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Imaging Review CCPM > NUC MED > Flashcards

NUC MED Flashcards

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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
isomeric transition
gamma rays emitted
26
isobar
nuclides with same mass number
27
geometric efficiency for single hole collimator
1/b^2 b is distance from source to collimator
28
what has low acoustic impedance
air and lung -low density and low sound velocity
29
what does reflection/transmission depend on?
differences in acoustic impedance
30
what are sound waves formed from
electrical energy converted into mechanical energy
31
impedance formula
Z (Rayls) = density * sound velocity
32
compressibility vs sound velocity
high compressability (ie bone) = high sound velocity
33
thickness of matching later
1/4 wavelength of sound in that material
34
velocity of sound in air
343 m/s
35
US to kill tissue?
high intensity US kills through ablation
36
US frequency range
> 20 kHz 1-20 MHz used in clinic
37
when does scattering occur
when US encounters objects that are smaller than US wavelength
38
what does US wavelength depend on
material compressability
39
velocity of sound in tissue
1540 m/s
40
axial resolution
1/2 the pulse length typically = wavelenght
41
specular reflection
from large smooth surface
42
non-specular reflection
from rough surface doesn't contribute to image
43
attenuation rate
0.5 dB/cm/MHz fluids have low attenuation lung and bone have high attenuation
44
refraction
f stay sams, lamba and v change per Snell's law, v1/v2=sin theta1/sintheta2
45
material of transducer
PZT
46
impedance of transducer
intermediate between transducer and tissue square root (ZtransZtiss)
47
trade-off between high and low frequency
low frequency = better penetration high frequency= better axial resolution
48
dB
10% is 10 dB, 1% is 20dB, 0.1% is -30 dB
49
bladder and cysts in US
appear as black have almost no scatter
50
width and height of individual elements in array
width = lambda/2 height = a few mm
51
transducer crystal thickness
lambda/2
52
issue with side lobes
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
what organs have many scattering sites
-kidney, pancreas, spleen, liver
54
focal depth
pt at which beam is at its narrowest
55
range of frquency of audible sound
15 Hz - 20 kHz
56
how to produce short pulses
use blocks of damping material
57
focal zone
near field region where US is narrow -don't use far zone for imaging
58
is pulsed or continuous US used in clinic
pulsed
59
size of PZT
60
what does Doppler US measure
change in frequency not velocity
61
reverbation
large number of reflected waves, which can be perceived as continuous sound
62
US contrast agents
microbubbles
63
how to improve lateral resolution
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
pulse repetition frequency to avoid aliasing
PRF> 2 X highest doppler delta f
65
how to improve axial resolution
increase transducer frequency to reduce pulse length
66
power doppler
more sensitive than regular doppler -shows only magnitude, not direction
67
show US artifacts in image
68
US artifacts in image
69
US artifacts in image
70
Anger camera max non-uniformity
5%
71
intrinsic vs extrinsic
intrinsic looks at imager part only extrinsic looks at total image, realistic conditions
72
parrallel hole collimator resolution
degraded with increasing distance from collimator
73
what scintillator is in Anger camera
NaI
74
how many counts in Anger camera
500,000
75
intrinsic resolution of anger camera
3-5 mm
76
formula for system resolution
square root (intrinsic res^2+ colli res^2) colli is limiting
77
types of SPECT collimators
-parrallel hole (constant FOV) -converging (magnified, FOV~ 1/distance) -diverging (FOV increases with distance) -pinhole (magnify and inver)
78
isotope vs isotone
isotoPe= same number of protons isotoNe= same number of neutrons
79
how far does an alpha particle travel
<0.1 mm
80
thickness of PET detector
20-30 mm thick to efficiently detect 0.511 MeV photons
81
how much more sensitive is 3D PET vs 2D PET?
3D PET is 6x more sensitive than 2D PET
82
Equation for cumulative activity
1.44*Ao*t1/2
83
S factor
absorbed dose in target organ/ unit cumulative activity in source organ S increases as the size of the organ decreases
84
MIRD
medical internal radiation dose -framework for assessing absorbed dose to organs, tissue, etc
85
99Mo breakthrough limit
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
ALI
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
does resolution degrade with depth in SPECT?
yes holes see more photons
88
equation for nuc med integral uniformity
100%*(max counts - min counts)/(max counts + min counts)
89
What does theranostic mean
rad nuclide used for therapy and diangostics
90
what does Ae^-1t + Be^-bt look like on a semi-log plot
2 straight line segments
91
efficiency of counting system
(Cradionuclide- Cbackground)/Aradionuclode *100%

Imaging Review CCPM (11 decks)

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