Average glandular dose in paired digital mammography and digital breast tomosynthesis acquisitions in a population based screening program: effects of measuring breast density, air kerma and beam quality

Abstract

The main purpose was to compare average glandular dose (AGD) for same-compression digital mammography (DM) and digital breast tomosynthesis (DBT) acquisitions in a population based screening program, with and without breast density stratification, as determined by automatically calculated breast density (Quantra). Secondary, to compare AGD estimates based on measured breast density, air kerma and half value layer (HVL) to DICOM metadata based estimates. AGD was estimated for 3819 women participating in the screening trial. All received craniocaudal and mediolateral oblique views of each breasts with paired DM and DBT acquisitions. Exposure parameters were extracted from DICOM metadata. Air kerma and HVL were measured for all beam qualities used to acquire the mammograms. Volumetric breast density was estimated using Quantra. AGD was estimated using the Dance model. AGD reported directly from the DICOM metadata was also assessed. Mean AGD was 1.74 and 2.10 mGy for DM and DBT, respectively. Mean DBT/DM AGD ratio was 1.24. For fatty breasts: mean AGD was 1.74 and 2.27 mGy for DM and DBT, respectively. For dense breasts: mean AGD was 1.73 and 1.79 mGy, for DM and DBT, respectively. For breasts of similar thickness, dense breasts had higher AGD for DM and similar AGD for DBT. The DBT/DM dose ratio was substantially lower for dense compared to fatty breasts (1.08 versus 1.33). The average c-factor was 1.16. Using previously published polynomials to estimate glandularity from thickness underestimated the c-factor by 5.9% on average. Mean AGD error between estimates based on measurements (air kerma and HVL) versus DICOM header data was 3.8%, but for one mammography unit as high as 7.9%. Mean error of using the AGD value reported in the DICOM header was 10.7 and 13.3%, respectively. Thus, measurement of breast density, radiation dose and beam quality can substantially affect AGD estimates.

Classification of fatty and dense breast parenchyma: comparison of automatic volumetric density measurement and radiologists’ classification and their inter-observer variation

“…Both the AGD from DM and DBT were within the limits set in the European Guidelines (238). It was also shown that the AGD from DBT was 33 % higher for women with non-dense breasts and 8 % higher for women with dense breasts (165). Therefore, the increase in AGD for DBT is lower for women with dense breasts.…”

“…Paper III showed that when using DBT, the AGD was about 24 % higher compared to DM, increasing from 1.74 to 2.10 mGy per view on average (165). Both the AGD from DM and DBT were within the limits set in the European Guidelines (238).…”

“…The HVL can also be obtained from the DICOM metadata. But the value reported in the DICOM header showed to have limited accuracy, resulting in an error between 2 and 12 % in the final estimate of AGD compared to measuring HVL (165). We measured HVL for all clinically used beam qualities on all three mammography units used.…”

“…In addition, glandularity refers to the faction of fibroglandular tissue only in the central core of the breast (not the 5 mm thick adipose tissue modelling subcutaneous fat). As the DICOM metadata contain the breast thickness and Quantra TM report the fibroglandular and total volume of the breast, it is possible to convert volumetric density to glandularity using the method described in paper III (165). We chose to include the distal 5 mm semi-circle shell into the core volume, even though this was not included in the original "Dance model" (161).…”

Diagnostic Performance of Digital Breast Tomosynthesis for Breast Suspicious Calcifications From Various Populations: A Comparison With Full-field Digital Mammography

“…Hence, there is no need to worry that the use of this FDA-approved technique would be associated with any harm to the patients [ 35 ]. Osteras et al investigated the average glandular dose in paired FFDM and DBT acquisitions in a population-based screening program (including 3819 women) and found that the mean dose for FFDM, DBT, and Combo was 1.72, 2.09, and 3.81 mGy, respectively [ 36 ]. Our study observed similar results.…”