數位乳房斷層層析攝影劑量之全國性評估

A Nationwide Survey on the Dose of Digital Breast Tomosynthesis

本篇之目的主要評估不同廠牌／型號之數位乳房X光攝影在二維平面（2-dimensional, 2D）模式、數位乳房斷層層析攝影（digital breast tomosynthesis, DBT）模式與複合模式下平均乳腺劑量（average glandular dose, AGD）之表現。本研究使用美國放射學院（American College of Radiology, ACR）認證傳統乳房攝影假體（以下簡稱ACR假體）模擬標準乳房，依據英國、歐洲與國際原子能總署（International Atomic Energy Agency, IAEA）系統方式分別測量2D模式與DBT模式下之臨床曝露條件的入射表面曝露與射束品質，並計算AGD，同時亦評估複合模式下之AGD。實地測量6種機型共28台配有DBT模式之數位式乳房X光攝影儀後發現不同廠牌型號之攝影儀於2D與DBT模式下之劑量表現皆有所不同，整體而言在DBT模式下所有攝影儀針對標準乳房平均之AGD相較2D模式約增加10%（分別為1.53 + 0.30 mGy與1.37 + 0.17mGy）。具有複合模式之攝影儀平均之AGD為2.95 + 0.47 mGy，約為2D模式下之平均AGD的2倍。 The purpose of the study was to evaluate the average glandular dose (AGD) in full field digital mammography (FFDM) with 2-dimensional (2D) mode, digital breast tomosynthesis (DBT) mode, and combo mode from various manufacturers. There were 28 mammography units which contained 6 different models from 4 manufactures in this on-site survey. The methodologies were referred to United Kingdom, European, and International Atomic Energy Agency (IAEA-) protocols developed by Dance and colleagues. The American College of Radiology (ACR) mammography accreditation phantom substituted for the averaged breast was exposed with clinical exposure parameters for 2D and DBT mode, and the incident air kerma and half value layer (HVL) were measured at the corresponded specific beam quality for further average glandular dose calculations. Besides, the AGD in combo mode was also evaluated. The results showed that the AGD varied between manufacturers/models based on the on-site measurements of 28 FFDM with DBT applications from 6 manufacturers. The average AGD of averaged breast from all the units surveyed were 1.37±0.17mGy and 1.53±0.30 mGy for 2D and DBT mode, respectively. The AGD of DBT mode was higher than the one of 2D mode for approximately 10%. For the units equipped with combo mode, the average AGD of combo mode was 2.95±0.47 mGy, which increased patient dose of 2D mode by approximately twofold.