PET | utmic

Positron Emission Tomography (PET)

Principle: PET uses radiotracers that undergo decay, resulting in the emission of positrons.

Positrons interact with electrons in the surrounding tissues, resulting in an annihilation reaction.

This reaction converts thesetwo particles into two 511 keV γ photons, which are

released in opposite directions. A ring detector surrounding the patient then detects these photons

simultaneously on opposite sides of the patient, and computer calculation of the site of origin in the

tissue creates an image. This quantitative imaging technique results in improved sensitivity

compared with conventional radionuclide imaging (using a gamma camera).

Advantage: 1. Its ability to study body function through biochemical functions detect disease before changes in the anatomy become apparent making it more effective in diagnosing than other imaging tests.

2. By studying metabolic functions in patients, PET imaging is able to distinguish between benign (non-cancerous) and malignant (cancerous) tumors make it a more accurate medical tool that can reduce the number of unnecessary surgeries performed due to incorrect diagnosis and staging data.

3. Is effectively used to diagnose the early stages of neurological illnesses such as epilepsy, Alzheimer’s disease, and other dementias.

4. For individuals afraid of infection in medical procedures, PET scan and infection are words that never go together.

Limitation: 1. PET scan risks caused by the radioactive component used during this procedure and radioactive substance may not be suitable for patients who are pregnant, suspect that they are pregnant, or are breast feeding.

2. The radioactive exposure in PET imaging means that there is only a limited amount of times a patient can undergo this procedure.

3. PET imaging is expensive with an average cost ranging between US$900 and $1400.

4. As PET scans require cyclotrons, an expensive machine that creates the radioisotopes that are used in the radioactive tracers required for PET imaging, PET scans are not offered in the majority of medical centers in the world. Consequently, it is a difficult treatment to receive.

PET Flow of Events

Manufacturers of Clinical PET scanner

Manufacturers of Pre-clinical PET scanner

Manufacturers of Pre-clinical and Clinical PET/CT scanner

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US FDA Approved Radiopharmaceuticals

PET in brain imaging

The greatest benefit of PET scanning is that with different specific radiotracers, one can measure blood flow, glucose metabolism, receptor density or biomolecules in the tissues of the working brain. These measurements reflect the amount of brain activity and pathophysiological changes in the various regions of the brain and allow to learn more about how the brain works. PET scanning is also used for diagnosis of brain disease, most notably because brain tumors, strokes, and neuron-damaging diseases such as Alzheimer's or Parkinson’s disease which cause great changes in brain metabolism. These changes are easily detectable with PET scans. PET is probably most useful in early cases of certain dementias (with classic examples being Alzheimer's disease and Pick's disease) where the early damage is difficult to measure with CT or MRI.

The review papers where PET is used to understand physiological chnages in CNS disease or disorders are collected. To download free review publications click on the name of the disease -

PET Procedure

To conduct the scan, a short-lived radioactive tracer isotope is injected into the living subject (usually into blood circulation). Each tracer atom has been chemically incorporated into a biologically active molecule. There is a waiting period while the active molecule becomes concentrated in tissues of interest; then the subject is placed in the imaging scanner. The molecule most commonly used for this purpose is F-18 labeled fluorodeoxyglucose (FDG), a sugar, for which the waiting period is typically an hour. During the scan, a record of tissue concentration is made as the tracer decays.

PET Isotope