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CT sim/ Imaging Flashcards

1
Q

cathode is the ____ part of the xray tube

A

negative

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2
Q

abided us ___ part of the xray tube

A

positive

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3
Q

what are the portions of the cathode

A

filament and focusing cup

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4
Q

what is filament made of

A

its a small coil of tungseten wire with a high melting point

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5
Q

focusing cup

A

the - charge of thr focusing cup can help direct e towsrds the anode in a or linear path

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6
Q

do e go from anode to cathode or cathode to anode

A

cathode to anode (- to +)

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7
Q

what are the prts of the anode

A

line focus principle, composition and target

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8
Q

the target in the anods is aka

A

focal spot

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9
Q

i am the part of the CT where photons start to fan out in a divergent path

A

the target of the anode

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10
Q

what is done to overcome extra heat production of a small focal spot

A

the line focus principle- the target is angled at 7-20 degrees to account for extra heat

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11
Q

anode, cathode, filament, focusing cup, target are components of what machine

A

CT sim

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12
Q

as FQ + wavelength _

A

-

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13
Q

as wavelength + FQ_

A

-

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14
Q

the principal interaction in xray production

A

bREMSTRAHLUNG

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15
Q

The ideal material for a target of an xray tube is what?

A

something with high atomic #

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16
Q

mA vs Kvp

A

mA is th tube current

Kvp is th e tube voltage

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17
Q

predominant interaction in the therapeutic range, is this good or bad?

A

predominant interaction is compton scattering, this is bad because scattering is not good

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18
Q

what is the only acceptable interaction to create images

A

photoelectric effect

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19
Q

an incident photon penetrates deep into the atom and ejects an inner shell electron. This process is known as…?

A

photoelectric effect

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20
Q

an xray photon interacts with an outer shell orbital electron. This process is known as….?

A

compton scattering

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21
Q

there is a change in photon direction but does not eject an electron. this is known as?

A

unmodified/ thompsons/ cohernt scattering

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22
Q

photoelectric effect is dependant on what

A

higher z material, the higher the z the more likely it is to be absorbed by photoelectric effect

