1992 Volume 48 Issue 9 Pages 1684-1691
We have often encountered patients with segmental instrumentation when employing external beam therapy of bone metastasis, and felt it important to investigate the effect of stainless steel in relation to does distribution. The stainless steel in a 10MV X-ray beam increases the radiation level on the side of the steel towards the radiation source by backscattered radiation and sideways by scattering radiation from the metal. These results showed these overdosages occurred within 10mm from the stainless steel. In the transition zone, however, the dose was much lower in response to the thickness of the stainless steel than in the acrylic phantom. Especially, the absorbed does of the just behind stainless steel abruptly dropped due to absorption of the secondary electrons and these underdosages which were below the steel were limited in the vicinity of its interface. The front and behind sides interface effect in treatment with the opposed beams using one field were reduced.
