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MRSC 2501 > SPECT and PET > Flashcards

SPECT and PET Flashcards

1
Q

2 types of images in SPECT

A

Planar

Tomographic

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2
Q

In Planar imaging is the Gamma camera moving or stationary?

A

Stationary

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3
Q

Another name for a scintillation camera?

A

gamma

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4
Q

2 types of data that leaves the PMT to the CPU in SPECT?

A

Position and energy data

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5
Q

Does SPECT planar have good spatial resolution?

A

no

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6
Q

What is the process in NM for detecting photons emitted from a radiopharmaceutical called?

A

Emission Computed Tomography.

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7
Q

Type of rays detected in SPECT and PET?

A

Gamma.

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8
Q

Areas often imaged in SPECT?

A

Cardiac
Liver/ spleen
Chest / thorax

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9
Q

Typically how many Gamma cameras does a SPECT machine have?

A

2

3 makes examinations quicker but isnt cost effective.

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10
Q

does a SPECT scanner gather images in 360 deg or 180 deg?

A

both

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11
Q

How many images does a gamma camera typically acquire per rotation?

A

128

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12
Q

Out of SPECT and PET which is most affected by Photon attenuation ?

A

SPECT

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13
Q

What is the main reason for having more than 1 gamma camera?

A

increased sensitivity.

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14
Q

how far does a 2 headed SPECT need to rotate to get a full image profile?

and a 3 gamma camera SPect?

A 
2 = 180deg
3= 120 deg.
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15
Q

When would a perpendicular arrangement be used for SPECT?

A

Cardiac or brain imaging

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16
Q

Why is SPECT not a sensitive imaging modality?

A

because the collimator blocks 99.95% of photons emitted from the patient before they can incident on the detector.

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17
Q

What is the line of response in SPECT?

A

essentially the gamma rays that make it through the collimator without being scattered or absorbed.

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18
Q

what is a projection or projection profile in spect?

A

a full set of response lines .

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19
Q

What is a CINE view?

A

Sequential projection profiles.

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20
Q

What does 360 deg data acquisition improve in SPECT?

A

Resolution and attenutation correction.

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21
Q

When is 180 degrees rotation commonly used in SPECT?

A

heart or organs positioned at one side of the body.

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22
Q

What is aquisiton time dependent on in SPECT

A

Radioactivity
no. gamma cameras
counting efficienct

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23
Q

What has the greatest effect on scanning time in SPECT?

A

Patient comfort.

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24
Q

Another name for a contour orbit?

A

scout image

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25
When is a elliptical orbit used in spect?
when the gamma camera needs to get close to organs.
26
Why is a moving detector trying to be phased out in SPECT?
it only allows for imaging of SLOW biological processes.
27
What should pixel width be less than or equal to in spect?
THE COLLIMATOR.
28
is resolution higher or lower with a wider pixel width?
lower.
29
Reducing collimation hole size increases resolution but why are they not made as small as possible?
reduces detector sensitivity and increases sacnning time.
30
What is a sinogram used for?
Correct for MINOR patient movement.
31
How many sinograms are used in SPECT?
1 for each slice.
32
What does a break in the sinogram show?
patient movement.
33
Without attenutation correction what would occur to the data gathered from a patient in SPECT?
Less activity in deep tissues since more photons are being absorbed.
34
What does loss of counts due to attenuation cause?
Increased: noise artefacts distortion of image.
35
What does the Chang method presume?
A constant attenuation coefficient throughout the patient.
36
What linear attenuation coefficient is typically used for image reconstruction in SPECT?
0.12 - 0.13 cm(-1) decimeters
37
What radionucleide is typically used for measuring the attenuation coefficient?
Galidium 153
38
What contributes to image noise
Photon scattering Statistical variation Random electronic fluctations
39
Frequency for background, image data and noise?
``` background = low Image = medium Noise = high. ```
40
What will a high pass filter block out and therefore increase what?
low frequencies increases SNR
41
2 types of image reconstruction in SPECT
iterative and back
42
How is a star artifact formed and corrected?
From the back projection Filtering and increasing number of views
43
What do all filters aim to do in spect ? and therefore reduce?
Contrast, reduce spatial resoltuon
44
when can filters in spect be applied?
Before and during back projection.
45
What does ramp filter remove?
star artifact and low frequency data.
46
Do we want particles with a long or small range in PET?
short ... FDG-18
47
What is FDG 18?
Flurodeoxyglucose
48
What doesnt PET have that SPECT has?
Collimator
49
Energy of annihilated photons?
511 keV
50
How fast are the photons detected in PET?
10(-9) seconds nanosecond
51
Is the detectors or patient moved in PET?
Patient.
52
Detector arrangment in PET?
Scintillator crystal -> PMT -> Detector -> CPU
53
Advantages of PET over SPECT?
Greater sensitivity and resoultuon . Dont always need high atomic number materials.
54
Disadvantages of PET over SPECT?
Cost extremely short H1/2
55
What type of radiation must the radionuclides emit?
Beta +
56
How are B+ emitters typically produced.
in a cyclatron parent isotope is bombarded with protons and Helium nuclei. The atom needs to have an excess of protons for B+ to be produced if it has an excess of neutrons then B- is produced.
57
Why are 11C , 13N and 15O typically not used in PET
Whils tthey show differnt function due to being gasses. their H/12 is too short and therefore difficult to image with.
58
Typically for PET is a radionuclide with a high or low positron yield preferable?
high
59
In PET is detection of coincidence photons preferable?
yes.
60
What time do 2 perpendicular photons have to be recorded at to be considered a coincidence?
6-12 nanoseconds.
61
What type of data is the coincidence data?
raw.
62
How precise is the PET time stamp?
1-2 nanoseconds
63
How does collimation work in PET?
electronically. discarding 'single events' (where only 1 photon of the annihilation reaction is incident on the detector).
64
does PET have worse or better spatial resolution than SPECT and why?
Better as it is more efficient and records more photon counts.
65
Do scatter events orginate in the patient?
yes but are detected in another detector pairs FOV.
66
What is an accidental random event in PET
Events detected by opposing detectors within the same timestamp but from outside the ROI. typically increases the probability of this event when using a radionuclide with a high radioactivity.
67
3 types of single PET events
Photon is registered but isnt from annhilation reaction Photon leaves the plane of detection Photon is absorbed by another medium
68
Can the time of flight technique be used when ROI is in centre of detector rings
no as both photons will incident at same time.
69
What is timing jitter?
Detectors with a low light output.
70
What type of artifact is associated with unfiltered back projection?
star
71
Is a 2D pet image aquired with or without the septa in place?
With,
72
Typical scintillator in PET
BGO Bismuth Germanate. GSO Gadolinium orthosilicate.
73
Do scintillators perform better with a higher or lower light yield ?
Higher Better Energy resolution and spatial resolution
74
Is a shorter or longer decay time preferable for a crystal?
shorter as it allows for rapid imaging.
75
Do we want the PMT closer or further from the site of impact?
closer.
76
What does PHA measure?
Time of detection Energy size of signal.
77
What time is the coincidence circuit set to?
5-15 ns

MRSC 2501 (3 decks)

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