The Use of C150 and 1502 Steady-State Imaging to Monitor Radiation Treatment Effects

Methods for monitoring the response of tumor and normal tissues to radiation therapy are extremely limited. Development of a method for monitoring physiologic parameters of these tissues sensitive enough to provide evidence of tumor regrowth and possibly predicting unacceptable effects upon normal tissues at an early time would be highly desirable. The aim of this preliminary study was to determine if serial C150 and 1502 steady-state images taken before, during and post-radiation therapy would show changes sufficiently large to suggest their application as therapy monitoring methods. A canine with a spontaneous osteosarcoma in the distal tibia was treated with a two week course of cobalt-60 radiotherapy and monitored. The ratio of tumor to contralateral control first increased in both the C150 and 1502 images to 170 and 140%, respectively, and then gradually decreased to 80 and 60% of their initial values by day 39. When venous blood normalized C150 images were subtracted from 1502 images taken on the same day, the decrease at day 39 reached 60%. The large changes observed in this study provides positive evidence that these methods may prove useful as monitors for radiotherapy treatment.