3-Dimensional computed tomographic angiography for use of surgery planning in patients with intracranial aneurysms

Discrepancy between MRA and DSA in identifying the shape of small intracranial aneurysms

OBJECTIVE

The authors evaluated the sensitivity and accuracy of MRA in identifying the shape of small-sized unruptured intracranial aneurysms.

METHODS

Small (< 7 mm) unruptured intracranial aneurysms initially detected by MRA and confirmed by DSA between January 2017 and December 2018 were morphologically reviewed by neuroradiologists. Regularity or irregularity of aneurysm shape was analyzed by two independent reviewers using MRA without DSA results. DSA findings served as the reference standard for aneurysm shape. Irregular shape, which in small aneurysms is associated with a higher likelihood of rupture, was defined as positive, and MRA sensitivity, specificity, and accuracy were determined by using evaluations based on location, size, and MRA magnetic strength (1.5T vs 3T MRA). Multivariate analysis was performed to determine risk factors for false-negative MRA results for irregularly shaped aneurysms.

RESULTS

In total, 652 unruptured intracranial aneurysms in 530 patients were reviewed for this study. For detecting aneurysm shape irregularity, the overall MRA sensitivity was 60.4% for reviewer 1 and 60.9% for reviewer 2. Anterior cerebral artery aneurysms had the lowest sensitivity for location (36.7% for reviewer 1, 46.9% for reviewer 2); aneurysms sized < 3 mm had the lowest sensitivity for size (26.7% for both reviewers); and 1.5T MRA had lower sensitivity and accuracy than 3T MRA. In multivariate analysis, location, size, and magnetic strength of MRA were independent risk factors for false-negative MRA results for irregularly shaped aneurysms.

CONCLUSIONS

MRA had a low sensitivity for detecting the irregular shape of small intracranial aneurysms. In particular, anterior cerebral artery location, aneurysm size < 3 mm, and detection with 1.5T MRA were associated with a higher risk of irregularly shaped aneurysms being misjudged as regular.

Circle of Willis variations in migraine patients with ischemic stroke

OBJECTIVES

Migraine is a risk factor for stroke, which might be explained by a higher prevalence in anatomical variants in the circle of Willis (CoW). Here, we compared the presence of CoW variants in patients with stroke with and without migraine.

MATERIALS AND METHODS

Participants were recruited from the prospective Dutch acute Stroke Study. All participants underwent CT angiography on admission. Lifetime migraine history was assessed with a screening questionnaire and confirmed by an interview based on International Classification of Headache Disorders criteria. The CoW was assessed for incompleteness/hypoplasia (any segment <1 mm), for anterior cerebral artery asymmetry (difference > 1/3), and for posterior communicating artery (Pcom) dominance (Pcom-P1 difference > 1/3). Odds ratios with adjustments for age and sex (aOR) were calculated with logistic regression.

RESULTS

We included 646 participants with stroke, of whom 52 had a history of migraine. Of these, 45 (87%) had an incomplete or hypoplastic CoW versus 506 (85%) of the 594 participants without migraine (aOR: 1.47; 95% CI: 0.63-3.44). There were no differences between participants with and without migraine in variations of the anterior or posterior CoW, anterior cerebral artery asymmetry (aOR: 0.86; 95% CI: 0.43-1.74), or Pcom dominance (aOR: 0.64; 95% CI: 0.32-1.30). There were no differences in CoW variations between migraine patients with or without aura.

CONCLUSION

We found no significant difference in the completeness of the CoW in acute stroke patients with migraine compared to those without.

Diagnosis and Treatment of Intracranial Aneurysms with 320-Detector Row Volumetric Computed Tomography Angiography

OBJECTIVES

The objective of the study was to determine the clinical utility of 320-detector row volume-computed tomographic angiography (VCTA) in the management of intracranial aneurysms.

METHODS

Between February 2011 and May 2015, 550 patients successfully underwent 320-detector row VCTA for suspected intracranial aneurysms. Three-dimensional (3D) digital subtraction angiography (DSA) was used as the ultimate reference standard, and the sensitivity, specificity, and accuracy of both nonsubtracted and subtracted VCTA in identifying aneurysms were analyzed.

