ABSTRACT
On the other hand, advanced treatment planning and delivery cannot change the physics of x-ray transportation. Improvements in the therapeutic ratio have been attributed to redistribution of x-ray doses to less critical and more radioresistant tissues, such as muscle and fat while avoiding functionally important and sensitive organs such as the spinal cord and parotids. Calculation on integral doses versus treatment modality showed that although varying organs-at-risk (OARs) sparing can be achieved by increasing the number of beams and intensity modulation, the integral doses are nearly constant (D’Souza and Rosen 2003; Reese et al. 2009). When the tumor is encompassed by OARs or abutting OARs, dose constraints on tumor and OAR doses become dicult to meet at the same time, and compromises have to be made. is fundamentally limits radiation therapy eectiveness for radioresistant or large tumors. Although particle therapy can be used to improve dosimetry,
11.1 Radiation erapy and Need for Radiosensitizers .............................................................137 11.2 Physical Radiation Enhancer .................................................................................................138
