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What is the maximum number of electrons in the outer shell?
8
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An incident photon hits the electron in the outer shell and knocks it out ( e-)
Compton Scattering
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What is the most common interaction ?
Compton or incoherent Scattering
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What are the 5 types of interactions?
- 1.Coherent scattering
- 2.Photoelectric scattering
- 3.Compton Scattering (incoherent)
- 4.Pair Production
- 5.Photodisintegration
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Who are the scientists responsible for the work performed relating to interactions of photons/
Thomson, Einstein, Compton,Rutherford
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Which interaction is not energetic enough to ionize the atom?
Coherent scattering
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In which interaction is the incident photon of low energy, coming into region close to atom and absorbed, reemitting a second photon of same energy as incident but headed in new direction ( no ionizrion takes place because energy is too low)
coherent scattering
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What energy does the incident photon have to have
1.022Mev
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During pair production, what happens to incident electron?
it gets absorbed by nucleus
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What happens in pair production after the incident photon is absorbed by nucleus?
- releases a positron (β+) and neutron(β-) each with the energy of
- .511 each
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Which interaction collides with the nucleus
photodisintegration
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An incident photon comes in and gets turned around and sent another way
Brehmsstralung
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What are the electrons on the outer shell called?
free electrons or valance electrons
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Which interaction hits an inner shell (K or L) and leaves a hole and knocks out the e-
Photoelectric
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What are the 5 types of Photon interactions?
- 1.Coherent scattering
- 2.Photoelectric scattering
- 3.Compton (coherent) scattering
- 4.Pair Production
- 5.Photodisintegration
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What is the inverse square law?
I2=I1(d1 / d2 )2
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What does the half value layer due to the intensity?
each layer halves the intensity
24⇾12⇾6⇾3⇾1.5⇾.75⇾.375
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EXAMPLE
X isotope has an intensity of 100 cGY.
It's hvl is 12mm lead
how many mm of lead will it take to get to 3%?
- 1 layer drops to 50% (12mm)
- 2 layers drops to 25%
- 3 layers drops to 12.5
- 4 layers drops to 6.25
- 5 layers drops to 3.12 %
5 layers x 12 mm = 60 mm lead to reach 3%
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Attentuation coefficient
.693/whatever coefficient you are using (see table page 291 table 14-4 will equal the half value layer
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What is HVL and what is it used for?
HVL is the amount of material used to reduce the radiation to half its initial value
Initially used to express the beam quality.. Hard or soft.
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What is the difference between a hard beam and a soft beam?
a hard beam will have a higher HVL and higher penetrating ability
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Which beam is unable to penetrate through patient to film but instead leaves a large amount of dose inside patient without contributing to the film
Soft Beam
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Which beam increases the skin dose to a patient?
soft beam
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What happen as a beam passes through lead?
the softer beams are absorbed by lead
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Name the effect of passing a beam through a lead attenuator to increase the the overall HVL of beam, and decreased the intensity of the beam
beam hardening
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What are the 3 physical characteristics of the EM wave?
- Frequency (nu)
- wavelength (lambda)
- velocity (v)
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What is point to point?
Wavelength λ lambda
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How many times something comes through
( nu ) frequency
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NOTE
label a EM energy field page 283
- velocity
- wavelength
- frequency
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what is braking radiation?
Bremsstrahlung
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What is the most important method of producing xray beams in therapy units?
Bremsstrahlung
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Which ELECTRON interaction has a high energy electron passing close to nucleus of target atom, strongly attracted by the charges in nucleus, it slows down, losing kinetic energy (emitted as as photon with energy equal to incident electron when it slowed)
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Energy that is caused by motion in space
Kinetic
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If NO kinetic energy is lost in the collsion, the collision is ___________
Elastic
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If kinetic energy IS lost from the system , the collision is__________
Inelastic
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Name the 3 electron interactions
- Electron- Electron interaction
- Elastic Electron-Nuclei Collisions
- Inelastic Electron-Nuclei Collision
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Name the interactions which emit a gamma ray
(more than one)
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These interactions cannot ionize the atoms
(more than one)
Pair Production and Photodisintegration
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How many seconds are in 4.44 hours?
- 4hr x 60min=240min x60sec= 14400 sec
- .44%x60min=26.4 min x 60 sec=1584 sec
14400sec+ 1584sec=15984sec
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Cobalt 60 decays by _____________
β- decay to an excited state of nickel
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What does Lambda represent (λ) ?
- exponential decay constant
- wavelength
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Excess energy , no longer needed to maintain stability, given off in the form of this type of xray
characteristic xray
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Compton (incoherent) scattering
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Compton (incoherent) scattering
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