Radiation dose in mammography is low, but the breast is a relatively radio-sensitive organ and when millions of healthy women are being screened annually, it is important to ensure that the dose remains as low as reasonably possible while preserving diagnostic image quality. Unfortunately, the radiation dose estimations provided today by mammography unit manufacturers are not standardized and vary according to the dose algorithm they use and how they handle differing breast densities. As a result, these dose estimations are not comparable. VolparaDose utilizes a globally accepted algorithm and uses the patient’s specific breast density to generate patient-specific radiation dose estimations in a standard manner.
Mean (or Average) Glandular Dose Estimation Today
When an x-ray is taken, energy is absorbed by the breast. That energy has a biological impact depending upon the radio-sensitivity of the breast tissue. Mean glandular dose (MGD) is widely accepted to be the most appropriate measure to predict risk of radiation-induced cancer.
Most mammography manufacturers provide an estimate of MGD which can be displayed on the mammogram when viewing overlays related to the physics parameters used. Unfortunately, these estimates have several flaws:
- Each manufacturer uses its own MGD estimation algorithm (usually one of Wu, Sobol, Boone or Dance)
- Each manufacturer uses a different estimate of volumetric breast density, typically either a set proportion (“30% glandular”) or varying according to compressed breast thickness.
The Volpara Difference
VolparaDoseRT, an add-on module to VolparaDensity, is vendor-neutral and uses volumetric quantitative data to generate a patient-specific assessment of the MGD per image. Research recently presented at American Association of Physicists in Medicine shows that it is possible to improve the accuracy and personalization of radiation dose estimation, which may, in turn, allow for better optimization of radiation dose in breast screening, both in mammography and tomosynthesis.
- Based on one, globally accepted and validated algorithm for all vendors
- Specific to the woman’s volumetric breast density
Separating cases by Volpara Density Grade (VDG) or BI-RADS® reveals how manufacturers make assumptions about the density across all breasts. The figure below shows that for Manufacturer 1, there is a strong correspondence between MGD and VolparaDose in VDG 1, but divergence in VDG 4; conversely, Manufacturer 2 shows a strong correspondence between MGD and VolparaDose in VDG 4, but divergence in VDG 1.