Accession Number:

ADA446550

Title:

Design and Calibration of a X-Ray Millibeam

Descriptive Note:

Master's thesis

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH

Personal Author(s):

Report Date:

2005-12-01

Pagination or Media Count:

136.0

Abstract:

It has been generally accepted that genetic damage is caused by the deposition of energy within the nucleus of a cell, and the extent of this damage is approximately proportional to the absorbed dose the linear no-threshold dose-response model. However, recent experiments have shown that genetic alterations, cell death or transformation can occur in cells that receive no direct radiation at all - the so-called bystander effect. The goal of this project was to convert a broad-beam Hewlett-Packard HP 43 855B Faxitron x-ray machine into a millibeam configuration that can target small sections of a cell culture dish with a precise dose of radiation. This millibeam provides novel capabilities for radiobiological studies into the mechanisms underlying bystander effects caused by x-rays, a low linear energy transfer LET radiation. Air kerma and absorbed dose calibration factors for the HP Faxitron were developed for use in Fricke dosimetry, parallel-plate ionization chambers, Lithium Fluoride thermoluminescent dosimetry TLD, and EBT OafChromic film to characterize the spatial distribution and accuracy of the doses produced by the Faxitron. A new film scanning and analysis technique was developed using an off-the-shelf Canon 995OF 16-bit transmission scanner and the free Image software from the National Institute of Health. A multi-layer shield composed of lead and steel was designed to convert the 26.035 cm Faxitron x-ray beam into a millibeam that targets 10 to 60 of the area on a 9-cm diameter cell culture dish.

Subject Categories:

  • Radiobiology
  • Nuclear Physics and Elementary Particle Physics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE