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Developing A Technique Chart

Developing A Technique Chart. Chapters 9 & 10. Exposure Factors & Critiquing X-rays. mAs kVp. mAs. Milliamperage -seconds Number of electrons used to produce x-rays Density/darkness/exposure of a film Increase mAs = increased exposure Blacker films Decrease mAs = decreased exposure

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Developing A Technique Chart

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  1. Developing A Technique Chart Chapters 9 & 10

  2. Exposure Factors & Critiquing X-rays mAs kVp

  3. mAs • Milliamperage-seconds • Number of electrons used to produce x-rays • Density/darkness/exposure of a film • Increase mAs = increased exposure • Blacker films • Decrease mAs = decreased exposure • Lighter/whiter films

  4. kVp • Peak kilovoltage • Speed of electrons used to produce x-rays • Exposure AND contrast of a film • Hint: when changing kVp, do so at 4-6 kVp increments • Changes exposure without changing contrast much

  5. Definitions • Density/darkness/exposure • The amount of darkness on a film • Focus is one body part • Contrast • Comparing the various densities on a film • Focus is all of the body parts • Increased contrast = lost of black & white with very little shades of gray • Decreased contrast = black, white, lots of shades of gray

  6. kVp Effects • Increased kVp= increased exposure, decreased contrast • Soft tissue films, especially thick abdomens • 70-125 kVp? • Decreased kVp= decreased exposure, increased contrast • Extremities (bones); small mammals/exotics • 40-60 kVp?

  7. Why A Technique Chart? • To develop a consistent method of taking EXCELLENTradiographs, with a minimum of retakes • Invaluable resource for RVT • Saves time & retakes • Saves owner money • What x-ray machine settings should we use? Let technique chart tell us

  8. Four Techniques to Develop a Technique Chart Doctor/RVT Memory X-ray Log Notebook Manufacturer Technique Chart Scientific Method

  9. Doctor/RVT Memory • Inconsistent • Least effective method of making “Diagnostic X-rays”

  10. X-ray Log Notebook • Recording of exposure factors, date, patient, etc. for every film  then using that data every time you take an x-ray • Good idea for technique chart for exotics • Inefficient technique chart for dogs & cats • Although good to do for log of ALL x-rays taken by practice

  11. Manufacturer Technique Chart • Supplied by Manufacturer • Developed by company with “Scientific Method” for their particular machine

  12. Formulated By Manufacturer

  13. Formulated by “Scientific Method” • KISS!!!  • I can make that chart in 6 x-rays!  • Grid technique versus table top • Any measurement exceeding 10 cm necessitates the use of a grid to reduce fog-producing scatter radiation • Standard mAs versus variable mAs • Manufacturer versus making your own

  14. Santes’ Rulepage 101 • Formula – (2 X tissue thickness in cm) + 40 inches + grid ratio = kVp • Add kVp for a grid

  15. Steps to Making Technique Chart mAs Chart 3 Abdominal X-rays of Average Dog Critique Films Scientifically Develop Chart

  16. mAs ChartTable 9-1, Page 101 • Shows every possible combination of mA and time  mAs possibilities on machine • Look for 5 mAs and 10 mAs, or as close as possible

  17. TABLE 9-1 MILLIAMPERAGE-SECONDS (MAS) CHART

  18. Technique Chart for Dogs (Grid Technique) • Select an “average dog” • Measure for a lateral of the abdomen • Use Santes’ Rule for kVp setting • Use maximum mA • Take and critique 3 x-rays…… • Scientifically develop the chart

  19. “Average Dog” • Select an “average dog” • Beagle?  • Measure for a lateral of the abdomen • 11-16 cm • Use Santes’ Rule for initial kVp setting • Example – abdomen = 12 cm • (2 X 12) + 40 + 8 (grid ratio = 8:1) = 72 kVp

  20. 3 Abdominal Films • Grid x-rays, 10 mAs (MAXIMUM mA) (300 mA at 1/30 second) • Film #1 = 66 kVp • Film # 2 = 72 kVp • Film #3 = 78 kVp • Critique all 3 films for exposure  select the BEST exposed film • Your chart is done!!!! 

  21. Finish the Chart for Dogs • Make a grid for 5 exposures • Abdomen first (width [cm], kVp) • Fill in the other 4 exposures • Thorax • Deep bone • Skull • Extremities

  22. 5 Rows in Technique Chart Extremities Deep Bone Skull Thorax Abdomen

  23. 20 Columns in Chart 1 column for each centimeter (cm)

  24. Scientifically Develop Chart • 1 cm = 2 kVp, until 80 kVp • After 80 kVp, 1 cm = 3 kVp • Fill in 1 box • Abdomen box for 12 cm = 72 kVp • Fill in rest of Abdomen row

  25. Fill in Rest of Chart • Skull Row = +4 kVp of abdomen numbers • Deep Bone Row = +4 kVp • Thorax Row = -10 kVp • Extremities Row = +2 kVp

  26. Technique Chart for Cats (Table Top Technique) • Select an “average cat” • Measure for a lateral of the abdomen • Use Santes’ Rule for kVp setting • Use maximum mA • Take and critique 3 x-rays…… • Scientifically develop the chart, just like the grid technique chart

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