Purpose: Image-guided stereotactic radiosurgery (SRS) is rapidly disseminating worldwide. A robust low-cost and universally accessible QA method is critically needed for its safe implementation and global collaborations. In this study, we developed a low-cost, universal, end-to-end Winton-Lutz method to address such a need.
Methods: After surveying the state-of-the-art SRS phantoms and QA strategies on the market, a simple two-piece detachable plastic film slab was created and specifically implemented for isocentric and off-center Winston-Lutz measurements. The phantom is constructed similar to the OSLD slabs shipped from IROC for Gamma Knife units. To conduct off-center Winston-Lutz testing, the user was instructed to cut a 0.3-mm solder wire into small bits (~ 0.5 mm). These fiducial bits were then randomly taped onto a radiochromic film (~250 cm²). The film was then needle-pricked on its back side at central positions of the taped fiducial bits. The film was then sandwich pressed between the two slabs. Treatment plan was created to deliver a near-spherical dose toward individual fiducials via online imaging guidance. The film and RTDose file were collected and analyzed centrally, a process similar to IROC workflow.
Results: The initial measurements with the method yielded excellent results, showing submillimeter matching in mechanical-vs-radiological isocenters and peripheral isodose lines. Most excitingly, the technique for CBCT-guided trigeminal neuralgia treatments yielded < 0.5 mm isocenter deviation that cemented clinical workflow. Additional benefits of our technique is its low cost and ease of implementation with the consumable cost estimated to be $10.20. Since final dose distribution associated with different phantom constructs was embedded into the DICOM RTDose file, no special restrictions were placed for the film slabs if made locally.
Conclusion: A low-cost, high-functional, end-to-end test procedure is developed and demonstrated for the first time. Implementations of the technique across modalities including carbon machines are underway with results forthcoming.
Not Applicable / None Entered.