Magnetic resonance imaging of liver and spleen with superparamagnetic contrast agents

Claim 1

The method of imaging a tumor in the liver or spleen of a human subject, comprising: (a) parenterally administering to the human subject prior to magnetic resonance imaging (MRI) examination an aqueous suspension composed essentially of microspheres having diameters of less than 1.5 microns, said microspheres being composed of a biodegradable matrix material with a particulate superparamagnetic contrast agent therein, said superparamagnetic contrast agent consisting essentially of ferromagnetic particles of not over 300 angstroms diameter, the quantity of said microspheres administered being effective to appreciably reduce the T 2 relaxation time of the subject's liver or spleen; (b) delaying the examination until the microspheres have been segregated by the reticuloendothelial system and are concentrated in the liver and spleen; and then (c) carrying out an MRI examination of the liver or spleen by T 2 imaging or mixed T 1 and T 2 imaging to obtain an image in which the normal liver or spleen tissues appear dark and the tumor appears light with distinct margins therebetween.

Claim 2

The method of imaging a tumor in the liver or spleen of a human subject, comprising: (a) parenterally administering to the human subject prior to magnetic resonance imaging (MRI) examination an aqueous suspension composed essentially of microspheres having diameters of less than 1.5 microns, said microspheres being composed of a biodegradable matrix material with a particulate superparamagnetic contrast agent therein, said superparamagnetic contrast agent consisting essentially of ferromagnetic particles of not over 300 angstroms diameter, the quantity of said microspheres administered being effective to appreciably reduce the T 2 relaxation time of the subject's liver or spleen; (b) delaying the examination until the microspheres have been segregated by the reticuloendothelial system and are concentrated in the liver and spleen; and then (c) carrying out an MRI examination of the liver or spleen by T 2 imaging or mixed T 1 and T 2 imaging to obtain an image in which the normal liver or spleen tissues appear dark and the tumor appears light with distinct margins therebetween.

Claim 4

The method of claims 1 or 2 in which said biodegradable matrix material is human serum albumin.

Claim 5

The method of imaging a tumor in the liver or spleen or a human subject, comprising: (a) intravenously administering to the human subject prior to magnetic resonance imaging (MRI) examination an aqueous suspension composed essentially of microspheres having diameters of less than 1.5 microns, said microspheres being composed of a biodegradable matrix material with a particulate ferromagnetic contrast agent embedded therein, said contrast agent having a particle size of less than 300 Angstroms and exhibiting superparamagnetic properties, the quantity of said microspheres administered being effective to appreciably reduce the T 2 relaxation times of the subject's liver and/or spleen; (b) delaying the examination until the microspheres have been segregated by the reticuloendothelial system and are concentrated in the liver and spleen; and then (c) carrying out an MRI examination of the liver spleen by T 2 imaging or mixed T 1 and T 2 imaging to obtain an image in which the normal liver or spleen tissues appear dark and the tumor appears light with distinct margins therebetween.

Claim 6

The method of imaging a tumor in the liver or spleen or a human subject, comprising: (a) intravenously administering to the human subject prior to magnetic resonance imaging (MRI) examination an aqueous suspension composed essentially of microspheres having diameters of less than 1.5 microns, said microspheres being composed of a biodegradable matrix material with a particulate ferromagnetic contrast agent embedded therein, said contrast agent having a particle size of less than 300 Angstroms and exhibiting superparamagnetic properties, the quantity of said microspheres administered being effective to appreciably reduce the T 2 relaxation times of the subject's liver and/or spleen; (b) delaying the examination until the microspheres have been segregated by the reticuloendothelial system and are concentrated in the liver and spleen; and then (c) carrying out an MRI examination of the liver spleen by T 2 imaging or mixed T 1 and T 2 imaging to obtain an image in which the normal liver or spleen tissues appear dark and the tumor appears light with distinct margins therebetween.

Claim 8

The method of claims 4 or 5 in which said matrix material is human serum albumin.