Monte Carlo dosimetry study of a 6 MV stereotactic radiosurgery unit

F. Verhaegen, I. J. Das, H. Palmans

Research output: Contribution to journalArticle

70 Citations (Scopus)

Abstract

Small-field and stereotactic radiosurgery (SRS) dosimetry with radiation detectors, used for clinical practice, have often been questioned due to the lack of lateral electron equilibrium and uncertainty in beam energy. A dosimetry study was performed for a dedicated 6 MV SRS unit, capable of generating circular radiation fields with diameters of 1.25-5 cm at isocentre using the BEAM/EGS4 Monte Carlo code. With this code the accelerator was modelled for radiation fields with a diameter as small as 0.5 cm. The radiation fields and dosimetric characteristics (photon spectra, depth doses, lateral dose profiles and cone factors) in a water phantom were evaluated. The cone factor (S(t)) for a specific cone c at depth d is defined as St(d, c) = D(d, c)/D(d, c(ref)), where c(ref) is the reference cone. To verify the Monte Carlo calculations, measurements were performed with detectors commonly used in SRS such as small-volume ion chambers, a diamond detector, TLDs and films. Results show that beam energies vary with cone diameter. For a 6 MV beam, the mean energies in water at the point of maximum dose for a 0.5 cm cone and a 5 cm cone are 2.05 MeV and 1.65 MeV respectively. The values of S(t) obtained by the simulations are in good agreement with the results of the measurements for most detectors. When the lateral resolution of the detectors is taken into account, the results agree within a few per cent for most fields and detectors. The calculations showed a variation of S(t) with depth in the water. Based on calculated electron spectra in water, the validity of the assumption that measured dose ratios are equal to measured detector readings was verified.

Original languageEnglish (US)
Pages (from-to)2755-2768
Number of pages14
JournalPhysics in Medicine and Biology
Volume43
Issue number10
DOIs
StatePublished - Oct 1998
Externally publishedYes

Fingerprint

Radiosurgery
Dilatation and Curettage
Dosimetry
dosimeters
Cones
cones
Water
Detectors
Radiation
detectors
radiation distribution
dosage
Electrons
Radiometry
Diamond
water
Photons
Uncertainty
Reading
Radiation detectors

ASJC Scopus subject areas

  • Biomedical Engineering
  • Physics and Astronomy (miscellaneous)
  • Radiology Nuclear Medicine and imaging
  • Radiological and Ultrasound Technology

Cite this

Monte Carlo dosimetry study of a 6 MV stereotactic radiosurgery unit. / Verhaegen, F.; Das, I. J.; Palmans, H.

In: Physics in Medicine and Biology, Vol. 43, No. 10, 10.1998, p. 2755-2768.

Research output: Contribution to journalArticle

Verhaegen, F. ; Das, I. J. ; Palmans, H. / Monte Carlo dosimetry study of a 6 MV stereotactic radiosurgery unit. In: Physics in Medicine and Biology. 1998 ; Vol. 43, No. 10. pp. 2755-2768.
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