Postoperative three-dimensional CT angiography after cerebral aneurysm clipping with titanium clips: detection with single detector CT. Comparison with intra-arterial digital subtraction angiography

Efficacy of ultra-high-resolution computed tomographic angiography for postoperative evaluation of intracranial aneurysm after clipping surgery: A case report

Background:

Following clipping surgery for intracranial aneurysm, computed tomography angiography (CTA) is often used to confirm complete aneurysm obliteration. However, artifacts from the titanium clips usually degrade the images around them. The ultra-high-resolution computed tomography (UHR-CT) system recently became available in clinical practice. Here, we report a case in which CTA using the UHR-CT system successfully pointed out a small aneurysmal remnant after the clipping surgery, which was validated by digital subtraction angiography.

Case Description:

A patient underwent clipping surgery for an unruptured aneurysm using two titanium alloy clips. CTA using the UHR-CT system demonstrated a small remnant aneurysm. Digital subtraction angiography confirmed the minor remnant. The UHR-CTA images were comparable to three-dimensional reconstructed images from the rotational angiography.

Conclusion:

We propose that UHR-CTA is a reliable postoperative assessment method for intracranial clipping surgeries.

256-row multislice CT angiography in the postoperative evaluation of cerebral aneurysms treated with titanium clips: using three-dimensional rotational angiography as the standard of reference

OBJECTIVE

To assess the diagnostic accuracy of 256-row multislice computed tomographic angiography (CTA) compared with three-dimensional rotational angiography (3DRA) in the postoperative evaluation of cerebral aneurysms treated with titanium clips.

METHODS

A total of 128 patients (42 men, 86 women; mean age, 57.6 years) with 143 cerebral aneurysms treated using titanium clips underwent both CTA and 3DRA. Two reviewers retrospectively evaluated the following parameters on CTA and 3DRA: (1) residual/recurrent aneurysm (absent or present), (2) patency of parent artery (patent or occluded/severe stenotic (> 70%)), and (3) patency of adjacent branch (patent or occluded/absent).

RESULTS

A total of 24 residual/recurrent aneurysms were detected by 3DRA. The sensitivity, specificity, and accuracy of CTA for the detection of residual/recurrent aneurysms were 83.3%, 100%, and 97.2% for reviewer 1 and 79.2%, 100%, and 96.5% for reviewer 2, respectively. The sensitivity, specificity, and accuracy of CTA for the evaluation of patency of parent artery were 100%, 100%, and 100%, respectively, for both reviewers. The sensitivity, specificity, and accuracy of CTA for evaluation of the patency of adjacent branch were 85.1%, 100%, and 92.3% for reviewer 1 and 82.4%, 100%, and 90.9% for reviewer 2, respectively.

CONCLUSION

A 256-row multislice CTA is a valuable non-invasive tool for assessment of cerebral aneurysms treated with titanium clips.

KEY POINTS

• A 256-row multislice CTA is an accurate imaging technique for the postoperative assessment of cerebral aneurysms treated with titanium clips. • Sensitivity of CTA for the detection of residual/recurrent aneurysms was 79-83% compared with 3DRA. • CTA is still limited in detecting residual/recurrent aneurysms of < 2 mm and small adjacent branches.

Residual Cerebral Aneurysms After Microsurgical Clipping: A New Scale, an Agreement Study, and a Systematic Review of the Literature

OBJECTIVE

The surgical repair of a cerebral aneurysm does not always lead to complete occlusion. A standardized repeatable method of reporting results of surgical clipping is desirable. Our purpose was to systematically review methods of classifying aneurysm remnants, provide a new scale with precise definitions of categories, and perform an agreement study to assess the variability in adjudicating remnants after aneurysm clipping.

METHODS

A systematic review was performed to identify ways to report angiographic results of surgical clipping between 1963 and 2017. Postclipping angiographic results of 43 patients were also independently evaluated by 10 raters of various experience and backgrounds using a new 4-category scale. Agreement between responses were analyzed using κ statistics.

