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.
 It 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