Positron emission tomography isotopes

Positron emission tomography (PET) A medical imaging technique that helps physicians locate tumors and other growths in the body. A radioactive tracer isotope which emits a positron is incorporated into a metaholically active molecule. A scanner locates the tissues where the radioactive substance winds up. 

Positron emission tomography (PET) is another form of imaging that uses positron emitters, such as nC, 13N, 150 and 18F. These isotopes are incorporated into chemicals that are taken up by tissue. When the isotopes decay, the emitted positron reacts with a nearby electron, giving off 2 gamma rays, which are detected and an image of the tissue is created. 

Advantages and disadvantages of PET and SPECT. Positron emission tomography. The half-life of the isotopes also makes a difference to their application. 

Like the monoamine hypothesis of depression, such a simple hypothesis was appeaUng but, perhaps predictably, a Uttle too simple to be true. Further research using a technique known as positron emission tomography (PET) showed the relationship between dopamine and schizophrenia is more complex. PET detects radioactive emissions of certain isotopes these isotopes are incorporated into a molecule and injected into a patient. The machine measures the radioactivity with detectors positioned aroimd the body. PET lets researchers study the distribution of certain molecules in Uving tissue since, imUke autoradiography, the tissue is not sliced and treated chemically. The amoimt of radioactivity must be small, however, to avoid harming the human subjects. 

Studying these isotopes provides fertile ground for physicists and chemists to gain a better understanding of the properties and behavior of nuclei. This field of research also has important applications. For example, radioisotopes—radioactive isotopes—that emit certain particles are critical in some medical treatments such as radiation therapy, which is used to kill cancer cells, and positron emission tomography (PET), which is extremely useful in imaging parts of the body. 

A recent development in nuclear medicine that illustrates how advances in basic research are transformed into practical applications is positron emission tomography or PET. PET creates a three-dimensional image of a body part using positron emitting isotopes. Positrons, positively charged electrons, are a form of antimatter. Antimatter consists of particles that have the same mass as ordinary matter, but differ in charge or some other property. For example, antipro-... 

Sr was more stable in vivo but Ag was more lipophilic. These results suggest that generator-produced isotopes such as Rb-82 (T% = 75 sec) sequestered inside cryptands may be useful freely diffusible tracers for measuring blood flow by positron emission tomography. It would be more convenient to make this measurement with generator-produced isotopes than with water from cyclotron-produced oxygen-15 (Th = 122 sec). 

Mention should also be made of short-lived isotopes that are important in biotechnology and medical biochemistry. The isotopes nC, 13N, lsO, and 18F, which are positron emitters, are crucial for use in positron emission tomography (PET). 

Fluorine is a chemical element that in pure form occurs as a dimer of two fluorine atoms, F2. The fluorine atom has the ground state electron configuration ls22s22p5. There is only one stable, naturally occurring isotope of fluorine 19F. However, the radioactive isotopes 17F, 18F, and 20F are known. The inclusion of the isotope 18F (half-life 110 minutes) in bioor-ganic molecules is an important noninvasive technique used in the study of living tissue by positron emission tomography. 

The isotope fluorine-18 has a half-hfe of 109 minutes and decays by positron emission therefore molecules containing this isotope can be monitored by positron emission tomography (PET), which is a technique that is especially useful for non-invasive in vivo study of metabohc processes [41]. For example, 2-fluorodeoxyglucose is transported into cells in the same manner as glucose but, after rapid phosphorylation, further metabolism is inhibited because of the fluorine, thus effectively trapping the radiolabelled... 

With positron emission tomography (PET), a positron emitting isotope, e.g. is substituted for a stable atom without altering the chemical behaviour of the molecule. 

Another medical procedure that uses nuclear reactions is called positron emission tomography (PET), which is shown in Figure 20. PET uses radioactive isotopes that have short half-lives. An unstable isotope that contains too many protons is injected into the person. 

---