Positron emission detector

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. 

Within the radiation emission tracking techniques, there are two main variants positron emission, in which the tracer position is determined by triangulation as described in Section 2, and the "proximity" techniques, in which a gamma emitter is placed within the system of interest and its position found by measuring the relative count rates in an array of detectors. An example of the latter is computer-automated radioactive... 

The production of short-lived positron emitters has been described in section 12.2. By interaction with electrons, the positrons are annihilated and two y-ray photons of 511 keV each are emitted simultaneously in opposite directions. By measuring these photons by means of a suitable arrangement of detectors, exact localization of the radionuclides in the body is possible. This is the basis of positron emission tomography (PET), which has found broad application in nuclear medicine. The most frequently used positron emitters are listed in Table 19.2. They are preferably produced by small cyclotrons in the hospitals or nearby. 

In positron emission tomography (PET) the two SllkeV y-ray photons emitted simultaneously in opposite directions are registered by y-ray detectors, indicating that the positron decay must have occurred somewhere along the line between these two detectors. The same holds for other events of positron decay, and the radionuclide can be localized at the intersection of these lines. 

A very good review paper pertaining to tissue imaging was written by Stephen Joffe [171]. He cites 34 published articles on topics such as oxygen measurements, but the strength of the article is in the detailed comparison of NIR with other methods like X-ray, MRI, ultrasound, positron emission, thermal emission, electrical impedance, and more. He discusses the various types of equipment used, detectors, and light sources. He also gives one of the best short descriptions of time-resolved spectroscopy seen in any review article. 

Moses WW, Derenzo SE (1993). Empirical observation of performance degradation in positron emission tomographs utilizing block detectors. J Nucl Med 34 101P... 

Since the publication of this book in 2005, the growth of positron emission tomography (PET) and PET/CT modality has been phenomenal with the discovery of efficient detectors and the addition of sophisticated scanners and powerful software. Because of the vast advancement and changes in technology, and also with great appreciation of the success of the first edition, we thought a second edition of the book would be appropriate. 

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