: A Combined Resting-State fMRI and Voxel-Based Morphometry Study.

Increasing evidence has indicated that the entire visual pathway from retina to visual cortex may be involved in dysthyroid optic neuropathy (DON) pathological mechanisms. To explore the functional and morphological brain characteristics in DON and their relationship with ophthalmologic performance. Retrospective. A total of 30 DON patients, 40 thyroid-associated ophthalmopathy (TAO) without DON patients and 21 healthy-controls (HCs). A 3.0 T, 3D T1-weighted spoiled gradient-recalled echo and gradient-recalled echo-planar imaging. Functional and structural alterations in brain regions were evaluated with fractional amplitude of low-frequency fluctuations, degree centrality (DC), and gray matter volume (GMV). Clinical activity score (CAS) is assessed across patients. One-way analysis of variance with post hoc two sample t-tests (GRF-corrected, voxel level: P< 0.005, cluster level: P< 0.05) and correlation analysis (significance level: P< 0.05). Compared to HCs, DON patients had significantly decreased DC values in the bilateral BA17 and BA18 regions. Compared to the TAO group, DON patients had decreased GMV in the left anterior cingulate cortex, left middle frontal gyrus, left lingual gyrus, left parietal gyrus, right Rolandic operculum, left supplementary motor area, and right middle temporal gyrus. In addition, GMV in the right Rolandic operculum was significantly positively correlated with CAS (correlation coefficient: r= 0.448). This study showed significant morphological and functional alterations in visual cortex and morphological alterations in partial default mode network regions of DON patients, which may provide insights into the mechanism of vision loss and may facilitate the diagnosis and treatment of DON. 3. Stage 3.

Tissue Probability Based Registration of Diffusion-Weighted Magnetic Resonance Imaging.

Current registration methods for diffusion-MRI (dMRI) data mostly focus on white matter (WM) areas. Recently, dMRI has been employed for the characterization of gray matter (GM) microstructure, emphasizing the need for registration methods that consider all tissue types. To develop a dMRI registration method based on GM, WM, and cerebrospinal fluid (CSF) tissue probability maps (TPMs). Retrospective longitudinal study. Thirty-two healthy participants were scanned twice (legacy data), divided into a training-set (n=16) and a test-set (n=16), and 35 randomly-selected participants from the Human Connectome Project. 3.0T, diffusion-weighted spin-echo echo-planar sequence; T1-weighted spoiled gradient-recalled echo (SPGR) sequence. A joint segmentation-registration approach was implemented: Diffusion tensor imaging (DTI) maps were classified into TPMs using machine-learning approaches. The resulting GM, WM, and CSF probability maps were employed as features for image alignment. Validation was performed on the test dataset and the HCP dataset. Registration performance was compared with current mainstream registration tools. Classifiers used for segmentation were evaluated using leave-one-out cross-validation and scored using Dice-index. Registration success was evaluated by voxel-wise variance, normalized cross-correlation of registered DTI maps, intra- and inter-subject similarity of the registered TPMs, and region-based intra-subject similarity using an anatomical atlas. One-way ANOVAs were performed to compare between our method and other registration tools. The proposed method outperformed mainstream registration tools as indicated by lower voxel-wise variance of registered DTI maps (SD decrease of 10%) and higher similarity between registered TPMs within and across participants, for all tissue types (Dice increase of 0.1-0.2; P < 0.05). A joint segmentation-registration approach based on diffusion-driven TPMs provides a more accurate registration of dMRI data, outperforming other registration tools. Our method offers a "translation" of diffusion data into structural information in the form of TPMs, allowing to directly align diffusion and structural images. 1 Technical Efficacy Stage: 1.

