SU-E-J-149: Is Rotational IMRT More Susceptible to Tumor Motion than Dynamic IMRT?

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Organ motion during radiation therapy can significantly impact treatment accuracy.
• Intensity-modulated radiation therapy (IMRT) is a common technique for precise dose delivery.
• Rotational IMRT delivery methods warrant investigation regarding their robustness against organ motion.

Purpose of the Study:

• To compare the susceptibility of rotational IMRT (RapidArc) versus fixed-field IMRT (sliding window) to organ motion.
• To evaluate the dosimetric impact of simulated tumor motion on different IMRT techniques.

Main Methods:

• Treatment plans for lung and pancreas cases were created using RapidArc and sliding window IMRT.
• Sinusoidal couch motion was simulated to emulate longitudinal, lateral, and vertical tumor motion.
• Monte Carlo dose verification software and Gamma analysis were used to compare dose distributions.

Main Results:

• Preliminary analysis indicates comparable susceptibility to motion between RapidArc and sliding window IMRT.
• A 95% Gamma pass rate was achievable with a 6%-6-mm criterion for RapidArc versus 8%-8-mm for sliding window in one lung case.
• Findings align with existing models on intra-fraction motion effects in dynamic IMRT.

Conclusions:

• Rotational IMRT delivery is not inherently more susceptible to organ motion compared to sliding window IMRT.
• Current results support the hypothesis that both techniques exhibit similar robustness against organ motion.