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The Use of CT Density Changes at Internal Tissue Interfaces to Correlate Internal Organ Motion with an External Surrogate
Physics in Medicine and Biology (2009)
  • Stewart Gaede, University of Western Ontario
  • Gregory Carnes, University of Western Ontario
  • Edward Yu, University of Western Ontario
  • Jake Van Dyk, University of Western Ontario
  • Jerry Battista, University of Western Ontario
  • Ting-Yim Lee, University of Western Ontario
The purpose of this paper is to describe a non-invasive method to monitor the motion of internal organs affected by respiration without using external markers or spirometry, to test the correlation with external markers, and to calculate any time shift between the datasets. Ten lung cancer patients were CT scanned with a GE LightSpeed Plus 4-Slice CT scanner operating in a ciné mode. We retrospectively reconstructed the raw CT data to obtain consecutive 0.5 s reconstructions at 0.1 s intervals to increase image sampling. We defined regions of interest containing tissue interfaces, including tumour/lung interfaces that move due to breathing on multiple axial slices and measured the mean CT number versus respiratory phase. Tumour motion was directly correlated with external marker motion, acquired simultaneously, using the sample coefficient of determination, r(2). Only three of the ten patients showed correlation higher than r(2) = 0.80 between tumour motion and external marker position. However, after taking into account time shifts (ranging between 0 s and 0.4 s) between the two data sets, all ten patients showed correlation better than r(2) = 0.8. This non-invasive method for monitoring the motion of internal organs is an effective tool that can assess the use of external markers for 4D-CT imaging and respiratory-gated radiotherapy on a patient-specific basis.
  • Biophysical Phenomena,
  • Humans,
  • Imaging,
  • Three-Dimensional,
  • Lung Neoplasms,
  • Movement,
  • Organ Specificity,
  • Radiotherapy Planning,
  • Computer-Assisted,
  • Radiotherapy,
  • Computer-Assisted,
  • Respiration,
  • Respiratory Mechanics,
  • Tomography Scanners,
  • X-Ray Computed,
  • Tomography,
  • X-Ray Computed
Publication Date
January 21, 2009
Publisher Statement
Published in: Phys. Med. Biol. 54 259-273. doi: 10.1088/0031-9155/54/2/006
Citation Information
Stewart Gaede, Gregory Carnes, Edward Yu, Jake Van Dyk, et al.. "The Use of CT Density Changes at Internal Tissue Interfaces to Correlate Internal Organ Motion with an External Surrogate" Physics in Medicine and Biology Vol. 54 Iss. 2 (2009)
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