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.
ABSTRACT
Objective To evaluate the relationship between field of view (FOV) and quality of CT images. Methods Scanning of the phantoms of spatial resolution and density resolution was performed with FOVs of 25 cm?25 cm, 35 cm?35 cm, and 42 cm?42 cm, respectively, and the spatial resolution and density resolution of CT images with different FOVs were measured. 20 patients underwent CT scanning using 25 cm?25 cm and 35 cm?35 cm FOVs, respectively. The images were evaluated by 3 qualified CT doctors by using a double-blind reading. Results As FOVs changed, the spatial resolution and density resolution were different. The best spatial resolution and density resolution were obtained on 25 cm?25 cm FOV images. The best spatial resolution could distinguish four 0.6 mm-diameter eyelets, and the best density resolution could distinguish five 2.5 mm-diameter eyelets. The CT images with 25 cm?25 cm FOV were obviously better than those with 35 cm?35 cm FOV (P