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ECSE-4963
Introduction to Subsurface Sensing
and Imaging Systems
Lecture 21: Nuclear Medicine/PET
Kai Thomenius1
& Badri R...
Recap
• Molecular Imaging has tremendous potential.
– MI is the result from a tight coupling of biology &
subsurface imagi...
Nuclear Medicine/PET
• Up to now, our focus has been on
imaging physical objects.
– We have looked for features which inte...
Nuclear Medicine
• Imaging is done by tracing the
distribution of
radiopharmaceuticals within the
body.
• Radionuclides or...
How does this work?
• Radioisotopes are injected into
the body
• A radioisotope can be:
– a pure element (e.g. I-131 which...
Physics of Nuclear Medicine
• 3 basic mechanisms for
photon - matter interaction:
– Photoelectric Effect
– Compton Scatter...
Energy of a Gamma Ray
• Radionuclide has a
typical energy: e.g. 140
keV for 99m
Tc
• Detection of lower
energy scattered
g...
Nuclear Imaging - Instruments
Nuclear Medicine Imagers
Steps in imaging
• Imaging done by a gamma
camera.
• A radionuclide is infused
into the patient’s blood.
– Usually, the ra...
Detector or Scintillator
• (NaI): Emits light
whenever hit by
gamma ray. Amount of
light is proportional to
gamma energy l...
Cross-section of an Anger
Camera
1. Shield Around Head
2. Mounting Ring
3. Collimator Core
4. Sodium Iodide Crystal
5. Pho...
Nuclear Medicine Performance
Metrics
• Typical performance:
– Energy resolution: 9.5 – 10%
• FWHM response
– Spatial resol...
Collimator Design & Function
Resolution v. Efficiency Trade-off
Nuclear Medicine Images
• Typical image:
– 64 by 64 pixels
• Intensity gives “counts per
pixel”
• Pseudocolor often used.
...
Cardiac Study
Cardiac Study
• Evaluation of the
coronary artery
circulation
– Myocardial
perfusion
• 3D Studies of the
radionuclide
acti...
SPECT Scanners
• Single Photon
Emission
Computerized
Tomography
– Store radionuclide
emission data from
multiple projectio...
PET – Positron Emission
Tomography
• Certain radionuclides
emit positrons.
• When a positron meets
an electron, they
annih...
How Does PET Compare With
Other Imaging Modalities?
• PET provides images of molecular-level physiological
function
• Exte...
PET Systems Event Detection
• Several gamma-detector
rings surround the patient.
• When one of these detects
a photon, a d...
PET Radiotracers
• 18
FDG is probably
the most widely
used PET tracer.
• HIGH FDG pick-
up by tumors first
reported in 198...
Application in Lung Cancer
Case Study:
• 55-year old female
• Lung Cancer
• 2 cycles of chemo
& radiotherapy
PET results:
...
PET/CT Scanners
• Generation of PET
& CT images in a
single study
• The image data
sets are registered
and fused.
– Anatom...
PET & Molecular Imaging
• There is a strong similarity
w. PET & MI.
– PET is often classified under
MI.
• There is a signi...
Source Material
• http://apps.gemedicalsystems.com/geCommunity
jsp
• Siemens & Philips web sites for nuclear
medicine & PE...
Summary
• Introduction to Nuclear Medicine and PET
imaging.
– Additional examples of agents (probes) introduced to
reveal ...
Homework: Lecture 21
• Using internet sources,
–discuss the patient and clinician safety
issues from the use of radioactiv...
Instructor Contact Information
Badri Roysam
Professor of Electrical, Computer, & Systems Engineering
Office: JEC 7010
Rens...
Instructor Contact Information
Kai E Thomenius
Chief Technologist, Ultrasound & Biomedical
Office: KW-C300A
GE Global Rese...
