Inversed-Planned Respiratory Phase Gating in Lung Conformal Radiation Therapy

Area of Science:

• Radiation Oncology
• Medical Physics
• Image-Guided Therapy

Background:

• Respiratory motion significantly impacts lung radiation therapy accuracy.
• Traditional gating methods often use a single phase (end-exhalation), which may not be optimal for all beams.
• Patient-specific factors influence optimal respiratory gating strategies.

Purpose of the Study:

• To assess patient-specific factors influencing optimal gating windows in lung radiation therapy.
• To develop and evaluate a personalized respiratory gating technique using inverse planning optimization.
• To determine if optimal gating windows vary based on tumor size, location, and motion.

Main Methods:

• Developed a personalized gating technique using inverse planning optimization.
• Utilized 4-dimensional CT scans to extract anatomical data for each respiratory phase.
• Incorporated patient breathing motion data to estimate time spent in each phase.
• Retrospectively analyzed 15 lung cancer patients treated with hypofractionated conformal radiation therapy.

Main Results:

• Optimal gating plans utilized end-exhalation for only 34% of beams, deviating from traditional single-phase gating.
• Maximal and mean doses to the esophagus, heart, and spinal cord were reduced by 15%-26%.
• Beam-on times were reduced by an average of 23% compared to single-phase gating plans.

Conclusions:

• Introduced a personalized respiratory gating technique for lung radiation therapy.
• Inverse planning optimization determines patient- and beam-specific gating phases.
• This technique enhances the dosimetric quality of radiation therapy treatment plans.