Small fields

Nonequilibrium radiation dosimetry

Indra J. Das, George X. Ding, Anders Ahnesjö

Research output: Contribution to journalArticle

374 Citations (Scopus)

Abstract

Advances in radiation treatment with beamlet-based intensity modulation, image-guided radiation therapy, and stereotactic radiosurgery (including specialized equipments like CyberKnife, Gamma Knife, tomotherapy, and high-resolution multileaf collimating systems) have resulted in the use of reduced treatment fields to a subcentimeter scale. Compared to the traditional radiotherapy with fields ≥4×4 cm2, this can result in significant uncertainty in the accuracy of clinical dosimetry. The dosimetry of small fields is challenging due to nonequilibrium conditions created as a consequence of the secondary electron track lengths and the source size projected through the collimating system that are comparable to the treatment field size. It is further complicated by the prolonged electron tracks in the presence of low-density inhomogeneities. Also, radiation detectors introduced into such fields usually perturb the level of disequilibrium. Hence, the dosimetric accuracy previously achieved for standard radiotherapy applications is at risk for both absolute and relative dose determination. This article summarizes the present knowledge and gives an insight into the future procedures to handle the nonequilibrium radiation dosimetry problems. It is anticipated that new miniature detectors with controlled perturbations and corrections will be available to meet the demand for accurate measurements. It is also expected that the Monte Carlo techniques will increasingly be used in assessing the accuracy, verification, and calculation of dose, and will aid perturbation calculations of detectors used in small and highly conformal radiation beams.

Original languageEnglish (US)
Pages (from-to)206-215
Number of pages10
JournalMedical Physics
Volume35
Issue number1
DOIs
StatePublished - 2008
Externally publishedYes

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Radiometry
Radiation
Radiotherapy
Image-Guided Radiotherapy
Electrons
Radiosurgery
Uncertainty
Therapeutics
Equipment and Supplies

Keywords

  • Monte Carlo
  • Nonequilibrium conditions
  • Small field dosimetry

ASJC Scopus subject areas

  • Biophysics

Cite this

Das, I. J., Ding, G. X., & Ahnesjö, A. (2008). Small fields: Nonequilibrium radiation dosimetry. Medical Physics, 35(1), 206-215. https://doi.org/10.1118/1.2815356

Small fields : Nonequilibrium radiation dosimetry. / Das, Indra J.; Ding, George X.; Ahnesjö, Anders.

In: Medical Physics, Vol. 35, No. 1, 2008, p. 206-215.

Research output: Contribution to journalArticle

Das, IJ, Ding, GX & Ahnesjö, A 2008, 'Small fields: Nonequilibrium radiation dosimetry', Medical Physics, vol. 35, no. 1, pp. 206-215. https://doi.org/10.1118/1.2815356
Das, Indra J. ; Ding, George X. ; Ahnesjö, Anders. / Small fields : Nonequilibrium radiation dosimetry. In: Medical Physics. 2008 ; Vol. 35, No. 1. pp. 206-215.
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