TECHNICAL ADVANCES IN RADIATION-THERAPY

The aim of radiation therapy is to deliver a dose capable of eradicati ng the tumor without producing more than minimal damage in surrounding healthy tissues. This requires use of restraining devices that ensure complete immobility of the target area during radiation. The target v olume an dose-limiting normal tissues should be accurately marked usin g a simulator and a contouring device. Computerized systems should be used to ensure optimal selection of the type of radiation (photons, el ectrons), the energy of the radiation, and the treatment unit (X-ray g enerator, telecobalt, linear accelerator). Field delineation and tumor coverage should be checked using either port films or portal imaging. Many improved radiation therapy devices have been developed recently, including cyclotrons (neutrons, protons), simulator-CT scanners and C T scanner-simulators, stereotactic radiation therapy units, multileaf collimators, portal imaging, remote afterloading systems, and radiatio n planning computers.