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term test 2 imaging > term test 2 imaging > Flashcards

term test 2 imaging Flashcards

1
Q

what does PET stand for

A

positron emission tomography

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2
Q

what are the standard measures for image quality in PET

A
  • spatial resolution
  • sensitivity / contrast
    = noise
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3
Q

what are the units of FDG

A
  • KBQ / mL
  • SUVs
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4
Q

what is SUV ?

A
  • standardized uptake value
  • tracer in tissue (Bq/ml) / inj. dose (Bq) / weight (g)
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5
Q

what are the applications of PET in radiation oncology

A
  • staging
  • treatment planning / tumour targeting
  • monitoring treatment response
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6
Q

how is PET-CT used in treatment planning / tumour targeting

A
  • tumour delineation
  • planning target volume
  • research
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7
Q

what does RECIST stand for (structural)

A

response
evaluation
criteria
in
solid
tumours

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8
Q

what does EROTIC stand for (functional)

A

European Organization for Research and Treatment of Cancer

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9
Q

what does PERECIST stand for

A

Positron Emission Reponse Criteria In Solid Tumours

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10
Q

what is complete response

A

complete resolution of FDG uptake within tumour volume

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11
Q

what is Partial response

A

reduction of a minimum of 15-25% in tumour SUV

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12
Q

what is stable disease

A

increase in SUV less than 25% or a decrease of less than 15%

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13
Q

what is progressive disease

A

increase of SUV more than 25% or a decreawse of less than 15%

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14
Q

what is the definition of sonography

A

use of reflected sound waves to describe the position and shape of an object

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15
Q

what is the definition of ultrasonography

A

= sonography that uses sound waves that are above the frequency that is audible to humans

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16
Q

how are ultrasounds made

A
  • transducer made of peizoelectrical crystal
  • so is the scanhead where echos are recieved
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17
Q

what frequency waves can thinner and thicker crystals make

A

thinner: higher frequency waves (5-10MHz)
thicker: lower frequency waves ) 2-3.5 Mhz

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18
Q

what is the difference in resolution and penetration in thinner and thicker piezoelectric crystals

A

thinner: greater resolution but less penetration
thicker: lower resolution but better penetration

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19
Q

how are images produced in ultrasounds (brightness of dots and location of dots)

A
  • brightness: proportional to the strengths of echos returning from there
  • location: due to the transit time of the sound waves
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20
Q

what is the constant velocity for recon

A

1540m/s

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21
Q

how do structures show up in ultrasound images

A

due to differences in acoustic impedance between different tissues

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22
Q

what is acoustic impedance

A

the product of a tissues density and propagation velocity

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23
Q

what happens at boundaries between tissues with acoustic impedance

A

sound is reflected back

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24
Q

what determines return echo

A
  • reflection (specular or diffuse)
  • refraction (u/s assumes return echo is a straight line, scan perpendicular to surface)
  • tranmission
  • attenuation
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25
Q

what is echogenicity

A
  • amount of energy reflected back from tissue interface
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26
Q

what are the three types of echogenicity

A

hyperechoic (greatest intensity, white)
hypoechoic (intermediate, grey)
anechoic (no reflection , black)
isoechoic (same intensity)

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27
Q

what structures are hyperechoic

A
  • diaphragm, tendons, bones
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28
Q

what structures are hypoechoic

A
  • most solid organs, thick fluids
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29
Q

what structures are anechoic

A
  • fluids in cyst, urine, blood
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30
Q

what are the types of positive agents

A

barium
iodine

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31
Q

what are the types of negative agents

A

air
carbon dioxide

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32
Q

what is the difference between ionic and non ionic compounds

A

ionic compounds dissociates in water
non ionic - covalently bounded compound

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33
Q

what is the osmolality of blood

A

280 - 300 mOs/kg

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34
Q

fill in blanks
____ agents typically have higher osmolaity
high osmoality agents have higher risk of ______

A

ionic

adverse evetns

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35
Q

what are some examples of IV ionic contrast agents

A
  • hypaque
  • isopaque
  • hexabrix
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36
Q

what are some examples of IV NON ionic contrast agents

A

ultravist, omnipaque, visipaque note: all except visi have higher osmo than blood

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37
Q

what contrasts are taken orally

A

barium iodine water

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38
Q

what contrasts are taken rectally

A

water, barium, iodine, air, CO2,

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39
Q

what contrasts are taken intravenous or intra arterial

A

iodine

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40
Q

what contrasts are taken intrathecally

A

iodine

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41
Q

which vein do we inject contrast into

A

cubital fossa, cephalic vein

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42
Q

what are the 4 general phases of AVID

A
  • pre contrast
  • bolus phase (arterial phase)
  • non equilibrium phase (venous phase)
  • equilibrium phase (delayed phase)
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43
Q

what does AVID stand for

A

arteriovenous iodine difference

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44
Q

what phases are compared

A

HU taken within aorta measurement taken within IVC

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45
Q

the bolus phase immediately follows the _________
it is characterized by attenuation differences of ________ or more HU between ____ and _____.
can see _____ filled. also
known as _____ phase