RESULTS

The systematic review yielded 63 articles with 37 different nomenclatures using 2-6 categories. The reliability of judging the presence of an aneurysm remnant on catheter angiography was studied only twice, with only 2 raters each time, with contradictory results. Interobserver agreement using the new 4-category scale was moderate (κ = 0.52; 95% confidence interval, 0.43-0.62) for all observers, but improved to substantial (κ = 0.62; 95% confidence interval, 0.47-0.76) when results were dichotomized (grade 0/1 vs. 2/3).

CONCLUSIONS

Various classification schemes to evaluate angiographic results after surgical clipping exist in the literature, but they lack standardization. Adjudication using fewer, better defined categories may yield more reliable agreement.

Efficacy of Endoscopic Fluorescein Video Angiography in Aneurysm Surgery—Novel and Innovative Assessment of Vascular Blood Flow in the Dead Angles of the Microscope

BACKGROUND: In aneurysm surgery, assessment of the blood flow around the aneurysm is crucial. Recently, intraoperative fluorescence video angiography has been widely adopted for this purpose. However, the observation field of this procedure is limited to the microscopic view, and it is difficult to visualize blood flow obscured by the skull base anatomy, parent arteries, and aneurysm.

OBJECTIVE: To demonstrate the efficacy of a new small-caliber endoscopic fluorescence video angiography system employing sodium fluorescein in aneurysm surgery for the first time.

METHODS: Eighteen patients with 18 cerebral aneurysms were enrolled in this study. Both microscopic fluorescence angiography and endoscopic fluorescein video angiography were performed before and after clip placement.

RESULTS: Endoscopic fluorescein video angiography provided bright fluorescence imaging even with a 2.7-mm-diameter endoscope and clearly revealed blood flow within the vessels in the dead angle areas of the microscope in all 18 aneurysms. Consequently, it revealed information about aneurysmal occlusion and perforator patency in 15 aneurysms (83.3%) that was not obtainable with microscopic fluorescence video angiography. Furthermore, only endoscopic video angiography detected the incomplete clipping in 2 aneurysms and the occlusion of the perforating branches in 3 aneurysms, which led to the reapplication of clips in 2 aneurysms.

CONCLUSION: The innovative endoscopic fluorescein video angiography system we developed features a small-caliber endoscope and bright fluorescence images. Because it reveals blood flow in the dead angle areas of the microscope, this novel system could contribute to the safety and long-term effectiveness of aneurysm surgery even in a narrow operative field.

Contrast-enhanced angiographic computed tomography for detection of aneurysm remnants after clipping: a comparison with digital subtraction angiography in 112 clipped aneurysms

BACKGROUND

For preclusion of remnants after aneurysm clipping, a reliable, noninvasive imaging technique is desirable.

OBJECTIVE

To evaluate the reliability of optimized angiographic computed tomography with intravenous contrast agent injection (ivACT) in detecting remnants after aneurysmal clipping compared with digital subtraction angiography (DSA), the gold standard.

METHODS

We included 84 patients with 112 clipped cerebral aneurysms of the anterior circulation. For treatment, 116 clips of cobalt and 57 clips of titanium alloy were used. In each patient, we performed an ivACT with dual rotational acquisition and a DSA. Data from ivACT were postprocessed with a dual-volume technique with newly implemented reconstructions modes. Aneurysm remnants were measured, classified, and correlated with DSA by 2 raters.

RESULTS

In total, 12 remnants were revealed by DSA, meaning a prevalence of 11%. IvACT demonstrated a sensitivity of 75% to 92% and a specificity of 99% in detecting remnants up to a minimal size of 0.7 × 0.3 mm. Classification of remnants by ivACT was identical to that by DSA, and assessment of size showed a significant correlation with DSA (P < .001). No significant differences between cobalt and titanium alloy were revealed concerning artifacts.

CONCLUSION

Optimized ivACT with enhanced postprocessing demonstrated high sensitivity and specificity in detecting remnants after aneurysm clipping in the anterior circulation. Classification and assessment of remnant size and detection of relevant parent artery stenosis showed high accuracy of ivACT compared with DSA. Our results indicate that ivACT might become a noninvasive alternative to DSA for postsurgical control.

