Dosimetric Effect of Prostate Motion During Helical Tomotherapy

Katja M. Langen, Weiguo Lu, Twyla R. Willoughby, Bhavin Chauhan, Sanford L. Meeks, Patrick A. Kupelian, Gustavo Olivera

Research output: Contribution to journalArticlepeer-review

36 Scopus citations


Purpose: To assess the dosimetric consequence of intrafraction prostate motion on helical tomotherapy plans. Methods and Materials: An electromagnetic tracking device was used to measure real-time prostate motion for 515 fractions (16 patients). Motion tracks were used to retrospectively recalculate dose distributions using a four-dimensional calculation engine. The minimum dose (Dmin), maximum dose (Dmax), and dose to 95% of the volume (D95%) were calculated for target volumes and compared with respective values from the treatment plan. The dosimetric effect was evaluated for each fraction. For each patient, the running cumulative effect was assessed throughout the course of treatment. Calculations were repeated assuming a time delay between initial patient setup and start of treatment. Results: Averaged over all fractions, the mean change in target D95% was <1% (SD, 3-4%). Reductions in target D95% of up to 20% were seen in individual fractions. Changes in prostate D95% were similar in frequency and magnitude to D95% changes in the planning target volume. The cumulative effect on target D95% was approximately 1% (SD, 1%). The average cumulative effect after five fractions was 1% (SD, 1.5%). Conclusions: In general, the dosimetric effect of observed prostate motion on target D95%was small. Infrequently severe D95% degradations were observed for individual fractions, but their effect on the cumulative dose distribution was quickly reduced with minimal fractionation.

Original languageEnglish (US)
Pages (from-to)1134-1142
Number of pages9
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number4
StatePublished - Jul 15 2009


  • Dosimetry
  • Prostate cancer
  • Radiotherapy
  • Real-time motion

ASJC Scopus subject areas

  • Radiation
  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Cancer Research


Dive into the research topics of 'Dosimetric Effect of Prostate Motion During Helical Tomotherapy'. Together they form a unique fingerprint.

Cite this