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Lambda, nu (v), and 'c' ?
wavelength, frequency, and velocity
Unstable ____ ____ tend to seek their ground state, meaning that they tend to give off their excess ____ until they reach a point at which the energy in the nucleus is just enough to maintain ____ ____. The process by which they lost this energy is called____?
- atomic nuclei
- nuclear stability
An alpha particle consists of two ____ and two ____ bound together; this is equivalent to a ____ ____ (Z=2) that has been stripped of its two ____.
- helium atom
Large, unstable atoms that have a large amount of excess energy tend to undergo ____ ____ by the emission of ____ particles.
What energy often appears in the form of photons because of their nuclear origin?
A beta-minus particle is the same as an ____.
An electron is found orbiting in the elctron shells whereas a beta-minus particle is ?
emitted as the result of a nuclear decay
There is a subatomic particle that has the exact same characteristics as an ____, except that is possesses a positive electrical charge rather than a ____ charge. This particle is called a ____.
An electron that strays too close to the nucleus may be ____ and combined with a ____, reversing the process for ____-____ decay. This process is known as ____ ____.
- electron capture
The lambda symbol is a value known as the ____ ____ ____.
exponential decay constant
226 Ra has a half-life of more than ____ years, whereas the half-life of the daughter 222 Rn is only approx. ____ days.
Kinetic energy is ?
energy caused by its motion through space
because of the proximity of the ____ shell to the nucleus, it is most likely that the captured ____ will be taken from this shell
When an electron is taken from one of the electron shells, it leaves a ____ in the shell; this will place the atom in an ____ configuration in terms of energy..
one of the electrons from an outer shell will ____/____ toward the nucleus moving from a higher energy state to a lower one and this excess energy no longer needed to maintain stability, will be given off in the form of an ____.This type of radiation is called ____ ____?
- characteristic radiation
____ ____ is an important part of many radioactive decay schemes and radiation/matter interactions.
The amount of ____ present in a given sample is ____ a constant quantity but rather is being ____ continuously by the decay of the radioactive ____ in the sample.
Any value that increases or decreases exponentially will double or halve its value within a certain amount of time; when that time interval passes again, the value will have further reduced by half or increased by two times. This is known as?
The lambda is a ____ for a given ____, that is, all atoms of a given isotope will decay with the same ____, which will ____ change no matter what environmental conditions persist.
The ____-____ is the time required for the activity of any sample of a particular ____ to decay of half of its initial value.
A quantity called the ____ ____ (t) of the isotope is somtimes used in ____ calculations involving short-lived isotopes.
226 Ra, which is one of a number of isotopes along a "chain" of daughter products created when 238 U, found in ____, decays to 206 Pb over the course of ____ of years.
The intensity of a flux radiation is defined as the number of ____ in the beam per sq cm.
*note: this definition doesn't take into account the energy of the radiation in the beam, only the number photons present in the beam at a given instant per sq. cm.*
Photons will interact w/ the atoms of the material giving up their energy and being removed from the beam. This is called?
____ ____ describes the probability that each photon in the beam will ____ with the medium and ____ its energy, per cm of material that the photons pass through, and has units of cm-1.
- Linear attenuation
____ values must be defined by both energy and attenuating material.
____ beams produced by most modern radiation therapy equipment, which produce ____ beams, consist of a wide spectrum of photon energies.
____ is usally simply measured for a given machine and beam energy, and in low-energy x-ray units, ___ is used to describe the ____ of the beam.
HVL is an important quantity for photon beams and can be used as a description of "____ ____"
Photon beams can be classified as ___ or ___ beams, depending on their HVL.
A ____ ____ will ____ penetrate adequately through the patient to the film, but will instead leave a large amount of dose inside the patient w/o contributing any quality to the final film.
Low-energy x-ray units (diagnostic and superficial therapy) usually have a certain amount of "____ ____"
____ ____ is very important in the design and use of diagnostic and radiation therapy equipment.
In Rayleigh (____) scattering the incident photon is of very low energy, not energetic enough to ____the atom.
The interaction is called coherent because the ____ and energy of the emitted photon are ____ to those of the incident photon, a condition known in physics as ____.
The energy lost by these outer shell electrons usually appears as low-energy x-rays, called ____ ____?
Most radiation therapy energies fall into the range of ____ to ____ MeV, where ____ predominates.
