First-Pass Contrast-Enhanced MRA for Pretherapeutic Diagnosis of Spinal Epidural Arteriovenous Fistulas with Intradural Venous Reflux.

BACKGROUND AND PURPOSE: Spinal epidural AVFs are rare spinal vascular malformations. When there is associated intradural venous reflux, they may mimic the more common spinal dural AVFs. Correct diagnosis and localization before conventional angiography is beneficial to facilitate treatment. We hypothesize that first-pass contrast-enhanced MRA can diagnose and localize spinal epidural AVFs with intradural venous reflux and distinguish them from other spinal AVFs. MATERIALS AND METHODS: Forty-two consecutive patients with a clinical and/or radiologic suspicion of spinal AVF underwent MR imaging, first-pass contrast-enhanced MRA, and DSA at a single institute (2000-2015). MR imaging/MRA and DSA studies were reviewed by 2 independent blinded observers. DSA was used as the reference standard. RESULTS: On MRA, all 7 spinal epidural AVFs with intradural venous reflux were correctly diagnosed and localized with no interobserver disagreement. The key diagnostic feature was arterialized filling of an epidural venous pouch with a refluxing radicular vein arising from the arterialized epidural venous system. CONCLUSIONS: First-pass contrast-enhanced MRA is a reliable and useful technique for the initial diagnosis and localization of spinal epidural AVFs with intradural venous reflux and can distinguish these lesions from other spinal AVFs.

First-Pass Contrast-Enhanced MR Angiography in Evaluation of Treated Spinal Arteriovenous Fistulas: Is Catheter Angiography Necessary?

BACKGROUND AND PURPOSE: Catheter angiography is typically used for follow-up of treated spinal AVFs. The purpose of this study was to determine the diagnostic performance and utility of first-pass contrast-enhanced MRA in the posttreatment evaluation of spinal AVFs compared with DSA. MATERIALS AND METHODS: A retrospective review was performed of all patients at our tertiary referral hospital (from January 2000 to April 2015) who underwent spine MR imaging, first-pass contrast-enhanced MRA, and DSA after surgical and/or endovascular treatment of a spinal AVF. Presence of recurrent or residual fistula on MRA, including vertebral level of the recurrent/residual fistula, was evaluated by 2 experienced neuroradiologists blinded to DSA findings. Posttreatment conventional MR imaging findings were also evaluated, including presence of intramedullary T2 hyperintensity, perimedullary serpentine flow voids, and cord enhancement. The performance of MRA and MR imaging findings for diagnosis of recurrent/residual fistula was determined by using DSA as the criterion standard. RESULTS: In total, 28 posttreatment paired MR imaging/MRA and DSA studies were evaluated in 22 patients with prior spinal AVF and 1 patient with intracranial AVF with prior cervical perimedullary venous drainage. Six image sets of 5 patients demonstrated recurrent/residual disease at DSA. MRA correctly identified all cases with recurrent/residual disease with 1 false-positive (sensitivity, 100%; specificity 95%; P < .001), with correct localization in all cases without interobserver disagreement. Conventional MR imaging parameters were not significantly associated with recurrent/residual spinal AVF. CONCLUSIONS: First-pass MRA demonstrates high sensitivity and specificity for identifying recurrent/residual spinal AVFs and may potentially substitute for DSA in the posttreatment follow-up of patients with spinal AVFs.

Comparison of Time-Resolved and First-Pass Contrast-Enhanced MR Angiography in Pretherapeutic Evaluation of Spinal Dural Arteriovenous Fistulas.

BACKGROUND AND PURPOSE: Different MRA techniques used to evaluate spinal dural arteriovenous fistulas offer unique advantages and limitations with regards to temporal and spatial resolution. The purpose of this study was to compare the efficacy and interobserver agreement of 2 commonly used contrast-enhanced spinal MRA techniques, multiphase time-resolved MRA and single-phase first-pass MRA, in assessment of spinal dural arteriovenous fistulas. MATERIALS AND METHODS: Retrospective review of 15 time-resolved and 31 first-pass MRA studies in patients with clinical suspicion of spinal dural arteriovenous fistula was performed by 2 independent, blinded observers. DSA was used as the reference standard to compare the diagnostic performance of the 2 techniques. RESULTS: There were 10 cases of spinal dural arteriovenous fistula in the time-resolved MRA group and 20 in the first-pass MRA group. Time-resolved MRA detected spinal dural arteriovenous fistulas with sensitivity and specificity of 100% and 80%, respectively, with 100% correct-level localization rate. First-pass MRA detected spinal dural arteriovenous fistulas with sensitivity and specificity of 100% and 82%, respectively, with 87% correct-level localization rate. Interobserver agreement for localization was excellent for both techniques; however, it was higher for time-resolved MRA. In 5 cases, the site of fistula was not included in the FOV, but a prominent intradural radicular vein was observed at the edge of the FOV. CONCLUSIONS: Multiphase time-resolved MRA and single-phase first-pass MRA were comparable in diagnosis and localization of spinal dural arteriovenous fistulas and demonstrated excellent interobserver agreement, though there were more instances of ambiguity in fistula localization on first-pass MRA.

Modeling the pattern of contrast extravasation in acute intracerebral hemorrhage using dynamic contrast-enhanced MR.

