Interfractional variations of shape and impact on dose of organs at risk in head and neck cancer patients during helical tomotherapy

M. N. Duma, S. Kampfer, V. Jacob, J. J. Wilkens, T. Schuster, M. Molls, H. Geinitz

Research output: Chapter in Book/Report/Conference proceedingConference contributionpeer-review

Abstract

PURPOSE: IGRT by daily MVCTs is becoming wider used. We analyzed the interfractional variations of shape and the impact on dose of the organs at risk (OARs) - i.e. parotid glands (PGs) and spinal cord (SC) - in head and neckcancer patients. PATIENTS AND METHODS: Ten head and neck patients were investigated retrospectively. All patients were treated up to 50 Gy with helical tomotherapy (HT) (2 Gy/day). Daily pretreatment MVCTs were performed. The OARs were all delineated by the same physician on the corresponding MVCTs for predetermined fractions. The actual delivered doses to the PGs and the SC were assessed by using the TomoTherapy PlannedAdaptive® software. The initial dose-volume histograms (DVHs) and the recalculated DVHs of the OARs of the corresponding fraction were used for the quantitative comparison of the cumulative maximum doses of the SC (CMaDSC) and the cumulative median doses of the PGs (CMeDPG). The interfractional changes of volumes of the PGs that received less than 1 Gy and over 1.6 Gy per fraction and the volumes of the SC that received more than the expected maximum dose were also assessed. RESULTS: Overall, the mean decrease of the PG volume was estimated to be 0.13 cc per day. There was a significantly higher CMeDPG and CMaDSC than initially predicted (mean increase for 6 fractions in Gy: 1.13 and 0.49, respectively). TheVol<1Gy decreased and the Vol>1.6Gy increased significantly with increasing fraction number (mean difference to the planning CT: 1.3 cc and 1.1 cc, respectively). CONCLUSIONS: The delivered dose to the PG and SC is higher than predicted by the PCT DVH data even if daily IGRT is performed.

Original languageEnglish
Title of host publicationWorld Congress on Medical Physics and Biomedical Engineering
Subtitle of host publicationRadiation Oncology
PublisherSpringer Verlag
Pages591-594
Number of pages4
Edition1
ISBN (Print)9783642034725
DOIs
StatePublished - 2009
EventWorld Congress on Medical Physics and Biomedical Engineering: Radiation Oncology - Munich, Germany
Duration: 7 Sep 200912 Sep 2009

Publication series

NameIFMBE Proceedings
Number1
Volume25
ISSN (Print)1680-0737

Conference

ConferenceWorld Congress on Medical Physics and Biomedical Engineering: Radiation Oncology
Country/TerritoryGermany
CityMunich
Period7/09/0912/09/09

Keywords

  • Helical tomotherapy
  • IGRT
  • MVCT
  • Organs at risk
  • Parotid glands

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