F.J.A. Meijer

4D-CTA in Neurovascular Disease: A Review

SUMMARY: CT angiography is a widely used technique for the noninvasive evaluation of neurovascular pathology. Because CTA is a snapshot of arterial contrast enhancement, information on flow dynamics is limited. Dynamic CTA techniques, also referred to as 4D-CTA, have become available for clinical practice in recent years. This article provides a description of 4D-CTA techniques and a review of the available literature on the application of 4D-CTA for the evaluation of intracranial vascular malformations and hemorrhagic and ischemic stroke. Most of the research performed to date consists of observational cohort studies or descriptive case series. These studies show that intracranial vascular malformations can be adequately depicted and classified by 4D-CTA, with DSA as the reference standard. In ischemic stroke, 4D-CTA better estimates thrombus burden and the presence of collateral vessels than conventional CTA. In intracranial hemorrhage, 4D-CTA improves the detection of the “spot” sign, which represents active ongoing bleeding.

Update on diffusion MRI in Parkinson's disease and atypical parkinsonism

Differentiating Parkinsons disease (PD) from other types of neurodegenerative atypical parkinsonism (AP) can be challenging, especially in early disease stages. Routine brain magnetic resonance imaging (MRI) can show atrophy or signal changes in several parts of the brain with fairly high specificity for particular forms of AP, but the overall diagnostic value of routine brain MRI is limited. In recent years, various advanced MRI sequences have become available, including diffusion weighted imaging (DWI) and diffusion tensor imaging (DTI). Here, we review available literature on the value of diffusion MRI for identifying and quantifying different patterns of neurodegeneration in PD and AP, in relation to what is known of underlying histopathologic changes and clinical presentation of these diseases. Next, we evaluate the value of diffusion MRI to differentiate between PD and AP and the potential value of serial diffusion MRI to monitor disease progression. We conclude that diffusion MRI may quantify patterns of neurodegeneration which could be of additional value in clinical use. Future prospective clinical cohort studies are warranted to assess the added diagnostic value of diffusion MRI.

MRA versus DSA for follow-up of coiled intracranial aneurysms: a meta-analysis.

MR angiography is proposed as a safer and less expensive alternative to the reference standard, DSA, in the follow-up of intracranial aneurysms treated with endovascular coil occlusion. We performed a systematic review and meta-analysis to evaluate the accuracy of TOF-MRA and contrast-enhanced MRA in detecting residual flow in the follow-up of coiled intracranial aneurysms. Literature was reviewed through the PubMed, Cochrane, and EMBASE data bases. In comparison with DSA, the sensitivity of TOF-MRA was 86% (95% CI: 82-89%), with a specificity of 84% (95% CI: 81-88%), for the detection of any recurrent flow. For contrast-enhanced MRA, the sensitivity and specificity were 86% (95% CI: 82-89%) and 89% (95% CI: 85-92%), respectively. Both TOF-MRA and contrast-enhanced MRA are shown to be highly accurate for detection of any recanalization in intracranial aneurysms treated with endovascular coil occlusion.

Susceptibility-Weighted Imaging Improves the Diagnostic Accuracy of 3T Brain MRI in the Work-Up of Parkinsonism

BACKGROUND AND PURPOSE: The differentiation between Parkinson disease and atypical parkinsonian syndromes can be challenging in clinical practice, especially in early disease stages. Brain MR imaging can help to increase certainty about the diagnosis. Our goal was to evaluate the added value of SWI in relation to conventional 3T brain MR imaging for the diagnostic work-up of early-stage parkinsonism. MATERIALS AND METHODS: This was a prospective observational cohort study of 65 patients presenting with parkinsonism but with an uncertain initial clinical diagnosis. At baseline, 3T brain MR imaging with conventional and SWI sequences was performed. After clinical follow-up, probable diagnoses could be made in 56 patients, 38 patients diagnosed with Parkinson disease and 18 patients diagnosed with atypical parkinsonian syndromes, including 12 patients diagnosed with multiple system atrophy–parkinsonian form. In addition, 13 healthy controls were evaluated with SWI. Abnormal findings on conventional brain MR imaging were grouped into disease-specific scores. SWI was analyzed by a region-of-interest method of different brain structures. One-way ANOVA was performed to analyze group differences. Receiver operating characteristic analyses were performed to evaluate the diagnostic accuracy of conventional brain MR imaging separately and combined with SWI. RESULTS: Disease-specific scores of conventional brain MR imaging had a high specificity for atypical parkinsonian syndromes (80%–90%), but sensitivity was limited (50%–80%). The mean SWI signal intensity of the putamen was significantly lower for multiple system atrophy–parkinsonian form than for Parkinson disease and controls (P < .001). The presence of severe dorsal putaminal hypointensity improved the accuracy of brain MR imaging: The area under the curve was increased from 0.75 to 0.83 for identifying multiple system atrophy–parkinsonian form, and it was increased from 0.76 to 0.82 for identifying atypical parkinsonian syndromes as a group. CONCLUSIONS: SWI improves the diagnostic accuracy of 3T brain MR imaging in the work-up of parkinsonism by identifying severe putaminal hypointensity as a sign indicative of multiple system atrophy–parkinsonian form.

