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Physics
X-rays: Production and Properties`
29
Physics
Undergraduate 4
11/16/2009

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Cards

Term
Electromagnetic Radiation (EMR)
Definition
wavelike fluctuations of electric and magnetic fields set up in space by oscillating (vibrating) electrons.
Term
Mode of transportation of energy through space
Definition
waves
Term
Radiation made in the tube:
Definition

Bremsstrahlung

 

Characteristic

Term
Radiation made in the body:
Definition

Compton

PE

Pair production

Term
Bremsstrahlung
Definition

As electron speeds toward anode and moves around the cuve of the foce field around nucleus of atom, energy is released by the "braking" of the electron

 

polyenergetic

Term
Energy of the photon in a Bremsstrahlung reaction depends on:
Definition
  • proximity to nucleus
  • energy of electron (from current)
  • charge of nucleus (Tungsten)
Term
Characteristic Radiation Production
Definition
  • electron interacts with innershell electron
  • must have equal to or greater energy than innershell electron
  • must have at least 70 kV to knock out k-shell
  • once knocked out, cascading effect occurs, releasing energy
Term
electron volt (eV)
Definition
the energy acquired by an electron when it is accelerated through a potential difference of 1 volt
Term
keV
Definition
unit of measurement for energy
Term
keV ends up being ______ of kVp applied to it.
Definition
1/3-1/2
Term
Primary radiation
Definition
radiation produced in x-ray tube that passes from tube to patient
Term
Properties of x-rays
Definition
  • highly penetrating
  • electrically neutral
  • polyenergetic
  • leave x-ray tube in straight lines
  • travel at speed of light
  • capable of ionization
  • can't be focused by lens
  • affect film (emulsion)
  • produces chemical or biological changes in boy due to ionization
  • produce scatter
Term
Main characteristics of x-ray beam and definition
Definition
  • quantity: amount of photons (#)--measured in Roentgens
  • quality: overall energy of beam
  • intensity: involves energy of photon plus number of photons
Term
exposure rate
Definition

Roentgens/sec

 

or

 

Roentgens/min

Term
Standard free-air ionization chamber
Definition

method used to determine quantity of beam

 

(measures ions in chamber)

Term
Roentgen
Definition

unit that measures quantity of radiation

 

(counts ion pairs being made)

Term
RAD (Gray)
Definition

Radiation Absorbed Dose: amount of energy that ionizes per gram of tissue or matter

 

100 rad= 1 Gray

Term
REM (Sievert)
Definition

Radiation equivalent in man that the employee receives

 

1 mSv=100 mrem

Term
Inverse Square Law
Definition
I1/D1=(D2/D1)squared
Term
HVL
Definition
Half Value Layer: the thickness of absorbing material necessary to reduce the x-ray quality to half its original value
Term
What are the purposes of filters?
Definition

harden beam to make more monoenergetic

 

reduce exposure to patient

Term
Remnant Radiation
Definition

photon passes through the body unaffected

 

(high energy=high kV)

no interaction with matter

reaches film

Term
Scattered Radiation
Definition
photon changes direction
Term
Photoelectric Effect (P.E.)
Definition
Totally absorbed
Term
Secondary Radiation
Definition
Compton interaction
Term
Attenuation
Definition
reduction of intensity of the beam as it passes through a medium
Term
What weakens the beam?
Definition
  1. absorption
  2. compton (scatter)
  3. inverse square law--how far the source is from the beam
Term
Absorption
Definition
photon gives up all its energy and disappears
Term
Photoelectric Effect
Definition
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