Tissue identification with micro-magnetic resonance imaging in a caprine spinal fusion model

M.P. Uffen, M.R. Krijnen, R.J. Hoogendoorn, G.J. Strijkers, V. Everts, P.I. Wuisman, T.H. Smit

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    Nonunion is a major complication of spinal
    interbody fusion. Currently X-ray and computed tomography
    (CT) are used for evaluating the spinal fusion process.
    However, both imaging modalities have limitations in
    judgment of the early stages of this fusion process, as they
    only visualize mineralized bone. Magnetic resonance
    imaging (MRI) could be of great value as it is able to discriminate
    between different types of tissue. A feasibility
    study was performed in nine animals from a goat spinal
    fusion study, to evaluate the detection capacity of different
    tissues with micro-MRI. In this study bioresorbable polylactic
    acid cages were used. Six- and 12-months follow-up
    specimens were scanned in a 6.3 T micro-MRI scanner.
    After scanning, the specimens were processed for histology.
    Different types of tissue as well as the degradable cage
    material were identified in the fusion zone and designated as
    regions of interest (ROIs). Subsequently, the location of
    these ROIs was determined on the corresponding micro-
    MRI image, and average signal intensities of every individual
    ROI were measured. An excellent match was seen
    between the histological sections and micro-MRI images.
    The micro-MRI images showed quantifiable differences in
    signal intensity between bone with adipose marrow, bone
    with hematopoietic marrow, fibrocartilage, fibrous tissue,
    and degradable implant material. In time the signal intensity
    of bone with adipose marrow, bone with hematopoietic red
    marrow, and of fibrous tissue remained relatively constant.
    On the other hand, the signal intensity of the degradable
    implant material and the fibrocartilage changed significantly
    in time, indicating change of structure and
    composition. In conclusion, in our model using bioresorbable
    cages the MRI provides us with detailed information
    about the early fusion process and may therefore, allow
    early diagnosis of non-union.
    Original languageUndefined/Unknown
    Pages (from-to)1006-1011
    JournalEuropean Spine Journal
    Publication statusPublished - 2008

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