Dose measurements at superficial energies required special considerations. First, care must be taken in selecting appropriate phantom materials. Materials that are adequate tissue substitutes at mega-voltage energies might not be adequate at superficial energies. The suitability of a material can be judged by comparing its mass attenuation and mass energy absorption coefficients at superficial energies to those of the tissue of interest. Second, very low energy x-ray and electron contaminants must be removed from the superficial beam before they reach the detector. For detectors with a very thin window, this can be achieved by placing thin film on top of the detector. Failure to properly eliminate contaminants can result in a large increase in dose measured directly at the surface.
- superficial x-ray
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