A study on needed or unneeded ReDosimetry and Recomissioning of a linac with Add on MLC by Comparing Dosimetric Data

Introduction: Today different uses of multileaf collimators(MLC) in different techniques of radiotherapy are common. Due to the use of this facility it is possible to have maximum radiation dose to target volumes and minimum radiation dose to critical tissues surronding treatment volumes. But there are numerouse Linear accelerators in IRAN without MLC. Because of high price of these new accelerators with MLC, maybe we have to use from Add on MLCs for our machines. The question is that do we need to redosimetry,recommissioning the linear accelerator and then revalidating our 3D Treatment Planning Software or not? Materials and Methods: For this purpose, first we add an Add on MLC on an Elekta Compact machine with 6 MV photon energy. Then we start dosimetry the machine by measuring dosimetry parameters like PDD in depth scan and profiles in crossline and inline scans. Also we measured scattering factors (Sc, Sp). All in reference radiotherapy fields and some most common fields. Results: Comparing between reference dosimetry parameters and new parameters from add on MLC in reference radiotherapy fields shows no significant deference. (pvalue<0.05) Conclusion: Due to these results need for redosimetry, recommissioning and consequences revalidating 3D treatment planning software will not be important for 6 MV photon energy in Elekta compact linear accelerator with Add on MLCs and will be optional.