Synopsis

Keywords: Body: Breast, Contrast mechanisms: Diffusion, Cross-organ: Cancer

Breast magnetic resonance imaging (bMRI) plays a central role in breast cancer diagnosis and management. Diffusion weighted imaging (DWI) is a helpful additional tool for the characterization of bMRI enhancing lesions. Apparent diffusion coefficient (ADC) values vary depending on the lesion type, benign or malignant, and the information on ADC can aid in the differential diagnosis. Benign lesions typically present with a high ADC. Thus, the measurement of high ADC values in a lesion can safely rule out malignancy. ADC values also correlate with cancer aggressiveness, with more aggressive cancers presenting with lower ADC value.

Breast magnetic resonance imaging (bMRI) plays a central role in breast cancer diagnosis and management. In the early years, bMRI was described as non-specific, due to the difficulties in characterizing enhancing findings. The development of structured reporting and lesion classification systems (Breast Imaging Reporting and Data System- BIRADS and the Kaiser Score), determined a significant improvement in lesion classification and allowed to achieve a high specifity. Diffusion weighted imaging (DWI) was not included in the standard bMRI protocol in the last BI-RADS edition, but it will be mentioned in the upcoming VI edition. Increasing evidence proved the usefulness of the Apparent Diffusion Coefficient (ADC) as additional tool for enhancing lesions characterization. Various methods have been suggested on how to measure ADC: include the whole lesion, use a volume or a region of interest, use single or multiple small regions of interest. Studies comparing different methods confirmed that the use of a single small region of interest in the enhancing area of the lesion with the higher diffusion hindrance is sufficiently reliable. ADC is particularly helpful in the identification of benign findings, and many authors suggested the use of the cutoff 1.5 mm2/s x 10-3 with this aim. Lesions with ADC values above this cutoff can be safely considered benign. Only few cancers can present with higher ADC values, and they can be suspected thorough typical imaging features, thus avoiding false negatives in clinical practice. ADC values also correlate with cancer aggressiveness, with more aggressive cancers presenting with lower ADC. High b-value images can be used for lesion detection, but this application is often limited by image quality and false positive findings.

Acknowledgements

No acknowledgement found.