Technique

♦ Linear accelerator or cobalt unit—optimum energy around 6 MV.

♦ Fractionated TBI is preferred for reasons of convenience.

♦ Patient lies on couch behind a perspex sheet (to provide full skin bolus) either on their side or back and side alternately.

♦ Treatment is given by opposed fields for half each treatment time.

♦ The couch is placed at an extended distance from the machine to obtain the field size required to cover the whole body.

♦ The dose distribution will be inhomogenous because of variation in AP/PA separation along the body and because of density differences (especially the lung). This can be compensated for by using bolus or lung shielding but is unnecessary using schedules described here, where doses do not exceed tolerance for any normal tissues.

♦ The maximum risk of damage is to the lung.

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