but also cleaves the thiol protecting group all of the aforementioned thiol protecting groups are cleaved by a reaction of salts of radioactive metals in accordance with this invention in forming the complex the radioactive material has a suitable amount of radioactivity in forming the tc 99m radioactive anionic complexes it is generally preferred to form radioactive complexes in solutions containing radioactivity at concentrations of from about 0 01 millicuries mci to 100 mci per ml the complex can be used for visualizing organs such as the kidney for diagnosing disorders in these organs tumors and blood clots can also be imaged in accordance with this invention the anionic complex either as a complex or as a salt with a pharmaceutically acceptable cation is administered in a single unit injectable dose any of the common carriers such as sterile saline solution plasma etc can be utilized after the radiolabeling for preparing the injectable solution to diagnostically image various organs clots tumors and the like in accordance with this invention generally the unit dose to be administered has a radioactivity of about 0 01 mci to about 100 mci preferably 1 mci to 20 mci the solution to be injected at unit dosage is from about 0 01 ml to about 10 ml after intravenous administration imaging of the organ in vivo can take place in a matter of a few minutes however imaging can take place if desired in hours or even longer after injecting into patients in most instances a sufficient amount of the administered dose will accumulate in the area to.