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Development of an Electron Microbeam for Cell Culture Studies

This study focuses on developing an electron microbeam to investigate the impact of low-dose ionizing radiation on human health. By targeting specific locations with moderate energy electrons, the researchers aim to quantify bystander effects. The apparatus includes an electron source, accelerator tube, collimator assembly, and cell dish stage. Current experiments involve irradiating various cell lines to assess cytogenetic effects. Future directions include expanding the studies to different cell types and comparing results with ion microbeam data.

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Development of an Electron Microbeam for Cell Culture Studies

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  1. Development of an Electron Microbeam for Cell Culture Studies T. W. Botting, L. A. Braby, and J. R. Ford Texas A&M University

  2. Overview • Background • Construction • Operation • Current Experiments • Future

  3. Objective Our main objective is to achieve a better understanding of the risk to human health due to everyday exposure to low doses of ionizing radiation.

  4. Most occupational and public radiation exposures are due to x and g rays so concern is about the effects of small numbers of moderate energy electrons (10 to 1000 keV)

  5. How do we study this directly? • Need source for low-to-moderate energy electrons • Need method to deliver them exactly where desired • We have used an electron microbeam to try to quantify bystander effects produced by moderate energy electrons

  6. mbeam delivery of electron dose • Targeting • irradiation paths • discrete locations • Dose • duration • intensity • Energy

  7. Electron Beam Production • Electron source • low-power tungsten filament • low voltage power supply • isolation transformer • Accelerator Tube • custom-made 3-section ceramic • equipotential rings • high voltage power supply

  8. Beam Delivery • Collimator Assembly • capillary tube • swivel mounts for alignment • Cell dish stage • x-y motion control • Microscope and camera • targeting

  9. Electron Microbeam Apparatus Less than 4 feet high Capillary-style collimator Accelerator tube up to 100,000 Volts to produce up to 100keV electrons

  10. Source and Accelerator \ Faraday Cup control Turbo pump - Equipotential rings / - Accelerator tube Voltage dividers - - Source

  11. 3D Schematic

  12. Collimator Stand and Microscope CCD camera - Light Source / - Stage X-Y motion control | \ Capillary Collimator

  13. Cell culture dishes

  14. Final Construction Details • Voltage dividers • 30 MW per tube section for smooth gradient • Exit collimation • 5mm and 300mm exit aperatures • Exit window • 2mm thick mylar (same as cell dishes)

  15. Operation • Electron source • provides electron beam up to 1 nanoamp on the Faraday cup • Stable at up to 85 kV so far • beams at up to 90kV • Software control of targeting • line traces • discrete spots

  16. Desired Improvements • Beam stability • Beam current • Beam transmission

  17. Bystander Effect Experiments • Irradiate nearly confluent cells • CDKN1A and PCNA versus distance • AG 1522 human fibroblasts • Clone 9 rat liver line • RIE mouse intestine line • HBEC human primary bronchial cells • Micronuclei assay • AG 1522 human fibroblasts

  18. Some Future Directions… • Further micronuclei assays • Clone 9 rat liver line • RIE mouse intestine line • HBEC human primary bronchial cells • NTEC Rat primary tracheal cells • All three methods (CDKN1A, PCNA, micronuclei) • Complete comparison matrix with our positive ion mbeam results as a control

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