Contrast-enhanced MR imaging of postoperative scars and VX2 carcinoma in rabbits: comparison of macromolecular contrast agent and gadopentetate dimeglumine.

PURPOSE

To compare the magnetic resonance (MR) imaging enhancement patterns of a blood pool contrast agent, SH L 643A, with those of gadopentetate dimeglumine in postoperative scars and VX2 carcinomas in rabbits and to compare these enhancement patterns with microvessel density in pathologic specimens.

MATERIALS AND METHODS

Eighteen rabbits with experimentally induced postoperative scars (n = 12) or VX2 carcinoma (n = 6) in the thighs underwent sequential MR imaging first with gadopentetate dimeglumine and then, 24 hours later, with SH L 643A. The enhancement ratios (ie, the ratios of postcontrast to precontrast signal intensity) and the microvessel densities of postoperative scars and VX2 carcinomas were assessed. Differences were tested for by using the Mann-Whitney U and Wilcoxon signed rank tests.

RESULTS

In postoperative scars, enhancement ratios were consistently lower with injection of SH L 643A than with injection of gadopentetate dimeglumine for up to 30 minutes (P <.05). In postoperative scars, mean peak enhancement ratios were 1.29 +/- 0.15 (SD) with injection of SH L 643A and 1.61 +/- 0.31 with injection of gadopentetate dimeglumine (P <.01). In VX2 carcinomas, the enhancement ratios were not significantly different with injection of SH L 643A than with injection of gadopentetate dimeglumine at all time points. The mean difference between the enhancement ratios of the VX2 carcinomas and postoperative scars was 0.64 +/- 0.10 (range, 0.50-0.77) with SH L 643A and 0.36 +/- 0.16 (range, 0.17-0.66) with gadopentetate dimeglumine (P <.01). The mean microvessel density (in terms of vessels per field of view) was 10.7 +/- 5.5 for postoperative scars and 30.0 +/- 7.7 for VX2 carcinoma (P <.001).

CONCLUSION

The difference between the enhancement ratios of postoperative scars and VX2 carcinomas with SH L 643A was greater than that with gadopentetate dimeglumine. Enhancement ratios at SH L 643A-enhanced MR imaging corresponded well with microvessel density in postoperative scars and VX2 carcinomas.