Computed diffusion-weighted imaging for differentiating decidualized endometrioma from ovarian cancer

•Decidualized endometrioma (DE) during pregnancy may mimic ovarian cancer (OC).•DE showed high signal intensity on DWI (b = 800) due to T2 shine-through effect.•The ADC value of DE was significantly higher than that of OC.•DE showed signal decrease on computed DWI (b = 1500), whereas OC did not.•Computed DWI can distinguish DE from OC by visual evaluation.

PurposeTo evaluate the clinical diagnostic ability of computed diffusion-weighted imaging (DWI) for differentiating decidualized endometrioma from ovarian cancer.Materials and methodsComputed DWI technique was retrospectively applied to 20 mural nodules in 9 decidualized endometriomas during pregnancy and 20 ovarian cancers. Signal intensities on measured DWI with b values of 800 s/mm2 (DWI800) and on computed DWI with b values of 1500 s/mm2 (cDWI1500) were visually evaluated.ResultsMural nodules of all decidualized endometriomas showed high signal intensity on DWI800 with significantly higher ADC (2.01 ± 0.26 × 10−3 mm2/s) and low signal intensity on cDWI1500, whereas solid components of all ovarian cancers showed high signal intensity on both DWI800 with lower ADC (1.08 ± 0.20 × 10−3 mm2/s) and on cDWI1500.ConclusionMural nodules in decidualized endometriomas may show high signal intensity on DWI800 due to T2 shine-through effect, and cDWI1500 can distinguish decidualized endometriomas from ovarian cancers by visual evaluation.