Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy

Sarah Joy, George Starkschall, Stephen Kry, Mohammed Salehpour, R. Allen White, Steven H. Lin, Peter Balter

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

The purpose of this work was to determine the dosimetric benefit to normal tissues by tracking the multi-leaf collimator (MLC) apertures with the photon jaws in step-and-shoot intensity-modulated radiation therapy (IMRT) on the Varian 2100 platform. Radiation treatment plans for ten thoracic, three pediatric, and three head and neck cancer patients were converted to plans with the jaws tracking each segment's MLC apertures, and compared to the original plans in a commercial radiation treatment planning system (TPS). The change in normal tissue dose was evaluated in the new plan by using the parameters V5, V10, and V20 (volumes receiving 5, 10 and 20 Gy, respectively) in the cumulative dose-volume histogram for the following structures: total lung minus gross target volume, heart, esophagus, spinal cord, liver, parotids, and brainstem. To validate the accuracy of our beam model, MLC transmission was measured and compared to that predicted by the TPS. The greatest changes between the original and new plans occurred at lower dose levels. In all patients, the reduction in V20 was never more than 6.3% and was typically less than 1%; the maximum reduction in V5 was 16.7% and was typically less than 3%. The variation in normal tissue dose reduction was not predictable, and we found no clear parameters that indicated which patients would benefit most from jaw tracking. Our TPS model of MLC transmission agreed with measurements with absolute transmission differences of less than 0.1% and, thus, uncertainties in the model did not contribute significantly to the uncertainty in the dose determination. We conclude that the amount of dose reduction achieved by collimating the jaws around each MLC aperture in step-and-shoot IMRT is probably not clinically significant.

Original languageEnglish (US)
Pages (from-to)136-145
Number of pages10
JournalJournal of Applied Clinical Medical Physics
Volume13
Issue number2
StatePublished - 2012
Externally publishedYes

Fingerprint

Radiotherapy
Jaw
collimators
radiation therapy
leaves
dosage
Tissue
Planning
Uncertainty
planning
apertures
Radiation
Cardiac Volume
Pediatrics
Therapeutics
Head and Neck Neoplasms
Photons
Liver
Esophagus
Brain Stem

Keywords

  • IMRT
  • Jaw optimization
  • Normal tissue dose reduction
  • Treatment planning

ASJC Scopus subject areas

  • Radiology Nuclear Medicine and imaging
  • Radiation
  • Instrumentation

Cite this

Joy, S., Starkschall, G., Kry, S., Salehpour, M., White, R. A., Lin, S. H., & Balter, P. (2012). Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy. Journal of Applied Clinical Medical Physics, 13(2), 136-145.

Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy. / Joy, Sarah; Starkschall, George; Kry, Stephen; Salehpour, Mohammed; White, R. Allen; Lin, Steven H.; Balter, Peter.

In: Journal of Applied Clinical Medical Physics, Vol. 13, No. 2, 2012, p. 136-145.

Research output: Contribution to journalArticle

Joy, S, Starkschall, G, Kry, S, Salehpour, M, White, RA, Lin, SH & Balter, P 2012, 'Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy', Journal of Applied Clinical Medical Physics, vol. 13, no. 2, pp. 136-145.
Joy S, Starkschall G, Kry S, Salehpour M, White RA, Lin SH et al. Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy. Journal of Applied Clinical Medical Physics. 2012;13(2):136-145.
Joy, Sarah ; Starkschall, George ; Kry, Stephen ; Salehpour, Mohammed ; White, R. Allen ; Lin, Steven H. ; Balter, Peter. / Dosimetric effects of jaw tracking in step-and-shoot intensity-modulated radiation therapy. In: Journal of Applied Clinical Medical Physics. 2012 ; Vol. 13, No. 2. pp. 136-145.
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