Comparison of Gd [DTPA-bis (2-aminoethoxy) ethane] polymeric contrast agent with gadodiamide injection for interstitial MR lymphography: Experimental study with rabbits

Purpose: To compare the differences between macromolecular and small molecular contrast agents in interstitial magnetic resonance (MR) lymphography. Materials and Methods: In two groups of rabbits (N = 12 each), 0.5-mL volumes of 0.5 M and 0.1 M gadodiamide, respectively, were injected subcutaneously into the dorsal feet of both hind legs. After a 24-hour interval, 0.5 mL of Gd [DTPA-bis (2-aminoethoxy) ethane] polymeric contrast agent (Gd-poly-DTPA-EOEA) injection (0.1 M) was injected into the same sites in each rabbit. T1-weighted three-dimensional gradient-echo and maximum intensity projection (MIP) images were obtained before and after the administration of each agent. The nodal maximum short-axis diameter (MSAD) and signal-to-noise ratio (SNR) at each time point were measured. Postmortem measurements of nodal MSADs were also performed. The nodal MSAD measurements obtained by MR lymphography were compared with the postmortem measurements. As an additional control experiment, six rabbits received a subcutaneous injection of 0.5 mL of 0.1 M gadodiamide at the same sites as those described above. This procedure was repeated after a 24-hour interval to determine whether the first injected gadodiamide had any effect on the performance of the subsequently injected agent, by comparing the differences in nodal MSADs obtained by MR lymphography after each injection. Results: Gd-poly-DTPA-EOEA showed a significantly longer enhancement plateau compared to gadodiamide. In comparison with postmortem measurements, nodal measurements by MR lymphography with Gd-poly-DTPAEOEA at the peak-enhancement phase revealed no significantly different MSADs (P > 0.05), whereas nodal measurements by MR lymphography with gadodiamide showed significantly smaller MSADs (P < 0.05). A comparison of the nodal MSADs measured in two gadodiamide-enhanced MR examinations after the 24-hour interval showed no significant difference (P > 0.05). Conclusion: Interstitial MR lymphography with polymeric Gd-poly-DTPA-EOEA enhancer enables more sufficient and reliable visualization of lymph nodes compared to small molecular gadodiamide.