Pretreatment setup verification by cone beam CT in stereotactic radiosurgery: phantom study

Area of Science:

• Medical Physics
• Radiotherapy Technology

Background:

• Stereotactic radiosurgery (SRS) requires high precision for patient positioning.
• Kilovoltage cone beam computed tomography (CBCT) is a potential tool for verifying patient setup in SRS.

Purpose of the Study:

• To evaluate the efficacy of CBCT in patient position verification for frame-based SRS.
• To investigate isocenter differences between the radiation beam and CBCT compared to a conventional SRS system.

Main Methods:

• A phantom with Gafchromic-EBT film and a pinhole was used for verification.
• Isocenter accuracy was assessed by comparing radiation beam isocenter to the target (pinhole).
• CBCT was performed, and its isocenter difference from the target was measured.

Main Results:

• The mean difference between the radiation beam and target was 0.6 ± 0.2 mm.
• The mean difference between the radiation beam and CBCT isocenter was 0.8 ± 0.1 mm.
• Both conventional stereotactic coordinate setup and CBCT isocenter accuracy met AAPM Report No. 54 standards.

Conclusions:

• Kilovoltage CBCT demonstrates sufficient accuracy for patient position verification in frame-based SRS.
• CBCT is a viable tool for enhancing setup accuracy in SRS delivery.
• The findings support the clinical integration of CBCT for SRS patient alignment.