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The following message was posted to: PharmPK
Hi
I would like to hear from anyone who has experience with fMRI and
particularly relating plasma drug concentration to whatever
measurement can be obtained from fMRI of the brain. Our specific
interest is in SSRIs but information on any drugs would be of
interest.
Thanks
Leon Aarons
Leon Aarons
School of Pharmacy and Pharmaceutical Sciences
University of Manchester
Manchester, M13 9PL, U.K.
tel +44-161-275-2357
fax +44-161-275-2396
email leon.aarons.at.man.ac.uk
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The following message was posted to: PharmPK
Leon:
I would be very interested in hearing what answers you get.
Let me make some comments to the whole group. fMRI and Functional
studies using MRI are not identical.
fMRI is a method where the measurements are based on the difference
between oxy-hemoglobin and de-oxyhemoglobin, and hence, the difference
in the concentration of Fe+3 as an MRI relaxing agent. fMRI is used to
measure physiological changes in a given target site (and hence, can
give pharmacodynamic information), but they are not suitable for
pharmacokinetic studies.
Functional studies using contrast agents, such as Dynamic Contrast
Enhanced MRI (DEMRI or DCE-MRI) give you a completely different set of
information. They measure the rate and the intensity of contrast
enhancement of any given region-of-interest (ROI) following
administration of a dose of the contrast agent, both in the very early
input phase, as well as in the later elimination phase. DEMRI is a good
method to measure the rate of drug distribution using the contrast
agent as an indicator for other solutes. However, because most MRI
contrast agents do not penetrate into cells (they are ionic products)
they have much more limitation in measuring drug retention and
elimination. For that, you have to use a spectroscopic approach (if you
can measure your drug by noninvasive MRS), or a nuclear imaging
approach (if you can intrinsically radiolabel your drug).
Professor Walter Wolf, Ph.D. Distinguished Professor of Pharmaceutical
Sciences
Director, Pharmacokinetic Imaging Program
Department of Pharmaceutical Sciences, School of Pharmacy
University of Southern California 1985 Zonal Ave., Los Angeles, CA
90089-9121
E-Mail: wwolfw.at.usc.edu
Telephone: 323-442-1405
Fax: 323-442-9804
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