INVIVO MEASUREMENT OF SPATIAL DOSE DISTRIBUTION AROUND RADIOACTIVE SOURCES USING A THERMOLUMINESCENT BASO4-EU SHEET

A thermoluminescent (TL) sheet for in vivo measurement of the spatial dose distribution around a radioactive source has been developed. The TL sheet is found to have a linear response with a very wide dynamic r ange from at least 0.002 to 5000 cGy absorbed dose. This TL sheet (40 cm x 50 cm x 200 mum), which is composed of Teflon mixed with BaSO4:Eu doped powder, is very flexible and can be cut to the desired size. In addition, it is easy to handle because of its insensitivity to room l ight. The spatial dose distribution is printed out with a newly develo ped TL sheet digital-readout system. Another high-resolution dosimetry system made by exposing X-ray film with TL photons emitted from the i rradiated TL sheet at constant room temperature has been reported. For a clinical application, the TL sheet is wrapped on an applicator for intracavitary radiation therapy of rectal cancer and is inserted into the rectum. The location of the TL sheet can be confirmed with diagnos tic X-ray film. After irradiation with a high dose-rate Co-60 source, the in vivo dose distribution on the surface of the rectal cancer is d etermined.