The use of 4D-CTA in the diagnostic work-up of brain arteriovenous malformations

Republished: Novel use of 4D-CTA in imaging of intranidal aneurysms in an acutely ruptured arteriovenous malformation: is this the way forward?

Ruptured arteriovenous malformation (AVM) is a frequent cause of intracranial hemorrhage. The presence of associated aneurysms, especially intranidal aneurysms, is considered to increase the risk of re-hemorrhage. We present two cases where an intranidal aneurysm was demonstrated on four-dimensional CT angiography (time-resolved CT angiography) (4D-CTA). These features were confirmed by digital subtraction angiography (catheter arterial angiogram). This is the first report of an intranidal aneurysm demonstrated by 4D-CTA. 4D-CTA can offer a comprehensive evaluation of the angioarchitecture and flow dynamics of an AVM for appropriate classification and management.

Novel use of 4D-CTA in imaging of intranidal aneurysms in an acutely ruptured arteriovenous malformation: is this the way forward?

Ruptured arteriovenous malformation (AVM) is a frequent cause of intracranial hemorrhage. The presence of associated aneurysms, especially intranidal aneurysms, is considered to increase the risk of re-hemorrhage. We present two cases where an intranidal aneurysm was demonstrated on four-dimensional CT angiography (time-resolved CT angiography) (4D-CTA). These features were confirmed by digital subtraction angiography (catheter arterial angiogram). This is the first report of an intranidal aneurysm demonstrated by 4D-CTA. 4D-CTA can offer a comprehensive evaluation of the angioarchitecture and flow dynamics of an AVM for appropriate classification and management.

Dynamic CT angiography for cyberknife radiosurgery planning of intracranial arteriovenous malformations: a technical/feasibility report

Background.

Successful radiosurgery for arteriovenous malformations (AVMs) requires accurate nidus delineation in the 3D treatment planning system (TPS). The catheter biplane digital subtraction angiogram (DSA) has traditionally been the gold standard for evaluation of the AVM nidus, but its 2D nature limits its value for contouring and it cannot be imported into the Cyberknife TPS. We describe a technique for acquisition and integration of 3D dynamic CT angiograms (dCTA) into the Cyberknife TPS for intracranial AVMs and review the feasibility of using this technique in the first patient cohort.

Patients and methods.

Dynamic continuous whole brain CT images were acquired in a Toshiba 320 volume CT scanner with data reconstruction every 0.5 sec. This multi-time-point acquisition enabled us to choose the CT data-set with the clearest nidus without significant enhancement of surrounding blood vessels. This was imported to the Cyberknife TPS and co-registered with planning CT and T2 MRI (2D DSA adjacent for reference). The feasibility of using dCTA was evaluated in the first thirteen patients with outcome evaluation from patient records.

Results.

dCTA data was accurately co-registered in the Cyberknife TPS and appeared to assist in nidus contouring for all patients. Imaging modalities were complementary. 85% of patients had complete (6/13) or continuing partial nidus obliteration (5/13) at 37 months median follow-up.

Conclusions.

dCTA is a promising imaging technique that can be successfully imported into the Cyberknife TPS and appears to assist in radiosurgery nidus definition. Further study to validate its role is warranted.

Flow diversion in the treatment of carotid injury and carotid-cavernous fistula after transsphenoidal surgery

We describe a case of iatrogenic carotid injury with secondary carotid-cavernous fistula (CCF) treated with a silk flow diverter stent placed within the injured internal carotid artery and coils placed within the cavernous sinus. Flow diverters may offer a simple and potentially safe vessel-sparing option in this rare complication of transsphenoidal surgery. The management options are discussed and the relevant literature is reviewed.

Four-dimensional computed tomography angiographic evaluation of cranial dural arteriovenous fistula before and after embolization

PURPOSE

This study aimed to evaluate the usefulness of four-dimensional CTA before and after embolization treatment with ONYX-18 in eleven patients with cranial dural arteriovenous fistulas, and to compare the results with those of the reference standard DSA.

