What is PET?
"PET" stands for Positron Emission Tomography. This technique allows us to measure organ function while the patient is comfortable, conscious and alert. A better name would be ART as we really are performing Annihilation Radiation Tomography, and not positron emission tomography.
PET represents a new step forward in evaluating function of internal organs and in diagnosing malignant tumors. Unlike X-rays or a CT scan, which show only structural details within the body, PET excels at determining organ function.
We are very interested in organ function because functional change, such as tissue metabolism or altered physiologic function physiologic function, often predates structural change in tissues. In oncology, PET is the only modality that can accurately image many organs of the body with a single pass to allow determination of malignancy.
PET helps determine whether a primary cancer has metastasized to other parts of the body.
What is the Value of PET
● Permits cost effective, whole-body metastatic surveys
● Avoids biopsies for low grade tumors
● Permits non-invasive differentiation of tumors from radiation necrosis
● Permits early change in course of ineffective chemotherapy
● Avoids unnecessary diagnostic and therapeutic surgeries.
Patient Management Outcomes showed that
■ PET can change staging of CA in 43% of cases*
■ PET leads to major changes in management decisions in 39%*
■ PET increases diagnostic understanding in 59%**
■ PET influenced therapy choice in 36%**
*(seltzer et al: abstract #408 snm 6/99- questionaire sent to 99 referring physicians)
**(comens et al: abstract #427 snm 6/99-questionaire before & after 153 PET scans)
What are PET Radiopharmaceuticals
● PET radiopharmaceuticals commonly incorporate short-lived radionuclides of elements encountered in nature, e.g.,
15O (t1/2 = 2 min), 13N (t1/2 = 10 min),
11C (t1/2 = 20 min), 18F (t1/2 = 110 min).
● Produce no physiological or pharmacological effects; inherently have a high degree of safety.
● No documented adverse reactions of clinical significance after hundreds of thousands of studies performed in humans worldwide.
● Radiation exposure from a PET imaging procedure is comparable to that of other Nuclear Medicine diagnostic procedures using gamma-emitting radiopharmaceuticals, many of which have been in use for decades.
● The radioactive substance used to evaluate the metabolic or physiologic process must not alter the process it is attempting to measure.
...Therefore, most substances used in PET are chemically equivalent or close analogs to naturally occurring compounds.
Many PET Radiopharmaceuticals are radiolabeled version of substances commonly present in the body, e.g., 13N-ammonia, 15O-water, 11C-acetate, 11C-methionine, and 18F-FDG
18F-FDG is the most common radiopharmaceutical used in PET worldwide.
Other PET Radiopharmaceuticals
■ 11C Compounds
■ 13N & 15O Compounds
■ 18F Compounds
■ Other Compounds
Underlying Principle of Utilizing PET Radiopharmaceuticals
● Compounds are generally chemically equivalent or close analogs to naturally occurring compounds.
● They provide functional images of the human body.
● Many PET radiopharmaceuticals are radiolabeled versions of substances commonly present in the body, e.g., 13N-ammonia, 15O-water, 11C-acetate, 11C-methionine, 18F-fluoride.