The interaction of charged particles w/ the nuclei can lead to their radiative energy loss through a process called?
____ production is more likely in high Z materials such as ____ or ____than in low materials such as ____ or ____.
- lead tungsten
- water tissue
Bremsstrahlung (German for "____ ____") is the ____ important method of producing x-ray beams in theapy units.
There is a possibility that the characteristic x-ray photon may be absorbed by an orbital electron rather than leaving the atom. The electron now having excess energy, will be ejected from the atom in place of the photon. An electron that leaves the atom in this manner is called ____ ____ and is capable of causing biologic damage on its own.
____ ____ is the MOST common photon interaction that occurs in the energy range used in radiation therapy.
Compton (incoherent) scattering
In a ____ interaction, the ____ photon interacts with an outer shell electron, that is an electron very ____ bound to the atom (sometimes called a ____ electron bc the binding energy of the electron is much less than the incident photon).
When the photon is scattered from its incident path and has different energy and wavelength than the incident photon, the interaction is known as ____ ____.
The ____ electon, also known as ____ electron, and the scattered photon travel away from the atom at ____ angles.
In a ____ ____ the incident photon interacts with an electron in the ____ shells of the atom.. usually the ____ or ____ .. leading to transfer of all the energy of the photon to the ____.
- photoelectric interaction
- K L
____ ____ interactions occur at ____ energies; in fact, they are physically ____ when the energy of the incident photon is less than ____MeV.
- Pair production
In the pair production interaction the incident photon passes ____ to the nucleus of the atom.
When the photon interacts with the ____ field of the nucleus, it is ____, and instantly the energy is ____ as an ____-____ pair.
The rest energy of an electon or positron is ____MeV according to Einstein.
Electron-positron pair production can also occur under the influence of the ____ field of the electrons in the target material and is called ____ ____.
A ____ reaction is one in which the photon ____ the nucleus of the target atom ____ and is absorbed.
When a ____ ____ interacts with a medium, __ single type of photon interaction occurs; instead, the result is usually a ____ of two or more of the previous interactions.
- radiation beam
The total kinetic energy, may or may not remain the ____ before and after the ____. If NO kinetic energy of the system is lost in the collision, the collision is ____; if kinetic energy is lost from the system, the collision is ____.
The target electron in the atomic orbit may be "____ ____" to a shell ____ from the nucleus (____) or may be ejected completely from the atom (____) if the energy gained from the incident electron is high enough for the process to occur.
- kicked up
"____" between two particles does not necessarily mean that actual physical contact has occured.
In energies in the range usually used in radiation therapy (____ to ____MeV) the electrons interact mainly by ____-____ scattering or inelastic ____ scattering.
- 4 25
When the electron beam is in the lower energy range, (____ to ____keV), the photons are emitted in a ____ range of angles. As the electron beam energy increases, the photons tend to be emitted ____ to the direction of the incident electron; a phenomenon known as ____ ____ of the photon beam.
- 50 to 300
- forward peaking
Heavy charged particle interactions
Protons, alpha particles (helium nucleus w/ two protons and two neutrons), and heavier charged particles such as carbon-12 ions lose their energy by ____ ____ w/ atomic electrons and nuclei.
____ electrons on outer shell.
-Coherent scattering ____ ____.
-Incoherent scattering (Compton) has ____ ____.
-Photoelectric scattering is ____.
-Pair production is ____.
- bounces off
- free electrons
Braggs Peak vs Dmax
- -Braggs peak: hits then drops off, less risk (proton)
- -Dmax: attenuation (photon)
Cobalt-60 decays by __-__decay to an excited state of 60____.
X-ray quality vs quantitiy?
-Quality: is done with HVL which filters the beam so it only produces a hard beam which passes further through a medium.
-Quantity:intensity of flux of a rad beam is defined and the NUMBER of photons in the beam per sq. cm
Example of a soft x-ray?
Name 2 interactions for gamma rays?
- Compton scattering
- pair production
____ scattering cannot ionize the atom.
- Rayleigh (coherent)
- Thomson (coherent)
5 types of photon interactions?
- Thomson (coherent) scattering
- Compton (incoherent) scattering
- Photoelectric scattering
- Pair production
Positron has the symbol ____?
There are ____ strict rules for determining the hardness or softness of a radiation beam, a hard beam will have a higher ____ and higher ____ ability than a soft beam.