PATIENTS AND METHODS

Eleven patients with cranial dural arteriovenous fistulas detected on DSA underwent transarterial embolization with ONYX-18. Four-dimensional CTA was performed an average of 2 days before and 4 days after DSA. Four-dimensional CTA and DSA images were reviewed by two neuroradiologists for identification of feeding arteries and drainage veins and for determining treatment effects. Interobserver and intermodality agreement between four-dimensional CTA and DSA were assessed.

RESULTS

Forty-two feeding arteries were identified for 14 fistulas in the 11 patients. Of these, 36 (85.71%) were detected on four-dimensional CTA. After transarterial embolization, one patient got partly embolized, and the fistulas in the remaining 10 patients were completely occluded. The interobserver agreement for four-dimensional CTA and intermodality agreement between four-dimensional CTA and DSA were excellent (κ=1) for shunt location, identification of drainage veins, and fistula occlusion after treatment.

CONCLUSION

Four-dimensional CTA images are highly accurate when compared with DSA images both before and after transarterial embolization treatment. Four-dimensional CTA can be used for diagnosis as well as follow-up of cranial dural arteriovenous fistulas in clinical settings.

Surgical treatment for ruptured dural arteriovenous fistula with large intracranial hematoma

The rupture of dural arteriovenous fistula (DAVF) is a serious complication endangering the lives of patients. It is difficult to treat such ruptured DAVF with large intracranial hematoma since lacking of early diagnostic methods. Meanwhile, there was no consensus of how to surgically treat these patients in early stage. In this study, we tried to use 4D-CTA to diagnose DAVF and guide surgical treatment. Based on the result of 4D-CTA, we attempted to eliminate DAVF at the same time we removed hematoma. The result was encouraging. 7 patients with ruptured DAVF presented as large spontaneous intracranial hemorrhage were included in this research between May, 2010 and August, 2012 in our hospital. 4D-CTA was performed in all cases. All results of 4D-CTA inspections were studied by both neurosurgeon and neuroradiologist. The therapeutic options were evaluated based on the clinical and angiographic results. All fistulas of seven patients were eliminated at the same time the hematoma being evacuated. 4D-CTA was sufficient for detecting and recognizing basic vessel angioarchitecture of DAVF to guide surgical treatment. Main arterial supplies, fistula location and CVDs found during surgery are consistent with the results 4D-CTA. All seven cases achieved completely fistula occlusion in operation without new neurological complication. We favor one stage surgical treatment for ruptured DAVF with large intracranial hemorrhage. 4D-CTA plays an important role in preoperative emergent inspection for its safety, rapidity and accuracy. However, it still needs further and larger investigations to optimize such treatment methods and to find out other potential risks.

320-Row Detector Dynamic 4D-CTA for the Assessment of Brain and Spinal Cord Vascular Shunting Malformations. A Technical Note

Shunting vascular malformations of the brain and spinal cord are traditionally studied using digital subtraction angiography (DSA), the current gold standard imaging method routinely used because of its favourable combination in terms of spatial and temporal resolution. Because DSA is relatively expensive, time-consuming and carries a risk of silent embolic events and a small risk of transient or permanent neurologic deterioration, a non-invasive alternative angiographic method is of interest. New 320 row-detector CT scanners allow volumetric imaging of the whole brain with temporal resolution up to ≌ 3 Hz. Those characteristics make computed tomography angiography (CTA) an affordable imaging method to study the haemodynamics of the whole brain and can also be applied to the study of limited portions of the spinal cord. The aim of this paper is to make a brief summary of our experience in studying shunting vascular malformation of the brain and spinal cord using dynamic 4D-CTA, explaining the technical details of the studies performed at our institution, and the state-of-the-art major advantages and drawbacks of this new technique. We found that dynamic 4D-CTA is able to depict the main architectural characteristics of previously untreated vascular shunting malformations both in brain and spinal cord (i.e. their main arterial feeders and draining veins) allowing their correct diagnosis and exhaustive classification, limiting the use of DSA for therapeutic purposes.