4D-CT angiography differentiating arteriovenous fistula subtypes

OBJECTIVE AND METHODS In the diagnostic work-up of patients suspected of a dural arteriovenous fistula (dAVF), imaging has a key role in order to diagnose the dAVF, assess its bleeding risk and choose optimal treatment strategy. Digital subtraction angiography (DSA) is the gold standard for the most detailed image of a dAVF. Nowadays four-dimensional CT angiography (4D-CTA) could possibly be an additional first-line tool in the work-up of a patient suspected of a dAVF. We describe three cases clinically suspected of a dAVF which had a diagnostic work-up with 4D-CTA as well as DSA. We evaluated the angioarchitecture of the dAVF both on 4D-CTA and DSA, with emphasis on the patterns of venous drainage as this is important in assessing the bleeding risk of a dAVF. RESULTS AND CONCLUSION 4D-CTA identified the dAVF, revealed its angioarchitecture and correctly differentiated different patterns of venous drainage (Borden type I, II and III) as confirmed on DSA. Although DSA has the advantage of higher spatial and temporal resolution, 4D-CTA seems to be a new useful non-invasive tool in the diagnostic work-up of a patient suspected of a dAVF.

The additional value of three time point color coding in dynamic contrast-enhanced MRI of the breast for inexperienced and experienced readers

PURPOSE To evaluate the additional value of the color coding of dynamic data using the 3TP method in the evaluation of contrast-enhanced breast MRI for readers with different levels of experience. MATERIALS AND METHODS A total of 52 lesions were included in this study, 25 malignant and 27 benign. All lesions were evaluated by four readers on two different workstations for the evaluation of dynamic breast MRI; one displaying the subtracted images and relative enhancement versus time curves and one displaying the subtracted images together with the 3TP color coding projected onto pre-contrast T1 images. Readers with different levels of experience were used. The diagnostic performance of both workstations was evaluated using ROC curve analyses. Interobserver variations were evaluated using kappa statistics. RESULTS All lesions were detected by all four readers on both workstations. The diagnostic performance found in the inexperienced readers improved significantly when using the 3TP evaluations (p=0.04 and p=0.03). No significant difference was found for the more experienced readers (p=0.94 and p=0.54). The level of agreement between the readers improved significantly when using the 3TP evaluation method (p=0.01). CONCLUSION Even though the 3TP color coding did not improve the diagnostic performance of the more experienced readers, this study clearly shows its value for inexperienced readers. The use of 3TP color coding is therefore recommended for inexperienced readers.

Nigrosome-1 on Susceptibility Weighted Imaging to Differentiate Parkinson’s Disease From Atypical Parkinsonism: An In Vivo and Ex Vivo Pilot Study

Summary Background Previous case-control studies have suggested that the absence of a swallow-tail appearance in the substantia nigra on high-resolution SWI, representing nigrosome-1, has high accuracy to identify Parkinson’s disease (PD). The first goal of our study was to evaluate nigrosome-1 ex vivo using optimized high-resolution susceptibility sensitive MRI. Our second goal was to evaluate its diagnostic value in vivo using a clinical 3T SWI sequence to differentiate between PD and atypical parkinsonism (AP) in a cohort of patients with early-stage parkinsonism. Material/Methods Case-control pilot study to evaluate nigrosome-1 ex vivo (2 PD, 2 controls), using high-resolution susceptibility sensitive sequences at 11.7 T MRI. Next, evaluation of nigrosome-1 in vivo using a clinical 3 T SWI sequence in a prospective cohort of 60 patients with early-stage parkinsonism (39 PD, 21 AP). Moreover, 12 control subjects were scanned. The bilateral substantia nigra was evaluated by two neuroradiologists for the presence, absence or indecisive presence of nigrosome-1. The discriminative power was evaluated by Receiver-Operating Characteristic. Results We identified nigrosome-1 in ex vivo control subjects. Nigrosome-1 was not identified in the ex vivo PD cases. In our prospective clinical cohort study, the AUC for the swallow-tail sign to discriminate between PD and AP was 0.56 (0.41–0.71) for reader 1 and 0.68 (0.55–0.82) for reader 2. Conclusions The diagnostic accuracy of the swallow-tail sign was marginal to discriminate between PD and AP using our clinical 3 T SWI sequence.

