Dosimetric problems at low monitor unit settings for scanned and scattering foil electron beams

Indra J. Das, James C. Harrington, Syed F. Akber, Alan F. Tomer, James C. Murray, Chee Wai Cheng

Research output: Contribution to journalLetter

9 Scopus citations

Abstract

Electron beam dosimetry at low monitor unit (MU) settings is important for dosimetric applications. Dose linearity, beam flatness, and beam energies were studied at low MU settings with various dose rates for different types of linear accelerators. It is observed that for the scattering foil units, the dose/MU is a smooth function of MU for all beam energies. Discrepancies in dose/MU are highest at the lowest MU. Significant variation (5%-245%) in dose linearity is observed among various linear accelerators at low MU settings. Dose rate has no effect on the dose linearity for all energies for the scattering foil units tested. On the contrary, for the scanned beam, there is no predictable pattern as dose/MU is random in nature and varies with time and beam energy. The maximum dosimetric error is observed for the highest energy beam where the beam width is most narrow. Using film, the beam uniformity was noticed to be very poor at low MU and high energy for scanned beams. The beam uniformity and dose linearity are random at low MU due to the random nature of the scan cycle. Under the adverse conditions, the deviation in dosimetric parameters was observed up to 200 MU.

Original languageEnglish (US)
Pages (from-to)821-826
Number of pages6
JournalMedical physics
Volume21
Issue number6
DOIs
StatePublished - Jun 1 1994

Keywords

  • dose linearity
  • electron beam
  • end effect
  • monitor unit
  • scanned beam
  • scattering foil

ASJC Scopus subject areas

  • Biophysics
  • Radiology Nuclear Medicine and imaging

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    Das, I. J., Harrington, J. C., Akber, S. F., Tomer, A. F., Murray, J. C., & Cheng, C. W. (1994). Dosimetric problems at low monitor unit settings for scanned and scattering foil electron beams. Medical physics, 21(6), 821-826. https://doi.org/10.1118/1.597328