Document Detail

Variations in daily quality assurance dosimetry from device levelling, feet position and backscatter material.
MedLine Citation:
PMID:  23208619     Owner:  NLM     Status:  Publisher    
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.
Abdurrahman Ceylan; Martin Butson; Ashley Cullen; Peter K N Yu; Hani Alnawaf
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Publication Detail:
Type:  JOURNAL ARTICLE     Date:  2012-12-4
Journal Detail:
Title:  Australasian physical & engineering sciences in medicine / supported by the Australasian College of Physical Scientists in Medicine and the Australasian Association of Physical Sciences in Medicine     Volume:  -     ISSN:  0158-9938     ISO Abbreviation:  Australas Phys Eng Sci Med     Publication Date:  2012 Dec 
Date Detail:
Created Date:  2012-12-4     Completed Date:  -     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8208130     Medline TA:  Australas Phys Eng Sci Med     Country:  -    
Other Details:
Languages:  ENG     Pagination:  -     Citation Subset:  -    
Illawarra Shoalhaven Cancer Network, Wollongong Hospital, Crown St, Wollongong, NSW, 2500, Australia.
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