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Radiology Exam 1
Lecture 1 (Radiation Physics)
31
Other
Not Applicable
06/09/2008

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Term
Roentgen
Definition
- discovered x-radiation
- 1st nobel prize in physics
Term
radiation
Definition
- transfer of light through space
Term
x-rays
Definition
- form of electromagnetic radiation
Term
EM Radiation
Definition
- oscillating electric and magnetic fields moving through space at right angles to each other
- radio, micro, infared, ultraviolet, gamma
Term
Speed of Light
Definition
Velocity of EM radiation
Term
photon
Definition
- energy carried by radiation
- "light"
Term
wavelength
Definition
- distance btwn peaks in a wave
Term
Frequency
Definition
- number of waves hat pass a point in a unit of time
Term
high energy
Definition
- high frequency/short wavelength
Term
ionizing radiation
Definition
- radiation with enough energy to knock electrons off an atom
- x-rays, gamma rays, UV radiation
Term
X-rays
Definition
- no mass/charge
- very short wavelengths/ high frequencies
- can ionize atoms
Term
X-ray production
Definition
- tungsten filament heated, electrons move away from nuclei
- electrons drawn across x-ray tube at high speed (cathode --> anode)
- electrons collide w/target, converting kinetic energy into EM radiation
Term
thermionic emission
Definition
- boiling off electrons
Term
space charge
Definition
- boiled off electron cloud around filament
Term
kilovolts (kV)
Definition
Potential difference measure in...
Term
milliamperes (mA)
Definition
tube current measured in...
Term
focal spot
Definition
- electrons focused to point at anode by molybdenum focusing cup
- electrons slow/stop at target, converting kinetic energy --> EM
Term
seconds/impulses
Definition
- length of time electrons move across tube (exposure time) measured in...
Term
x-ray production time
Definition
- not produced continuously
- in discrete impulses
- 60/second
Term
K shell
Definition
- electron shell closest to nucleus
- greatest binding energy
Term
Binding energy
Definition
- holds electrons in orbit around nucleus
- greatest for K shell closest to nucleus
Term
Electrons interaction with Tungsten
Definition
- Brehmsstrahlung radiation
- Characteristic radiation
Term
Brehmsstrahlung radiation
Definition
- "brakes" "radiation" auf Deutsch
- electrons approach nucleus and slow down as they fling around it
- kinetic --> EM
Term
Brehmsstrahlung radiation
Definition
- 85-90% of x-rays produced through this
- wide range of energies because electrons slow at various rates depending on angle to nucleus
-
Term
characteristic radiation
Definition
- electron hits k shell electron and knows it out
- electron from l shell fills spot in k shell and creates energy
- energy = difference in binding energies = photons in x-ray range
- one energy level
- 10-15% x-rays
Term
characteristic radiation
Definition
- characteristic of element since binding energies differ in different elements
Term
monoenergetic
Definition
- one energy level
- characteristic radiation
Term
polenergetic
Definition
- multiple energy levels
- Brehmsstrahlung radiation
Term
x-ray darkness
Definition
- lighter w/less x-rays hitting target
Term
kVp
Definition
- voltage peak value
Term
Components of X-Ray Tube
Definition
- glass envelope
- electron stream
- tungsten filament
- cathode (-)
- anode (+)
- focusing cup
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