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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
Q

When is a elliptical orbit used in spect?

A

when the gamma camera needs to get close to organs.

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26
Q

Why is a moving detector trying to be phased out in SPECT?

A

it only allows for imaging of SLOW biological processes.

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27
Q

What should pixel width be less than or equal to in spect?

A

THE COLLIMATOR.

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28
Q

is resolution higher or lower with a wider pixel width?

A

lower.

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29
Q

Reducing collimation hole size increases resolution but why are they not made as small as possible?

A

reduces detector sensitivity and increases sacnning time.

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30
Q

What is a sinogram used for?

A

Correct for MINOR patient movement.

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31
Q

How many sinograms are used in SPECT?

A

1 for each slice.

32
Q

What does a break in the sinogram show?

A

patient movement.

33
Q

Without attenutation correction what would occur to the data gathered from a patient in SPECT?

A

Less activity in deep tissues since more photons are being absorbed.

34
Q

What does loss of counts due to attenuation cause?

A

Increased:

noise
artefacts
distortion of image.

35
Q

What does the Chang method presume?

A

A constant attenuation coefficient throughout the patient.

36
Q

What linear attenuation coefficient is typically used for image reconstruction in SPECT?

A

0.12 - 0.13 cm(-1) decimeters

37
Q

What radionucleide is typically used for measuring the attenuation coefficient?

A

Galidium 153

38
Q

What contributes to image noise

A

Photon scattering
Statistical variation
Random electronic fluctations

39
Q

Frequency for background, image data and noise?

A 
background = low 
Image = medium
Noise = high.
40
Q

What will a high pass filter block out and therefore increase what?

A

low frequencies

increases SNR

41
Q

2 types of image reconstruction in SPECT

A

iterative and back

42
Q

How is a star artifact formed and corrected?

A

From the back projection

Filtering and increasing number of views

43
Q

What do all filters aim to do in spect ? and therefore reduce?

A

Contrast,

reduce spatial resoltuon

44
Q

when can filters in spect be applied?

A

Before and during back projection.

45
Q

What does ramp filter remove?

A

star artifact and low frequency data.

46
Q

Do we want particles with a long or small range in PET?

A

short … FDG-18

47
Q

What is FDG 18?

A

Flurodeoxyglucose

48
Q

What doesnt PET have that SPECT has?

A

Collimator

49
Q

Energy of annihilated photons?

A

511 keV

50
Q

How fast are the photons detected in PET?

A

10(-9) seconds

nanosecond

51
Q

Is the detectors or patient moved in PET?

A

Patient.

52
Q

Detector arrangment in PET?

A

Scintillator crystal -> PMT -> Detector -> CPU

53
Q

Advantages of PET over SPECT?

A

Greater sensitivity and resoultuon .

Dont always need high atomic number materials.

54
Q

Disadvantages of PET over SPECT?

A

Cost

extremely short H1/2

55
Q

What type of radiation must the radionuclides emit?

A

Beta +

56
Q

How are B+ emitters typically produced.

A

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
Q

Why are 11C , 13N and 15O typically not used in PET

A

Whils tthey show differnt function due to being gasses.

their H/12 is too short and therefore difficult to image with.

58
Q

Typically for PET is a radionuclide with a high or low positron yield preferable?

A

high

59
Q

In PET is detection of coincidence photons preferable?

A

yes.

60
Q

What time do 2 perpendicular photons have to be recorded at to be considered a coincidence?

A

6-12 nanoseconds.

61
Q

What type of data is the coincidence data?

A

raw.

62
Q

How precise is the PET time stamp?

A

1-2 nanoseconds

63
Q

How does collimation work in PET?

A

electronically.

discarding ‘single events’ (where only 1 photon of the annihilation reaction is incident on the detector).

64
Q

does PET have worse or better spatial resolution than SPECT and why?

A

Better as it is more efficient and records more photon counts.

65
Q

Do scatter events orginate in the patient?

A

yes but are detected in another detector pairs FOV.

66
Q

What is an accidental random event in PET

A

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
Q

3 types of single PET events

A

Photon is registered but isnt from annhilation reaction

Photon leaves the plane of detection

Photon is absorbed by another medium

68
Q

Can the time of flight technique be used when ROI is in centre of detector rings

A

no as both photons will incident at same time.

69
Q

What is timing jitter?

A

Detectors with a low light output.

70
Q

What type of artifact is associated with unfiltered back projection?

A

star

71
Q

Is a 2D pet image aquired with or without the septa in place?

A

With,

72
Q

Typical scintillator in PET

A

BGO

Bismuth Germanate.

GSO Gadolinium orthosilicate.

73
Q

Do scintillators perform better with a higher or lower light yield ?

A

Higher

Better Energy resolution and spatial resolution

74
Q

Is a shorter or longer decay time preferable for a crystal?

A

shorter as it allows for rapid imaging.

75
Q

Do we want the PMT closer or further from the site of impact?

A

closer.

76
Q

What does PHA measure?

A

Time of detection

Energy size of signal.

77
Q

What time is the coincidence circuit set to?

A

5-15 ns

MRSC 2501 (3 decks)

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