Quiz 1- Lecture 4: PET Flashcards
What does PET stand for?
Positron emission tomography
What is positron emission tomography (PET) based on?
The physical properties of isotopes- radioactive forms of simple atoms (like hydrogen, oxygen, fluorine, etc.) emitting positrons when they decay
The atoms of each chemical element have a defining and…
BUT CRUCIALLY
Same number of protons and electrons
NOT NEUTRONS, whose numbers can vary
Isotopes are…
Atoms with the same number of protons but different numbers of neutrons
Which is the radioactive isotope?
Protium (1H), Deuterium (2H), Tritium (3H)
Tritium (3H)- 2 NEUTRONS
What is a positron?
Antiparticle of an electron
A positron has all the properties of an electron except for…
Therefore, a positron can simply be considered…
The polarity of the electrical charge, which is POSITIVE
An electron having positive unit electrical charge
What happens whenever an electron and a positron come close?
They annihilate each other and produce energy in the form of photons
Basic properties of positrons (3):
- Rest mass= 9.11x10^-31 kg = 0.511 MeV/c^2
- Electrical charge= +1.602x10^-19 C
- Internal structure: Believed to have no internal structure
Graph:
Each smaller square represents the nucleus of a known…
Black square represents…
All other squares represent…
Stable or radioactive isotope
The stable isotope nuclei
The nuclei of radioactive isotopes
Fluorine F18 (3 characteristics):
- Decays by positron
- (B+) emission
- Has a half-life of 109.7 minutes
What is it called when Oxygen-18 turns to Fluorine-18?
Nuclear transmutation
Adding a proton means…
Going up on diagram
Removing a neutron means…
Going left on diagram
Labels on PET diagram:
- Positron-emitting nucleus
- Positron path
- Positron-Electron annihilation
-Distance between positron-emitting nucleus and positron-electron annihilation is ~ 0.5 mm - annihilation photons on either side of diagram
During 1925-26, quantum theories were proposed that…
HOWEVER
Accurately described the energy levels of electrons in atoms
These equations needed to be adapted to Einstein’s theory of relativity
In 1928, Paul Dirac…
Formulated a fully relativistic quantum theory
What did Paul Dirac’s equation do?
What happened later?
The equation gave solutions that he interpreted as being caused by a particle equivalent to the electron but with a positive charge
This particle, the positron, was later confirmed through experiments
Who was from Tallahassee, Florida?
Paul Dirac
The Nobel Prize in Physics 1933
“For the discovery of new productive forms of atomic theory”
In developing the quantum mechanical theory, Dirac predicted that…
All matter has a kind of mirror image- antimatter
What should a particle and its antiparticle have, if charged?
Opposite charges
By studying the… in a …, in 1932…
Tracks of cosmic ray particles; Cloud chamber; Carl Anderson discovered a positively-charged particle with a mass seemingly equal to that of an electron
Who discovered the positron?
Anderson’s particle…
Carl Anderson (Nobel Prize in Physics 1936)
Was the first antiparticle proven by experiment and was named a “positron”
This wonderful item is a… that was used by… and Seth Neddermeyer between 1935 and 1941 at Caltech
Cloud chamber; Carl Anderson
The cloud chamber served as the…
Prototype for a larger (3 ft diameter) chamber that was carried in a B-29 aircraft from 1948 to 1950 to study cosmic rays at high altitudes
This particular chamber is unusual in that…
What is the advantage provided?
The piston is glass rather than metal
The advantage provided by the glass piston is that it allowed the chamber to be illuminated from below rather than from the side as in conventional designs
