Feasibility study of a multi-lesion cyberknife radiotherapy plan verification method using a 2D array with pre-set...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiosurgery

Background:

• Validating intracranial multi-lesion CyberKnife plans with SRSmapcheck is challenging due to limitations in measuring multiple targets and lack of roll verification.
• Existing methods using a fixed 0° array setting only measure one target, leaving others unverified.
• The CyberKnife treatment planning system lacks support for roll verification tools, and X-sight fiducial marker guidance is incompatible with free array roll.

Purpose of the Study:

• To develop and validate a novel method for verifying intracranial multi-lesion CyberKnife plans using SRSmapcheck with pre-set roll angles.
• To optimize dose distribution verification in high-dose and rapidly varying areas for multi-lesion radiosurgery.
• To compare the efficacy of the pre-set roll angle method against the traditional fixed 0° verification method.

Main Methods:

• A geometric model was created to determine the relationship between SRSmapcheck array roll angle and tumor spacing.
• SRSmapcheck and StereoPHAN computed tomography (CT) images were acquired at 15° intervals for phantom plans.
• 101 intracranial multi-lesion plans were verified using both fixed 0° and pre-set roll angle methods, with subsequent comparative analysis.

Main Results:

• The pre-set roll angle method assessed an average of 2.34 targets per plan, compared to 1.32 targets with the fixed 0° method.
• Plan pass rates remained stable between methods for gamma analysis criteria of 2 mm/1% and 2 mm/2%.
• Recommended gamma analysis criteria for pre-set roll angle verification are 1 mm/1% and 1 mm/2% for optimal results.

Conclusions:

• SRSmapcheck with the pre-set roll angle method enables comprehensive validation of intracranial multi-lesion CyberKnife plans.
• This novel approach allows for the measurement of multiple targets within a single validation session.
• The study recommends specific gamma analysis criteria (1 mm/1% and 1 mm/2%) for effective pre-set roll angle verification.