Chapter 3 - Overview of Breast DWI: Diagnosis of Suspicious Lesions Using DWI in Combination With Standard MRI

Abstract

Breast magnetic resonance imaging (MRI) is the most sensitive test for the detection of breast cancer. The current approach relies on the intravenous injection of gadolinium-based contrast media, which reveals angiogenesis in malignant neoplasms. Usually, the task of detecting cancer is quite simple: any enhancement may represent cancer, and the absence of enhancement largely excludes cancer. The challenge is to distinguish benign from malignant enhancing lesions. While Breast Imaging Reporting and Data System (BI-RADS) provides a common language for this task, BI-RADS morphological and kinetic features in benign and malignant lesions overlap, and subjective interpretation has only a moderate interreader agreement. Confronted with a lack of objective criteria, physicians recommend biopsies to establish a definite diagnosis in a substantial number of benign lesions. As this workup is invasive, associated with physical and psychological harm, costs, and stretching limited resources in biopsy facilities and trained personnel, methods to reduce unnecessary biopsies are required. Diffusion-weighted imaging (DWI) is such a test: ranging from simple to advanced diffusion metrics, it provides the physician with a quantitative, spatially resolved biomarker suggesting objective diagnosis. While DWI can be used to detect cancer as a stand-alone method, its best proven use is the characterization of enhancing lesions on contrast-enhanced breast MRI. As the rate of malignant lesions decreases with increasing apparent diffusion coefficients, a cutoff can potentially be defined to exclude malignancy and avoid unnecessary biopsy. This chapter describes the application of DWI in clinical practice and focuses on the diagnosis of suspicious lesions using DWI in combination with contrast-enhanced images.