Identification of single-dose, dual-echo based CBV threshold for fractional tumor burden mapping in recurrent glioblastoma

BackgroundRelative cerebral blood volume (rCBV) obtained from dynamic susceptibility contrast (DSC) MRI is widely used to distinguish high grade glioma recurrence from post treatment radiation effects (PTRE). Application of rCBV thresholds yield maps to distinguish between regional tumor burden and PTRE, a biomarker termed the fractional tumor burden (FTB). FTB is generally measured using conventional double-dose, single-echo DSC-MRI protocols; recently, a single-dose, dual-echo DSC-MRI protocol was clinically validated by direct comparison to the conventional double-dose, single-echo protocol. As the single-dose, dual-echo acquisition enables reduction in the contrast agent dose and provides greater pulse sequence parameter flexibility, there is a compelling need to establish dual-echo DSC-MRI based FTB mapping. In this study, we determine the optimum standardized rCBV threshold for the single-dose, dual-echo protocol to generate FTB maps that best match those derived from the reference standard, double-dose, single-echo protocol.MethodsThe study consisted of 23 high grade glioma patients undergoing perfusion scans to confirm suspected tumor recurrence. We sequentially acquired single dose, dual-echo and double dose, single-echo DSC-MRI data. For both protocols, we generated leakage-corrected standardized rCBV maps. Standardized rCBV (sRCBV) thresholds of 1.0 and 1.75 were used to compute single-echo FTB maps as the reference for delineating PTRE (sRCBV < 1.0), tumor with moderate angiogenesis (1.0 < sRCBV < 1.75), and tumor with high angiogenesis (sRCBV > 1.75) regions. To assess the sRCBV agreement between acquisition protocols, the concordance correlation coefficient (CCC) was computed between the mean tumor sRCBV values across the patients. A receiver operating characteristics (ROC) analysis was performed to determine the optimum dual-echo sRCBV threshold. The sensitivity, specificity, and accuracy were compared between the obtained optimized threshold (1.64) and the standard reference threshold (1.75) for the dual-echo sRCBV threshold.ResultsThe mean tumor sRCBV values across the patients showed a strong correlation (CCC = 0.96) between the two protocols. The ROC analysis showed maximum accuracy at thresholds of 1.0 (delineate PTRE from tumor) and 1.64 (differentiate aggressive tumors). The reference threshold (1.75) and the obtained optimized threshold (1.64) yielded similar accuracy, with slight differences in sensitivity and specificity which were not statistically significant (1.75 threshold: Sensitivity = 81.94%; Specificity: 87.23%; Accuracy: 84.58% and 1.64 threshold: Sensitivity = 84.48%; Specificity: 84.97%; Accuracy: 84.73%).ConclusionsThe optimal sRCBV threshold for single-dose, dual-echo protocol was found to be 1.0 and 1.64 for distinguishing tumor recurrence from PTRE; however, minimal differences were observed when using the standard threshold (1.75) as the upper threshold, suggesting that the standard threshold could be used for both protocols. While the prior study validated the agreement of the mean sRCBV values between the protocols, this study confirmed that their voxel-wise agreement is suitable for reliable FTB mapping. Dual-echo DSC-MRI acquisitions enable robust single-dose sRCBV and FTB mapping, provide pulse sequence parameter flexibility and should improve reproducibility by mitigating variations in preload dose and incubation time

Value of prominent flow voids without cord edema in the detection of spinal arteriovenous fistulae

Purpose: To determine the prevalence of spinal dural arteriovenous fistulae (SDAVF) in patients presenting with prominent vascular flow voids on imaging without other imaging findings suggestive of SDAVF. Methods: We retrospectively identified patients from January 1, 2005 to March 1, 2012 who underwent spinal angiography for suspected SDAVF with prominent vascular flow voids on prior imaging. We excluded patients with other major spinal pathology or other imaging findings of SDAVF including cord hyperintensity, enhancement, or expansion. We calculated the proportion of patients with positive findings for SDAVF on angiography and evaluated the prevalence of SDAVF for this finding alone and in correlation with clinical findings. Results: 18 patients underwent spinal angiography for prominent flow voids on imaging without other spinal pathology or imaging findings of SDAVF. Three had a SDAVF detected on angiography. The prevalence of SDAVF in this population was low, only 17% (95% CI 6-39%). All of the patients with positive angiography findings had myelopathy, increasing the prevalence to 100% if the additional clinical finding of myelopathy was present. Conclusions: Prominent flow voids without other imaging findings suggestive of SDAVF is poorly predictive of the presence of a SDAVF, unless myelopathy is present clinically. © 2014 Alhilali et al

A multi-disciplinary model of risk factors for fatal outcome in posterior reversible encephalopathy syndrome

