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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
In coherent scatter no _____ occurs
energy transfer
14
mAs math: 100 mA and .5 sec
50 mAs
14
mAs is the primary controller of:
intensity/quanity in the remnant beam
14
Attenuation is absorption & scattering as a result of:
photoelectric effect compton scatter coherent scatter
14
For each 4cm of tissue requires: For every 4 cm of tissue how much x-ray beam attenuation is occuring?
doubling of mAs & kVp by: 15% kVp 100% mAs - 50% x-ray beam attenuation
15
mA is limited by what?
Focal spot size
15
To calculate the mAs we:
multiply mA x Time
15
Radiologic time is measured in?
seconds .25 secs or 250 ms or 1/4 second (all the same)
15
How do we reduce motion?
setting the shortest time while maintaining same mAs output (Shorter time requires more mA)
15
Doubling in mAs leads to:
doubling of intensity or quantity
15
mAs math: 300 mA and .2 sec
60 mAs (300 x .2)
16
What does kVp control?
the quality of the x-ray beam
16
mAs math: 200 mA and .2 sec
40 mAs
16
Maintaining density: 150 mAs to 300 mAs 72 kVp to ___ ?
61.2 (reduced 15%, cuts exposure in half)' mAs doubled kVp needs to come down 15% to maintain
16
Kilovoltage is the measurement of
electrical force
17
the small increase of 15% kvp will?
double the exposure to the image receptor
17
What is penumbra? Is it good or bad?
blurry or unsharp edges of the shadow or image
17
kVp means?
kilo voltage peak (the highest value in electrical generator)
17
when the kvp increases 15% patient exposure increases by:
1/3
18
kVp math: increase kVp 15% of 70 kvp: decrease kVp 15% of 100 kVp:
80.5 (70 x 1.15) 85 (100 x .85)
18
OID stands for?
object image distance (patient distance from IR)
18
What is preferred, optimal kVp or minimal kvp? what is higher in kVp out of the 2?
optimal kVp
18
What does a higher kVp do?
increase the x-ray's ability to penetrate through a particular tissue
18
What is remnant radiation?
the part of the x-ray beam that has passed through the patient (Leftovers from the primary beam)
19
SID stands for?
source to image distance (x-ray tube to IR)
20
SOD stands for?
Source to object distance (x-ray tube to patient)
20
How much of the primary beam becomes remnant radiation?
less than 1%
21
What is elongation?
the object appears to be longer than its actual size
21
What is umbra?
is the ''pure" shadow or image of uniform darkness (crisp shadow line)
22
What is shape distortion?
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
As a radiographer do we want pneumbra?
no, we want to minimize this
22
What is the relationship with SID and pneumbra & spatial resolution?
the greater the SID the smaller the pneumbra & higher the spatial resolution
23
What is distortion?
misrepresentation of the size or shape of an object
24
what is foreshortening?
the object appears to be shorter than its actual size
25
How do we calculate the mag factor?
dividing SID/SOD
25
How can we reduce shape distortion?
properly aligning the: tube (Object) part Image receptor
26
What is size distortion? What is it also called?
misrepresentation of the size of the object aka magnification
27
How can size distortion (magnification) be reduced?
decreasing OID or increasing SID
28
What affects contrast?
kVp (low kvp = high contrast) image receptor (grids) computer algorithms (AEC) patient factors (tissue density)
28
Mag Factor math: SID= 72 SOD=66
1.09 mag factor
28
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?
6.54cm (48 (SID) - 4 (OID) = 44 SOD 48 (SID) / 44 (SOD)= 1.09 1.09 x 6 cm= 6.54cm
29
What is spatial resolution? What is also referred to as?
the sharpness of the structural edges around the image AKA detail, sharpness, or decreased pneumbra (OR LOW BLUR)
30
How is resolution (spatial resolution) measured?
using a line-pair test tool (measured in line-pairs per millimeter or LP/mm)
31
what affects spatial resolution?
motion focal spot size distance (SID, SOD, OID) patient factors (OID or motion) angulation (elongation/foreshortening)
32
What is contrast?
the difference between 2 adjacent brightness levels
33
What can contrast be referred to as? which is?
gray scale the number of different brightness levels in a x-ray
33
Low contrast = high contrast =
long scale (many greys) short scale (black & white)
33
What is SNR? What should it always be greater than?
Signal to noise ratio one
33
What is noise?
undesirable image input that interferes with ability to visualize the x-ray
34
What can be used to increase subject (patient) contrast?
barium & iodine
34
What is quantum mottle? What is the opposite?
insufficient number of x-rays reaching the image receptor scatter is too much x-rays reaching the image receptor
35
What causes quantum mottle? What is usually the cause?
low mAs low kVp or difficult anatomy to penetrate usually low technique, especially mAs
35
What is postprocessing?
adjustment of the image by a rad tech or rad at a workstation
36
What is window level? What is window width?
post-processing of image brightness post-processing if image contrast
37
For digital systems, what is preferred quantum mottle or scatter?
Scatter (the digital systems are very good at filtering out too much information)
38
More kvp = ____ scatter more volume = _____ scatter more volume
more more (why collimation is key, and optimal kVp)
39
Low contrast = High contrast=
Long scale & low kvp Short scale & high kVp
40
Low contrast = High contrast=
Long scale & low kvp Short scale & high kVp
41
What is the rule regarding tissues thickness?
for every 4cm of tissue thickness 50% of x-ray beam is attenuated
42
What does high tissue atomic number mean for attenuation?
means more attenuation due to more interactions (more electrons higher chance for photelectric absorption)
43
What does higher tissue density mean for attenuation?
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
Who sets the standards for optimal contrast/brightness settings?
the radiologists

Donny RAD SCI 2 (4 decks)

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