The effect of exposure technique on image quality and radiation dose from CT simulation image of chest (phantom study)
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Abstract
Introduction: Computed tomography simulation imaging is a processing for treatment plan that may cause patients high radiation dose receiving. Thus, exposure techniques variation could reduce dose risk.
Objectives: Purpose of this study was to study effect of exposure technique on image quality and radiation dose (CTDIvol and effective dose) from CT simulation image of chest.
Materials and methods: Exposure parameters (tube voltage, tube current and slice thickness) were varied to achieve low radiation dose with equal reference image quality (120 kVp, 100 mAs). In this study, chest phantom was used. Scanning parameters were 90, 120,140 kVp, in which each kVp was varied to 50, 100, 150 mAs and slice thickness at 3 mm and 5 mm were tested. CTDIvol from each scan was recorded. Effective dose of chest and breast was calculated by impact scan program. Image noise was measured in lung and heart regions. Image quality was evaluated by 2 radiation oncologists.
Results: The results showed that kVp and mAs were affected to radiation dose. mAs was direct proportional to while kVp increased radiation dose. In addition, image noise measured in heart and lung region with increasing kVp or mAs, were reduced. Moreover, 3 mm-slice thickness showed higher noise than 5 mm-slice thickness.
Conclusion: The recommended exposure parameters for computed tomography simulation assessed by radiation oncologists were 140 kVp, 50 mAs for 3 mm- and 5 mm-slice thickness, respectively. The radiation dose reduced 26.35% (5.92 to 4.36 mGy) from reference exposure technique. Effective dose of chest and breast were 0.7 and 0.57 mSv, respectively.
Bull Chiang Mai Assoc Med Sci 2016; 49(2): 245-254. Doi: 10.14456/jams.2016.16
Article Details
Personal views expressed by the contributors in their articles are not necessarily those of the Journal of Associated Medical Sciences, Faculty of Associated Medical Sciences, Chiang Mai University.
References
2. Editorial. Incident and trends in the occurrence of cancer in Asia. Thai Cancer Journal 2014; 34: 55. (in Thai)
3. Titipong Kaewlek. Evaluation of image quality and lens’s radiation dose of cranial CT scan by spiral CT at various mAs settings. [Master degree thesis]. Bangkok: Mahidol University; 2005.
4. Reid J, Gamberoni J, Dong F, Davros W. Optimization of kVp and mAs for pediatric low-dose simulated abdominal CT: is it best to base parameter selection on object circumference. AJR Am J Roentgenol 2010; 195: 1015-20.
5. Yoon H, Kim MJ, Yoon CS, Choi J, Shin HJ, Kim HG, et.al. Radiation dose and image quality in pediatric chest CT: effects of iterative reconstruction in normal weight and overweight children. Pediatr Radiol 2015; 45: 337-44.
6. Rezazadeh S, Co SJ, Bicknell S. Reduced kilovoltage in computed tomography-guided intervention in a community hospital: effect on the radiation dose. Can Assoc Radiol J 2014; 65: 345-51.
7. ImPACT. CTDosimetry version 1.0.4. Medical Physic department, St Gorege’s Hospital, London; 2011.
8. Rasband W. ImageJ. The Research Services Branch, National Institute of Mental Health, Bethesda, Maryland, USA.
9. Mutic S, Jatinder R P, Elizabeth K B, Indra J D, Saiful M H, Leh-Nien D L, et.al. Quality Assurance for Computed-tomography Simulators and the Computed-tomography-simulation. Report of the AAPM Radiation Therapy Committee Task No.66. Med. Phys 2003; 30: 2762-92.
10. AAPM Computed Tomography Radiation Dose Education Slides. [Internet]. 2014 November 19 [cited 2014 Nov 19]; Available from: http://www.aapm.org/pubs/CTProtocols/documents/EducationSlides .pptx.
11. Cynthia M, Dianna C, Sue E, Rich G, Bob G, Nicholas K, et.al. The Measurement Reporting and Management of Radiation Dose in CT. American Association of Physicists in Medicine AAPM report no.96. College Park, MD: 2008.
12. Henry K, Usman B, et al. Computed tomography dose index. Available at http://radiopaedia.org/ articles/ct-dose-index-1. Accessed November 18, 2014.
13. Mahadevappa M. MDCT Physics: The Basics: Technology, Image Quality and Radiation Dose. [Internet]. 2014 November 11 [cited 2014 Nov 11]; Available from: https://books.google.co.th/ books?id=TH_sMhXgzx AC&printsec=frontcover&dq= MDCT+Physics.
14. Kihong Son, Seungryong C, Jin Sung K, Youngyih H, Sang G J, Doo H C. Dose Length Product. [Internet]. 2014 November 18 [cited 2014 Nov 18]; Available from: http://www.jacmp.org/index.php/ jacmp/rt/printerFriendly/ 4556/html_ 60.
15. Manus Mongkolsuk. X-ray computed tomography: Principle of Physics, Technique and Image Quality. 1st Edition. KhonKaen: Klangnanavittaya; 2003. (in Thai)
16. Paul M S. Multislice computed tomography.1st ed. California USA; 2002.
17. Edyvean S. Effect of ROI Size on Image Noise. [Internet]. 2014 November 19 [cited 2014 Nov 19]; Available from: http://www.ctug.org.uk/ meet04-01-13/roi_size_image_noise.pdf.