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Transcript of "ECSE-4963 Introduction to Subsurface Sensing and Imaging Systems"

  1. 1. ECSE-4963 Introduction to Subsurface Sensing and Imaging Systems Lecture 21: Nuclear Medicine/PET Kai Thomenius1 & Badri Roysam2 1 Chief Technologist, Imaging Technologies, General Electric Global Research Center 2 Professor, Rensselaer Polytechnic Institute Center for Sub-Surface Imaging & Sensing
  2. 2. Recap • Molecular Imaging has tremendous potential. – MI is the result from a tight coupling of biology & subsurface imaging technologies. • Pursuit of activities in this area will require a good grounding in cell biology, biochemistry. – PET, nuclear will be most likely the first modalities esp. in human imaging. – Optical imaging, MRI are receiving much attention in animal studies. – There is a very exciting potential for a fundamental change in diagnostic & therapeutic medicine. • Today – Nuclear Medicine/PET
  3. 3. Nuclear Medicine/PET • Up to now, our focus has been on imaging physical objects. – We have looked for features which interact with our probes • Attenuation with X-ray • Impedance mismatches in pulse-echo methods • Variations in proton density – Nuclear medicine & PET are quite different – Like MI, we are imaging concentrations of exogenous chemicals injected into the patient • The observability of these is invariably based on radioactivity.
  4. 4. Nuclear Medicine • Imaging is done by tracing the distribution of radiopharmaceuticals within the body. • Radionuclides or radioisotopes are atoms that undergo radioactive decay, and emit radiation. • In nuclear medicine, we are interested in radionuclides that emit x-rays or gamma rays. • A radiopharmaceutical is a radionuclide bound to a biological agent.
  5. 5. How does this work? • Radioisotopes are injected into the body • A radioisotope can be: – a pure element (e.g. I-131 which connects to Thyroid) – a biological agent labeled with radioisotopes like MIBI-Tc99m • All isotopes have a half life. • All isotopes are expelled from the body with an associated half life. • Nuclear Medicine provides physiological images, i.e. the metabolic activity of the organs process the radiopharmaceutical and concentrate it in the target organs for imaging.
  6. 6. Physics of Nuclear Medicine • 3 basic mechanisms for photon - matter interaction: – Photoelectric Effect – Compton Scatter – Pair Production • Any one of these can happen to the radionuclide gamma-rays. Compton Scatter Pair Production
  7. 7. Energy of a Gamma Ray • Radionuclide has a typical energy: e.g. 140 keV for 99m Tc • Detection of lower energy scattered gamma- or x-rays degrades contrast and image quality. • A radioisotope emits one (or more) very sharp energy lines
  8. 8. Nuclear Imaging - Instruments
  9. 9. Nuclear Medicine Imagers
  10. 10. Steps in imaging • Imaging done by a gamma camera. • A radionuclide is infused into the patient’s blood. – Usually, the radionuclides have a specific physiological role. – This gives the clinical specificity to the procedure. • Concentrations of the agent emit greater quantity of gamma rays. • These are mapped by the camera head.
  11. 11. Detector or Scintillator • (NaI): Emits light whenever hit by gamma ray. Amount of light is proportional to gamma energy level. • Photomultiplier Tubes: read the light signals and translate them into electrical signals
  12. 12. Cross-section of an Anger Camera 1. Shield Around Head 2. Mounting Ring 3. Collimator Core 4. Sodium Iodide Crystal 5. Photomultiplier Tubes
  13. 13. Nuclear Medicine Performance Metrics • Typical performance: – Energy resolution: 9.5 – 10% • FWHM response – Spatial resolution: 3.2 – 3.8 mm – Uniformity: 2 – 4%
  14. 14. Collimator Design & Function Resolution v. Efficiency Trade-off
  15. 15. Nuclear Medicine Images • Typical image: – 64 by 64 pixels • Intensity gives “counts per pixel” • Pseudocolor often used. • Nuclear med imaging modes: – Static – Dynamic – MUGA – Whole Body – SPECT
  16. 16. Cardiac Study
  17. 17. Cardiac Study • Evaluation of the coronary artery circulation – Myocardial perfusion • 3D Studies of the radionuclide activity
  18. 18. SPECT Scanners • Single Photon Emission Computerized Tomography – Store radionuclide emission data from multiple projections – Projections taken every 3 or 6 degrees. – Use CT type algorithms to determine the location and degree of accumulation of agent.
