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(λ) 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= fλ or f= c/λ or λ= 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. Planck’s Quantum Theory • X-rays are created at the speed of light or they don’t exist at all. • The energy of a photon is directly proportional to it’s frequency. • A photon’s energy is inversely proportional to the photon wavelength. • E= hf where E is the photon energy; h is Planck’s 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. • Planck’s quantum physics and Einstein’s 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.

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