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Physics session > Nuclear medicine > Flashcards

Nuclear medicine Flashcards

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1
Q

in vivo

A

measured as it leaves the body. eg bone scans from gamma camera

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2
Q

in vitro

A

no images, given to patient then biopsies taken

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3
Q

what are examples of non nuclear imaging?

A

Contrast enhanced ultrasound
optical imaging
MRI spec

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4
Q

CEUS with ligands is used or preclinical

A

it is preclinical

looking for things like VEGF, ICAM1 (inflammatory markers)

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5
Q

what are the two types of optical luminescence?

A

bioluminsecne

fluorescence

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6
Q

Bioluminescence

A

luciferase enzyme in cells.

Lucinferin is injected, chemical reaction with photon produced.

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7
Q

what type of cells contain luciferase?

A

Tumour cells

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8
Q

Fluorescence

A

an injected molecule is activiated with a an external light source/wavelength,

good as can be repeatably excited

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9
Q

what are the three ways of producing radioisoptopes

A

Cyclotron

Generator

Nuclear reactor

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10
Q

Cyclotron creates them how>

A

Bombardes.

Dee (D shaped electrodes either sid eof a vacuum)
- spin them in a circle with an AC current.

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11
Q

What isotopes are produced by bombardement in Cycltron?

A

Tehcnetium 99m (Molybdenum is blasted).
Fluorine 18 (oxygen rich water is bombarded)
Gallium 67
Thallium 201

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12
Q

gallium 67 used in what?

A

inflammation nad tumours

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13
Q

Thallium 201 used in what?

A

heart scans

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14
Q

How are RI produced in a nuclear reactor?

A

Uranium 235 - fission -
Uranium 236. Makes lots of neutrons.

Create neutron rich RI

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15
Q

Neutron rich RI will decay how?

A

Via B negative emission.

Proton rich –> proton and negative thing

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16
Q

What are nuclear reactor created RI?

A

Molybdenum98 (then used in cycltrons!)

Iodine 131

Xenon 133

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17
Q

Why is Xenon 133 better than crypton for ventilation tudies?

A

Xenon has a half life of 5 days so easier to traonsport.

As apposed to 13 seconds.

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18
Q

Radionuclide generator creates RI how?

A

Slow decaying element absorbed on to a surface like alumina.

encased in lead.

the decayed daughter RI is then used by elluting with sodium chloride.

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19
Q

Generator produced RI?

A

Tehcnetium 99m

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20
Q

What is the pathway for making Tech99

A

Nuclear reactor makes Moly98
Cyclotron takes Moly98 and makes Moly 99
Moly 99 goes to Tech99`

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21
Q

which way is krypton make?

A

Generator

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22
Q

Ideal property of radioisotope

- half life

A

long enough to achieve image
short enough to limit radiation dose

ideal 1.5 x length of imaging

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23
Q

Ideal property of radioisotope

- gamma ray energy

A

high enough to reach the gamma camera.

if low energy they are absorbed by the body increasing the dose.

Mono energetic gamma emitter between 100 and 250kEv.

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24
Q

Ideal property of radioisotope

- deays to what

A

a stable isotope

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25
Q

Ideal property of radioisotope

- binding

A

easy to bind

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26
Q

Ideal pharmaceutical

A

high target: non-target uptake ratio
Easy and cheap
non toxic
does not alter physiology that you are measuring

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27
Q

Cardiac imaging uses

A

Thalium 201

- to see perfusion of muscle immediately and later

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28
Q

Technetium 99m tetrofosmin

A

myocardial perfusion

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29
Q

MUGA is used in what

A

Ventriculography. labelled blood ells.

Wall motion and chamber size

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30
Q

Iodine 131 is used in?

A

Neuroendocrine.

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31
Q

Renal imaging RI?

A

Tech99 DMSA - cortical function

Tech99 MAG3 - eGFR

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32
Q

CNS imaging examples

A

Brian SPECT tech99

Iodine 123. for parkinsons

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33
Q

Iodine 123 is used in which scan

A

DaTscan

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34
Q

what are the positiron emittors?

A

PET FLOC GAL

Gallium67
Fl18
Oxygen
Carbon 11

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35
Q

How are the positron emittors made?

A

Cycltron

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36
Q

What are the componenets of a gamma camera?

A

Collimator
radiation detector (Scint and PMT)
Electronic

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37
Q

Collimators are usualy made of what?

A

Lead

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38
Q

what is the purpose of the collimator?

A

for spatial mapping

NOT to do with scatter

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39
Q

diverging causes what to the image

A

minification

diverges at the object

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40
Q

converging causes what

A

mag

converges at the object

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41
Q

the collimators need to be able to absrob what energy gamma rays

A

150 - 400

42
Q

Low collimators are used for which RI

A

99mTC

43
Q

High energy collimators used for which RI

A

Iodine 131

44
Q

Gamma camera - what is the scintallator used

A

Sodium Iodide with a hint of thallium in an aluminium can

45
Q

How thick is the scintallator

A

6-13mm

46
Q

in a gamma camera what is a light pipe?

A

Perspex slab.

between the crystal and PMT.

47
Q

How does a PMT work

A

light photon hits a photocathode - gives an electron.
Accelerated between dynodes and multiplies.
Detected as an electrical charge.

