1. Introduction to Radiography
Patient Care
Chapter 1
Mrs. Nelms

2. History Discovery by Roentgen 1st documented medical application
Snook and his contribution to electricity
Pupin
Thomas Edison and Dally
Eastman Kodak and film
Training of x-ray technicians

3. Overview of Radiographic Procedure
Cassette, alignment of the cassette tray, control booth/panel, what happens during the exposure

4. X-ray Production 4 requirements for the production of x-ray Vacuum
Source of electrons
Target for the electrons
High potential difference or voltage between the electron source and the target

5. Vacuum The x-ray tube itself provides the vacuum
It is referred to as a glass envelope
Made of pyrex glass to withstand heat and is fitted on both ends for electrical connections
All of the air is removed (hence the term ‘evacuated glass tube’; this is so that the gas molecules will not interfere with the process of x-ray production

6. Source of Electrons
The source of electrons is the wire filament (made of tungsten)
An electric current moves through this wire to heat it
The heat speeds up the movement of electrons and moves them away from the nucleus; the outer-shell electrons get so far away from the nucleus that they are flung out of orbit. This forms an “electron cloud” around the filament. These free electrons or “space charge” provide the electrons needed for x-ray production.

7. Target for the Electrons
The target is at the opposite end of the filament
It is also made of tungsten and is a smooth, hard surface where the electrons travel to form x-rays.

8. The Potential Difference or Voltage
Voltage required for x-ray production is provided by a high-voltage transformer
The two wires coming out of the glass envelope (mentioned previously) are connected so that the anode side is positive and the cathode end is negative.
The highly positive electrical potential at the anode or target end attracts the highly charged negative electrons (they move across the tube forming an “electron stream”)
When these electrons strike the target, the kinetic energy of their motion must be converted into a different kind of energy. 99% of it is converted into heat, but the rest is converted to x-rays.

9. Characteristics of Radiation
X-rays are classified as electromagnetic energy
They have both electrical and magnetic properties
They change the field in which they pass through both electrically and magnetically
This change in the field occurs in a repeating wave form, a pattern known as a sine wave

10. The Sine Wave
Amplitude: distance between the crest and the valley or height of the wave
Wavelength: distance from one crest to another
Frequency: the number of times per second the crest passes a given point
All electromagnetic energy has the same velocity (186,000 miles per second)
When the wavelength is short, crests are close together; when the wavelength is long, crests are further apart. Close crests- high frequency; far apart crests- low frequency.
Photon: smallest possible unit of electromagnetic energy
Quanta: bundles of photons (singular is quantum)
Electromagnetic spectrum includes: x-rays, gamma rays, visible light, microwaves and radio waves.
Ionizing radiation: radiation with a wavelength shorter than one nanometer. Ionizing radiation has sufficient energy to remove an electron from an atomic orbit. X-rays are ionizing because their wavelength is about 0.1 nanometer (a billionth of an inch)

12. X-rays and Light Both are part of the electromagnetic spectrum
Both travel in straight lines
Both have an effect on photographic emulsions
Both have biological effects (they can change living organisms)
X-rays are capable of more harmful effects of light because of their greater energy
X-rays cannot be detected by the human senses; we can visibly see light- we cannot see x-rays. This is an important concept when considering radiation safety.

13. X-ray Penetration
X-rays can penetrate objects that are opaque to light
Differential penetration; depending on the object thickness and density will determine the penetrability of x-rays
Remnant radiation: radiation that is able to pass completely through the body and exit. This is the radiation that is recorded on an x-ray

14. The X-ray Beam Primary Beam
Radiation Field (controlled by a collimator)
Central Ray

15. Scatter Radiation
When the primary beam encounters matter, a portion is absorbed within the matter. This results in the production of scatter radiation. It has less energy than the primary beam, but is extremely hard to control. It will bounce from the source in all directions causing unwanted exposure to the film and unwanted exposure to anyone in the room.

16. X-ray Beam Attenuation
To review, there is the primary beam, scatter radiation and remnant radiation. The chart on page 9 will help distinguish each type’s characteristics.

17. The X-ray Tube

18. X-ray Tube Housing

19. X-ray Tube Support

20. Collimator
The collimator allows the radiographer to vary the size of the radiation field and to indicate with a light beam the size, location and center of the field.

21. Radiographic Table

22. Grids and Buckys Bucky: moving grid device below the table
Grid: situated between the table top and the film

23. Upright Cassette Holders

24. Transformer

25. Control Console
Locate these items on the control panel of the classroom x-ray machine
Off/on mA
kVp
Timer
mAs
Bucky
AEC (ours does not have this)
Meters
Prep or rotor switch
Exposure switch
accessories

26. Fluroscopic Unit

27. Factors of Radiographic Exposure
Exposure time
Milliamperage or mA
Kilovoltage peak or kVp
Distance

28. Exposure Time How long the exposure will continue
Measured in units of seconds, fractions of seconds or milliseconds (thousandths of seconds)
Longer exposure will produce a darker film; conversely a shorter exposure will produce a lighter film
Patient dose is directly proportional to exposure time
Discuss AEC

29. Milliamperage Measure of the current flow in the x-ray tube
Determines the amount of electrons available to cross the tube, thus the rate at which x-rays are produced
mA is an indication of the number of x-ray photons that will be produced per second
mA setting will determine how much exposure time is needed to produce a given amount of exposure
mAs= mA x time (seconds)
mA can affect the focal spot size in dual focus tubes

30. Kilovoltage Potential difference across the x-ray tube
Changes in kV will cause changes to the film
Typcial kV range in x-ray is between 40 and 150 in increments of 1 or 2 kilovolts

31. Distance
Distance between the source and the film is known as SID (source-image distance)
The change in x-ray beam intensity that results from changes in SID is expressed as the inverse square law

32. Image Receptor Systems
Cassette
Film
Film processing
Filmless radiography

33. Image Quality
Density
Contrast
Definition
Distortion

34. Radiation Units
Roentgen or C/kg
Rad or gray
Rem or sievert

35. Biological Effects of X-Ray
Law of Bergonie and Tribondeau
Short term effects
Long term effects
Genetic effects

36. Radiation Safety Personnel safety Monitoring devices
Effective dose equivalent limits- ALARA
Patient protection
Gonadal shielding
Pregnancy and radiation