Online Angular Tube Current Modulation in X-Ray Computed Tomography: Can Tube Current Be Modulated Appropriately?
K Matsubara1*, H Koshida2, T Takata2, J Horii2, H Iida2, K Koshida1, O Matsui1, A Fukuda3, (1) Kanazawa University, Kanazawa, (2) Kanazawa University Hospital, Kanazawa, (3) Shiga Medical Center for Children, MoriyamaSU-D-217BCD-2 Sunday 2:15:00 PM - 3:00:00 PM Room: 217BCD
Purpose: In X-ray computed tomography (CT), X-rays are significantly less attenuated in the anteroposterior direction and more in the lateral direction. Therefore, the tube current should be adjusted within one gantry rotation using angular tube current modulation (TCM). The aim of this study was to evaluate whether online angular TCM could reduce radiation dose appropriately.
Methods: A 128-detector dual-source CT (SOMATOM Definition Flash; Siemens Healthcare, Erlangen, Germany) and an online TCM system (CARE Dose 4D; Siemens Healthcare) were used. Dose profiles were acquired using the CT Dose Profiler (RTI Electronics, Molndal, Sweden) and an elliptical cylindrical phantom (MHT; Kyoto Kagaku, Kyoto, Japan) for helical CT scans with and without TCM. In addition, absorbed dose distributions within a single section were acquired using an anthropomorphic phantom (RAN110; The Phantom Laboratory, Salem, NY) and radiophotoluminescent glass dosimeters (RPLDs) (GD-302M; Chiyoda Technol, Tokyo, Japan) for helical CT scans with and without TCM after placing RPLDs within all holes of one section and pasting them around the section. A graph of each absorbed dose distribution was drawn using graphing software (ORIGIN 8.6; OriginLab, Northampton, MA).
Results: The acquired dose profiles suggested that online angular TCM could adjust the tube current in near-real time according to the attenuation measured from the previous projection. The profiles gradually stabilized because the tube current was adjusted properly. The absorbed doses were low and the distributions were stable with TCM compared with those without TCM.
Conclusions: In X-ray CT, an online angular TCM can reduce radiation dose effectively by adjusting tube current within one gantry rotation in near-real time.