RESULTS

Nonsubtracted VCTA identified 417 aneurysms (2 false-positive readings, 12 false-negative readings). The diagnostic sensitivity, specificity, and accuracy of non-subtracted VCTA, on a per-aneurysm basis, were 97.2%, 99.0%, and 97.6%, respectively. Subtracted VCTA identified 426 aneurysms (2 false-positive readings, 3 false-negative readings). The sensitivity, specificity, and accuracy of subtracted VCTA, on a per-aneurysm basis, were 99.3%, 99.0%, and 99.2%, respectively. No differences in diagnostic accuracy were found between subtracted VCTA and 3D DSA. Nonsubtracted VCTA, however, was observed to be significantly less sensitive than 3D DSA and subtracted VCTA. Twenty-six aneurysm cases were referred for surgical treatment based on VCTA imaging. All aneurysms were deemed completely occluded during surgical clipping. On the basis of VCTA imaging, 299 aneurysms were found suitable for endovascular coiling, of which 293 aneurysms (98%) were treated successfully.

CONCLUSIONS

The 320-detector row subtracted VCTA technique is an effective, first-line diagnostic imaging modality for surgical and endovascular treatment of aneurysms. The nonsubtracted VCTA was less accurate than the subtracted VCTA, especially for intracranial aneurysms adjoining bone tissue.

Effect of endovascular treatment on headache in elderly patients with unruptured intracranial aneurysms

BACKGROUND AND PURPOSE

The incidence of unruptured intracranial aneurysms is increasing in the elderly population as life expectancy increases, and patients often present with headache. The goal of this study was to determine the effect of endovascular treatment on headache and identify factors associated with headache outcome in elderly patients with unruptured intracranial aneurysms.

MATERIALS AND METHODS

A retrospective study was conducted for elderly patients (≥ 65 years old) being treated for unruptured intracranial aneurysms. Headache assessment was performed by a quantitative 11-point headache scale in all patients before and after endovascular treatment. Factors associated with headache outcome were investigated by univariate analyses.

RESULTS

A total of 72 patients (mean age, 70.0 years; age range, 65-80 years; 41 women) fulfilled the inclusion criteria. There were 52 patients (72.2%) who presented with preoperative headache (headache score ≥ 1). Among them, 40 (76.9%) reported that headache score had an improvement according to their self-reported quantitative headache score after endovascular treatment. The average headache score was 5.63 preoperatively vs 2.50 postoperatively (P = .000). Twenty patients (27.8%) had no headache before treatment (headache score = 0), of whom 2 (10.0%) reported new onset of headache postoperatively. Only a preoperative headache score was associated with treatment outcome of headache, and a higher headache score predicted a lack of headache relief after endovascular treatment (P = .003).

CONCLUSIONS

Endovascular coiling of unruptured intracranial aneurysms resulted in relief of headache in most of the elderly patients. Preoperative headache score was the only statistically significant predictor of headache outcome.

Detection and Characterization of Intracranial Aneurysms with Dual-Energy Subtraction CTA: Comparison with DSA

BACKGROUND

to investigate the diagnostic performance of dual-energy subtraction CTA in evaluating intracranial aneurysms by comparison with DSA.

METHODS

ninety-seven patients with suspected intracranial aneurysms were included into our study and completed both 64-section dual-energy subtraction CTA and DSA examinations. Two independent readers retrospectively reviewed all subtraction CTA images in a blinded manner. Sensitivity, specificity, positive predictive value and negative predictive value of subtraction CTA and DSA were calculated on a per-patient and per-aneurysm basis.

RESULTS

according to the reference standard, 96 aneurysms were present in 81 patients and no aneurysm was found in 16 patients. The overall sensitivity, specificity, positive predictive value and negative predictive value of subtraction CTA on a per-aneurysm basis were 98.9, 100, 100 and 94.1%, respectively. DSA prospectively detected 88 aneurysms in 79 of 81 patients. On a per-aneurysm basis, the sensitivity, specificity, positive predictive value and negative predictive value of DSA were 91.7, 100, 100 and 66.7%, respectively.

CONCLUSION

the diagnostic accuracy of 64-section dual-energy subtraction CTA is promising in detection and characterization of intracranial aneurysms. In most cases, it may substitute for conventional DSA as the primary imaging method in the diagnostic work-up of intracranial aneurysms.

