Indexed on: 08 May '10Published on: 08 May '10Published in: Academic Radiology
The aim of the study was to investigate the optimal protocols of dual-source computed tomography (CT) angiography in aortic stent grafting in terms of image noise and radiation dose, based on an in vitro phantom study.A series of helical CT cans were performed on a human aorta phantom using a dual-source CT scanner with kVp of 100, 120, and 140, corresponding mAs of 180, 150, and 100; slice thickness of 1.0, 1.5, and 2.0 mm; and pitch value of 0.5, 1.0, and 1.5, respectively. Image quality was determined by measuring the standard deviation (SD) on three-dimensional virtual intravascular endoscopy (VIE) images. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were measured on two-dimensional (2D) axial images at superior mesenteric artery (SMA), renal arteries, and aneurysm. Effective dose was determined based on dose-length product.SD measured on VIE images was independent of kVp and pitch values but was determined by the slice thickness (P < .05) at the SMA and renal arteries. SNR and CNR measured on 2D images showed significant differences between variable kVp values and slice thicknesses (P < .05), but were independent of pitch values. The mean estimated effective dose for 120 kVp and 140 kVp protocols were 2.66 +/- 0.21 mSv and 2.68 +/- 0.18 mSv, respectively. The mean estimated effective dose for 100 kVp protocol was significantly lower (1.97 +/- 0.07 mSv, P < .0001). This indicates a reduction of 26.5% radiation dose when the kVp was lowered from 140 to 100.A scanning protocol of 1.5-mm slice thickness, pitch 1.5 with 100 kVp, and 180 mAs is recommended for a dual-source CT angiography in aortic stent grafting as it leads to significant reduction of radiation dose while achieving diagnostic images.