Clot Burden and Collaterals in Anterior Circulation Stroke: Differences Between Single-Phase CTA and Multi-phase 4D-CTA

PURPOSE

It has been reported that the extent of intravascular thrombi and the quality of collateral filling in computed tomography (CT) angiography are predictive for the clinical outcome in patients with acute stroke. We hypothesized that multi-phase four-dimensional CTA (4D-CTA) allows better assessment of clot burden and collateral flow compared with arterial single-phase CTA (CTA).

METHODS

In 49 patients (33 female; age: 77 ± 12 years) with acute anterior circulation stroke, CTA and 4D-CTA reconstructed from dynamic perfusion CT data were analyzed for absolute thrombus length (TL), clot burden score (CBS), and collateral score (CS). The length of the filling defect was also defined on thin-slice nonenhanced CT as corresponding hyperdense middle cerebral artery sign (HMCAS) when present.

RESULTS

There was good correlation (r = 0.62, p < 0.01) between the length of HMCAS (1.29 ± 0.62 cm) and TL in 4D-CTA (1.22 ± 0.51 cm). 4D-CTA and CTA significantly varied (p < 0.01) in TL (1.42 ± 0.73 cm (CTA) versus 1.11 ± 0.62 cm (4D-CTA)), CBS (median: 5, interquartile range: 4-7 (CTA) versus median: 6, interquartile range: 5-8 (4D-CTA); p < 0.001), and CS (median: 2, interquartile range: 1-2 (CTA) versus median: 3, interquartile range: 2-3 (4D-CTA); p < 0.001). Accordingly, CTA significantly overrated clot burden and underestimated collateral flow.

CONCLUSIONS

4D-CTA more closely defines clot burden and collateral supply in anterior circulation stroke than CTA, implicating an additional diagnostic benefit.

4D-CTA in neurovascular disease: a review

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.

Computed tomography angiography or magnetic resonance angiography for detection of intracranial vascular malformations in patients with intracerebral haemorrhage

BACKGROUND

Intracranial vascular malformations (brain or pial/dural arteriovenous malformations/fistulae, and aneurysms) are the leading cause of intracerebral haemorrhage (ICH) in young adults. Early identification of the intracranial vascular malformation may improve outcome if treatment can prevent ICH recurrence. Catheter intra-arterial digital subtraction angiography (IADSA) is considered the reference standard for the detection an intracranial vascular malformation as the cause of ICH. Computed tomography angiography (CTA) and magnetic resonance angiography (MRA) are less invasive than IADSA and may be as accurate for identifying some causes of ICH.

OBJECTIVES

To evaluate the diagnostic test accuracy of CTA and MRA versus IADSA for the detection of intracranial vascular malformations as a cause of ICH.

SEARCH METHODS

We searched MEDLINE (1948 to August 2013), EMBASE (1980 to August 2013), MEDION (August 2013), the Database of Abstracts of Reviews of Effects (DARE; August 2013), the Health Technology Assessment Database (HTA; August 2013), ClinicalTrials.gov (August 2013), and WHO ICTRP (International Clinical Trials Register Portfolio; August 2013). We also performed a cited reference search for forward tracking of relevant articles on Google Scholar (http://scholar.google.com/), screened bibliographies, and contacted authors to identify additional studies.

SELECTION CRITERIA

We selected studies reporting data that could be used to construct contingency tables that compared CTA or MRA, or both, with IADSA in the same patients for the detection of intracranial vascular malformations following ICH.

DATA COLLECTION AND ANALYSIS

Two authors (CBJ and RA-SS) independently extracted data on study characteristics and measures of test accuracy. Two authors (CBJ and PMW) independently extracted data on test characteristics. We obtained data restricted to the subgroup undergoing IADSA in studies using multiple reference standards. We combined data using the bivariate model. We generated forest plots of the sensitivity and specificity of CTA and MRA and created a summary receiver operating characteristic plot.

