dGEMRIC was validated in vitro by comparing the GAG calculated from the MR measurements of Gd(DTPA)2- concentration to that derived from biochemical measures of GAG. The correlation was high for both bovine and human samples (e.g. Figure 1). Furthermore, variations in GAG across a sample were evident in both the dGEMRIC images and histologic sections in both bovine tissue degraded with interleukin-1 (Figure 2) and GAG lesions present in human samples obtained from patients undergoing total knee replacement surgeries (Figure 3).

Figure 1: GAG by dGEMRIC vs GAG by DMB

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Figure 2: 3D MRI of a 2 mm cultured cartilage plug with 25 micron isotropic resolution shows morphologically intact cartilage (proton density image, upperleft), with heavy T1 (dGEMRIC) variations (upper right). A 2D section of the 3D dataset matches the distribution of GAG by H&E staining.

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Figure 3:
Top : Proton density image shows morphologically intact cartilage.
Middle : T1 weighted image shows large defect in GAG concentration.
Bottom : The defect in GAG is seen on toluidine blue staining.

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For more information, see these references:

  • Bashir A, Gray ML, Burstein D. Gd-DTPA2- as a measure of cartilage degradation. Magn Reson Med 1996; 36:665-673.
  • Bashir A, Gray ML, Hartke J, Burstein D. Nondestructive Imaging of Human Cartilage Glycosaminoglycan Concentration by MRI. Magn Reson Med 1999; 41:857-865.