Organized Approach to Diagnostic Imaging

Overview

This chapter outlines a systematic approach to the diagnostic evaluation of noncalcified findings identified at screening mammography, including masses and asymmetries. Modalities discussed include mammography, tomosynthesis, and ultrasound.

For asymptomatic patients, the purpose of the diagnostic workup is to further evaluate potential abnormalities identified at screening mammography. Specific objectives include the following: confirmation that a finding is real, lesion localization, and lesion characterization.

Triangulation

Describing the Location of Findings in the Breast

In order to describe the location of a finding in the breast, the convention of the clockface is used. The o’clock position of a finding is based on its position when an observer is facing the patient. For example, a finding in the lateral aspect of the right breast would be at the 9 o’clock position, whereas a lateral lesion in the left breast would be at the 3 o’clock position. In addition to the clockface, it is also important to specify the distance of a finding from the nipple in centimeters. These conventions are also observed when describing clinical breast examination findings such as palpable lumps. These rules facilitate clear and precise communication between radiologists and clinicians.

Triangulation with Two-Dimensional Mammography

Once a finding has been determined to represent a true space-occupying lesion, it needs to be precisely localized in order to facilitate targeted ultrasound as well as biopsy. For findings that are visible on the standard craniocaudal (CC) and mediolateral oblique (MLO) screening views, it is helpful to be able to predict the location on a true lateral projection. As a general rule, lateral lesions will fall and medial lesions will rise as one goes from the MLO to true lateral projection. However, there are exceptions to this rule. A more reliable approach has been described by Sickles, as illustrated in Fig. 13.1 . By lining up the CC and MLO projections, one can predict the location on the mediolateral (ML) view.

Fig. 13.1, Prediction of lesion location on the lateral projection using standard craniocaudal (CC) and mediolateral oblique (MLO) views. (A) Line up views progressing in obliquity from 0 degrees CC to 45 degrees MLO to 90 degrees. Mediolateral (ML) views with the nipples pointing in the same direction and positioned at the same level. Images should be equidistant from each other. (B) Draw a line connecting the lesion on the CC and MLO views, extending the line to the ML view. The lesion will be located along this line on the ML view, at the same distance from the nipple as on the other views ( blue dotted line ).

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