Impact of Optimization Resolution and Dose Calculation Grid Size in Small-Field Stereotactic Body Radiotherapy Using...

Area of Science:

• Medical Physics
• Radiation Oncology
• Radiotherapy Planning

Background:

• Stereotactic body radiation therapy (SBRT) is a key treatment for hepatocellular carcinoma (HCC).
• Flattening-filter-free (FFF) photon beams offer dosimetric advantages in SBRT.
• The impact of varying optimization and calculation resolutions on SBRT plan quality for HCC requires detailed evaluation.

Purpose of the Study:

• To assess the influence of different optimization and calculation resolutions on SBRT plan quality for HCC.
• To compare the dosimetric outcomes and plan quality between 6X-FFF and 10X-FFF beams.
• To determine the optimal resolution settings for liver SBRT.

Main Methods:

• SBRT plans were generated for 15 HCC patients using Eclipse TPS with 6X-FFF and 10X-FFF beams.
• Four resolution combinations (1.25 mm and 2.5 mm for optimization and calculation) were tested.
• Plans were evaluated based on PTV coverage, organs at risk (OARs) sparing, delivery efficiency, and a composite plan quality score.

Main Results:

• 10X-FFF beams demonstrated superior performance compared to 6X-FFF beams.
• The 1.25 mm optimization/1.25 mm calculation (O1.25-C1.25) plan excelled in OAR sparing.
• The 1.25 mm optimization/2.5 mm calculation (O1.25-C2.5) plan showed better PTV coverage, while 2.5 mm resolution plans generally reduced planning and calculation times.

Conclusions:

• For liver SBRT with 10X-FFF beams, 1.25 mm resolution for both optimization and calculation is recommended when prioritizing OAR sparing.
• A 2.5 mm resolution setting is considered optimal for liver SBRT when faster planning and calculation times are desired, balancing plan quality.
• The choice of resolution depends on the specific clinical priorities for HCC treatment planning.