# Dosimetric analysis of SIB whole brain radiotherapy planning: Comparison of coplanar VMAT and tomotherapy techniques

## TL;DR

This study compares tomotherapy and VMAT for whole-brain radiotherapy with a boost, finding tomotherapy offers better dose conformity and organ protection.

## Contribution

The study introduces a comparative dosimetric analysis of tomotherapy and VMAT for SIB-WBRT, emphasizing the impact of evaluation indices on plan quality.

## Key findings

- Tomotherapy provided higher D98% values for target volumes compared to VMAT.
- Tomotherapy showed lower maximum and mean doses to the lenses and eyes.
- Tomotherapy outperformed VMAT in conformity and homogeneity indices for target volumes.

## Abstract

Radiotherapy techniques have advanced significantly over the past few decades. Whole‐brain radiotherapy combined with a simultaneous integrated boost (WBRT+SIB) is increasingly used to treat limited brain metastases.

To retrospectively compare helical tomotherapy and coplanar volumetric modulated arc therapy (VMAT) for WBRT with a SIB‐WBRT in patients with multiple brain metastases. Additionally, it emphasizes the importance of selecting appropriate evaluation indices when comparing SIB plans.

Fifteen patients with 2‐ 3 metastatic lesions were retrospectively analyzed in this study. Treatment planning was performed using TomoHD and eclipse planning systems for tomotherapy and VMAT, respectively. Dose–volume histograms were used to assess the doses delivered to the target volumes and organs at risk (OARs). Quantitative metrics, including the homogeneity index (HI), conformity index (CI), and plan quality index (PQI), were used for the evaluation.

Tomotherapy yielded significantly higher D98% values for both the planning target volume (PTV) WB and PTV_met compared with VMAT (p < 0.05). It also provided lower Dmax and Dmean values for the lenses and eyes (p < 0.001 and p < 0.02, respectively). Tomotherapy was superior in terms of PTV whole‐brain CI and PTV_met HI and CI (p < 0.05). However, no significant difference was observed in the PQI values between the techniques (p > 0.05).

Both tomotherapy and VMAT achieved acceptable target volumes and OAR doses in SIB applications. Tomotherapy showed advantages in terms of dose conformity and critical organ sparing. Moreover, this study highlights the impact of selecting appropriate evaluation indices on interpreting plan quality, particularly for complex treatment approaches such as SIB.