| Background and Purpose Intracranial aneurysms are relatively common, with a reported prevalence of 3%-6% in the general population, predominantly in women. These aneurysms may rupture, ruptured aneurysms not only cause subarachnoid hemorrhage (SAH) but can also cause intraventricular hemorrhage. Mortality is high among patients with this condition, and prompt localization of the aneurysm is critical for determining the appropriate neurosurgical or endovascular intervention. Moreover, the aneurysms treated by clipping or coiling may have remnants and recurrences. Conventional digital subtraction angiography (DSA) is widely regarded as the gold standard in the diagnose and follow-up of intracranial aneurysms. However, DSA is time consuming, invasive and relatively expensive, and DSA has been reported to carry a 1% risk of complications and a 0.5% risk of permanent neurological deficit. DSA requires more time to perform and may be associated with a higher rate of rebleeding. For all these reasons, it can be invaluable to find an accurate minimally invasive imaging method for the diagnose and follow-up of intracranial aneurysms. In addition, SAH due to ruptured aneurysms often results in poor prognosis, and mortality is high among patients with this condition. Most of the patients die of rebleeding, and the appropriate treatment can be performed to minimize rebleeding. Hence, rapid diagnostic evaluation and treatment are crucial for the patient’s outcome.Computed tomographic angiography (CTA) and MR angiography (MRA) are practically noninvasive cerebral vessel methods, and 2-dimensional (2D) and 3-dimensional (3D) images reconstructed from a single set of raw images can be viewed in any direction with commercially available workstations and softwares There have been numerous studies to compare four-row multislice CTA with DSA, and sensitivity of four-slice CTA in the investigation of aneurysms has been reported to range from 81 to 100%, with an accuracy range from 79 to 94.9%. Nevertheless, four-slice CTA has demonstrated a limited sensitivity and specificity for smaller than 5 mm aneurysms. Recently, implementation of 16-row multislice CT technology has led to considerable progress in the field of CTA. A 16-slice CT scanner provides high-resolution 3D reconstructions and is capable of acquiring images from the first cervical vertebra to the superior aspect of the frontal sinuses in a single acquisition, which may in turn improve the diagnostic accuracy of this technique. The purpose of our study was to assess the accuracy of 16-row multislice CTA in diagnosis of intracranial aneurysms, and the clinical value of CTA and MRA in the therapy and follow-up of aneurysms.Materials and Methods (1) 471 consecutive patients underwent CTA and DSA for suspected intracranial aneurysms. This was performed with a 16-detector row machine, with a detector slice of 0.75 mm, reconstruction interval of 0.40 mm, and timing determined by bolus trigger. CTA and DSA images were reviewed by two independent neuroradiologists who assessed the presence, shape, orientation, neck, and location of the aneurysms and their relationship to other structures using maximum-intensity projections, shaded-surface display, and volume rendering techniques reconstructions. DSA or surgical findings or both were considered as the ultimate reference standard against which the diagnostic accuracy of CTA and DSA were compared; (2) 329 patients were included in the study and successively underwent CTA and DSA examination for suspected intracranial aneurysms. Using maximum-intensity projections and volume-rendering techniques, the neuroradiologist performed shape, size and location of the aneurysms, and the relationship of aneurysms to adjacent branch vessels. The 16-slice CTA data was used to determine whether the aneurysm was suitable for endovascular treatment or whether a surgical procedure was preferable; (3) Forty-eight patients with 51 clipped intracranial aneurysms underwent 16-row spiral CT assessment, and the aneurysm shape, size and location, as well as the residual aneurysms and patency of the parent artery after clipping, were assessed with maximum-intensity projections and volume-rendering techniques; (4) In a prospective study, 65 consecutive patients treated with detachable coils underwent DSA and MRA at 1.5T with a follow-up range from 3 to 12 months after coil placement. MRA images were evaluated for presence of aneurysm remnants, and DSA results were considered as a reference standard.Results (1) Combining CTA, DSA and intraoperative findings, 267 aneurysms were detected in 244 of the 471 patients. Eight aneurysms were considered as false-negative interpretation with CTA, four were considered as false-positive interpretation with CTA, ten were considered as false-negative interpretation with DSA, and two were considered as false-positive interpretation with DSA. The sensitivity, specificity, and accuracy of 16-slice CTA in detecting all aneurysms were 97.0%、98.3% and 97.6%, respectively, on a per-aneurysm basis. The positive predictive value and negative predictive value of detecting aneurysms on 16-slice CTA on a per-aneurysm basis were 98.5% and 96.6%, respectively. The sensitivity, specificity, and accuracy of DSA in detecting all aneurysms were 96.2%、99.1% and 97.6%, respectively, on a per-aneurysm basis. The positive predictive value and negative predictive value of detecting aneurysms on DSA on a per-aneurysm basis were 99.2% and 95.7%, respectively. There was no statistically significant difference in sensitivity between 16-slice CTA and DSA (P > 0.05). 3D 16-slice CTA images show more clarity and accuracy in the relationship of aneurysms to bone structures and adjacent branch vessels; (2) 202 intracranial aneurysms were identified in 181 of the 329 patients. Four aneurysms were missed when using CTA, and seven aneurysms were not clearly depicted at DSA. The sensitivity, specificity, and accuracy of 16-slice CTA for detecting aneurysms were 98.0%, 98.0% and 98.0%, respectively. 115 aneurysms were suitable for endovascular coiling by using the 16-slice CT angiographic images, and 112 aneurysms were successfully treated by endovascular coiling; (3) 37 aneurysms were saccular in shape, 9 irregular and 5 fusiform. The most common location for all the aneurysms was middle cerebral artery (31%), and the second location was posterior communicating artery (29%). The average craniocaudal size was 6.9 mm, the average dome size was 5.5 mm and the average neck size was 3.4 mm. 49 aneurysms were treated with a single clip and two with two clips. Three clipped aneurysms with incomplete closure were identified by the 16-slice CTA, and the parent artery could be reliably evaluated close to the clip; (4) The sensitivity, specificity, and accuracy of MRA for the residual aneurysms were 80% (95% confidence interval (CI): 51.9–95.7%),100% (97.5% CI: 93.5–100%) and 95.7% (95% CI: 88.0–99.1%), respectively. The positive and negative predictive values were 100% and 94.8%, respectively. There was no statistically significant difference in accuracy between MRA and DSA.Conclusion (1) 16-slice CTA has a very high sensitivity, specificity, and accuracy of detecting aneurysms, and it is sensitive enough to replace conventional DSA in the triage, diagnosis, and treatment planning in patients with intracranial aneurysms. The theoretical gold standard in detecting aneurysms should not be only conventional DSA; (2) 16-slice CTA offers high diagnostic accuracy not only in the detection of intracranial aneurysms,but also in guiding the endovascular therapy of aneurysms; (3) 16-slice CTA has high accuracy and clinical value in the preoperative and postoperative diagnosis of clipped intracranial aneurysms, and should become an alternative examination of the preoperative and postoperative assessment of clipped aneurysms. A diagnostic-only DSA examination could be avoided, when 16-slice CTA provides sufficient diagnostic information to guide surgical treatment of aneurysms; 4) MRA at 1.5T is an accurate and noninvasive imaging examination in the follow-up of patients with intracranial aneurysms treated with coil placement. |
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