A
  • IV bolus injection
  • 30
  • aorta and IVC
  • arterial vessels
  • arterial phase
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46
Q

how long after the injection does the non equilibrium venous phase begin ? how long does it last

A

1 minute for both

47
Q

what is the HU difference in the non equilibrium / venous phase

A

10 - 30

48
Q

which phase is good at looking at liver lesions

A

venous phase

49
Q

when does the equilibrium delayed phase occur

A
  • 2 minutes after bolus
50
Q

what is the HU difference in the equilibrium / delayed phase

A

< 10 HU

51
Q

which phase is the worst to look at structures

A
  • equilibrium delayed phase
52
Q

what do time density curves predict

A
  • contrast media dose
  • injection flow rate
  • scan delay
  • scan duration
53
Q

what are the premedications for patients with a high risk reaction

A

prednisone : 50mg po 13 hours and 1 hour before
benadryl: 50mg 1 hour prior

54
Q

What do the following drugs do
Chlorpheniramine (Chlor-Tripolon)
* Diphenhydramine (Benadryl) -
* Diazepam (Valium) –
* Epinephrine (Adrenalin)
IV adrenalin
* Hydrocortisone (Solu Corlef)
* Salbutamol (Ventolin)
* Phentolamine (Rogatine)
* Sodium Chloride 0.9%

A
  • antihistamine vial/pill
  • antihistamine vial
  • controls convulsions
    – for anaphylaxis
    – rapid increase in BP, stimulates heart, increases HR,
    relaxes smooth muscle to alleviate bronchospasm/asthma attack
  • acute allergic anaphylactic rxns
    – bronchial dilator
    – vasodilator
  • keep veins open
55
Q

for the site, name
site: rectum / anal canal
see:
type
delay

A
  • lower small bowel
  • telebrix and water
  • 1 hour prior
56
Q

for the site, name
site: esophagus
see:
type
delay

A

GE stomach
telebrix and water
just after scout

57
Q

for the site, name
site: pancreas liver cholangio
see:
type
delay

A

duodenum
telebrix and water
20 minutes prior

58
Q

for the site, name
site: upper GI
see:
type
delay

A

lower small bowel
telebrix and water
1 hour prior

59
Q

for the site, name
site: Lower GI
see:
type
delay

A

lower small bowel
telebrix and water
1 hour prior

60
Q

what does x ray image quality depend on

A
  • x ray source (energy, spot size)
  • SSD
    patient thickness and the part to be imaged
    detector to patient distance (Airgap_
    amount of exposure or dose
    quality of detector
61
Q

what are the advantages of portal films

A
  • high resolution
  • fair contrast
  • low maintenance and set up costs
62
Q

what are the disadvantages of portal films

A

time consuming
high cost per film
not online or digital

63
Q

what are the advantages of EPIDs

A
  • fair resolution
  • images at any angle
  • fast efficient
  • online digital
64
Q

what are the disadvantages of portal films

A
  • poor contrast
  • high cost
  • image database maintenance
  • image quality operator dependant
65
Q

what are the advantages of flat panel technology

A
  • much better image quality
  • excellent spatial resolution
  • online digital
    -transit dose measurements
66
Q

what are the disadvantages of flat panel technology

A
  • limited to bony or fiducial markers
  • 2D information only
  • image quality can be poor
67
Q

limitations to flat panel detectors

A
  • lower efficiency (lower x ray cross section)
  • higher noise characteristcis
  • slower readout per frame
    signal memory (lag or ghosting)
68
Q

describe each for linac acquisition
frames / s
min / rotation
projections
exposures

A

5
2
600
120 kVp, 100mA, 10-20ms

69
Q

describe the process to project data

A

300 projections
gain anad offset
exposure normalization
pixel defect correction

70
Q

what are sources of image artifacts

A
  • truncation (detector FOC)
    motion artifacts
    metal artifacts
    scatter
    lag/ghosting
71
Q

what does the bowtie filter do in CBCTs

A
  • compensate for anticipates thickness of patient along beam length to achieve a fluence of photons that is uniform
  • filters our lower energy photons at periphery
72
Q

in varians a full fan is a _____ bowtie filter
and a half fan is a ____ bowtie filter

A

half and full

73
Q

what is Precession in relation to MRIs and hydrogen

A

axial spin of the H proton
independent of the alignment of axis of the atom
the wobble of the axial spin of the H proton

74
Q

how is precessional frequency determined

A
  • type of atom and is the magnetic field strength
75
Q

what is the rate of precession determined by

A

magnetic field

76
Q

what do gradient coils do

A

superimpose magnetic fields over the main magnetic field to create a gradient of magnetic field strength down the bore of the machine
- how the location of signal is determined

