Fluorescent screen video imaging for checking linac beams in dynamic stereotactic radiosurgery

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Radiation Oncology

Background:

• Precise beam targeting is essential for effective stereotactic radiosurgery (SRS).
• Current monitoring methods may have limitations in dynamic assessment.
• Ensuring beam stability and accurate isocenter positioning is critical for patient safety and treatment efficacy.

Purpose of the Study:

• To describe a novel monitoring system for real-time verification of radiation beam parameters in SRS.
• To assess the system's capability in evaluating beam intensity, uniformity, position, and diameter.
• To evaluate the dynamic isocenter positioning accuracy using the 'ball test' technique.

Main Methods:

• A monitoring system comprising a fluorescent screen, video camera, and computer interface was developed.
• The system analyzes approximately ten frames per second for beam characteristic verification.
• The 'ball test' technique was employed with the system mounted on the gantry to assess dynamic isocenter position.

Main Results:

• The 6-MV radiation beam demonstrated acceptable stability in terms of intensity and uniformity.
• The system confirmed that isocenter shifts relative to gantry and couch angles were acceptably reproducible.
• Real-time analysis of beam parameters was achieved with approximately ten frames analyzed per second.

Conclusions:

• The described monitoring system provides effective real-time quality assurance for stereotactic radiosurgery.
• The system's ability to verify beam stability and dynamic isocenter position enhances treatment precision.
• Regular monthly quality assurance tests using this apparatus are conducted at the facility.