Objectives: To evaluate the effect of the choice of b values and prior use of contrast medium on apparent diffusion coefficients (ADCs) of breast lesions derived from diffusion-weighted imaging (DWI), and on the discrimination between benign and malignant lesions.
Methods: A literature search of relevant DWI studies was performed. The accuracy of DWI to characterize lesions by using b value ≤600 s/mm(2) and b value >600 s/mm(2) was presented as pooled sensitivity and specificity, and the ADC was calculated for both groups. Lesions were pooled as pre- or post-contrast DWI.
Results: Of 198 articles, 26 met the inclusion criteria. Median ADCs were significantly higher (13.2-35.1 %, p < 0.001) for the group of b values ≤600 s/mm(2) compared to >600 s/mm(2). The sensitivity in both groups was similar (91 % and 89 %, p = 0.495) as well as the specificity (75 % and 84 %, p = 0.237). Contrast medium had no significant effects on the ADCs (p ≥ 0.08). The differentiation between benign and malignant lesions was optimal (58.4 %) for the combination of b = 0 and 1,000 s/mm(2).
Conclusions: The wide variety of b value combinations applied in different studies significantly affects the ADC of breast lesions and confounds quantitative DWI. If only a couple of b values are used, those of b = 0 and 1,000 s/mm(2) are recommended for the best improvement of differentiating between benign and malignant lesions.
Key points: • The choice of b values significantly affects the ADC of breast lesions. • Sensitivity and specificity are not affected by the choice of b values. • b values 0 and 1,000 s/mm (2) are recommended for optimal differentiation between benign and malignant lesions. • Contrast medium prior to DWI does not significantly affect the ADC.