1. Department of Radiological Technology, School of Health Sciences, Niigata University, Asahimachi-dori, Chuo-ku, Niigata, Niigata, Japan
2. Department of Medical Radiological Technology, School of Health Sciences, Fukushima Medical University, Sakae-machi, Fukushima, Fukushima, Japan
3. Department of Radiology and Nuclear Medicine, Research Institute for Brain and Blood Vessels-Akita, Senshu-kubota-machi, Akita, Japan