P1 Flashcards
Fundamental building blocks of matter
Atom
Smallest particle of an element
Atom
Electron is discovered by
John Joseph
Thomson
Proton is discovered by
Ernest Rutherford
Neutron is discovered by
James Chadwick
Consists of same number of protons
and electrons
Neutral atom
– Consists of an extra or a lacking of e
– Can be positive or negative
Ionized Atom
Consists of electrons
Orbital shell
Central core of an atom
Nucleus
Contains nearly all mass of the
atom
Nucleus
Number of electron (outermost shell)
‒GROUP NUMBER
‒VALENCE STATE
• Number of outermost electron shell
PERIOD NUMBER
The strength of attachment of an
electron to the nucleus
Electron Binding energy
The energy required to completely
remove an electron from the atom
Electron Binding Energy
The number of protons in an atom
Atomic number
The number of protons and neutrons
Atomic mass number
The difference between the
atomic mass number and atomic
number
Neutron number
‒ Atoms having nuclei with the same number of protons but different number of neutrons
Isotopes
‒ Having the same number of neutrons but different number of protons
Isotones
‒ Same number of nucleons but different number of protons
Isobars
‒ Same number of protons as well as neutrons.
Isomers
‒ Represents identical atoms except that they differ in their nuclear energy states.
Isomers
Radioactivity is first discovered by ____
in ____.
Antonio Henri Becquerel, 1896
A phenomenon in which radiation is given off by the nuclei of the elements
Radioactivity
This radiation can be in the form of particles, electromagnetic radiation, or both
Radioactivity
is the spontaneous emission of particles
and energy in order to become stable.
Radioactivity
The atoms involved in radioactivity are
radionuclides
Any nuclear arrangement is called a ___; only nuclei that undergo radioactive decay are ____.
nuclide, radionuclides
An unstable atomic nucleus sheds its excess energy in the form of either an _____.
If it still possesses excess energy after that, _____ are emitted in order to reach its steady state.
intranuclear electron (e−) (beta particle)
or a helium nucleus (an “alpha particle”)
gamma rays
‒ Original radionuclide
‒ Very unstable
‒ Longer half-lives
‒ Excited stated
PARENT
‒ Resulting radionuclide
‒ More stable
‒ Shorter half-lives
‒ Ground state
DAUGHTER
The time required for a quantity of
radioactivity to be reduced to one-
half its original value.
Physical Half life
The time required for the body to eliminate one-half of the dose of any substances by biological processes.
Biological half life
A combination of both T1/2 and Tb
Effective half-life
The time required for half of initial radioactivity to disappear from an organ or body by combination of excretion and physical decay
Effective half-life
Must always shorter than T1/2 or Tb
Effective half-life
Formula of the effective half-life
Formula: 1/Te= 1/T1/2 x 1/Tb / 1/T1/2 + 1/Tb
due to their negative charge and low mass, can be accelerated to high energies in linacs or betatrons.
Electrons
are normally bound to a (positively charged) nucleus.
Electrons
The number of electrons is equal to the number of protons in a ____ atom
neutral
all interact with matter by electrical forces and lose kinetic energy via excitation, ionization, and radiative losses.
Energetic charged particles
occur when charged particles lose
energy by interacting with orbital electrons.
Excitation and ionization
Excitation and ionization occur when charged particles lose energy by interacting with orbital electrons. These interactional, or collisional, losses refer to the ____ exerted on charged particles when they pass in proximity to the electric field generated by the atom’s electrons and protons.
coulombic forces
is the transfer of some of the incident particles’ energy to electrons in the absorbing material, promoting
them to electron orbits farther from the nucleus (i.e., higher energy level).
Excitation
Occurs when energy transferred to an
electron does not exceed its binding
energy
Excitation
Following excitation, _____ occurs as the electron returns to a lower energy level releasing energy
de-excitation
Occurs when transferred energy exceeds the binding energy
Secondary Ionization
Electron is ejected from the atom
Secondary Ionization
Secondary Ionization results in an _____ consisting of an ejected electron and a
positively charged atom
ion pair
Secondary ionization occurs when the ejected electron has sufficient energy to produce further ionization, these
electrons are called
delta rays
As electron energy ______, the probability of energy loss via excitation _____.
decreases, increases
The number of primary and secondary ion pairs produced per unit length of the charged particle’s path is expressed in
_____
ion pairs (IP)/mm
As the alpha particle slows, the specific ionization increases to a maximum called the
Bragg peak
follow tortuous paths in matter as the result of multiple scattering events caused by coulombic deflections
(repulsion and/or attraction).
