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Patient-Based Average Glandular Dose Estimations in Taiwan

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y hwang

Y.S. Hwang1*, H.Y. Tsai2, H.Y. Chen2, H.W. Wei2, J.H. Lin3, H.L. Liu2, (1) Chang Gung Memorial Hospital, Linkou,Taiwan, (2) Chang Gung University, Taoyuan, Taiwan, (3) Atomic Energy Council, New Taipei, Taiwan

SU-E-I-59 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
The objective of the study was to investigate the average glandular dose (AGD) distributions based on the patients with average-sized breasts in Taiwan.

Methods:
Patient data were collected from 199 mammography units of 167 facilities (76% of the units in Taiwan) during 2012 in Taiwan. For each unit, exposure parameters including target/filter, kVp and tube loadings of 15 patients with average-compressed breast size of 4.2±0.5 cm in craniocaudal (CC) views were recorded by the technologists. Half value layer (HVL) and radiation exposure per mAs were measured at specific beam quality during the annual on-site inspection. Entrance skin exposure for each patient was thus estimated based on the radiation output data, patient exposure techniques and compressed breast thickness. Both the conversion factors calculated by Dance and Wu were used for further AGD calculations for comparisons. Average of the AGDs of the 15 patients may served as the represented mean AGD for each mammographic unit, and dose distributions could also be obtained for further evaluations.

Results:
Based on the conversion factors calculated by Dance, AGDs ranged from 95.8 to 505.7 mrad, and the mean, median and 3rd quartile of the estimated AGD of the 199 mammographic units was 191.9 mrad, 172.2 mrad, and 228.0 mrad, respectively. By calculating AGDs using Wu's conversion factors, AGDs ranged from 73.3 to 390.4 mrad, and the mean, median and 3rd quartile of the estimated AGD of the 199 mammographic units was 156.1 mrad, 143.5 mrad, and 186.2 mrad, respectively. Estimated AGDs using Wu's correction factors got the lower AGD values compared to the AGDs estimated by Dance method.

Conclusion:
AGD distributions based on nationwide represented patient data may serve as a baseline dose database for future diagnostic reference level (DRL) establishment in mammography in Taiwan.

Funding Support, Disclosures, and Conflict of Interest: This work was supported by grants from Atomic Energy Council of Taiwan(AEC10101003L). The authors declare that there are no conflict of interest.

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