  19. 19. PET – Positron Emission Tomography • Certain radionuclides emit positrons. • When a positron meets an electron, they annihilate each other. • This annihilation results in a generation of two gamma rays. – The gamma rays travel in opposite directions. – The energy of these gamma rays is 511 KeV. • PET Imaging is based on detection of these gamma rays.
  20. 20. How Does PET Compare With Other Imaging Modalities? • PET provides images of molecular-level physiological function • Extends capabilities of other modalities. – Like MR & CT, it uses tomographic algorithms – Like Nuclear Medicine, the images represent distributions of radiotracers. • But that’s where the similarity ends… CT Scan MRI Scan PET Scan Report: Normal Report: Normal Report: Patient Deceased.
  21. 21. PET Systems Event Detection • Several gamma-detector rings surround the patient. • When one of these detects a photon, a detector opposite to it, looks for a match. • Time window for the search is few nanosecs. • If such a coincidence is detected, a line is drawn between the detectors. • When done, there will be areas of overlapping lines indicating regions of radioactivity.
  22. 22. PET Radiotracers • 18 FDG is probably the most widely used PET tracer. • HIGH FDG pick- up by tumors first reported in 1980 at Brookhaven NL. • Can also be used to measure rate of metabolism in the brain.
  23. 23. Application in Lung Cancer Case Study: • 55-year old female • Lung Cancer • 2 cycles of chemo & radiotherapy PET results: • Increased uptake of FDG in lung nodules • Increased uptake of FDG in lymph nodes Therapy will have to be continued.
  24. 24. PET/CT Scanners • Generation of PET & CT images in a single study • The image data sets are registered and fused. – Anatomic data from CT – Metabolic data from PET • Colorectal Cancer shown in images.
  25. 25. PET & Molecular Imaging • There is a strong similarity w. PET & MI. – PET is often classified under MI. • There is a significant distinction, however. • MI probes are often designed to interact w. cellular processes. – This interaction is used to improve detectability. • PET probes are usually passive in this regard. – They rely on the inherent radioactivity of the probes.
  26. 26. Source Material • http://apps.gemedicalsystems.com/geCommunity jsp • Siemens & Philips web sites for nuclear medicine & PET • http://www.crump.ucla.edu/software/lpp/lpphome. • http://thayer.dartmouth.edu/~bpogue/ENGG167/1
  27. 27. Summary • Introduction to Nuclear Medicine and PET imaging. – Additional examples of agents (probes) introduced to reveal subsurface phenomena. – Today’s focus on radioactive labeling. • Review of instruments – Relatively straightforward devices. – Signal-to-noise ratio challenges, need to limit exposure. • Powerful clinical tools. • Much of today’s research focused on PET and extensions of PET technology.
  28. 28. Homework: Lecture 21 • Using internet sources, –discuss the patient and clinician safety issues from the use of radioactive tracers in PET and nuclear imaging. –SPECT imaging is a variant of the scanners discussed today. Review their operation and discuss how SPECT imagers use the computed tomography algorithms (e.g. filtered backprojection) discussed earlier.
  29. 29. Instructor Contact Information Badri Roysam Professor of Electrical, Computer, & Systems Engineering Office: JEC 7010 Rensselaer Polytechnic Institute 110, 8th Street, Troy, New York 12180 Phone: (518) 276-8067 Fax: (518) 276-6261/2433 Email: roysam@ecse.rpi.edu Website: http://www.rpi.edu/~roysab NetMeeting ID (for off-campus students): 128.113.61.80 Secretary: Betty Lawson, JEC 7012, (518) 276 –8525, lawsob@.rpi.edu
  30. 30. Instructor Contact Information Kai E Thomenius Chief Technologist, Ultrasound & Biomedical Office: KW-C300A GE Global Research Imaging Technologies Niskayuna, New York 12309 Phone: (518) 387-7233 Fax: (518) 387-6170 Email: thomeniu@crd.ge.com, thomenius@ecse.rpi.edu Secretary: Betty Lawson, JEC 7012, (518) 276 –8525, lawsob@.rpi.edu
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