An oxygenated Hemoglobin (Hb) solution includes from about 10 g to about 250 g of polymerized Hb per liter of solution. About 80% by weight, or greater, of the polymerized Hb of the oxygenated hemoglobin solution is oxyhemoglobin. About 18% by weight, or less, of the polymerized Hb has a molecular weight of over 500,000 Daltons. About 5% by weight, or less, of the polymerized Hb has a molecular weight equal to or less than 65,000 Daltons. A P50 of the polymerized Hb is in a range of between about 34 and about 46 mm Hg. An endotoxin content of the oxygenated Hb solution is less than about 0.05 endotoxin units per mL. A method of visualizing a tissue or organ of a subject includes the steps of administering to the subject an oxygenated hemoglobin solution as described above, and imaging the tissue, blood vessel or organ with an imaging system. A method of producing an oxygenated Hb solution includes the step of oxygenating a Hb solution that includes polymerized Hb as described above to thereby cause about 80% by weight, or greater, of the polymerized Hb to become oxyhemoglobin.