Clinical implementation of MRI-based organs-at-risk auto-segmentation with convolutional networks for prostate radiotherapy

BackgroundStructure delineation is a necessary, yet time-consuming manual procedure in radiotherapy. Recently, convolutional neural networks have been proposed to speed-up and automatise this procedure, obtaining promising results. With the advent of magnetic resonance imaging (MRI)-guided radiotherapy, MR-based segmentation is becoming increasingly relevant. However, the majority of the studies investigated automatic contouring based on computed tomography (CT).PurposeIn this study, we investigate the feasibility of clinical use of deep learning-based automatic OARs delineation on MRI.Materials and methodsWe included 150 patients diagnosed with prostate cancer who underwent MR-only radiotherapy. A three-dimensional (3D) T1-weighted dual spoiled gradient-recalled echo sequence was acquired with 3T MRI for the generation of the synthetic-CT. The first 48 patients were included in a feasibility study training two 3D convolutional networks called DeepMedic and dense V-net (dV-net) to segment bladder, rectum and femurs. A research version of an atlas-based software was considered for comparison. Dice similarity coefficient, 95% Hausdorff distances (HD95), and mean distances were calculated against clinical delineations. For eight patients, an expert RTT scored the quality of the contouring for all the three methods. A choice among the three approaches was made, and the chosen approach was retrained on 97 patients and implemented for automatic use in the clinical workflow. For the successive 53 patients, Dice, HD95 and mean distances were calculated against the clinically used delineations.ResultsDeepMedic, dV-net and the atlas-based software generated contours in 60 s, 4 s and 10-15 min, respectively. Performances were higher for both the networks compared to the atlas-based software. The qualitative analysis demonstrated that delineation from DeepMedic required fewer adaptations, followed by dV-net and the atlas-based software. DeepMedic was clinically implemented. After retraining DeepMedic and testing on the successive patients, the performances slightly improved.ConclusionHigh conformality for OARs delineation was achieved with two in-house trained networks, obtaining a significant speed-up of the delineation procedure. Comparison of different approaches has been performed leading to the succesful adoption of one of the neural networks, DeepMedic, in the clinical workflow. DeepMedic maintained in a clinical setting the accuracy obtained in the feasibility study.

Migraine or idiopathic intracranial hypertension: Magnetic resonance venography and magnetic resonance imaging findings.

Idiopathic intracranial hypertension (IIH) is a disease characterised by increased cerebral pressure without a mass or hydrocephalus. We aimed to differentiate migraine and IIH patients based on imaging findings. Patients with IIH (n = 32), migraine patients (n = 34) and control subjects (n = 33) were evaluated. Routine magnetic resonance imaging, contrast-enhanced 3D magnetic resonance venography and/or T1-weighted 3D gradient-recalled echo were taken with a 1.5 T magnetic resonance scanner. Optic-nerve sheath distention, flattened posterior globe and the height of the pituitary gland were evaluated in the three groups. Transverse sinuses (TS) were evaluated with respect to score of attenuation/stenosis and distribution. Pearson chi-square, Fisher's exact test and chi-square trend statistical analyses were used for comparisons between the groups. A p-value of <0.05 was considered statistically significant. Decreased pituitary gland height, optic-nerve sheath distention and flattened posterior globe were found to be statistically significant (p < 0.001) in IIH patients. Bilateral TS stenosis was also more common in IIH patients than in the control group and migraine group (p = 0.02). Decreased pituitary gland height, optic-nerve sheath distention, flattened posterior globe, bilateral stenosis and discontinuity in TS are significant findings in differentiating IIH cases from healthy individuals and migraine patients. Bilateral TS stenosis may be the cause rather than the result of increased intracranial pressure. The increase in intracranial pressure, which is considered to be responsible for the pathophysiology of IIH, is not involved in the pathophysiology of migraine.

Functional MRI Safety and Artifacts during Deep Brain Stimulation: Experience in 102 Patients.

