title: Independent quality assurance of a helical tomotherapy machine using the dose magnifying glass.
abstract: OBJECTIVE
  Helical tomotherapy is a complex delivery technique, integrating CT image guidance and intensity modulated radiotherapy in a single system. The integration of the CT detector ring on the gantry not only allows patient position verification but is also often used to perform various QA procedures. This convenience lacks the rigor of a machine-independent QA process.
  
  
  METHODS
  In this article, a Si strip detector, known as the Dose Magnifying Glass (DMG), was used to perform machine-independent QA measurements of the multileaf collimator alignment, leaf open time threshold, and leaf fluence output factor (LFOF).
  
  
  RESULTS
  The DMG measurements showed good agreements with EDR2 film for the MLC alignment test while the CT detector agrees well with DMG measurements for leaf open time threshold and LFOF measurements. The leaf open time threshold was found to be approximately 20 ms. The LFOF measured with the DMG agreed within error with the CT detector measured LFOF.
  
  
  CONCLUSIONS
  The DMG with its 0.2 mm spatial resolution coupled to TERA ASIC allowed real-time high temporal resolution measurements of the tomotherapy leaf movement. In conclusion, DMG was shown to be a suitable tool for machine-independent QA of a tomotherapy unit.
authors.affiliation: Centre for Medical Radiation Physics, University of Wollongong, New South Wales 2522, Australia.
authors.forename: J H D
authors.initials: JH
authors.lastname: Wong
authors.forename: N
authors.initials: N
authors.lastname: Hardcastle
authors.forename: W A
authors.initials: WA
authors.lastname: Tomé
authors.forename: A
authors.initials: A
authors.lastname: Bayliss
authors.forename: R
authors.initials: R
authors.lastname: Tolakanahalli
authors.forename: M L F
authors.initials: ML
authors.lastname: Lerch
authors.forename: M
authors.initials: M
authors.lastname: Petasecca
authors.forename: M
authors.initials: M
authors.lastname: Carolan
authors.forename: P
authors.initials: P
authors.lastname: Metcalfe
authors.forename: A B
authors.initials: AB
authors.lastname: Rosenfeld
mesh_terms: D005898:Glass; D011786:Quality Control; D011829:Radiation Dosage; D011879:Radiotherapy Dosage; D011881:Radiotherapy, Computer-Assisted / Q000295:instrumentation* / Q000592:standards; D012825:Silicon; D014057:Tomography, X-Ray Computed
chemical_list: D012825:Silicon