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The Initial Experience with the CyberKnife G4 System at Stanford University Cheng Yu, Anthony Lo, David Djajaputra Stanford University Medical Center, Stanford, CA Objectives: The second CyberKnife, a G4 system, went live at Stanford University Cancer Center on Oct. 17, 2006. The CyberKnife G4 platform is built on a new linear accelerator with a dose rate of 600 MU/min that is 50% higher than the previous generation, the CyberKnife G3, potentially reducing treatment times. The new CyberKnife G4 also features flush-mounted, in- floor x-ray detectors, providing a significant increase in treatment workspace and further expanding the potential for extracranial applications. Our experience with the CyberKnife G4 system, as well as a comparison to our CyberKnife G3 system, will be presented in this report. Methods: In the first month of operation, 42 patients with 50 lesions and 95 fractions were treated with the CyberKnife G4 system. Pathologic diagnoses included acoustic neuroma, meningioma, pituitary adenoma, malignant glioma, trigeminal neuralgia, metastases, and others. Of all lesions, 37 were treated with 6D skull tracking, eight with Xsight tracking, and five with Synchrony tracking. The mean number of fractions per lesion was two (range: one to five). The mean lesion volume was 15.2 cm3 (range of 0.02 to 78.6 cm3), and the mean prescription was 25.6 Gy (range: 8 to 60 Gy) to the 78% isodose line (range: 70-82%). Accuracy of beam delivery, system efficiency, Estop interruption, machine downtime, customer support, and treatment planning system were analyzed. Results: Treatment in all patients was delivered as planned. The end-to-end accuracy was 0.38 mm for 6D skull tracking, 0.34 mm for fiducial tracking, 0.05 mm for spinal skeleton tracking, and 0.34 mm for Synchrony tracking. Improvements for the G4 system include an increase in treatment workspace, higher dose rate, enhanced power-up and power-down. However, the average time was approximately 90 min (range: 60 to 180 min) for treatment delivery, which was significantly longer compared to our G3 system. Cause of extended treatment time was identified after extensive investigations with Accuray. Conclusion: The CyberKnife G4 system offers the latest technology for frameless stereotactic radiosurgery. Our initial experience with this new CyberKnife G4 system was generally very positive.

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The Initial Experience with the CyberKnife G4 System at Stanford University

Cheng Yu, Anthony Lo, David Djajaputra

Stanford University Medical Center, Stanford, CA

Objectives: The second CyberKnife, a G4 system, went live at Stanford University Cancer Center on Oct. 17, 2006. The CyberKnife G4 platform is built on a new linear accelerator with a dose rate of 600 MU/min that is 50% higher than the previous generation, the CyberKnife G3, potentially reducing treatment times. The new CyberKnife G4 also features flush-mounted, in-floor x-ray detectors, providing a significant increase in treatment workspace and further expanding the potential for extracranial applications. Our experience with the CyberKnife G4 system, as well as a comparison to our CyberKnife G3 system, will be presented in this report.

Methods: In the first month of operation, 42 patients with 50 lesions and 95 fractions were treated with the CyberKnife G4 system. Pathologic diagnoses included acoustic neuroma, meningioma, pituitary adenoma, malignant glioma, trigeminal neuralgia, metastases, and others. Of all lesions, 37 were treated with 6D skull tracking, eight with Xsight tracking, and five with Synchrony tracking. The mean number of fractions per lesion was two (range: one to five). The mean lesion volume was 15.2 cm3 (range of 0.02 to 78.6 cm3), and the mean prescription was 25.6 Gy (range: 8 to 60 Gy) to the 78% isodose line (range: 70-82%). Accuracy of beam delivery, system efficiency, Estop interruption, machine downtime, customer support, and treatment planning system were analyzed.

Results: Treatment in all patients was delivered as planned. The end-to-end accuracy was 0.38 mm for 6D skull tracking, 0.34 mm for fiducial tracking, 0.05 mm for spinal skeleton tracking, and 0.34 mm for Synchrony tracking. Improvements for the G4 system include an increase in treatment workspace, higher dose rate, enhanced power-up and power-down. However, the average time was approximately 90 min (range: 60 to 180 min) for treatment delivery, which was significantly longer compared to our G3 system. Cause of extended treatment time was identified after extensive investigations with Accuray.

Conclusion: The CyberKnife G4 system offers the latest technology for frameless stereotactic radiosurgery. Our initial experience with this new CyberKnife G4 system was generally very positive.