Cortical Venous Filling on Dynamic Computed Tomographic Angiography A Novel Predictor of Clinical Outcome in Patients With Acute Middle Cerebral Artery Stroke

Background and Purpose— Venous flow in the downstream territory of an occluded artery may influence patient prognosis after ischemic stroke. Our aim was to study cortical venous filling (CVF) in a time-resolved manner with dynamic computed tomographic angiography and to assess the relationship with clinical outcome. Methods— Patients with a proximal middle cerebral artery occlusion underwent noncontrast CT and whole-brain CT perfusion/dynamic CT angiography within 9 hours after stroke-onset. We defined poor outcome as a modified Rankin Scale score of ≥3. Association between the extent and velocity of CVF and poor outcome at 3 months was analyzed with Poisson-regression. Prognostic value of optimal CVF (maximum opacification of cortical veins) in addition to age, stroke severity, treatment, Alberta Stroke Program Early CT score, cerebral blood flow, and collateral status was assessed with logistic regression and summarized with the area under the curve. Results— Eighty-eight patients were included, with a mean age of 67 years. By combining the extent and velocity of optimal CVF, we observed a decreased risk of poor outcome in patients with good and fast optimal CVF, risk ratio of 0.5 (95% confidence interval, 0.3–0.7). Extent and velocity of optimal CVF had additional prognostic value (area under the curve, 0.88; 95% confidence interval, 0.77–0.98; P<0.02) compared with a model without CVF information. Conclusions— The combination of extent and velocity of optimal CVF, as assessed with dynamic CT angiography, is useful to identify patients with acute middle cerebral artery stroke at higher risk of poor clinical outcome at 3-month follow-up. Clinical Trial Registration— URL: http://www.trialregister.nl/trialreg and http://www.clinicaltrials.gov. Unique identifier: NTR1804 and NCT00880113, respectively.

Timing-Invariant CT Angiography Derived from CT Perfusion Imaging in Acute Stroke: A Diagnostic Performance Study

BACKGROUND AND PURPOSE: Timing-invariant (or delay-insensitive) CT angiography derived from CT perfusion data may obviate a separate cranial CTA in acute stroke, thus enhancing patient safety by reducing total examination time, radiation dose, and volume of contrast material. We assessed the diagnostic accuracy of timing-invariant CTA for detecting intracranial artery occlusion in acute ischemic stroke, to examine whether standard CTA can be omitted. MATERIALS AND METHODS: Patients with suspected ischemic stroke were prospectively enrolled and underwent CTA and CTP imaging at admission. Timing-invariant CTA was derived from the CTP data. Five neuroradiologic observers assessed all images for the presence and location of intracranial artery occlusion in a blinded and randomized manner. Sensitivity and specificity of timing-invariant CTA and standard CTA were calculated by using an independent expert panel as the reference standard. Interrater agreement was determined by using κ statistics. RESULTS: We included 108 patients with 47 vessel occlusions. Overall, standard CTA and timing-invariant CTA provided similar high diagnostic accuracy for occlusion detection with a sensitivity of 96% (95% CI, 90%–100%) and a specificity of 100% (99%–100%) for standard CTA and a sensitivity of 98% (95% CI, 94%–100%) and a specificity of 100% (95% CI, 100%–100%) for timing-invariant CTA. For proximal large-vessel occlusions, defined as occlusions of the ICA, basilar artery, and M1, the sensitivity and specificity were 100% (95% CI, 100%–100%) for both techniques. Interrater agreement was good for both techniques (mean κ value, 0.75 and 0.76). CONCLUSIONS: Timing-invariant CTA derived from CTP data provides diagnostic accuracy similar to that of standard CTA for the detection of artery occlusions in acute stroke.

Residual High-Grade Stenosis After Recanalization of Extracranial Carotid Occlusion in Acute Ischemic Stroke

Background and Purpose— Residual stenosis after recanalization of an acute symptomatic extracranial occlusion of the internal carotid artery (ICA) might be an indication for carotid endarterectomy. We evaluated the proportion of residual high-grade stenosis (≥70%, near occlusions not included) on follow-up imaging in a consecutive series of patients with an acute symptomatic occlusion of the extracranial ICA. Methods— We included patients participating in the Dutch Acute Stroke Study (DUST), who had an acute symptomatic occlusion of the extracranial ICA that was diagnosed on computed tomographic angiography within 9 hours after onset of neurological symptoms. Follow-up imaging of the carotid artery had to be available within 7 days after admission. Results— Of the 1021 patients participating in DUST between May 2009 and May 2013, an acute symptomatic occlusion of the extracranial ICA was found in 126 (12.3%) patients. Follow-up imaging was available in 86 (68.3%) of these patients. At follow-up, a residual stenosis of <30% was found in 15 (17.4%; 95% confidence interval, 10.8–26.9) patients, a 30% to 49% stenosis in 3 (3.5%; 95% confidence interval, 0.8–10.2) patients, a 50% to 69% stenosis in 2 (2.3%; 95% confidence interval, 0.1–8.6) patients, and a ≥70% stenosis in 14 (16.3%; 95% confidence interval, 9.8–25.6) patients. A near or persistent occlusion was present in the remaining 52 (60.5%) patients. Conclusions— A residual high-grade stenosis of the extracranial ICA occurs in 1 of 6 patients with a symptomatic occlusion in the acute stage of cerebral ischemia. Because this may have implications for secondary prevention, we recommend follow-up imaging in these patients within a week after the event. Clinical Trial Registration— URL: http://www.clinicaltrials.gov. Unique identifier: NCT00880113.