MEASUREMENT OF RADIAL DOSE DISTRIBUTIONS AROUND SMALL BETA-PARTICLE EMITTERS USING HIGH-RESOLUTION RADIOCHROMIC FOIL DOSIMETRY

A method is described for the direct measurement of the radial dose di stributions around small (from several mm down to tens of mum in diame ter) beta particle emitters. The method employs the high resolution re adout of radiochromic dye foils. These foils form a blue image upon ir radiation and require no processing to stabilise the image. The colour change (in units of absorbance) is nearly linear with absorbed dose o ver a range of 10 Gy to 1000 Gy and the response to electrons is nearl y identical to Co-60 gamma radiation which makes the system easy to ca librate. Readout is performed with a laser scanning densitometer with a 100 mum spot size which can be stepped in increments of 40 mum in tw o dimensions. Examples of the results of measurements of Sr-90/Y-90 ey e applicators as well as particle sources of Sr-90/Y-90Y, Co-60, and T m-170 are given.