CHARACTERIZATION OF REACTIVE VERSUS TUMOR-BEARING LYMPH-NODES WITH INTERSTITIAL MAGNETIC-RESONANCE LYMPHOGRAPHY IN AN ANIMAL-MODEL

RATIONALE AND OBJECTIVES. To determine if magnetic resonance lymphogra phy performed with subcutaneously administered AMI-227, a nanoparticul ate iron oxide contrast agent, can distinguish reactive from tumor-bea ring lymph nodes. MATERIALS AND METHODS. Mature male Copenhagen rats w ere inoculated with cell suspensions of R3327-MAT-LyLu rat prostate ca rcinoma (n = 21) or Freund's complete adjuvant (n = 15) in the left fo otpad to generate ipsilateral popliteal lymph node metastases or lymph adenitis. At 12 to 14 days after inoculation, T1- and T2-weighted magn etic resonance images of bilateral popliteal areas were obtained befor e and 24 hours after subcutaneous administration of AMI-227, Contrast- to-noise ratios were calculated in precontrast and postcontrast images . Bilateral popliteal nodes were excised for pathologic assessment. RE SULTS. AMI-227 resulted in decreased contrast-to-noise ratios in react ive (T1 - W = -7.01 +/- 1.13, T2 - W = -31.64 +/- 5.35) and normal (T1 - W = -13.56 +/- 1.97, T2 - W = -21.62 +/- 2.51) nodes, Contrast-to-n oise ratios were unchanged (T1 - W = -0.22 +/- 1.71, T2 - W = -2.20 +/ - 4.19) in tumor-containing nodes. These differences in contrast-to-no ise ratio changes between tumor-bearing versus nontumor-hearing nodes were statistically significant (P < 0.05). Histologic analysis showed similar distribution of AMI-227 within normal and reactive nodes, but not in tumor-bearing nodes. CONCLUSIONS. Differences in AMI-227-uptake between tumor- and nontumor-bearing nodes detected with magnetic reso nance imaging are helpful for distinguishing the two entities.