Assessment of long-term results of intracranial aneurysm clipping by means of computed tomography angiography

BACKGROUND AND PURPOSE

The aim of this retrospective study was to assess the effectiveness of aneurysm clipping by computed tomography angiography (CTA) in a long-term follow-up.

MATERIAL AND METHODS

The CTA examination was performed in 119 patients who had 143 aneurysms clipped. The examinations were performed 3 to 11 years (mean 6 years) after clipping using a GE Lightspeed PRO16 scanner.

RESULTS

In all cases but one, good quality CTA images, suitable for evaluation of the arteries around the clip site, were obtained. Complete aneurysm closure without neck remnant or regrowth was confirmed in 137 (96%) aneurysms. In 4 (3%) cases, neck remnants were detected (2 on the anterior communicating artery [AComA] and 2 on the middle cerebral artery [MCA]). A total clip slippage from the aneurysm dome was revealed in 1 case. One case of aneurysm re-rupture was noted, 11 years after clipping. The rebleeding was caused by AComA aneurysm regrowth. Among these 6 patients with unsatisfactory clipping, 2 required further treatment and 4 remain under observation. Nineteen 'de novo' aneurysms in other locations were found in 14 (12%) patients. Summing up all of the pathological findings in the study group, there were 18 (15%) patients who needed further management including close surveillance or re-treatment.

CONCLUSIONS

Computed tomography angiography is a simple and reliable method of aneurysm clipping evaluation. The long- term follow-up CTA confirmed the permanent and complete obliteration of 96% of the aneurysms. The rate of unsatisfactory aneurysm closure was 4%, but only 1.4% needed re-treatment during a mean follow-up of 6 years. The annual risk of aneurysm re-rupture was 0.1%.

Optimized angiographic computed tomography with intravenous contrast injection: an alternative to conventional angiography in the follow-up of clipped aneurysms?

OBJECT

The purpose of this study was to evaluate the diagnostic accuracy of an optimized angiographic CT (ACT) program with intravenous contrast agent injection (ivACT) in the assessment of potential aneurysm remnants after neurosurgical clipping compared with conventional digital subtraction angiography (DSA).

METHODS

The authors report on 14 patients with 19 surgically clipped cerebral aneurysms who were scheduled to undergo angiographic follow-up. For each patient, the authors performed ivACT with dual rotational acquisition and conventional angiography including a 3D rotational run. The ivACT and 3D DSA data were reconstructed with different imaging modes, including a newly implemented subtraction mode with motion correction. Thereafter, the data sets were merged by the dual-volume technique, and freely rotatable 3D images were obtained for further analysis. Observed aneurysm remnants were electronically measured and classified for each modality by 2 experienced neuroradiologists.

RESULTS

Digital subtraction angiography and ivACT both provided high-quality images without motion artifacts. Artifact disturbances from the aneurysm clips led to a compromised, but still sufficient, image quality in 1 case. The ivACT assessed all aneurysm remnants as true-positive up to a minimal size of 2.6×2.4 mm in accordance with the DSA findings. There was a tendency for ivACT to overestimate the size of the aneurysm remnants. All cases without aneurysm remnants on DSA were scored correctly as true-negative by ivACT.

CONCLUSIONS

By using an optimized image acquisition protocol as well as enhanced postprocessing algorithms, the noninvasive ivACT seems to achieve results comparable to those of conventional angiography in the follow-up of clipped cerebral aneurysms. The authors have shown that ivACT can provide reliable diagnostic information about potential aneurysm remnants after neurosurgical clipping with high sensitivity and specificity, sufficient for clinical decision making, at least for aneurysms in the anterior circulation located distal to the internal carotid artery. These preliminary results may be a promising step to replace conventional angiography by a noninvasive imaging technique in selected cases after aneurysm clipping.