Applications of multislice CT angiography in the surgical clipping and endovascular coiling of intracranial aneurysms

Prompt diagnosis and therapy of aneurysms are critical for patients with nontraumatic subarachnoid hemorrhage (SAH). The aim of our study was to assess the clinical usefulness of multislice computed tomography angiography (CTA) in the surgical and endovascular treatment of intracranial aneurysms. A total of 195 cases with 206 intracranial aneurysms underwent CTA. Fifty (24%) aneurysms underwent surgical clipping while 156 (76%) aneurysms underwent endovascular coiling. In the five missed aneurysms at digital substraction angiography and the nine aneurysms with mass intracerebral hematomas, surgical treatment was successfully performed based on 16-slice CTA alone, and the other 36 aneurysms were clipped on the main basis of the CTA. The intraoperative findings correlated well with the CTA findings and all aneurysms were clipped successfully. Sixteen-slice CTA image information has been shown to determine the choice of aneurysm therapy and assist the surgical and endovascular treatment of intracranial aneurysms.

Postoperative Assessment of Clipped Aneurysms With 64-Slice Computerized Tomography Angiography

BACKGROUND

Multidetector computerized tomography angiography (MDCTA) is now a widely accepted technique for the management of intracranial aneurysms.

OBJECTIVE

To evaluate its accuracy for the postoperative assessment of clipped intracranial aneurysms.

METHODS

We analyzed a consecutive series of 31 patients that underwent direct surgical clipping procedures of 38 aneurysms. A 64 slice MDCT scanner (Aquilion 64, Toshiba) was used and results were compared with digital subtraction angiographies (DSA). Two independent neuroradiologists analyzed the following data: examination quality, artifacts, aneurysm remnant, and patency of collateral branches. Interobserver agreement, sensitivity, and specificity were calculated.

RESULTS

Seventy-nine percent of the aneurysms were located in the anterior circulation. Significant artifacts were found with multiple and cobalt-alloy clips. According to DSA, remnants &gt;2 mm were found in 21% of the cases, and 2 patients had one collateral branch occluded. Sensitivity and specificity of 64-MDCTA for the detection of aneurysm remnants were 50% and 100%, respectively. Sensitivity and specificity of 64-MDCTA for the detection of a significant remnant (&gt;2 mm) and the detection of the occlusion of a collateral branch were, respectively, 67% and 100% and 50% and 100%. No relationship was found with the location, type, shape, size, or number of clips, but missed remnants tended to be larger with cobalt-alloy clips.

CONCLUSIONS

64-MDCTA is a valuable technique to assess the presence of a significant postoperative remnant in single titanium clip application cases and might be useful for long-term follow-up. DSA remains the most accurate postoperative radiological examination.

Utility of computed tomographic angiography in the pre-operative planning for initial and repeat congenital cardiovascular surgery

OBJECTIVE

To investigate the utility of computed tomographic angiography as an adjunctive imaging modality before congenital cardiac surgery.

DESIGN

We evaluated 33 patients who underwent a pre-operative computed tomographic angiogram. They were classified according to the anatomic site of repair. Post-operatively, the surgeon completed a questionnaire assessing the utility of the study.

RESULTS

Computed tomographic angiography was found to be either "essential" or "very useful" for pre-operative planning in 94% of the patients. Specifically, the scan was consistently useful for procedures involving the aorta (14/15, 93%) or the pulmonary veins (4/4, 100%) and obviated pre-operative catheterisations in 14 patients (42%). Furthermore, when compared with other diagnostic groups, computed tomographic angiography determined the need for peripheral cannulation in patients undergoing re-operations (6/7; 86%, p = 0.02).

CONCLUSIONS

Computed tomographic angiography was found to be useful in the pre-operative planning of virtually all patients undergoing repair of congenital cardiac malformations, regardless of diagnosis. Specifically, the studies were essential in select populations, such aortic arch or pulmonary vein repairs, and helped to determine cannulation sites for repeat operations while significantly reducing the need for invasive imaging.

Application of multislice computed tomographic angiography in diagnosis and treatment of intracranial aneurysms

OBJECTIVES

The aim of the study is to assess the clinical value of 16-row multislice computed tomographic angiography (CTA) for detection and treatment of intracranial aneurysms.

PATIENTS AND METHODS

Between January 2005 and October 2008, 388 patients were included and successively underwent 16-slice CTA for suspected intracranial aneurysms. Three neuroradiologists independently reviewed CTA and DSA images. The combined interpretations of digital subtraction angiography (DSA) and surgical findings were considered as the ultimate reference standard against which the diagnostic accuracy of CTA and DSA were compared.

