Author

Avi Hameroff

Document Type

Honors Capstone Project

Date of Submission

Spring 5-1-2009

Capstone Advisor

Edward Lipson

Honors Reader

Andrzej Krol

Capstone Major

Physics

Capstone College

Arts and Science

Audio/Visual Component

no

Capstone Prize Winner

no

Won Capstone Funding

no

Honors Categories

Sciences and Engineering

Subject Categories

Biological and Chemical Physics | Physics

Abstract

An important application of William Röntgen’s discovery of x-rays is computed tomography (CT). First developed in the 1970’s, CT scanners of today are able to provide a detailed image of a patient’s body with minimal risk to patient and a very short turnaround time from scan to reconstructed image. This powerful tool provides physicians another way to diagnose patients while simultaneously allowing for researchers to learn about the human body.

Scientists soon became interested in using the technology on small animals but practical issues plagued the widespread use of CT in preclinical research. The scale of the scanners was simply too large to provide useful images of the animals, mainly mice and rats. As a direct result of this problem, the field of micro-CT was developed. Micro-CT scanners can be used to generate images of small animals in while the platform itself has been used to develop advancements applied to clinical CT.

In February 2006, the Syracuse Medical Imaging Research Group (SMIRG) acquired a Siemens Micro CAT II scanner. At the time, only theoretical predictions of dose to small animals existed and they were based in part on computer models.

It became necessary to perform a dosimetry study of the micro-CT scanner in order to empirically determine the dose to small animals during a scan. Utilizing materials and the method outlined by the SUNY Upstate Medical University Department of Radiation Safety, the study was successfully completed in May 2008. In order to measure exposure, thermoluminescent dosimeters (TLDs) were calibrated using an ionization chamber and then exposed in-air to obtain conversion factors. The TLDs were then exposed inside of a phantom. Post phantom exposure measurements were converted into kerma measurements which were finally converted into dose estimates using the f-factor for mice.

Mathematical equations which can predict dose estimates to small animals during scanning were developed. The equations, one for each of three filter thicknesses, allow the researcher to input their scan’s technique (peak voltage and current applied to the tube, and exposure time) and obtain an empirically-derived prediction of dose to the subject. This project provided a powerful tool to researchers and proved that dose to animals during micro-CT scanning, while small, is not insignificant. In addition, it also validated earlier dose predictions which were developed using computer models.

Creative Commons License

Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 3.0 License.

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