Metalloporphyrin Contrast Enhancement of Tumors in Magnetic Resonance Imaging A Study of Human Carcinoma, Lymphoma, and Fibrosarcoma in Mice

The diagnostic use of Mn(III)TPPS4, a paramagnetic metalloporphyrin, for MR contrast enhancement was examined in human--mouse xenograph models of carcinoma, lymphoma, and sarcoma. Spin-echo images of 15 mice, five mice for each implanted tumor type, were obtained before and at 20 minutes, and 2, 4, and 24 hours following administration of 0.09 mmol/kg of Mn(III)TPPS4. All tumors had a uniform moderate signal intensity on precontrast images. After administration of Mn(III)TPPS4, all tumors demonstrated significant enhancement of signal intensity that persisted to 24 hours. T1 relaxation times were maximally depressed at 2-4 hours and remained low to 24 hours for all three tumors. Kidney signal intensity reached a maximum at 20 minutes and remained significantly above background for 24 hours. The high relaxivity and apparent avidity of Mn(III)TPPS4 for divergent tumor histologies support the potential use of this agent for improved diagnostic specificity of MR imaging for neoplastic masses.