# Evaluation of Diaphragm Position Variations During Proton Therapy for Pediatric Patients With Neuroblastoma

## TL;DR

This study examines how the diaphragm moves during proton therapy in children with neuroblastoma, finding large individual differences.

## Contribution

The study provides new insights into diaphragm motion variability in pediatric patients undergoing proton therapy.

## Key findings

- Intrafractional diaphragm motion averaged 8.3 mm on the right and 6.4 mm on the left.
- Interfractional displacement of 5 mm or more occurred in 13% of treatment fractions.
- No significant correlation was found between diaphragm motion and patient height.

## Abstract

Background

To evaluate the respiratory-induced intrafractional diaphragm motion and interfractional diaphragm displacement in pediatric patients with neuroblastoma (NBL).

Materials and methods

Ten pediatric patients with a mean age of 4.5 years (range: 1.8-8.7 years) with abdominal NBL treated with proton therapy (PT) have been evaluated. Intrafractional motion and interfractional displacement have been analyzed by using cine radiography and orthogonal X-ray images, respectively. In each case, the cranio-caudal positions of the diaphragm have been measured as an index. This study has investigated the possible correlations between intrafractional diaphragm motion and height. Additionally, interfractional displacement and its time trend during the treatment course have been analyzed.

Results

The average right and left diaphragm intrafractional motions of 8.3 mm (range: 4.4-11.5 mm) and 6.4 mm (range: 2.2-11.8 mm) were observed, respectively; however, no significant correlation has been observed with height. An interfractional displacement of 5 mm or more has been observed in 20 out of 152 fractions (13%). The average absolute value of the interfractional displacement was 2.5 mm (range: 0-8.6 mm). Interfractional displacement did not show a peculiar tendency throughout the treatment period.

Conclusions

It was suggested that respiratory-induced diaphragm position variation in children varies greatly among individuals, and accurately estimating it based on height is difficult. Thus, these individual evaluations are considered indispensable.