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RAD SCI REVIEW FOR MOCK Flashcards

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1
Q

what does photoelectric effect strike? what happens the x-ray photon? what does the inner shell electron do? in photoelectric effect increased kVp leads to?

A

inner shell electron
ceases to exist
absorbs all the x-ray photon’s energy
decreased photoelectric absorption (beam is too fast/intense)

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2
Q

photoelectric effect is _____ likely to occur when the _____ of the incident x-ray is slightly ______ than the binding energy of the orbital electron
In photoelectric effect the energy in excess of binding energy is given to:
In photoelectric effect the inner shell electron ____ ups &:

A

more
energy
higher
the inner-shell electron
speeds (excites) & leaves the atom

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3
Q

if we were to increase our atomic number of our material, what would happen to photoelectric effect?

A

increased photoelectric absorption (attenuation, more things to interact with)

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4
Q

In Compton interactions what is striking what? photoelectric?

A

incident x-ray strikes outer shell electron; ceases to exist
x-ray photon strikes inner shell electron; ceases to exist

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5
Q

what is Coherent interactions? what are the two types of Coherent interactions? what happens to the incident x-ray path? what type of energy transfer occurs in Coherent?

A

orbital electron reaches a temporary state of excitement; no ionization occurs
Thompson; incident x-ray interacts with orbital electron (outer shell)
Rayleigh; incident x-ray interacts with the entire atom
continues in a new direction
no energy transfer

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6
Q

what do photoelectric & Compton both result in? what is Compton proportionally more likely at?

A

ionization; removal of an electron
high kVp levels; bc absorption decreases at high kVp and Compton interactions stay the same

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7
Q

what are some of the main things that affect attenuation?

A

tissue thickness; every 4cm of tissue =50% beam attenuation, must increase technique 100% to compensate)
tissue atomic number; more to interact with
tissue density (most important); air vs fat vs muscle (least to most dense)

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8
Q

what is mA limited by? what is mAs a measurement of? its considered? and not considered? what is mAs a primary controller of?

A

focal spot size
electron flow in a conductor
an electrical term
a unit of radiation output
intensity/quantity in the remnant beam

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8
Q

what is SOD? SID? OID?

A

source-to-object distance; x-ray tube to object (patient)
source-to-image distance; x-ray tube to IR
object-to-image distance; object (patient) to IR

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9
Q

what does a small increase of 15% do? how much does patient dose increase? doubling the mAs?

A

double the exposure to the IR; increases patient dose by 1/3
doubles the intensity/quantity

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9
Q

what is attenuation? what is the primary contributor? what are the different interactions that cause this?

A

reduction of x-rays reaching the IR; scatter/absorption
photoelectric effect (absorption)
Coherent scatter (absorption)
Compton (scatter & absorption)

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10
Q

what is the best way to reduce motion? how do we measure radiologic time?

A

setting the shortest time while maintaining the same mAs output; shorter time requires more mA
in seconds

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11
Q

what does kVp control in the x-ray beam? mAs?

A

the quality of the x-ray beam; x-ray’s ability to penetrate through tissue
the intensity/quantity of the x-ray beam

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11
Q

what is remnant radiation? how much of the primary beam becomes remnant radiaiton?

A

part of the x-ray beam that has passed through the patient
less than 1%

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11
Q
A
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12
Q

what is pneumbra? do we want this? what is umbra?

A

blurriness on the outer edges of an image; bad, don’t want this
pure shadow

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13
Q

what is elongation? what is foreshortening? what is this considered?

A

object appears longer than it actually is; tube or IR is angled
object appears shorter than usual; part is angled
distortion; misrepresentation of size/shape of object

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14
Q

what two types of distortion are there? how do we calculate mag factor? how can we reduce size distortion/mag factor? how can we reduce shape distortion?

A

shape; foreshortening & elongation
size distortion; object size is misrepresented on x-ray; aka magnification
SID/SOD
reducing OID or increasing SID
properly aligning tube, part, & IR

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14
Q

what is contrast? what can it be referred to as? what can affect contrast? what can we do to manipulate or increase subject contrast? low kvp=? high kvp?

A

the number of brightness levels in an x-ray; different between 2 adjacent brightness levels
gray scale
kVp (low kvp= high contrast), image receptors, computer algorithms (AEC), patient factors (tissue density)
barium & iodine
low kvp=low contrast=long scale; many greys
high kvp=high contrast=short scale; black & whites

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15
Q

what is spatial resolution? what can affect spatial resolution? how do we measure spatial resolution?

A

sharpness of edges around the image; aka detail or decrease penumbra/low blur
motion, focal spot size, distance, patient factors (OID/motion), angulation
line-pair test tool; LP/mm

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16
Q

what is noise? what is SNR? what is the rule about SNR?

A

undesirable image feedback/input that interferes with the ability to visualize the x-ray
signal-to-noise ratio; must always be greater than one
to produce the best quality image noise must be as low as possible and signal as high as possible

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16
Q

how are kVp & volume related when it comes to scatter (noise)?

A

increase volume (decrease collimation) & high kVp increase chances for scatter

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17
Q

what is quantum mottle? what is usually the cause for QM? what is the opposite of QM? what is preferred in DR systems?

