Advancing Targeted Radiation with Microdosimetry in BNCT

Boron neutron capture therapy (BNCT) represents a sophisticated, highly selective cancer treatment modality. However, traditional dose calculation often relies on fixed relative biological effectiveness (RBE) values. These static numbers frequently fail to account for variations in beam quality and specific tumor biology. To overcome these limitations, researchers recently developed a physics-based alternative. This framework utilizes Microdosimetry in BNCT to predict cell survival more accurately by coupling PHITS lineal energy calculations with the microdosimetric kinetic (MK) model.

The research team derived MK parameters for critical cell lines, including U87 glioblastoma and SAS human squamous carcinoma. Notably, they used low linear energy transfer (LET) datasets to calibrate the model. Specifically, the framework successfully reproduced in-vitro survival curves for various charged particles. Furthermore, the model maintained high accuracy when researchers applied it to neutron fields from different sources. This included thermal neutron beams from reactors and epithermal sources from cyclotrons or linear accelerators.

Clinical Impact of Microdosimetry in BNCT on Treatment Planning

The findings demonstrate that predicted RBE values at 10% survival (RBE₁₀) align closely with experimental measurements. Consequently, this method allows for spectrum-specific and cell-line-specific estimations of biological effects. Moving away from fixed RBE and compound biological effectiveness (CBE) values is essential for clinical safety. Therefore, spectrum-aware quantities can significantly improve dose prescription and patient safety in oncology departments. For instance, the framework can guide the design of new neutron beams by providing preliminary RBE estimates before the construction of expensive shaping assemblies.

Moreover, the integration of this model supports the ongoing development of indigenous BNCT technologies in India. Recent breakthroughs in local accelerator-based systems highlights the need for precise dosimetry tools. Ultimately, incorporating intracellular boron microdistribution in future iterations will further refine CBE estimates. This evolution will enhance the overall biological accuracy of BNCT treatment planning for aggressive or radio-resistant tumors.

Frequently Asked Questions

How does microdosimetry improve BNCT safety?

Microdosimetry accounts for the specific energy deposition at the cellular level. By replacing fixed RBE values with spectrum-aware calculations, clinicians can avoid over- or under-dosing based on the unique characteristics of the neutron beam and the targeted tissue.

Can this model be used for different types of cancer?

Yes. The framework has already shown success in reproducing survival curves for glioblastoma, skin fibroblasts, and squamous carcinomas. Researchers can adapt the MK parameters for other cell lines as more data becomes available.

What role does the PHITS code play in this method?

The PHITS code calculates the lineal energy distributions of charged particles within the tissue. This physical data is then combined with biological kinetic models to predict how many cancer cells will survive a specific radiation dose.

Disclaimer: This content is for informational and educational purposes only. It does not constitute medical advice or a substitute for professional healthcare consultation. Refer to the latest local and national guidelines for clinical practice.

References

1. Yamazaki R et al. Development of a microdosimetry-based method to derive cell survival rates for evaluating the biological effects of BNCT. Biomed Phys Eng Express. 2026 Feb 11. doi: 10.1088/2057-1976/ae44a2. PMID: 41671591.

2. Sato T et al. Microdosimetric Modeling of Biological Effectiveness for Boron Neutron Capture Therapy Considering Intra- and Intercellular Heterogeneity in 10B Distribution. Sci Rep. 2018 Jan 17;8(1):988. doi: 10.1038/s41598-017-18871-0.

3. Saikia D et al. Design and optimisation of a neutron beam shaping assembly for AD-BNCT applications at Cotton University. Nucl Instrum Methods Phys Res B. 2025 Nov 12.