TUMOR BLOOD-FLOW MEASUREMENTS USING COINCIDENCE COUNTING ON PATIENTS TREATED WITH NEUTRONS

Purpose: The purpose of this work was to measure blood flow in tumors using a coincidence counting technique on patients undergoing treatment with neutrons. Methods and Materials: The half-time, T-w, for the washout of O-15 from neutron-activated tumors was measured with two 10 cm NaI(TI) crystals coupled to a PC-based coincidence counting system, Blood how measurements were made in 33 patients, 19 of whom had cancers of the head and neck region, 6 had breast cancer, 5 had sarcomas, and 3 patients had mesotheliomas. Results: Blood how as indicated by T-w of mobile O-15 formed by neutron activation could be readily determined in tumors of patients undergoing neutron radiotherapy. The general reduction in the value for Tw was noted towards the end of treatment and did not seem to be dependent on the initial tumor volume. There was a tendency for larger lesions to be associated with longer half-times of O-15 washout. Conclusion: It appears possible to obtain a reasonable estimate of tumor blood flow using a simple coincidence counting technique. In view of the large variation in blood flow between tumors, it did not appear to be possible to identify potentially hypoxic tumors that would respond to neutron therapy.