Correlating ultrasound with MRI and tomosynthesis in breast imaging

Abstract

Breast ultrasound performed in conjunction with tomosynthesis and MRI requires close correlation with those studies. Whilst larger mass lesions seen on mammography and MRI may be relatively easy to identify on ultrasound, many suspicious lesions requiring biopsy may have relatively subtle ultrasound findings. This is particularly true of suspicious “non-mass lesions” including architectural distortions, asymmetric densities, and calcifications on mammography, and smaller mass lesions and non-mass enhancement which may be seen on MRI. Ultrasound guided biopsy is often more readily available, less costly, easier to perform, and more comfortable for women undergoing biopsy than mammographic and MRI guided biopsy. Ultrasound visualisation of a lesion requiring biopsy is advantageous for these reasons. “Probable benign” mammographic and MRI lesions which undergo normal or benign ultrasound assessment may have delayed cancer diagnosis if a subtle abnormal ultrasound finding indicating a cancer has been missed at ultrasound assessment. Understanding factors such as breast positioning differences in MRI, mammography and ultrasound, as well as the influence that breast size and density may have on estimating lesion position is critical for breast sonographers. Also critical in identifying subtle lesions, is an appreciation of subtle ultrasound findings such as focal breast textural change, focal or segmental ductal thickening, and calcifications. Optimising scan technique to identify these subtle changes is discussed. Essential factors in correlation include: 1. Review of tomography/mammographic/MRI images PRIOR to performing ultrasound to enable an appropriate target area for ultrasound search. 2. Knowledge of lesion characteristics being searched, including lesion size, margin characteristics, relationship with adjacent tissue (eg intraductal lesion or calcification, poorly marginated mass, converging distortion, multifocal distortion). 3.Knowledge of scan techniques which may assist in search, including survey scanning using a wide field of view, appropriate use of focal zones, optimising gain, and use of other assisting features such as harmonic imaging, trying varied machine presets, colour flow, and varying compression. Reduced compression may allow enhanced visualisation of some ductal lesions and calcifications, and scanning in a grid like “to and fro” pattern may allow you to see a focal converging distortion not evident on a “single pass” through an area. In summary, you have to know where you are looking, what you are expecting to see, and how you can best find it.