1. Software College, Northeastern University, Shenyang 110169, China
2. Key Laboratory of Intelligent Computing in
Biomedical Image, Ministry of Education, Northeastern University, Shenyang 110169, China
3. Department of Nuclear
Medicine, The First Affiliated Hospital of China Medical University, Shenyang 110001, China
4. Computer Science
Division, The University of Aizu, Aizu-Wakamatsu, Fukushima 965-8580, Japan