Assessing residual motion for gated proton-beam radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Biomedical Engineering

Background:

• Gated radiation therapy enhances dose conformity for moving targets, crucial in proton beam therapy due to finite proton range.
• Respiratory motion introduces variations in target depth, necessitating gating techniques.
• Current gating methods rely on external surrogates that may not perfectly track internal target motion.

Purpose of the Study:

• To investigate the impact of physiological motion phenomena on gated radiotherapy.
• To analyze the effects of phase delay and baseline drift in respiratory surrogates during proton therapy.

Main Methods:

• Utilized an external surrogate to monitor respiratory motion.
• Simulated and analyzed the influence of phase delay between internal and surrogate motion.
• Examined the effects of baseline drift on gated treatment delivery.

Main Results:

• Phase delay between internal target motion and external surrogate motion can lead to inaccuracies in gating.
• Baseline drift in respiratory patterns affects the accuracy of gated proton therapy delivery.
• These phenomena can compromise dose conformity and potentially increase irradiated tissue volume.

Conclusions:

• External surrogates for gated radiotherapy are susceptible to inaccuracies caused by phase delay and baseline drift.
• Understanding and mitigating these physiological effects is essential for optimizing gated proton beam therapy.
• Further research is needed to develop more robust gating strategies for moving targets.