Evaluation of methemoglobin as an autologous intravascular MRI contrast agent.
Methemoglobin (MetHb) was evaluated as an intravascular paramagnetic contrast agent. Methemoglobin formation was induced by 4-dimethylaminophenol (4-DMAP), causing a reduction in blood T2* in vitro. The 4-DMAP generated metHb with a time constant of 62 s. A 4-DMAP bolus did not decrease measurably the signal intensity in the in vivo rabbit kidney in the first pass. At steady state, a MetHb concentration of 24.8 +/- 2.3% resulted in a signal decrease of 9.2 +/- 2.6% in the kidney. Methemoglobin is an effective vascular T2* relaxation agent, but the formation of MetHb by 4-DMAP is too slow for first-pass imaging. A more effective conversion agent resulting in a bolus of at least 25% MetHb within 5 s would result in a detectable first-pass signal and a viable contrast technique.
Duewell
S
S
Laboratory of Cardiac Energetics, National Heart, Lung and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
Kasserra
C E
CE
Jezzard
P
P
Balaban
R S
RS
D015761:4-Aminopyridine / Q000031:analogs & derivatives; D000818:Animals; D003287:Contrast Media; D004285:Dogs; D019786:Gadolinium DTPA; D007091:Image Processing, Computer-Assisted; D007668:Kidney / Q000033:anatomy & histology*; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008706:Methemoglobin; D009942:Organometallic Compounds; D004369:Pentetic Acid / Q000031:analogs & derivatives; D011817:Rabbits
D003287:Contrast Media; D009942:Organometallic Compounds; D004369:Pentetic Acid; D008706:Methemoglobin; D015761:4-Aminopyridine; D019786:Gadolinium DTPA; C003885:4-dimethylaminopyridine