Contrast-enhanced high resolution magnetic resonance imaging of pigmented malignant melanoma using Mn-TPPS4 and Gd-DTPA: experimental results

The aim of this study was to evaluate the potential of the paramagnetic met alloporphyrin Mn-TPPS4 (using Gd-DTPA as the reference) for magnetic resona nce imaging (MRI) of pigmented malignant melanoma in an animal model. High resolution MRI (2.0 T, 2.0 cm surface coil, T1-weighted FLASH two-dimension al sequence) was performed on 15 mice (C57bl6) with intracutaneous implante d melanoma (B16F1) before and after intravenous administration of Gd-DTPA ( Magnevist, Schering AG, Berlin, Germany) and Mn-TPPS4 (Porphyrin Products, Logan, Utah, USA). The images were evaluated quantitatively by calculating the percentage enhancement, the slope of the signal intensity-to-time curve s, the percentage increase in the signal intensity, and the signal-to-noise and contrast-to-noise ratios. The qualitative evaluation was accomplished by visual assessment of the enhancement, the demarcation of the tumours fro m the surrounding tissue, and the homogeneity of the tumours. Contrast medi um-enhanced images showed an increase in signal intensity for all the tumou rs, with no significant difference between the contrast media. Specific acc umulation of the contrast media in the melanoma could not be proved. Demarc ation of tumours from the surrounding tissue is better after administration of contrast media; regressive changed areas were better depicted. (C) 2000 Lippincott Williams & Wilkins.