Development of a phantom to test fully automated breast density software – A work in progress

Radiation exposure and screening yield by digital breast tomosynthesis compared to mammography: results of the TOSYMA Trial breast density related

OBJECTIVES

The randomized TOmosynthesis plus SYnthesized MAmmography (TOSYMA) screening trial has shown that digital breast tomosynthesis plus synthesized mammography (DBT + SM) is superior to digital mammography (DM) in invasive breast cancer detection varying with breast density. On the other hand, the overall average glandular dose (AGD) of DBT is higher than that of DM. Comparing the DBT + SM and DM trial arm, we analyzed here the mean AGD and their determinants per breast density category and related them to the respective invasive cancer detection rates (iCDR).

METHODS

TOSYMA screened 99,689 women aged 50 to 69 years. Compression force, resulting breast thickness, the calculated AGD obtained from each mammography device, and previously published iCDR were used for comparisons across breast density categories in the two trial arms.

RESULTS

There were 196,622 exposures of 49,227 women (DBT + SM) and 197,037 exposures of 49,132 women (DM) available for analyses. Mean breast thicknesses declined from breast density category A (fatty) to D (extremely dense) in both trial arms. However, while the mean AGD in the DBT + SM arm declined concomitantly from category A (2.41 mGy) to D (1.89 mGy), it remained almost unchanged in the DM arm (1.46 and 1.51 mGy, respectively). In relative terms, the AGD elevation in the DBT + SM arm (64.4% (A), by 44.5% (B), 27.8% (C), and 26.0% (D)) was lowest in dense breasts where, however, the highest iCDR were observed.

CONCLUSION

Women with dense breasts may specifically benefit from DBT + SM screening as high cancer detection is achieved with only moderate AGD elevations.

CLINICAL RELEVANCE STATEMENT

TOSYMA suggests a favorable constellation for screening with digital breast tomosynthesis plus synthesized mammography (DBT + SM) in dense breasts when weighing average glandular dose elevation against raised invasive breast cancer detection rates. There is potential for density-, i.e., risk-adapted population-wide breast cancer screening with DBT + SM.

KEY POINTS

Breast thickness declines with visually increasing density in digital mammography (DM) and digital breast tomosynthesis (DBT). Average glandular doses of DBT decrease with increasing density; digital mammography shows lower and more constant values. With the smallest average glandular dose difference in dense breasts, DBT plus SM had the highest difference in invasive breast cancer detection rates.

Mechanical standardisation of mammographic compression using Volpara software

INTRODUCTION

Although breast compression is required in routine mammographic practices, current subjective protocols enforcing 'breast tautness' have minimal clinical reproducibility. Whilst objective guidelines of target force (daN) do not consider breast volumes, new measures of pressure (kPa) account for associated variations. The study aims to determine characteristic compressive forces applied at an Australian diagnostic breast clinic, thereby establishing performance success in achieving ideal pressures of 10 kPa.

METHODS

Parameters of 1972 mammograms were analysed retrospectively from a South Australian diagnostic breast clinic. Raw data were processed using VolparaDensity software; applied compression (force/pressure), breast thickness, breast volume, breast density and average glandular dose estimates were investigated based on breast/paddle contact areas.

RESULTS

Distributions of applied average forces is large, yet distributions of applied average pressures are larger; this is internationally comparable. Regarding force-compressions, 98.6% are >5 daN, 16.6% are >10 daN, and 0.0% are >15 daN. Regarding pressure-compressions, 94.5% are >5 kPa, 36.0% are >10 kPa, and 6.3% are >15 kPa. Measures of average breast thickness, volume and density show anatomically consistent trends, with average glandular dose values constant, albeit high.

CONCLUSIONS

There was a high level of variation of applied compression forces in relation to breast/paddle contact area and an even higher variation in applied pressure. This is comparable with existing literature. Real-time compression pressure standardisation may benefit examination consistency. The relationship between breast volume, contact area, compression force and resultant compression pressure may aid in developing an objective compression protocol for clinical practice.

IMPLICATIONS FOR PRACTICE

Practical guidelines may increase the reproducibility of image acquisition, whilst optimizing patient discomfort and additional radiation dose from image repeats. Patient compliance may increase in accordance with perceived advantages of mechanical standardisation, ultimately aiding in the detection of early-stage breast cancer.