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Title: SU-F-T-434: Development of a Fan-Beam Optical Scanner Using CMOS Array for Small Field Dosimetry

Abstract

Purpose: To design and construct a second generation optical computed tomography (OCT) system using a fan-beam with a CMOS array detector for the 3D dosimetry with polymer gel and radiochromic solid dosimeters. The system was specifically designed for the small field dosimetry. Methods: The optical scanner used a fan-beam laser, which was produced from a collimated red laser beam (λ=620 nm) with a 15-degree laser-line generating lens. The fan-beam was sent through an index-matching bath which holds the sample stage and a sample. The emerging laser light was detected with a 2.54 cm-long CMOS array detector (512 elements). The sample stage rotated through the full 360 degree projection angles at 0.9-degree increments. Each projection was normalized to the unirradiated sample at the projection angle to correct for imperfections in the dosimeter. A larger sample could be scanned by using a motorized mirror and linearly translating the CMOS detector. The height of the sample stage was varied for a full 3D scanning. The image acquisition and motor motion was controlled by a computer. The 3D image reconstruction was accomplished by a fan-beam reconstruction algorithm. All the software was developed inhouse with MATLAB. Results: The scanner was used on both PRESAGE andmore » PAGAT gel dosimeters. Irreconcilable refraction errors were seen with PAGAT because the fan beam laser line refracted away from the detector when the field was highly varying in 3D. With PRESAGE, this type of error was not seen. Conclusion: We could acquire tomographic images of dose distributions by the new OCT system with both polymer gel and radiochromic solid dosimeters. Preliminary results showed that the system was more suited for radiochromic solid dosimeters since the radiochromic dosimeters exhibited minimal refraction and scattering errors. We are currently working on improving the image quality by thorough characterization of the OCT system.« less

Authors:
; ;  [1];  [2];  [3]
  1. Department of Radiation Oncology, University of Minnesota, Minneapolis, MN (United States)
  2. Department of Physics, Vel Tech University, Chennai (India)
  3. (Mexico)
Publication Date:
OSTI Identifier:
22649027
Resource Type:
Journal Article
Resource Relation:
Journal Name: Medical Physics; Journal Volume: 43; Journal Issue: 6; Other Information: (c) 2016 American Association of Physicists in Medicine; Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
60 APPLIED LIFE SCIENCES; 61 RADIATION PROTECTION AND DOSIMETRY; COMPUTER CODES; COMPUTERIZED TOMOGRAPHY; DOSEMETERS; DOSIMETRY; ERRORS; GELS; IMAGE PROCESSING; LASERS; RADIATION DOSE DISTRIBUTIONS; VISIBLE RADIATION

Citation Formats

Brost, E, Warmington, L, Watanabe, Y, Senthilkumar, S, and Departamento de Ingeneria Fisica, DCI, Universidad de Guanajuato, Campus Leon, Guanajuato. SU-F-T-434: Development of a Fan-Beam Optical Scanner Using CMOS Array for Small Field Dosimetry. United States: N. p., 2016. Web. doi:10.1118/1.4956619.
Brost, E, Warmington, L, Watanabe, Y, Senthilkumar, S, & Departamento de Ingeneria Fisica, DCI, Universidad de Guanajuato, Campus Leon, Guanajuato. SU-F-T-434: Development of a Fan-Beam Optical Scanner Using CMOS Array for Small Field Dosimetry. United States. doi:10.1118/1.4956619.
Brost, E, Warmington, L, Watanabe, Y, Senthilkumar, S, and Departamento de Ingeneria Fisica, DCI, Universidad de Guanajuato, Campus Leon, Guanajuato. Wed . "SU-F-T-434: Development of a Fan-Beam Optical Scanner Using CMOS Array for Small Field Dosimetry". United States. doi:10.1118/1.4956619.
@article{osti_22649027,
title = {SU-F-T-434: Development of a Fan-Beam Optical Scanner Using CMOS Array for Small Field Dosimetry},
author = {Brost, E and Warmington, L and Watanabe, Y and Senthilkumar, S and Departamento de Ingeneria Fisica, DCI, Universidad de Guanajuato, Campus Leon, Guanajuato},
abstractNote = {Purpose: To design and construct a second generation optical computed tomography (OCT) system using a fan-beam with a CMOS array detector for the 3D dosimetry with polymer gel and radiochromic solid dosimeters. The system was specifically designed for the small field dosimetry. Methods: The optical scanner used a fan-beam laser, which was produced from a collimated red laser beam (λ=620 nm) with a 15-degree laser-line generating lens. The fan-beam was sent through an index-matching bath which holds the sample stage and a sample. The emerging laser light was detected with a 2.54 cm-long CMOS array detector (512 elements). The sample stage rotated through the full 360 degree projection angles at 0.9-degree increments. Each projection was normalized to the unirradiated sample at the projection angle to correct for imperfections in the dosimeter. A larger sample could be scanned by using a motorized mirror and linearly translating the CMOS detector. The height of the sample stage was varied for a full 3D scanning. The image acquisition and motor motion was controlled by a computer. The 3D image reconstruction was accomplished by a fan-beam reconstruction algorithm. All the software was developed inhouse with MATLAB. Results: The scanner was used on both PRESAGE and PAGAT gel dosimeters. Irreconcilable refraction errors were seen with PAGAT because the fan beam laser line refracted away from the detector when the field was highly varying in 3D. With PRESAGE, this type of error was not seen. Conclusion: We could acquire tomographic images of dose distributions by the new OCT system with both polymer gel and radiochromic solid dosimeters. Preliminary results showed that the system was more suited for radiochromic solid dosimeters since the radiochromic dosimeters exhibited minimal refraction and scattering errors. We are currently working on improving the image quality by thorough characterization of the OCT system.},
doi = {10.1118/1.4956619},
journal = {Medical Physics},
number = 6,
volume = 43,
place = {United States},
year = {Wed Jun 15 00:00:00 EDT 2016},
month = {Wed Jun 15 00:00:00 EDT 2016}
}