SPSS-based correlation analysis for flattened photon beams with energy of 6 MV between TrueBeam and Edge

Abstract

Author(s): Sara Archir*, Mohammed El Adnani Krabch, Bachouchi Mounir and Mourad Trihi

Transferring a patient from one linac to another for radiotherapy treatment necessitates the use of dosimetrically correlative linacs. By modeling the beam data into one dataset per linac treatment plan, the transfer reduces workflow and systemic dose delivery errors. In this study, the correlation between the dosimetric properties of the Varian Edge and TrueBeam 6 MV FF photon beams from IBM SPSS Statistics Version 22.0 was measured. The results from the comparison of percentage depth dose (rs = 0.999; ρ = 0), beam profile (rs = 0.989 ~ 0.994 ~ 0.987~ 0.981 ~ 0.930; ρ = 0) and output factor (rs= 0.979; ρ = 0) showed a perfect and strong correlation between the two accelerators.Furthermore, the Dmax was very similar and the quality index TPR(20/10), flatness, symmetry, and mean penumbra of TrueBeam (SD-120 MLC) were less than 1% and 1 cm smaller than Varian Edge. In comparison, the Varian Edge (HD -120 MLC) MLC transmission factor and dosimetric leaf gap values were two times higher and often two times lower than TrueBeam (SD-120 MLC), respectively. However, the results show that the MLC parameters varied greatly, resulting in uncorrelated linacs in the beam. This difference is due to the smaller leaf projection at the Varian Edge's isocenter. In stereotactic radiosurgery, the (HD-120 MLC) had the potential to improve dose conformity to the target volume and reduce dose to critical structures. Furthermore, the dosimetric leaf gap influences MLC treatment planning systems and is considered as a critical parameter in the equivalence between linear accelerators.

In the event of a malfunction or maintenance work, the patient cannot switch from one linac to another without having the treatment plan recalculated.

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