Author: Minbin Chen, Gang Liu, Manju Liu, Weiwei Sang, Pulin Sun, Mingyuan Ye, Fang-Fang Yin, Lihua Zhang, Haiming Zhu 👨🔬
Affiliation: Jiahui International Hospital, Radiation Oncology, Cancer Center, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Medical Physics Graduate Program, Duke Kunshan University, Duke Kunshan University, The First People's Hospital of Kunshan 🌍
Purpose: This study aims to conduct a dosimetric comparison between lattice radiotherapy (LRT) and 3D grid treatment planning techniques, focusing on their differences in delivering three-dimensional spatially-fractionated radiotherapy(SFRT) using volume-modulated arc therapy (VMAT).
Methods: Three patients with tumor volumes of 135cc, 1510cc and 1720cc (lung, breast, and liver cases) were studied. Two SFRT approaches were compared: the 3D lattice with 1cm diameter spheres spaced cm apart and the 3D grid with 1cm diameter cylinders spaced cm apart. Both lattice/grid volumes received 60Gy in 4 fractions, while the whole PTV received 20Gy. Two VMAT plans (LRT and 3D grid) were created for each patient using Varian Eclipse V15 with a 6X beam. Plan evaluation included Dmax, Dmean, equivalent uniform dose (EUD), D10%, D50%, D90%, and D95% of the lattice/grid volumes and whole PTVs. Organ-at-risk (OAR) doses were also assessed.
Results: The VMAT LRT and 3D grid plans produced comparable dosimetric outcomes across all three cases. The VMAT LRT plan achieved higher average Dmax, Dmean, D90% and D50% values, with slight differences in D10% and D95%. In the larger volume breast and liver cases, the 3D grid plans exhibited greater dose heterogeneity and lower EUD. However, in the smaller volume lung case, the trends were reversed, with the LRT plan showing greater heterogeneity and lower EUD. Regarding OAR doses, both plans demonstrated similar protective efficacy in the lung case. In the liver case, the 3D grid plan reduced high-dose region in OARs, whereas in the breast case, the LRT plan resulted in a lower overall OAR dose.
Conclusion: This study indicates that 3D grid plans provide dosimetric performance comparable to lattice plans, with tumor size potentially influencing the choice of approach. Additionally, the consistency of the EUD results with previous studies highlights the reliability of both SFRT planning techniques.