PET - Positron Emission Tomography Basicsepileptologie-bonn.de/.../AAghababaei-PETbasics.pdf ·...

PETPositron Emission Tomography

Basics

Alireza Aghababaei

April 15, 2019

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1 MotivationPositron/iumRadioactivity

2 Imaging stepsIsotopesTracerReconstruction

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Anatomic(CT/MRI) vs Metabolism(PET)

source: deserthealthnews.comMRI scan of the body

source:wikipediaCT-Scan

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Function and Metabolism(PET)

source: medicalxpress.com

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source: healthcare-in-europe.com

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Positron

Electron’s antiparticle

Annihilation by colliding toelectron

Positronium consist of a e+

and e− similar to H-Atom

Annihilation of electron andPositron

e+ + e− −→ γ + γ

Energy conservation

γ angle is (180.0± 0.5)◦

The Energy of the γs are511 keV

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Mean free path length (β+ range)

Resolution never perfect

Emitted positron needs to lose energy

Lose energy require distance

Annihilation

There is some distance between positron emitter and annihilationpoint

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Units

Unit of radioactivity: becquerel

1 Bq = 1 decay per second

Older unit: Curie

1 Ci is the activity of 1 g of the 226Ra

1 nCi = 37 kBq

Unit of ionizing radiation and a measure of health effect on thehuman body (Dose equivalent): Sievert

1 Sv = 1 J kg−1 of human tissue

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What is radioactive?

supervised area 1 mSv a−1

controlled area 6 mSv a−1

exclusion area 3 mSv h−1

natural background radiation 0.1 µSv a−1

Background radiation due to cosmic radiation, radon gas decay in the air,K40 in food, ...

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Imaging steps

Radio isotope Production

For each pet imaging study one needs to produce the Radio-tracer onthe day of the scan (why?)

Using Cyclotron and bombarding an atom and make it unstable

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Imaging steps

Isotopes

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Imaging steps

Cross section

Figure: source: oecd-nea.org

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Imaging steps

Parent Nucleus Parent T1/2 Decay Mode Daughter Nucleus189 F 109.77 m β+: 100 % 18

8 O116 C 1221.8 s β+: 100 % 11

5 B158 O 122.24 s β+: 100 % 15

7 N137 N 9.965 m β+: 100 % 13

6 C

Table: source: nndc.bnl.gov (National Nuclear Data Center)

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Imaging steps Tracer

Radiotracer

We are now running on a Clock! (look at the T1/2)

Now we still need to attach the radio isotope to a biomolecule

It should be as pure as possible to inject to a patient

Depends on what one wants to see

Then we can start the scan

FDG : FludeoxyglucoseGlucose Metabolism

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Imaging steps Tracer

What do we see:

BrainHeartLiverBone marrow

source: researchgate.netCoronal F18-FDG PET scan

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Imaging steps Tracer

lung cancer

Figure: D.Groheux: FDG PET-CT

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Imaging steps Tracer

Image reconstruction

source: Florin Turcu, researchgate.netLine Of Response

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Imaging steps Tracer

the projections are integrals of the radiotracer in the body

Sinogram: row data

source: Adam Alessio, PhD and Paul Kinahan, PhD

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Imaging steps Tracer

source: Adam Alessio, PhD and Paul Kinahan, PhD

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Imaging steps Tracer

Method: filtered backprojection (FBP)

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Imaging steps Tracer

Summery

Function and metabolism imaging

Bad resolution mean free path length

Radioactivity, time limit, radiotracer

Image reconstruction

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Imaging steps Tracer

Literature

Mathematical Medicine: Positron Emission Tomography (PETScans),Sully Chen, medium.com

https://www.researchgate.net, WHOLE BODY PET BASED ON ANRPC SYSTEM Florin Constantin, Florin Turcu

Principles and Practice of PET-CT Part 1A Technologist‘s Guide, Siemens

Positron Emission Tomography, Springer

https://www.oecd-nea.org/janisweb/book/protons/O18/MT4/renderer/110

Cyclotron Produced Radionuclides: Physical Characteristics andProduction Methods, IAEA

Reconstruction of Positron Emission Tomography Images UsingGaussian Curvature, Jose Mejia

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Imaging steps Tracer

Thanks for your attention! Any questions?

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