The special aspects in the planning and use of an electron linear accelerator facility for intraoperative radiotherapy (IORT)]

Limiting conditions for the planning of the installation of an electron linear accelerator in an operating theatre are described taking into account the radiotherapeutical and surgical requirements based on the example of the Essen facility for intraoperative radiotherapy (IORT) with electrons. Special features of the facility like a non-contact electron applicator system with television monitoring, table-top trolley, which is used also during irradiation, are explained in detail. Measured isodose curves for all tubes and all electron energies serve for the radiotherapist as criteria for decision on tube size and electron energy selection during surgical operation. The influence of misalignments of the tube on dose distributions is investigated. Limit values of alignment tolerances are deduced. Daily constancy tests for monitor calibration, electron energy, and tube alignment system are to be performed for quality assurance. Tables of the planned and realized treatments and of a representative time schedule of an IORT give a survey on the indications and the necessary time effort and staff. Completion of the set of tubes as well as optimization of the tube fixation accessory and of the table-top trolley are main subjects for future developments.