77
Q

what is the energy exchange between two systems called

A

resonance

78
Q

how is the slice selection and data origin location determined

A

RF pulse

79
Q

what is the T1 and T2 stage

A

T1: recovery of net magnetization
t2: spin spin relaxation
- loss of phase coherence

80
Q

what is time of echo

A
  • time from RF pulse and the time where we measure the signal of the lateral magnetization
81
Q

what is time of repetition

A

-time between one pulse and another
can be used to see which tissues are losing and gaining their perpendicular magnetization faster

82
Q

how do you increase slice thickness on MRI

A

increase bandwidth of the RF pulse
decrease the gradient of the main magnetic field
move patient slower

83
Q

how does shadowing occur

A

(ultrasound)
due to a dense object attenuating most of the sound energy leaving little to travel beyond this creating a shadow, can be used diagnostically

84
Q

how are most signals located in MRI (plane)

A

cartesian

85
Q

what are the 3 dose metrics and how are they calculated

A
  1. CTDI (computed tomography dose)
  2. DLP ( dose length product)
  3. effective dose ED
86
Q

what are some factors affecting dose in CT

A
  • intensity
  • noise
  • spatial resolution
  • slice thickness
87
Q

how does edge shadowing occur

A

(ultrasound)-
sound refracting at tissue boundaries

88
Q

how does the enhancing artifact occur

A

(ultrasound)-
sound does through a structure that does not attenuate well
- fluid filled
- reflections of the other side of the object are enhanced

89
Q

how does the duplication artifact occur

A

(ultrasound)-
due to refraction
- system assumes reflections come back along line of transmitted sound waves at constant speed
- refraction at the boundary therefore makes a false duplicate of the real structure

90
Q

how does the mirroring artifact occur

A

(ultrasound)-
pulse can properly reflect off an object in front of a reflective boundary (diaphragm)
- pulse can transmit through object and reflect off boundary again properly displaying boundary on image

91
Q

how does the reverbation artifact occur

A

(ultrasound)
result of a strong reflector
sound waves bounce off the reflector properly placing it in space
- creates lines on the other side of the strong reflector

92
Q

how does the ring down/ comet tail artifact occur

A

(ultrasound)
similar to reverberation artifact
- ring down can be caused by fluid wedged between microbubbles and that results in reverberations
- comet tail can be caused by two small but strong reflectors close to each other that result in reverberations

93
Q

how does the ring side lobe or grating artifact occur

A

(ultrasound) energy directed outside the field of view reflects and the system incorrectly indicates that a stricture is there in the FOV when it isnt

94
Q
A
95
Q

how does a speed artifact occur

A

(ultrasound)
object in path slows down sound waves

96
Q

how does a ambiguity artifact occur

A

(ultrasound)
- closer than it seems

97
Q

how does a chemical shift artifact occur

A

MRI
frequency encoding gets messed up where fat would be and moved to the left

98
Q

how does an aliasing artifact occur

A
  • also known as a wrap around
  • frequent
  • FOV is smaller than what is being imaged
  • due to misrepresentation in frequency and phase coding
99
Q

3 main types of CT artifacts

A

streak
shading
ring

100
Q

how do streak artifacts occur

A

CT
- improper sampling of data
- beam hardening
- metal
- noise
- partial volume averaging
- patient motion
- spiral helical scanning
- mechanical failure

101
Q

how do shading artifacts occur

A

CT
partial volume averaging
beam hardening
patient motion
spiral helical scanning
scatter radiation
off focal radiation
incomplete projections

102
Q

how do ring artifacts occur

A

bad detector channels in 3rd generation CTs
when detector is not calibrated

103
Q

what are the origins of artifacts categories

A
  • physics based
  • patient based
  • scanner based
  • helical and multisection
104
Q

what are examples of physics based artifacts

A

beam hardening
partial volume
photon starvation
undersampling

105
Q

how does a cupping artifact occur

A
  • from beam hardening
106
Q

what are examples of patient based artifacts

A

metallic materials
patient motions
incomplete patient projections

107
Q

what are examples of helical and multisection CT artifacts

A

helical artifacts in the axial plane : single section scanning
helical artifacts in the multisection scanning
cone beam effect

108
Q

what are examples of multiplanar and 3D reformation artifacts

A

stair step artifact
zebra artifact

109
Q

what should typical scanners be able to display
spatial resolution
contrast resolution
uniformity
linearity

A

0.3mm
0.5% for a 5mm object
deviation of less than 8CT numbers (SD)
coefficient of correlation of 0.96%

110
Q

what is noise / quantum mottle artifact

A

PET CT artifact
- not enough time to overcome the signal to noise

111
Q

what is respiration artifact

A

PET CT
white band due to misalignment between breath hold CT and breathing PET with its relatively long acquisition time

112
Q

what is injection site artifact

A

stems from extravasation of injected PET tracers

113
Q

what is a truncation artifact

A
  • when PET FOV does not match CT FOV

term test 2 imaging (3 decks)

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