Tumor-enhancement effect of a Mn3+ metalloporphyrin derivative (ATN-4T) in magnetic resonance imaging

Magnetic resonance imaging is routinely used for tumor recognition in cancer diagnosis. The tumor image-enhancing characteristics of ATN-4T (THF–Mn–Asp), a Mn3+ metalloporphyrin derivative, were evaluated in rabbits. ATN-4T (10 mM) was diluted in gelatin to final concentrations ranging from 100 to 1 μM. Increasing concentrations of ATN-4T resulted in higher signal intensities. VX2 (squamous cell carcinoma) tumor-bearing rabbits were injected with 50 μmol/kg ATN-4T intravenously and T1-weighted images were recorded continuously. Tumor images were compared with images of surrounding muscle tissue. T1-weighted images from ATN-4T-treated rabbits showed a marked enhancement of tumor contrast from 30 to 240 min postinjection. Microscopic examination revealed that carcinoma cells were scattered throughout the high contrast area of the tumor and were not seen in the surrounding muscles. ATN-4T appears useful for enhancing the intensity of tumors imaged by magnetic resonance.