RESULTS

The reference standard revealed 287 aneurysms in 256 patients. There was no statistically significant difference in accuracy between 16-slice CTA and conventional DSA. The sensitivity, specificity, and accuracy of 16-slice CTA in detecting all aneurysms were 98.3, 97.0, and 97.9%, respectively, on a per-aneurysm basis. The sensitivity of 16-slice CTA was 90.0% for reader 1 and 93.3% for reader 2 for less than 3mm aneurysms. One hundred eighty-nine aneurysms were deemed amenable to endovascular therapy on the basis of CTA images, 98% of whom (185) were successfully treated with this method. Forty-eight aneurysms were considered candidates for surgical treatment, and all aneurysms were deemed completely occluded during surgical clipping. Sixteen-slice CTA images provided important preoperative information, which could assist the endovascular and surgical therapy of aneurysms.

CONCLUSIONS

Sixteen-slice CTA is a highly accurate imaging examination of the first line imaging technique for the detection of intracranial aneurysms, and it can provide sufficient diagnostic information in guiding the surgical and endovascular therapy of aneurysms.

Jugular tubercle and vertebral artery/posterior inferior cerebellar artery anatomic relationship: a 3-dimensional angiography computed tomography anthropometric study

OBJECTIVE

To evaluate structural variations of the jugular tubercles (JTs) and their relationships with the vertebral artery, the posterior inferior cerebellar artery (PICA), and the vertebrobasilar junction (VBJ).

METHODS

The depth, height, and width of the JTs were measured using 30 cadaveric basicranial specimens and 50 three-dimensional angiography computed tomographic (angio-CT) scans evaluating morphological variations between the 2 sides. Angio-CT analysis evaluated the relationships of the JTs with the vertebral arteries and the PICAs. The location of the VBJ with respect to the JT level in the coronal plane was evaluated.

RESULTS

In the cadaveric specimens, the mean JT depth ranged from 0.9 to 3.1 cm, the mean height ranged from 0.6 to 1.5 cm, and the mean width ranged from 0.4 to 1.2 cm. According to the 3-dimensional angio-CT scans, JT measurements ranged as follows: depth, 0.7 to 2.6 cm; height, 0.6 to 1.4 cm; and width, 0.3 to 1.2 cm. The vertebral artery was in close contact with the JT on the left side in 30% of cases and on the right side in 24% of the cases. On axial scans, the PICA origin was classified as anterior to the JT in 20.5% of patients on the left side and 17.4% on the right, at the JT level in 50% of patients on the left side and 45.7% on the right, and posterior to the JT in 29.5% of patients on the left side and 36.9% on the right. On coronal scans, the PICA origin was classified as superior to the JT in 13.6% of patients on the left side and 8.7% on the right, at the JT level in 54.6% of patients on the left side and 50% on the right, and inferior to the JT in 31.8% of patients on the left side and 41.3% on the right. In the coronal plane, the VBJ was located above the tubercles in 16 patients (32%), at the JT level in 28 patients (56%), and below the tubercles in 6 patients (12%).

CONCLUSION

A precise morphometric analysis of the JTs on 3-dimensional CT scans was quick and safe and showed significant variations in their size and shape. The relationship of the JT with vertebral artery and the PICA varied significantly, as well as with the VBJ location. Knowledge of these morphological variations can contribute to optimal preoperative surgical planning, minimizing retraction and reducing morbidity during extreme lateral infrajugular-transtubercular exposure surgery.

Remitting Form of Hemicrania Continua: Two New Cases Exhibiting One Unusual Autonomic Feature

Hemicrania continua (HC) is an uncommon, primary headache disorder characterized by a continuous, strictly unilateral headache of moderate intensity with superimposed exacerbations of more severe pain and accompanying autonomic features. Whereas in the majority of HC patients the headache is continuous and without pain-free intervals, we report two new cases of the rare remitting form of HC. One patient described unusual olfactory sensation during episodes of exacerbation, which we classify as an olfactory aura.

