Implementation and Dosimetric Evaluation of a Kv Microbeam X-Ray Irradiation Platform
Abstract
Purpose
The purpose of this study was to implement and experimentally characterize a kV microbeam X-ray irradiation platform, with emphasis on spatial dose modulation and dosimetric suitability for future radiobiological applications. Spatially Fractionated Radiation Therapy (SFRT) delivers non-uniform dose distributions. Among SFRT techniques, Microbeam Radiation Therapy (MRT) produces high-dose peaks separated by low-dose valleys enabling tumor control while preserving normal tissue function.
Methods
A tungsten microbeam collimator consisting of 31 parallel slits was implemented in an orthovoltage X-ray irradiator operating in the 50–200kVp energy range with added filtration. The collimator was positioned at the central axis of the beam and produced nominal microbeam widths of 40 μm with a center-to-center spacing of 400μm. Custom 3D-printed holders ensured precise and reproducible alignment within the beam path. Spatial dose distributions were measured using radiochromic films (EBT3 and EBT-XD), which were compared in terms of spatial resolution and dynamic range for peak and valley dose assessment. Additional measurements investigated the influence of tube voltage, filtration, and backscatter materials. Finally, percentage depth dose measurements and in-vitro cell irradiation experiments conducted comparing microbeam and continuous irradiation fields.
Results
Clear and reproducible microbeam dose profiles were obtained, resolving an average of 30 microbeams per profile. The measured FWHM was 152μm, with a mean center-to-center spacing of 638μm. Peak doses ranged from approximately 8 to 18Gy, while valley doses remained below 1Gy. Peak-to-valley dose ratios (PVDR) ranged from 15 to 34 depending on the analysis method. Peak dose uniformity across the field was high, with a coefficient of variation of 21%, demonstrating well-defined spatial dose modulation.
Conclusion
This work demonstrates the feasibility of experimentally delivering and characterizing kV microbeam X-ray fields with high spatial precision and large PVDR values. The developed platform provides a robust technical foundation for future depth-dose characterization and preclinical microbeam radiobiology studies.