Average absorbed breast dose (2ABD): an easy radiation dose index for digital breast tomosynthesis

Abstract

Background: To propose a practical and simple method to individually evaluate the average absorbed dose for digital breast tomosynthesis. Methods: The method is based on the estimate of incident air kerma (k a,i) on the breast surface. An analytical model was developed to calculate the k a,i from the tube voltage, tube load, breast thickness, x-ray tube yield, and anode-filter combination. A homogeneous phantom was employed to simulate the breast in experimental measurements and to assess the dose-depth relationship. The k a,i values were employed to calculate the "average absorbed breast dose" (2ABD) index. Four mammographic units were used to develop and test our method under many conditions close to clinical settings. The average glandular dose (AGD) calculated following the method described by Dance et al., and the 2ABD computed through our method (i.e., from the exposure parameters) were compared in a number of conditions. Results: A good agreement was obtained between the k a,i computed through our model and that measured under different clinical conditions: discrepancies < 6% were found in all conditions. 2ABD matches with a good accuracy the AGD for a 100% glandular-breast: the minimum, maximum, and mean differences were < 0.1%, 7%, and 2.4%, respectively; the discrepancies increase with decreasing breast glandularity. Conclusions: The proposed model, based on only few exposure parameters, represents a simple way to individually calculate an index, 2ABD, which can be interpreted as the average absorbed dose in a homogeneous phantom, approximating a 100% glandular breast. The method could be easily implemented in any mammographic device performing DBT.

Average Absorbed Breast Dose (2ABD) to Mean Glandular Dose (MGD) Conversion Function for Digital Breast Tomosynthesis: A New Approach

“…Recently a new dose index for DM and DBT procedures, named 2ABD, has been presented and 14,15 described . 2ABD allows the calculation of the value of the average breast dose in a simple way: it is easily computed for each anode/filter combination starting from the knowledge of tube voltage kVp, tube load mAs, breast thickness T, focus-to-surface distance FSD and tube yield Y .…”

“…kVp, mAs and T are tb characteristics of each DM or DBT exam and can be easily found in the DICOM header; FSD is a specific ( a n d w e l l k n o w n ) c h a r a c t e r i s t i c o f t h e mammographic device and, finally, Y can be tb measured once a time and periodically verified for all the employed devices. A complete description of the method is out of the scope of the present work 14,15 and can be found in the previous publications for both DM and DBT modalities.…”

“…The experimental-based 2ABD method was developed in a homogeneous phantom, with 2ABD representing the mean absorbed dose in a homogenous phantom. 15 In the above-mentioned preliminary study, it was found that the used phantom represented a good approximation of a homogenous breast whose glandularity was 1 (100% of tissue is glandular). Specifically, 2ABD matched MGD within an Dance accuracy of ~ 6 % for a phantom whose thickness was T=3 cm.…”

“…In this work, another method for evaluating the mean glandular dose absorbed by the patient's breast during the DBT examinations was presented. In 14,15 previous works , a simple approach based on experimental measurements has been introduced to individually evaluate the average absorbed dose in DM and DBT procedures. This method is based on the evaluation of a new dosimetric index, named 2ABD (Eq.…”

“…Digital Mammography (DM) is the main X-ray technique used to detect breast masses and microcalcifications. Technological advancements have highly improved the DM technique over the years and today the best upgrade is represented by the Digital Breast Recently a similar dosimetric index (Average Absorbed Breast Dose, 2ABD), based on experimental phantom measurements, has been described, which calculates the average absorbed [13][14][15] breast dose in DM or DBT procedures.…”