Evaluation of a high resolution diode array for CyberKnife quality assurance

Area of Science:

• Medical Physics
• Radiation Oncology
• Quality Assurance

Background:

• CyberKnife stereotactic radiosurgery relies heavily on radiochromic film (RCF) for machine quality assurance (QA).
• Exploring advanced detector technologies is crucial for improving the efficiency and accuracy of QA procedures.

Purpose of the Study:

• To evaluate a high-resolution diode array as a potential alternative to RCF for CyberKnife QA.
• To assess the array's performance in geometrical accuracy (AQA), iris collimator field size constancy (Iris QA), and multileaf collimator (MLC) positioning.

Main Methods:

• The SRS Mapcheck diode array and its software were used to perform three CyberKnife QA tests.
• Tests included geometrical accuracy (AQA) with orthogonal beams, iris collimator field size constancy (Iris QA), and MLC positioning.
• Constancy, repeatability, and sensitivity to introduced errors were compared between the diode array and RCF.

Main Results:

• For AQA tests, the diode array yielded results comparable to RCF (0.18 ± 0.14 mm differences) with higher reproducibility.
• The diode array demonstrated high linearity and sensitivity (detecting 0.1 mm changes) in Iris QA tests.
• While the array detected single MLC leaf errors, it failed to detect systematic displacements of entire MLC banks.

Conclusions:

• The diode array is a sensitive and accurate tool for AQA and Iris QA, potentially replacing RCF for faster, reliable CyberKnife QA.
• The array's current limitations in detecting systematic MLC errors hinder its full adoption for all QA aspects.