Dosimetric comparison of FF and FFF beams in VMAT treatment plans of head and neck cancers

Abstract

Author(s): Silpa Ajay Kumar*, Musthafa MM, Suja CA, Resmi KB, Lisha Jose, Geetha Muttath and Shahirabanu KP

Background: Currently we are using flattened beams for Volumetric Modulated Arc Therapy (VMAT) for head and neck treatments. The purpose of this study is to find whether there is any dosimetric benefits of FF beams in VMAT head & neck cancer treatments over FFF beams and vice versa.

Aim: To compare dosimetric parameters of VMAT plans with FF and FFF beams in head and neck cancers.

Materials and methods: Dosimetric data of fifty cases, Planned with FF and FFF beams, of oral cavity cancers were retrieved from the Monaco treatment planning system (version 5.2). Flattened and FFF beam plans are quantitatively compared in terms of Planning Target Volumes (PTV) Coverage, conformity index, homogeneity index, the Organ at Risk (OAR) sparing, peripheral dose and the Monitor Units (MU).

Results and Discussion: Comparable dose distributions were observed for FFF and FF VMAT plans. There was no significant difference noticed for organ at risk doses, like the spinal cord, oesophagus and parotid, of the two plans. However, FFF VMAT plans provided the lowest mean doses for OARs; no statistical significance was observed in the case of peripheral dose distribution. FF VMAT plans showed comparatively higher homogeneity and conformity with statistically significant D98 and D50 values. Monitor Units of the fifty cases were evaluated and were observed to be significantly higher for FFF plans.

Conclusion: This study of comparison of treatment planning for oral cavity cases demonstrates that FF and FFF treatment plans were in general of comparable quality. This is important in the sense that FFF need lesser delivery time there by saving the machine heating and treatment cost.

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