ABSTRACT
Objective To explore the feasibility of low-dose multi-slice computed tomography(MSCT) scan on pulmonary artery three-dimensional angiography, and the relationship between pulmonary VR image quality and the SD value of plain scan. Methods Pulmonary artery CT examination was performed in 87 patients. 63 volunteers were administered with low dose as a low-dose group, and the other 24 were scanned with conventional dose as a routine group. Both plain scans were use conventional dose of pulmonary scan with 150 mAs, and the low-dose pulmonary enhanced scans were used with 60 mAs. The images were post-processed with volume rendering(VR) and classified into three grades A, B and C, and VR image quality levels of both groups compared. The receiver operating characteristic curve( ROC) was used to analyze the relationship between VR image quality level and SD value of plain scan image SD value. Results The VR image level of A-class was 100% in the conventional dose group, and 85. 7% was in the low dose group . According to the correlation analysis between the standard deviation(SD) value of plain scan image and pulmonary artery VR image quality, the area under curve in receiver-operated characteristic analysis was 0. 906. Conclusions The low-dose scan of pulmonary artery three-dimensional angiography is feasible. Using 60 mAs low-dose in pulmonary artery enhanced scan could ensure better image quality. With the SD value of the plain scan decreased, the pulmonary artery VR image quality is improved.
ABSTRACT
Objective To explore the feasibility and reasonable of low-dose scan on abdominal angiography in 64-slice spiral helical CT. Methods Phantom test: at 120 KV and from 200 mAs to 30 mAs at an interval of 10 mAs in each image acquisition, it was measured standard deviation (SD) of CT number, high contrast resolution and low contrast resolution, and then analyzed the relationship between the three parameters and the mAs values. Three mAs values were chosen to undertake clinical analysis.Clinical analysis: 90 randomly selected objects with abdominal angiography were divided into three groups,scanning with above three mAs values.Measurement of the SD value at the plain scan images was performed and the enhanced low-dose scan images were used post-processing with three-dimensional volume reconstruction (VR). The VR images were classified into three grades (excellent, moderate, bad) with the blind evaluation of three CT radiologists. The quality-correlation analysis was used between the standard deviation (SD) values of plain scan image and abdominal angiography VR image. Results According to the quality-correlation analysis between the standard deviation (SD) value of plain scan image and abdominal angiography VR image, the area under curve in receiver-operated characteristic (ROC) analysis was 0.921, 0.906 and 0.893 in each three group, respectively. Conclusions The low-dose scan of abdominal angiography is feasible. 80mAs can ensure better image quality. The enhanced scan probably can use 60mAs when the SD value is less than 5.78 in the plain scan; but when the SD value of plain scan is greater than 11.8, the enhanced scan is used best 100 mAs or higher.