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Terms in this set (43)
Which is used more commonly in the modern linac, Klystron or magnetron?
Penumbra ______ with source site, depth and SSD, and _______ with SDD.
After the Bragg peak, dose rate
What type of radiation results from the decay of Cobalt-60?
what are the two mechanisms by which x-rays are produced, and which type is useful in the clinical setting?
bremsstrahlung and characteristic; bremsstrahlung
what unique feature is exhibited by protons and heavier charged particles, and what process accentuates this feature for negative pions?
Bragg peak, star formation
What does it mean for a carbon atom to be in an excited state during gamma emission?
A carbon atom is in an excited state due to the total energy of electrons being lowered by transferring one or more electrons to different electron orbitals.
What is the fundamental law of attenuation?
Equal thicknesses of absorber transmit equal fractions (percentages). This means that a material that attenuates 20% of the beam, 80% of the beam will remain. Then if it passes through the same thickness, 80% of the previous will be left. Ex: 100% --> 80% --> 64% --> 51%
What are the two types of equilibrium and how do they differ?
Secular and Transient equilibrium. Secular equilibrium is when the half-life of the parent is much greater than the half-life of the daughter. For instance, after 10 half-lives of the daughter, the amount of decay by the parent is negligible. The other type of equilibrium is transient equilibrium which is where the half-life of the parent is approximately 10 times greater than the half-life of the daughter. The decay of the parent has a steady and gradual decline. The activity of the daughter increases greatly, bottoms off, and steadily declines at the same rate of the parent.
This occurs when enough energy is given to the electron to remove it completely from the atom.
Which of the following is struck with electrons and goes through thermionic emission to produce X-Rays in an X-Ray tube?
In modern LINACS, what is the insert called that helps produce more homogeneous photon beam energy levels by hardening the beam?
Beam flattening filter
The size of the hole of the collimator determines?
The ultimate size of the beam
What is Inverse Square Law?
The formula used to identify the strength (intensity) of the x-ray beam at a given distance from the target
The beam's intensity is reduced by two effects?
beam divergence & beam attenuation
Grenz Therapy utilizes x-ray potentials less than?
Explain how we find the Average life of radioactive material and describe where the constant is derived from.
1.44x half life. 1.44 is 1/.639
Which type of parent-daughter equilibrium occurs when the half life of the parent is many times greater than that of the daughter.
A narrow _______ is the reason photons are an ideal treatment for pediatric patients.
What is an alpha particle?
When were X-rays discovered?
What energy range is used with orthovoltage?
Target material has a [high or low] atomic number.
The x-ray beam intensity decreases from cathode to anode direction. This variation in intensity is called the _____________.
Magnetrons generate [high or low] frequency power
True or false: During beta decay, the daughter nucleus has the same number of nucleons as the parent, but the atomic number is one less.
Penumbra increases with what three things and decreases with what one thing?
Penumbra increases with source size, depth, and SSD. Penumbra decreases with SDD
What process can occur where an electron in a lower shell can be excited to a higher shell level in an atom?
Isotopes are chemical elements consisting of the same number of protons but differing number of (?) consequently giving the element a different (? ).
As an electromagnetic wavelength Increases in a waveguide, what happens to the frequency of it's waves?
Every decay can create (?) particles.
Name the two main reasons nuclear decay takes place.
unstable n:p (neutron to proton) ratio, or the atom is in an excited state and must transform themselves to a more stable condition.
The difference between gamma rays and x-rays is
X-rays are generated in a mechanical object (cathode, anode, and target system)
Gamma rays are generated through natural radioactive decay
Characteristics of Co-60
5mm Dmax, first treatment method to have a build-up region, 1.25 MeV energy, an excited isotope of Co-59
Atomic radiation is when an electron is in an "excited state" and spontaneously _____.
decays to a lower-energy stable state
True or false: Collimation changes the energy and number of x-rays in the x-ray beam that reach the film.
False; collimation just limits the size and shape of the beam.
What is the advantage of orthotherapy compared to others, such as superficial therapy?
the SSD of treatment has increased (50cm)
What makes isotopes different from its original element?
the # of Neutrons
How is Cobalt-60 generated?
Extra neutrons are introduced to the atoms of the source material in a nuclear reactor
In the heart of an x-ray machine there is a ____1_____ charged cathode which is comprised of a ________2 _________ and a ____3_____ charged anode which is a flat disc made of ____4____.
1. Negatively 2. Heated Filament 3. Positively 4.Tungsten
charge of the anode
charge of the cathode