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Flashcards in Introduction Deck (29)
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1

Radiation

The transfer of energy as particles or electromagnetic (EM) waves

2

Ionizing radiation

Radiation with sufficient energy (>15eV) to cause3 an atom or molecule that it reacts with to lose an electron

3

Production of X-Ray

Occurs through the conversion of energy within particulate radiation (electrons) to electromagnetic energy (X-rays)

4

Focusing cup

Negatively charged, repels the electrons and "focuses" the electron cloud toward the anode

5

KeV

Kiloelectron volt
The measure of the energy of a photon or electromagnetic wave

6

KVp

Kilovoltage peak applied across the tube
Beam includes many other energy X rays
Average energy of the beam is 1/3 - 1/2 KVp

7

Photoelectric effect (PE)

Ion pair created
Photon totally absorbed and does not contribute to image formation

8

Compton scatter (CS)

Ion pair created
Only some of the photon (X-Ray) energy is absorbed, but still continues as a lower energy X-Ray photon in a new direction
Probability of interaction is proportional to physical density of the subject/ (Energy)

9

Increased kVp decreases likelihood of

Compton scatter

10

Increased KVP decreased likelihood of

Photoelectric effect

11

Increased atomic number

Increased likelihood of photoelectric effect
No effect on Compton

12

Thickness/density of object increases

Compton scatter

13

Latitude

Maximum difference in Radiographic density of anatomical structures that can be evacuees on a given radiograph
Inversely related to contrast with many shades of gray
High KVp, low mAS
Used to abdomen and thoracic evaluation
The ability of a film to record differences in density (recognizable differences in shades of gray
Increase KVp by 15%
One-half mAS

14

Contrast

Difference in the photo density between two adjacent anatomic stuctures
Very short gra scale
Low KVp, high mAS
Used for musculoskeletal techniques
Decrease KVp by 15%
Done mAS

15

More scatter will be produced with increases in

KVp setting (beam energy)
Field size (collimating on)
Patient thickness

16

Reducing scatter after X-Ray productions

Grids
Air gap

17

Grids

Carefully fabricated series of radiopaque material (lead) alternated with strips of radiolucent material
Transmits only those X-rays on a straight line from the source to the image receptor

18

Grid ratio =

Height of strips / space between the space

19

Three components of the image recording system

Film
Intensifying screens
Cassette

20

Intensifying screens

Converts X-Ray energy into visible light which then exposes the film

21

Digital imaging and communications in medicine

DICOM
Protocol intended to standardize the way in which images are stored

22

Picture archive and communication system

PACS
Stage of DICOM images

23

Direct digital radiography

DR
X-rays converted to electronic signal
Immediate display (3-4 seconds)

24

Computed radiography

CR
Use cassettes with image plate
Phosphorescence records and stop later image
Read by "laser"
Similar to film-screen systems as far as workflow

25

Screen construction

Protective coating
Phosphor
Reflective layer
Base

26

Phosphor

High atomic number
Active layer
Emits layer
Rare Earth - older screens calcium tungstate

27

Screen speed

Relative number that identifies the efficiency of conversion of X-Radiatio into light
Determined by - phosphor type, crystal size, secondary factors

28

Advantages of intensifying screens

Decrease X-Ray dose to patient
Decrease X posture times
Increase image contrast

29

Disadvantages to intensifying screens

Decrease detail
Artifacts