Design and Construction of an Optical Computed Tomography Scanner for Polymer Gel Dosimetry Application

Abstract

Polymer gel dosimeter is the only accurate three dimensional (3D) dosimeter that can measure the absorbed dose distribution in
a perfect 3D setting. Gel dosimetry by using optical computed tomography (OCT) has been promoted by several researches. In the
current study, we designed and constructed a prototype OCT system for gel dosimetry. First, the electrical system for optical scanning of
the gel container using a Helium-Neon laser and a photocell was designed and constructed. Then, the mechanical part for two rotational
and translational motions was designed and step motors were assembled to it. The data coming from photocell was grabbed by the
home-built interface and sent to a personal computer. Data processing was carried out using MATLAB software. To calibrate the system
and tune up the functionality of it, different objects was designed and scanned. Furthermore, the spatial and contrast resolution of the
system was determined. The system was able to scan the gel dosimeter container with a diameter up to 11 cm inside the water phantom.
The standard deviation of the pixels within water flask image was considered as the criteria for image uniformity. The uniformity of the
system was about ±0.05%. The spatial resolution of the system was approximately 1 mm and contrast resolution was about 0.2%. Our
primary results showed that this system is able to obtain two-dimensional, cross-sectional images from polymer gel samples.