BackgroundWith growing numbers of patients receiving deep brain stimulation (DBS), radiologists are encountering these neuromodulation devices at an increasing rate. Current MRI safety guidelines, however, limit MRI access in these patients.PurposeTo describe an MRI (1.5 T and 3 T) experience and safety profile in a large cohort of participants with active DBS systems and characterize the hardware-related artifacts on images from functional MRI.Materials and MethodsIn this prospective study, study participants receiving active DBS underwent 1.5- or 3-T MRI (T1-weighted imaging and gradient-recalled echo [GRE]-echo-planar imaging [EPI]) between June 2017 and October 2018. Short- and long-term adverse events were tracked. The authors quantified DBS hardware-related artifacts on images from GRE-EPI (functional MRI) at the cranial coil wire and electrode contacts. Segmented artifacts were then transformed into standard space to define the brain areas affected by signal loss. Two-sample t tests were used to assess the difference in artifact size between 1.5- and 3-T MRI.ResultsA total of 102 participants (mean age ± standard deviation, 60 years ± 11; 65 men) were evaluated. No MRI-related short- and long-term adverse events or acute changes were observed. DBS artifacts were most prominent near the electrode contacts and over the frontoparietal cortical area where the redundancy of the extension wire is placed subcutaneously. The mean electrode contact artifact diameter was 9.3 mm ± 1.6, and 1.9% ± 0.8 of the brain was obscured by the coil artifact. The coil artifacts were larger at 3 T than at 1.5 T, obscuring 2.1% ± 0.7 and 1.4% ± 0.7 of intracranial volume, respectively (P < .001). The superficial frontoparietal cortex and deep structures neighboring the electrode contacts were most commonly obscured.ConclusionWith a priori local safety testing, patients receiving deep brain stimulation may safely undergo 1.5- and 3-T MRI. Deep brain stimulation hardware-related artifacts only affect a small proportion of the brain.© RSNA, 2019Online supplemental material is available for this article.See also the editorial by Martin in this issue.

Natural embryonic death in the plain viscacha Lagostomus maximus: are there previous anatomo-histological variations that would intervene in the differential survival of the implantations?

Visualization of the retroplacental clear space (RPCS) may provide critical insight into the development of abnormally invasive placenta (AIP). In this pre-clinical study, we characterized the appearance of the RPCS on magnetic resonance imaging (MRI) during the second half of gestation using a liposomal gadolinium contrast agent (liposomal-Gd).Studies were performed in fifteen pregnant C57BL/6 mice at 10, 12, 14, 16, and 18 days of gestation. MRI was performed on a 1T permanent magnet scanner. Pre-contrast and post-contrast images were acquired using T1-weighted gradient-recalled echo (T1w-GRE) and T2-weighted fast spin echo (T2w-FSE) sequences. Animals were euthanized after imaging and feto-placental units harvested for histological examination. Visualization of the RPCS was scored by a maternal-fetal radiologist and quantified by measuring the contrast-to-noise ratio (CNR) on T1w images. Feto-placental features were segmented for analysis of volumetric changes during gestation.Contrast-enhanced T1w images enabled the visualization of structural changes in placental development between days 10–18 of gestation. Although the placental margin on the fetal side was clearly visible at all time points, the RPCS was partially visible at day 10 of gestation, and clearly visible by day 12. Hematoxylin and eosin (H&E) staining of the placental tissue corroborated MRI findings of structural and morphological changes in the placenta.Contrast-enhanced MR imaging using liposomal-Gd enabled adequate visualization of the retroplacental clear space starting at day 12 of gestation. The agent also enabled characterization of placental structure and morphological changes through gestation.

Pre-clinical magnetic resonance imaging of retroplacental clear space throughout gestation

IntroductionVisualization of the retroplacental clear space (RPCS) may provide critical insight into the development of abnormally invasive placenta (AIP). In this pre-clinical study, we characterized the appearance of the RPCS on magnetic resonance imaging (MRI) during the second half of gestation using a liposomal gadolinium contrast agent (liposomal-Gd). Materials and methodsStudies were performed in fifteen pregnant C57BL/6 mice at 10, 12, 14, 16, and 18 days of gestation. MRI was performed on a 1T permanent magnet scanner. Pre-contrast and post-contrast images were acquired using T1-weighted gradient-recalled echo (T1w-GRE) and T2-weighted fast spin echo (T2w-FSE) sequences. Animals were euthanized after imaging and feto-placental units harvested for histological examination. Visualization of the RPCS was scored by a maternal-fetal radiologist and quantified by measuring the contrast-to-noise ratio (CNR) on T1w images. Feto-placental features were segmented for analysis of volumetric changes during gestation. ResultsContrast-enhanced T1w images enabled the visualization of structural changes in placental development between days 10–18 of gestation. Although the placental margin on the fetal side was clearly visible at all time points, the RPCS was partially visible at day 10 of gestation, and clearly visible by day 12. Hematoxylin and eosin (H&E) staining of the placental tissue corroborated MRI findings of structural and morphological changes in the placenta. ConclusionsContrast-enhanced MR imaging using liposomal-Gd enabled adequate visualization of the retroplacental clear space starting at day 12 of gestation. The agent also enabled characterization of placental structure and morphological changes through gestation.

