Components of Image Quality & Radiographic Artifacts

1. Components of Image Quality & Radiographic Artifacts Radiologic Technology A SPRING 2012

2. X-ray Exposure Factors • Radiographic Density & Contrast • Components of Image Quality • Radiographic Artifacts

3. Review • Primary radiation exits the tube • Interacts with various densities in the body • Photons may be absorbed • Scattered • Passed through without any interference to the cassette or image receptor (IR)

4. How well we can see something on the image

5. Image detail is affected by:Photographic propertiesand Geometric properties

6. Photographic Properties • Contrast • Density

7. Factors Affecting Density • Primary control factor • mA • Time (seconds) • Influencing factors • kVp • Grids • Beam restriction • Body structures (size of pt, pathology • Processing • SID & OID • Film Screen combinations

8. Primary Controlling Factor of Density • mAs • mA = AMOUNT of electrons sent across the tube combined with TIME (S) = mAs • mAs controls DENSITY on radiograph • primary function of mAs is DENSITY

9. Imagine this… • If the mA station is changed from 200 to 400 mA, twice as many electrons will flow from the cathode to the anode. • From 10 mA to 1000 mA = 100 x more • mA controls how many electrons are coming at the target • mAs is a combination of how many and for how long(seconds)

10. 10 mA 1000 mA

12. Changing Mas – Changes Density+ 25 % + 50 % mas

13. Influencing Factor on Density:kVp

14. Change in kVp • kVp controls the energy level of the electrons and subsequently the energy of the x-ray photons. • A change from 72 kVp will produce x-rays with a lower energy than at 82 kVp • Difference between a ball traveling 72 mph and 82 mph (how much energy did it take to throw the ball at the rates?)

15. + 15% kvp - 15% kvp This will also influence the density on the image Increasing kVp = increase energy reaching the IR

16. Radiolucent vs. Radiopaque • Radiolucent materials allow x-ray photons to pass through easily (soft tissue). • Radiopaquematerials are not easily penetrated by x-rays (bones)

17. Transmission no interaction Responsible for dark areas Scatter (grays) – produces no diagnostic info Absorption (photoelectric effect) Responsible for light areas Creating the Image

18. Images • DENSITY = THE AMOUNT OF BLACKENING “DARKNESS” ON THE RADIOGRAPH (mAs) • CONTRAST – THE DIFFERENCES BETWEEN THE BLACKS TO THE WHITES (kVp)

19. Why you see what you see… • The films or images have different levels of density – different shades of gray • X-rays show different features of the body in various shades of gray. • The gray is darkest in those areas that do not absorb X-rays well – and allow it to pass through • The images are lighter in dense areas (like bones) that absorb more of the X-rays.

20. Patient Body Size and Pathology

21. 3 Different Body HabitusHypersthenic Sthenic Hyposthenic Dr. Charman, Eric Guzman, Adam Guzman Thank you to the 3 men in my life !  DCharman

22. PATHOLOGY • Pleural • Effusion • Excessive fluid in lung • More dense than air

23. Pneumonia

24. The right lung is almost completely collapsed; vascular shadows can not be seen in this area (arrow). Lung collapses No tissue in space Easy to penetrate with x-ray photons Pneumothorax

25. LungCancer

26. LUNG CANCER

27. Density and Images

28. Goal: Producing optimal radiographsDENSITY Too dark Too light

30. Controlling Factor ofContrast

31. Controlling Factor of Contrast • Kilovolts to anode side – kVp • Kilovolts controls how fast the electrons are sent across the tube • kVp – controls CONTRAST on images

32. Producing optimal radiographsContrast Scale Long scale short scale

34. Scale of Contrast? Which one is “better” How does the kVp affect these images?

35. Beam Restriction and Grids

36. Creates fog Lowers contrast (more grays) Increases as kV increases Field size increases Thickness of part increases Scatter

37. Effects of collimation (beam restriction) on scatter

38. Collimate to area of interest -reduces scatter and radiation dose to the patient

39. Grids • A device with lead strips that is placed between the patient and the cassette • Used on larger body parts to reduce the number of scattering photons from reaching the image

40. Basic Grid Construction • Radiopaque lead strips • Separated by radiolucent interspace material - Typically aluminum • Allow primary radiation to reach the image receptor (IR) • Absorb most scattered radiation • Primary disadvantage of grid use • Grid lines on film

41. GRIDS

42. Grid is placedbetween patient (behind table or upright bucky) & cassette

43. Grids absorb scatter –prevents it from reaching the image GRID STOPS SCATTER

45. Contrast changes with the use of a grid Less scatter radiation – shorter scale = “better contrast” With Grid No Grid

46. GRIDS CAN LEAVE LINES ON THE IMAGE

47. GEOMETRIC Properties • Recorded Detail • DISTORTION • Size distortion • Magnification • Shape distortion • Elongation • Foreshortening

48. RECORDED DETAIL

49. RECORDED DETAIL • The degree of sharpness in an object’s borders and structural details. • How “clear” the object looks on the radiograph

50. Recorded Detail • The degree of sharpness in an object’s borders and structural details. • Other names: -sharpness of detail -definition -resolution -degree of noise