Comparably, SPECT (single-photon emission computed tomography) imaging acquires information on the concentration of radionuclides introduced to the patient's body, providing information which is typically presented as cross-sectional lices through the patient, which can be freely reformatted or manipulated to produce 3D images, just as with PET scans, a SPECT scan is often used to analyze blood flow to any given organ to help determine how well it is functioning, and for a variety of cardiac diseases.

Although SPECT and PET scans are mostly used today to image tumors and the heart, there are more and more studies and scans being done on the brain, as of late.


"The big two right now are oncology and cardiology, which are both being well accepted,"Wagner says. "The brain is the next big one that will gain support, and that's not too far in the future."

By improving diagnosis, PET scans aid physicians in selecting better courses of treatment, as well as assessing whether treatment is effective or should be changed. Recent published clinical trials have shown that in a wide array of cancers, the use of PET has caused the treatment to be changed for 15% to 50% of patients, depending on the specific clinical question. In addition, PET and PET/CT provide both the patient and their physician with a degree of certainty that is often unavailable through other imaging methods.

Since a radiotracer can go just about anywhere inside the human body, the possibilities of what can be imaged is endless, as the biology and chemistry are almost limitless. The body runs on molecules, so in theory, there are an unlimited number of tracers that can be developed. "But you have to develop the chemical synthesis, you have to pick the right ones, you have to get the financial support to develop it, you have to get the approval," as Dr.Wagner notes.

"We expect that PET will open new doors in understanding the pathologies and progression of various neurological disorders like Alzheimer's, Parkinson's, epilepsy, depression and schizophrenia," says Bernd J. Pichler, head of the Laboratory for Preclinical Imaging and Imaging Technology in the Department of Radiology at the University of Tuebingen in Germany, in an e-mail.

Why aren't more radiotracers coming onto the market?

"One big limiting factor right now is regulation by the FDA," Dr. Wagner says. "The problem is that their mindset is so linked to therapeutic drugs, that they cannot simplify things enough to make them appropriate for non-toxic drugs that are administered once to acquire information."

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