BACKGROUND: Contrast extravasation (CE) in spontaneous intracerebral hemorrhage (ICH), coined the spot sign, predicts hematoma expansion (HE) and poor clinical outcome. The dynamic relationship between CE and the mode of ICH growth are poorly understood. We characterized the in vivo pattern and rate of HE using a novel animal model of acute ICH. METHODS: Basal ganglia ICH was created in 14 Yorkshire swine utilizing a novel MRI integrated model, permitting real-time CE observation using dynamic contrast-enhanced (DCE) MRI. Computerized planimetry measured CE volume at each time point. Spatial vector analysis along three orthogonal axes determined distance vectors. Maximizing and minimizing the coefficient of determination defined the temporal phases of growth and stability, respectively. CE rate was calculated using a Patlak model. RESULTS: Asymmetric growth and variable rates of expansion characterized HE defining three distinct growth phases and patterns. A primary growth phase (duration 160 s; IQR 50-130) demonstrated rapid linear growth (0.04 mm/s IQR 0.01-0.10) accounting for 85 ± 15 % of total HE. The stationary phase demonstrated stability (duration 145 s; IQR 0-655). A secondary growth phase (duration 300; 130-600 s) accounted for 23 ± 8 % of total HE. In the primary and secondary growth phase, asymmetric growth occurred in the anterior-posterior (AP) planes (0.056 mm/s; p = 0.026 and 0.0112 mm/s; p = 0.03). Monophasic 2 (14 %), biphasic 4 (35 %) (primary followed by secondary growth), and triphasic 8 (56 %) patterns (primary, stationary, and secondary growth phase) were observed. CONCLUSIONS: A novel model of ICH provides real-time study of the dynamics and rate of CE. This data facilitates the understanding of pattern and rate of ICH formation.

CT perfusion spot sign improves sensitivity for prediction of outcome compared with CTA and postcontrast CT.

BACKGROUND AND PURPOSE: Recent studies have recommended both early and late imaging to increase spot sign detection. However optimal acquisition timing for spot detection and impact on outcome prediction is uncertain. Our aim was to assess the utility of CTP in spot sign detection and characterization with emphasis on its impact on the prediction of outcome in patients with acute primary ICH. MATERIALS AND METHODS: A retrospective review of 28 patients presenting within 6 hours of ICH, studied with CTA, CTP, and postcontrast CT, was performed. CTA, CTP, and postcontrast CT spot sign characteristics were recorded according to predefined radiologic criteria. A combined primary outcome of hematoma expansion or poor clinical outcome was used and defined as hematoma expansion ≥6 mL or ≥30%, need for surgical drainage, or in-hospital mortality. Associations with the primary outcome and spot sign presence were examined against baseline clinical, laboratory, and radiographic variables. Predictive ability of CTA, CTP, and postcontrast CT spot characteristics were compared among modalities. RESULTS: Primary outcome criteria were met in 18 patients (61%). CTP spot sign presence was an independent predictor of hematoma expansion or poor outcome (P = .040) and demonstrated greater sensitivity (78%) than spots detected on CTA (44%, P = .034) and postcontrast CT (50%, P = .025). Specificity and positive predictive value of the spot sign was high (100%) on all modalities. CTP detected the greatest number of spots (80%) with peak spot attenuation demonstrated at a median (interquartile range) time of 50 seconds (range, 34-63 seconds) after contrast bolus injection. CTP spot appearance was later than CTA-detected spots (P = .002) and earlier than postcontrast CT spots (P < .001). CONCLUSIONS: CTP spot sign detection improves the sensitivity for prediction of outcome compared with CTA or postcontrast CT-detected spots.

CT perfusion quantification of small-vessel ischemic severity.

BACKGROUND AND PURPOSE: Cerebral blood flow (CBF) abnormalities are previously demonstrated in white matter disease. A gradation of change may exist between patients with mild and more severe white matter disease. An association between blood brain barrier dysfunction, increasing age and white matter disease is also suggested. The purpose of this study was to quantify and correlate white matter disease severity and CT perfusion (CTP)-derived CBF and to determine whether permeability surface abnormality increases with white matter disease severity. MATERIALS AND METHODS: One hundred twenty patients with strokelike symptoms underwent CTP and MR imaging. Of these, 35 patients (15 women, 20 men; age, 66 +/- 15.7 years) with rapidly resolving symptoms and normal imaging characteristics consistent with transient ischemic attack were retrospectively reviewed and constituted the study cohort. Two blinded neurologists rated white matter severity, assigning age-related white matter change (ARWMC) scores. Patients were dichotomized a priori into mild and moderate-to-severe. CBF, cerebral blood volume (CBV), mean transit time (MTT), and permeability surface product maps were calculated for periventricular and subcortical white matter regions and average white and gray matter. Associations with white matter severity were tested by uni- and multivariate logistic regression analyses. Receiver operating characteristic analysis was performed. RESULTS: White matter disease was mild in 26 patients and moderate-to-severe in 9. Age was associated with increased likelihood of having moderate-to-severe white matter disease (P = .02). ARWMC correlated with subcortical (r = -0.50, P < .001) and average CBF (r = -0.55, P < .001). White matter severity was associated with subcortical (P = .03) and average (P = .03) white matter CBF, with a trend toward periventricular white matter CBF (P = .05). Uni- and multivariate analysis controlling for the confounding effect of age demonstrated significant association between white matter severity and subcortical (P = .032) white matter CBF. Area under the curve was 0.82. No permeability surface abnormality was found. CONCLUSIONS: CTP-derived subcortical white matter CBF is independently associated with white matter disease severity.