Prepared by:Madan Baral (8)

Anish Shrestha (9)Krishna Ghimire (10)

Rahul Rana Chhetri (11)

RADIOPHARMACEUTICALS:POSITRON EMMISION TOMOGRAPHY (PET)

Introduction

•PET- Positron Emission Tomography

•Employed since 1970

•Non-invasive method for diagnosis and management of cancer

•Yields high-quality images that characterize substrate metabolism, cellular proliferation, receptor density and other parameters used to identify cancer and evaluate its response to treatment

•Allows the physician to to retain the cerebral physiology of patient through the low resolution “autoradiograph”

•It shows the regional concentration of positron-emitting nuclide inside the living body.

Methodology•R

adiolabelled tracers injected in nonpharmacologic doses are used to construct three dimensional images by computer to demonstrate the location and concentration of the tracer of interest

•Quantitative imaging of regional function and chemical reactions within various organs of the human body

•Application in mapping regional blood flow, oxygen metabolism, regional blood volume, rates of use of metabolic substrates receptor-specific tracer binding, bone remodeling , tumor receptor density, and reporter gene expression

Operation

Types of Tracer Molecules

•Carbon-11

•Nitrogen-13

•Oxygen-15

•Fluorine-18

•Gallium-68

Carbon-11•I

ncorporated into a number of organic molecules like carboxylic acids, alcohols glucose

•Half life is 20 minutes

•Palmitic acid commonly used for myocardial metabolism

•Application: Imaging of cerebral glucose metabolism

Nitrogen-13•1

3N ammonia used for cerebral and myocardial blood flow

•Half life 10 minutes

•Superior than radioactive noble gases due to lower solubility in gases

Oxygen-15•1

5O has too short half life for tracer synthesis

•Half life: 2.04 minutes

•Available radiopharmaceuticals radiolabeled with 15O are

•15Ooxygen gas(15OO): Used for the studies of Oxygen metabolism,

•15O water ( H2

15O): Used for the equilibrium studies of tissue water content

•Carbon monoxide(C15O)

• 15O Carbon dioxide

Fluorine-18•1

8F has long half-life 110 minutes comparatively

•Shows receptor-specific tracer binding

•FDG(2-18F-fluoro-deoxy-D-glucose) major application in imaging of cerebral, myocardial, and tumor metabolism, myocardial and tumor metabolism

•Also cancers of lung and colon and myelomas and lymphomas.

Gallium-68

•Rapidly bound to iron-binding sites

•Application: studies of regional plasma volume also in calculation of regional hematocrit

References

•Loyd V. Allen Nicholas G. Popvich, Howard C. Ansel (2008), Ansel’s Pharmaceutical Dosage Forms and Drug delivery Systems (8th Ed),Walters Klewer ,New Delhi,pp 584-588