Estimation of Error in Maximal Intensity Projection-Based Internal Target Volume of Lung Tumors: A Simulation and Comparison Study Using Dynamic Magnetic Resonance Imaging

Jing Cai, Paul W. Read, Joseph M. Baisden, James M. Larner, Stanley H. Benedict, Ke Sheng

Research output: Journal article publicationJournal articleAcademic researchpeer-review

47 Citations (Scopus)


Purpose: To evaluate the error in four-dimensional computed tomography (4D-CT) maximal intensity projection (MIP)-based lung tumor internal target volume determination using a simulation method based on dynamic magnetic resonance imaging (dMRI). Methods and Materials: Eight healthy volunteers and six lung tumor patients underwent a 5-min MRI scan in the sagittal plane to acquire dynamic images of lung motion. A MATLAB program was written to generate re-sorted dMRI using 4D-CT acquisition methods (RedCAM) by segmenting and rebinning the MRI scans. The maximal intensity projection images were generated from RedCAM and dMRI, and the errors in the MIP-based internal target area (ITA) from RedCAM (ε), compared with those from dMRI, were determined and correlated with the subjects' respiratory variability (ν). Results: Maximal intensity projection-based ITAs from RedCAM were comparatively smaller than those from dMRI in both phantom studies (ε = -21.64% ± 8.23%) and lung tumor patient studies (ε = -20.31% ± 11.36%). The errors in MIP-based ITA from RedCAM correlated linearly (ε = -5.13ν - 6.71, r2= 0.76) with the subjects' respiratory variability. Conclusions: Because of the low temporal resolution and retrospective re-sorting, 4D-CT might not accurately depict the excursion of a moving tumor. Using a 4D-CT MIP image to define the internal target volume might therefore cause underdosing and an increased risk of subsequent treatment failure. Patient-specific respiratory variability might also be a useful predictor of the 4D-CT-induced error in MIP-based internal target volume determination.
Original languageEnglish
Pages (from-to)895-902
Number of pages8
JournalInternational Journal of Radiation Oncology Biology Physics
Issue number3
Publication statusPublished - 1 Nov 2007
Externally publishedYes


  • Four-dimensional computed tomography
  • Internal target volume
  • Lung tumor motion
  • Magnetic resonance imaging
  • Maximal intensity projection

ASJC Scopus subject areas

  • Oncology
  • Radiology Nuclear Medicine and imaging
  • Radiation

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