Phantom-Based Dosimetric Comparison of Helical and Fixed-Beam TomoTherapy for Spatially Fractionated Radiotherapy...

Area of Science:

• Radiation Oncology
• Medical Physics
• Cancer Treatment

Background:

• Spatially Fractionated Radiotherapy (SFRT) creates heterogeneous dose distributions for bulky tumors.
• TomoTherapy platform studies for SFRT, particularly comparing GRID and lattice vertex designs, are limited.
• Optimizing SFRT delivery techniques is crucial for effective cancer management.

Purpose of the Study:

• To evaluate the dosimetric performance of GRID and lattice vertex designs using TomoHelical and TomoDirect techniques on the TomoTherapy platform.
• To compare the effectiveness of different SFRT configurations in terms of dose distribution, normal tissue sparing, and delivery efficiency.

Main Methods:

• A phantom-based study simulated medium- and large-sized tumors with cylindrical GRID and spherical lattice vertices.
• Treatment plans were generated using TomoHelical and TomoDirect techniques with identical prescription criteria (15 Gy in a single fraction).
• Dosimetric parameters (PVDR, PEDR, V30%, V50%, conformity, homogeneity) and delivery accuracy (gamma passing rates) were assessed.

Main Results:

• All plans met prescription and delivery accuracy requirements (>95% gamma passing rate).
• TomoHelical demonstrated superior dose modulation (higher PVDR, PEDR), better conformity, and reduced V50% compared to TomoDirect.
• Lattice designs yielded higher PVDR than GRID, while TomoDirect offered shorter beam-on times but with greater dose variability.

Conclusions:

• TomoHelical delivery with lattice designs provides optimal dose modulation and normal tissue sparing for SFRT, albeit with longer treatment times.
• GRID designs facilitate quicker treatment delivery on the TomoTherapy platform.
• Findings offer practical guidance for optimizing SFRT planning and delivery on TomoTherapy.