[Diagnosis of ruptured and unruptured cerebral aneurysms with three-dimensional CT angiography (3D-CTA)]

Three-dimensional CT angiography (3D-CTA) is a new, minimally invasive technique for the diagnosis of cerebral aneurysms. The purpose of this study is to compare the diagnostic value of 3D-CTA for ruptured and unruptured cerebral aneurysms with that of MR angiography (MRA) and digital subtraction angiography (DSA). Forty-one cases consisting of 11 cases of ruptured aneurysms and 30 cases of unruptured aneurysms, with a total of 67 cerebral aneurysms, were included in this study. 3D-CTA was performed with a bolus injection of nonionic contrast medium on the SOMATOM PLUS-S scanner and the ProSeed Accell scanner. Three-dimensional images were obtained by both shaded surface reconstruction (SSR) method and maximum intensity projection (MIP) method. The CT values of cisternal clot in cases of ruptured cerebral aneurysms did not exceed 90HU in any of the cases. The effect of SAH was, therefore, eliminated in the SSR images through a threshold level processing of a CT value of 150HU. All the cerebral aneurysms were visualized by this process. With regard to the detectability of cerebral aneurysms, 3D-CTA was able to demonstrate cerebral aneurysms with diameters of larger than 1mm as well as giant aneurysms which MRA would sometimes fail to reveal. 3D-CTA was superior to MRA and DSA in making diagnosis of small aneurysms such as those with diameters of less than 3mm.(ABSTRACT TRUNCATED AT 250 WORDS)