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Imaging Review CCPM > NUC MED > Flashcards

NUC MED Flashcards

1
Q

counts/pixel in SPECT and PET

A

100 counts/pixel in SPECT
1000/pixel in PET
1000 photons/mm2 is reasonable

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2
Q

secular equilibrium

A

long lived parent
parent and daugther activities meet to be equal

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3
Q

transient equilibrium

A

parent is short lived but still longer half life than daughter
-activities only proportional to each other

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4
Q

when does transient or secular equilibrium occur?

A

after 4 daughter half lives

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5
Q

electron capture nuclides in Nuc Med

A

67 Ga, III In, 123I

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6
Q

regulatory limit for 99Mo breathrough

A

5.5 kBq Mo/37 MBq 99mTc

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7
Q

nuc med matrix size

A

128x128, 1 byte/pixel, 1/64 MB

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8
Q

what products are carrier free?

A

neutron activation products are not carrier free. Cyclotron and fission products are

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9
Q

number of LORs in PET

A

n(n-1)
n is number of detectors

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10
Q

gamma camera system sensitivity

A

105 counts/MBq

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11
Q

PET spatial resolution

A

3 mm FWHM

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12
Q

SPECT spatial resolution

A

8 mm FWHM

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13
Q

PET effective dose

A

8 mSv

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14
Q

PET scan time

A

2-3 min at each detector position
uses 5 positions to cover body

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15
Q

system spatial resolution

A

square root of (intrinsic res. ^2 + collimator res. ^2)
collimator res is limiting

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16
Q

99mTc effective dose

A

4 mSv

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17
Q

for what organs is nuc med dose high?

A

thyroid, spleen, gallbladder, liver

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18
Q

PET administered 18F activity

A

600 MBq

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19
Q

scan time of SPECT

A

60-120 images

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20
Q

radionuclides used for therapy

A

P32
Sr89
Y90
I131

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21
Q

what causes ring artifact in SPECT

A

non-uniformity

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22
Q

energy windows for gamma cameras

A

-low energy counts = compton
-mi energy is from backscatter out of detector or patient
-max scatter is from backscatter in detector
-multiple scattered photons have low E

remember backscatter IN detector = max

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23
Q

when is NRC notified wrt uninetended dose

A

uninetended radiation exceeds 50 mSv or 500 mGy to an organ

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24
Q

typical nuc med activity administered to patient

A

22 mCi or 700 MBq

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25
Q

isomeric transition

A

gamma rays emitted

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26
Q

isobar

A

nuclides with same mass number

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27
Q

geometric efficiency for single hole collimator

A

1/b^2
b is distance from source to collimator

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28
Q

what has low acoustic impedance

A

air and lung
-low density and low sound velocity

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29
Q

what does reflection/transmission depend on?

A

differences in acoustic impedance

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30
Q

what are sound waves formed from

A

electrical energy converted into mechanical energy

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31
Q

impedance formula

A

Z (Rayls) = density * sound velocity

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32
Q

compressibility vs sound velocity

A

high compressability (ie bone) = high sound velocity

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33
Q

thickness of matching later

A

1/4 wavelength of sound in that material

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34
Q

velocity of sound in air

A

343 m/s

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35
Q

US to kill tissue?

A

high intensity US kills through ablation

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36
Q

US frequency range

A

> 20 kHz
1-20 MHz used in clinic

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37
Q

when does scattering occur

A

when US encounters objects that are smaller than US wavelength

38
Q

what does US wavelength depend on

A

material compressability

39
Q

velocity of sound in tissue

A

1540 m/s

40
Q

axial resolution

A

1/2 the pulse length
typically = wavelenght

41
Q

specular reflection

A

from large smooth surface

42
Q

non-specular reflection

A

from rough surface
doesn’t contribute to image

43
Q

attenuation rate

A

0.5 dB/cm/MHz
fluids have low attenuation
lung and bone have high attenuation

44
Q

refraction

A

f stay sams, lamba and v change per Snell’s law,
v1/v2=sin theta1/sintheta2

45
Q

material of transducer

A

PZT

46
Q

impedance of transducer

A

intermediate between transducer and tissue
square root (ZtransZtiss)

47
Q

trade-off between high and low frequency

A

low frequency = better penetration
high frequency= better axial resolution

48
Q

dB

A

10% is 10 dB, 1% is 20dB, 0.1% is -30 dB

49
Q

bladder and cysts in US

A

appear as black
have almost no scatter

50
Q

width and height of individual elements in array

A

width = lambda/2
height = a few mm

51
Q

transducer crystal thickness

A

lambda/2

52
Q

issue with side lobes

A

yields artifacts

Side lobe artifact occurs when the beam of an off-axis side lobe encounters a structure and returns this off-axis object as coming from the main beam. This creates a duplicate structure on the screen but in a different area.

