Program Information
Preliminary Study of Size-Specific Dose Estimates in Adult Abdomenal CT Examinations in Taiwan
H Tsai1*, Y Hwang2 , Y Hu1 , (1) Department of Medical Imaging and Radiological Sciences, Chang Gung University, Taoyuan, Taiwan, (2) Department of Medical Imaging and Intervention, Chang Gung Memorial Hospital at Linkou, Taoyuan, Taiwan.
Presentations
TU-G-CAMPUS-I-8 (Tuesday, July 14, 2015) 5:00 PM - 5:30 PM Room: Exhibit Hall
Purpose: This study was to investigate size-specific dose estimates (SSDE) for routine adult abdominal CT examinations in Taiwan.
Methods: A national survey was conducted in Taiwan in 2014 to investigate SSDEs for routine adult abdominal CT examinations. The hospitals involved in this study provided CT images of their typical patients. The CT image in the level of the middle liver was selected to record the corresponding tube current, slice mAs or effective mAs. The image was also used to estimate the dimensions of patient as measuring the lengths in the anterior to posterior (AP) and lateral (LAT) directions. The effective diameter was then calculated from AP and LAT, and used to look up conversion factors in the AAPM 204 report. The volume CTDI (CTDIvol) for each CT unit was measured on sites using a 32-cm cylindrical standard dose phantom and a calibrated pencil-type ionization chamber. Individual patient's SSDEs were then calculated from the corresponding SSDE conversion factor and the CTDIvol.
Results: The study cohort included 111 CT units. The ratio of turning on automatic tube current modulation (ATCM) or not is 88:23. Effective diameters are 258.7±25.1 mm (167-366 mm). 99.3% of typical patients selected by each hospital have smaller effective diameter than the 32-cm dosimetry phantom. Adult abdomenal SSDE is 17.5 ± 8.8 mGy (1.9-58 mGy). The SSDE seems to decrease as the effective diameter increases as the ATCM turns off, and independent with the effective diameter as the ATCM turns on.
Conclusion: The SSDE for typical patients in Taiwan was investigated. We continue to complete this investigation in 2015 to include more valid data to establish SSDE reference level in Taiwan.
Funding Support, Disclosures, and Conflict of Interest: This study was financially supported by the Atomic Energy Council in Taiwan.
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