Sixty-four-row multislice computed tomographic angiography in the diagnosis and characterization of intracranial aneurysms: comparison with 3D rotational angiography

BACKGROUND

Sixty-four-row multislice computed tomographic angiography (CTA) has great potential for use in vascular studies. The aim of our study was to compare 64-slice CTA with three-dimensional rotational angiography (3DRA) in the detection and characterization of intracranial aneurysms with special attention to smaller (<3-mm) aneurysms.

METHODS

In a prospective study, a total of 133 patients were included who successively underwent 64-slice CTA and digital subtraction angiography (DSA) examinations for suspected intracranial aneurysms. The 64-slice CTA, conventional DSA, and 3DRA images were independently reviewed by five readers who performed the presence, shape, dimension, and location of aneurysms. The 3DRA results were considered as the ultimate reference standard.

RESULTS

The reference standard revealed 111 aneurysms in 93 patients: 27 aneurysms were read as <3 mm, 66 were read as being between 3 and 8 mm, and 18 were read as >8 mm. The sensitivities of 64-slice CTA for aneurysms<3 mm, between 3 and 8 mm, and >8 mm were 96.3%, 98.5%, and 100%, respectively, on a per-aneurysm basis. The sensitivities of conventional DSA for aneurysms<3 mm, between 3 and 8 mm, and >8 mm were 85.2%, 100%, and 100%, respectively, on a per-aneurysm basis. The 64-slice CT angiographic images could clearly show the aneurysmal characteristics and the relationship between aneurysms and adjacent branch vessels.

CONCLUSION

Sixty-four-slice CTA is a highly accurate imaging examination of the first-line imaging technique for detecting and characterizing intracranial aneurysms including <3-mm 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.

Comparison of computed tomography angiography with digital subtraction angiography in the assessment of clipped intracranial aneurysms

PURPOSE

To examine whether computed tomography angiography (CTA) is comparable to digital subtraction angiography (DSA) in assessing clipped intracranial aneurysms.

MATERIALS AND METHODS

Retrospective collection of clipped aneurysms that had both CTA and DSA within 2 months of one another. Computed tomography angiograms were independently reviewed by 2 blinded neuroradiologists; rereviewed by one at least 4 months later. Each was classified as complete obliteration, neck remnant, or residual aneurysm. Parent vessel was classified as patent or occluded. Digital subtraction angiograms were reviewed in a similar manner by a third blinded neuroradiologist.

RESULTS

Forty-eight patients with 53 clipped aneurysms were collected. On DSA, 35 were completely obliterated, 10 neck remnants, and 8 residual aneurysms. The ability of CTA to detect residual aneurysms versus complete obliterations or neck remnants was excellent (mean sensitivity, 88%; specificity, 100%; positive predictive value [PPV], 100%; negative predictive value [NPV], 98%). The ability of CTA to detect neck remnants versus complete obliterations was poor (mean sensitivity, 20%; specificity, 99%; PPV, 83%; NPV, 81%). The CTAs were good at detecting parent vessel occlusion (mean sensitivity, 88%; specificity, 97%; PPV, 75%; NPV, 99%). Interrater and intrarater agreement was good to excellent for aneurysm and parent vessel assessment, with kappa values ranging from 0.6 to 1.0.

CONCLUSIONS

Computed tomography angiography has high sensitivity and specificity for residual aneurysm detection and parent vessel occlusion. It is not accurate in neck remnant detection, although these were small and of uncertain clinical significance. This suggests that CTA is useful for follow-up of clipped aneurysms. However, given the potential to miss neck remnants or small residual aneurysms, it is recommended to perform initial DSA and CTA to select cases in which CTA follow-up is appropriate.

Usefulness of multislice computerized tomographic angiography in the postoperative evaluation of patients with clipped aneurysms

BACKGROUND

The aim of our study was to evaluate the diagnostic efficacy of multislice computed tomographic angiography (MSCTA) regarding exclusion quality after aneurysm clipping.

