Positron-emission tomography (PET) Research Project


China Basin - 185 Berry Street - Lobby 6 - Suite 180

12 Hour Fasting - Drink lots of water - Take any Medications

Check in time: 8:30 A.M.

Injection time: 9:00 A.M.

Brain Scan 9:45 A.M. (For Dr. Chao's neurology sub-study)

Upper body CT scan: 11:00 A.M. (For EPIC study)

Before the testing, you will get a call from the medical center. You will call back at 619.633.2987 and given the website name and you will be given a password. You will go to the website, www.startemmi.com and enter a password given to you via a phone call and you will be directed to the web page, www.my-emmi.com/eplayer. You will enter a slid presentation and have to view and listen to the entire presentation, up to 15 minutes! If you have any problems accessing the overview of the procedure, call the Tech Support at 866.294.3664

In this procedure, you will do both, a CT and a MRI scan!


CT versus PET Scan

Chuck Buntjer - Research Study

I asked my contact at the San Francisco General Hospital, what is the difference between an MRI and a PET scan? Smruti Rahalkar replied:

To answer your question, MRI uses magnetic fields to build up series of cross sectional images of an organ. PET scan involves an injection to highlight certain parts of the body that have signs of inflammation. The reason PET scans take longer is because this injection needs to be circulated throughout the body. PET scans use radiations unlike MRI. I hope that answers your question

Chuck Buntjer - Research Study


Radiation Injection

For some reason I kept thinking about them injecting me with a dye but the technician came out with a small steel box with a lock on it. He put a cathedar into my right arm and took out some blood. He was testing for the sugar level. It had to be under 150 and mine was 106. He said the level was very good for my age!

He then put in some saline solution and opened the box. Inside was a steel cylindar with the radioactive liquid in it! He injected that into my blood stream and said I had to lie down for two hours for the cells to fill up with the liquid. He said they could tell how my system was if the cells had too much radiation in some of them. That could possibly be a health problem.

So I first did the CT for the head, then took a two hour rest and finally the PET scan that took over an hour. I went in around 8 A.M. and was finished at 1 P.M. A long day.


Positron-emission tomography (PET)

Positron-emission tomography (PET) is a nuclear medicine functional imaging technique that is used to observe metabolic processes in the body as an aid to the diagnosis of disease. The system detects pairs of gamma rays emitted China Basin - Beale Street indirectly by a positron-emitting radionuclide (tracer), which is introduced into the body on a biologically active molecule. PET Scanner

Three-dimensional images of tracer concentration within the body are then constructed by computer analysis. In modern PET-CT scanners, three-dimensional imaging is often accomplished with the aid of a CT X-ray scan performed on the patient during the same session, in the same machine.

If the biologically active molecule chosen for PET is fludeoxyglucose (FDG), an analogue of glucose, the concentrations of tracer imaged will indicate tissue metabolic activity as it corresponds to the regional glucose uptake. Use of this tracer to explore the possibility of cancer metastasis (i.e., spreading to other sites) is the most common type of PET scan in standard medical care (90% of current scans).

Less often, other radioactive tracers are used to image the tissue concentration of other types of molecules of interest. Metabolic trapping of the radioactive glucose molecule allows the PET scan to be utilized. One of the disadvantages of PET scanners is their operating cost.


How does the procedure work?

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 Schema of a PET 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.

Schema of a PET acquisition process

As the radioisotope undergoes positron emission decay (also known as positive beta decay), it emits a positron, an antiparticle of the electron with opposite charge. The emitted positron travels in tissue for a short distance (typically less than 1 mm, but dependent on the isotope, during which time it loses kinetic energy, until it decelerates to a point where it can interact with an electron. The encounter annihilates both electron and positron, producing a pair of annihilation (gamma) photons moving in approximately opposite directions. These are detected when they reach a scintillator in the scanning device, creating a burst of light which is detected by photomultiplier tubes or silicon avalanche photodiodes (Si APD). The technique depends on simultaneous or coincident detection of the pair of photons moving in approximately opposite directions (they would be exactly opposite in their center of mass frame, but the scanner has no way to know this, and so has a built-in slight direction-error tolerance). Photons that do not arrive in temporal "pairs" (i.e. within a timing-window of a few nanoseconds) are ignored.


PET Scan Exhibits

Schema of a PET Space.



Created on: 2018.07.18
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Updated on: 2018.08.14