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Variations in daily quality assurance dosimetry from device levelling, feet position and backscatter material

  • Abdurrahman Ceylan
  • Martin ButsonEmail author
  • Ashley Cullen
  • Peter K. N. Yu
  • Hani Alnawaf
Scientific Note
  • 117 Downloads

Abstract

Daily quality assurance procedures are an essential part of radiotherapy medical physics. Devices such as the Sun Nuclear, DQA3 are effective tools for analysis of daily dosimetry including flatness, symmetry, energy, field size and central axis radiation dose measurement. The DQA3 can be used on the treatment couch of the linear accelerator or on a dedicated table/bed for superficial and orthovoltage x-ray machines. This device is levelled using its dedicated feet. This work has shown that depending on the quantity of backscatter material behind the DQA3 device, the position of the levelling feet can affect the measured central axis dose by up to 1.8 % (250 kVp and 6 MV) and that the introduction of more backscatter material behind the DQA3 can lead to up to 7.2 % (6 MV) variations in measured central axis dose. In conditions where no backscatter material is present, dose measurements can vary up to 1 %. As such this work has highlighted the need to keep the material behind the DQA3 device constant as well as maintaining the accuracy of the feet position on the device to effectively measure the most accurate daily constancy achievable. Results have also shown that variations in symmetry and energy calculations of up to 1 % can occur if the device is not levelled appropriately. As such, we recommend the position of the levelling feet on the device be as close as possible to the device so that a constant distance is kept between the DQA3 and the treatment couch and thus minimal levelling variations also occur. We would also recommend having no extra backscattering material behind the DQA3 device during use to minimise any variations which might occur from these backscattering effects.

Keywords

Radiotherapy Quality assurance Dosimetry X-rays 

Notes

Acknowledgments

This study has been fully supported by a grant from the Research Grants Council of HKSAR, China (Project No. CityU 123810). Hani Alnawaf was supported by the Saudi Arabian Government.

References

  1. 1.
    Alaei P, Hui SK, Higgins PD, Gerbi BJ (2006) The use of a commercial QA device for daily output check of a helical tomotherapy unit. Med Phys 33(10):3680–3682PubMedCrossRefGoogle Scholar
  2. 2.
    Lim S, Ma SY, Jeung TS, Yi BY, Lee SH, Lee S, Cho SJ, Choi J (2012) Development of a one-stop beam verification system using electronic portal imaging devices for routine quality assurance. Med Dosim 37(3):296–304PubMedCrossRefGoogle Scholar
  3. 3.
    Millar M, Cramb J, Das R, Ackerly T, Brown G, Webb D (1997) ACPSEM position paper. Recommendations for the safe use of external beams and sealed brachytherapy sources in radiation oncology. Australasian College of Physical Scientists and Engineers in Medicine. Australas Phys Eng Sci Med 20(3 Suppl):1–35Google Scholar
  4. 4.
    Van de Vondel I, Tournel K, Verellen D, Duchateau M, Lelie S, Storme G (2009) A diagnostic tool for basic daily quality assurance of a Tomotherapy Hi*Art machine. J Appl Clin Med Phys 10(4):2972PubMedGoogle Scholar
  5. 5.
    Butson MJ, Cheung T, Yu PK (2008) Measuring energy response for RTQA radiochromic film to improve quality assurance procedures. Australas Phys Eng Sci Med 31(3):203–206PubMedCrossRefGoogle Scholar
  6. 6.
    Das IJ, Gazda MJ, Beddar AS (1996) Characteristics of a scintillator-based daily quality assurance device for radiation oncology beams. Med Phys 23(12):2061–2067PubMedCrossRefGoogle Scholar
  7. 7.
    Peng JL, Kahler D, Li JG, Amdur RJ, Vanek KN, Liu C (2011) Feasibility study of performing IGRT system daily QA using a commercial QA device. J Appl Clin Med Phys 12(3):3535PubMedGoogle Scholar
  8. 8.
    Butson MJ, Cheung T, Yu PKN (2007) Radiochromic film for verification of superficial x-ray backscatter factors. Australas Phys Eng Sci Med 30:269–273PubMedCrossRefGoogle Scholar

Copyright information

© Australasian College of Physical Scientists and Engineers in Medicine 2012

Authors and Affiliations

  • Abdurrahman Ceylan
    • 1
  • Martin Butson
    • 2
    • 3
    Email author
  • Ashley Cullen
    • 1
  • Peter K. N. Yu
    • 2
  • Hani Alnawaf
    • 3
  1. 1.Illawarra Shoalhaven Cancer NetworkWollongong HospitalWollongongAustralia
  2. 2.Department of Physics and Materials ScienceCity University of Hong KongKowloon TongHong Kong
  3. 3.Centre for Medical Radiation Physics and the Illawarra Health and Medical Research InstituteUniversity of WollongongGwynnevilleAustralia

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