Commissioning experience with cone-beam computed tomography for image-guided radiation therapy

Area of Science:

• Medical Physics
• Radiotherapy Technology
• Image-Guided Radiation Therapy

Background:

• The integration of cone-beam computed tomography (CT) systems with linear accelerators is crucial for modern image-guided radiation therapy (IGRT).
• Commissioning and quality assurance (QA) are essential steps to ensure the safety, accuracy, and reliability of these advanced systems.

Purpose of the Study:

• To report on the commissioning of an Elekta Synergy cone-beam CT system.
• To present a comprehensive QA procedure as a guide for other institutions.
• To evaluate the system's safety, geometric accuracy, image quality, registration accuracy, and patient dose.

Main Methods:

• The commissioning process involved six key elements: system safety, geometric accuracy (megavoltage and kilovoltage isocenter agreement), image quality assessment, registration and correction accuracy, patient dose evaluation, and QA procedure development.
• Geometric accuracy was assessed using phantom measurements, with isocenters found to agree within 1 mm.
• Image and alignment accuracy were evaluated using a skull phantom, achieving results within 1 mm and 1 degree.

Main Results:

• The Elekta cone-beam CT system successfully passed all safety tests.
• Isocenter agreement between megavoltage and kilovoltage beams was within 1 mm.
• Reconstruction and alignment algorithms demonstrated accuracy within 1 mm and 1 degree using phantom studies.
• Average agreement in coordinate measurements within a Rando phantom was excellent, with minor deviations attributed to CT slice thickness.

Conclusions:

• The commissioning process validated the Elekta cone-beam CT system's performance for clinical use.
• A robust QA protocol, including daily, monthly, and annual checks, was established.
• The developed QA procedures provide a valuable framework for other facilities implementing similar systems.