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RTEC 111

RTEC 111. Bushong Ch 2 & 3 Technique Math. Fundamentals of Radiologic Science. RTEC 111 Bushong Ch. 2. Units of Measurement. This allows scientists to describe quantities. The fundamental units of measurement are mass, length and time. Two widely used systems of measurement.

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RTEC 111

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  1. RTEC 111 Bushong Ch 2 & 3 Technique Math

  2. Fundamentals ofRadiologic Science RTEC 111 Bushong Ch. 2

  3. Units of Measurement • This allows scientists to describe quantities. • The fundamental units of measurement are mass, length and time. • Two widely used systems of measurement

  4. UNITS OF RADIATION MEASUREMENT • TO QUANTIFY THE AMOUNT OF RADIATION A PATIENT OR WORKER RECEIVES.

  5. Conventional (British)Units vs. SI Units • Conventional (British) Units Used Since The 1920’s (foot, pound, second) • also called the US customary system • 1948 - A System Of Units Based On Metric Measurements Was Developed By The International Committee For Weights And Measures. SI Units

  6. Commonly Used SI Prefixes

  7. Commonly Used SI PrefixesBushong Pg. 34

  8. Important Radiology Units • Roentgen (R) is coulomb per kilogram (C/kg) • Radiation absorbed dose (rad) is gray (Gy) • Radiation equivalent man (rem) is seivert (Sv)

  9. RADS REMS R - ROENTGEN GRAYS SIEVERT C/KG Conv. Units SI Units

  10. ROENTGEN (R) • SI = coulomb per kilogram (C/kg) or air kerma Gya • THE QUANTITY OF X-RADIATION • ONLY EXPOSURE IN AIR • OUTPUT OF XRAY TUBE • DOES NOT INDICATE ACTUAL • PATIENT EXPOSURE OR ABSORBTION

  11. RADIATION ABSORBED DOSE (RAD) SI = GRAY (Gy) • MEASURES THE AMOUNT OF ENERGY ABSORBED IN ANY MEDIUM. (the patient) • 1 Gy = 100 rads • 1/100 or 0.01 Gy = 1 rad • 1 centigray = 1 rad

  12. REM / SIEVERT • 1 Sv = 100 rem • 1/100 Sv = 1 rem • 1 centisievert = 1 rem • Used for occupational exposure EMPLOYEE EXPOSURE

  13. RADIATION EQUIVALENT MAN(rem) OR Effective dose • SI UNITS = SEIVERT • NOT ALL TYPES OF RADIATION PRODUCE THE SAME RESPONES IN LIVING TISSUE • THE UNIT OF DOSE EQUIVALENCE, EXPRESSED AS THE PRODUCT OF THE ABSORBED DOSE IN RAD AND QUALITY FACTOR.

  14. rem OR Sievert • SI UNITS = SIEVERT • 1 Sv = 100 rem • THE PRODUCT OF THE GRAY AND THE QUALITY FACTOR.

  15. Rad VS. Rem • RAD’S X QUALITY FACTOR = REM • GRAY’S X QUALITY FACTOR = SIEVERT • QUALITY FACTOR FOR X-RAYS = 1 • So…… Rads = Rems

  16. Rems & Rads • Sieverts & Grays • PAtient = rAds & grAys • Employee (technologists) = rEms & siEvErts

  17. milli m 10-3 5 mrem = 0.005 rem 5000 mrem = 5 rems 500 mrem = 0.5 rems 50 mrem = 0.05 rems 5 mrem = 0.005 rems Metric System

  18. Radiology – units of measurement • What units correlate with: • Exposure • Dose • Effective dose

  19. 3 rem = ? Sv 30 mrem = ? Sv 300mSv = ? mrem 8 rad = ? Gy 25 mrad = ? Gy 750 Gy = ? mrad Unit conversion

  20. The Structure of Matter RTEC 111 Bushong Ch. 3

  21. Radiology Mechanics • Velocity • The motion of an object can be described by the use of two terms velocity and acceleration. • Velocity = speed • What is the speed of x-rays in a vacuum?

  22. Kinetic energy (KE) • The energy associated with the motion of an object • Kinetic energy depends on the mass of the object and the square of its velocity

  23. Potential energy (PE) • The stored energy of position or configuration

  24. Heat • Is the kinetic energy of the random motion of molecules

  25. Atoms • Elements: 112 substances have been identified • 92 are naturally occurring and 20 more have been artificially produced • The atom is the smallest particle of matter that has the properties of an element

  26. What does Z # mean? Atomic mass? Atomic Structure

  27. Combining atoms • Atom + Atom = molecule • Molecule + Molecule = Compound • The smallest particle of an element is an atom; the smallest particle of a compound is a molecule

  28. Elements • Chemical elements – determined by the # of protons • Isotopes – neutrons, atomic mass • Shells – electron orbits • Ion or Ionization?

  29. e- shell configuration is dependent on the size of the atom

  30. Ionization of carbon • Ion pair • 34 eV of energy is required

  31. Electron Arrangement • The maximum number of e- that can exist in each shell increase with distance from the nucleus • See table 3-2, pg. 43 • No outer shell can contain more than eight e-

  32. Periodic table of the elements • The table is organized by the number of e- in the outer or valence shell of an atom • # of e- in the outermost shell = the period of that atom on the table • The valence shell is important because it determines how that element will react and interact with other elements

  33. Electrons • Can exist only in certain shells • Each shell has different electron binding energies or energy levels

  34. Electron binding energy • The closer the e- is to the nucleus the more tightly it is bound and the higher the binding energy • Also the larger the Z# of the atom the higher the binding energy for any given shell….therefore more difficult of ionize larger atoms

  35. Ionization potential • The energy required to ionize tissue atoms • How much energy is required to ionize tungsten’s K shell? • Pg 46

  36. Types of Ionizing Radiation • All ionizing radiation can be classified into two categories • Particulate or electromagnetic radiation • What type of radiation is used for diagnostic ultrasound or magnetic resonance imaging? Ionizing or Nonionizing?

  37. ParticulateRadiation • The emission of particles and energy from the nucleus in order to become stable • Radioactive elements are called radionuclides or radioisotopes

  38. Radioisotopes • Occur when atoms have too many or too few neutrons • Can occur naturally or can be man made

  39. Radioisotope decay • Decay from the nucleus to become stable • Beta emission and Alpha emission • Alpha & Beta particles can cause ionization because of high kinetic energy • What form of energy does x-rays use to ionize

  40. Radioactive Half-Life • The time required for a quantity of radioactivity to be reduced to one-half its original value • For radiology: Half-value layer • To reduce the strength of the x-ray beam by 1/2

  41. Photons vs Particles • Particles cause ionization through kinetic energy • Photons have no mass, no charge, travel at the speed of light and are considered energy disturbances in space. A form of EM energy. Photons travel at the speed of light or not at all.

  42. X-rays vs Gamma rays • Forms of EM energy • Only difference between x-rays and gamma rays is their origin • Only difference between alpha and beta particles is their origin

  43. Origins • X-rays = outside the nucleus in the e- shells • Alpha & Beta particles = from the nucleus • Gamma rays = form the nucleus • As part of radioactive decay

  44. X-rays have low ionization rates and a very long range in tissue

  45. Technique Calculations

  46. What happens to primary? • When x-rays pass through a patient's body, three things can happen: (1) the x-ray photon is transmitted, passing through the body, interacting with the film, and producing a dark area on the film; (2) the x-ray photon is absorbed in an area of greater tissue density, producing lighter areas on the film; and (3) the x-ray photon is scattered and reaches the film causing an overall gray fog.

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