VET-120 Diagnostic Imaging

1. VET-120Diagnostic Imaging

2. Course Set-up • 5 Lessons (Webinars) • 5 Lesson Exams • Final Proctored Exam • Required Reading • Diagnostic Imaging Study Guide • Radiography in Veterinary Technology (Lavin – 4th edition)

3. Studying for Exams • Make copy of Lesson PowerPoints • Take excellent notes during Webinars • Read & highlight Assigned Readings in Study Guide & Lavin book • Perform Self Checks in Study Guide • Learn the Glossaryat the beginning of each Chapter in Lavin book • Study Key Points & Review Questionsat end of each Chapter in Lavin book

4. Lesson 2– Producing a Radiographic Image

5. Glossary Terms – Page 36

6. The 4 Exposure Factors Milliamperage (mA) Time (S) Kilovoltage (kVp) Distance (SID)

7. The 4 Exposure Factors • Exposure factors are THE KEY to taking good quality diagnostic x-rays • Definition • Machine settings that a technician can adjust on the machine to take diagnostic x-rays • SIBKIS when it comes to changing exposure factors! 

8. Milliamperage (mA)Figure 4-1, Page 36 • Amount of electrons to produce x-rays • Fundamental – Use the highest mA your machine can do • Allows you to use much lower time settings • Less exposure time to x-rays • The higher the mA, the more exposed your film will be (the DARKER it will be) if all other exposure factors are kept the same

9. Exposure Time (S) • The longer the exposure time, the greater the number of x-rays produced • The longer the exposure time, the greater the exposure to scatter radiation • Inverse relationship to mA • Benefits of shorter exposure times • Less movement on x-ray (thoracic films) • Technician safety

10. Kilovoltage Peak (kVp)Figure 4-4, Page 38 • Speed of electrons used to create x-rays • Quality of x-ray • Not faster x-rays, but more penetrating • Affects both exposure (darkness) of film, and contrast of film • Santes’ Rule • (2 X thickness of body part) + 40 = kVp

11. CalipersFigure 4-5, Page 38 • Definition • A tool used to measure the thickness of a body part to be x-rayed • Use centimeters (cm), not inches • If in between numbers…… latitude

13. Latitude

14. Kilovoltage Summary • It affects both contrast and exposure • Increased kVp  more penetrating x-rays • Increased kVp  increased scatter radiation • Increased kVp  decreased contrast (leading to more latitude)

15. Milliamperage and Time • Milliamperes • Exposure time • Formula • mAs = mA X s • Examples – same mAs, different mA • Same darkness(exposure)

16. Distance (SID) • Source-image distance(SID) • Aka Focal-film distance(FFD) • Should be 40 inches for both table top technique and grid technique • Inverse Square Law – • Figure 4-6, Page 39 • Definition • KISS Fundamental – distance should always stay constant if possible

17. Greater Distance = Less Shadows

18. Greater Distance = Less Intensity (Exposure)Figure 4-6, Page 39

19. Review of X-ray Production • Figure 4-7on page 40 • X-ray tube parts • Primary vs. secondary radiation • Exposure factors

20. Radiographic Quality

21. Glossary Terms – Page 44

22. Radiographic Quality • Definition • How easily details can be seen on an x-ray • How sharp the details are

23. Radiographic Quality Factors Radiographic Density Radiographic Contrast Exposure Factors Scatter Radiation Grids

24. Radiographic Density • Definition – amount of darkness (exposure) in x-ray film • When looking at a film for exposure, look at the body part you are interested in • What causes density, you ask?  ---

25. Densities of Various Structures Subject densities: 1, Air. 2, Fat. 3, Water. 4, Bone. 5, Metal. Air is least dense, allowing x-rays to penetrate and expose the film. Metal is the most dense, absorbing most of the x-rays and allowing only a few to penetrate, exposing the film.

27. Factors Affecting Radiographic Density • All 4 exposure factors • Figure 5-2 on page 46 • Same mAs (exposure), different thickness of body part • White structures on x-rays • Radio-opaque….. Why? • Black structures on x-rays • Radio-translucent….. Why?

28. Density on X-raysFigure 5-3, Page 47

29. Subject Density/Exposure

32. How is the Exposure on This X-ray? • “Overexposed” (Figure 5-7 on page 49) • Body parts too dark • Why? • “Under-exposed” (Figure 5-6 on page 48) • Body parts too light • More common than overexposed • Correct exposure (“just right”!)

33. Overexposed Film (Too Dark)

34. Underexposed Film(Too Light)

35. “Just Right, Goldilocks!” 

36. Underexposed or Overexposed?

37. Underexposed or Overexposed?

38. Underexposed or Overexposed?

39. Radiographic Contrast • Definition • The density differences between 2 adjacent areas of an x-ray • High contrast (short scale) • Low contrast (long scale) • Just like exposure, look at body parts (not background) on film

40. High Contrast vs. Low Contrast Table 5-1, Page 46

41. High Contrast X-rays • Lots of black and white on the film with very little shades of gray • Bone x-rays should be high contrast

46. Low Contrast X-rays • The film has black, white, and lots of shades of gray in between • Usually soft tissue x-rays • Latitude

50. Factors Affecting Radiographic Contrast • kVp • Relationship of contrast and kVp (Table 5-1 on page 46)*** • Latitude • Subject contrast • Difference in density between 2 body parts • Depends on thickness & density of part (Table 5-2 on page 46)