A Tabletop Platform for In Vitro Irradiation with Low-Energy Electron Bunches
Abstract
Purpose
Low-energy electron (LEE) beams in the kilo-electronvolt (keV) range are expected to exhibit an increased relative biological effectiveness (RBE) due to their high linear energy transfer and limited penetration depth. Emerging laser accelerator-on-a-chip concepts could enable delivery of such electron bunches in minimally invasive clinical scenarios. This work investigates the radiobiological effects of pulsed LEE irradiation and compares them to conventional X-ray exposure.
Methods
Cells were irradiated using an ultrafast pulsed electron source based on photoemission from an array of gold needle tips, delivering electron energies up to 50 keV. Human primary fibroblasts and multiple tumor cell lines were exposed either to LEE or to reference radiation from a conventional 120 kVp X-ray tube. DNA double-strand breaks were quantified using γH2AX immunostaining. Clonogenic survival assays were performed to assess radiation-induced cell inactivation. Absorbed dose measurements were obtained using unlaminated EBT3 radiochromic films.
Results
LEE irradiation produced DNA damage patterns that differed quantitatively from those induced by X-rays. The depth distribution of DNA double-strand breaks was consistent with the finite penetration range of low-energy electrons in water. Highly localized and intense damage regions were observed, indicative of elevated linear energy transfer. Initial clonogenic survival data demonstrate that biological effectiveness of LEE radiation can be quantitatively compared to that of X-rays, enabling preliminary estimation of RBE values.
Conclusion
A reproducible experimental platform for in vitro irradiation with low-energy electron bunches was established. The observed damage patterns and survival data indicate distinct radiobiological characteristics of LEE compared to conventional photon irradiation. These results support further systematic investigation of LEE beams and their potential application in highly localized radiation therapy using laser accelerator-on-a-chip technology.