# Evaluation of radiation treatment plan quality in head and neck cancer: a comparative analysis of RapidArc technique with flattening filter and flattening filter-free photon beams

## TL;DR

This study compares the quality of radiation treatment plans for head and neck cancers using two different photon beam techniques, finding that flattening filter-free beams offer better results.

## Contribution

The study provides a comparative analysis of RapidArc treatment plans using flattening filter and flattening filter-free photon beams for head and neck cancers.

## Key findings

- FFF-RA plans showed better conformity and homogeneity indices than FF plans.
- FFF-RA plans resulted in lower doses to organs at risk like parotid glands and eyes.
- FFF-RA plans had shorter beam-on times and higher gamma passing index rates.

## Abstract

This study aims to evaluate the treatment plan quality for oral cavity cancers in the head and neck region using the RapidArc (RA) technique with both flattening filter (FF) and flattening filter-free (FFF) photon beams.

In this analytical study, treatment plans for 12 patients originally planned with a 6 MV FF photon beam were recreated using the RA technique with a 6 MV FFF photon beam. Identical beam parameters and planning objectives were maintained for both sets of plans to facilitate comparison. All plans were evaluated based on planning indices and doses to organs at risk (OAR).

A significant dose variation was found in the minimum (Dmin) and mean (Dmean) doses of the high-risk planning target volume between FF and FFF photon beam RA plans. However, the dose distribution for the low-risk planning target volume was equivalent between the two techniques. The FFF-RA plans demonstrated superior conformity and homogeneity indices compared to the FF plans, with these differences being statistically significant. In addition, the FF-RA plans showed higher doses to the parotid glands, eyes and lenses than the FFF plans. The FFF plans also showed significantly shorter beam-on treatment times and a higher gamma passing index rate compared to the FF plans.

In contrast to the FF photon beam, an FFF photon beam-oriented RA plan provides significant OAR sparing without losing the quality of the treatment plan. High monitor units and beam on time are major highlights of the RA plan with FFF beam.