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Gadolinium-enhanced MR Images of the Growing Piglet Skeleton: Ionic versus Nonionic Contrast Agent¹

¹ From the Department of Radiology, Massachusetts General Hospital and Harvard Medical School, Boston, Mass (N.M.M., E.A.O., D.J.); Athinoula A. Martinos Center for Biomedical Imaging, Department of Radiology, Massachusetts General Hospital and the Harvard-Massachusetts Institute of Technology Division of Health Sciences and Technology, 149 13th St, Rm 2301, Boston, MA 02129 (N.M.M., M.F.); Division of MRI, Department of Radiology, Tongji Hospital, Tongji Medical University, Huazhong University of Science and Technology, Hubei, Wuhan, China (X.L.); Departments of Radiology (S.A.C.) and Orthopaedic Surgery (D.Z., F.S.), Children's Hospital Boston and Harvard Medical School, Boston, Mass; and Department of Pathology, Children's Hospital Boston, Boston, Mass (F.S.). Received March 1, 2005; revision requested April 14; revision received June 25; final version accepted July 8. Supported by National Institutes of Health grant R01 AR042396-09. Address correspondence to N.M.M. (e-mail: nmenezes{at}nmr.mgh.harvard.edu).

Purpose: To determine whether there are differences in the distribution of ionic and nonionic gadolinium-based contrast agents by evaluating contrast enhancement of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis in the knees of normal piglets.

Materials and Methods: Following approval from the Subcommittee on Research Animal Care, knees of 12 3-week-old piglets were imaged at 3-T magnetic resonance (MR) imaging after intravenous injection of gadoteridol (nonionic contrast agent; n = 6) or gadopentetate dimeglumine (ionic contrast agent; n = 6). Early enhancement evaluation with gradient-echo MR imaging was quantified and compared (Student t test) by means of enhancement ratios. Distribution of contrast material was assessed and compared (Student t test) by means of T1 measurements obtained before and at three 15-minute intervals after contrast agent administration. The relative visibility of the physis, epiphyseal cartilage, secondary ossification center, and metaphysis was qualitatively assessed by two observers and compared (Wilcoxon signed rank test). Differences in matrix content and cellularity that might explain the imaging findings were studied at histologic evaluation.

Results: Enhancement ratios were significantly higher for gadoteridol than for gadopentetate dimeglumine in the physis, epiphyseal cartilage, and secondary ossification center (P < .05). After contrast agent administration, T1 values decreased sharply for both agents—but more so for gadoteridol. Additionally, there was less variability in T1 values across structures with this contrast agent. Gadoteridol resulted in greater visibility of the physis, while gadopentetate dimeglumine resulted in greater contrast between the physis and metaphysis (P < .05).

Conclusion: The results suggest different roles for the two gadolinium-based contrast agents: The nonionic contrast medium is better suited for evaluating perfusion and anatomic definition in the immature skeleton, while the ionic contrast medium is better for evaluating cartilage fixed-charge density.

© RSNA, 2006