CT angiography with SSD and VRT reconstructions in diagnosing of intracranial aneurysms

CT angiography (CTA) is used more and more commonly in diagnosing of intracranial aneurysms. However, it is still doubtful if CTA appearance is a sufficient base for planning either operative or endovascular treatment. Therefore there are attempts to improve technically the value of CTA. The aim of the study was to assess the value of SSD (surface shaded display) and VRT (volume rendering technique) reconstructions in diagnosing of aneurysms. In 35 patients with 38 intracranial aneurysms, CTA examinations were analyzed. In all of them, apart from standard MIP reconstructions, SSD and VRT techniques were used. CTA studies were performed using spiral acquisition, after injection of 120 ml of contrast medium (5 ml/s). Then source images were postprocessed using EDIT software. The obtained images were reconstructed with MIP, SSD and VRT techniques. The protocol for SSD was as follows: lower threshold of density 100-150 Hounsfield units (HU); upper threshold 3000 HU; coronal, sagittal and oblique planes. VRT reconstructions were performed using two methods: 1. imaging of vessels: density 100-550 HU, opacity 100%, refraction index 100%. 2. colour imaging of vessels (density 80-550 HU, opacity 80-90%) and bones (density 450-3000 HU, opacity 100%, refraction index 100%). In all patients the morphological details of the aneurysms in MIP, SSD and VRT reconstructions were evaluated. In all cases SSD and VRT allowed to obtain additional information: better visualization of the sac and neck of the aneurysm, precise assessment of the relationship between the aneurysm and adjacent vessels and bone structures, visualization of the bleeding point. The most efficient method in evaluating of the details mentioned above was VRT. SSD was slightly inferior to VRT, except for assessment of the relationship to the bone structures. MIP images were inferior both to VRT and SSD. Evaluation of CTA is based mainly on the source and MIP images. However, VRT and SSD often allow for better assessment of the anatomical details of the aneurysm and thus, more precise planning of the operative or endovascular treatment. (author)