The effect of carbon fibre inserts on the build-up and attenuation of high energy photon beams.

BACKGROUND AND PURPOSE

The use of new materials in radiotherapy requires an investigation of the effects of these materials on the relevant beam parameters. The high strength and low density of carbon fibre suggest an excellent material for table inserts with minimal attenuation, without changing the skin sparing effect in the build-up zone.

MATERIALS AND METHODS

In this paper three different carbon fibre plates and two conventionally table top materials are studied in Co-60, 6 MV and 23 MV photon beams.

RESULTS AND CONCLUSIONS

From depth dose measurements it is clear that the dose in the build-up zone is influenced in the qualities of the beams. The mutual differences for the three carbon plates are minimal. For Co-60 the depth of the maximum dose is decreased by carbon from 5 to 2 mm and the surface dose is increased from 18 to 76%. For 6 and 23 MV the surface dose is increased from 21 to 52% and 20 to 32%, respectively, as well as the dose in the build-up region. A transmission of 99% was measured for two carbon plates out of three in Co-60 and for one out of three in 6 MV.