Iranian Journal of Medical Physics

Iranian Journal of Medical Physics

New Method of Quality Control Test for Light and Radiation Field Coincidence in Medical Linear Accelerators

Document Type : Original Paper

Authors
Mahdi Heravian Shandiz 1
Mohammad-Hossein Bahreyni-Toosi 2
Ghorban Safaeian Layen 3
Amir Hossein Ziaei 3
1 Medical Equipment Unit, Imam Reza Hospital, Mashhad University of Medical Sciences, Mashhad, Iran
2 Medical Physics Research Center, Faculty of Medicine, Mashhad University of Medical Sciences, Mashhad, Iran
3 Department of Technology of Radiology, School of Paramedical Science, Mashhad University of Medical Sciences, Mashhad, Iran
10.22038/ijmp.2019.21250.1202
Abstract
Introduction: The evaluation of X-ray and light field coincidence in linear accelerators as a quality control test is often performed subjectively, involving the manual marking of films and their visual inspection following the irradiation. Therefore, the present study aimed to develop an objective method for the performance of this test leading to the increased levels of accuracy, precision, and speed for the measurement of X-ray and light field coincidence.
Material and Methods: The new method involved a portable, lightweight, and inexpensive device containing optically-shielded and non-shielded photodiodes to detect the location and dimensions of the light and X-ray fields. The obtained results were analyzed using purpose-written user-friendly software.
Results: On the basis of the results, this system could be a reliable method to measure the coincidence of the two fields with the accuracy of 0.5 mm and average field size standard deviations of Elekta Presice and Siemens Primus are 22.47 mm2 and 22.36 mm2, respectively. The result was well within the tolerance recommended by the American Association of Physicists in Medicine task group report number 142.
Conclusion: The proposed method allows accurate and precise measurements through a largely automated process. Therefore, the measurement results benefit from the reduced level of subjectivity or human error, compared to the standard film-based technique. 
Keywords
Quality Control
Quality Assurance
Radiation
Subjects

  1.  

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Iranian Journal of Medical Physics
Volume 16, Issue 5 - Serial Number 5
September and October 2019
Pages 336-340

  • Receive Date 18 November 2017
  • Revise Date 09 May 2019
  • Accept Date 14 May 2019