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Diagnostic Imaging 1 > Intro > Flashcards

Intro Flashcards

1
Q

Which side of the X-ray tube do X-rays come out of?

A

Anode

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2
Q

How are X-rays created within the X-ray tube?

A

the cathode creates a lot of free electrons, when they hit the anode they become X-ray photons

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3
Q

What % of electrons become X-rays?

A

1-2% the rest turns into heat

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4
Q

X-rays move isotropically, what does this mean?

A

They move in every direction

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5
Q

What is primary radiation (PR)?

A

All the radiation between the source and the patient
Incident radiation or useful beam

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6
Q

What is Remnant Radiation?

A

Radiation which leaves the patient and is going to hit the image receptor
RR=PR-(Absorbed+Scattered)

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7
Q

What is secondary radiation?

A

radiation coming from a place other than the source or target

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8
Q

What is scattered radiation?

A

primary radiation which has been deflected or changed direction

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9
Q

What is CR?

A

Central ray - not to be confused with computed radiography
centre of the Xray beam

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10
Q

What is FS/T/S?

A

Focal spot, target or source - where the X-rays originate

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11
Q

What is SID?

A

Source to image receptor distance

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12
Q

What is SGD?

A

Source grid distance

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13
Q

What is SOD?

A

Source to object distance - the primary beam
also known as TOD (target to object distance), AOD (anode to object distance), and FOD (focal to object distance)

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14
Q

What is OID?

A

object to image receptor distance
also known as OFD - object film distance

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15
Q

What is mA?

A

milliamperes
- quantity or intensity
- one ampere is defined as the current that flows with electric charge of one Coulomb per second
- values of mA influence amount of radiation
- rate of radiation production

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16
Q

What is s?

A

value of time selected
- controls the duration of the exposure

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17
Q

What is mAs?

A

Milliampere seconds
- total quantity of radiation used for a particular exposure

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18
Q

What is kVp?

A

kilovolts peak (quality of radiation)
- determines penetrating ability of the radiation

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19
Q

What will happen to the wavelength of the X-ray photons if kVp is increased?

A

The wavelength will decrease, but the photon will have increased energy

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20
Q

What is attenuation?

A

any process that decreases/reduces the intensity of the beam

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21
Q

What factors affect attenuation?

A

Thickness, atomic number and physical density

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22
Q

Why does increased atomic number affect attenuation?

A

increased amount of outer shell electrons

23
Q

What is the atomic number of bone, muscle and water?

A

bone - 13.8
muscle - 7.4
water - 5.9

24
Q

What are the physical densities of bone, soft tissue and air?

A

bone - 1.8 g/cm3
soft tissue - 1.0 g/cm3
air - 0.001 g/cm3

25
Q

How does kVp affect absorption?

A

by increasing the kVp you are giving the X-ray photons more energy and a shorter wavelength this decreases absorption

26
Q

Does mAs affect absorption?

A

no

27
Q

What is high contrast?

A

lots of dark shades and brighter shades, few shades of grey
Brightness differences between structures is large

28
Q

What is low contrast?

A

many shades of grey, brightness differences between structures are small

29
Q

What is mA?

A

current (I)

30
Q

What is mAs?

A

total amount of e flow over entire exposure

31
Q

What is reciprocity?

A

variety of mA and time settings that could produce the same mAs

32
Q

What are the advantages to reciprocity?

A
  • control motion
  • focal spot size
  • breathing techniques
33
Q

Why would you want to use a smaller focal spot?

A

better spacial resolution - crisper edges

34
Q

What is the small focal spot limit by?

A

mA NOT mAs

35
Q

What is the inverse square law?

A

I1/I2=d2^2/d1^2

36
Q

What is the intensity maintenance law?

A

also known as the square law
mAs2/mAs1=d2^2/d1^2

37
Q

What is subject contrast?

A

a measurement of intensity of the remnant beam caused by differential absorption

38
Q

What does image contrast depend on?

A

subject contrast, scatter radiation, algorithms, processing, post processing

39
Q

kVp and intensity formula?

A

I1/I2 = (kVp1/kVp2)^2

40
Q

kVp, mAs and intensity?

A

I.e. solving for I2
I2 = I1 x (kVp1/kVp2)^2 x (mAs1/mAs2)

41
Q

What are grids?

A

Devices that reduce the amount of scattered radiation reaching the image receptor

42
Q

What factors affect scatter?

A

kVp, field size, thickness, composition of irradiated material

43
Q

How is a basic grid constructed?

A

strips of lead interspaced with radiolucent material

44
Q

What is the grid ratio?

A

GR=h/D
D is the width of the interspace material
h is the height of the grid

45
Q

If you increase the grid ratio, what happens to the amount of scatter reaching the IR?

A

decreases

46
Q

Different frequencies effect on grid?

A

higher frequency, thinner Pb strips, less visible
lower frequency, thicker Pb strips, more visible

47
Q

What is contrast improvement factor?

A

K = image contrast with grid/image contrast without grid
1.5-2.5
depends on kVp, patient thickness and field size

48
Q

What are the Bucky Factors?

A

How much of an increase in technique is needed compared to non-grid
No Grid - 1
5:1 - 2
6:1 - 3
8:1 - 4
12:1 - 5
16:1 - 6

49
Q

Who invented moving grids?

A

Dr. Hollis E Potter in 1920
moves to blur out grid lines

50
Q

What kind of movement do moving grids do?

A

either reciprocating (side to side 2-3cm) or oscillating (circular)

51
Q

Will the movement of the grid cause more grid cut-off?

A

a little bit

52
Q

What are the 4 types of grid errors?

A

off center
off level - angle mismatch
off focus - out of proper SID
upside down

53
Q

What is the air gap technique?

A

alternative to using a grid
increasing OID - scatter misses IR
1 foot of SID per inch of OID

54
Q

Magnification Factor

A

MF = SID/SOD
MF = Image size/object Size
object size= Image size/MF

Diagnostic Imaging 1 (4 decks)

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