A method for making a composition, comprising: selecting one or more solutions containing one or more nonradioactive contrast-enhancing agents; concentrating the one or more solutions by at least about 10% from 350 mg I/mL to at least 400-450 mg I/mL to produce a concentrated solution of the nonradioactive contrast-enhancing agents; forming sterically stabilized liposomes comprising: a phospholipid, a phospholipid which is derivatised with a polymer chain, and cholesterol in the presence of the concentrated solution of the one or more nonradioactive contrast-enhancing agents to provide a solution of the sterically stabilized liposomes that contains or is associated with the one or more nonradioactive contrast-enhancing agents; and concentrating the liposomal solution to an iodine concentration of over 85 mg I/mL, the one or more nonradioactive contrast-enhancing agents being located or associated with internal cavities of the liposomes; wherein the one or more nonradioactive contrast enhancing agents comprise iohexol; wherein the phospholipid comprises 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC); the phospholipid which is derivatized with a polymer chain comprises N-(carbonylmethoxypolyethyleneglycol2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-MPEG2000); and wherein the DPPC, cholesterol and DSPE-MPEG2000 are in a 55:40:5 molar ratio. selecting one or more solutions containing one or more nonradioactive contrast-enhancing agents; concentrating the one or more solutions by at least about 10% from 350 mg I/mL to at least 400-450 mg I/mL to produce a concentrated solution of the nonradioactive contrast-enhancing agents; forming sterically stabilized liposomes comprising: a phospholipid, a phospholipid which is derivatised with a polymer chain, and cholesterol in the presence of the concentrated solution of the one or more nonradioactive contrast-enhancing agents to provide a solution of the sterically stabilized liposomes that contains or is associated with the one or more nonradioactive contrast-enhancing agents; and concentrating the liposomal solution to an iodine concentration of over 85 mg I/mL, the one or more nonradioactive contrast-enhancing agents being located or associated with internal cavities of the liposomes; wherein the one or more nonradioactive contrast enhancing agents comprise iohexol; wherein the phospholipid comprises 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC); the phospholipid which is derivatized with a polymer chain comprises N-(carbonylmethoxypolyethyleneglycol2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-MPEG2000); and wherein the DPPC, cholesterol and DSPE-MPEG2000 are in a 55:40:5 molar ratio. a phospholipid, a phospholipid which is derivatised with a polymer chain, and cholesterol in the presence of the concentrated solution of the one or more nonradioactive contrast-enhancing agents to provide a solution of the sterically stabilized liposomes that contains or is associated with the one or more nonradioactive contrast-enhancing agents; and concentrating the liposomal solution to an iodine concentration of over 85 mg I/mL, the one or more nonradioactive contrast-enhancing agents being located or associated with internal cavities of the liposomes; wherein the one or more nonradioactive contrast enhancing agents comprise iohexol; wherein the phospholipid comprises 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC); the phospholipid which is derivatized with a polymer chain comprises N-(carbonylmethoxypolyethyleneglycol2000)-1,2-distearoyl-sn-glycero-3-phosphoethanolamine (DSPE-MPEG2000); and wherein the DPPC, cholesterol and DSPE-MPEG2000 are in a 55:40:5 molar ratio.