Techniques of magna-field irradiation.

Total body irradiation (TBI) techniques have evolved over the years, with the basic goals remaining adequate immunosuppresion and/or tumor eradication. TBI technique variables include: machine type and energy, prescription parameters (dose, number of fractions, dose/fraction, dose rate), patient position, therapy room and machine constraints (field size, distance) and beam modifiers (bolus, compensators, shields). Related variable include chemotherapy agents and schedules, and 'boost' radiotherapy. Seven representative insitutions that treat a large number of TBI patients were surveyed for these variables. Homogeneity has been achieved generally within +/- 10% with the use of these techniques. One 'sentinel' effect is disucssed, namely interstitial pneumonitis, as a measure of normal tissue effects with varying techniques. There is an indication that more fractionated methods, used either daily or in a hyperfractionated fashion, are leading to a decreased incidence of pneymonitis.