Nuclear medicine Flashcards by Maredudd Harris

in vivo

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

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in vitro

no images, given to patient then biopsies taken

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what are examples of non nuclear imaging?

Contrast enhanced ultrasound
optical imaging
MRI spec

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CEUS with ligands is used or preclinical

it is preclinical

looking for things like VEGF, ICAM1 (inflammatory markers)

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what are the two types of optical luminescence?

bioluminsecne

fluorescence

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Bioluminescence

luciferase enzyme in cells.

Lucinferin is injected, chemical reaction with photon produced.

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what type of cells contain luciferase?

Tumour cells

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Fluorescence

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

good as can be repeatably excited

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what are the three ways of producing radioisoptopes

Cyclotron

Generator

Nuclear reactor

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Cyclotron creates them how>

Bombardes.

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

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What isotopes are produced by bombardement in Cycltron?

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

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gallium 67 used in what?

inflammation nad tumours

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Thallium 201 used in what?

heart scans

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How are RI produced in a nuclear reactor?

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

Create neutron rich RI

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Neutron rich RI will decay how?

Via B negative emission.

Proton rich –> proton and negative thing

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What are nuclear reactor created RI?

Molybdenum98 (then used in cycltrons!)

Iodine 131

Xenon 133

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Why is Xenon 133 better than crypton for ventilation tudies?

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

As apposed to 13 seconds.

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Radionuclide generator creates RI how?

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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Generator produced RI?

Tehcnetium 99m

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What is the pathway for making Tech99

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

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which way is krypton make?

Generator

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Ideal property of radioisotope

- half life

long enough to achieve image
short enough to limit radiation dose

ideal 1.5 x length of imaging

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Ideal property of radioisotope

- gamma ray energy

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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Ideal property of radioisotope

- deays to what

a stable isotope

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Ideal property of radioisotope | - binding

easy to bind

Ideal pharmaceutical

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

Cardiac imaging uses

Thalium 201 | - to see perfusion of muscle immediately and later

Technetium 99m tetrofosmin

myocardial perfusion

MUGA is used in what

Ventriculography. labelled blood ells. | Wall motion and chamber size

Iodine 131 is used in?

Neuroendocrine.

Renal imaging RI?

Tech99 DMSA - cortical function | Tech99 MAG3 - eGFR

CNS imaging examples

Brian SPECT tech99 Iodine 123. for parkinsons

Iodine 123 is used in which scan

DaTscan

what are the positiron emittors?

PET FLOC GAL Gallium67 Fl18 Oxygen Carbon 11

How are the positron emittors made?

Cycltron

What are the componenets of a gamma camera?

Collimator radiation detector (Scint and PMT) Electronic

Collimators are usualy made of what?

Lead

what is the purpose of the collimator?

for spatial mapping NOT to do with scatter

diverging causes what to the image

minification diverges at the object

converging causes what

mag converges at the object

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

150 - 400

Low collimators are used for which RI

99mTC

High energy collimators used for which RI

Iodine 131

Gamma camera - what is the scintallator used

Sodium Iodide with a hint of thallium in an aluminium can

How thick is the scintallator

6-13mm

in a gamma camera what is a light pipe?

Perspex slab. | between the crystal and PMT.

How does a PMT work

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

how many PMTs are there?

30 - 100

how does the gamma photon interact with the scintillation?

By PE or compton.

What is FWHM

full width at half maximum

Energy resolution =

FWHM kEV / photopeak x 100

How is scatter removed?

NOt by the collimator By energy discrimination. A 20% window either side of the peak kV . More than one peak can be used

down side of removing scatter by energy discrimination this?

removes low energy scatter but also low energy unscattered.

planar imaging gets images in what way?

Static planar imaging is good for what

size, shape, uptake DMSA

Dynamic planar imaging is good for...

when the uptake changes over time (rapidly) MAG3

Gated - planar imaging

regular motion organs like the heart.

Are collimators used in planar imaging?

yes. can change them based on scan

How can SNR be increased in planar imaging

increase the count density by - increasing imaging time - increase adminisitred radiation - ensure acceptable gamma camera sensitivity

Matrix relationship with SNR

large matrix more pixels - more resolution Less SNR

Typical matrix in planar imaging?

64 x 64 for gated | 256 x 256 for dynamic

How can orietnation assist in planar imaging?

Continuous movement Step and shoot

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

the resolution

in planar imaging how can we achieve contrast enhanement

windowing

ROI

Area of interest to assit with count number

planar imaging - what are time activity curves

ROI count rate can be plotted as a graph. - time to reach peak - area under the curve - washout rate

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

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

how many heads on a gamma camera?

at least 2 - rotate.

How does CT come into SPECT

can put the XR beam between the cameras. Helps to do attenuation corrections for the nuclear medicine through DIRECT measurement.

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

Circular orbits. | NOT body contouring

normal matrix size for dual headed system?

128 x 128

how does the spect gantry roate

step and shoot

cardiac spect is what matrix

64 x 64

PET - | distance of where the positron is emitted and where it annihilates is....

variable

Ideal PET scintillation

high LAC for 511keV photons PE more than Compton interaction lots of light phtons produced per gamma photon absorbed short scsinilattion light decay time

What scintillation crystal is use din pET

Bismuth germinate

downside of BGO (why we use LGO and GSO)

light output and decay time are inferior to NaI

How many PMT to each scintilattor block in PET

in PET what are the detector elements?

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

PET - what is a coincidence?

co - incidene t | detection at the same time by the gamma detectors

line between points of coincidence is called the

linear response line.

how can collimation be used for 2D vs 3D

2D - single plane | tungsten collimator ensures only photons from a single plane are received.

how does 3D imaging and collimation worl?

no collimation | higher counts

how to avoid scatter in PET

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

What causes increased random coincidence

more radionuclide 3D acquisition increased coincidience window (normally 1ns)

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

Gallium rod without the patient measured | Then with the patient present.

how to account for dead time

most problemtaic in 3D have mathematial equations

how to account for radioactive decay

counts are corrected for time

what is the contrast equatin for NM

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

subject contrast depends on....

activity difference of the tissues

image contrast depends on....

counts per unit area difference

Is RN noisy

yes

types of noise

structured random noise

types of structured noise

(non random types) - nearby tissue uptake - imaging system artefact like non uniormity of gamma camera not very significant compared to random noise

types of random noise

same as quantum mottle and statistical noise | - random variation in count density due to random decay

noise contrast equation

= 1 / square root of counts

what is the intrinsic resolution

max resolution achievable by the detecotr and electronics

collimator spatial resolution equation?

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

types of spatial resoltuon for NM

Intrinsic Collimator System spactial resolution

system takes into account what?

Intrinsic and collimator

System resolution equation

square root of(int square added to collimator squared)

Nuclear medicine Flashcards

(101 cards)