The Development of a pH-sensitive contrast agent for NMR 1H imaging

✍ Scribed by Joseph A. Helpern; Jeff C. Curtis; David Hearshen; Jmichael B. Smith; Kenneth M. A. Welch

• Publisher: John Wiley and Sons
• Year: 1987
• Tongue: English
• Weight: 220 KB
• Volume: 5
• Category: Article
• ISSN: 0740-3194
• DOI: 10.1002/mrm.1910050313

✦ Synopsis

Fe(III)meso-tetra(4-sulfonatophenyl)porphine (Fe-TPPS4) has been investigated as a potential pH-sensitive nuclear magnetic resonance (NMR) proton image contrast agent. Relaxation rates (1/T1 and 1/T2) of water protons were measured as a function of pH and concentration of Fe-TPPS4 in phosphate-buffered isotonic saline. Transverse relaxation rates (1/T2) did not change appreciably with pH above 6.0. Longitudinal relaxation rates (1/T1) increased significantly between pH 7.75 and 5.75. This effect was more pronounced with the increasing concentration of Fe-TPPS4 from 0.1 to 1.5 mM and is attributed to a pH-dependent equilibrium between the high-spin (S = 5/2) Fe-TPPS4 monomer at low pH and the antiferromagnetically coupled mu-oxodimer O-(FeTPPS4)2 at high pH. The efficacy of this pH-dependent contrast agent is demonstrated in vitro.