Correlations of MRI manifestations with survivin gene expression in primary hepatic carcinoma.

To investigate the correlations of magnetic resonance imaging (MRI) manifestations with survivin gene expression in primary hepatocellular carcinoma (HCC). A total of 84HCC patients receiving partial hepatectomy in the Surgery Department and Oncology Department in our hospital from April 2011 to May 2014 were recruited. At 1week before operation, MRI was used to examine the imaging features of liver, a certain size of area was defined and the signal value of each sequence was recorded. HCC and para-carcinoma tissues were collected after operation, and the expression levels of survivin were detected via immunohistochemistry (IHC). All patients were followed up for 30months after operation, and the Kaplan-Meier survival curve was drawn. The correlations of survivin expression with MRI features and signal parameters of each sequence were analyzed. There was no expression of survivin in normal liver tissues. In HCC and para-carcinoma tissues, the nuclei of positive cells showed brown yellow. The positive expression rate of survivin in HCC tissues was 76.19% (64/84), which was significantly higher than that in para-carcinoma tissues (20.81%, 20/84) (p< 0.05). The overall survival (OS) of patients with high expression of survivin was 12.5months, which was significantly shorter than that of patients with low expression of survivin (17.6months) (p< 0.05). Results of chi-square test showed that the survivin level had no correlations with the MRI scan shape and edge in the tumor area (p> 0.05), but it was significantly correlated with tumor diameter, MRI enhancement features and lymphatic metastasis (p< 0.05). Pearson correlation analyses revealed that the survivin IHC score was not correlated with in-phase T1-weighted gradient-recalled echo (GRE), hepatic arterial-phase T1-weighted GRE, portal venous-phase T1-weighted GRE and equilibrium-phase T1-weighted GRE signals (p> 0.05). Besides, the survivin IHC score was negatively correlated with opposed-phase T1-weighted GRE (r=-0.46, p= 0.038), but positively correlated with T2-weighted fast spin echo signal (r=-0.49, p= 0.025). Survivin is significantly up-regulated in HCC tissues and associated with tumor growth and lymph node metastasis. Clinical detection of survivin level combined with MRI examination might be beneficial for clinical diagnosis and treatment of HCC.

Cerebral Microbleeds Could Be Independently Associated with Intracranial Aneurysm Rupture: A Cross-Sectional Population-Based Study

To determine whether the presence of cerebral microbleeds (CMBs) is independently associated with intracranial aneurysm rupture and to identify the time interval of CMB-related intracranial aneurysm rupture. This cross-sectional study included 1847 patients with unruptured and ruptured intracranial aneurysms from January 2010 to November 2017. Clinical records and imaging, including T2-weighted gradient-recalled echo sequence magnetic resonance imaging that identified the presence of CMBs preoperatively, were evaluated. Univariate analysis and multivariate logistic regression were done to determine which parameters were independent factors for aneurysm rupture. The time interval of CMB-related intracranial aneurysm rupture was also evaluated. CMBs confirmed by magnetic resonance imaging were present in 142 patients (142/1847; 7.7%). Of 142 patients with CMBs, 56 patients (including 17 ruptured aneurysms) who received endovascular treatment and another 86 consecutive patients who did not receive embolization or surgery for various reasons were followed for 3-49 months. The incidence of CMB-related intracranial aneurysm rupture was 27.9% (24/86) during the follow-up period. The time interval of CMB-related intracranial aneurysm rupture was 3-27 months (median 9.5 months). Multivariate analyses showed CMBs were significantly correlated with intracranial aneurysm rupture (odds ratio= 1.6; 95% confidence interval, 1.1-2.4; P= 0.010). CMBs were independently associated with intracranial aneurysm rupture. Patients with CMBs have a 60% increased risk of aneurysm rupture compared with patients without CMBs.

