Three levels of dose planning and treatment are:

 ■ Conventional treatment uses single or opposing beams, with or without 2D dose distributions, with compensators and simple shielding. 

■ Conformal treatment involves target volume delineation of tumour and normal organs according to ICRU principles with 3D dose calculations using MLC to shape beams.

■ Complex treatment includes the use of IMRT to shape the fluence of the beam, dynamic treatments, IGRT and 3D or 4D delivery. 


Most dose computation is done using 3D computerised treatment planning systems which are programmed with beam data from therapy machines. These systems require careful quality control programmes. Following production of a satisfactory isodose distribution to a given target volume using 2D or 3D algorithms, the calculations are checked by a physicist and detailed instructions for delivery are prepared by radiographers on the therapy unit.

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