PRELIM 2 Flashcards
atomic mass (number of nucleons)
A
atomic number (number of protons)
Z
element symbol
X
Two Forces Acting on Electrons
-Centrifugal Force
-Attractive Force
Two Forces Acting on the Nucleus
Repulsive Force (due to protons)
Nuclear Binding Force(due to neutrons)
-amount of energy that must be supplied to a nucleus to completely separate its nuclear particles (nucleons).
-the amount of energy that would be released if the nucleus was formed from the separate particles.
-Binding energy is the energy equivalent of the mass defect.
Electron Binding Energy
is the minimum energy required to remove the electron from an atom
electron binding energy
is a form of energy traveling through a medium or space. It travels as waves or subatomic particles through air, water or solid materials.
Radiation
Forms of Radiation
A. Particulate-
B. Electromagnetic
distance from the peak of one wave to the peak of another.(1 angstrom=10 ^ -10 m)
wavelength
is the number of waves per second that a stationary observer would count while the wave is passing by
Frequency
Invisible
Electrically neutral
No mass
Travel at the speed of light in a vacuum
Cannot be optically focused
Form a polyenergetic or heterogenous beam
Can be produced in a range of energies
Travel in straight lines
X-ray Properties
-also known as “path length“
-maximum distance traversed by ionizing radiation in interacting medium
-measured in micron or micrometer (µm)
Range
the ave. number of ions generated per unit length of path
Specific ionization
The energy transferred by ionizing radiation per unit path length of the interacting medium.
LET/ Linear Energy Transfer
-Property of some atoms to spontaneously give off energy as particles or rays from the nucleus
-Caused by instability in the atom’s nucleus or an excess of energy
Radioactivity/Radioactive Decay
Types of Radioactivity
-natural
-artificial
happens by itself. (naturally existing radioactive elements)
natural
is induced in the laboratory (with the help of cyclotron)
Artificial
Forms of Atomic Nucleus
-IsotoPes
-IsobArs
-IsotoNes
-IsomErs
Atoms having the same number of protons but different number of neutrons
IsotoPes
Same number of nucleons but different number of protons
IsobArs
- Same number of neutrons but different number of protons.
IsotoNes
Contains same number of protons as well as same number of neutrons but the energy level of the nucleus is different
IsomErs
Modes of Decay
-Alpha Emission/Decay (α-decay)
-Beta Decay/Emission
-Occurs in heavy nuclides with high atomic number
-It resembles the Helium (He) element
-The relative charge of alpha is 2 and a mass of 4
Alpha Emission/Decay (α-decay)
-has low penetrating power and most harmful internally and less harmful externally.
-it can be stopped by a piece of paper or cloth.
Alpha radiation
-The relative charge of -1 and a mass of 0.
-has a moderate energy and it can be stopped by approximately 0.5mm aluminum or lead.
The β-decay
Has two sub-modes:β-decay
Negatron emission
Positron emission.
-This occurs when there are too many neutrons.
-It occurs when a radioactive nuclide with high Neutron and Proton ratio disintegration
-This particle emitted is a negatively charge high speed electron which originated in the nucleus.
-This electrons results from the conversion of the excess neutron into proton.
Negatron Emission
-It occurs when the radioactive nuclide with an excess of Proton disintegrates
-The particle emitted is positively charged electron which comes from the nucleus
-This results from the transformation of the excess proton to a neutron
-With Positron emitter, the parent nucleus gives up positive charge resulting in a daughter less positive by one unit of charge.
-The atomic number decrease by one and the mass number remains unchanged.
Positron Emission or Beta Positive emission
Alternative to positron decay for neutron-deficient radionuclides
Nucleus captures an orbital (usually K- or L-shell) electron
Electron Capture/ K-Capture
-During radioactive decay, a daughter may be formed in an excited state
-Gamma rays are emitted as the daughter nucleus transitions from the excited state to a lower-energy state
Isomeric Transition
Examples of some gamma emitters:
iodine-131, cesium-137, cobalt-60, radium-226, and technetium-99m.
is the removal of an electron by a gamma ray during isomeric transition.
Internal Convesion
is the removal of an electron by a characteristic ray during electron capture.
Auger process
What are the types of radiation:
-alpha
-beta
-gamma
-positron
-xray
-neutron
Mass (u) & charge: alpha
4
+2
Mass (u) & charge: beta
1/1840
-1
Mass (u) & charge: gamma
0
0
Mass (u) & charge: positron
1/1840
+1
Mass (u) & charge: xray
0
0
Mass (u) & charge: neutron
1
0
The time taken for the number of atoms in a sample of an element to decay by half
Half-life (T1/2)
The time required for the body to eliminate one half of the dose of any radioactive substance.