METHODS

Sixty patients (74 aneurysms) underwent microsurgical exclusion using titanium clips. The presence of aneurysm remnants on MSCTA was compared by a neuroradiologist to 2D digital subtraction angiography (DSA), which was considered as a reference examination. The contribution of 3D DSA was assessed in a subpopulation of 29 patients (35 aneurysms).

RESULTS

With 2D DSA, six aneurysm remnants (8%) were diagnosed, and only five (7%) by MSCTA. The specificity and sensitivity were 98.5 and 83%, respectively. MSCTA failed to demonstrate one large remnant (>2 mm) because of clip artifacts (six clips). With 3D DSA six supplementary remnants were diagnosed. Two were large remnants blinded by vessel overlaps and clip artifacts. Four were small "dog-eared" remnants (< or =2 mm). No additional treatment was required for small remnants.

CONCLUSION

In the postoperative period, MSCTA was considered a useful tool to evaluate the large remnants as well as a non-invasive ulterior examination for suspected bifurcation. Nevertheless, 3D DSA is still required for an accurate evaluation of aneurysms treated by more than three clips.

Brain death confirmation: comparison of computed tomographic angiography with nuclear medicine perfusion scan

INTRODUCTION

: Brain death is a difficult diagnosis to make, relying primarily on clinical examination. Ancillary tests are used when confounders exist. Nuclear medicine perfusion test (NMPT) is currently the preferred test for confirming brain death. Computed tomographic angiography (CTA) may be an alternative test to confirm brain death. It is readily available 24 hours a day at most level I trauma centers and is easy to perform.

METHODS

: Patients with a clinical examination consistent with brain death were selected from the intensive care unit at a 550-bed teaching hospital. The patients underwent NMPT followed immediately by CTA. Both studies were read by radiologists blinded to the results of the alternative study. Absence of brain perfusion confirmed brain death. Multiple independent variables were collected on each patient including demographics, core body temperature, apnea challenge, mechanism of injury, timelines, renal function pre- and posttesting, organ donation, and time to procurement.

RESULTS

: There were 25 patients enrolled in the study with multiple injury patterns. No false negative exams were identified on CTA when compared with NMPT. Three patients without flow on NMPT showed minimal flow on CTA. Each of these had open skull defects. Sensitivity of CTA was 0.86 and specificity was 1. There was no induced morbidity with regards to renal failure and organ donation.

CONCLUSION

: CTA is a quick and efficient test for brain death confirmation. CTA demonstrated no false negative studies. The resolution of CTA seems to have an increased sensitivity for cerebral blood flow. Further studies with larger sample sizes need to be performed.

Comparison of multislice computed tomography angiography and digital subtraction angiography in the detection of residual or recurrent aneurysm after surgical clipping with titanium clips

PURPOSE

To determine the diagnostic accuracy of 3D-CTA using volume rendering (VR) in the detection of residual or recurrent cerebral aneurysms after clipping.

MATERIAL AND METHODS

Between January 2006 and November 2007, 45 patients (20 female, 25 male) with 50 intracranial aneurysms treated using titanium clips were enrolled in this study. IADSA and 3D-CTA were performed within 1 month after surgery in 27 (60%) patients, after 1 year in 12 (26%) patients and after 5 years in six (13%) patients. In blinded fashion, CTA and DSA images were independently interpreted by two senior neuroradiologists with 7 years of experience in vascular diagnostic neuroradiology. The diagnostic performance of MDCTA compared with DSA for the detection of aneurysm remnants was measured by receiver operating characteristic (ROC) analysis. The area under the ROC curve, 95% confidence interval (CI), sensitivity, and specificity were calculated.

RESULTS

For the detection of residue-recurrent aneurysm; the sensitivity and specificity of MDCTA were 87.5% (95% CI = 52.9-97.8%) and 97.4% (95% CI = 86.5-99.5%) for the first reader and 87.5% (95% CI = 52.9-97.8%) and 100% (95% CI = 90.8-100%) for the second reader respectively. Receiver operating characteristic (ROC) analysis revealed good diagnostic performance for 3D-CTA (mean area under ROC curve (Az) = 0.98 and 0.99 for the first and the second observer, respectively) The kappa values extracted from the interobserver concordance analysis for agreement observers regarding the use of MDCTA for assessment of a remnant neck was 0.62.

