Two Different Methods of Region-of-Interest Placement for Differentiation of Benign and Malignant Breast Lesions by Apparent Diffusion Coefficient Value

Purpose: We aimed to investigate the influence of different methods of region-of-interest (ROI) placement onapparent diffusion coefficient (ADC) values in breast tumours and their accuracy in differentiating benign versusmalignant tumors in mass and nonmass lesions. Methods and Materials: In this prospective study, 79 patients with98 breast lesions, from 2015 until 2017, were investigated by 1.5-T breast MRI. Histopathology evaluation were donefor all malignant lesions and most of the benign ones. ADC values were measured in normal breast tissue and by twoways of ROI placement in the breast lesions (mass and non-mass): 1- ROI covering the whole lesion, 2- ROI in thehighest part (most restricted area) of the lesion in DWI images. The accuracy of these two approaches were compared.Results: The age range was 17-68 years with mean age 43.3 ± 9.9 years. 49% of the lesions were benign and 51% oftumors were malignant. Our results revealed that the measured ADC values in normal breast tissue were higher thanbreast lesions (P≤0.01). Appropriate cut off determination in non-mass was not valid by both methods, but in mass inthe first way was 1.45×10 -³mm²/s and in the most restricted part was 1.16×10-³ mm²/s. ADC values differed significantlybetween the two ways of ROI placement in mass lesions (P<.001). Most restricted part ADC showed the best diagnosticperformance in mass lesions with area under curve 0.88 versus 0.82. Conclusion: ROI placement has significant impacton the meseaured ADC values of breast lesions and ROIs in most restricted parts were more accurate than whole-lesionROIs. Cut-off values differed significantly based on the methods of measurement.