MAIN RESULTS

Eleven studies (n = 927 participants) met our inclusion criteria. Eight studies compared CTA with IADSA (n = 526) and three studies compared MRA with IADSA (n = 401). Methodological quality varied considerably among studies, with partial verification bias in 7/11 (64%) and retrospective designs in 5/10 (50%). In studies of CTA, the pooled estimate of sensitivity was 0.95 (95% confidence interval (CI) 0.90 to 0.97) and specificity was 0.99 (95% CI 0.95 to 1.00). The results remained robust in a sensitivity analysis in which only studies evaluating adult patients (≥ 16 years of age) were included. In studies of MRA, the pooled estimate of sensitivity was 0.98 (95% CI 0.80 to 1.00) and specificity was 0.99 (95% CI 0.97 to 1.00). An indirect comparison of CTA and MRA using a bivariate model incorporating test type as one of the parameters failed to reveal a statistically significant difference in sensitivity or specificity between the two imaging modalities (P value = 0.6).

AUTHORS' CONCLUSIONS

CTA and MRA appear to have good sensitivity and specificity following ICH for the detection of intracranial vascular malformations, although several of the included studies had methodological shortcomings (retrospective designs and partial verification bias in particular) that may have increased apparent test accuracy.

Computed tomography depiction of small pediatric vessels with model-based iterative reconstruction

BACKGROUND

Computed tomography (CT) is extremely important in characterizing blood vessel anatomy and vascular lesions in children. Recent advances in CT reconstruction technology hold promise for improved image quality and also reductions in radiation dose. This report evaluates potential improvements in image quality for the depiction of small pediatric vessels with model-based iterative reconstruction (Veo™), a technique developed to improve image quality and reduce noise.

OBJECTIVE

To evaluate Veo™ as an improved method when compared to adaptive statistical iterative reconstruction (ASIR™) for the depiction of small vessels on pediatric CT.

MATERIALS AND METHODS

Seventeen patients (mean age: 3.4 years, range: 2 days to 10.0 years; 6 girls, 11 boys) underwent contrast-enhanced CT examinations of the chest and abdomen in this HIPAA compliant and institutional review board approved study. Raw data were reconstructed into separate image datasets using Veo™ and ASIR™ algorithms (GE Medical Systems, Milwaukee, WI). Four blinded radiologists subjectively evaluated image quality. The pulmonary, hepatic, splenic and renal arteries were evaluated for the length and number of branches depicted. Datasets were compared with parametric and non-parametric statistical tests.

RESULTS

Readers stated a preference for Veo™ over ASIR™ images when subjectively evaluating image quality criteria for vessel definition, image noise and resolution of small anatomical structures. The mean image noise in the aorta and fat was significantly less for Veo™ vs. ASIR™ reconstructed images. Quantitative measurements of mean vessel lengths and number of branches vessels delineated were significantly different for Veo™ and ASIR™ images. Veo™ consistently showed more of the vessel anatomy: longer vessel length and more branching vessels.

CONCLUSION

When compared to the more established adaptive statistical iterative reconstruction algorithm, model-based iterative reconstruction appears to produce superior images for depiction of small pediatric vessels on computed tomography.

Long-term outcome of 106 consecutive pediatric ruptured brain arteriovenous malformations after combined treatment

BACKGROUND AND PURPOSE

Childhood intracerebral hemorrhage is mainly attributable to underlying brain arteriovenous malformations (bAVMs). Multimodal treatment options for bAVMs include microsurgery and embolization, allowing an immediate cure, and radiosurgery, entailing longer obliteration times. Follow-up data on pediatric ruptured bAVMs are scarce, making it difficult to assess the risk of subsequent intracerebral hemorrhage. Our aim was to assess the clinical and angiographic outcome and to analyze risk factors for rebleeding during and after combined treatment of pediatric bAVMs.

METHODS

A prospectively maintained database of children referred to our institution between January 1997 and October 2012 for bAVMs was retrospectively queried to identify all consecutive ruptured bAVMs treated by surgery, embolization, and radiosurgery. The impact of baseline clinical and bAVM characteristics on clinical outcome, rebleeding rate, annual bleeding rate, and bAVM obliteration was studied using univariate and multivariate Cox regression analysis.