A

insufficent number of x-rays reaching the IR
low mAs; also can be low kVp & difficult to penetrate anatomy
scatter; DR doesn’t do well with QM

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18
Q

what is window-leveling & window width? what happens if they increase/decrease? who sets the standards for optimal contrast/brightness?

A

post-processing of image brightness; decreasing window level increase image brightness, increasing window level decreases image brightness
post processing of image contrast; if we increase window width we see more shades of grey, decreased WW more black & whites
the radiologists

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19
what is the collimator? what does increased collimation do to contrast? patient dose?
adjustable lead shutters increases the contrast; by limiting the amount of volume that can create scatter (noise) decreases patient dose
20
what does higher atomic number, tissue density, & part thickness mean for attenuation? what is the order for most dense to least dense tissue?
increased attenuation; more things to interact with bone, muscle, fat, & air
21
what is the PBL? what is the aperture diaphragm? how much can the light/radiation field be off by?
positive beam limitation; automatic collimator, can override to desired size fixed opening between x-ray tube & collimator box; beam limiter
21
what factors are usually behind scatter? what does scatter do to the IR exposure? what happens to scatter at higher kVp levels? what is scatter sometimes referred to as?
large field sizes & increased tissue volume increases IR exposure; creates noise & decreased contrast (all bad) scatter is increased at higher kVp levels secondary radiation
22
what is the number one source of occupational dose? what do grids do?
scatter prevent scatter reaching IR; not production of scatter
22
what affects detail?
focal spot size & penumbra
23
how are grids constructed? how is the effectiveness measured? what is the purpose of grids? what type of grids are there?
alternating lead strips & AL interspace material (plastic sometimes) height of lead strips by the width of interspace material; aka grid ratio restore subject contrast; prevent scatter reaching IR focused grids; follow divergent beam linear; run up & down (angle one way) cross-hatched; up & down + side to side
24
where must grids be used from? how much do modern grid attenuate? how do grids operate? what are the grid ratios?
specific distance from focal spot; convergence spot 70-80% if scattered photons allow primary beam to pass through lead strips & absorb scattered x-rays no grid=1, 5:1=1,6:1=3, 8:1=4, 10:1=5, 12:1=5, 16:1=6
25
what are the factors in which grids should be used? what is the worst type of grid errors?
part thickness above 10cm, kVp greater than 70, & large field sizes upside down; other errors are off-center, off-level, off-focus
26
what are the two types of filtration? what is compensating filtration? what exams are they used on? what is the purpose of beam filtration? what is the legally required filtration?
added; aluminum, sometimes copper inherent; built in, x-ray tube glass, cooling oil, beryllium window filtering that evens out inherently uneven anatomy; c-spine swimmers, x-table shoulder, & x-table hip to reduce patient dose; by elimination the weak/unnecessary x-rays 2.5 mm Al/Eq
26
what is the purpose of generators? what generator type has the effective kVp equal to the set kVp?
generators affect penetration by altering the average energy of created x-rays portables; only generators that are equal
27
how do we measure penetration? how should we adjust our technique for post-mortem in the first 30 mins & after 30 mins?
half-value layers (HVL) increase technique 35% in first 30 mins 50% increase after 30 mins (less air, more fluids)
27
what do we do to technique for the different body types?
hypersthenic; increase kVp (fatty tissue) sthenic; nothing (average) hyposthenic; reduce mAs, thin but healthy asthenic; reduce kVp, sickly or elderly (thin)
27
what is the technique adjustments for fiberglass? plaster casts?
no change to technique increased technique; dry casts double the kVp (15%) wet casts triple the kVp (15 then +15)
28
what is the caliper? what is the rule regarding this?
device to measure part thickness (accurately) is should measure along the centray ray
29
what is the average abdomen thickness for an AP view? Lat?
AP: 22cm; Lat: 30cm
30
what do contrast agents primarily affect? what must we do to technique for contrast agents? what is the technique for iodine, single, & double contrast studies? how do contrast agents appear on x-ray?
image contrast increase our technique to partially penetrate the agent (to be diagnostic) iodine; 80 kVp single; 120 kVp double (barium +air); 90-100 kVp white; easier to see due to high atomic number
31
how much technique increase is required to demonstrate a noticeable change in an x-ray?
35% change
32
what do additive pathologies requiredfor technique? what about destructive pathologies?
increased technique; kVp for bony growth, mAs for soft tissue reduced technique, kVp as penetration is easily obtained
33
what is the typical anode angle? what is the anode heel effect? when is the anode heel effect most noticeable?
15-17 degrees varying x-ray intensity between cathode & anode; anode is the weaker side best for detail & cathode is stronger side large field sizes & short SID's
33
what factors create a small effective focal spot? where is the effective focal spot located? what is the typical size for actual focal spot? effective focal spot sizes?
thin electron beam + small anode bevel angle below actual focal spot small; 1 cm large; 1.5-2cm small; 0.5mm-1mm large; 1-2mm
34
what does focal spot affect? when would we use a large focal spot? when would we use a small focal spot?
spatial resolution (small) & heat capacity (large) for exams with high heat (lumbar) for exams that require high spatial resolution (small)
