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6CCVD Research

Correction factors for diode and diamond detectors in the measurement of small field output factors, using film dosimetry as reference

At a Glance

Section titled ā€œAt a Glanceā€
MetadataDetails
Publication Date2018-07-25
JournalBiomedical Physics & Engineering Express
AuthorsAlexander F. I. Osman, Wassim Jalbout
InstitutionsAmerican University of Beirut Medical Center, American University of Beirut
Citations1

Abstract

Section titled ā€œAbstractā€

The accurate measurement of field output factors at small field sizes typically encountered in SRS and IMRT is challenging. In this study we measured detector output ratios for small fields using a range of detectors and orientations, we then calculated correction factors for each detector using film dosimetry as reference to obtain field output factors. The calculated correction factors were compared to the ones from TRS 483. Detectors used were: EBT3 Gafchromic film, PTW semiflex 31010 chamber, PTW pinpoint 31016 chamber, PTW diamond (used in two different orientations) and PTW SRS 60018 diode. Photon beam energies were 6 MV flat and 7 MV FFF with square field sizes from 0.5 to 10.0 cm side. Semiflex and pinpoint chambers agreed well with film down to 2.0 cm field size but under-responded by up to 40% at 0.5 cm field size. At 0.5 cm field size, diamond with stem parallel to beam axis under-estimated field output factors by up to 6.2%; diamond with stem perpendicular to beam axis over-estimated field output factors by up to 1.5% and diode over-estimated field output factors by up to 6.5%. Calculated correction factors, in general, agreed with and confirmed those given in TRS 483 film is an acceptable alternative to Monte Carlo simulation for deriving correction factors for solid state detectors. For field sizes smaller than 1.0 cm, diamond detector with stem perpendicular to beam axis was the most adequate for field output factor measurement, although not recommended in TRS 483.

Tech Support

Section titled ā€œTech Supportā€

Original Source

Section titled ā€œOriginal Sourceā€

References

Section titled ā€œReferencesā€
  1. 2014 - Output correction factors for nine small field detectors in 6 MV radiation therapy photon beams: a PENELOPE Monte Carlo study [Crossref]
  2. 2017 - Spectral distribution of particle fluence in small field detectors and its implication on small field dosimetry [Crossref]
  3. 2011 - Radiochromic film dosimetry: past, present, and future [Crossref]
  4. 2004 - Dosimetric properties of improved GafChromic films for seven different digitizers [Crossref]
  5. 2005 - Precise radiochromic film dosimetry using a flat-bed document scanner [Crossref]
  6. 2011 - Experimental comparison of seven commercial dosimetry diodes for measurement of stereotactic radiosurgery cone factors [Crossref]
  7. 2009 - Determination of output factors for stereotactic radiosurgery beams [Crossref]

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