A method of large irregular field compensation

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Abstract
For large irregular field radiation treatments, the dose distribution is affected by the surface contour, the change in SSD at points away from the central ray of the beam, and the change in scatter conditions due to the irregular shape of the field. These combined effects could produce a dose variation within the irradiated volume up to 30%. A method of compensating for all these effects is described with special consideration being given to a simple method of producing a missing tissue compensator. This method incorporates a simple mechanical device for marking out thin lead sheets to show lines of equal air gap distance