PARENT SESSION
1:30 PM to 3:30 PM
Wednesday, April 24, 2002
Poster Session 30 Bystander Effects
Room: Nevada Exhibition Center

(P35-339) New Developments and Experiments using the Gray Laboratory Charged-Particle Microbeam.

Vojnovic, Borivoj¹, Prise, Kevin¹, Gilchrist, Stuart¹, Newman, Heidi¹, Tartier, Laurence², Michael, Barry¹, Folkard, Melvyn^*,1, ¹ Gray Cancer Institute, Northwood, Middlesex² CNRS

ABSTRACT-
The Gray Laboratory charged-particle microbeam facility has been substantially refurbished to enhance its performance. Developments have been made to the cell imaging system, the image processing and overall experimental control to improve the speed and versatility of the cell finding procedure. Other developments, such as changes to the collimator positioning system have been designed to dramatically improve the throughput of cells during the irradiation phase (a throughput of nearly 10,000 cells per hour is now achieved, with developments to increase this to 20,000 underway). A new beam line monitoring arrangement has also been installed prior to the collimator to provide both an optical and an electronic indication of the beam profile. The microbeam facility continues to be used for a diverse range of experiments. The improved cell throughput is of particular benefit to recent studies of radiation-induced genomic instability in primary human fibroblasts and lymphocytes, where up to 6000 cells per dish may be individually targeted. At the other extreme, studies related to the bystander effect require a few, or just a single cell to be exposed. Bystander studies in particular require the cells to be free of unwanted stress factors, therefore new cell imaging and beam finding strategies have been implemented to further reduce UV exposure of the cell and to eliminate exposure of the cell dish to the small radiation dose that previously occurred when beam-finding. Consequently, we now have results using 1MeV and 3.2MeV protons for both the direct (where every cell is targeted) and bystander (where only one cell is targeted) responses, both showing a plateau at about 95% survival after five proton traversals of one cell. Most recently, experiments using fluorescent antibody staining (using markers such as H2AX) to highlight regions of DNA damage within individual cells have also proved to be a good method of verifying the targeting accuracy of the microbeam.

KEYWORDS: microbeam, charged-particle, bystander effect, alpha-particles