Value of normalized apparent diffusion coefficients in differentiating between borderline and malignant epithelial ovarian tumors

Purpose: To compare the diagnostic performance of normalized apparent diffusion coefficients (nADCs) of different references with that of ADCs at differentb factors in differentiating borderline epithelial ovarian tumors (BEOTs) from malignant epithelial ovarian tumors (MEOTs). Method: This retrospective study included 53 BEOTs and 148 MEOTs. Conventional magnetic resonance and diffusion-weighted imaging withb factors of 800 and 1000s/mm(2) were performed. ADC was measured three times at solid components of tumors, gluteus maximus muscle (GMM), iliopsoas muscle (IM) and urine and then averaged. ADC(tumor), nADCs were then obtained. Differences and the diagnostic performance of ADC(tumor) and nADCs between BEOTs and MEOTs with different b factors were compared. Results: ADC(tumor), nADCs regardless of b factors were significantly higher in BEOTs than MEOTs. The diagnostic performance of nADC(urine) regardless of b factors was significantly larger than that of nADC(GMM) and nADC(IM). There was no significant difference in the diagnostic performance between ADC(tumor) and nADC(urine) regardless of b factors. A significantly lower ADC(tumor) and a larger diagnostic performance for ADC(tumor) was found with a b factor of 1000s/mm(2) than 800 s/mm(2). There were no significant differences in nADC(urine) of BEOTs or MEOTs or in the diagnostic performance of nADC(urine) with b factors between 800 and 1000s/mm(2). Conclusions: ADC(tumor) and nADCs were both capable of differentiating BEOTs from MEOTs. nADC(urine) was the best of all nADCs and was superior to ADC(tumor) because of its stable performance in differentiating BEOTs from MEOTs, regardless of b factors.