Presentation Title

Laser Sourced Computed Tomography

Format of Presentation

Poster to be presented the Friday of the conference

Abstract

Computed tomography (CT) has been used for decades by medical professionals to detect and diagnose various injuries and ailments. CT scanners are teeming with interesting physics, but due to their bulk, cost and safety, hands on experience with a medical CT scanner is unrealistic for undergraduate students. Therefore, an operationally similar, yet small, safe and inexpensive CT scanner is desirable. This poster details the design and operation of one such apparatus. First, the medical CT’s X-rays were replaced by light, a far safer type of radiation. A 5-mW laser was the light source and a photodetector sensed the light once it has passed through a scan subject. Pyrex glass was chosen as the scan object. Glass was used because a key property of CT scanning is to differentiate densities by their absorption characteristics, so scanning an object which obscures the laser light is not sufficiently similar to medical CT. A consequence of that choice was that laser light interacting with glass resulted in significant refraction. In order to minimize the refraction, the glass was bathed in mineral oil, which has the same index of refraction as Pyrex. With that taken care of, the next step was image reconstruction. Keeping in line with the low-cost goal the image reconstruction program was written in R, an open source programming language. The program takes data from the absorption of the light transmitted through the object at various positions and forms an image based on locations of high or low absorption.

Department

Physics

Faculty Advisor

Mark Paetkau

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Laser Sourced Computed Tomography

Computed tomography (CT) has been used for decades by medical professionals to detect and diagnose various injuries and ailments. CT scanners are teeming with interesting physics, but due to their bulk, cost and safety, hands on experience with a medical CT scanner is unrealistic for undergraduate students. Therefore, an operationally similar, yet small, safe and inexpensive CT scanner is desirable. This poster details the design and operation of one such apparatus. First, the medical CT’s X-rays were replaced by light, a far safer type of radiation. A 5-mW laser was the light source and a photodetector sensed the light once it has passed through a scan subject. Pyrex glass was chosen as the scan object. Glass was used because a key property of CT scanning is to differentiate densities by their absorption characteristics, so scanning an object which obscures the laser light is not sufficiently similar to medical CT. A consequence of that choice was that laser light interacting with glass resulted in significant refraction. In order to minimize the refraction, the glass was bathed in mineral oil, which has the same index of refraction as Pyrex. With that taken care of, the next step was image reconstruction. Keeping in line with the low-cost goal the image reconstruction program was written in R, an open source programming language. The program takes data from the absorption of the light transmitted through the object at various positions and forms an image based on locations of high or low absorption.