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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.


Journal article


Magn Reson Med

Publication Date





787 - 789


4-Aminopyridine, Animals, Contrast Media, Dogs, Gadolinium DTPA, Image Processing, Computer-Assisted, Kidney, Magnetic Resonance Imaging, Methemoglobin, Organometallic Compounds, Pentetic Acid, Rabbits