Showing papers by "Sharmila Majumdar published in 1990"
TL;DR: The in vivo pharmacokinetics and the biodistribution of superparamagnetic iron-oxide particles (AMI25, Advanced Magnetics, Cambridge, MA) were investigated in anesthetized rats and autoradiography showed that the iron was selectively taken up by the cortex.
Abstract: The in vivo pharmacokinetics and the biodistribution of superparamagnetic iron-oxide particles (AMI25, Advanced Magnetics, Cambridge, MA) were investigated in anesthetized rats Four different dose concentrations, ranging from 498 to 4089 mumol of Fe (or 278-2284 mg Fe) per kilogram, radiolabeled with 60 microCi of 59Fe-AMI25 were injected intravenously into 18 rats The radioactivity cleared from the circulation with a fast component with a half-life of approximately 10 minutes and a slower component with a half-life of 92 minutes Both half-lives were independent of the injected dose (ID) in the range of 1054-4089 mumol (589-2284 mg) Fe/kg The relative uptake in the liver, spleen, and kidneys was 57%, 29%, and 20% of the ID, respectively At a dose of 521 mumol (291 mg) of Fe/kg, the relative concentration of iron significantly increased in the liver and decreased in the blood Within the kidney, autoradiography showed that the iron was selectively taken up by the cortex In the kidney, a concentration of 023 mumol (0013 mg) Fe/g resulted in a 30% reduction in image intensity in a single echo magnetic resonance image obtained using a spin-echo sequence and an echo time of 70 ms
63 citations
TL;DR: Simple concepts of indicator‐dilution techniques are described, and the theoretical basis of measuring regional blood flow via transit time measurements of a blood pool marker is discussed, using very fast imaging of the effects of an appropriate and efficient relaxation agent.
Abstract: Simple concepts of indicator-dilution techniques are described, and the theoretical basis of measuring regional blood flow via transit time measurements of a blood pool marker is discussed. Using very fast imaging of the effects of an appropriate and efficient relaxation agent, the concentration-time curve of the agent can be quantified. Preliminary measurements of the transit of superparamagnetic iron oxide through a rat brain at 2.0 T have been obtained. There are problems, however, in relating the NMR signal change to the tissue concentration of an intra vascular relaxation agent when there is not fast exchange of the tissue water with the water in the vasculature, or when the precise efficacy of the agent varies with the geometrical arrangement of the capillaries. Studies of the effects of superparamagnetic iron oxide particles in different media confirm that the in vivo efficacy varies among different tissues, which complicates their use as blood flow markers. © 1990 Academic Press, Inc.
42 citations