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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
Alireza Aghababaei PET April 15, 2019 4 / 25
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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