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TU-F-18C-06: Which Women Based On Clinical Benefits and Dose Should Be Considered For Breast Screening with Tomosynthesis?

PURPOSE
To consider, on a patient specific basis according to volumetric breast density (VBD) the mean glandular dose (MGD) imparted by mammography and tomosynthesis so as to determine which women might benefit from tomosynthesis in consideration with the clinical benefits.


METHODS
For a set of 23 Hologic combo-mode images, MGD was calculated for the tomosynthesis and mammogram acquisitions, with glandularity derived from a personalised measure of VBD. The doses for each acquisition type were compared as a function of VBD, and correlated with breast thickness.


RESULTS
For dense breasts - precisely, those with a Volpara Density Grade (VDG) (analogous to BI-RADS) of 3 and 4 - the MGDs were approximately equal for both tomosynthesis and mammography. However, for low density breasts - those with a VDG of 1 and 2 - the MGD was significantly greater in the tomosynthesis examination than for the mammogram. The compressed breast thickness was generally greater for the lower density (VDG 1 and 2) breasts, than for higher density (VDG 3 and 4) breasts.


CONCLUSION
In breasts of low VBD, examination by mammography offers a lower patient specific MGD than tomosynthesis, sometimes substantially. In breasts of high VBD, the MGD values are approximately equal. The lower MGD is likely due to the increased compressed breast thickness observed in the low density cases. This causes such images to be acquired at a higher MGD in tomosynthesis in order to obtain a satisfactory contrast-to-noise ratio. This results from fundamental differences in the characteristics of the function relating contrast-to-noise ratio to dose between the techniques. Since the possibility of lesion masking arising from tissue superposition is limited in low density breasts, clinicians need to consider the diagnostic benefits versus the apparent increased dose in fatty breasts, which will remain even if the 2D component is stopped. Volpara Solutions Ltd market software for measuring volumetric breast density (Volpara Density), and measuring personalised mean glandular dose (Volpara Dose).