More than 20 years after the advent of balloon angioplasty restenosis remains a major health risk and cost burden. Success in animal trials and treatments in other non-malignant lesions using radiotherapy has established a new branch of medical science, intravascular brachytherapy (IVB) in treating restenosis. In just over 6 years since the first application, there are today more than 500,000 operations a year in USA alone. Successful treatment will depend critically on the delivery of proper radiation dosage to the vascular site. Radioactive strength and uniformity of the IVB sources used are of primary concern. This program takes a sensitive, well proven radiation detection technology and couples it to an innovative imaging approach for the characterization of IVB line/seed-train sources. The end product is a fast, accurate and low-cost 3-D imaging systems for the profiling of IVB line sources. A 2-D system will be tested in Phase I for both gamma and ¿ IVB sources. The results will be used for the design of a 3-D system to be constructed in Phase II.