Usefulness of thermoluminescent sheet for measurement of dose distribution near radioactive sources

摘要

A thermoluminescent sheet (TL sheet) for in vivo measurement of spatial dose distribution near small radioactive sources (mm) and its digital readout system have been developed. The TL sheet, the size of which is 40cm×50cm×0.2mm, is a teflon homogeneously mixed with BaSO{sub}4:Eu doped powder of about 5μm. This thin TL sheet is very flexible and can be cut to the desired size and form. The sheet was insensitivity to room-light, so it is easy to handle. The sheet was found to have a linear response with a very wide dynamic range from at least 0.002cGy to 5000cGy absorbed dose. The spatial resolution of the TL sheet was 62μm corresponding to 8.1 line pairs/mm. These are suitable to measure the in vivo spatial dose distribution near sources because large dose gradients exist over small area. For intracavitary radiation therapy of a rectal cancer, the in vivo dose distribution on the surface of the cancer war determined with the TL sheet. This TL sheet may provide a convenient means of measuring the dose distribution of various patterns in radiation therapies.