JOURNAL CLUB: Four-Dimensional Flow MRI-Based Splenic Flow Index for Predicting Cirrhosis-Associated Hypersplenism.

The objective of this study is to evaluate the ability of spleen volume, blood flow, and an index incorporating multiple measures to predict cirrhosis-associated hypersplenism. A total of 39 patients (14 women and 25 men; mean [± SD] age, 52 ± 10 years) with cirrhosis and sequelae of portal hypertension underwent 4D flow MRI and anatomic 3-T MRI performed before and after contrast administration. Unenhanced 4D flow MRI was used to assess abdominal hemodynamics, and splenic volumes were measured on T1-weighted gradient-recalled echo MRI. Relationships among demographic characteristics, blood component counts, splenic volume, arterial flow, venous flow, and the percentage of shunted portal flow were assessed in 29 consecutive patients (i.e., the derivation group), to develop a splenic flow index. This index was assessed along with splenic volume and blood flow alone in 10 additional consecutive patients (i.e., the validation group) via ROC curve analysis, to identify platelet counts of less than 50 × 103 cells/μL, leukocyte counts of less than 3.0 × 103 cells/μL, or both. In the derivation cohort (platelet count, 129 ± 76 × 103 cells/μL), splenic volume, arterial flow, venous flow, and the percentage of shunted portal flow were inversely correlated with platelet counts (ρ = -0.68, -0.68, -0.56, and -0.36, respectively; p < 0.05). Adding splenic volume to arterial flow and the product of venous flow and the percentage of shunted portal flow indexed to the body surface area yielded superior correlations with platelet counts, leukocyte counts, and the degree of severity of hypersplenism (ρ = -0.75, -0.48, and -0.75, respectively; p ≤ 0.001) and predicted severe hypersplenism (sensitivity, 100%; specificity, 100%) in the validation cohort (platelet count, 93 ± 71 × 103 cells/μL). A splenic flow index that incorporates both splenic volume and blood flow is a better indicator of hypersplenism than is splenic volume alone.

Abstract TP172: Pulmonary Function and White Matter Hyperintensity in Neurologically Healthy Adults

Introduction: Cerebral small vessel disease (SVD) is considered as precursor lesion of many clinical outcomes including stroke and dementia. It is well established that obstructive sleep apnea or chronic obstructive pulmonary disease is an independent risk factor of stroke. However, there are few studies about the association between pulmonary function and the presence of cerebral small vessel disease. Purpose: This study aims to investigate the association between pulmonary function and cerebral SVD in healthy adults. Methods: We conducted a cross-sectional study of 1,528 neurologically healthy people (mean age 56.0±9.0; 847 men), who underwent brain MRI and pulmonary function tests (forced vital capacity (FVC), forced expiratory volume in the first second (FEV 1 )). Risk factors, anthropometric parameters and clinical information were obtained. For evaluating cerebral SVD, the presence of small silent infarction (SSI) and the volume of white matter hyperintensity (WMH) were assessed through axial T2 fluid-attenuated inversion recovery (FLAIR) sequences MRI. Cerebral microbleeds (CMBs) were evaluated through T2-weighted gradient-recalled echo MRI. Results: The prevalence of SSI and CMBs were 9.6% (147 subjects) and 4.1% (63 subjects), respectively. The mean volume of WMH was 2.8±6.2mm 3 . In multiple regression analysis that controlled for age, sex, and smoking status, FVC had a significant negative correlation with WMH volume (R 2 =0.005, β=-0.109, p=0.002), and FEV 1 /FVC ratio had a significant correlation with WMH volume (R 2 =0.006, β=0.083, p=&lt;0.001). In multivariable logistic analysis, after adjusting age, gender, hypertension, and glucose, FVC was negatively associated with the presence of SSI (adjusted OR 0.63, 95% CI 0.44-0.91), and FEV 1 /FVC ratio was positively associated with the presence of SSI (adjusted OR 1.05, 95% CI 1.02-1.08). The presence of CMBs was not associated with any factor of pulmonary function tests. Conclusions: The results from our study suggest that lower pulmonary function, especially FVC, was found to be an independent risk factor of cerebral SVD in neurologically healthy adults.

