A novel internal radiation therapy (IRT) mode intended for controlled local delivery of (188)Re-Tin colloid was developed by using chitosan-based thermosensitive hydrogel. Chitosan (C) and beta-glycerophosphate (beta-GP) were used to prepare the thermosensitive hydrogel (C/GP). The prepared C/GP hydrogel featured a rapid sol-gel transition within 5min after it was brought into an environment of 37 degrees C. (188)Re-Tin colloid was prepared with labeling efficiency of 93.9+/-0.6%, and could be increased to more than 98% following centrifugation. The average particle size of (188)Re-Tin colloid was 12.1+/-1.2microm, with only 7.2+/-1.5% less than 1microm. Scintigraphic study showed that (188)Re-Tin colloid contained in the C/GP hydrogel was localized (>91%) around the injection site for up to 48h post injection, verifying the intended function of the IRT design. The developed novel form of IRT in this study could be an effective treatment mode for regional radiotherapy.