Lattice Radiotherapy: Influence of Parameters on Dose Distribution
Abstract
Purpose
The radius and spacing of high-dose spheres (HDS) in Lattice Radiotherapy (LRT) used by clinicians varies considerably This study quantifies how changing these parameters impacts dosimetric characteristics (such as peak-to-valley dose ratio (PVDR) and mean dose).
Methods
Four combinations of radius and spacing were investigated, using radii of 0.5 and 0.75 cm with spacings of 3.0 and 4.5 cm. A Python-based script was developed to generate HDS structures with geometric fidelity directly on patient CT datasets. The HDS structures were arranged in a face-centered cubic configuration to maximize the number of spheres within the target volume. To isolate the effects of radius and spacing, VMAT treatment plans were generated for each configuration using identical arc geometry, optimization parameters, and ring structures surrounding each sphere.
Results
Changing the spacing from 4.5 to 3.0 cm produced larger dosimetric effects than changing sphere radius from 0.75 to 0.5 cm, including increased isodose overlap between spheres, PVDR, mean HDS dose, and hotspot magnitude. Decreasing spacing reduced PVDR from 3.18 to 1.82, whereas increasing sphere radius resulted in only a minor reduction in PVDR from 3.24 to 3.18. The lattice effect was maximized for smaller radius (R) and larger spacing (S), where R = 0.5 cm and S = 4.5 cm yielded the highest PVDR, highest maximum HDS dose, and lowest HDS density.
Conclusion
This study showed that spacing of HDS has a greater influence than radius on dose characteristics. It also revealed consistent trends in how DVH metrics and PVDR vary with these parameters.