Extraction of metastasis hotspots in a whole-body bone scintigram based on bilateral asymmetry

• Published in: International journal for computer assisted radiology and surgery 2021-12, Vol.16 (12), p.2251-2260
• Main Authors: Saito, Atsushi, Wakabayashi, Hayato, Daisaki, Hiromitsu, Yoshida, Atsushi, Higashiyama, Shigeaki, Kawabe, Joji, Shimizu, Akinobu
• Format: Article
• Language: English
• Subjects: Asymmetry; Computer Imaging; Computer Science; Health Informatics; Imaging; Medical imaging; Medicine; Medicine & Public Health; Metastasis; Original Article; Pattern Recognition and Graphics; Performance evaluation; Radiology; Surgery; Vision
• ISSN: 1861-6410; 1861-6429
• DOI: 10.1007/s11548-021-02488-w

Purpose A hotspot of bone metastatic lesion in a whole-body bone scintigram is often observed as left–right asymmetry. The purpose of this study is to present a network to evaluate bilateral difference of a whole-body bone scintigram, and to subsequently integrate it with our previous network that extracts the hotspot from a pair of anterior and posterior images. Methods Input of the proposed network is a pair of scintigrams that are the original one and the flipped version with respect to body axis. The paired scintigrams are processed by a butterfly-type network (BtrflyNet). Subsequently, the output of the network is combined with the output of another BtrflyNet for a pair of anterior and posterior scintigrams by employing a convolutional layer optimized using training images. Results We evaluated the performance of the combined networks, which comprised two BtrflyNets followed by a convolutional layer for integration, in terms of accuracy of hotspot extraction using 1330 bone scintigrams of 665 patients with prostate cancer. A threefold cross-validation experiment showed that the number of false positive regions was reduced from 4.30 to 2.13 for anterior and 4.71 to 2.62 for posterior scintigrams on average compared with our previous model. Conclusions This study presented a network for hotspot extraction of bone metastatic lesion that evaluates bilateral difference of a whole-body bone scintigram. When combining the network with the previous network that extracts the hotspot from a pair of anterior and posterior scintigrams, the false positives were reduced by nearly half compared to our previous model.