title: Automated generation of a four-dimensional model of the liver using warping and mutual information.
abstract: The use of mutual information (MI) based alignment to map changes in liver shape and position from exhale to inhale was investigated. Inhale and exhale CT scans were obtained with intravenous contrast for six patients. MI based alignment using thin-plate spine (TPS) warping was performed between each inhale and exhale image set. An expert radiation oncologist identified corresponding vessel bifurcations on the exhale and inhale CT image and the transformation for identified points was determined. This transformation was then used to determine the accuracy of the MI based alignment. The reproducibility of the vessel bifurcation identification was measured through repeat blinded vessel bifurcation identification. Reproducibility [standard deviation (SD)] in the L/R, A/P, and I/S directions was 0.11, 0.09, and 0.14 cm, respectively. The average absolute difference between the transformation obtained using MI based alignment and the vessel bifurcation in the L/R, A/P, and I/S directions was 0.13 cm (SD=0.10 cm), 0.15 cm (SD=0.12 cm), and 0.15 cm (SD-0.14 cm), respectively. These values are comparable to the reproducibility of bifurcation identification, indicating that MI based alignment using TPS warping is accurate to within measurement error and is a reliable tool to aid in describing deformation that the liver undergoes from the exhale to inhale state.
authors.affiliation: Department of Radiation Oncology, University of Michigan Health Systems, Ann Arbor, Michigan 48109, USA. kkbrock@umich.edu
authors.forename: K M
authors.initials: KM
authors.lastname: Brock
authors.forename: J M
authors.initials: JM
authors.lastname: Balter
authors.forename: L A
authors.initials: LA
authors.lastname: Dawson
authors.forename: M L
authors.initials: ML
authors.lastname: Kessler
authors.forename: C R
authors.initials: CR
authors.lastname: Meyer
mesh_terms: D000465:Algorithms; D016477:Artifacts; D006499:Hepatic Artery / Q000000981:diagnostic imaging; D006503:Hepatic Veins / Q000000981:diagnostic imaging / Q000502:physiology; D006801:Humans; D008099:Liver / Q000000981:diagnostic imaging* / Q000502:physiology*; D009068:Movement / Q000502:physiology*; D010363:Pattern Recognition, Automated; D011856:Radiographic Image Enhancement / Q000379:methods*; D011857:Radiographic Image Interpretation, Computer-Assisted / Q000379:methods*; D015203:Reproducibility of Results; D012119:Respiration; D012680:Sensitivity and Specificity; D013382:Subtraction Technique