Office: 317-274-1802
Fax: 317-274-8124
Email: emorris@iupui.edu
Web page: http://www.indyrad.iupui.edu/public/emorris/
Research Summary:
Positron Emission Tomography
(PET) measures radioactivity per volume of tissue indiscriminately.
That is, the instrument is unable to identify the source of the
radioactivity in a given macroscopic location - be it from a radioactive
molecule in the microcirculation or floating freely in the extracellular tissue
space or from a labeled ligand locked in the clutches of a receptor molecule.
This microscopic attribution of radioactivity signal to one or another
'state' of the injected ligand is the province of the mathematical model.
In PET, 30 years experience has lead us to conclude that compartmental
models are adequate to describe the dynamics of our data.
These models, which ignore local concentration gradients smaller than the
voxel dimensions, can be encoded entirely with ordinary differential equations (ODEs)
and are the stock and trade of PET modelers.
Recently modelers have focused on the ability of PET to non-invasively
detect and measure not only the exogenous radioactive species
- but by mathematical inference - changes to the endogenous species that
compete with the injected tracer - say at a receptor site.
Dr. Morris and colleagues are currently engaged in developing new
analysis techniques (i.e., new compartmental models and parameter estimation
schemes) and in optimization of imaging study protocols to extract the maximum
amount of relevant information about neuromodulation from dynamic PET images.
In particular, Morris et al. have begun working with researchers in the
Alcohol Research Center to investigate changes in neurotransmitters in response
to alcohol.
If you would like to learn more about neuroimaging with PET and modeling, Dr. Morris invites you to attend his PET Journal Club. See his web site for a link.
Publications
Morris, E.D.,
R.E. Fisher, N.M. Alpert, S.L. Rauch, A.J. Fischman (1995): In Vivo Imaging of
Neuromodulation Using Positron Emission Tomography: Optimal Ligand
Characteristics and Task Length for Detection of Activation. Human
Brain Mapping. 3:35-55.
Morris, ED, SI Chefer, MA Lane, RF Muzic Jr., DF Wong, RF Dannals, JA Matochik, AA Bonab, VL Villemagne, SJ Grant, DK Ingram, GS Roth and ED London. (1999): Loss of D2 Receptor Binding with Age in Rhesus Monkeys: Importance of Correction for Differences in Striatal Size. J Cereb Blood Flow & Metab 19:218-229.