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Chapter 5 Electromagnetic Radiation

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Title: Chapter 5 Electromagnetic Radiation


1
Chapter 5 Electromagnetic Radiation
  • A photon is the smallest element of
    electromagnetic energy.
  • Photons are energy disturbances moving through
    space at the speed of light.
  • Photons have no mass but they do have electric
    and magnetic fields.

2
Electromagnetic Radiation
  • A field is an interaction between different
    energies, forces or masses that can not be seen
    but can be described mathematically.
  • Electromagnetic Radiation can be represented by
    the sine-wave model.
  • Sine-waves have amplitude.Amplitude is one half
    the range from crest to valley over a sine wave.

3
Electromagnetic Radiation
  • The important properties of the sine-wave model
    are frequency(f) and wavelength(?) and velocity.
  • Frequency is the number of wavelengths passing a
    point per second.
  • Frequency is identified as oscillations per
    second and measured in hertz (Hz).

4
Electromagnetic Radiation
  • Wavelength is the distance from one crest to
    another or from any point in the wave to the next
    corresponding point.
  • The wave parameters are very important. A change
    in one affects the value of one or both of the
    others.

5
Electromagnetic Radiation
  • At a given velocity, wavelength and frequency are
    inversely proportional.
  • The Wave Formula
  • Velocity Frequency x Wavelength

6
Electromagnetic Radiation
  • With EMF we know the velocity so the formula is
    simplified.
  • c f? or f c/? or ? c/f
  • As frequency increases, wavelength decreases and
    vice versa
  • For electromagnetic radiation, frequency and
    wavelength are inversely proportional.

7
Electromagnetic Spectrum
  • The electromagnetic spectrum includes the entire
    range of electromagnetic radiation.
  • The frequency range is from about 102 to 1024 Hz
  • Photon wavelengths range from 107 to 10-16m.
  • Grouped together, these radiations make up the
    electromagnetic spectrum.

8
Electromagnetic Spectrum
  • Three important ranges.
  • Visible light
  • Radio frequency
  • X-radiation
  • Others include
  • UV
  • IR and microwave

9
Electromagnetic Spectrum
  • EMF can be measured in three formats
  • Energy (eV) used to describe x-rays
  • Frequency (Hz)
  • Wavelength (m)

10
Visible Light
  • Measured in wavelength.
  • A prism is used to refract or change the
    direction of the photons.
  • Only form of EMF that we can sense.

11
Forms of Light
  • Visible light ranges from 700nm to 400nm
    wavelength.
  • Infrared light have longer wavelength than
    visible light but shorter than microwaves.
  • Ultraviolet light is located between visible
    light and ionizing radiation.

12
Radiofrequency
  • AM radio, FM radio and Television are other forms
    of electromagnetic radiation.
  • With radio, the frequency is used to identify the
    station.
  • Short wavelength radiofrequency are referred to
    as microwaves.

13
Ionizing Radiation
  • Unlike visible light or radiofrequency, ionizing
    electromagnetic radiation is characterized by the
    energy contained in the photon.
  • When we use 70 kVp, the photon will have energy
    varying from 0 to 70 keV.

14
Ionizing Radiation
  • The frequency is much higher and wavelength much
    shorter for x-rays compared to any other form of
    electromagnetic radiation.
  • Visible light identified by wavelength
  • Radiofrequency identified by frequency
  • X-rays identified by energy

15
Ionizing Radiation
  • The only difference between X-rays and gamma rays
    is their origin.
  • X-rays are produced outside the nucleus.
  • Gamma rays are produced inside the nucleus of
    radioactive atoms.

16
Wave-Particle Duality
  • A x-radiation photon and a visible light photon
    are fundamentally the same except that
    x-radiation photons have a much higher frequency
    and shorter wavelength.
  • These differences change the way they interact
    with matter.
  • Visible light tends to behave as waves.

