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A concave tray with divergent block for desired dose distribution around shielded region in megavoltage radiation
J S Avadhani1, A S Pradhan, A Sankar
1Department of Medical Physics, Tata Memorial Hospital, Bombay, India.
Abstract:
In clinical situations large numbers of rectangular divergent blocks are required at different off-axis positions from central axis to shield sensitive organs. Superiority of divergent blocks over non-divergent blocks on a flat tray lies in improving the dose homogeneity. A method has been developed to minimize the number of divergent shielding blocks by using a concave tray at the collimator. The results of use of a single divergent block are similar to that of the use of several divergent blocks, each to match at different off-axis positions in the radiation beam. This type of single concave tray thus provides a considerable ease of handling divergent blocks in a busy radiotherapy centre.