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Donny RAD SCI 2 > Exam 1 Review guide > Flashcards

Exam 1 Review guide Flashcards

1
Q

Photoelectric effect strikes:

A

inner shell electron

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2
Q

In Photoelectric absorption the electron absorbs all:

A

the x-ray’s photon’s energy

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2
Q

In photoelectric effect the x-ray photon ceases:

A

to exist

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3
Q

In photoelectric effect the inner shell electron ____ ups &:

A

speeds (excites)
leaves the atom

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4
Q

In photoelectric effect the energy in excess of binding energy is given to:

A

the inner-shell electron

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4
Q

photoelectric effect is _____ likely to occur when the _____ of the incident x-ray is slightly ______ than the binding energy of the orbital electron

A

more
energy
higher

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5
Q

In photoelectric effect increased kVp leads to:

A

decreased photoelectric absorption
(Beam is too fast/intense)

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6
Q

In Compton scatter the x-ray photon ceases:

A

to exist

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7
Q

In Compton scatter _________ interacts (strikes) with an:

A

incident x-rays
outer shell electron

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7
Q

In photoelectric effect increased atomic number leads to increased

A

photoelectric absorption (attentuation)
(because more things to interact with)

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8
Q

In Compton scatter the electron absorbs:

A

all the incident x-rays energy

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8
Q

In Compton scatter outer shell electron speeds up and leaves:
what is this called?

A

the atom (recoil electron)
(Excess energy leaves as a scatter photon)

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8
Q

In Compton scatter some of the energy excess of binding energy is given to an:

A

outer shell electron

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9
Q

In Coherent when an incident x-ray interacts with an orbital electron it is:

A

Thompson

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9
Q

Attenuation can be affected by?

A

-Tissues thickness (every 4 cm = 50% xray beam attenuation)
-tissue atomic number (more z#= more attenuation)
-tissue density (most important ex: air vs muscle vs fat) muscle most dense/ air least dense

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10
Q

In Compton scatter remaining energy is ______ as a new x-ray and leaves the _____ in a random direction

A

reemitted
atom

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11
Q

Compton scatter is proportionally more likely:

A

at high kVp levels
(this is bc higher kVp levels have lower absorption rate but compton remains consistent at all levels)

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11
Q

Both the photoelectric effect and compton scatter lead to

A

ionization
(the removal of an electron from orbit and net positive charge to the atom)

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12
Q

In coherent scatter when the energy of the incident photon is ______ than the ________ no ________ occurs

A

less
binding energy
ionization

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12
Q

In coherent scatter when an incident x-ray interacts with an entire atom is it called:

A

Rayleigh

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12
Q

In coherent scatter the orbital electron reaches a temporary:

A

state of excitation

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12
Q

Attenuation is?
What different interactions result in attenuation?

A

Reduction in the number/intensity of x-rays reaching the IR (through scatter/absorption)
Photoelectric (absorption)
Coherent scatter (absorption)
Compton (both scatter & absorption)

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13
Q

mAs is a measurement of what?
it is considered:
what is it not?

A

electron flow in a conductor
an electrical term
a unit of radiation output

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13
Q

In coherent scatter the incident x-ray continues:

A

in a new direction

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13
Q

In coherent scatter no _____ occurs

A

energy transfer

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14
Q

mAs math:
100 mA and .5 sec

A

50 mAs

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14
Q

mAs is the primary controller of:

A

intensity/quanity in the remnant beam

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14
Q

Attenuation is absorption & scattering as a result of:

A

photoelectric effect
compton scatter
coherent scatter

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14
Q

For each 4cm of tissue requires:
For every 4 cm of tissue how much x-ray beam attenuation is occuring?

A

doubling of mAs & kVp by:
15% kVp
100% mAs
- 50% x-ray beam attenuation

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15
Q

mA is limited by what?

A

Focal spot size

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15
Q

To calculate the mAs we:

A

multiply mA x Time

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15
Q

Radiologic time is measured in?

A

seconds
.25 secs or 250 ms or 1/4 second (all the same)

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15
Q

How do we reduce motion?

A

setting the shortest time while maintaining same mAs output
(Shorter time requires more mA)

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15
Q

Doubling in mAs leads to:

A

doubling of intensity or quantity

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15
Q

mAs math:
300 mA and .2 sec

A

60 mAs
(300 x .2)

16
Q

What does kVp control?

A

the quality of the x-ray beam

16
Q

mAs math:
200 mA and .2 sec

A

40 mAs

16
Q

Maintaining density:
150 mAs to 300 mAs
72 kVp to ___ ?

A

61.2 (reduced 15%, cuts exposure in half)’
mAs doubled
kVp needs to come down 15% to maintain

16
Q

Kilovoltage is the measurement of

A

electrical force

17
Q

the small increase of 15% kvp will?

A

double the exposure to the image receptor

17
Q

What is penumbra?
Is it good or bad?

A

blurry or unsharp edges of the shadow or image

17
Q

kVp means?

