Evaluation of the Sun Nuclear SRSMapCHECK for Patient-Specific Quality Assurance On the ZAP-X Radiosurgery Machine
Y Lei1*, C Jenkins2, M Halfman1, Q Xu3, P Rojas Castillo1, X Yan1, S Wang4, (1) Barrow Neurological Institute, Phoenix, AZ, (2) Zap Surgical Systems, Inc., San Carlos, CA, (3) Inova Schar Cancer Institute, Fairfax, VA, (4) University of Nebraska Medical Center, Omaha, NE
Presentations
PO-GePV-T-383 (Sunday, 7/10/2022) [Eastern Time (GMT-4)]
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Purpose: To evaluate a high-resolution detector array (Sun Nuclear SRS MapCHECK(SRSMC)) for patient-specific quality assurance(PSQA) on ZAP-X Gyroscopic Radiosurgery platform.
Methods: We performed the SRSMC array calibration and absolute dose calibration using the maximum 25mm ZAP-X field size(FS). The array response homogeneity test was checked by irradiating the SRSMC under a 10x10cm² FS with a Varian TrueBeam. The SRSMC array beam angle dependence, MU linearity relative to the ion chamber (up to 200 MUs) and array FS output correction factors were tested with the 25mm FS. Then two phantom-based test plans and PSQA plans of seven recently treated patients were created on the CT images of the SRSMC inside the SNC StereoPHAN. The plans were delivered and compared with the ZAP-X treatment planning system calculations with gamma analysis. The SRSMC PSQA results were also compared with film-based PSQA results obtained using the CyberKnife ball cube phantom.
Results: The response homogeneity test shows that 99.2% of detectors in SRSMC have a response difference lower than ±0.5%; 100% of them had a difference of less than 0.7%. The array shows significant angular dependence as large as 14% from lateral and post-lateral beam directions. The angular dependence correction factors for the SRSMC in the SNC-Patient software showed improved post-lateral beam responses but diminished frontal direction responses. The array MU linearity relative to ion chamber results is less than 2% up to 3 MU. For all seven PSQA plans, the SRSMC measurements showed an average gamma passing rates of 94.4% compared to 96.9% for film based PSQA method (2%/2mm-criteria applied to both).
Conclusion: The dosimetric characteristics of SRSMC on the ZAP-X has been evaluated and the SRSMC-based PSQA results were found to be comparable with film-based methods. This shows that SRSMC could be a convenient replacement for film-based results for the ZAP-X Radiosurgery Platform.
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