Diagnostic Performance of MRI Sequences for Evaluation of Dural Venous Sinus Thrombosis.

The purpose of this study is to assess the performance of routinely used MRI sequences with and without contrast enhancement in the diagnostic evaluation of dural venous sinus thrombosis (DVST). We identified consecutive patients older than 18 years who underwent concurrent standardized brain MRI and contrast-enhanced (CE) MR venography (MRV) examinations for suspected DVST. The seven MRI sequences that were used (axial unenhanced T1-weighted, T1-weighted CE, T2-weighted, DWI, T2-weighted FLAIR, T2-weighted gradient-recalled echo [GRE], and sagittal 3D T1-weighted GRE CE sequences) were randomized, anonymized, and reviewed independently by two neuroradiologists who were blinded to the final diagnosis. Ten separate venous sinus segments were evaluated. CE MRV was the reference standard for determining the presence or absence of DVST, and it was performed using the following imaging parameters: TR/TE, 4.1-77/1.4-9.5; flip angle, 12-35°; and slice thickness, 0.8-1.4 mm. The diagnostic performance of and interobserver variability for each sequence was assessed per patient and per segment. Thirty-six patients with DVST (72% of whom had acute thrombosis and 28% of whom had chronic thrombosis) and 29 patients without DVST were included in the study. For each sequence, the AUC values for the detection of DVST per patient, as determined by reviewer 1 and reviewer 2, respectively, were as follows: for T1-weighted unenhanced sequences, 55% and 61%; for T1-weighted CE sequences, 79% and 80%; for T2-weighted sequences, 77% and 76%; for DWI sequences, 59% and 64%; for T2-weighted FLAIR sequences, 70% and 72%; for T2-weighted GRE sequences, 64% and 66%; and for the 3D T1-weighted GRE CE sequence, 77% and 81%. The diagnostic performance of the 3D T1-weighted GRE CE sequences was statistically significantly greater than that of the other sequences. Interobserver variability ranged from 0.26 (for T1-weighted unenhanced sequences) to 0.73 (for the DWI sequence). Overall, for each reviewer and with the use of all evaluated sequences, MRI had a high sensitivity (> 99% for both reviewers) but low specificity (14% for reviewer 1 and 48% for reviewer 2) for the detection of DVST. Sequences used in routine brain MRI performed with and without contrast enhancement have varying strengths that are important to recognize when the likelihood of DVST is assessed, but they do not replace the utility of dedicated CE MRV.

High-resolution T1-weighted gradient echo imaging for liver MRI using parallel imaging at high-acceleration factors

To determine whether application of a high-acceleration parallel acquisition can provide three-dimensional (3D)-fat-suppressed T1-weighted gradient-recalled-echo (T1W-GRE) imaging at 3T for liver MR imaging. This retrospective study was approved by our institutional review board. Seventy patients underwent liver MRI at a 3T scanner. After administration of a standard dose of Gadoxetic acid for 20 min, 3D-T1W-GRE images were obtained twice using sensitivity encoding with acceleration factors (AFs) 2.6 [332 × 298 matrix, 3-mm slice thickness (ST)] and 4 (380 × 320 matrix, 1.5-mm ST). The image qualities of the two image sets were graded using a five-point scale. The high-resolution (HR) 3D-T1W-GRE image sets were obtained with an AF 4 within a single breath-hold (18.5 s). It showed a better anatomic depiction than conventional 3D-T1W-GRE image sets with an AF 2.6 (p < 0.05). Although the image noise was higher on the HR image sets (p < 0.05), the HR image sets showed better lesion conspicuity and overall image quality than the conventional image sets (p < 0.05). With the use of high AFs, HR 3D-T1W-GRE imaging was demonstrated to be clinically more feasible and advantageous than the conventional 3D-T1W-GRE.

