Development of treatment techniques for radiotherapy optimization

Over the last decade a large number of new treatment techniques have been developed to allow a true optimization of the delivered dose distribution in radiation therapy. The most important clinical requirement of most optimization techniques is to be able to deliver strongly nonuniform beams on the patient from arbitrary directions. For very complex tumors the number of beams required to eradicate the tumor without severe injury to normal tissues is quite high, to accurately make the three dimensional dose distribution conform to the target volume. For more simple target geometries fewer beams are sufficient, and in many cases with small tumors the classical uniform rectangular beams will do nicely. A number of new treatment techniques, from narrow beam robot mounted linear accelerators through fan beam devices using linear multileaf collimation in rotary gantries, to the most flexible external beam devices with scanned electron and photon beams and/or dynamic multileaf collimation available over the whole treatment field, are now rapidly coming into clinical use.