MR Lymphography with a Lymphotropic T1‐Type MR Contrast Agent: Gd‐DTPA‐PGM

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Abstract
A model system of a paramagnetic lymphotropic MR contrast agent (Gd‐DTPA labeled polyglucose associated macrocomplex, PGM) for T1‐weighted MR imaging of lymph nodes in rats and rabbits was evaluated. Pharmacokinetic (tissue accumulation) and MR imaging data (optimal dose and timing parameters) were obtained in normal rats (n = 88) after subcutaneous (SC) injection of paramagnetic, radiolabeled [111In]Gd‐DTPA‐PGM. A rabbit model of lymph node metastases (n = 8) was ultimately used to demonstrate the potential of MR imaging with Gd‐DTPA‐PGM for nodal tumor detection. Maximum concentrations of Gd‐DTPA‐PGM were found in popliteal and paraaortic lymph nodes within 24 h after SC administration, and highest lymph node SNR values were obtained by MR imaging at this time point. The optimum imaging dose was 6–12 μmol Gd/kg. Tumor‐lymph node contrast increased from 0.0 ± 1.2 precontrast to 19.2 ± 6.5 (spoiled gradient echo sequence, TR 50/TE 7/flip angle 60°) postcontrast and conspicuity of nodal metastases was improved. Gd‐DTPA‐PGM accumulates in lymph nodes after SC administration and significantly enhances lymph node signal intensity of normal animals but not metastatic lymph nodes.