PET-CT Scan(Principles and Basics)

introducyion of the Pet/CT machine, its principles, the radiotracer (FDG), SUV....and the application of the PET/Ct in different medical fields

1. PRINCIPLES & APPLICATIONS OF PET - CT
Presentated BY-
Abdulkader Helwan

Submitted to: Dr. Zafer Topukcu

2. PET/CT
•Medical Imaging
Technique
•Both systems in one
Gantry
•Aquired image combined
into a coregistered image
•Functional imaging by
PET
•Anatomical imaging by
CT-Scanner
2 By Eng. Abdulkader Helwan

3. PET/CT
•Combines the functional
information with the
anatomical detail
•Accurate anatomical
registration
•Higher diagnostic
accuracy than PET or CT
alone
3 By Eng. Abdulkader Helwan

4. 4
By Eng. Abdulkader Helwan

5. Fused PET/CT images

6. PET
•Stands for positron emission tomography
•Machine that can image biological and
chemical activities
•For ex: imaging brain activity when there is a
scary event
•Active part of brain can’t be imaged using x-ray
of only CT
•It can be imaged using PET
By Eng. Abdulkader Helwan
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7. Principles of PET

•Inject a radioactive tracer bind with glucose
•The active part of brain absorbs it more than
other inactive parts
•The radioactive tracer is:
Fluorine-18-deoxyglucose (FDG), a radionuclide
labeled glucose analogue is injected into the
organ that would be imaged


By Eng. Abdulkader Helwan
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8. PET tracer: FDG
•Fluorodeoxyglucose is a glucose analog. Its full
chemical name is 2-fluoro-2-deoxy-D-glucose,
commonly abbreviated to FDG.
•Radioactive fluoride atom produced in a
cyclotron is attached to a molecule of glucose.
•The FDG molecule is absorbed by various
tissues just as normal glucose would be.

By Eng. Abdulkader Helwan 9

9. 9
FDG
CH
2HO
HO
HO
O
OH
18
F
CH
2HO
HO
HO
O
OH
OH
glucose
2-deoxy-2-(F-18) fluro-D-glucose
•Most widely used PET
tracer
•Glucose utilization
•Taken up avidly by most
tumours
•It is absorbed by various
tissues as normal glucose
would be.

By Eng. Abdulkader Helwan

10. Figure 3. Uptake of FDG. FDG is a glucose analog that is taken up by metabolically active
cells by means of facilitated transport via glucose transporters (Glut) in the cell
membrane.
Kapoor V et al. Radiographics 2004;24:523-543
©2004 by Radiological Society of North America

11. 11
FDG Metabolism
FDG FDG -6-P
Radio-
active
Glucose
18
F-FDG
Radioactive Glucose
18
F-FDG
X
Glucose
Glucose
Glucose
Glucose-6-
Phosphate
Unlike glucose, FDG is trapped

12. 12
PET Radiopharmaceuticals
Nuclide Half-life Tracer Application
O-15 2 mins Water Cerebral blood flow
C-11 20 mins Methionine Tumour protein synthesis
N-13 10 mins Ammonia Myocardial blood flow
F-18 110 mins FDG Glucose metabolism
Ga-68 68 min DOTANOC Neuroendocrine imaging
Rb-82 72 secs Rb-82 Myocardial perfusion

13. Positron and Photons Emission
Kapoor V et al. Radiographics 2004;24:523-543
©2004 by Radiological Society of North America

14. Annihilation Reaction
•The positron annihilates with an electron to release energy in the form of
coincident photons :


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15. Coincidence Detection
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16. Figure 5. Photograph (frontal view) of a hybrid PET-CT scanner shows the PET ring
detector system (red ring).
Kapoor V et al. Radiographics 2004;24:523-543
©2004 by Radiological Society of North America 17

17. CRYSTALS USED IN PET

BaF
2

– Barium
Flouride(0.8ns)
BGO – Bismuth Germinate
Oxide(300ns)
LSO – Lutetium
Orthosilicate(40ns)
GSO – Gadolineum
Orthosilicate(60ns)
YLSO – Yttrium Lutetium
Orthosilicate(40ns)
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21. Data Acqusition

•The detection of photon pairs by opposing crystals create one event (LOR)
•Millions of these event will be stored with in sinograms and used to reconstruct the
image
•Spatial resolution is determined by the size of crystal and their separation and is
typically 3-5mm


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27. Interpretation of Images

PET provides images of quantitative uptake of the radionuclide
injected that can give the concentration of radiotracer activity in
kilobecquerels per milliliter .


Methods for assessment of radiotracer uptake –
•visual inspection
•standardized uptake value (SUV)
•glucose metabolic rate

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28. SUV
•Standardized Uptake Value
•The SUV is a semiquantitative assessment of the radiotracer uptake from a
static (single point in time) PET image.
•Malignant tumors have an SUV of greater than 2.5–3.0, whereas normal tissues
such as the liver, lung, and marrow have SUVs ranging from 0.5 to 2.5.
•The SUV of a given tissue is calculated with the following formula:

29. Limitations of PET/CT
•FDG is not cancer specific and will accumulate in any
areas of high rates of metabolism and glycolysis.
•Therefore, increased uptake can be expected in all sites
of hyperactivity at the time of FDG administration (e.g.
muscles and nervous system tissues); at sites of active
inflammation or infection
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30. The distribution of FDG
within a normal individual (MIP).
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31. Physiologic FDG uptake

32. Figure 17b.
Kapoor V et al. Radiographics 2004;24:523-543
©2004 by Radiological Society of North America

33. Figure 18. Non-small cell lung carcinoma in a 78-year-old man with enlarged hilar and
mediastinal lymph nodes.
Kapoor V et al. Radiographics 2004;24:523-543
©2004 by Radiological Society of North America

34. Figure 20. Large cell lung cancer in a 54-year-old woman.
Kapoor V et al. Radiographics 2004;24:523-543
©2004 by Radiological Society of North America

35. Identification of distant metastatic disease





Top Tip
Evidence suggests that the
removal of a solitary adrenal
deposit at the time of resection of
the lung primary results in an
increased life expectancy.
Liver, adrenal, brain and bony
deposits are common with
lung cancer but many of the
lesions are undetected in
the course of conventional
staging

37. •ASSESSMENT OF TREATMENT RESPONSE
Pretherapy and post
therapy
studies showing a
complete metabolic
response to therapy.

38. PET in Neurology

The Active Human Brain

39. Hypo metabolism in left temporal lobe secondary to epilepsy

40. THANK YOU
new ideas make work interesting





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