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. 2014 Apr;4(2):130-8.

Design and construction of an optical computed tomography scanner for polymer gel dosimetry application

Seyed Salman Zakariaee  1 , Asghar Mesbahi  2 , Ahmad Keshtkar  1 , Vahid Azimirad  3
Affiliations

Design and construction of an optical computed tomography scanner for polymer gel dosimetry application

Seyed Salman Zakariaee et al. J Med Signals Sens. 2014 Apr.

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.

Keywords: Optical computed tomography; polymer gel dosimetry; two-dimensional imaging system.

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Conflict of interest statement

Conflict of Interest: None declared

Figures

Figure 1
Figure 1
(a) Photocell, (b) Photocells response function, (c) The circuit board of the detection system consists of analog to digital converter, (d) Dual-axis circuit board with L298 and L297, (e) Constructed mechanical system for sample motion
Figure 2
Figure 2
(a) The schematic of the sample motion procedure. (b) Two-dimensional scanning algorithm. Sample had N steps in rotational motion and X steps in horizontal direction. Scans are always done from first step to the last
Figure 3
Figure 3
(a) The samples which scanned in order to determine the system spatial resolution. (b) The samples which scanned in order to investigate the system contrast resolution
Figure 4
Figure 4
The schematic representation of gel irradiation setup, polyethylene phantom and gel vials used in the current study
Figure 5
Figure 5
Designed and constructed optical computed tomography system
Figure 6
Figure 6
The reconstructed image from the sample which was used to investigate the uniformity of system
Figure 7
Figure 7
The reconstructed images of the samples which scanned in order to determine the system spatial resolution. (a) The sample with 1 mm diameter. (b) The sample with 2 mm diameter. (c) The sample with 3 mm diameter. (d) The sample with 6 mm diameter
Graph 1
Graph 1
Contrast determined by our new system versus contrast determined by spectrophotometer of polymer gel vials
Figure 8
Figure 8
The reconstructed images of the samples which scanned in order to determine the system contrast resolution. (a) The un-irradiated sample. (b) The sample with 1 Gy irradiation. (c) The sample with 3 Gy irradiation. (d) The sample with 5 Gy irradiation. (e) The sample with 7 Gy irradiation. (f) The sample with 9 Gy irradiation
See this image and copyright information in PMC

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