# Synthetic computed tomography techniques for adaptive proton therapy in head and neck cancers

## TL;DR

This study compares synthetic CT techniques for adaptive proton therapy in head and neck cancer patients, showing their effectiveness for dose recalculation.

## Contribution

The study introduces an anatomy-preserving virtual CT method suitable for head and neck cancer patients.

## Key findings

- APvCT and conventional virtual CT methods showed lower mean absolute errors compared to corrected CBCT.
- All synthetic CT methods achieved gamma passing rates greater than 96.7% for proton dose recalculation.
- Mean absolute error in CT number values was ≤ 42 HU across all methods compared to repeat CT.

## Abstract

Head and neck (HN) radiotherapy often requires corrective interventions. This study evaluated three methods for synthetic computed tomography (CT) generation for adaptive HN planning using cone-beam CT (CBCT) images. CBCT images for 15 patients were paired with same-day repeat CT scans and robustly optimized proton plans were recalculated. The anatomy-preserving virtual CT (APvCT) method utilized organs-at-risk as deformation controlling structures. APvCT and conventional virtual CT methods showed lower mean absolute errors in CT number values compared to corrected CBCT; however, all synthetic CT methods were found suitable for proton dose recalculation with gamma passing rates greater than 96.7% (2%,2mm).

•Anatomy-preserving virtual computed tomography suitable for head and neck patients.•Corrected cone beam and virtual computed tomography led to similar results.•Mean absolute error ≤ 42 HU in all methods compared to repeat computed tomography.•Gamma passing rate (2%, 2 mm) ≥ 96.7% for proton dose recalculation in all methods.

Anatomy-preserving virtual computed tomography suitable for head and neck patients.

Corrected cone beam and virtual computed tomography led to similar results.

Mean absolute error ≤ 42 HU in all methods compared to repeat computed tomography.

Gamma passing rate (2%, 2 mm) ≥ 96.7% for proton dose recalculation in all methods.