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Morrisett

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Morrisett

  1. 1. Carotid Atherosclerotic Lesion Models for Quality Control of Clinical Trials with MRI Endpoints William Insull, M.D., Gareth Adams, B.S. Cassius Bordelon, Ph.D. and Joel Morrisett, Ph.D. Baylor College of Medicine Houston,Texas
  2. 2. The Model Attributes should closely resemble those of human carotid arteries in terms of: a) gross and microscopic structure and dimensions b) spatial distribution of principal components c) chemical composition of principal components d) presence of normal and atherosclerotic tissues e) presence of all stages of atherosclerotic lesions f) identifiable zones of transition from normal to atherosclerotic regions for indexing lesion initiation, development, and growth
  3. 3. Model Attributes (continued) g) identifiable major lesion types for indexing lesion changes and the effects of treatment (retardation, stabilization, regression) h) defined sites for replicate measures, whose locations are referenced to the carotid bifurcation or an external marker i) gross dimensions, histology, and chemical composition at reference sites as defined by accepted independent measurements (e.g. X-ray, raman, infrared spectroscopies) j) multiple reference sites indexed for easy use k) stability for extended time periods (e.g. years) in chemical composition, and gross and microscopic morphology
  4. 4. The Model Holder should: a) have clear identification permanently attached b) allow easy access to indexed sites c) provide mounting that makes the model resistant to normal wear d) be compatible with conventional and state-of-the-art MRI instrumentation e) be amenable to convenient handling and shipping f) have attached instructions for handling by the user
  5. 5. Model Documentation should provide: a) accurate description of the gross and histological composition, with location of defined, indexed referenced sites for rapid orientation in scanning and measurement b) an atlas of acceptable images c) specifications for MR image acquisition at indexed reference sites d) defined quality control parameters with the accepted “in control” range e) periodic verification of stability of MRI characteristics performed by the reference laboratory f) life history of the model
  6. 6. CCA BIF ICA ECA Cadaveric human carotid artery used for Reference Standard Tissue was perfusion fixed at mean arterial pressure before excision. Most of the periadventitial tissue has been removed. The common carotid artery (CCA), bifurcation (BIF), external carotid artery (ECA), and internal carotid artery (ICA) are clearly seen.
  7. 7. Cadaveric Carotid Specimens ( models of the native carotid arteries) -contain intima, media, adventitia, and some perivascular soft tissue -enable study of range of lesion types -allow comparison of left/right carotids -give reproducible images over >1 year -provide stable reference for: -intra-laboratory standardization -inter-laboratory standardization for multicenter clinical trials
  8. 8. Holder for imaging cadaveric carotid tissues. The tubes (3.0cm diameter) are secured in four holes drilled in a plastic insert (8.0cm diameter) fabricated from two 100ml plastic beakers fastened top-to-top by superglue. The insert is placed in a larger plastic bottle (12.0cm diameter, 22.0cm tall) fitted with a water inlet at the bottom and outlet at the top for temperature control. A pair of phased array coils (6cm Ultra Image/Pathway) is fastened around the outside of the larger outer bottle with velcro strips. Tissues are imaged in a GE Horizon 1.5T clinical MRI system with 10cm FOV, 2 NEX, 3mm slice thickness. TR/TE for the different contrast sequences: 3000/34 (PDW), 650/14 (T1W), and 3000/108 (T2W).
  9. 9. 1.5T MR images of left and right human cadaveric carotid arteries above, at, and below their bifurcation. The plaque within each tissue slice (red area) has been identified by a semi-automatic algorithm. 3D reconstructions from multiple slices are used to calculate the aggregate volumes.
  10. 10. PDW T1W T2W MR images of human cadaveric carotids acquired on a GE Horizon LX 1.5T system fitted with UltraImage/Pathway phased array coils (also used for human carotid studies in vivo). The slices (3mm) begin at the bifurcation (left) and descend to the common carotid artery (right). Proton density-, T1-, and T2- weighted images show plaque heterogeneity

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