CONCLUSION

Using MDCTA, it is possible to demonstrate the status of intracranial aneurysms after surgical clipping in the immediate postoperative period as well as long-term follow-up with an high sensitivity and specificity when comparing with the findings of DSA.

Does black blood MRA have a role in the assessment of intracerebral aneurysms?

The aim of this study was to assess whether the addition of a black blood (BB) sequence to standard three-dimensional time-of-flight (3D-TOF) imaging yields improved quantitative assessment of intracranial aneurysms. Thirty seven patients with 42 proven intracranial aneurysms underwent intra-arterial digital subtraction angiography, 3D-TOF and BB MRI imaging. This multimodality imaging was used to create a composite reference aneurysm description. The 3D-TOF and BB imaging were graded on a subjective seven-point scale to determine what improvement if any the addition of BB imaging yielded. Comparison of measurements from all imaging modalities demonstrated no significant difference (p < 0.01) in aneurysm length/width or parent vessel width. Aneurysm neck measurements were underestimated on 3D-TOF images although there was still a significant correlation (R(2) = 0.72, p < 0.05). Comparison of TOF and BB examinations to the composite reference using the Wilcoxon signed-rank test showed significant improvement in the demonstration of the aneurysm to parent/branch vessels and the morphology/size of the aneurysm neck, particularly in the setting of local haematoma or slow flow (p < 0.001). We propose the addition of the BB sequence as a useful adjunct to 3D-TOF imaging particularly when detailed aneurysm morphology is required or there is thrombus in subarachnoid space.

Computed tomographic angiography in the evaluation of clip placement for intracranial aneurysm

BACKGROUND

Computed tomographic angiography (CTA) has been shown to reliably detect aneurysms pre-operatively. The aim of this study was to compare the ability of post-operative CTA to detect aneurysmal remnants in connection with clip placement compared with digital subtraction angiography (DSA). Furthermore, special attention was paid to identifying factors influencing the image quality of CTA.

METHOD

Between January 2005 and January 2006 a total of 76 patients with intracranial aneurysms were treated in our department. Thirty-two patients with a total of 33 clipped aneurysm were included in this study. All patients underwent CTA and DSA after surgery. Two investigators, each blinded to the classifications of the other, assessed image quality and clip placement.

FINDINGS

In three patients aneurysmal remnants could be detected with CTA and DSA. One 2-mm aneurysmal remnant was not clearly identified on CTA; two small (<2-mm) aneurysmal remnants were definitely not seen on CTA. A single titanium clip was used for aneurysmal clipping in 26 patients, two clips were needed in six patients and one aneurysm required three clips being used. Overall, use of one titanium clip tended to result in better image quality. In addition, clip-gantry angles between 30 degrees and 60 degrees tended to yield better image quality.

CONCLUSION

Post-operatively, CTA can be recommended as a reliable non-invasive diagnostic tool only with optimal image quality and with this criterion up to 66% of the aneurysms can be evaluated. Titanium artefacts, especially in the important zone (<2 mm) around the clip in which small aneurysmal remnants can occur, can render adequate evaluation impossible. CTA image quality depends on the number of titanium clips used, but clip-gantry-angle does not significantly influence the image quality.

Subtraction 3D CT angiography with the orbital synchronized helical scan technique for the evaluation of postoperative cerebral aneurysms treated with cobalt-alloy clips

BACKGROUND AND PURPOSE

CT angiography (CTA) has been used for the evaluation of intracranial aneurysms and recently has been applied to assess postoperative aneurysms treated with titanium-alloy clips. We investigated the clinical usefulness of subtraction CTA by using the orbital synchronized helical scan technique (OSHST) for evaluating intracranial aneurysms surgically treated with cobalt-alloy clips.