RESULTS

One hundred six children with ruptured bAVMs were followed up for a total of 480.5 patient-years (mean, 4.5 years). Thirteen rebleeding events occurred, corresponding to an annual bleeding rate of 2.71±1.32%, significantly higher in the first year (3.88±1.39%) than thereafter (2.22±1.38%; P<0.001) and in the case of associated aneurysms (relative risk, 2.68; P=0.004) or any deep venous drainage (relative risk, 2.97; P=0.002), in univariate and multivariate analysis. Partial embolization was associated with a higher annual bleeding rate, whereas initial surgery for intracerebral hemorrhage evacuation was associated with a lower risk of rebleeding.

CONCLUSIONS

Associated aneurysms and any deep venous drainage are independent risk factors for rebleeding in pediatric ruptured bAVMs. Immediate surgery or total embolization might be advantageous for children harboring such characteristics, whereas radiosurgery might be targeted at patients without such characteristics.

"Imaging Evaluation of Collaterals in the Brain: Physiology and Clinical Translation"

The cerebral collateral circulation is a network of blood vessels designed to preserve cerebral blood flow when primary routes fail. Though recognized for hundreds of years, the beneficial influence of collateral flow has now gained significant attention due to widely available, rapid, and real-time non-invasive imaging techniques. Multimodal CT and MRI based techniques, with angiographic and perfusion assessments, are becoming mainstays in the care of patients with ischemic brain disease. These methods allow for precise delineation of the structural and functional aspects of cerebral blood flow and as such provide valuable information that can inform the diagnosis and treatment of cerebral ischemia, in both the acute and chronic setting.

Time-resolved computed tomography of the liver: retrospective, multi-phase image reconstruction derived from volumetric perfusion imaging

OBJECTIVE

To assess feasibility and image quality (IQ) of a new post-processing algorithm for retrospective extraction of an optimised multi-phase CT (time-resolved CT) of the liver from volumetric perfusion imaging.

METHODS

Sixteen patients underwent clinically indicated perfusion CT using 4D spiral mode of dual-source 128-slice CT. Three image sets were reconstructed: motion-corrected and noise-reduced (MCNR) images derived from 4D raw data; maximum and average intensity projections (time MIP/AVG) of the arterial/portal/portal-venous phases and all phases (total MIP/ AVG) derived from retrospective fusion of dedicated MCNR split series. Two readers assessed the IQ, detection rate and evaluation time; one reader assessed image noise and lesion-to-liver contrast.

RESULTS

Time-resolved CT was feasible in all patients. Each post-processing step yielded a significant reduction of image noise and evaluation time, maintaining lesion-to-liver contrast. Time MIPs/AVGs showed the highest overall IQ without relevant motion artefacts and best depiction of arterial and portal/portal-venous phases respectively. Time MIPs demonstrated a significantly higher detection rate for arterialised liver lesions than total MIPs/AVGs and the raw data series.

CONCLUSION

Time-resolved CT allows data from volumetric perfusion imaging to be condensed into an optimised multi-phase liver CT, yielding a superior IQ and higher detection rate for arterialised liver lesions than the raw data series.

KEY POINTS

• Four-dimensional computed tomography is limited by motion artefacts and poor image quality. • Time-resolved-CT facilitates 4D-CT data visualisation, segmentation and analysis by condensing raw data. • Time-resolved CT demonstrates better image quality than raw data images. • Time-resolved CT improves detection of arterialised liver lesions in cirrhotic patients.

Usefulness of 4D-CTA in the detection of cerebral dural sinus occlusion or stenosis with collateral pathways