A

kilo voltage peak (the highest value in electrical generator)

17
Q

when the kvp increases 15% patient exposure increases by:

A

1/3

18
Q

kVp math:
increase kVp 15% of 70 kvp:
decrease kVp 15% of 100 kVp:

A

80.5 (70 x 1.15)
85 (100 x .85)

18
Q

OID stands for?

A

object image distance (patient distance from IR)

18
Q

What is preferred, optimal kVp or minimal kvp?
what is higher in kVp out of the 2?

A

optimal kVp

18
Q

What does a higher kVp do?

A

increase the x-ray’s ability to penetrate through a particular tissue

18
Q

What is remnant radiation?

A

the part of the x-ray beam that has passed through the patient
(Leftovers from the primary beam)

19
Q

SID stands for?

A

source to image distance (x-ray tube to IR)

20
Q

SOD stands for?

A

Source to object distance (x-ray tube to patient)

20
Q

How much of the primary beam becomes remnant radiation?

A

less than 1%

21
Q

What is elongation?

A

the object appears to be longer than its actual size

21
Q

What is umbra?

A

is the ‘‘pure” shadow or image of uniform darkness
(crisp shadow line)

22
Q

What is shape distortion?

A

the difference between the actual shape of the object and the shape of its projected image
(Difference between actual object shapes
& the image shape)

22
Q

As a radiographer do we want pneumbra?

A

no, we want to minimize this

22
Q

What is the relationship with SID and pneumbra & spatial resolution?

A

the greater the SID the smaller the pneumbra & higher the spatial resolution

23
Q

What is distortion?

A

misrepresentation of the size or shape of an object

24
Q

what is foreshortening?

A

the object appears to be shorter than its actual size

25
Q

How do we calculate the mag factor?

A

dividing SID/SOD

25
Q

How can we reduce shape distortion?

A

properly aligning the:
tube
(Object) part
Image receptor

26
Q

What is size distortion?
What is it also called?

A

misrepresentation of the size of the object
aka magnification

27
Q

How can size distortion (magnification) be reduced?

A

decreasing OID or
increasing SID

28
Q

What affects contrast?

A

kVp (low kvp = high contrast)
image receptor (grids)
computer algorithms (AEC)
patient factors (tissue density)

28
Q

Mag Factor math:
SID= 72
SOD=66

A

1.09 mag factor

28
Q

Mag Factor math:
An object that measures 6 cm is radiographed using SID of 48 and OID of 4. How many centimeters will the object measure on the completed radiograph?

A

6.54cm
(48 (SID) - 4 (OID) = 44 SOD
48 (SID) / 44 (SOD)= 1.09
1.09 x 6 cm= 6.54cm

29
Q

What is spatial resolution?
What is also referred to as?

A

the sharpness of the structural edges around the image
AKA detail, sharpness, or decreased pneumbra (OR LOW BLUR)

30
Q

How is resolution (spatial resolution) measured?

A

using a line-pair test tool
(measured in line-pairs per millimeter or LP/mm)

31
Q

what affects spatial resolution?

A

motion
focal spot size
distance (SID, SOD, OID)
patient factors (OID or motion)
angulation (elongation/foreshortening)

32
Q

What is contrast?

A

the difference between 2 adjacent brightness levels

33
Q

What can contrast be referred to as?
which is?

A

gray scale
the number of different brightness levels in a x-ray

33
Q

Low contrast =
high contrast =

A

long scale (many greys)
short scale (black & white)

33
Q

What is SNR?
What should it always be greater than?

A

Signal to noise ratio
one

33
Q

What is noise?

A

undesirable image input that interferes with ability to visualize the x-ray

34
Q

What can be used to increase subject (patient) contrast?

A

barium & iodine

34
Q

What is quantum mottle?
What is the opposite?

A

insufficient number of x-rays reaching the image receptor
scatter is too much x-rays reaching the image receptor

35
Q

What causes quantum mottle?
What is usually the cause?

A

low mAs
low kVp
or difficult anatomy to penetrate
usually low technique, especially mAs

35
Q

What is postprocessing?

A

adjustment of the image by a rad tech or rad at a workstation

36
Q

What is window level?
What is window width?

A

post-processing of image brightness
post-processing if image contrast

37
Q

For digital systems, what is preferred quantum mottle or scatter?

A

Scatter
(the digital systems are very good at filtering out too much information)

38
Q

More kvp = ____ scatter
more volume = _____ scatter more volume

A

more
more
(why collimation is key, and optimal kVp)

39
Q

Low contrast =
High contrast=

A

Long scale & low kvp
Short scale & high kVp

40
Q

Low contrast =
High contrast=

A

Long scale & low kvp
Short scale & high kVp

41
Q

What is the rule regarding tissues thickness?

A

for every 4cm of tissue thickness 50% of x-ray beam is attenuated

42
Q

What does high tissue atomic number mean for attenuation?

A

means more attenuation due to more interactions
(more electrons higher chance for photelectric absorption)

43
Q

What does higher tissue density mean for attenuation?

A

more attenuation
(implants most, then bone, then muscle, then fat, and least dense is air)
more dense objects show up more dominantly on the x-ray

44
Q

Who sets the standards for optimal contrast/brightness settings?

A

the radiologists

Donny RAD SCI 2 (4 decks)

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