Influences of imaging parameters on multi-slice CT with automatic tube current modulation:an experimerntal study

Abstract:

Objective：To explore the influences of imaging parameters on image quality and radiation dose in multi-slice CT with au－tomatic tube current modulation（ATCM）. Methods：An equivalent anthropomorphic phantom was scanned using a 16-slice multi-slice spiral CT with ATCM. ATCM was studied with variable positioned image acquisition parameters（tube angle，tube current，tube volt－age） and spiral scan acquisition parameters[noise index（NI），pitch，detector collimation configuration and tube voltage]. Changes in tube turlent，volume CT dose index（CTDIvol） and image noise resulting from the modulation were calculated and compared. Results：Value of CTDIvol from the position angle of 90° was 28.45% higher than that from the position angle of 0°. Value of CTDIvol was de－creased when tube current and tube voltage were increased for positioned image. Image noise was increased and value of CTDIvol was decreased alongside the growth of the NI. Image noise was remained in constant in spite of changes of pitch，detector collimation or tube voltage. Value of CTDIvol came to the peak at pitch of 0.938. Value of CTDIvol was increased by 6.44% when pitch changed from 0.562 to 0.938 and was decreased respectively by 11.67% and 23.05% when pitch changed from 0.938 to 1.375 and 1.75. Wider and thicker detector collimation configuration had higher X-ray dose utilization ratio and lower radiation dose. Value of CTDIvol was decreased when the tube voltage was increased. Conclusions：Positioned image acquisition parameters must be standardized to ensure that ATCM technique can exert effects normally. Imaging parameters should be selected rationally to guarantee that ATCM technique can control the image quality well and reduce the radiation dose.