The preliminary evaluation of Mn DTPA as a potential contrast agent for nuclear magnetic resonance imaging.
The pharmacokinetics of 54Mn administered as Mn-diethylenetriamine pentaacetic acid (DTPA) are being investigated to determine if tissue-specific uptake of manganese could be observed while increasing urinary excretion. This chelation and increased excretion should reduce toxicity. In order to obviate the need for repetitive quantitative nuclear magnetic resonance imaging (NMR) we have substituted tracer amounts of a radioisotope of manganese, Mn-54, for the stable ion. By 6 hours, 58 +/- 7% of the injected dose had been excreted in the urine. Peak liver accumulation occurred within 30 minutes (0.50 +/- 0.14% injected dose/g X kg body weight). The pancreas also showed a relatively high accumulation of tracer (0.25 +/- 0.04%/g X kg body weight), reaching a peak at 4 hours. The pancreas to liver ratios were highest at 6 hours (0.7). There was also a substantial accumulation of the manganese in bile. The blood concentration fell very rapidly with little tracer remaining in the blood at 1 hour. Based on these pharmacokinetics, imaging experiments were conducted before, immediately after, and 9 or 24 hours postinjection. These images showed enhanced kidneys and, later (at 9 hours), an excellent parenchymal-collecting system differentiation. The gallbladder was negatively enhanced. The liver showed either increased or decreased signal strength relative to skeletal muscle depending on the pulse sequence used. We conclude that Mn++, administered as Mn-DTPA, merits further investigation as an NMR contrast agent.
Boudreau
R J
RJ
University of Minnesota Hospitals, Department of Radiology, Minneapolis 55455.
Frick
M P
MP
Levey
R M
RM
Lund
G
G
Sirr
S A
SA
Loken
M K
MK
D000818:Animals; D003287:Contrast Media; D004285:Dogs; D004353:Drug Evaluation, Preclinical; D008279:Magnetic Resonance Imaging; D004369:Pentetic Acid / Q000493:pharmacokinetics; D014018:Tissue Distribution
D003287:Contrast Media; D004369:Pentetic Acid