MATERIALS AND METHODS

We scanned an agar gel phantom with a cobalt-alloy clip mounted in the center by using subtraction CT with and without OSHST. Eighteen patients (20 aneurysms) who underwent surgery with cobalt-alloy clips were postoperatively evaluated with subtraction CTA with OSHST, and the results were compared with those from digital subtraction angiography. Two neuroradiologists independently evaluated the 3D CTA images and source images with and without subtraction for the presence of residual flow in the aneurysm and stenotic change in parent or neighboring arteries.

RESULTS

For the phantom study, significantly fewer artifacts from clips were noted on images obtained by using subtraction CT with OSHST than on those obtained without OSHST. For the clinical study, subtraction CTA with OSHST also showed fewer clip artifacts than did conventional CTA. Image quality was poor, and we were unable to diagnose residual neck for 5% (1/20) with subtraction CTA with OSHST and 75% (15/20) with conventional CTA. For evaluation of adjacent vessels, image quality was poor for none (0/20) with subtraction CTA with OSHST and for 55% (11/20) with conventional CTA. For subtraction CTA with OSHST, sensitivity in detecting residual neck was 1.0, and specificity was 0.94. For conventional CTA, sensitivity and specificity were both 0.25.

CONCLUSIONS

OSHST is a useful technique for subtracting cobalt-alloy clips, and subtraction CTA with OSHST is available for evaluating aneurysms after clipping with cobalt-alloy clips.

Diagnostic accuracy of CT angiography with matched mask bone elimination for detection of intracranial aneurysms: comparison with digital subtraction angiography and 3D rotational angiography

BACKGROUND AND PURPOSE

Our aim was to determine the diagnostic accuracy of multisection CT angiography combined with matched mask bone elimination (CTA-MMBE) for detection of intracranial aneurysms compared with digital subtraction angiography (DSA) and 3D rotational angiography (3DRA).

MATERIALS AND METHODS

Between January 2004 and February 2006, 108 patients who presented with clinically suspected subarachnoid hemorrhage underwent both CTA-MMBE and DSA for diagnosis of an intracranial aneurysm. Two neuroradiologists, independently, evaluated 27 predefined vessel locations in the CTA-MMBE images for the presence of an aneurysm. After consensus, diagnostic accuracy of CTA was calculated per predefined location and per patient. Interobserver agreement was calculated with kappa statistics.

RESULTS

In 88 patients (81%), 117 aneurysms (82 ruptured, 35 unruptured) were present on DSA. CTA-MMBE detected all ruptured aneurysms except 1. Overall specificity, sensitivity, positive predictive value, and negative predictive value of CTA-MMBE were 0.99, 0.90, 0.98, and 0.95 per patient and 0.91, 1.00, 0.97, and 0.99 per location, respectively. Sensitivity was 0.99 for aneurysms >/=3 mm and 0.38 for aneurysms <3 mm. Interobserver agreement for aneurysm detection was excellent (kappa value of 0.92 per location and 0.80 per patient).

CONCLUSION

CTA-MMBE is accurate in detecting intracranial aneurysms in any projection without overprojecting bone. CTA-MMBE has limited sensitivity in detecting very small aneurysms. Our data suggest that DSA and 3DRA can be limited to the vessel harboring the ruptured aneurysm before endovascular treatment, after detection of a ruptured aneurysm with CTA.

Noninvasive imaging of treated cerebral aneurysms, Part II: CT angiographic follow-up of surgically clipped aneurysms

Although not useful for the evaluation of coiled aneurysms, CT angiography (CTA) is far superior to MR angiography (MRA) for the evaluation of aneurysms after surgical clipping. Using the latest multidetector row scanners and optimized imaging parameters, CTA can often effectively depict and follow small aneurysm remnants; demonstrate patency, stenosis, or vasospasm in the adjacent parent vessels; and provide surveillance of the entire cerebrovasculature for de novo aneurysms after surgical clipping. Despite these advances, conventional angiography remains the gold standard for the evaluation of surgically treated aneurysms and should be liberally used to resolve any cases of diagnostic uncertainty on noninvasive imaging.