CLINICAL USE OF ASYMMETRIC COLLIMATORS

Purpose: To illustrate some of the radiation treatment techniques with asymmetric collimators in one field dimension. Methods and Materials: Treatment planning for various sites is done with an in-house develop ed treatment planning system. Dose distributions in the central plane are illustrated. Results: The use of asymmetric collimation, in additi on to being a replacement for cerrobend and lead blocks, can facilitat e treatment setup with boost fields and with half-beam asymmetric fiel ds as in matching two adjacent fields, in avoiding nearby critical org an or tissue, and in tangential breast treatment. The use of asymmetri c collimators would alter the dose distribution across the radiation f ield and should be accounted for during treatment planning. In conjunc tion with arc rotation or multiple asymmetric fields, two-dimensional conformal radiotherapy is possible. Conclusion: The full potential of asymmetric collimation requires the use of a proper treatment planning algorithm. Some of the treatment techniques with asymmetric collimati on in one field dimension are shown here. (C) 1997 Elsevier Science In c.