PURPOSE: To evaluate the relative impact of clinical data, imaging findings, and CSF laboratory values on clinical outcome in patients with posterior reversible encephalopathy syndrome (PRES). METHODS: 47 patients with PRES who underwent a lumbar puncture were retrospectively evaluated. Fatal outcome was defined as death directly ascribed to PRES toxicity. Univariate and multivariate analyses were used to evaluate the association between fatal outcome and clinical factors (demographics, PRES etiology), imaging findings (signal abnormality severity, atypical distribution, restricted diffusion, hemorrhage, enhancement, angiographic abnormalities), and lumbar puncture results (appearance, cell count, glucose, protein, culture results). RESULTS: Nine patients (19.1%) had a fatal outcome. Odds of a fatal outcome increased nearly 5-fold with hemorrhage on imaging (Adjusted Odds Ratio (AOR) 4.8, 95% CI 3.8-6.0, p=0.03) and nearly doubled with low CSF glucose (AOR 1.9, 95% CI 1.5-2.5, p=0.02). Hypertensive encephalopathy as an etiology was associated with a fatal outcome (AOR 1.6, 95% CI 1.3-2.9, p=0.02), while toxemia of pregnancy was protective, with a 75% decreased risk (AOR 0.25, 95% CI 0.15-0.43, p=0.02). CONCLUSION: Clinical, imaging, and CSF laboratory findings all influence outcome in PRES, with a low CSF glucose, hypertensive encephalopathy, and imaging findings of hemorrhage associated with increased risk of fatal outcome

Evaluation of a limited three-slice head CT protocol for monitoring patients with ventriculoperitoneal shunts

OBJECTIVE: Patients with a ventriculoperitoneal shunt for the management of hydrocephalus often undergo multiple head CT examinations for assessment of shunt malfunction. The purpose of this study was to evaluate whether a limited three-slice CT protocol would consistently provide adequate information for the diagnosis of shunt malfunction with a decrease in effective dose. MATERIALS AND METHODS: The study group included 231 unenhanced head CT examinations performed on 128 patients with shunts for hydrocephalus. The original contiguous CT images were reviewed retrospectively. A theoretic limited three-slice study was then created from the original complete CT study and separately reviewed. This limited three-slice study was created by using the lateral topographic image to select three axial locations as follows: midpoint between foramen magnum and vertex, top of the mastoid air cells, and orbital roof. The limited study was graded for parameters of image adequacy with the original full protocol study as the reference standard. RESULTS: Twenty-four of the 231 (10.4%) full studies had findings consistent with shunt failure; all 231 studies would have been correctly categorized with the limited three-slice protocol. The sensitivity of three-slice CT for identifying the ventricular system was 91.6% and for identifying the catheter tip, 93.5%. Limited-slice CT examination would have resulted in greater than 90% mean dose reduction in both adult and pediatric populations. CONCLUSION: Unenhanced head CT with a limited-slice protocol provides adequate diagnostic information for the diagnosis of shunt malfunction with a greater than 90% reduction in effective dose

Detection of central white matter injury underlying vestibulopathy after mild traumatic brain injury

PURPOSE: To determine if central axonal injury underlies vestibulopathy and ocular convergence insufficiency after mild traumatic brain injury (TBI) by using tract-based spatial statistics (TBSS) analysis of diffusion-tensor imaging (DTI). MATERIALS AND METHODS: The institutional review board approved this study, and the requirement to obtain informed consent was waived. Diffusion-tensor images were retrospectively reviewed in 30 patients with mild TBI and vestibular symptoms and 25 patients with mild TBI and ocular convergence insufficiency. Control subjects consisted of 39 patients with mild TBI without vestibular abnormalities and 17 patients with mild TBI and normal ocular convergence. Fractional anisotropy (FA) maps were generated as a measure of white matter integrity and were analyzed with TBSS regression analysis by using a general linear model. DTI abnormalities were correlated with symptom severity, neurocognitive test scores, and time to recovery with the Pearson correlation coefficient. RESULTS: Compared with control subjects, patients with mild TBI and vestibular symptoms had decreased neurocognitive test scores (P \u3c .05) and FA values in the cerebellum and fusiform gyri (P \u3c .05). Patients with ocular convergence insufficiency had diminished neurocognitive test scores (P \u3c .05) and FA values in the right anterior thalamic radiation and right geniculate nucleus optic tracts (P \u3c .0001). Cerebellar injury showed an inverse correlation with recovery time (R = -0.410, P = .02). Anterior thalamic radiation injury showed correlation with decreased processing speed (R = 0.402, P \u3c .05). CONCLUSION: DTI findings in patients with mild TBI and vestibulopathy support the hypothesis that posttraumatic vestibulopathy has a central axonal injury component. Peripheral vestibular structures were not assessed, and a superimposed peripheral contribution may exist. DTI evaluation of central vestibular structures may provide a diagnostic imaging tool in these patients and a quantitative biomarker to aid in prognosis

Evaluation of White Matter Injury Patterns Underlying Neuropsychiatric Symptoms after Mild Traumatic Brain Injury

