Auto-evaluation of skull radiograph accuracy using unsupervised anomaly detection

Article type: Research Article

Authors: Watanabe, Haruyuki^{a; *} | Ezawa, Yuina^a | Matsuyama, Eri^b | Kondo, Yohan^c | Hayashi, Norio^a | Maruyama, Sho^a | Ogura, Toshihiro^a | Shimosegawa, Masayuki^a

Affiliations: [a] School of Radiological Technology, Gunma Prefectural College of Health Sciences, Maebashi, Japan | [b] Faculty of Informatics, The University of Fukuchiyama, Fukuchiyama, Japan | [c] Graduate School of Health Sciences, Niigata University, Niigata, Japan

Correspondence: [*] Corresponding author: Haruyuki Watanabe, School of Radiological Technology, Gunma Prefectural College of Health Sciences, 323-1 Kamioki-machi, Maebashi, Gunma, Japan. Tel.: +81272351211; Fax: +81272352501; E-mail: hal-watanabe@gchs.ac.jp.

Abstract: BACKGROUND:Radiography plays an important role in medical care, and accurate positioning is essential for providing optimal quality images. Radiographs with insufficient diagnostic value are rejected, and retakes are required. However, determining the suitability of retaking radiographs is a qualitative evaluation. OBJECTIVE:To evaluate skull radiograph accuracy automatically using an unsupervised learning-based autoencoder (AE) and a variational autoencoder (VAE). In this study, we eliminated visual qualitative evaluation and used unsupervised learning to identify skull radiography retakes from the quantitative evaluation. METHODS:Five skull phantoms were imaged on radiographs, and 1,680 images were acquired. These images correspond to two categories: normal images captured at appropriate positions and images captured at inappropriate positions. This study verified the discriminatory ability of skull radiographs using anomaly detection methods. RESULTS:The areas under the curves for AE and VAE were 0.7060 and 0.6707, respectively, in receiver operating characteristic analysis. Our proposed method showed a higher discrimination ability than those of previous studies which had an accuracy of 52%. CONCLUSIONS:Our findings suggest that the proposed method has high classification accuracy in determining the suitability of retaking skull radiographs. Automation of optimal image consideration, whether or not to retake radiographs, contributes to improving operational efficiency in busy X-ray imaging operations.

Keywords: Anomaly detection, unsupervised learning, autoencoder, variational autoencoder, skull radiograph

DOI: 10.3233/XST-230431

Journal: Journal of X-Ray Science and Technology, vol. 32, no. 4, pp. 1151-1162, 2024