Positron emission tomography pet

brief but informative knowledge about what basically PET is and what is the phenomenon behind this machine ... easy to understand as well as presenting during lectures and in classes . share it

1. POSITRON EMISION TOMOGRAPHY SIR SYED UNIVERSITY OF ENGINEERING AND TECHNOLOGY SYED HAMMAD AKHTER 2012-BM-071 PRESENTED TO ENGR. FAHAD AKBER

2. What is PET PET is a noninvasive, diagnostic imaging technique for measuring functional activity of cells in the human body. I t was the first scanning method to give functional information about the brain. It measures metabolic activity, physiology and pathology of human body . It works with the positron Tracer is entered in body

3. What is a Positron? A Positron is an anti-matter electron, it is identical in mass but has an apposite charge of +1 . Positron can come from different number of sources, but for PET they are produced by nuclear decay . Annihilation of a positron and electron The positron will encounter an electron and completely annihilate each other resulting in converting all their masses into energy. This is the result of two photons, or gamma rays. Because of conservation of energy and momentum, each photon has energy of 511keV and head in an almost 180 degrees from each other.

4. Tracer in PET Special form of substance such as glucose in injected in body is FDG (Flouro-dehydroxy glucose ) that collects in cells that are using a lot energy such as cancer cells Why glucose ? When radio pharmaceutical inserted in body. Body consume energy in the form of glucose Tumor has high rate of consumption Working Principle of PET: Positron emitting tracer is injected into the body which emits positrons causing annihilation that results two gamma rays. These rays are detected by opposing detectors. The incident photon is converted into light and converted into electrical signals by PMTs. Then these signal is transfer to amplifier and other electronic circuit.

5. Detectors Same signal acquire at both ends When they were at 180 degrees. Same enegy as well Coincidence Three types True coincidence Scattered coincidence Random coincidence Event detector It defines time ,energy and angle Benefits High spatial resolution Can detect a disease at an earlier stage tha CT or MRI More precise and esthetical that exploring surgery

6. PET scans of Brain PET brain scans show chemical differences in the brain between addicts and non-addicts. The normal images in the bottom row come from non-addicts; the abnormal images in the top row come from patients with addiction disorders. These PET brain scans show that that addicts have fewer than average dopamine receptors in their brains, so that weaker dopamine signals are sent between cells