The present invention provides an aqueous excipient solution suitable for diluting a diagnostic composition comprising a contrast agent. The excipient solution comprises a sodium ion concentration of about 100 140 mM and a calcium ion concentration of about 0.8 1.2 mM. Alternatively the molar ratio between sodium ion concentration and calcium ion concentration is between about 80 and 175. Also provided are methods of making and using the excipient solution as well as a kit comprising the excipient solution.
