Room: Exhibit Hall | Forum 9
Purpose: Although automatic tube current modulation (ATCM) system has been one of the dose optimization methods to enable patient doses at an acceptable level, there is a lack of methods to access ATCM performance of CT dose output. The main aim of this study is to establish a dose evaluation method for ATCM with a novel phantom and MOSFET detectors.
Methods: Measurements were performed on a United Imaging CT scanner with a novel PMMA phantom and a MOSFET dose measurement system (Thomson & Nielsen, Ottawa, Canada). The geometry of the home-made phantom is designed according to the X-ray attenuation equivalent in human body in Xã€?Y and Z dimensions. The MOSFET dosimeters were placed along the hole in the phantom at a 1cm interval to obtain the dose profiles under ATCM, and the performance of the MOSFET dose system was evaluated in in Secondary Standard Dosimetry Lab .
Results: MOSFETs exhibits a good linear relationship to the nominated dose range from 0.4cGy to 24.4cGy and have a good uniformity. The angular responses of the MOSFETs was found to be in the range of 0.88Â±0.001 to 1.15Â±0.001. ATCM for different level settings followed similar patterns in the different axes and dose profile remained relatively constant along the central axis compared with those along the short axis and long axis. However, the dose levels didnâ€™t change by the same factor.
Conclusion: It indicates that the MOSFET is suitable for CT diagnostic radiology and evaluating the output dose of CT scanners in routine clinical CT diagnostic radiology. The novel phantom with MOSFET detectors could be an applicable evaluation method for ATCM. Measurements of the dose profile in the novel phantom showed that different modulations have their own internal algorithms instead of establishing a simple linear relationship between dose levels and mAs levels.
Funding Support, Disclosures, and Conflict of Interest: This work was supported by the Natural Science Foundation of China (grant number 11475047)
Not Applicable / None Entered.