Development and Dosimetric Characterization of an In Vitro Benchtop Americium 241 Alpha Irradiator Platform

To expand preclinical efforts aimed at understanding the unique radiobiology of high linear energy transfer alpha particles and their implications for cancer therapy, robust, accessible, and high-throughput in vitro alpha irradiation platforms are needed. Such platforms must be extensively characterized and validated to ensure rigor and reproducibility. Here, we describe the construction and dosimetric characterization of a benchtop in vitro alpha irradiation platform using an americium 241 (²⁴¹Am) source.

A square foil with embedded ²⁴¹Am was used as the alpha source (activity 3.3785 mCi). The source was secured in the roof of a custom housing incorporating a 3-dimensional printed microcapillary array collimator to exclude large-angle alpha particles, thereby narrowing the energy spectrum and improving homogeneity. A movable shelf accommodates cells grown on glass slides at variable distances from the source. Dosimetric characterization included direct measurement of dose homogeneity, source self-attenuation, energy spectra, absorbed dose, and dose rate.

The ²⁴¹Am source, when used in conjunction with the microcapillary array, provided a spatially uniform and geometrically stable irradiation field. The mylar entrance window resulted in predictable shifting and broadening of the alpha particle energy spectra. Absorbed dose and dose-rate measurements (5.815-7.721 mGy/s) demonstrated the feasibility of controlled in vitro alpha particle irradiation studies.

We established a turnkey, low-cost in vitro alpha irradiation platform suitable for high-throughput preclinical studies. The homogeneity, alpha particle energy spectra, absorbed dose, and dose rate were characterized and validated through direct measurements. Given the approximately 432-year half-life of ²⁴¹Am, this platform will provide stable and reliable dose rates for decades, facilitating long-term radiobiological investigations.