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PET Study Guide > chapter 5: ct instrumentation > Flashcards

chapter 5: ct instrumentation Flashcards

1
Q

what is the type of radiation used to produce diagnostic xrays?

pair production
compton scattering
characteristic xrays
bremsstrahlung “breaking” radiation

A

bremsstrahlung “breaking” radiation

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2
Q

what is it called when an atom in the target of the xray tube has been ionized, the inner shell electron is removed, so an outer shell electron drops down to fill this vacancy?

bremsstrahlung radiation
pair production
compton scattering
characteristic xrays

A

characteristic xrays

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3
Q

the kVp controls

the number of xrays produced
the shape of the xray beam
the energy of the xrays
the type of xrays produced

A

the energy of the xrays

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4
Q

the mAs controls

the number of xrays produced
the shape of the xray beam
the energy of the xrays
the type of xrays produced

A

the number of xrays produced

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5
Q

define the equation for pitch

A

pitch = table movement in one rotation/single-slice thickness

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6
Q

define the partial volume effect

A

occurs when there is a mixture of tissues within a voxel, so the measurement within that voxel will be inaccurate. typically occurs with small lesions

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7
Q

define the equation for the CT number

A

CT number = (u tissue - u water)/ u water x 1,000

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8
Q

what are the CT numbers for air, fat, water, muscle, blood, soft tissue, and bone?

A

-1,000
-100 to -50
0
35-80
20-80
20-80
400-1,000

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9
Q

define the truncation artifact

A

occurs when the CT is reconstructed with a smaller fov than the PET scan. PET quantitative measurements may be altered at the edge of the scan

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10
Q

what causes a ring artifact on a CT scan?

A

when the mAs are too low (30 mAs), resulting in low data density

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11
Q

postcollimators on a ct scanner are located in front of, or behind the x ray detectors?

A

in front of

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12
Q

T/F: the typical slice range of ct scanners used for oncologic pet/ct is 16 to 40 slices

A

true

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13
Q

good low-contrast resolution is obtained by increasing the…

kvp
scan time
mAs
xray energy

A

mAs

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14
Q

when an electron undergoes a bremsstrahlung reaction, its energy is

preserved
lost
gained
stays the same

A

lost

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15
Q

the energy of the characteristic xray is based on

the number of electrons in the vicinity
the energy

the energy of the bremsstrahlung radiation

the total number of ionizations

type of target material that has been ionized

A

type of target material that has been ionized

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16
Q

on the bremsstrahlung xray spectrum, as energy increases, the number of xrays

increases
decreases
stays the same
is preserved

A

decreases

17
Q

as more or less current and voltage are applied to the xray tube, tungsten characteristic xray energy

increases with more current/voltage
decreases with less current/voltage
does not change
is preserved

A

does not change

18
Q

the purpose of the xray tube filter is to

shape the xray beam
filter out low energy xrays
A and B
none of the above

A

A and B

19
Q

all of the following are true concerning thin collimation for ct xray tubes except

more volume averaging
better spatial resolution
increase in quantum noise
reduction in streak artifacts

A

more volume averaging

20
Q

all of the following are materials that may be used to produce xrays in the ct xray tube except

germanium
silicon
tungsten
cadmium

A

tungsten

21
Q

in MDCT or MSCT, what defines the number of slices that can be created at the same time?

x axis
y axis
z axis
A and B

A

z axis

22
Q

all of the following are considered the 4 Cs of helical CT except

continuous feed of the bed
continuous rotation of the gantry
continuous data reconstruction
continuous data transfer

A

continuous data reconstruction

23
Q

generation of high res/high-contrast res for inner ear or eye orbits, or low-res with smoothing properties for the abdomen is called

image recon algorithms
kernel
filtering
chang technique

A

kernel

24
Q

a ct for attenuation correction for use with pet must be a

high res scan
low res scan
high res scan with smoothing
low res scan with smoothing

A

low res scan with smoothing

25
Q

most body tissues have ct numbers that are close to that of

air
water
soft tissue
blood

A

blood

26
Q

a concentric ring artifact may be caused by

patient motion
beam hardening
mA setting is too low
kvp is too low

A

mA setting is too low; low data density as a result

27
Q

the CTDI is measured in

mGy
mSv
KBq
MBq

A

mGy

28
Q

DLP stands for

dose length procedure
dose length protection
dose length product
dose length probability

A

dose length product

29
Q

all of the following are true for accurate calculation of DLP except

it is measured in mGy
scan lengths must be equivalent
it is inversely related to scan length
it is an estimate of absorbed dose

A

it is inversely related to scan length

30
Q

the highest fraction of patient radiation exposure comes from

fdg pet scans
chest xrays
ct scans
rb82 rest/stress studies

A

ct scans

31
Q

all of the following will reduce the radiation exposure to the patient except

lowering mAs
lowering kvp
using a smaller pitch
decreasing scan time

A

using a smaller pitch

32
Q

AEC techniques

are the same across all scanner manufacturers and scanners

may reduce patient exposure by approximately 75%

substantially benefits smaller patients

primarily adjusts the kvp

A

substantially benefits smaller patients

33
Q

AEC is adjusted based on

size of the patient
density of the patient
age of the patient
A and B

A

A and B

34
Q

the standard deviation of pixel values in a uniform water phantom describes the

standard deviation coefficient
pixel parallax
noise index
houndsfield deviation

A

noise index

35
Q

all protocols established for the ct scanner should be reviewed and approved by the

field engineer and physician
ct physicist and physician
ct physicist and field engineer
ct physicist and state licensing agencies

A

ct physicist and physician

36
Q

ring artifacts on a ct scan from a failed detector

will be seen on all slices
can be caused by a failed air scan
always requires a service call
causes an artificially high reading

A

can be caused by a failed air scan

PET Study Guide (19 decks)

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