Response.

Abstract

I thank to the authors for their interest in our study.1 Our study documented that in spite of the lower diagnostic accuracy of diffusion-weighted imaging (DWI) in nonmass enhancements (NMEs), it is effective in the characterization of both mass and NME-type breast lesions. The results are encouraging for the use of DWI in the characterization of both mass and nonmass-type lesions. DWI seems very easy to apply and provides useful information for the characterization of breast tumors. However, technical and protocol differences—mainly the selected b-values—in scanning, together with differences in the evaluation of images and measurement of apparent diffusion coefficient (ADC) values—mainly the use of average or minimum ADC—causes great variations between ADCs obtained in different studies. In our study for DWI we used b-values of 50, 400, and 1000 s/mm2 and analyzed the minimum ADCs. Of course, the chosen b-value combination affects the obtained ADCs. Our preference of 50 s/mm2 as the minimum b instead of 0 s/mm2 is probably one of the reasons for the relatively lower ADC values obtained in the study when compared with the literature. However, might it be the only factor? How much is the effect of chosen minimum b on ADC? Nilsen et al2 in their study of 24 women with breast cancer found a 5% decrease in mean ADCs when b-values of 50, 800 s/mm2 were used instead of 0, 800 s/mm2. According to the analysis of our unpublished data of 125 suspicious lesions, the ADC decreases by 2% when b-values of 50, 400, 1000 s/mm2 are used instead of 0, 50, 400, 1000 s/mm2. Although not well known, the ADC measurement technique also affects the obtained ADCs. Breast tumors are neither pathologically nor radiologically homogenous. In our study1 we preferred to use the minimum ADC because ADC values inversely correlated with tumor cellularity and high cellularity is one of the main features of malignant tissue. The minimum ADC might be reflecting the tumor site with the most malignant potential. Hirano et al3 in their study of 75 cases found that the diagnostic efficacy of minimum ADC was superior to that of average ADC and mean ADC decreased nearly 17% when minimum ADC instead of average ADC was used. The scientific data are insufficient, but according to what we have the ADC measurement technique—the preference of minimum ADC instead of average ADC—seems to be the more important of the two reasons for the relatively lower ADC values obtained in our study.1