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RTA 2011 WK 5 FINAL

RTA 2011 WK 5 FINAL. Tube Exposure Factors Math Technique Contrast and Density. X-ray Properties. X-Ray Properties. Are highly penetrating, invisible rays which are a form of electromagnetic radiation.

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RTA 2011 WK 5 FINAL

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  1. RTA 2011WK 5FINAL Tube Exposure Factors Math Technique Contrast and Density

  2. X-ray Properties

  3. X-Ray Properties • Are highly penetrating, invisible rays which are a form of electromagnetic radiation. • Are electrically neutral and therefore not affected by either electric or magnetic fields

  4. X-Ray Properties • Can be produced over a wide variety of energies and wavelengths (polyenergetic & heterogeneous). • Release very small amounts of heat upon passing through matter.

  5. X-Ray Properties • Travel in straight lines. • Travel at the speed of light in a vacuum. • Can ionize matter.

  6. X-Ray Properties • Cause fluorescence of certain crystals. • Cannot be focused by a lens. • Affects photographic film.

  7. X-Ray Properties • Produce chemical and biological changes in matter through ionization and excitation. • Produce secondary and scatter radiation.

  8. Artistic Talent

  9. Artistic Talent

  10. Your artistic talent…..

  11. Your artistic talent…..Your signature

  12. What is Technique? • Exposure factors under the control of the radiographer at the control panel • mAs (mA x s) • Milliamperage • seconds • kVp

  13. How does it affect our image?

  14. The Control Console • Where tech sets technical factors A. _____ B. _____ C. ____________ • Only a ________________ individual is authorized to energize the console

  15. Control panelAKAControl Console

  16. Producing optimal radiographs

  17. PRIME FACTORS mAs kVp Distance (SID)

  18. DENSITY • DENSITY • THE AMOUNT OF _________“DARKNESS” ON THE RADIOGRAPH • Usually in response to_________________ • Described as a comparison of light going __ and light coming ____

  19. DENSITY • _________________ on a radiograph • or of a certain part of the image • Results from: • the _______of radiation that reaches a particular area of the ______________

  20. Anatomic Density vs. Optical Density • ________________ • Pathology or condition that _________ the atomic number of that body part • Will appear as a ___________ in optical density on the film • Optical density • The level of darkening we SEE on the film

  21. Inversely Proportional • Atomic number (z#) increases • _______________ • Atomic number (z#) decreases • _______________

  22. Variables that Affect Density • Patient size • Tissue composition • mAs • kVp • Source image receptor distance (SID) • Beam modification • Image receptor • Processing

  23. Variables that Affect Density • Patient size • Tissue composition • mAs • kVp • Source image receptor distance (SID) • Beam modification • Image receptor • Processing

  24. ______ is the PRIMARY controlling factor of density

  25. mAs • __________ • number of x-ray photons in the beam • Also called: • x-ray output • Intensity

  26. Milliamperage • mA • One milliampere is equal to one thousandth of an ampere. • The amount of current supplied to the x-ray tube • Range 10 to 1200 mA

  27. Time • In seconds • How long x-rays will be produced • 0.001 to 6 seconds

  28. mAs mA X s = mAs

  29. mAs Reciprocity • 100 mA x 1/4 = 25 mAs • 200 mA x 1/8 = 25 mAs • 400 mA x 1/16 = 25 mAs

  30. What changes to mAs are needed for human eye to detect?

  31. mAs DOUBLED = DENSITY DOUBLED

  32. DENSITY directly proportional to mAs 100 mAs + 25%mAS = 25% increase in density +50% mAs = 50% increase in density

  33. Math Problems

  34. CONTRAST • THE DIFFERENCES BETWEEN: • Blacks • Whites • Dark gray • Light gray

  35. Contrast • Comparison of all densities on image • _________________ • Gray tones from darkest to the lightest gray

  36. Short scale of Contrast • _________________ • _________________ • _________________ • _________________ • Greater distance between densities

  37. Long Scale of Contrast • ______________ • ______________ • ______________ • ______________M • Less distance between densities

  38. Kilovoltage Peak (kVp) • Is the _______________________ of contrast • _____________ ability of photons • Manipulates radiographic contrast • Strength or ______________ of photons • Maximum ___________ energy • Ranges from 0-peak • Heterogeneous or polyenergetic

  39. High kVp Penetrates more easily Causes more grays Low scale of contrast Low kVp Decreases penetration Causes more black-white High scale of contrast Beam Attenuation AKA absorption • Different parts of body attenuate differently • The difference in attenuation is the basis for contrast

  40. Optimal kVpIs there such a concept? • YES and NO • Depends on the body part • The anatomic area of interest • More energy is needed to penetrate through bony tissue (high z #) than soft tissue (low z #)

  41. 15% Rule • 15% kVp = doubling of exposure to the image receptor  15% kVp = halving of exposure to the image receptor 15% rule will always change the contrast of the image because kV is the primary method of changing image contrast. Remember : 15% change ( ) KVP has the same effect as doubling or ½ the MAS on density

  42. + 15% kvp - 15% kvp

  43. Three things can happen… When x-rays interact with patient: • (1) the x-ray photon is __________ • (2) the x-ray photon is __________ • (3) the x-ray photon is __________

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