Title page for ETD etd-01142010-133415


Type of Document Master's Thesis
Author Robertson, Chad Joseph
Author's Email Address crobe56@tigers.lsu.edu,crobe56@gmail.com
URN etd-01142010-133415
Title Prototype Electron Phantom for Radiographic and Radiochromic Film Dosimetry
Degree Master of Science (M.S.)
Department Physics & Astronomy
Advisory Committee
Advisor Name Title
Price, Mich Committee Chair
Hogstrom, Kenneth Committee Member
Parker, Brent Committee Member
Sajo, Erno Committee Member
Stacy, Greg Committee Member
Keywords
  • solid water phantom
  • film phantom
  • radiochromic film
  • electron dosimetry
  • radiographic film
Date of Defense 2009-11-12
Availability unrestricted
Abstract
Robertson, Chad Joseph, B.S. Louisiana Tech University, 2006

Master of Science, Spring Commencement, 2006

Major: Medical Physics and Health Physics

Prototype Electron Phantom for Radiographic and Radiochromic Film Dosimetry

Thesis directed by Professor Kenneth R. Hogstrom

Pages in thesis, 133. Words in abstract, 350

ABSTRACT

Purpose: The purpose of this work is to develop a solid electron beam film phantom for use with

radiographic film (RGF) and radiochromic film (RCF) to measure relative dose distributions in a

principal plane containing the central axis for 6每20MeV electron beams. It was hypothesized that

relative dose distributions measured using film will agree with corresponding diode

measurements within ㊣2% of the central-axis maximum dose or ㊣1mm distance-to-agreement

(DTA).

Method and Materials: Three prototype film phantoms were designed at Mary Bird Perkins

Cancer Center and constructed by Gammex-RMI, Inc. Relative dose measurements, planar (2D)

dose distributions containing central-axis, were acquired in the phantom using both Kodak-XV

RGF and GafChromic-EBT RCF. Correspondingly, diode measurements were acquired utilizing

a Scanditronix-Wellhofer 2D-water phantom. For prototype 3, dose distributions were measured

at 100-cm SSD using a 15x15-cm2 field-size at 6, 9, 12, 16, and 20 MeV, as well as 2x2-cm2 and

4x4-cm2 field-sizes at 9 and 16 MeV. Relative dose differences were evaluated with respect to

regional criteria of acceptability: (1) high dose, low dose-gradient region (≒ 2 % dose), (2) high

dose-gradient region (≒ 2 mm DTA), and (3) low-dose, low dose-gradient region (≒ 2 % dose).

Results: RGF depth-dose measurements agreed with diode measurements within all criteria for

all measurements conditions. 2D dose distributions were in agreement with over 98% of

measured dose points agreeing within ㊣2% dose or ㊣1mm DTA for all energies (6每20MeV,

15x15-cm2). RCF depth-dose measurements agreed for all measurement conditions in all regions

excluding the build-up region (<1每2cm depth), where measurements were approximately 3每4%

low. 2D dose distributions reflected differences seen in the depth-doses with 90% of data points

within criteria.

Conclusion: With appropriate modifications, the prototype 3 phantom is capable of accurately

measuring relative electron dose distributions using RGF sufficiently for clinical use. RCF

measurements acquired in the same phantom consistently underestimated diode measurements

by 3每4% at depths <2-cm. The cause of this systematic error, believed to be a combination of

film-edge misalignment and RCF depth-dependency, must be resolved before prototype phantom

3 with appropriate modifications would be acceptable for clinical use.

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