Impact of Optimization Resolution and Dose Calculation Grid Size in Small-Field Stereotactic Body Radiotherapy Using Flattening-Filter-Free Beams for Hepatocellular Carcinoma

Thirunavukkarasu, Moorthi; Khanna, D; Balaji, Karunakaran; Ramachandran, Mohan

doi:10.31557/APJCP.2026.27.3.1115

Impact of Optimization Resolution and Dose Calculation Grid Size in Small-Field Stereotactic Body Radiotherapy Using Flattening-Filter-Free Beams for Hepatocellular Carcinoma

Document Type : Research Articles

Authors

¹ Department of Physics, Karunya Institute of Technology and Sciences, Coimbatore, India.

² Department of Radiation Oncology, Gleneagles Hospitals, Chennai, India.

³ Department of Oncology, Iswarya Hospital, Chennai, India.

⁴ Mediclinic Middle East, Dubai Healthcare City, Dubai, United Arab Emirates.

10.31557/APJCP.2026.27.3.1115

Abstract

Objective: This study aims to evaluate the impact of optimization and calculation resolutions in SBRT for hepatocellular carcinoma (HCC) using flattening-filter-free photon beams. Methods: The SBRT plans were created in the Eclipse TPS using 6X-FFF and 10X-FFF MV photon beams, prescribed with a hypofractionated dose of 50 Gy in 5 fractions. A total of 4 plans were created for each energy with different combinations of optimization (O) and calculation (C) resolutions, viz. O1.25-C1.25, O1.25-C2.5, O2.5-C1.25, and O2.5-C2.5, using computed tomography (CT) images of fifteen HCC patients. The optimization and calculation times were noted for comparison among all plans. The plans were evaluated based on the PTV, organs at risk, and delivery efficiency dosimetric parameters, and a plan quality score was computed for each plan. Results: This study revealed that the 10X-FFF beams provided better results compared to 6X-FFF. The integrated scoring method revealed that the O1.25-C1.25 plan achieved better results for OARs, while O1.25-C2.5 plan achieved better results for PTV. Further, the optimization and calculation times, and phantom study results were better with 2.5 mm resolution plans. Conclusion: The 1.25 mm resolution for both optimization and calculation was found to be better if the critical organs are in prioritized; otherwise, the 2.5 mm resolution setting is the optimal choice for liver SBRT using the 10X-FFF beam.

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