[Progress in external irradiation in radiation therapy].

Radiation therapy has been used most frequently as one of the important modalities in multidisciplinary cancer treatment. Through the progress of diagnostic imaging, one can now evaluate tumor extent more easily and precisely. On the application of external irradiation, both good local control rate and less radiation damage could be obtained with precise irradiation of the target lesion. A treatment planning system combined with CT simulator and other computerized equipment surrounding the treatment machine have proved useful for clinical use. As a result, conformal radiotherapy and concentration technique of narrow beam onto the target lesion have been applicable with these procedures. These techniques with precise irradiation planning are essential for multidisciplinary treatment to obtain good quality of life during the clinical course of cancer patients.