Electrons
Heavy charged particle results in a dense and usually ___ ionization track
linear
A particle that has a larger mass results in a dense and usually linear ionization track.
Alpha
‒Defined as the actual distance the particle travels.
Path length of a particle
‒Defined as the actual depth of penetration of the particle in matter.
Range of a particle
The path length of the ___ almost always exceeds its range.
electron
The path length and range of the ____ is being nearly equal
alpha particle
The amount of energy deposited per unit path length.
LINEAR ENERGY TRANSFER
LET is usually expressed in units of
eV/cm.
LET of a charged particle is ____ to the square of the charge and ____ to the particle’s kinetic energy.
proportional, inversely proportional
is the product of specific ionization (IP/cm) and the average energy deposited per ion pair (eV/IP).
LET
It is the result of interaction where the particle or photon deflects from its original path/trajectory.
Scattering
Scattering events in which the total kinetic energy of the colliding particles is unchanged is called
Elastic Scattering.
Scattering events that occurs with a loss of kinetic energy, the interaction is said to be
Inelastic Scattering
The radiation emission accompanying electron deceleration is called ___, a German word meaning ____
bremsstrahlung, braking radiation”
The deceleration of the high-speed electrons in an x-ray tube produces the
bremsstrahlung x-rays.
occurs when an electron ( e − ) and a positron ( e + , the electron’s antiparticle) collide.
Electron–positron annihilation
happens when an X-Ray photon comes in, interacts with electron cloud and goes out. The X-Ray is scattered after this interaction but it has the same energy as it leaves.
Coherent Scattering/ Rayleigh/ Elastic
— Involves all of the electrons of
the atom in the interaction
Rayleigh Scattering
— Involves a single electron of the
atom in the interaction
Thomson Scattering:
(also called inelastic or nonclassical scattering) is the predominant interaction of x-ray and gamma-ray photons in the diagnostic energy range with soft tissue.
Compton scattering
This interaction is most likely to
occur between photons and
outer (“valence”) shell electrons.
Compton Scattering
Most common but the least desirable photon interaction
Compton Scatter
Results:
— Scattered x-ray
— Compton electron
— Change in direction
— Change in energy, frequency and
wavelength
Compton Scatter
In compton scattering with ____ of deflection , scattered x-ray retains at least 2/3 of its energy
180 degree
In compton scattering with ____ of deflection , no energy is transferred to Compton electron
0 degree
In compton scattering, an increased angle of deflection would cause ____ energy transferred to Compton electron
more
In Compton Scattering, a decrease angle of deflection would cause ___ energy transferred to Compton electron
less
Occurs when an incident x- ray
photon interacts with a tightly bound
electron
Photoelectric effect
Low-energy x-ray photons gives up
all its energy ejecting an inner-shell
electron
Photoelectric effect
Results:
—No scattered x-ray
—Photoelectron
—Total x-ray absorption
—Secondary x-rays
Photoelectric effect
▪ Major contributor to patient dose
▪ Production of high contrast image
Photoelectric effect
Photoelectric effect predominates in the lower energy ranges produced by ___ kVp
40-70
The conversion of a neutron boson into a subatomic particle and its antiparticle
Pair production
Occurs only with very-high- energy
photons of 1.02 MeV or greater
Pair Production
▪ Does not occur in radiography
▪ Useful in nuclear medicine
Pair production
Results:
▪ Incident photon disappears
▪ Incident photon is converted to
matter (pair electrons)
— Negatron
—Positron
▪ Annihilation reaction
Pair Production
Identical to a helium nucleus
Alpha Particle
Heaviest and least penetrating
form of radiation
Alpha
Carries an electronic charge
twice that of the proton
Alpha
Occurs in all radionuclides
Beta decay
Occurs much more frequently than
alpha particle
Beta decay
2 types of beta particle
Beta minus
Beta plus
Identical to electrons
Beta particle
The existence of neutrinos and antineutrinos was first suggested by ___ in ____, although it was ___ that provided
the name “neutrino”
Pauli, 1930, Fermi
Method of radioactive decay
that involves the capture of an
orbital electron most likely in
the K or L- shell by its nucleus
Positron decay
Similar to positron decay
Electron capture
There is no change in the atomic or mass number of the nucleus after the gamma decay, so it is termed an “ ____ ”
decay.
isomeric
A nucleus is not always fully stable (i.e., at its basal energy level) just after it decays; sometimes, the nucleus will be in a semi-stable state instead. The excess energy carried by the nucleus is then emitted
as ____ radiation.
gamma