35
If we increase or mA what happens?
IR exposure increases noise decreases; QM goes down
36
if we increase time what will happen?
IR exposure increases (primary) noise decreases; QM decreases (primary) sharpness decreases; motion goes up
37
if kVp goes up what will happen?
IR exposure increases (primary) subject contrast decreases (primary) noise increases; scatter
38
what will happen if collimation increases?
IR exposure decreases subject contrast increases (primary) noise decreases; scatter (primary)
38
if part thickness goes up what will happen?
IR exposure decreases; more attenuation (primary) subject contrast decreases; more scatter (primary) noise increases; more scatter (primary) sharpness decreases; OID size distortion increases; OID
39
if scatter goes up what will change?
IR exposure increases subject contrast decreases noise increases; scatter
40
if the grid ratio goes up what will happen?
IR exposure decreased; more attenuation in lead strips subject contrast increases; less scatter noise decreases; less scatter
41
if focal spot increase what will happen?
sharpness decreases (primary); large focal spot is good for heat not spatial resolution
42
if SID goes up what will happen?
IR exposure decreases sharpness increases size distortion increases (primary); magnification is reduced
43
if OID goes up what will happen?
IR exposure decreases; air gap subject contrast increases; air gap noise decreases; scatter sharpness decreases (primary) size distortion increases
44
if SOD goes up what will happen?
sharpness increases (primary) size distortion decreases (primary)
45
if motion goes up what will happen?
subject contrast decreases; blur noise increases; blur sharpness decreases
46
if alignment goes up what will happen?
shape distortion decreases (primary)
47
what happens when AEC encounters metal? what density settings are required to see a noticeable change in an x-ray? where is the AEC located? how many ionization chambers consist in AEC systems?
time, motion, patient & IR exposure all increase +2 density setting; 1=25% change (35% needed to see change) between the patient & IR; uses ionization to cut off 3 cells
48
what is modulation transfer function? what is something bad that can happen?
how physicists measure contrast resolution line-pairs become to small to measure and merge and reduce contrast
49
what should the back up time be set to? what is the primary reason for technique charts?
150% of anticipated time to maintain consistency
50
what is Cieszynski's law?
angle 1/2 of the parts angle to minimize distortion (elongation/foreshortening)
51
how can we find the actual object size on an x-ray? how would we find the objects projected size?
divide projected size by the mag factor multiply actual size by the mag factor
52
what is a CPU? RAM? ROM? BIOS? motherboard?
central processing unit; coordinates all computer operations random access memory; accessed quickly & can be override by user, stored on chip/disc read-only memory; can't be changed by user basic input/output system; internal/primary ROM that directs the flow of information between CPU & peripherals houses CPU, RAM, ROM, chips & connections for USB/audio
53
what is LAN? WAN?
local area network; single business/building wide area network; multiple geographic areas
54
what is a bit? what are they used for? how many to create a byte?
small unit for binary numbers 8 bits
55
what is teleradiology?
remote transmission of medical images via telephone wire/fiber cable to radiologist at home/remote
56
what is the smallest unit of a digital image? smaller the pixel? pixel size is limited by what?
pixel the better the spatial resolution DEL detector element size in diagnostic imaging
57
what is the FOV? what is the matrix?
physical area of an image pattern of pixels laid out in rows/columns
58
what is bit depth? what is a bit depth of 5? 8? 10? what is dynamic range?
the maximum pixel values a computer can measure/store 32 shades of gray; how much a human eye can distinguish 256 shades; common for non-medical imaging 1024 shades of gray; number of grays in the remnant beam range of shades of gray that a system can generate
59
what is scanning? sampling? qauntization?
creating a matrix measuring the intensity assigning a value
60
what is the greatest known benefit of DR over CR?
ability to control contrast resolutions
61
what is pre-processing? what does it do? what does post-processing do?
automatic clean up of raw image date to make initial image visible corrections refinements
62
what are the matrix sizes for these modalities? nuclear medicine: US: MR: CT: x-ray: mammography:
64 x 64 128 x 128 512 x 512 512 x 512 1024 x 1024 3328 x 3328; but depth 14 & 27 MB file size
63
what can happen to individual DELs? what is the noise reduction for DEL dropout?
malfunction & return no data compensates for malfunctioning DEL by assigning a value from the surrounding 8 DEL's
64
what is segmentation? where does it primarily occur? what is flat field uniformity? what is exposure field recongition?
computer error that reads multiple images as one; occurs in CR only preprocessing that corrects for electronic/optic flaws in the IR computer error that analyzes raw radiation outside anatomy of interest
65
what is an histogram? how does it visually appeal? what are smax & smin?
bar graph created by measuring the number of pixels at each brightness level dark pixels on the right, white pixels to the left smax are the maximum values used for analysis; smin is the minimum
65
66
what are the different types of histogram analysis?
type 1; detects smax & removes values to the right (raw radiation) type 2; assumes no values to right of smax & assigns a highest value as smax (abdomen) type 3; detects smin & removes values to the left that represent metal or prothesis
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