Diagnostic Imaging- NBCE Part 2
X-ray machine is made up of? - ANS-Generator
X-ray tube
Control console
Cathode consists of - ANS-Small and Large filaments
Focusing cup
Filaments - ANS-- Serve as source of electrons in the production of x-ray and are made
of tungsten
- Thermionic emission occurs when a current is applied to the filament; the coil of the
wire becomes very hot, boiling off electrons
- The *temperature of the filament controls the quantity of electrons (mA) emitted from it
Number of electrons determines the number of x-rays created
Focusing cup - ANS-Part of the cathode that encases the two filaments.
This is where *thermionic emission occurs*
Anode is AKA - ANS-Target plate
Two types of radiation - ANS-1. Characteristic radiation
> 10~15%
> Does not contribute to the formation of the image
2. Bremsstrahlung radiation
> 85~90%
> Creates image
Photoelectric effect - ANS-Some of rays are completely absorbed by the patient
Scatter radiation can be decreased by? (3) - ANS-*Reducing* the beam size
*Increasing* the beam energy
> Increasing the kVp
,*Decreasing* the field size
> Using a collimator
> Grid
> Using the air-gap technique (reducing OFD)
Air-gap technique refers to? - ANS-The distance between the *object* and the *film*
Increasing mA (current) - ANS-Brings the *large filament* into play
(reducing > *small filament*)
Larger objects > Shorter exposure time
Density refers to?
And related to? - ANS-Overall blackness of the film
> Directly proportional to kVp and mA
Contrast refers to?
And related to? - ANS-Differences in the shades of gray in the film
> Indirectly related to kVp
1. Low contrast > Soft tissue (high kVp)
2. High contrast > Bone (low kVp)
Detail refers to?
And related to? - ANS-How clear the structures are visualized
> Increased FFD
> Decrease OFD
> Decrease kVp
Anode heel effect - ANS-Heel - bottom part of the *anode*
Strength of the x-ray beam is
> *Stronger* on the cathode side
> *Weaker* on the anode side
One should place the *cathode* side closer to the larger or fatter part of the object (*FAT
CAT*)
____ kVp results in less tissue damage - ANS-Increased
, > More x-rays penetrate the body with *less tissue interaction*
Increased kVp
- Density
- Contrast
- Size distortion
- Detail
- Exposure time - ANS-- Density +
- Contrast -
- Size distortion =
- Detail =
- Exposure time +
kVp - ANS-- The force applied to *accelerate the electrons* from the cathode to the
anode at the time of exposure
- Greater the force, the greater the numbers of high energy x-ray photons
- High kVp = high energy = strong penetration
Relationship betwen kVp and density - ANS-Increase kVp by 15% will double the overall
density
Increased mA
- Density
- Contrast
- Size distortion
- Detail
- Exposure time - ANS-- Density +
- Contrast -
- Size distortion =
- Detail *+*
- Exposure time +
Increased FFD
- Density
- Contrast
- Size distortion
- Detail
- Exposure time - ANS-- Density -
X-ray machine is made up of? - ANS-Generator
X-ray tube
Control console
Cathode consists of - ANS-Small and Large filaments
Focusing cup
Filaments - ANS-- Serve as source of electrons in the production of x-ray and are made
of tungsten
- Thermionic emission occurs when a current is applied to the filament; the coil of the
wire becomes very hot, boiling off electrons
- The *temperature of the filament controls the quantity of electrons (mA) emitted from it
Number of electrons determines the number of x-rays created
Focusing cup - ANS-Part of the cathode that encases the two filaments.
This is where *thermionic emission occurs*
Anode is AKA - ANS-Target plate
Two types of radiation - ANS-1. Characteristic radiation
> 10~15%
> Does not contribute to the formation of the image
2. Bremsstrahlung radiation
> 85~90%
> Creates image
Photoelectric effect - ANS-Some of rays are completely absorbed by the patient
Scatter radiation can be decreased by? (3) - ANS-*Reducing* the beam size
*Increasing* the beam energy
> Increasing the kVp
,*Decreasing* the field size
> Using a collimator
> Grid
> Using the air-gap technique (reducing OFD)
Air-gap technique refers to? - ANS-The distance between the *object* and the *film*
Increasing mA (current) - ANS-Brings the *large filament* into play
(reducing > *small filament*)
Larger objects > Shorter exposure time
Density refers to?
And related to? - ANS-Overall blackness of the film
> Directly proportional to kVp and mA
Contrast refers to?
And related to? - ANS-Differences in the shades of gray in the film
> Indirectly related to kVp
1. Low contrast > Soft tissue (high kVp)
2. High contrast > Bone (low kVp)
Detail refers to?
And related to? - ANS-How clear the structures are visualized
> Increased FFD
> Decrease OFD
> Decrease kVp
Anode heel effect - ANS-Heel - bottom part of the *anode*
Strength of the x-ray beam is
> *Stronger* on the cathode side
> *Weaker* on the anode side
One should place the *cathode* side closer to the larger or fatter part of the object (*FAT
CAT*)
____ kVp results in less tissue damage - ANS-Increased
, > More x-rays penetrate the body with *less tissue interaction*
Increased kVp
- Density
- Contrast
- Size distortion
- Detail
- Exposure time - ANS-- Density +
- Contrast -
- Size distortion =
- Detail =
- Exposure time +
kVp - ANS-- The force applied to *accelerate the electrons* from the cathode to the
anode at the time of exposure
- Greater the force, the greater the numbers of high energy x-ray photons
- High kVp = high energy = strong penetration
Relationship betwen kVp and density - ANS-Increase kVp by 15% will double the overall
density
Increased mA
- Density
- Contrast
- Size distortion
- Detail
- Exposure time - ANS-- Density +
- Contrast -
- Size distortion =
- Detail *+*
- Exposure time +
Increased FFD
- Density
- Contrast
- Size distortion
- Detail
- Exposure time - ANS-- Density -
