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Laboratory Device for Demonstrating Medical Imaging in the Classroom

Abstract

In this paper, we describe the details of the experimental setup developed with the objective of demonstrating the principles of tomography using visible light. Most tomographic methods use invisible forms of radiation (e.g., x-rays or ultrasound) and therefore it is not very instructive to see them in operation. The proposed setup consists of a translucent object illuminated by a simple white-light source and imaged with the digital camera at different angles. Collimation is provided by using a readily available telecentric lens to perform the imaging. This eliminates the need for a collimated light source, which can increase the cost of the system, and which usually involves hazardous sources such as lasers or laser diodes. By using visible light, students can observe the whole process directly. The students can control the image acquisition parameters and observe the reconstruction process on a computer. In this paper we focus on providing detailed design information so that the experimental setup can be reproduced by interested educators. A separate paper[3] discusses the educational issues relating to the proposed experiment including assessment results.

Introduction

In computed tomography (CT) the cross sectional distribution of some property of an object is reconstructed from a large number of line integrals of that distribution measured at many different angles and radial positions[4]. Stepper For example, x-ray CT provides images of the distribution motor of x-ray attenuation coefficient. X-rays have a desirable property to travel through tissue with negligible refraction. Shaft Therefore, line integrals of x-ray attenuation coefficient coupler distribution can be easily estimated by measuring the intensity of x-rays transmitted thorough the object[1]. Phantom For a student demonstration x-rays are not convenient because they are invisible and hazardous. To circumvent this problem we have developed an experiment that uses visible light, allowing students to directly observe the process and eliminating any hazards. To eliminate refraction (which is not negligible for visible light) the Figure 1. A photograph of the phantom phantom object is designed from translucent material assembly illuminated by the light box. The translucent phantom object is (acrylic plastic) and immersed within a refractive-index- immersed within a square tank with a matching fluid. The phantom is rotated by a stepper motor stepper motor mounted on top. The and imaged by a digital camera from many different angles. phantom is coupled to the motor shaft An uncollimated light source is used for illumination and with the shaft coupler. the collimation is achieved by using a telecentric lens.

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Wernick, M., & Lukic, A. (2006, June), Laboratory Device For Demonstrating Medical Imaging In The Classroom Paper presented at 2006 Annual Conference & Exposition, Chicago, Illinois. 10.18260/1-2--611