Utility of Real-time Virtual Sonography (RVS), anew breast imaging method for coordinating sonography with an MRIusing an image fusion technique

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We have developed real-time virtual sonography (RVS), a method for coordinating sonography with an MRI system using an image fusion technique. Since 2005, we have applied this method to sonographic evaluation of MRI-detected lesions of the breast. We reported previously that in 2009, 98% of MRI enhanced index mass and 83% of MRI-detected lesions were identified using RVS (Nakano, et al. Jpn J Clinic Oncol 2009). The aims of this study were (1) to evaluate the targeting accuracy of RVS in sonographic identification of enhancing lesions detected by breast MRI, and (2) to verify the utility of second-look sonography using RVS. (1) We analyzed the positioning error, i.e., the distance from the actual sonographic position to the expected MRI position, in three dimensions. The meanpositioning errors for the transverse and sagittal planes and the depth from the skin were 7.7, 6.9, and 2.8 mm, respectively. The overall mean three-dimensional positioning error was 12.0 mm (Nakano, et al. Ultrasound Med Biol 2012). (2) We analyzed the correlations between lesion detection rates on second-look sonography using conventional B-mode or RVS. Among 67 lesions (24 malignant and 43 benign), the detection rate of conventional B-mode was 27% (18/67); RVS increased these rates signi〓cantly, to 90 % (60/67) (p <0.001) (Nakano, et al. Breast Cancer Res Treat 2012). Our results suggest that RVS has good targeting accuracy in a direct comparison of a sonographic image with MRI results, and the additional use of RVS on second-look sonography signi〓cantly increases the sonographic detection rate of MRI-detected lesions without operator dependence. Webelieve that RVS represents a promising new modality for breast imaging.