Three-dimensional humeral morphologic alterations and atrophy associated with obstetrical brachial plexus palsy

Obstetrical brachial plexus palsy (OBPP) is a common birth injury, resulting in severe functional losses. Yet, little is known about how OBPP affects the 3-dimensional (3D) humeral morphology. Thus, the purpose of this study was to measure the 3D humeral architecture in children with unilateral OBPP. Thirteen individuals (4 female and 9 male patients; mean age, 11.8 ± 3.3 years; mean Mallet score, 15.1 ± 3.0) participated in this institutional review board approved study. A 3D T1-weighted gradient-recalled echo magnetic resonance image set was acquired for both upper limbs (involved and noninvolved). Humeral size, version, and inclination were quantified from 3D humeral models derived from these images. The involved humeral head was significantly less retroverted and in declination (medial humeral head pointed anteriorly and inferiorly) relative to the noninvolved side. Osseous atrophy was present in all 3 dimensions and affected the entire humerus. The inter-rater reliability was excellent (intraclass correlation coefficient, 0.96-1.00). This study showed that both humeral atrophy and bone shape deformities associated with OBPP are not limited to the axial plane but are 3D phenomena. Incorporating information related to these multi-planar, 3D humeral deformities into surgical planning could potentially improve functional outcomes after surgery. The documented reduction in retroversion is an osseous adaptation, which may help maintain glenohumeral congruency by partially compensating for the internal rotation of the arm. The humeral head declination is a novel finding and may be an important factor to consider when one is developing OBPP management strategies because it has been shown to lead to significant supraspinatus inefficiencies and increased required elevation forces.

Precise size evaluation of extraocular muscles using fat-suppressed fast T1-weighted gradient-recalled echo imaging and multiple gaze fixation targets

We studied the feasibility of the precise size measurement of extraocular muscles using fast magnetic resonance imaging sequences and gaze fixation targets. We recruited 20 healthy volunteers and optimized fat-suppressed fast T1-weighted gradient-recalled echo (FS T1-GRE) and single-shot fast spin-echo (SSFSE) imaging for evaluating extraocular muscles. With each eye at 40° abduction and adduction, we scanned the short-axis plane at the maximum diameter of the bilateral lateral and medial rectus muscles and measured the maximal cross-sectional area of the muscles during extension and contraction. We evaluated interobserver reproducibility and variability between the size measurements using the two MR sequences and the measurement reproducibility using FS T1-GRE imaging. The interobserver reproducibility in the muscle size measurements using FS T1-GRE and SSFSE imaging was excellent (r=0.93-0.94) and moderate to good (r=0.54-0.75), respectively. The interobserver variability was less with FS T1-GRE than SSFSE imaging (p<0.01). The reproducibility of the size measurement using FS T1-GRE was good to excellent (r=0.78-0.92). FS T1-GRE imaging with the subject staring at each of multiple targets is useful for evaluating precisely the size of extraocular muscles.

3-T direct MR arthrography of the wrist: Value of finger trap distraction to assess intrinsic ligament and triangular fibrocartilage complex tears

PurposeTo determine the value of applying finger trap distraction during direct MR arthrography of the wrist to assess intrinsic ligament and triangular fibrocartilage complex (TFCC) tears. Materials and methodsTwenty consecutive patients were prospectively investigated by three-compartment wrist MR arthrography. Imaging was performed with 3-T scanners using a three-dimensional isotropic (0.4mm) T1-weighted gradient-recalled echo sequence, with and without finger trap distraction (4kg). In a blind and independent fashion, two musculoskeletal radiologists measured the width of the scapholunate (SL), lunotriquetral (LT) and ulna-TFC (UTFC) joint spaces. They evaluated the amount of contrast medium within these spaces using a four-point scale, and assessed SL, LT and TFCC tears, as well as the disruption of Gilula's carpal arcs. ResultsWith finger trap distraction, both readers found a significant increase in width of the SL space (mean Δ=+0.1mm, p≤0.040), and noticed more contrast medium therein (p≤0.035). In contrast, the differences in width of the LT (mean Δ=+0.1mm, p≥0.057) and UTFC (mean Δ=0mm, p≥0.728) spaces, as well as the amount of contrast material within these spaces were not statistically significant (p=0.607 and ≥0.157, respectively). Both readers detected more SL (Δ=+1, p=0.157) and LT (Δ=+2, p=0.223) tears, although statistical significance was not reached, and Gilula's carpal arcs were more frequently disrupted during finger trap distraction (Δ=+5, p=0.025). ConclusionThe application of finger trap distraction during direct wrist MR arthrography may enhance both detection and characterisation of SL and LT ligament tears by widening the SL space and increasing the amount of contrast within the SL and LT joint spaces.