Effective Half-life
The length of time required for one half of the original number of atoms in a given radioactive sample to disintegrate.
Physical half-life(T1/2)
The time required for the body to eliminate one half of the dose of any substance by the regular process of elimination
Biologic half-life(TB):
Indicates the number of radionuclides disintegrating per second (dps or s-1)
Activity (A)
SI unit for radioactivity
Bq- becquerel
Old unit for radioactivity
curie (Ci)
1 Bq =
1 disintegration per second (dps)
1 Ci =
3.7 x 10^10 Bq
37GBq
quantities which describe the radiation field (in terms of particles or rays) & the quantity of ionization produced
Radiometric Quantities
Radiometric Quantities are:
Energy
Fluence
Exposure
Kerma
SI unit is Joules (J)
energy of ionizing radiation is measured in terms of electronvolts (eV)
energy
1 eV =
1.6 x 10 ^ -19 J
-number of particles (or photons) passing through unit area
-measured in particles per square metre (m-2)
Fluence (F)
is the number of particles passing through unit area in unit time
Fluence rate
-amount of ionization produced in air
originally called the roentgen (R), named after the discoverer of x-rays, Wilhelm Roentgen
-SI unit of exposure is the coulomb per kilogram (C/kg)
Exposure (X)
1 R =
2.58 x 10^-4 C/kg of air
-kinetic energy released per unit mass of absorber
-a measure of the kinetic energy of charged particles produced in an absorbing medium by uncharged radiation (i.e. photons and neutrons)
Gray (Gy)
Kerma (K)
1 Gy =
1 J / kg
Dosimetric quantities are:
-absorbed dose
-Equivalent dose
-Symbol is D
-Defined as the energy absorbed per unit mass from any kind of ionizing radiation in any target
absorbed dose
The S.I. unit is gray (Gy) = 1 joule per kilogram
Old unit is the rad
absorbed dose
100 rad =___Gy
1 Gy
Symbol is H
A measure of the biological effects of a particular type of radiation on organs or tissues
Equivalent Dose
Calculated by: H = D x WR ,
Equivalent Dose
WR =
radiation weighting factor
The S.I. unit is sievert (Sv) = 1 joule per kilogram
Old unit is the rem
Equivalent Dose
1 Sv = ___ rem
100 rem
alpha particles, all energies: WR
20
beta particles, all energies:WR
1
γ & x-rays, all energies:WR
1
Neutrons: < 10 keV
10 keV– 100 keV
> 100 keV – 2 MeV
> 2 MeV – 20 MeV
> 20 MeV
5
10
20
10
5
-Symbol is E
-A measure of the effect of a particular type of radiation on organs or tissues.
-Takes into account theradiosensitivities of different tissues or organs
Effective Dose
Calculated by: ET = HT x WT ,
Effective Dose
*WT =
tissue weighting factor
The S.I. unit is sievert (Sv)
Effective Dose
1 sievert (Sv) = _____ joule per kilogram
1
WT:0.12
summation WT:0.72
Bone-marrow (red), Colon, Lung, Stomach, Breast, Remainder tissues*
WT:0.08
summation WT:0.08
gonads
WT:0.04
summation WT:0.16
Bladder, esophagus, Liver, Thyroid
WT:0.01
summation WT:0.04
Bone surface, Brain, Salivary glands, Skin
summation total of tissues
1
5 Interaction with Matter
Coherent Scattering ( Thomson Scattering )
Photoelectric Effect
Compton Scattering
Pair Production
Photodisitegration
-Aka Classical, Thomson, unmodified
-Produced by a low energy x ray photon
-Incident x ray interact with target atom
-Target atom release excess energy as scatter
-There is a change in direction of but does not change the energy
-No excitation happened
Coherent Scattering ( Thomson Scattering )
-Photon Absorption interaction
-Photon undergo interaction with inner shell electron
-Photon energy is transferred to the electron
-Photon is completely absorbed
-Photoelectron in created in the process
Photoelectric Effect
-Also called Compton Scattering or modified scattering
-Incoming x ray photon interacts with loosely bound, outer-shell electron
-Photon scatter in another direction with less energy.
-This scattered photon may interact with other electron causing more ionization
Compton Interaction
-Does not occur in radiography
-This is produced by photon energy greater than 1.02 MeV
-High energy photon comes close to the strong nuclear field and lose all energy that energy is used to create a pair or electron negatron and positron
Pair Production
-Does not occur in diagnostic radiology
-Interaction with extremely high energy photon greater than 10 MeV
-This strikes the nucleus and all of the energy is absorbed and exciting the nucleus
-This excitation will produce the nuclear fragment
Photodisintegration