In time-resolved CT angiography (4D-CTA), it is of substantial merit to detect the veins and sinuses of the whole brain with the simultaneous demonstration of the natural drainage flow in order to find occlusion or stenosis of the dural sinuses with collateral pathways. As preoperative information for patients with brain tumors, it is important to detect feeding arteries, incidentally found aneurysms or other vascular lesions, and to detect patency of the dural sinuses and the important cortical veins, whether they are compressed by tumors or not. On the other hand, cerebral venous thrombosis (CVT) may occur in patients due to various causes, which has not been unusual in recent years. For patients with acute symptomatic or chronic non-symptomatic CVT, identification of dural sinus occlusion (DSO) or dural sinus stenosis (DSS) and compensatory collateral pathways is necessary for suitable thrombolytic therapy or careful investigation to avoid further CVT. This study reviews our experiences in 116 cases of 4D-CTA for 90 patients with brain tumors and 26 other patients including 11 with arteriovenous malformation, and four with acute CVT and other conditions. 4D-CTA presented DSO/DSS with compensatory venous collateral pathways, which was helpful to detect the severity of the venous abnormality, and see whether it was compressed by brain tumors, or due to other causes in patients with symptomatic or non-symptomatic CVT. 4D-CTA is a useful non-invasive diagnostic tool to detect cerebral venous abnormalities as an alternative to DSA.

Usefulness of 320-row area detector computed tomography for the diagnosis of cystic falx meningioma

We present a case of cystic falx meningioma. Cystic meningioma is rare and not easy to diagnose preoperatively; it is often misdiagnosed as other tumors, including glial or metastatic tumors with cystic or necrotic changes. This study showed the potential impact of 320-row computed tomography (CT) on image-based diagnostic evaluation of cystic meningioma with special attention to the novel techniques of 4-dimensional CT angiography (4D-CTA) and CT whole-brain perfusion (CTP). 4D-CTA showed the arterial supply feeding the tumor and late enhancement of the tumor nodule, similar to that seen in meningioma by conventional angiography. CTP showed that the tumor had a higher cerebral blood flow and cerebral blood volume and a longer mean transit time than adjacent brain tissue. These findings were consistent with meningioma and reinforced the other imaging findings, resulting in the correct preoperative diagnosis. The new techniques available for 320-row CT can potentially be used to improve differential diagnosis and preoperative assessment of cystic tumors with nodules.

The diagnosis of arteriovenous malformations by 4D-CTA: a clinical study

BACKGROUND AND PURPOSE

Digital subtraction angiography (DSA) is the current imaging 'gold standard' for diagnosis of arteriovenous malformation (AVM). The latest technique, four-dimensional computed tomography (4D-CT), offers a new diagnostic method for assessing AVM in real time. This study used a 320-detector-row CT scanner to compare the value of 4D-CT angiography (4D-CTA) with DSA in the diagnosis of untreated AVM patients.

METHODS

Seventeen patients diagnosed with AVM by DSA were included in this study. Two independent readers blind to the results of all examinations evaluated the findings of DSA and 4D-CTA in each patient. All results were then documented using a standardized scoring sheet.

RESULTS

The results of 4D-CTA in all 17 cases were fully consistent with DSA for AVM location, size and vascular structures. 4D-CTA had the same ability as DSA to distinguish the main feeding arteries in all cases, although in the identification of smaller and specific arterial branches, there were discrepancies in one patient between the two methods. In the diagnosis of draining veins, however, 4D-CTA successfully displayed all of the vessels found by DSA.

CONCLUSION

4D-CTA was able to detect all AVM lesions, including their size, location, feeding arteries and draining veins. Thus, 4D-CTA has a value similar to that of DSA in the diagnosis and assessment of AVM.

Optimization of the reconstruction interval in neurovascular 4D-CTA imaging. A technical note

Time resolved whole brain CT angiography (4D-CTA) is a novel imaging technology providing information regarding blood flow. One of the factors that influence the diagnostic value of this examination is the temporal resolution, which is affected by the gantry rotation speed during acquisition and the reconstruction interval during post-processing. Post-processing determines the time spacing between two reconstructed volumes and, unlike rotation speed, does not affect radiation burden. The data sets of six patients who underwent a cranial 4D-CTA were used for this study. Raw data was acquired using a 320-slice scanner with a rotation speed of 2 Hz. The arterial to venous passage of an intravenous contrast bolus was captured during a 15 s continuous scan. The raw data was reconstructed using four different reconstruction-intervals: 0.2, 0.3, 0.5 and 1.0 s. The results were rated by two observers using a standardized score sheet. The appearance of each lesion was rated correctly in all readings. Scoring for quality of temporal resolution revealed a stepwise improvement from the 1.0 s interval to the 0.3 s interval, while no discernable improvement was noted between the 0.3 s and 0.2 s interval. An increase in temporal resolution may improve the diagnostic quality of cranial 4D-CTA. Using a rotation speed of 0.5 s, the optimal reconstruction interval appears to be 0.3 s, beyond which, changes can no longer be discerned.

