Partial Quality Assessment of ⁶⁰Co-Teletherapy Machine Performance

Mohammed A. Ali Omer^1,2

¹College of Medical Radiologic Science, Sudan University of Science and Technology, Khartoum, Sudan.
²Department of Radiologic Technology, College of Applied Medical Science, Qassim University, Buraidah, Saudi Arabia.

DOI: 10.4236/ojrad.2015.54032                

Abstract

The aim of this study was to assess the performance of ⁶⁰Co-teletherapy unit at Radiation and Isotopes Center in Khartoum, using the common tools used for quality control (Front pointer, Graphic paper, Pin, Non-screen film, meter and Check plate). The collected and analyzed data revealed that: there was a difference between the calculated theoretical field size (FS) and the measured one relative to the change of SSD; and the average FS shift was 0.9 cm relative to the standard one, while the machine isocenter was almost fixed at 0° with a shift of 0.003 cm, which was within the standard limit (0.2 cm). The diaphragm isocenter showed a shift of ±0.36 cm (i.e. in clock and anti clock wise) in average relative to standard limit (±0.3 cm) and the couch vertical isocenter (CVI) relative to the SSD changes was exceeded the standard limit (0.2 cm) by a factor of 0.9 cm. Also the SSD determined by the optical distance indicator was greater than the actual SSD (determined by Front pointer and measured by scale meter) by an average of 0.8 cm; which exceeded the limit (0.3 cm) by an average factor of 0.5 cm. The study also showed that the penumbra profile (1.5 cm) was less than the actual specified for ⁶⁰Co-teletherapy machine, while the radiation beam was so homogeneous across the field size.

Keywords

⁶⁰Co-Quality, Control, Teletherapy, Radiotherapy, Assurance

Conflicts of Interest

The authors declare no conflicts of interest.

References

[1]	Zhu, X.R. (2000) Entrance Dose Measurements for in-Vivo Diode Dosimetry: Comparison of Correction Factors for Two Types of Commercial Silicon Diode Detectors. Journal of Applied Clinical Medical Physics, 1, 100-107. http://dx.doi.org/10.1120/1.308253
[2]	ICRU (1976) Determination of Absorbed Dose in a Patient Irradiated by Beams of x or Gamma Rays in Radiotherapy Procedures. ICRU Report 24, Bethesda, Maryland and Washington DC.
[3]	Huang, K., Bice Jr., W.S. and Hidalgo-Salvatierra, O. (2003) Characterization of an in Vivo Diode Dosimetry System for Clinical Use. Journal of Applied Clinical Medical Physics, 4, 132-142. http://dx.doi.org/10.1120/1.1559920
[4]	International Commission on Radiological Protection (ICRP) (2000) Prevention of Accidental Exposure to Patients Undergoing Radiation Therapy. International Commission on Radiological Protection, Oxford.
[5]	Podgorsak, E.B. (2005) Radiation Oncology Physics: A Handbook for Teachers and Students. IAEA, Vienna.
[6]	IAEA and International Society for Radiation Oncology ISRO (1995) Quality Assurance in Radiation Therapy. Proceedings of the Working Meeting on National Programmes: Design, Harmonisation and Structures, Vienna, 8-9 May 1995, 62.
[7]	Van, D.J. (2009) Commissioning and Implementing a Quality Assurance Programme for New Technologies. International Conference on Advances in Radiation Oncology (ICARO), Vienna, 27-29 April 2009, 21.
[8]	Nath, R., Anderson, L.L., Luxton, G., et al. (1995) Dosimetry of Interstitial Brachytherapy Sources: Recommendations of the AAPM Radiation Therapy Committee Task Group No. 43. Medical Physics, 22, 209-234. http://dx.doi.org/10.1118/1.597458
[9]	Rivard, M.J., Coursey, B.M., Dewerd, L.A., et al. (2004) Update of AAPM Task Group No. 43 Report: A Revised AAPM Protocol for Brachytherapy Dose Calculations (AAPM Report No. 84). Medical Physics, 25, 633-674. http://dx.doi.org/10.1118/1.1646040
[10]	Dam, V.J., Johansson, K.-A., Bridier, A. and Sernbo, G. (1993) EORTC Radiotherapy Group Quality Assurance: Mechanical Checks and Beam Alignment of Megavoltage Equipment. Radiotherapy and Oncology, 29, 91. http://dx.doi.org/10.1016/0167-8140(93)90231-V
[11]	Zeman, G.H. and Dooley, M.A. (1984) Performance and Dosimetry of Theratron-80 Co-60 Unit. Armed Forces Radiology Research Institute—AFRRI-Technical Report—Defense Nuclear Agency, Bethesda.
[12]	AAPM (American Association of Physicists in Medicine) (1984) Radiation Therapy Committee Task Group of Quality Assurance in Radiation Therapy. American Institute of Physics, New York.
[13]	Svensson, G.K. (1994) Physical Aspects of Quality Assurance in Radiation Therapy. AAPM Report No. 13, American Institute of Physics, New York.
[14]	Adams, E.J. and Warrington, A.P. (2008) A Comparison between Cobalt and Linear Accelerator-Based Treatment Plans for Conformal and Intensity-Modulated Radiotherapy. British Journal of Radiology, 81, 304-410. http://dx.doi.org/10.1259/bjr/77023750
[15]	Faiz, K.M. (2003) The Physics of Radiation Therapy. 3rd Edition, Lippincott Williams & Wilkins, Philadelphia.