[Experimental studies of ferrite as a MRI contrast agent].
Using a 0.2 T permanent MR imaging system, the gradual changes of signal intensity after intravenous injection of Ferrite suspension were studied in liver of normal rabbits and those with intrahepatic VX2 tumor. After injection of Ferrite suspension, decreased signal intensities of liver were observed on both T1 and T2 weighted images. The decrease on T2 weighted images was more remarkable than that on the T1 weighted image. The image with 8 mg/kg (50 mumol/kg) dose of Ferrite suspension showed significant changes of signal intensity, while, the image with 24 mg/kg (150 mumol/kg) dose was hardly evaluated because of inducing intense artifacts. The decrease of signal intensity in liver was observed immediately after the injection and was lowest after 1 hour. After 48 hours, the signal intensity began to increase. However, a slight loss of signal intensity was visualized even after 4 weeks. A clear MRI of the intrahepatic tumor following injection of Ferrite suspension was acquired especially on T2 weighted image in comparison with MRI after Gd-DTPA administration. In addition, MRI using Ferrite suspension could detect the small intrahepatic tumors which had been unable to be visualized by plain CT or enhanced CT. It is of benefit, furthermore, that Ferrite suspension could be an useful tracer for observing the intrahepatic tumor growth by a first single injection. Histologically, Ferrite particles were accumulated in reticuloendothelial system of liver whereas no accumulated in intrahepatic tumor was verified. The particles produced changes in local magnetic field resulting that signal intensity of liver showed decrease on the image. Subsequently, relatively negative contrast enhancement of liver was displayed. As a result of the present investigation, the MR imaging following injection of Ferrite suspension was found to be useful for detection of intrahepatic tumors, particularly of metastatic tumors which were isointense or hypovascular to the surrounding tissue of liver. No evidence of acute toxicity by Ferrite administration has been noticed.
Aoki
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Department of Rediology, Nippon Medical School First Hospital, Tokyo, Japan.
D000818:Animals; D003287:Contrast Media; D005290:Ferric Compounds; D019786:Gadolinium DTPA; D008114:Liver Neoplasms, Experimental / Q000175:diagnosis; D008279:Magnetic Resonance Imaging; D008297:Male; D009942:Organometallic Compounds; D004369:Pentetic Acid; D011817:Rabbits
D003287:Contrast Media; D005290:Ferric Compounds; D009942:Organometallic Compounds; C001215:ferrite; D004369:Pentetic Acid; D019786:Gadolinium DTPA