X-Ray Machine

Question 1

Glass vacuum tube:

Answer 1

• All air removed
• Surrounds electrodes of x-ray tube to provide a vacuum
• The aperture or window: thin segment of the glass that allows maximum emission of x-rays and minimum absorption by the glass

Question 2

Leaded glass housing:

Answer 2

• Prevents x-rays from going in all directions

Question 3

Cathode(-)

Answer 3

• Serves as the source of e- to be directed at anode
• Composed of:
  
  • Filament (tungsten wire): Filament that lies in a focusing cup: heated to give off e- (thermionic emission)
  • Focusing cup: e- from focusing cup are directed to focal spot
  • mA control regulaties
    
    1. Step-down transformer
    2. Heating of the filament
    3. Quantity of electrons “boiled off” during thermionic emission
  • Because charges repel —– the electron beam is directed to a small area on the anode

Question 4

Anode (+)

Answer 4

Composed of:
*Tungsten target (high atomic#)
*Copper stem (remember tungsten & copper) that functions to conduct heat away from the target
*Focal spot: portion of a target bombarded by electrons
Convert e- from filament into photons
Kilovoltage control regulations the:
*Step-up transformer
*Voltage between the cathode and the anode
*Accelerating potential (speed) of electrons

Question 5

Focal Spot:

Answer 5

• Sharpness of radiograph go up^ as size of radiation source go down
• Heat go up^ as focal spot go down in size

Question 6

Power Supply:

Answer 6

*Ohm’s Law: Volts = Amperes (I) x Resistance (R)
(electrical potential) (rate of e- flow)
Voltage = kVp. Describes the potential differences between the (-) and (+) and therefore, the speed or force of the moving e- toward the (+) charge

Question 7

Power Supply:

Answer 7

Transformer (changes potential difference of incoming electrical energy to any desired level)
1.Provide low-Volt current to heat filament by use of step-down transformer
*Operation regulated by mA switch: adjusts R and therefore current flow —- regulates temp. of filament—–Quantity of x-rays
2.Step-up transformer
*Increases the voltage sufficiently to propel electrons across the vacuum tube circuit to produce x-ray energy
3.Generate high difference between anode/cathode
*Controlled by kVp dial - selects varying V —- controls V between anode & cathode
*V to up^ = go up^ speed e- toward anode

Question 8

PID: Position-indicating device

Answer 8

*An open ended, circular or rectangular “cone” that extends from the tube head toward the image receptor
*Federal regulations(size):7cm/ 2.75in diameter
*(PID)Length that go up^ focal-to-object distance creates a less divergent beam
*Use fastest image receptor system: “F” speed intraoral film requires the least amt of radiation to produce a diagnostic image
* Longer PID = produce x-ray beam that is less divergent
- Decrease radiation exposure
- Provide better image resulution