Medical dyes for diagnosis, namely, contrast agents for diagnostic imaging, medical preparations, namely dyes for fluorescence imaging to monitor physiological functions, such as blood flow and tissue perfusion; medical dyes encapsulated in carriers for administration into a patient's body in order to monitor physiological functions, such as blood flow and tissue perfusion; kits comprising medical dyes and carriers for the medical dyes for administration to a human or animal; therapeutic agents namely radiation absorbing dyes encapsulated within a carrier; kits comprising medical dyes and reagents for preparing carriers for the medical dyes