Dosimetric Comparison of ZAP-X and CyberKnife Stereotactic Radiosurgery for Single Brain Metastasis
J Wang1, L Pan2, B Qu1, M Bodduluri3, X Dai1, Z Ju1, C Wang1, J Bai1, S Xu1*, (1) Department of Radiation Oncology, the First Medical Center of PLA General Hospital, Beijing, BJ, CN, (2) Department of Neurosurgery, the First Medical Center of PLA General Hospital. Beijing, BJ, CN, 3)Zap Surgical Systems, Inc. San Carlos, CA, USA,
Presentations
PO-GePV-T-379 (Sunday, 7/25/2021) [Eastern Time (GMT-4)]
Purpose: To evaluate the dosimetric characteristics of ZAP-X and CyberKnife (CK) G4 stereotactic radiosurgery (SRS) for single brain metastasis.
Methods: Ten patients with single brain metastasis treated with CK were re-planned in the ZAP-X planning system using the same prescribed dose. The prescribed dose of planning target volume (PTV) was 20-24Gy for 1-3 fractions. The PTV volumes ranged from 0.68-11.52 cm(3).The same target and organs at risk (OARs) constraints were used, and the prescription dose of PTV was normalized to 70% for both ZAP-X and CK. The dosimetric parameters and total MUs, treatment time (TT) were evaluated for PTV and normal structures. A paired t-test was performed to show the significance of difference.
Results: For coverage, CK is significantly higher than ZAP-X (98.89±0.89% vs 97.69±1.54%，p<0.01)，but ZAP-X shows a higher conformity index (0.80 ±0.05 vs 0.77±0.08)，and a lower Paddick gradient index (2.97±0.26 vs 3.04±0.24) than CK. Because all the prescribed doses of PTV are normalized to 70%, the plans have the same HI. The total MUs of ZAP-X are significantly lower than CK (12159.9 ±5423.0 vs 25940.1 ±2752.3, p<0.01) and shows shorter TT than ZAP-X (25.67 ±6.67 vs 37.89 ±4.94 min) (p<0.01). For V2-V21 and Dmean of brain tissues，there are no significant differences between two modalities, but ZAP-X have a little lower than CK. But CK may have a certain advantage for the target close to OARs, such as lens, due to no function of avoiding certain organs in ZAP-X.
Conclusion: For SRS treating single brain metastasis, ZAP-X can provide a high quality plan equivalent to or even better than CK,especially reducing the treatment time. ZAP-X may become a new SRS platform for the treatment of brain metastasis.
Funding Support, Disclosures, and Conflict of Interest: This work was partially supported by a grant from Chinese National Science Fund(Grant No.81801799)
Keywords
Brain, Dose, Radiation Therapy
Taxonomy
TH- External Beam- Photons: cyberknife
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