Purpose: The purpose of this study is to provide an end-to-end validation of the capability of different radiotherapy modalities to treat challenging multi-lesion stereotactic radiosurgery (SRS) cases.
Methods: The study uses the CT simulation scan of a real patient, who was treated for five brain lesions ranging from 7-20 mm in diameter within 6 cm of isocenter. 20 Gy in a single fraction was prescribed to all lesions following the clinical protocol of UNC. Four treatment plans were produced using the following combinations of treatment planning software (TPS) and delivery machine: 1) Precision-CyberKnife (Accuray), 2) iPlan-Novalis (BrainLab), 3) Raystation-VersaHD (RaySearch Laboratories-Elekta), 4) Monaco-VersaHD (Elekta). Plans were delivered to a 3D-printed phantom emulating the specific patient’s anatomy while including a gel-dosimetry insert to derive the dose distribution.
Results: The conformity index values were 0.76, 0.79, 0.80 and 0.69, respectively (clinical goal: ≥0.70). All the plans failed to satisfy the constraint of V12Gy < 10cc for brain minus PTVs (Precision: 22.8cc, iPlan: 18.0cc, Raystation: 32.5cc, Monaco: 22.5cc). All the plans performed satisfactory regarding the constraint of D0.035cc < 15Gy for brainstem (Precision: 15.9cc, iPlan: 15.5cc, Raysation: 14.9cc, Monaco: 13.3cc). CyberKnife and VersaHD achieved clinically acceptable results for all the targets regarding 3D global gamma analysis (3%/2mm). More specifically, the 7mm, 9mm, 12mm, 15mm and 20mm lesions had passing rates of 100%, 99.5%, 99.3%, 98.6%, 95.9%, respectively for CyberKnife, 69.5%, 95.5%, 66.8%, 88.1%, 79.9% for Novalis, 100%, 100%, 100%, 99.8%, 94.9%, for VersaHD (Raystation), and 94.3%, 97.0%, 100%, 100%, 92.7% for VersaHD (Monaco).
Conclusion: All the plans were comparable in terms of quality, satisfying the requirements of the clinical protocol with some deviations within clinical acceptance. CyberKnife and VersaHD accurately delivered the corresponding radiosurgery plans for targets within 6cm of isocenter. Clinically acceptable gamma pass rates were achieved for all the lesion sizes.