Dosimetric evaluation of a treatment planning system using pencil beam convolution algorithm for enhanced dynamic wedges with symmetric and asymmetric fields

Background: The dosimetric performance of Eclipse 6.5 three dimensional treatment planning system (3DTPS) is evaluated by comparing the calculated and measured dose in two dimensions following the guide lines of American Association for Physicists in Medicine Task Group 53. Materials and Methods: The calculations were performed by the 3DTPS for symmetric as well as asymmetric fields for standard source to surface distance (SSD) at dmax, 5, 10 and 20cm depths in water phantom using 45° and 60° enhanced dynamic wedges (EDWs) in a field of 15 cm×15 cm size for 6 MV photon beams. Measurements were carried out for 6 MV photon beams produced by a linear accelerator, Clinac EX - 2100, equipped with EDWs using 0.125cc volume PTW ionization chamber and PTW UNIDOS electrometer for beam axis and two off axis points. Results: The deviations between the calculated dose (Dcalc) and the measured dose (Dmeas) at toe, centre and heel at different depths for symmetric as well as asymmetric fields for both the wedge angles is less than 2% at all the points and in all geometries. For 45° EDW the deviation was maximum at 20 cm depth and in asymmetric geometry. For 60° EDW the deviation was maximum at 20 cm depth but in symmetric geometry. Conclusion: The results indicate that the accuracy of Eclipse 6.5 (version 7.3.10) three dimensional treatment planning system used with the EDWs in symmetric as well asymmetric fields is adequate in clinical applications under the studied experimental conditio