PURPOSE: To determine if a central axonal injury underlies neuropsychiatric symptoms after mild traumatic brain injury (mTBI) by using tract-based spatial statistics analysis of diffusion-tensor images. MATERIALS AND METHODS: The institutional review board approved this study, with waiver of informed consent. Diffusion-tensor imaging and serial neurocognitive testing with the Immediate Post-Concussion Assessment and Cognitive Testing evaluation were performed in 45 patients with mTBI (38 with irritability, 32 with depression, and 18 with anxiety). Control subjects consisted of 29 patients with mTBI without neuropsychiatric symptoms. Fractional anisotropy and diffusivity maps were analyzed by using tract-based spatial statistics with a multivariate general linear model. Diffusion-tensor imaging findings were correlated with symptom severity, neurocognitive test scores, and time to recovery with the Pearson correlation coefficient. RESULTS: Compared with control subjects, patients with mTBI and depression had decreased fractional anisotropy in the superior longitudinal fasciculus (P = .006), white matter around the nucleus accumbens (P = .03), and anterior limb of the internal capsule (P = .02). Patients with anxiety had diminished fractional anisotropy in the vermis (P = .04). No regions of significantly decreased fractional anisotropy were seen in patients with irritability relative to control subjects. Injury in the region of the nucleus accumbens inversely correlated with recovery time in patients with depression (r = -0.480, P = .005). CONCLUSION: Unique white matter injury patterns were seen for two major posttraumatic neuropsychiatric symptoms. Injury to the cerebellar vermis in patients with mTBI and anxiety may indicate underlying dysfunction in primitive fear conditioning circuits in the cerebellum. Involvement of the nucleus accumbens in depression after mTBI may suggest an underlying dysfunctional reward circuit that affects the prognosis in these patients

White Matter Microstructural Differences between Essential Tremor and Parkinson Disease, Evaluated Using Advanced Diffusion MRI Biomarkers

Background: Essential tremor (ET) is a common slowly-progressive neurologic disorder. It is predominantly characterized by kinetic tremors involving bilateral upper limbs. Although ET shares motor similarities with Parkinson disease (PD), there is no known relationship between ET and PD. Methods: We studied white matter differences between 17 ET and 68 PD patients using standard diffusion tensor imaging and fixel-based analysis (FBA). Diffusion magnetic resonance imaging data were acquired from two scanners (General Electric (GE) and Philips) with different numbers of diffusion directions. Fractional anisotropy maps were generated by the Oxford Centre for Functional Magnetic Resonance Imaging of the Brain (FMRIB) Software Library (FSL), and FBA was performed using MRtrix3 to obtain fiber density, fiber bundle, and fiber density bundle cross-section. Results: Compared with PD, significantly lower values of fiber density, fiber bundle, and fiber density bundle cross-section were found in the corpus callosum and left tapetum of the ET group. Additionally, significantly lower functional anisotropy values were found in the ET compared to the PD group, principally in the corpus callosum, corona radiata, and cingulum. In conclusion, differences in white matter integrity between ET and PD were observed by both FBA-based metrics and diffusion tensor imaging. Conclusions: Advanced diffusion-based metrics may provide a better understanding of the white matter microstructural characteristics in disparate motor-associated diseases with different underlying phenotypes, such as ET and PD

Omental infarct: an unusual CT appearance after superior mesenteric artery occlusion

We report a case of omental infarct resulting from superior mesenteric artery occlusion, which had an unusual appearance on computed tomography

White Matter Injuries in Mild Traumatic Brain Injury and Posttraumatic Migraines: Diffusion Entropy Analysis

Purpose To determine the performance of Shannon entropy (SE) as a diagnostic tool in patients with mild traumatic brain injury (mTBI) with posttraumatic migraines (PTMs) and those without PTMs on the basis of analysis of fractional anisotropy (FA) maps. Materials and Methods The institutional review board approved this retrospective study, with waiver of informed consent. FA maps were obtained and neurocognitive testing was performed in 74 patients with mTBI (57 with PTM, 17 without PTM). FA maps were obtained in 22 healthy control subjects and in 20 control patients with migraine headaches. Mean FA and SE were extracted from total brain FA histograms and were compared between patients with mTBI and control subjects and between patients with and those without PTM. Mean FA and SE were correlated with clinical variables and were used to determine the areas under the receiver operating characteristic curve (AUCs) and likelihood ratios for mTBI and development of PTM. Results Patients with mTBI had significantly lower SE (P \u3c .001) and trended toward lower mean FA (P = .07) compared with control subjects. SE inversely correlated with time to recovery (TTR) (r = -0.272, P = .02). Patients with mTBI with PTM had significantly lower SE (P \u3c .001) but not mean FA (P = .15) than did other patients with mTBI. SE provided better discrimination between patients with mTBI and control subjects than mean FA (AUC = 0.92; P = .01), as well as better discrimination between patients with mTBI with PTM and those without PTM (AUC = 0.85; P \u3c .001). SE of less than 0.751 resulted in a 16.1 increased likelihood of having experienced mTBI and a 3.2 increased likelihood of developing PTM. Conclusion SE more accurately reveals mTBI than mean FA, more accurately reveals those patients with mTBI who develop PTM, and inversely correlates with TTR. (©) RSNA, 2016