Enhanced Lattice Radiation Therapy for Bulky Tumors：a Comparative Study between Dual–Layer and Single–Layer Mlc VMAT
Abstract
Purpose
This study compared the performance of the dual-layer multileaf collimator (DLM) system of the Halcyon 3.0 accelerator with the single-layer multileaf collimator (SLM) system of the TrueBeam accelerator for treating bulky tumors using two lattice radiation therapy (LRT) approaches.
Methods
Nineteen patients with bulky tumors were retrospectively analyzed. Gross tumor volume (GTV) and organs at risk (OARs) were delineated based on CT-fused MRI images. Spherical lattice vertices were generated within the GTV using automated contouring software (vertex diameter: 1.2–1.5 cm; spacing: 3.6–4.5 cm) to create the lattice target volume (LTV). Two planning approaches were designed for each accelerator: the Lattice SBRT (L-SBRTDLM and L-SBRTSLM) and Standalone Lattice (LRTDLM and LRTSLM). All plans used 6 MV Flattening-Filter-Free (FFF) beams and multi-arc Volumetric Modulated Arc Therapy (VMAT), ensuring 95% of the LTV received 100% of the prescribed dose.
Results
DLM plans exhibited higher D2% and V110%, along with a lower GI within the LTV, compared to SLM plans (all p 0.05) but significantly reduced Dmean and D50% (all p < 0.001). LRTDLM plans demonstrated significantly higher PVDR (p < 0.001) compared to LRTSLM plans, whereas no significant difference was observed between the two platforms in the Lattice SBRT approach (p = 0.171). Despite requiring higher monitor units (MUs) and longer delivery times (DT), DLM plans demonstrated reduced Dmean and integral dose (ID) to normal tissues as well as reduced plan complexity.
Conclusion
The DLM system showed equivalent or superior PVDR, improved OAR sparing, and reduced plan complexity compared to the SLM system. Although requiring higher MUs and longer DT, these advantages support its clinical use for LRT.