Compensation for respiratory motion by gated radiotherapy: an experimental study

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy

Background:

• Respiratory organ motion, particularly lung tumors, introduces significant intrafractional motion.
• This motion leads to dose uncertainties in Intensity-Modulated Radiation Therapy (IMRT).
• Gated dose delivery aims to mitigate these uncertainties by accounting for organ motion during treatment.

Purpose of the Study:

• To investigate the benefits of gated dose delivery for lung tumors affected by respiratory motion.
• To quantify the impact of gating on treatment time and dose distribution accuracy.
• To determine optimal gating strategies for improving radiotherapy outcomes.

Main Methods:

• Simulated respiratory motion using a moving lung phantom with a lung tumor.
• Designed an IMRT plan and irradiated the phantom in static and moving states.
• Employed film dosimetry and treatment planning software for dose distribution analysis.
• Calculated dose-volume histograms (DVHs) for various gating thresholds and treatment modalities.

Main Results:

• Irradiation without gating resulted in underdosages up to 33%, especially at tumor edges.
• Gated delivery reduced underdosage to as low as 9%, depending on the gating threshold.
• Treatment time increased by 20%-100% with gated delivery, calculable based on the threshold.

Conclusions:

• Gated radiotherapy is effective in reducing underdosage caused by respiratory motion in lung tumors.
• A balance exists between improved dose distribution and increased treatment time with gating.
• Gating strategies can be optimized to achieve better therapeutic ratios in lung cancer radiotherapy.