1. Department of Oral and Maxillofacial Radiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700‑8558, Japan
2. Department of Radiological Technology, Graduate School of Health Sciences, Okayama University, Okayama 700‑8558, Japan
3. Department of Proton Beam Therapy, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Science, Okayama 700‑8558, Japan
4. Department of Radiology, Okayama University Hospital, Okayama 700‑8558, Japan
5. Department of Radiology, Kagawa Prefectural Central Hospital, Takamatsu, Kagawa 760‑8557, Japan
6. Department of Radiology, Iwakuni Clinical Center, Iwakuni, Yamaguchi 740‑8510, Japan
7. Department of Radiology, Tsuyama Chuo Hospital, Okayama 708‑0841, Japan
8. Department of Radiology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama 700‑8558, Japan