Objective To investigate the correlation of average glandular dose ( AGD) with categories of breast composition and breast compressed thickness in digital breast tomosynthesis ( DBT) , and to compare the average glandular dose between DBT and FFDM .Methods 520 patients received a serial scan of DBT before FFDM under the same pres-sure condition with AEC mode .AGD during DBT was compared among 4 categories of breast composition within the same breast compressed thickness .AGD during DBT and FFDM was also compared under the same pressure condition .Results Of 520 cases, 4 cases were of the fatty type , 96 cases were of the fibroglandular density type , 308 cases were of the het-erogeneously dense type , and 112 cases were of the extremely dense type .With the same thickness , the AGD is highest in the extremely dense type and lowest in the fatty type , during both FFDM and DBT .Under the same pressure condition , AGD was (1.50 ±0.40) mGy in FFDM and (1.66 ±0.24) mGy in DBT (P<0.01).Conclusion AGD rises with breast compression thickness and density in both FFDM and DBT .In the same compression status , AGD of DBT is higher than FFDM.%目的：探讨数字乳腺断层摄影（ DBT）下不同乳腺分型、不同乳腺厚度与腺体剂量之间的关系，并比较DBT与全视野数字乳腺X线摄影（ FFDM）的腺体剂量。方法对520例患者在同一压迫状态下，先进行DBT，再进行FFDM，选用自动曝光模式进行曝光。比较相同厚度水平下，DBT下4种不同乳腺分型的腺体剂量，以及比较同一压迫状态下DBT与FFDM的腺体剂量。结果520例中脂肪型4例，少量腺体型96例，多量腺体型308例，致密型112例；在同一乳腺厚度FFDM及DBT均以致密型乳腺的腺体剂量最高，多量腺体次之，少量腺体型及脂肪型最少。同一压迫状态下FFDM腺体剂量（1.50±0.40）mGy，DBT腺体剂量（1.66±0.24）mGy，差异有统计学意义（P＜0.01）。结论 DBT与FFDM的腺体剂量均随着乳腺厚度及密度的增加而升高，同一压迫状态下DBT腺体剂量大于FFDM。
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