53
Q

what organs have many scattering sites

A

-kidney, pancreas, spleen, liver

54
Q

focal depth

A

pt at which beam is at its narrowest

55
Q

range of frquency of audible sound

A

15 Hz - 20 kHz

56
Q

how to produce short pulses

A

use blocks of damping material

57
Q

focal zone

A

near field
region where US is narrow
-don’t use far zone for imaging

58
Q

is pulsed or continuous US used in clinic

A

pulsed

59
Q

size of PZT

A

<lambda/2 in width and a few mm high

60
Q

what does Doppler US measure

A

change in frequency
not velocity

61
Q

reverbation

A

large number of reflected waves, which can be perceived as continuous sound

62
Q

US contrast agents

A

microbubbles

63
Q

how to improve lateral resolution

A

reduce frame rate
-this also reduces temporal resolution

increase pulse repetition frequency to increase line density
-this reduces listening interval and thus reduces imaging depth

64
Q

pulse repetition frequency to avoid aliasing

A

PRF> 2 X highest doppler delta f

65
Q

how to improve axial resolution

A

increase transducer frequency to reduce pulse length

66
Q

power doppler

A

more sensitive than regular doppler
-shows only magnitude, not direction

67
Q

show US artifacts in image

A
68
Q

US artifacts in image

A
69
Q

US artifacts in image

A
70
Q

Anger camera max non-uniformity

A

5%

71
Q

intrinsic vs extrinsic

A

intrinsic looks at imager part only
extrinsic looks at total image, realistic conditions

72
Q

parrallel hole collimator resolution

A

degraded with increasing distance from collimator

73
Q

what scintillator is in Anger camera

A

NaI

74
Q

how many counts in Anger camera

A

500,000

75
Q

intrinsic resolution of anger camera

A

3-5 mm

76
Q

formula for system resolution

A

square root (intrinsic res^2+ colli res^2)
colli is limiting

77
Q

types of SPECT collimators

A

-parrallel hole (constant FOV)
-converging (magnified, FOV~ 1/distance)
-diverging (FOV increases with distance)
-pinhole (magnify and inver)

78
Q

isotope vs isotone

A

isotoPe= same number of protons
isotoNe= same number of neutrons

79
Q

how far does an alpha particle travel

A

<0.1 mm

80
Q

thickness of PET detector

A

20-30 mm thick to efficiently detect 0.511 MeV photons

81
Q

how much more sensitive is 3D PET vs 2D PET?

A

3D PET is 6x more sensitive than 2D PET

82
Q

Equation for cumulative activity

A

1.44Aot1/2

83
Q

S factor

A

absorbed dose in target organ/ unit cumulative activity in source organ
S increases as the size of the organ decreases

84
Q

MIRD

A

medical internal radiation dose
-framework for assessing absorbed dose to organs, tissue, etc

85
Q

99Mo breakthrough limit

A

5.5 kBq 99Mo per 37 MBq Tc 99m
-when you give it to the patient. Have to account for decay- 99Mo decays a lot slower than 99Tc so you would have to be below this limit at time of elution to be within the limit at time of treatment

86
Q

ALI

A

annual limit on intake
-activity of radionuclide that will deliver effective dose of 20 mSv during 50 yrs after radionuclide taken in by someone over 20 yo or for period starting at intake and ending at 70 for someone < 18

87
Q

does resolution degrade with depth in SPECT?

A

yes
holes see more photons

88
Q

equation for nuc med integral uniformity

A

100%*(max counts - min counts)/(max counts + min counts)

89
Q

What does theranostic mean

A

rad nuclide used for therapy and diangostics

90
Q

what does Ae^-1t + Be^-bt look like on a semi-log plot

A

2 straight line segments

91
Q

efficiency of counting system

A

(Cradionuclide- Cbackground)/Aradionuclode *100%

Imaging Review CCPM (11 decks)

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