Lesion Load Matters: Low-dose Spillage, Oar Impact, and Delivery Efficiency Across Robotic Radiosurgery, Ring-gantry, and C-arm Modalities in Multimetastatic Brain Stereotactic Radiotherapy.

چکیده اصلی

AIMS: Retrospective comparative dosimetric evaluation using anonymized patient datasets for stereotactic brain radiotherapy delivered using robotic radiosurgery, ring-gantry helical delivery, and C-arm linear accelerator-based volumetric modulated arc therapy (VMAT), with particular emphasis on the impact of increasing intracranial lesion number on low-dose spillage and organ-at-risk exposure. MATERIALS AND METHODS: Treatment plans were generated using clinically contoured intracranial metastases derived from patient datasets, with lesion-burden scenarios ranging from 1 to 20 lesions across all platforms. Ring-gantry plans were created using a 2.5 cm field width. VMAT with both single- and multi-isocenter approaches in coplanar and noncoplanar configurations were used. All plans were prescribed 27 Gy in three fractions and optimized to achieve 100% of the dose to 98% of the planning target volume (PTV). Dosimetric endpoints included low-dose spillage volumes (V5Gy, V10Gy, V12Gy, and V15Gy) and V20Gy for the whole brain. Additional organ at risk (OAR) doses to the hippocampus, brainstem, and optic apparatus were evaluated. Treatment efficiency was assessed using monitor units and beam-on time. RESULTS: Clinically acceptable target coverage was achieved across all platforms. Increasing lesion number led to a progressive increase in low-dose spillage across all techniques, with distinct platform-specific trends. CyberKnife demonstrated lower low-dose spillage but required substantially longer treatment times, whereas VMAT provided efficient delivery for higher lesion counts but showed greater increases in V5-V15 Gy with increasing lesion burden. CONCLUSION: Lesion burden was strongly associated with low-dose spillage and OAR exposure in multilesion brain stereotactic radiotherapy. These findings provide comparative dosimetric insights within the evaluated treatment platforms and may support individualized planning decisions when balancing low-dose exposure and delivery efficiency.

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