MRI contrast agents endowed with concentration independent responsiveness
AssigneeBracco Imaging S.P.A.
InventorsSilvio Aime, Enzo Terreno
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Abstract
The present invention relates to a method for the in vivo, ex vivo, or in vitro determination of physical or chemical parameters of diagnostic interest by use of a slow tumbling paramagnetic agent that is responsive to changes of said physical or chemical parameter through changes in the R2p/R1p ratio allowing the determination of the said parameter in a manner that is independent on the actual agent concentration.
Claims9
A method for the in vivo determination, by use of the MRI technique, of the value of a physical or chemical parameter of diagnostic interest selected from the group consisting of temperature, pH, partial pressure of oxygen or carbon dioxide, specific ion or metabolite concentration and specific enzymatic activity in a human or animal body organ, fluid or tissue, said method comprising:
- administering to said human or animal a diagnostically effective amount of a slow tumbling paramagnetic agent that is a nano-sized system comprising a liposome entrapping HPDO3A complexed with a paramagnetic metal in an inner aqueous phase at a minimum concentration of 5 mM, and having a mean diameter ≧5 nm;
- recording a MRI image;
- calculating the R2p/R1p ratio, which acts as a reporter of a change in the parameter of interest;
- and
- determining the value of the parameter of interest through the obtained R2p/R1p ratio.
A method for the in vivo determination, by use of the MRI technique, of the value of a physical or chemical parameter of diagnostic interest selected from the group consisting of temperature, pH, partial pressure of oxygen or carbon dioxide, specific ion or metabolite concentration and specific enzymatic activity in a human or animal body organ, fluid or tissue, said method comprising:
- administering to said human or animal a diagnostically effective amount of a slow tumbling paramagnetic agent that is a macromolecular paramagnetic metal complex endowed with at least one labile water molecule coordinated to the metal center, having a τR value from 1 to 10 ns and a τM value from 0.01 to 1 μs, and including a polyamino acid;
- recording a MRI image;
- calculating the R2p/R1p ratio, which acts as a reporter of a change in the parameter of interest;
- and
- determining the value of the parameter of interest through the obtained R2p/R1p ratio.
Dependencies are inferred from the claim text.