Research on glandular dose level of mammography in China

Objective: To analyze the distribution of compressed breast thickness (CBT) and dose level of average glandular dose(AGD) by the investigation of exposure parameters of mammography and measurement of AGD in different levels of hospitals in 15 provinces of China, and provide basis to establish a suitable diagnostic reference level(DRL) of mammography for adult female in China. Methods: According to the requirements of the 'Research on Radiation Hazard Evaluation and Control Technology of Medical Radiation^, we investigated the age, the CBT, the exposure parameters and the position of clinical mammography cases. The incident air kerma(K_a,i) was measured by manual exposure according to the exposure records, and AGD was calculated using the method of EC guideline. Results: A total of 4, 372 mammograms and 273 different types of mammography equipment s were investigated in 149 hospitals in 15 provinces of China, including screen-film mammography, computed radiography for mammography and digital mammography. For the three types of equipment, the mean value of AGD of craniocaudal(CC) position was 1.21, 1.77, 1.61 mGy, and 75th percentile of the AGD was 1.36, 2.22, 1.81 mGy, respectively; the mean value of AGD of mediolateral oblique (MLO) position was 1.02, 1.78, 1.66 mGy, and 75th percentile of the ACD was 1.23, 2.46, 1.81 mGy, respectively. The median of CBT for CC and MLO was 4.2 and 4.5 cm respectively. Conclusion: The AGD of SFM is the lowest among different types of mammography equipment, followed by mammary DRM. The AGD of mammary gland CRM is higher than SFM and DRM. (authors)