title: Respiratory-induced prostate motion using wavelet decomposition of the real-time electromagnetic tracking signal.
abstract: OBJECTIVE
  The objective of this work is to characterize and quantify the impact of respiratory-induced prostate motion.
  
  
  METHODS
  Real-time intrafraction motion is observed with the Calypso 4-dimensional nonradioactive electromagnetic tracking system (Calypso Medical Technologies, Inc. Seattle, Washington). We report the results from a total of 1024 fractions from 31 prostate cancer patients. Wavelet transform was used to decompose the signal to extract and isolate the respiratory-induced prostate motion from the total prostate displacement.
  
  
  RESULTS
  Our results show that the average respiratory motion larger than 0.5 mm can be observed in 68% of the fractions. Fewer than 1% of the patients showed average respiratory motion of less than 0.2 mm, whereas 99% of the patients showed average respiratory-induced motion ranging between 0.2 and 2 mm. The maximum respiratory range of motion of 3 mm or greater was seen in only 25% of the fractions. In addition, about 2% patients showed anxiety, indicated by a breathing frequency above 24 times per minute.
  
  
  CONCLUSIONS
  Prostate motion is influenced by respiration in most fractions. Real-time intrafraction data are sensitive enough to measure the impact of respiration by use of wavelet decomposition methods. Although the average respiratory amplitude observed in this study is small, this technique provides a tool that can be useful if one moves to smaller treatment margins (≤5 mm). This also opens ups the possibility of being able to develop patient specific margins, knowing that prostate motion is not unpredictable.
authors.affiliation: Tu and Yuen Center for Functional Onco-Imaging, Department of Radiological Sciences, University of California, Irvine, California, USA.
authors.forename: Yuting
authors.initials: Y
authors.lastname: Lin
authors.forename: Tian
authors.initials: T
authors.lastname: Liu
authors.forename: Xiaofeng
authors.initials: X
authors.lastname: Yang
authors.forename: Yuenan
authors.initials: Y
authors.lastname: Wang
authors.forename: Mohammad K
authors.initials: MK
authors.lastname: Khan
mesh_terms: D019583:Dose Fractionation, Radiation; D006801:Humans; D021621:Imaging, Three-Dimensional / Q000379:methods; D008297:Male; D009068:Movement; D011467:Prostate; D011471:Prostatic Neoplasms / Q000532:radiotherapy*; D050397:Radiotherapy, Intensity-Modulated / Q000379:methods; D058998:Remote Sensing Technology / Q000379:methods*; D012119:Respiration; D012680:Sensitivity and Specificity