Effects of 16-multi-detector row CT aortography with lower tube current

Abstract

To study the effects of 16-multi-detector row CT (MDCT) aortography with lower tube current in diagnosis of aortic diseases. The study was conducted in 2 steps. In the first step, 58 patients with suspicious aortic disease or after operation on the aorta underwent 16-MDCT aortography for 70 times. Ten of them underwent scanning with conventional tube current of 175 mAs and the other 60 patients were divided into 3 groups according to their bogy weights: <65 kg group (n=20) receiving the lowest tube current of 25 mAs, 65-75 kg group (n=20) receiving the lowest tube current of 50 mAs, and >75 kg group (n=20) receiving the lowest tube current of 75 mAs. In the second step 60 patients with dissecting aneurysm, underwent 16-MDST aortography and were divided into 3 groups according to their body weight too: <65 kg group (n=20) receiving the lowest tube current of 50 mAs, 65-75 kg group (n=20) receiving the lowest tube current of 75 mAs, and >75 kg group (n=20) receiving the lowest tube current of 100 mAs, all 25 mAs more compared with the corresponding groups in the first step. The weighted CT dose index (CTDI), scanning length, and dose length produce (DLP) were recorded. The diagnostic accuracy rates of the images from the low dose groups were compared with those of the higher dose groups. The data of the first step showed that the CTDI values of the patients who received 25 mAs, 50 mAs, and 75 mAs tube current were 11.3%, 29.0%, and 42.7% that of the conventional tube current group (all P < 0.001) and the DLP values of the 3 low dose groups were also significantly lower than that of the conventional tube current group (all P < 0.001). The diagnostic accuracy rate of the 25 mAs, 50 mAs, and 75 mAs groups were 60% , 85%, and 85% that of the conventional tube current group. The results of the second step showed that the CTDI values of the 50 mAs, 75 mAs, and 100 mAs groups were 29.0%, 42.7%, and 57.3% that of the conventional tube current group respectively, and the DLP values of the 3 low dose groups were also significantly lower than that of the conventional group ( all P < 0. 001); and the 50 mAs, 75 mAs, and 100 mAs groups all showed good three-dimensional reconstruction imaging qualities, all with the diagnostic accuracy rate of 100%. The crossing section and three-dimensional images all showed excellent diagnostic image quality. 16-MDCT aortography with the tube current at the doses 50 mAs to 100 mAs suffices to diagnose aortic diseases in patients with different body weights. Higher tube current should be used in dissecting aneurysm. The tube current at the dose of 100 mAs satisfies the imaging and diagnosing of all kinds of aortic diseases in the patients with any body weight.