48
Q

how many PMTs are there?

A

30 - 100

49
Q

how does the gamma photon interact with the scintillation?

A

By PE or compton.

50
Q

What is FWHM

A

full width at half maximum

51
Q

Energy resolution =

A

FWHM kEV / photopeak x 100

52
Q

How is scatter removed?

A

NOt by the collimator

By energy discrimination. A 20% window either side of the peak kV .

More than one peak can be used

53
Q

down side of removing scatter by energy discrimination this?

A

removes low energy scatter but also low energy unscattered.

54
Q

planar imaging gets images in what way?

A

2D

55
Q

Static planar imaging is good for what

A

size, shape, uptake DMSA

56
Q

Dynamic planar imaging is good for…

A

when the uptake changes over time (rapidly) MAG3

57
Q

Gated - planar imaging

A

regular motion organs like the heart.

58
Q

Are collimators used in planar imaging?

A

yes. can change them based on scan

59
Q

How can SNR be increased in planar imaging

A

increase the count density by

  • increasing imaging time
  • increase adminisitred radiation
  • ensure acceptable gamma camera sensitivity
60
Q

Matrix relationship with SNR

A

large matrix more pixels
- more resolution

Less SNR

61
Q

Typical matrix in planar imaging?

A

64 x 64 for gated

256 x 256 for dynamic

62
Q

How can orietnation assist in planar imaging?

A

Continuous movement

Step and shoot

63
Q

If the detector is closer to the patient what does this improve?

A

the resolution

64
Q

in planar imaging how can we achieve contrast enhanement

A

windowing

65
Q

ROI

A

Area of interest to assit with count number

66
Q

planar imaging - what are time activity curves

A

ROI count rate can be plotted as a graph.

  • time to reach peak
  • area under the curve
  • washout rate
67
Q

In SPECT - what should the distribution be of the radiopharmaceutical be?

A

The distribution should not shange over the 20 - 40 mins of the scan

68
Q

how many heads on a gamma camera?

A

at least 2 - rotate.

69
Q

How does CT come into SPECT

A

can put the XR beam between the cameras.

Helps to do attenuation corrections for the nuclear medicine through DIRECT measurement.

70
Q

in SPECT - non - parallel collimator can only be used with what?

A

Circular orbits.

NOT body contouring

71
Q

normal matrix size for dual headed system?

A

128 x 128

72
Q

how does the spect gantry roate

A

step and shoot

73
Q

cardiac spect is what matrix

A

64 x 64

74
Q

PET -

distance of where the positron is emitted and where it annihilates is….

A

variable

75
Q

Ideal PET scintillation

A

high LAC for 511keV photons

PE more than Compton interaction

lots of light phtons produced per gamma photon absorbed

short scsinilattion light decay time

76
Q

What scintillation crystal is use din pET

A

Bismuth germinate

77
Q

downside of BGO (why we use LGO and GSO)

A

light output and decay time are inferior to NaI

78
Q

How many PMT to each scintilattor block in PET

A

4

79
Q

in PET what are the detector elements?

A

each crystal is subdivided into detector elements with reflective elements to prevenet cross talk

80
Q

PET - what is a coincidence?

A

co - incidene t

detection at the same time by the gamma detectors

81
Q

line between points of coincidence is called the

A

linear response line.

82
Q

how can collimation be used for 2D vs 3D

A

2D - single plane

tungsten collimator ensures only photons from a single plane are received.

83
Q

how does 3D imaging and collimation worl?

A

no collimation

higher counts

84
Q

how to avoid scatter in PET

A

energy discrimination for photopeak window..

But not great as has to be wide due to poor energy resolution of the scintillators.

85
Q

What causes increased random coincidence

A

more radionuclide

3D acquisition

increased coincidience window (normally 1ns)

86
Q

PET - how to correct for attenuation through the body of the photons

A

Gallium rod without the patient measured

Then with the patient present.

87
Q

how to account for dead time

A

most problemtaic in 3D

have mathematial equations

88
Q

how to account for radioactive decay

A

counts are corrected for time

89
Q

what is the contrast equatin for NM

A

c = Lesion - Surrounding tissue activity amount ) / surrounding tissue activity amount

90
Q

subject contrast depends on….

A

activity difference of the tissues

91
Q

image contrast depends on….

A

counts per unit area difference

92
Q

Is RN noisy

A

yes

93
Q

types of noise

A

structured

random noise

94
Q

types of structured noise

A

(non random types)

  • nearby tissue uptake
  • imaging system artefact like non uniormity of gamma camera

not very significant compared to random noise

95
Q

types of random noise

A

same as quantum mottle and statistical noise

- random variation in count density due to random decay

96
Q

noise contrast equation

A

= 1 / square root of counts

97
Q

what is the intrinsic resolution

A

max resolution achievable by the detecotr and electronics

98
Q

collimator spatial resolution equation?

A

R = hole diameter (1+distance from radiation source to collimator / hole length)

99
Q

types of spatial resoltuon for NM

A

Intrinsic
Collimator
System spactial resolution

100
Q

system takes into account what?

A

Intrinsic and collimator

101
Q

System resolution equation

A

square root of(int square added to collimator squared)

Physics session (6 decks)

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