17
Wave-Particle Duality
  • X-radiation tends to behave more as particles
    than waves.
  • Both types of photons exhibit both types of
    behavior and this is referred to as the
    wave-particle duality of radiation.
  • Photons interact with matter when the matter is
    approximately the same size as the photon
    wavelength.

18
Wave-Particle Duality
  • Radio television photons wavelength is measured
    in meters and interact with long metal rods
    called antennae.
  • Microwave are measured in centimeters and react
    most easily with popcorn hotdogs.

19
Wave-Particle Duality
  • Visible light wavelength is measured in
    micrometers or nanometers, interacts with living
    cells such as the rods and cones in the eye.
  • Ultraviolet light interacts with molecules.
  • X-rays interact with atoms and electrons.
  • All radiation with wavelengths longer than x-rays
    interact primarily as a wave.

20
Wave model Visible Light
  • Vision is result of specially developed organ
    that sense a very narrow portion of the
    electromagnetic spectrum.
  • When a visible light photon strikes an object, it
    sets the molecule of the object into vibration.

21
Wave model Visible Light
  • The orbital electrons become excited by the
    higher energy. This energy is immediately
    irradiated as another photon of light. This is
    referred to as reflection.
  • Atomic and molecular structure determine which
    wavelength of light are reflected.

22
Wave model Visible Light
  • Light photons not reflected are either absorbed
    or transmitted.
  • There are three degrees of absorption
  • Transparency
  • Translucency
  • Opacity

23
Degrees of Absorption
  • If all of the light is transmitted almost
    unaltered, it is transparent.
  • If only some of the light passes through , it is
    called translucent.

24
Degrees of Absorption
  • If all of the light is absorbed, it is called
    opaque.
  • Attenuation is the sum of scattering and and
    absorption of radiation.

25
Radiopaque or Radiolucent
  • Terms used to describe the appearance of objects
    on the x-ray film.
  • Objects that absorb the radiation are called
    radiopaque.

26
Radiopaque or Radiolucent
  • Structures that attenuate the x-rays are referred
    to as Radiolucent.
  • Bone is radiopaque.
  • Lung is radiolucent.

27
Inverse Square Law
  • I1 D22
  • ____ _____
  • I2 D12
  • Radiation intensity is inversely related to the
    square of the distance from the source.
  • The decrease is due to the light being spread
    over a ever increasing area.

28
Inverse Square Law
  • If the source is not a point but a line such as a
    fluorescent lamp, the inverse square law does not
    hold at distances close to the source.
  • The inverse square law can be applied to
    distances greater than seven times the longest
    dimension of the source .

29
Inverse Square Law
  • The Inverse Square Law is used in radiography to
    adjust technical factors for changes in distance.
  • It is also used for radiation protection. The
    farther you are away from the source, the lower
    the exposure.
  • To use the formula, you need to know three of the
    4 factors which are two distances and two
    intensities.

30
Particle Model Quantum Theory
  • Unlike other forms of electromagnetic radiation,
    x-ray energy is measured in electron volts (eV).
  • X-ray energies range from 1 to 50 MeV
  • X-ray wavelengths range from 10-9 to 10-12m.
  • X-ray frequency range from 1018 to 1021Hz

31
Range of X-ray Energies
  • Diffraction uses less than 10 kVp.
  • Grenz rays with energies of 10 to 20 kVp are used
    in dermatology.
  • Diagnostic Radiography uses the range of 30 kVp
    to 150 kVp.
  • Therapy uses energies from 200 to 1000 kVp

32
X-ray Waveform
  • X-rays have both electric and magnetic fields.
  • One wave represents the electric field and one
    the magnetic field varying at right angles to
    each other.

33
Plancks Quantum Theory
  • X-rays are created at the speed of light or they
    dont exist at all.
  • The energy of a photon is directly proportional
    to its frequency.
  • A photons energy is inversely proportional to
    the photon wavelength.
  • E hf where E is the photon energy h is
    Plancks constant or 10-15eVs or 6.63 x 10-34Js
    and f is the photon frequency in hertz.

