An optimized online verification imaging procedure for external beam partial breast irradiation.

Area of Science:

• Radiation Oncology
• Medical Imaging
• Image-Guided Therapy

Background:

• External-beam partial breast irradiation requires precise patient setup.
• On-line verification imaging is crucial for accurate treatment delivery.
• Kilovoltage (kV) on-board imagers (OBI) offer potential for real-time imaging during radiotherapy.

Purpose of the Study:

• To evaluate the efficacy of a kV OBI-equipped linear accelerator for on-line verification imaging in partial breast irradiation.
• To optimize and assess imaging techniques for image quality, dose, and physical clearance.
• To determine the clinical applicability of nonorthogonal kV image pairs for online setup correction.

Main Methods:

• Optimization and assessment of kV imaging techniques using an anthropomorphic phantom for image quality and dose.
• Evaluation of physical clearance using a volunteer.
• Implementation of optimized nonorthogonal kV image pairs for online verification in 17 patients undergoing accelerated partial breast irradiation.
• Recording of imaging session duration, collision risk, visualization of surgical clips, and setup deviations.

Main Results:

• Nonorthogonal kV image pairs demonstrated optimal image quality, clearance, and dose.
• All 170 image sessions showed low collision risk.
• Surgical clips were well visualized in all cases where present (n=5).
• Average imaging session time was 6 minutes 16 seconds, with a learning curve effect.
• Online setup deviations up to 1.3 cm were detected and corrected.

Conclusions:

• Nonorthogonal kV image pairs provide effective and efficient online verification for partial breast irradiation.
• The technique allows for accurate online correction of patient setup deviations.
• Further multicenter studies are needed to assess generalizability and dependence on skilled staff.