320-detector row CT angiography for detection and evaluation of intracranial aneurysms: comparison with conventional digital subtraction angiography

AIM

To compare the diagnostic performance of 320-detector row computed tomographic angiography (CTA) with digital subtraction angiography (DSA) for the detection and characterization of intracranial aneurysms.

MATERIALS AND METHODS

Fifty-two consecutive patients with non-traumatic subarachnoid haemorrhage (SAH) and suspected intracranial aneurysms were evaluated from January 2009 to October 2011. All underwent both 320-detector row volume CTA examination and DSA. CTA volume data were transmitted to a VITREA workstation and two physicians with experience in diagnostic imaging of the nervous system independently carried out image post-processing and assessed the results. The three-dimensional (3D) CTA and DSA images were assessed using intraoperative findings as the reference standard.

RESULTS

In 52 patients, 54 aneurysms were detected; 48 patients underwent surgery for 50 aneurysms. The overall sensitivity, specificity, and accuracy of 3D CTA were 96.3, 100, and 94.6%, respectively. Meanwhile, the overall sensitivity, specificity, and accuracy of DSA were 98.1, 98.1, and 95.1%, respectively. For aneurysms less than 3 mm, the sensitivity, specificity, and accuracy of 3D CTA were 81.8, 100, and 93.3%, respectively. The sensitivity, specificity, and accuracy of DSA for small aneurysms were 90.9, 100, and 96.2%, respectively. 3D CTA was superior to DSA in demonstrating aneurysmal calcification, parent artery, and surrounding vascular anatomy.

CONCLUSIONS

3D CTA is a highly sensitive, specific, and non-invasive imaging method for diagnosis and evaluation of intracranial aneurysms. It also allows for precise depiction of aneurysm morphology. Therefore, 320-detector row CTA may be used as an alternative to DSA as a first-line imaging technique in patients with SAH.

Classification of cerebral arteriovenous malformations and intranidal flow patterns by color-encoded 4D-hybrid-MRA

BACKGROUND AND PURPOSE

4D MRA has been evolving as a noninvasive supplement for DSA. The purpose of this study was to evaluate the feasibility of a newly developed blood flow visualization technique for the classification of cerebral AVMs. We hypothesized that 4D-hMRA allows detection of different flow patterns within the nidus as well as differentiation of feeders and draining veins and has very good agreement with DSA regarding the Spetzler-Martin grade.

MATERIALS AND METHODS

Thirty-one consecutive patients with AVMs were evaluated by using 4D-hMRA and DSA by 2 blinded raters. Rating criteria included Spetzler-Martin score and other morphologic variables together with a new scale for 3 intranidal flow patterns (homogeneous = 1, unidirectional = 2, heterogeneous = 3).

RESULTS

The Spetzler-Martin grades were rated different from DSA in 5 cases by rater 1 and in 3 cases by rater 2 with an excellent interrater reliability of κ = 0.96 (4/31, 1 by size and 3 by drainage). Each reader missed 5 feeders on 4D-hMRA. Draining veins were distinguished in the temporal course in 7 on DSA but in 8 and 12 on 4D-hybrid-MRA (raters 1 and 2 respectively), with κ = 0.79. A type 1 intranidal flow pattern was recognizable in 9 (30%) patients; type 2, in 19 (60%); and type 3, in 3 (10%).

CONCLUSIONS

4D-hMRA allows reliable Spetzler-Martin grading and detection of brain arteriovenous malformation feeding arteries and draining veins, with the drawback that for small vessels DSA is still needed. Draining veins might even be detected with higher sensitivity than on DSA. Discrimination of different intranidal flow patterns is possible, but their relevance for hemorrhage risk assessment and therapy planning requires further study.