ACR BI-RADS is a quality assurance system designed to standardize reporting and reduce confusion in breast imaging interpretations and management recommendations. It mainly consists of dynamic contrast enhanced (DCE)-MRI. Evaluation of morphology and kinetics using DCE-MRI is recommended to differentiate malignant from benign tumors. For diffusion weighted imaging (DWI), the growing evidence of the improvement in specificity using DWI is shown in BI-RADS; however, the techniques remain in the research realm. Category classification based on morphology and kinetics can be complicated. Meanwhile, assessment using DWI would be less complicated.

There are three advantages of DWI: visibility, short scanning time and quantitative capability. Quantitative apparent diffusion coefficient (ADC) obtained from DWI is useful not only to differentiate benign and malignant tumors but also to grade malignant tumors according to their prognostic factors. The contents of this presentation are

1. DWI for differentiation between benign and malignant tumors

2. DWI for grading breast cancers

3. Problems of DWI and future investigation

For discriminating malignant from benign, several reports have shown that the specificity was significantly improved and unnecessary biopsy could be avoided with DWI. False positive tumors were reported to include fibroadenoma, fibrocystic change, papilloma and high risk lesions (atypical ductal hyperplasia (ADH), flat epithelial atypia (FEA), lobular carcinoma in situ (LCIS)). False negative tumors were reported to include some types of invasive ductal carcinoma (IDC), ductal carcinoma in situ (DCIS), invasive lobular carcinoma (ILC), and mucinous carcinoma.

For tumors diagnosed as breast carcinoma, DWI might be useful for grading the prognostic factors.

2-1 DWI for differentiating DCIS and IDC

2-2 DWI for predicting the cell proliferation level

2-3 DWI for differentiating types of mucinous carcinoma

2-4 DWI for the evaluation of neoadjuvant chemotherapy

Despite these advantages, there are several problems with DWI.

3-1 Methods to calculate ADC and reproducibility of results

3-2 Standardization of ADC in different MR systems

3-3 Problems associated with echo-planner imaging (EPI)-DWI including distortion, chemical shift and susceptibility artifact

There are already several established advantages of using DWI to diagnose breast cancer. Standardization and improvement of technology should be made to expand the clinical application of DWI in the future.