1.
PRINCIPLES & APPLICATIONS OF PET - CT

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
7
By Eng. Abdulkader Helwan

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
8
By Eng. Abdulkader Helwan

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.
9
By Eng. AbdulkaderHelwan

9.
FDG
CH2HO
HO
HO
O
OH
18F
CH2HO
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.
9
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.
FDG Metabolism
FDG FDG -6-P
Radio-
active
Glucose
18F-FDG
Radioactive Glucose 18F-FDG
X
Glucose Glucose
Glucose
Glucose-6-
Phosphate
Unlike glucose, FDG is trapped
11

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
12

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 formof
coincident photons :
15

15.
Coincidence Detection
16

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
BaF2 – Barium
Flouride(0.8ns)
BGO – Bismuth Germinate
Oxide(300ns)
LSO – Lutetium
Orthosilicate(40ns)
GSO – Gadolineum
Orthosilicate(60ns)
YLSO – Yttrium Lutetium
Orthosilicate(40ns)
17

18.
Data Acqusition
• The detection of photon pairs by opposing crystals create one event(LOR)
• Millions of this event will be stored within sinograms and used to reconstructthe
image
• Spatial resolution is determined by the size of the crystal and their separation andis
typically 3-5mm

19.
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
30

20.
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 normaltissues
such as the liver, lung, and marrow have SUVs ranging from 0.5 to2.5.
• The SUV of a given tissue is calculated with the following formula:

21.
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
28

22.
The distribution of FDG
within a normal individual (MIP).
31

23.
Physiologic FDG uptake

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

25.
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

26.
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

27.
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

28.
• ASSESSMENT OF TREATMENT RESPONSE
Pretherapy and post
therapy
studies showing a
complete metabolic
response to therapy.

29.
PET in Neurology
The Active Human Brain

30.
Hypo metabolism in left temporal lobe secondary to epilepsy

31.
THANK YOU
new ideas make work interesting
40