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

3. X-ray Properties

4. 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

5. 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.

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

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

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

9. Artistic Talent

10. Artistic Talent

11. Your artistic talent…..

12. Your artistic talent….. Your signature

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

14. How does it affect our image?

15. The Control Console Where tech sets technical factors
B. _____
C. ____________
Only a ________________ individual is authorized to energize the console
The control console is device that allows the technologist to set technical factors (mAs & kVp) and to make an exposure.
Only a legally licensed individual is authorized to energize the console.

16. Control panel AKA Control Console

17. Producing optimal radiographs

18. PRIME FACTORS mAs kVp Distance (SID)
Exposure factors under the control of the radiographer.
Consists of the 3 prime factors
It will make a difference as to whether the image is optimal or not.

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

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

21. 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

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

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

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

25. ______ is the PRIMARY controlling factor of density

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

27. 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
Tube current is equal to the number of electrons flowing from the cathode to the anode per unit time

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

29. mAs
mA X s = mAs

30. mAs Reciprocity 100 mA x 1/4 = 25 mAs 200 mA x 1/8 = 25 mAs

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

32. mAs DOUBLED = DENSITY DOUBLED

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

35. Math Problems

36. CONTRAST THE DIFFERENCES BETWEEN: Blacks Whites Dark gray Light gray
The differences between adjacent densities. It gives us the various shades of grays on the IR.

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

38. Short scale of Contrast
_________________
Greater distance between densities

40. Long Scale of Contrast ______________ ______________M
Less distance between densities

41. 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

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

44. Optimal kVp Is 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 #)

45. 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

46. + 15% kvp % kvp

47. 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 __________
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.

53. Film Screen _____________ Too ______
too much x-ray photons reached the image receptor
Could be from too much mAs or too much kVp
too ______
Too little x-ray photons reached the image receptor
Could be from too little mAs or too little kVp
Overexposed
Referring to a radiograph that is too dark because too much x-radiation reached the image receptor
Underexposed
Referring to a radiograph that is too light because too little x-radiation reached the image receptor

58. X-Ray Machine Purpose:
provide a specific current (mA) & voltage (kV) to the x-ray tube
convert electrical energy to electromagnetic energy (x rays) in a controlled manner
control the energy of the x-ray photons
control the number of photons

59. kVp & mAs kVp = mAs quality of beam
intensity of how much tissue it can penetrate
mAs
the amount (quantity) of photons
time the beam is left on

60. kVp = energy mAs = amount QUALITY vs. QUANTITY

61. Source to Image Receptor Distance
SID -controlled and manipulated in the x-ray room

62. Intensity of the beam As distance _______: intensity ________
Inverse relation

63. Inverse square law Farther the distance of the x-ray tube to the IR
Photons have less chance of getting to IR
Due to divergent beam

64. How does distance affect IR exposure?
Increased distance: decreased exposure
________________
Decreased distance: increased exposure
Inversely proportional to the square of the distance
Intensity is ¼ of original
Intensity increases to 4 x’s the original exposure

65. INVERSE SQUARE LAW Used for RADIATION PROTECTION
When you change your distance from the “radiation source”
The intensity of radiation will be reduced by a square of the distance
MOVING AWAY FROM THE SOURCE
INCREASED – CLOSER TO SOURCE

66. DISTANCE
Distance from the radiation source should be kept as great as possible

67. Application of inverse square law principles can yield significant reductions in patient and operator radiation exposure.

69. INTENSITY IS SPREAD OUT…

70. Inverse Square Law Formula
Distance #2 - Squared
Intensity #1
Distance #1 - Squared
Intensity #2

71. How the current gets to the TUBE

72. Current from the outlet

73. Generator+ Transformers (where the power comes from)