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Welcome to Louie's PET Scan Page
What is PET and how does it work?
     PET, or Positron Emission Tomography, is a "camera" that produces powerful images of the body's biological functions to reveal the mysteries of disease.  Compounds like simple sugars (ie: glucose) are labeled with signal-emitting tracers and are injected into the patient.  A scanner records the signals these tracers emit as they journey through the body and collect in the various organs targeted for examination.  A computer then reassembles the signals into actual images that show organ and biological functions.
Sample PET images:
This patient also has a lung tumor.  Unfortunately, there's evidence that cancer is spreading.  Can you spot the metastases in his right leg?
Can you spot the lung tumor in this patient?
The ECAT software translates the scanner's signals into the images seen on this page.
Why are tumors so visible with PET?
     Remember that the patient is injected with a glucose tracer.  Although glucose is used by all cells, more glucose is used by cells with increased metabolism.  Because cancer cells are highly metabolic and use more glucose than neighboring cells, they are easily seen on the PET scan.
Can the glucose tracer harm me?
     The tracer is labeled with a minute amount of a signal-emitting radioisotope.  This radioisotope is, of course, radioactive.  The different radioisotopes used in PET scanning have such short half-lives (duration), that the PET scan often has to be performed hurriedly in order to obtain any signals at all.  In most cases, a patient can be exposed to more harmful radiation by spending a few hours at the beach than when undergoing a PET procedure.  PET patients very seldom have adverse reactions to the tracers.  
O.K. so PET is an excellent cancer diagnosis tool.  What else is it good for?
PET and Heart Disease:
     PET is the most accurate test to reveal coronary artery disease or rule out its presence.  The PET images show inadequate blood flow to the heart during stress undetected by other non-invasive cardiac tests.   PET is also routinely done to help determine treatment by either transplant or bypass surgery.  
Blood Flow                                  Metabolism
This PET scan reveals that both blood flow and metabolism are absent in a large area of the heart.  The absence of metabolism indicates that the tissue is dead, so a cardiac transplantation would be the treatment of choice.
Blood Flow                                  Metabolism
This PET scan reaveals that blood flow is markedly reduced in a large area of the heart, but metabolism is maintained.  Because metabolism indicates that the tissue is still alive, cardiac transplantation is not necessary for this patient.  However, bypass surgery would improve the function of the heart.
PET and Alzheimer's Disease:
     PET scans show a very consistent diagnostic pattern for Alzheimer's disease, where certain regions of the brain have decreased metabolism early in the disease (see arrows).  In fact, this pattern often can be recognized several years before a physician is able to confirm the diagnosis and is also used to differentiate Alzheimer's from other confounding types of dementia or depression.
PET and Parkinson's Disease:
     PET images of the brain will show if you have Parkinson's disease.  A labeled amino acid called F-DOPA is used with PET to see if your brain has a deficiency in dopamine synthesis.  If it doesn't, then you do not suffer from Parkinson's, and your tremors can be treated differently.
Pictures of the PET Scan facility at the University of Tennessee Hospital where I do my research:
Cyclotron accelerator used to create the radioactive tracers used in PET.
PET Scan Technician Kathy Hunter scans a patient.
Thank you for visiting my PET page!  I hope your visit was pleasant and informative.  If you have further questions you'd like to have answered about PET, e-mail me--I'd be happy to answer them for you.
Sincerely,
Luis Martinez
Student,
Robot arms used in mixing the different tracers for PET.
Visit this link for an interactive PET Scan demonstration:
(I highly recommend viewing the ShockWave Version)
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