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23
Q

the relationship between distance and density

A

ISL

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24
Q

What does density in imaging refer to

A

how light or dark an image is

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25
the higher the mA the ____ the density
higher
26
optimal contrast depnds on whay?
Kvp
27
computed radiography uses ______ to convert xrays to digital images
photostimable plates
28
primary method of - scatter
colimating the beam
29
who would cause more scatter, small pts or larger patients
large patients
30
what area would cause more scatter: abdomen or pelvis?
pelvis as there is more bone in the pelvis (bone causes more scatter, high Z) abdomen has more soft tissue therefore less scatter
31
predominant interaction in imaging? kv imaging?
kv- photoelectric effect | mv-compton scatter
32
which has lower dose to pt? Kv or Mv?
Kv is 100 X less dose than Mv
33
T1 vs T2 on MRI
T1- longitudinal relaxation time | t2-Transverse relaxation time
34
MRI uses_____`
pulse sequences
35
FDG is a _____EMITTER
POSITON
36
What is used to create US waves
piezoelectrical crystal
37
how many detectors are /cm and per degree
1-8 detectors/ cm or 1-5 detecros / degree
38
what do solid state detectors do?
convert radiation to light
39
what is pitch
the distance that the couch travels through the xray rotation
40
a higher pitch can cause what?
+ artifacts
41
whats foltered back projection
an algoritihm used to reconstruct CT image aka convolution method
42
what image reconstruction is mostly used now
IR iterative reconstruction
43
what is the pros of IR over FBP
FBP can have significant artifacts and noise, IR corrects for this
44
CT +1000 is....
dense bone
45
CT # 0 is.....
water
46
CT # -1000 is....
air
47
what is the typical matrix size in CT scan?
512 x 512
48
voxel is determined by what 3 things?
slice thickness, matrix size and FOV
49
PIXEL VS VOXEL
picture element vs volume elemnt | n.b. the pixel is 2 d and vixel is 3d
50
what is isotropic display
this is when all planes of the voxel are = ( therefore equal width, length and depth)
51
if after imaging you would like to see improved contrast of the image what would you adjust?
window width
52
if i want to view the lung better what would I adjust?
the window width, in lung the WW # is typically 500
53
what is tthe effect of a wide WW
- contrast
54
what is the effect of a narrow WW
+conrast
55
if I want to - noise of the image what should i do to the mA? kVp?
+ kVP and - mA
56
to improve tube longevity what kind of mA should you use
LOW if pissible
57
a ring artifact is an indication of what
detector malfunction
58
a star artifact is an indication of what
metal in the field
59
what causes partial volume artifacts
when thick slices are taken
60
what can be used to - motion artifacts
using fast scanners
61
``` a multislice CT systen uses what? A: multiple detector beams b: multi slice beams c: multiple detctor rows d: multi-slice rows e: multiple corn rows ```
E LOL | C is correct answer
62
what is the pro of placing pt prone in pelvis tx
it - sm bowel in the field threfore - SE
63
What is diazorate melgulieum
this is an oral contrast agent that is aqueous
64
when is aqueous oral contrast used
for patients at risk of GI prforation (ex: UC, diverticulitis) where its dangerous for them to have barium sulfate
65
contraindications to IV contrast
pt >50 pt with diabetes pts with impaired kidney fn or cardiovascular disease or a reaction to contrast in the past
66
what needs to be done before IV contrast
bloodwork that looks at EGFR (estimated glomoular filtration rate) ad creatinie levels
67
what EGFR rate is PROBLEM, what happens in this case?
EGFR <60 | in this instance the patient will have areduced amount of contrast or will not have contrast at all
68
IV contrast 2 types
inonic iodine and nonionic contrast
69
ionic iodine has ____ osmoality
high
70
what is osmoality
particles in solution / kg of water
71
what can high osmoality contrast cause
decreased blood pressure
72
what happens in dehydrated pts if they receive high osmoality contrast, what are these patients given?>
can cause pt to go into shock | these pts are given low osmoality contrast ex nonionic contrast instead
73
what steps do you take when pt has mild reaction to contrast media
- the injection continues - reassure the pt - monitor the pt to ensure rection does NOT progress - ensure the reaction subsides
74
what steps do you take when pt has intermediate reaction to contrast media
stop the injection- pt requires careful observation to ensure a severe rection does not occur
75
what steps do you take when pt has severe reaction to contrast media
stop injection, prompt medical attention is required, pt is often hospitalized
76
when do most reactions occur from contrast media
70% occur within first 5 mins the rest occurs within half an hour
77
what subsites need to fast prior to SIM
H&N, lung, brain and PROS
78
when is contrast admin in H&N and lung
seconds before the scan via power injector
79
when is contrast admin for brain
10-30 mins before CT via IV push
80
when to admin contrast for liver
20-40 seconds before scan to visualise hepatic artery, 60-90s to view portal vein
81
when to admin contrast for pelvis
not all pros patients get contrast- if administered: 15 mins before CT IV injection Barium can b given orally 30-60 mins before scan to visualize sm bowel
82
when to admin contrast for GI
Oral contrast is used: | baroum is taken orally 30-60 mins before scan
83
what sites get IV contrast
lung, H&N, brain, liver, sometimes PROS
84
contrast media needs _____ in order to -______
needs to have low atomic # to - artifacts
85
when the scanner is triggered to aquire images/ treat during a certain part of respiration, this is called _____
prospective axial scanning
86
with PET scanning _____ is used to create the image A: KV XRAYS B: 511 kev gamma rays that move in almost opposite directions C: 6MV gamma rays D: Magnetic pulses
B
87
mA is the ____ of the beamand controls ______. | kVp is the ______ of the beam and controls ______.
mA is the quantity of th beam and controls density | kVp is the quality of the beam and controls contrast
88
VMAT is best used for what type iof tumours ?
central, well defined tumours | Ex: central lung cancer or prostate

Skin Radiation therapy (40 decks)

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