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正电子发射断层(positrDn emision to-mography,简称PET)是七十年代发展起来的一种核医学成像诊断装置。它需要与回旋加速器(Betatron)配套使用,所以该设备价格昂贵。回旋加速器用来产生短寿命的具有正电子发射的元素(放射性同位素),如~(11)C、~(13)N、~(15)O和~(18)F等。受检者服用或注射这类放射性同位素标记的药物后,因人体内的新陈代谢或生化过程,药物会选择性地浓集于某一器官的组织中。放射性同位素在衰变时发射正电予,它的寿命小于3×10~(-10)秒,即是在它发射后的极短时间内人体内的电子发生湮没,同时产生一对γ光子。断层扫描设备在人体相应的断层面上距轴一定的圆周上轭形配置许多闪烁计数器,对γ光子进行符合测量。所
Positron emission tomography (PET) is a nuclear imaging diagnostic device developed in the seventies. It needs to be used with a cyclotron (Betatron), so the device is expensive. Cyclotrons are used to generate short-lived positron emitting elements (radioactive isotopes) such as ~ (11) C, ~ (13) N, ~ (15) O and ~ (18) F and so on. Subjects taking or injecting such radiolabeled drugs can selectively concentrate on the tissues of an organ due to the metabolism or biochemical processes in the body. Radioisotopes emit positive charges when they decay. Their lifetimes are less than 3 × 10 -10 seconds, meaning that the electrons within the body annihilate within a short time after their emission and a pair of γ-photons are generated. The tomography apparatus is provided with many scintillation counters on the corresponding fault plane of the human body on a certain circumference from the axis of the yoke to make the gamma photons conform to the measurement. The