J Korean Radiol Soc.  1981 Dec;17(3):555-561. 10.3348/jkrs.1981.17.3.555.

The experimental measurements of the effects of field size and shadow tray on the relative surface doses for Co-60 and 10 MV X-ray beams

• Choo IW
• Park CI
• Han MC

• KMID: 2463390
• DOI: http://doi.org/10.3348/jkrs.1981.17.3.555

Abstract

It is well known that high energy X and r-ray have high penetration power in tussue, but have lower survacedose which is called the "skin sparing effect". However, the surface dose can be increased significantly by excessive electron contamination and it is an important factor intreatment planning in the presence of a blocktray, especially in isocentric set-up. So relaltive surface doses for 10MV-X-ray and Co-60 r-ray were measuredwith various field sizes and SSD with or withoug 1/4" lucite shadow tray, present in the beams, using pancakechamber and polystylene phantom. The results obtained are as follows. 1. A rapid increase in surface dose isapparant with increasing field size in 10MV X-ray and Co-60 r-ray. 2. high surface dose is evident for smallerdistance from the tray, so at least 25cm of skin shadow tray distance for 10MV X-ray and 20cm for Co-60 are desirable. 3. Utilization of either bolus for treatment field or electron boost should be considered in treatmentof superificial nodal disease. 4. A tray using an intermediate or high z No. filter can be reduced the surfacedose significantly.

MeSH Terms

Polymethyl Methacrylate
Silver Sulfadiazine
Skin
Polymethyl Methacrylate
Silver Sulfadiazine