34
Matter and Energy
  • Like the law of the conservation of matter, the
    law of conservation of energy states that Energy
    can be neither created or destroyed.
  • Plancks quantum physics and Einsteins physics
    of relativity greatly extended these theories.

35
Matter and Energy
  • According to quantum physics and physics of
    relativity, matter can be transformed into energy
    and vise versa.
  • Although matter and energy are interchangeable,
    it is energy from the x-ray photon interacting
    with tissue and the image receptor that forms the
    basis of x-ray imaging.

36
Mass Energy Relationship
  • Mass and energy are two forms of the same medium.
    This scale shows the equivalence of mass measured
    in kilograms to energy measured in electron volts.

37
Summary
  • X-rays are just one type of photon of
    electromagnetic radiation
  • The following are used to describe the
    electromagnetic spectrum.
  • Frequency
  • Wavelength
  • Velocity
  • Amplitude
  • These factors are what determines such radiation
    interacts with matter.

38
History of Chiropractic Radiography
39
X-Ray and Chiropractic
  • First used by B.J. Palmer at PSC in 1910.
  • He referred x-rays of the spine as spinographs.
  • Originally take to prove existence of the
    subluxations later used to evaluate spine for
    misalignment and pathology..

40
X-Ray and Chiropractic
  • 1924 first erect spinal radiographs at Universal
    Chiropractic College in Pittsburgh, Pa. This was
    the first time that the effects of gravity on the
    spine was evaluated.
  • Until 1938 all films taken at P.S.C. by Doctor
    Ray Richardson.

41
X-Ray and Chiropractic
  • Dr Warren Sausser was a 1917 graduate of Palmer
    School of Chiropractic.
  • He was a radiologic technologist in the Army
    during WW1.
  • He is one of the pioneers of radiography. Thanks
    to him Chiropractors were allowed to take x-rays.

42
X-Ray and Chiropractic
  • He is responsible for D.C.s in New York being
    able to take x-rays.
  • He founded what is now the Chiropractic College
    of Radiology.

43
X-Ray and Chiropractic
  • He was the first chiropractor to take full body
    radiographs.
  • He also did extensive research in full spine
    radiography.

44
X-Ray and Chiropractic
  • Dr Hugh Logan stressed the importance of upright
    full spine films making the procedure popular.
    Dr. Sausser was impressed by his approach.
  • Dr Warren Sausser reported the first single
    exposure full spine taken with the 14 x 36
    film. Standard X-ray Company designed the x-ray
    machine . Kodak developed cassette, film and the
    special hangers needed to process the film. The
    cassette weighed 50 pounds.

45
X-Ray and Chiropractic
  • Dr. Sausser developed filters to equalize the
    exposure.
  • The tube was placed nine feet from the patient
    and a 12 second exposure was needed to produce
    the image.
  • Dr. Sausser also developed full body exams but
    only the full spine remains today.
  • The full body radiograph went the way of the
    x-rays to fit shoes.

46
X-Ray and Chiropractic
  • Like many of the early pioneers of x-ray, he died
    in 1958 as a result of the affects of radiation
    exposure.
  • He had tumors down his side that was not behind a
    barrier during the exposures.
  • He would often peek around the barrier to check
    on the patient.

47
X-Ray and Chiropractic
  • Films taken recumbent until 1938 at Palmer School
    of Chiropractic.
  • All forms of radiography was done at P.S.C.
    including fluoroscopic contrast studies of G.I.
    Tract and gallbladder until 1938.

48
X-Ray and Chiropractic
  • The use of radiography started as a means to see
    the subluxations. Today it is used to image the
    entire body and not just the spine.
  • Today the scope is generally limited to plain
    film radiography of the spine, chest, abdomen and
    extremities.

49
X-Ray and Chiropractic
  • As early as 1922, they used x-rays for the
    detection of pathological processes, fractures
    and anomalies that impact the patients health as
    well as chiropractors determinations of what to
    do or not to do.
  • This is still true today.

50
End of Lecture
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