1. Department of Gastrointestinal Tract Surgery, Fukushima Medical University School of Medicine, Fukushima City, Fukushima, Japan
2. Department of Neurosurgery, Fukushima Medical University School of Medicine, Fukushima City, Fukushima, Japan
3. Department of Radiation Health Management, Fukushima Medical University School of Medicine, Fukushima City, Fukushima, Japan