The aim of radiotherapy to eradicate tumor cells with ionizing radiation implies a radiation dose to surrounding
normal tissue. In conformal therapy special attention is paid to match the high dose volume in three dimensions
around the tumor volume. Tumor conform treatments allow dose escalation in the tumor resulting in an increased
tumor control probability while delivering the same dose (as in a "conventional treatment) to normal tissue.
Conforming the treated volume to the target is not a new concept, but only the technological improvements and
developments of the last decades allow the technical achievement of conformal therapy (improved image quality
for tumor definition, faster computers for three dimensional treatment planning systems to calculate the dose
distribution in the patient, on-line portal imaging devices to check the patient alignment during treatment,
commercially available multileaf collimators for treatment delivery). At the moment conformal radiotherapy is in
routine clinical use only in several radiotherapy centers all over the world.
Several new steps are involved in the conformal therapy treatment delivery process when compared with
conventional treatments. The new equipment necessary to perform conformal therapy increases the workload for
quality assurance (QA) procedures. QA procedures encompassing all technical components for a conformal therapy
program are not straightforward and still under development.
The project "Quality Assurance in Conformal Radiotherapy" encompasses quality assurance for the therapy unit
(linear accelerator equipped with a multileaf collimator MLC), the treatment planning system (TPS) with a new
implemented algorithm developed for the dose calculation for this type of integrated MLC and the network links
for the data transfer between TPS, field prescription console and treatment unit. For mechanical and dosimetric
control of the therapy unit tolerance levels have to be stated together with appropriate action levels. Dose
measurements (in water and special phantoms ) representing clinical conditions have to be performed to evaluate
the accuracy of the TPS and to estimate the obtainable accuracy in clinical situations. The testing of the network
links is a crucial element in the safety of conformal radiotherapy. Protocols for QA in conformal radiotherapy are
to be defined.