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Quality assurance and independent dosimetry for an intraoperative x-ray device.
Eaton, D J.
Affiliation
  • Eaton DJ; Radiotherapy Physics, Royal Free Hospital, London NW3 2QG, UK. davideaton@nhs.net
Med Phys ; 39(11): 6908-20, 2012 Nov.
Article in En | MEDLINE | ID: mdl-23127084
PURPOSE: Quality assurance is an essential component of accurate and safe radiotherapy delivery, and should include measurements which are independent of manufacturer-provided calibration. However, the physical and dosimetric properties of the INTRABEAM compact mobile 50 kV x-ray source are different from conventional kilovoltage therapy units and few reports describe methods for independent checks, frequencies, or tolerances for quality assurance tests. METHODS: Based on the available evidence and local experience, methods are described for determination of the key dosimetric parameters: beam quality, output, isotropy, and depth doses. Internal system checks are also described, along with measurements of long-term stability. RESULTS: A small volume parallel plate ionization chamber in a liquid water tank is the gold standard for measurements with this unit, but solid water-equivalent materials, thermoluminescent dosimeters and radiochromic film can all be used as practical alternatives with an accuracy of 5%-10%. The main cause of measurement uncertainty is positioning of the detector in the steep dose gradient, but energy dependence should also be considered. CONCLUSIONS: A quality assurance schedule with suggested tolerances is proposed, which includes both internal tests, before each treatment and on a monthly basis, and independent tests every year or after servicing or recalibration.
Subject(s)

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Radiometry Type of study: Health_economic_evaluation Language: En Journal: Med Phys Year: 2012 Document type: Article Country of publication: United States

Full text: 1 Collection: 01-internacional Database: MEDLINE Main subject: Radiometry Type of study: Health_economic_evaluation Language: En Journal: Med Phys Year: 2012 Document type: Article Country of publication: United States