Gyroscopic radiosurgery-based lattice therapy for intracranial tumors: A dosimetric study

Lattice therapy, a novel technique within spatially fractionated radiation therapy, demonstrates considerable potential for the management of challenging tumors, such as recurrent glial tumors and bulky brain metastases, which are often refractory to conventional radiotherapy approaches. However, current platforms, such as CyberKnife®, face limitations in generating lattice therapy plans, particularly regarding treatment duration, and the optimal technique remains undefined. This study evaluates the feasibility of implementing lattice therapy for intracranial tumors using the ZAP-X gyroscopic radiosurgery system. Simulation computed tomography (CT) images from 7 glioblastoma patients were used to design lattice therapy plans. A custom Python script automated the generation of lattice vertices with a spherical diameter of 1 cm and a center-to-center spacing of 3 cm. Treatment planning was performed on the ZAP-X system, delivering 20 Gy to lattice vertices using a 10 mm collimator. Dosimetric indices, including conformity index (CI), gradient index (GI), homogeneity index (HI), and peak-to-valley dose ratio (PVDR), were evaluated. Patient-specific quality assurance (QA) was performed through ion chamber and Gafchromic film measurements. The ZAP-X system efficiently created lattice therapy plans within clinically acceptable treatment durations, with a median duration of 42 minutes (range: 35 to 77 minutes). Dosimetric analysis showed CI values ranging from 1.04 to 1.55, HI values between 1.11 and 1.28, and PVDRs spanning 4.5 to 5.3, indicating precise and heterogeneous dose distributions. QA results demonstrated agreement between planned and measured doses within ± 3% and confirmed the accurate positional alignment of lattice vertices. The ZAP-X system's high dose rate and gyroscopic design enabled efficient and precise lattice therapy delivery for intracranial tumors, overcoming limitations of alternative systems like CyberKnife®. Favorable dosimetric and QA results support its potential for treating large or recurrent intracranial tumors. Future studies should focus on clinical outcomes, toxicity profile, and integration with systemic therapies.