Quantitative analysis of errors in fractionated stereotactic radiotherapy

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance in Radiotherapy

Background:

• Fractionated stereotactic radiotherapy (FSRT) minimizes radiation dose to healthy tissues.
• Rigorous quality assurance (QA) is essential for the precision of FSRT procedures.
• Previous QA protocols for FSRT require detailed examination and validation.

Purpose of the Study:

• To describe and evaluate the quality assurance procedures for fractionated stereotactic radiotherapy (FSRT).
• To estimate the accuracy of individual steps and the overall precision of FSRT treatments.
• To identify and quantify potential sources of error in FSRT delivery.

Main Methods:

• QA protocols encompassing CT localization, image transfer, laser alignment, and isocentric accuracy were established.
• Geometric phantoms, treatment planning computers, and specialized tools like the mechanical isocenter standard (MIS) were utilized.
• Head-frame stability was assessed using a depth confirmation helmet (DCH), and portal verification was performed via film tests.

Main Results:

• CT localization accuracy was measured at 1.2+/-0.5 mm.
• Isocentric accuracy of the linear accelerator and laser alignment achieved 0.5+/-0.2 mm.
• Overall treatment accuracy, excluding human errors, was determined to be 1.7+/-0.7 mm.

Conclusions:

• The implemented QA procedures provide a reliable framework for precise FSRT delivery.
• Accurate CT localization, isocentric accuracy, and head-frame stability are critical for successful FSRT.
• Continuous monitoring and analysis of QA data are vital for maintaining high standards in fractionated stereotactic radiotherapy.