Usefulness of three-dimensional T1-weighted spoiled gradient-recalled echo and three-dimensional heavily T2-weighted images in preoperative evaluation of spinal dysraphism

The aim of this study was to evaluate the usefulness of three-dimensional T1-weighted spoiled gradient-recalled echo (3D T1-GRE) images for the preoperative anatomical evaluation of lumbosacral lipoma, thick filum terminale, and myelomeningocele as a means of compensating for the drawbacks of 3D heavily T2-weighted (3D hT2-W) images. Nine patients with lumbosacral lipomas, one patient with tight filum terminale, and five patients with myelomeningoceles were included in this study. 3D T1-GRE images were compared with 3D hT2-W images or conventional magnetic resonance images in terms of delineation of lipomas and other structures in the patients with lipomas and tight filum terminale. For patients with myelomeningoceles, 3D T1-GRE images were compared with 3D hT2-W images in terms of artifacts in the cerebrospinal fluid (CSF) space. The 3D T1-GRE images demonstrated lipomas with good contrast to the spinal cord and CSF space and more clearly delineated the anatomical relationship between lipomas and these structures than did the 3D hT2-W images. The 3D T1-GRE images delineated dural defects through which extradural lipomas penetrated into the intradural space. The 3D T1-GRE images also demonstrated the presence or absence of lipomas in the filum terminale and the absence of artifact in the myelomeningoceles. Furthermore, they were useful for differentiating artifacts observed on the 3D hT2-W images from nerve elements. The complementary use of 3D T1-GRE and 3D hT2-W images may compensate for the drawbacks of 3D hT2-W images and may eventually improve lesion visualization and surgical decision making.

Dorsal Fractures of the Triquetrum: MRI Findings With an Emphasis on Dorsal Carpal Ligament Injuries

The objective of our study was to report the MRI findings in dorsal fractures of the triquetrum, with an emphasis on dorsal carpal ligament injuries. A total of 21 patients (16 men, five women; mean age, 41.9 years) with acute or subacute (≤ 6 weeks) dorsal triquetral fractures on radiography and MRI were included in this two-center retrospective study. MRI of the wrist was performed on 3-T units with transverse T1-weighted, coronal or transverse (or both) fat-suppressed T2weighted, transverse gadolinium-enhanced fat-suppressed T1-weighted turbo spin-echo, and 3D gadolinium-enhanced fat-suppressed T1-weighted gradient-recalled echo sequences. Three musculoskeletal radiologists evaluated the ulnar styloid process index (USPI) on radiographs and the following MRI features: fracture pattern (types 1-6), bone fragment size and displacement, bone marrow edema distribution, and dorsal carpal ligament tears. Eight type 1, one type 2, six type 3, five type 4, and one type 5 fractures were identified. These fractures were associated with 14 (66.7%), 17 (81.0%), and 16 (76.2%) tears of the dorsal radiocarpal, ulnotriquetral, and intercarpal ligaments, respectively. There was no correlation between bone marrow edema distribution and dorsal carpal ligament injuries (all p > 0.05). The mean (± SD) bone fragment volume and displacement were 205 ± 157 mm(3) and 1.0 ± 1.1 mm, respectively. The mean USPI was 0.21 ± 0.10. Dorsal fractures of the triquetrum are frequently associated with dorsal carpal ligament injuries. Bone marrow edema distribution is not correlated with these ligament tears.