BLISTER-LIKE ANEURYSMS OF THE ANTERIOR COMMUNICATING ARTERY

OBJECTIVE

Blood blister-like aneurysms are small hemispherical bulges from the dorsomedial wall of the internal carotid artery that resemble berry aneurysms but differ in their clinical and surgical features. On the basis of our literature review, blister-like aneurysms have been reported to occur only at nonbranching sites of the dorsomedial internal carotid artery. In this report on our series of five patients, we describe blister-like aneurysms of the anterior communicating artery (AComA) and discuss important diagnostic and therapeutic aspects unique to them.

METHODS

In our retrospective review of 719 patients with nontraumatic subarachnoid hemorrhage admitted to our service from 1998 to 2003, 181 (25.17%) patients harbored AComA aneurysms. Five (2.76%) patients (four women, one man) had blister-like aneurysms that were recognized at the time of surgery.

RESULTS

Initial digital subtraction angiography was diagnostic in only one patient. A second digital subtraction angiogram was diagnostic in one patient but failed to reveal an aneurysm in the remaining three patients; these were eventually diagnosed by computed tomographic angiography. All aneurysms were clipped. At the time of surgery, the aneurysms arose from the horizontal portion of the AComA without any involvement of the branches of the anterior cerebral artery. All presented as blister-like aneurysms that were thin-walled and lacking a surgical neck. On dissection, two of the lesions ruptured. All lesions were treated with straight fenestrated clips through the A1–AComA junction, thus remodeling the AComA. No delayed rupture was noted at the time of the last follow-up evaluation. At the time of discharge, outcomes were good in two patients, fair in two, and poor in the remaining patient.

CONCLUSION

Blister-like aneurysms constitute technically challenging lesions that may occur at the AComA. Computed tomographic angiography is valuable in diagnosis. Blister-like aneurysms should be suspected when digital subtraction angiography findings are negative for subarachnoid hemorrhage.

Nonrigid registration for subtraction CT angiography applied to the carotids and cranial arteries

RATIONALE AND OBJECTIVES

Computed tomography angiography (CTA) is an established tool for vascular imaging. However, high-intensity nonvascular structures in the contrast image can seriously hamper luminal visualization. This is an issue for three-dimensional visualization, where high-intensity structures might cover the underlying vasculature. But also in two dimensions, calcified plaques adjacent to the contrast-enhanced vessel lumen impede correct determination of the vessel boundary. High-intensity structures can be eliminated using subtraction CTA, where a native image is subtracted from the contrast image. However, patient and organ motion limits the widespread application of this technique. We propose to use nonrigid image registration to solve this problem.

MATERIALS AND METHODS

For each patient, a native image and a contrast image are recorded, respectively, before and after contrast administration. The native image is registered to the contrast image using an automatic intensity-based nonrigid three-dimensional registration algorithm. Both images are merged in a fused image, allowing the user to switch between a view of the arteries, the bone or both. The procedure has been applied to 95 patients.

RESULTS

In all cases, subtraction CTA using nonrigid registration allows for a significantly better artifacts removal than subtraction CTA without registration. Image quality of all images was judged adequate for clinical use. The average total processing time for each dataset is about 30 minutes.

CONCLUSION

Nonrigid registration can allow for a great reduction in subtraction artifacts for subtraction CTA, resulting in a clear view of the vasculature.

Multislice CT angiography in the selection of patients with ruptured intracranial aneurysms suitable for clipping or coiling

Introduction

We sought to establish whether CT angiography (CTA) can be applied to the planning and performance of clipping or coiling in ruptured intracranial aneurysms without recourse to intraarterial digital subtraction angiography (IA-DSA).

Methods

Over the period April 2003 to January 2006 in all patients presenting with a subarachnoid haemorrhage CTA was performed primarily. If CTA demonstrated an aneurysm, coiling or clipping was undertaken. IA-DSA was limited to patients with negative or inconclusive CTA findings. We compared CTA images with findings at surgery or coiling in patients with positive CTA findings and in patients with negative and inconclusive findings in whom IA-DSA had been performed.

Results

In this study, 224 consecutive patients (mean age 52.7 years, 135 women) were included. In 133 patients (59%) CTA demonstrated an aneurysm, and CTA was followed directly by neurosurgical (n = 55) or endovascular treatment (n = 78). In 31 patients (14%) CTA findings were categorized as inconclusive, and in 60 (27%) CTA findings were negative. One patient received surgical treatment on the basis of false-positive CTA findings. In 17 patients in whom CTA findings were inconclusive, IA-DSA provided further diagnostic information required for correct patient selection for any therapy. Five ruptured aneurysms in patients with a nonperimesencephalic SAH were negative on CTA, and four of these were also false-negative on IA-DSA. On a patient basis the positive predictive value, negative predictive value, sensitivity, specificity and accuracy of CTA for symptomatic aneurysms were 99%, 90%, 96%, 98% and 96%, respectively.

