[DEVELOPMENTS IN BREAST IMAGING].

Breast cancer is the most frequent cancer in Japanese women. As breast density increases, the detection rate of breast cancer by mammography (MMG) decreases. Breast density notification laws have been enacted in several states in the USA. Supplemental screening tools for women with dense breasts are needed. The results of a large randomized trial to compare the sensitivity, specificity, and cancer detection rate of MMG and adjunctive ultrasonography (US) to screen for breast cancer in Japan (J-START) were reported last year. More than 70,000 women aged 40 to 49 years were enrolled. The sensitivity and cancer detection rate were significantly higher in the MMG+US group than in the MMG-alone group. Automated breast ultrasonography is a tool to overcome the operator dependency of hand-held US and low reproducibility. Digital breast tomosynthesis, referred to as 3D MMG, offers higher sensitivity and specificity than MMG. Contrast-enhanced spectral MMG is an MMG scan using contrast medium to detect breast cancer more clearly even in dense breasts. It is often used for women at high risk for cancer and substituted for magnetic resonance imaging. A dedicated breast positron-emission tomography (PET) system has been available in Japan with insurance coverage since 2013. More cases of cancer were detected using breast PET than whole-body PET. Additional studies including mortality rates are needed.