Neuroimaging Laboratory Exercise - Background Information

Neuroimaging Laboratory Exercise - Background Information -...

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Bio 335 Neuroimaging 1 Neuroimaging Laboratory Exercise Positron Emission Tomography (PET) Data Analysis I. Learning Objectives In this exercise you will examine and analyze human neuroimaging data that was collected at Brookhaven National Laboratory. The imaging technique you will learn about is called Positron Emission Tomography (PET). You will be given real PET scan data as image files collected from subjects, first following administration of a placebo, and then after a drug called Modafinil. You will then compare the two brain scans and learn how to quantify the effect of the drug on elements of the dopamine neurotransmitter pathway. The goals of this exercise are to: See and analyze real neuroimaging data, first hand Learn some neuropharmacology of the dopamine system Appreciate how PET is used for clinical and research purposes Use a graphical analysis method to quantify PET data II. How does a PET scan work? PET detects and locates radioactivity. A subject undergoing a PET scan will be injected with a radiotracer – a molecule or drug that has been labeled with a radioactive atom. It is important to note that this label does not change the initial chemical properties of the molecule. When the radiotracer is a ligand – a molecule that binds to a specific protein – it will bind to its target just like the unlabeled version can. But because the radiotracer is given at very low concentrations (binding less than 5-10% of the available sites), it does not perturb the system you are trying to measure. Instead, the radiotracer gives you a representation of how many target proteins are available to bind. The most common radioactive atoms used for PET scans are given in the table below which shows their half life, and what they turn into when they undergo beta + decay, where a β + particle (aka – positron) is emitted from the nucleus. The decay products are not harmful and the molecules can be normally cleared from the body. Table 1. Half-life of common PET isotopes Isotope Half-life (min) Decay product Carbon-11 20.4 Boron-11 Fluorine-18 110 Oxygen-18 Nitrogen-13 10 Carbon-13 Oxygen-15 2 Nitrogen-15 The PET camera can detect radioactive decay events in the brain or body and pinpoint their locations. This information can be obtained in all 3 spatial dimensions, and over the time course of the scan. Just like any other molecule or drug that enters your blood stream,
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Bio 335 Neuroimaging 2 radiotracer ligands will travel throughout the body, but they will accumulate in areas where their protein targets are enriched and available, thus increasing radioactivity in that region. III. Using PET to study a neurotransmitter system PET can be used to study the mechanism of action of a drug in vivo , in live subjects.
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This note was uploaded on 12/06/2011 for the course BIO 335 taught by Professor Cabot during the Fall '08 term at SUNY Stony Brook.

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Neuroimaging Laboratory Exercise - Background Information -...

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