Hypoosmotic solutions for lymph node detection

A hypoosmotic suspension for medical injection comprising:

• about 13 mg/mL to about 200 mg/mL of superparamagnetic particles;
• and
• an osmolyte selected from either about 0.01% w/v to about 0.6% w/v of an inorganic salt or about 0.5% w/v to about 1.5% w/v of a glycol
• wherein the hypoosmotic suspension has an osmolality of about 80 mOsm/kg to about 160 mOsm/kg.