ISSN: 2640-2343
Authors: Olaolu Osunbayo, Patricia Svolos, Ashley Rubinstein and Ching-Mei Feng*
Purpose: To investigate how the displayed average glandular dose (AGD) of Hologic 3Dimensions mammography systems compares to computed AGD, and how this comparison is modulated by breast thickness, and the assumptions in women breast glandularity. Methods: Using 2, 4, 6, and 8 centimeter (cm) of BR-12 (47% glandular / 53% adipose, CIRS, VA, USA), exposures were acquired using the Auto-Filter automatic exposure control (AEC) mode on 13 Hologic 3Dimensions mammography systems. Entrance exposures and half-value-layer (HVL) were measured using solid state detectors, and the displayed entrance skin dose (ESD), displayed AGD, and displayed exposure index (EI) were recorded. The AGD was first computed under the assumption of 50% glandular, 50% adipose tissue composition. It was then computed using the assumption of breast composition for the average woman aged 40-49 years old (100%, 65%, 35% and 14% glandularity for 2, 4-, 6- and 8-cm breast thickness, respectively). The AGD computed using these assumptions was compared to the displayed AGD. Results: Under the assumption of 50% glandularity, the deviation between displayed AGD and computed AGD is statistically significant at 2cm thickness in 2D mode, and at the thicknesses of 4, 6 and 8 cm in 3D mode (p<0.05). Using the assumption of glandularity based on the average woman aged 40-49 years old, the deviation between displayed AGD and computed AGD is statistically significant at the largest thickness of 6 and 8 cm in 2D mode; and also significant at thicknesses 2, 4, and 8 cm in 3D mode. Conclusion: While AGD may not estimate the patient breast’s dose accurately due to uncertainty in the amount and distribution of glandular tissues in the breast, AGD may be useful in the optimization of a mammographic procedure. The knowledge of the displayed AGD performance across different thicknesses may help in the optimizations.
Keywords: Glandularity; Mammography Systems; Hologic 3dimensions; Adipose Tissue