Conclusion

CTA should be used as the first diagnostic modality in the selection of patients for surgical or endovascular treatment of ruptured intracranial aneurysms. If CTA renders inconclusive results, IA-DSA should be performed. With negative CTA results the complementary value of IA-DSA is marginal. IA-DSA is not needed in patients with negative CTA and classic perimesencephalic SAH. Repeat IA-DSA or CTA should still be performed in patients with a nonperimesencephalic SAH.

Improvement of Chronic Headache After Treatment of Unruptured Intracranial Aneurysms

OBJECTIVE

The objective of this study is to determine the incidence, character, and outcome of headache in patients with unruptured intracranial aneurysms who had been treated to avoid the risk of rupture.

BACKGROUND

There are a variety of clinical manifestations associated with unruptured intracranial aneurysms. Among them, chronic headache is the most common presenting and/or accompanying symptom.

METHODS

Among the 137 patients with unruptured aneurysms who had been treated, we collected 81 patients excluding 30 on the basis of inclusion criteria. Twenty-six patients were lost to follow-up. We collected data by medical record review and a telephone survey. Included in the information collected was the analysis of presenting symptom, location and size of each aneurysm, location, quality, intensity and duration of headaches, associated symptoms, triggering and alleviating factors, and precipitating events.

RESULTS

Forty-nine patients (60.5%) of 81 had chronic headaches before the diagnosis of unruptured intracranial aneurysm. Forty-four patients (89.8%) answered that their headaches were improved slightly (12 patients) or markedly (32 patients) (P <.05). The clinical pattern of the headache worsened in only 1 patient and did not change in 4 patients. When the surgical group (40 patients) and the coil embolization group (41 patients) were compared, there was no significant difference observed in outcome (P >.05).

CONCLUSION

Either by employing the technique of clipping or by coil embolization, treatment of unruptured intracranial aneurysms resulted in relief of headaches in majority of patients who had headaches pre-operatively.

Acute subarachnoid hemorrhage: using 64-slice multidetector CT angiography to “triage” patients’ treatment

INTRODUCTION

To evaluate the clinical role of CT angiography (CTA) in patients with acute subarachnoid hemorrhage (SAH) for treatment decision-making.

METHODS

Consecutive patients with acute SAH had CTA using a 64-slice scanner for initial clinical decision-making. Image processing included multiplanar volume reformatted (MPVR) maximum intensity projections (MIP) and 3D volume-rendered reconstructions. CTAs were used for (1) evaluating the cause of SAH, and (2) triaging aneurysm-bearing patients to the more appropriate management, either surgical clipping or endovascular coiling. CTA findings were confirmed by neurosurgical exploration or catheter angiography (digital subtraction angiography, DSA). Successful coiling provided evidence that triaging to endovascular treatment was correct.

RESULTS

Included in the study were 73 patients. CTA findings were confirmed by DSA or neurosurgical operation in 65 patients, and of these 65, 47 had aneurysmal SAH, 3 had vasculitis, 1 had arterial dissection and 14 had no underlying arterial abnormality. The cause of SAH was detected with CTA in 62 out of the 65 patients (95.4%, sensitivity 94%, specificity 100%). CTA revealed the aneurysm in 46 of 47 patients (98%, sensitivity 98%, specificity 100%, positive predictive value 100%, negative predictive value 82.3%), 1 of 3 vasculitides and 1 of 1 dissection. Of the 46 patients with aneurysm, 44 (95.7%) were referred for treatment based on CTA. In 2 patients (2 of 46, 4.4%) CTA was not informative enough to choose treatment requiring DSA. Of the 44 patients, 27 (61.4%) were referred to endovascular treatment and successful coiling was achieved in 25 (25 of 27, 92.6%).

CONCLUSION

CTA using a 64-slice scanner is an accurate tool for detecting and characterizing aneurysms in acute SAH. CTA is useful in the decision process whether to coil or clip an aneurysm.