No abstract

Calcium fluoride (Mn) Teflon thermoluminescent dosimetry (TLD) has been used for dosimetric studies of the fast neutron beam from the MRC Cyclotron. The very small intrinsic sensitivity of this phosphor to fast neutrons makes it suitable for investigating the gamma contribution in the field. The percentage of dose due to y-rays was found to be 5yo, in reasonable agreement with a measurement of 3% using photographic film. Exposures in pairs, one in a hydrogenous surround (polythene), the other in lead, enable the gamma and neutron components to be memured separately. This method has been applied to depth dose studies in tissue-equivalent phantoms.The dosemeters were discs 0.13 x 6.0 mm and the read-out instrument used was Conrad Type 5100. Reproducibility of 376 has been obtained using a controlled calibration and annealing technique. The angular response severely limits its application in clinical use.

CaS0,:Tm phosphor TLD has been used, mixed with glucose, to measure neutron and gamma doses separately. The results of measurements taken on 50 patients undergoing clinical neutron therapy are reported. Comparisons with isodose estimations at entrance and exit points give standard deviations of 8.8 and 17% respectively. An analysis of the errors involved indicates that the energy sensitivity of the system is a problem, but the results obtained are encouraging enough to continue development of a system for measuring doses in the treated volume. -