Dr. Geoffrey S. Ibbott
The University of Texas MD Anderson Cancer Center
Department of Radiation Physics
An area of active research for a number of years has been the development and evaluation of a polymerizing gel dosimeter. The practice of radiation oncology has evolved as a result of the availability of equipment and techniques that facilitate the production of complex dose distributions. However, the physical dosimetry has lagged behind. A polymerizing gel dosimetry system has been developed (MGS Research, Inc., Guilford CT) and is based on radiation-induced chain polymerization of acrylic monomers dispersed in a tissue-equivalent gel. During recent years, the dosimeter has been refined and improved by my collaborators and myself, and its value has been demonstrated in a number of areas including verification of placement of stereotactic beams, quantitative dosimetry, and demonstration of dose distributions around brachytherapy sources.
Most prior work has depended on MR imaging of the gel to measure dose distributions, but recently, optical imaging has been investigated. The student would participate in determination of the optical characteristics of the gel to optimize imaging, and determination of dosimetric characteristics such as dose linearity, dose rate dependence and energy dependence. A variation of the dosimeter to simulate lung tissue is also being evaluated.
Several projects are under way to evaluate optically-stimulated luminescence (OSL) dosimeters. These dosimeters will be used in the RPC’s remote audit program, and might ultimately be incorporated into the RPC’s anthropomorphic phantoms.
Evaluation of the RPC’s phantoms under new and untested conditions is an ongoing task. In the near future, several phantoms will be evaluated in proton beams. A modification to the thorax phantom to simulate respiratory
motion is being considered.
Program in Medical Physics
Office: MDA Y2.5629f (Unit 94)
Ph.D. - Colorado State University - 1993