Radionuclide - 1

Radionuclide - 1 - In general, nuclear medicd imaging may...

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In general, nuclear medicd imaging may be divided into three categories: 1. Conventional or planar imaging 2. Single photon emission computed tomography or SPECT 3. Positron emission tomography or PET CONVENTIONAL OR PLANAR IMAGING 7-1 A Simplified diagram of a scintillation camera. A small portton d the rediition eRvlYd kgm a point source within the object is able to transmit through a few apertures to rooeh b NalCn) crystal. Rcflcctcd r----- - High-volt* 1 + p- I rnicrosccond I I Fin1 I amplifier Photornultipl'icr ctc.p &in control - kyvV 13.18 Basic implementation of a NaI scintillation detector, showing the scintillator. light-sensitive photomultiplier tube, and support electronics. (From H. N. Wagner, Jr., ed., Principles of Nuclear Medicine. Philadelphia: Saunders, 1968. Used with ~ermission of W. R. Saunders Co.)
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0 2 0 4 0 6 0 8 0 100 Number of Protons Figure 130 All stable elements have the neutron/~roton ratio indicated bv the I For example, a neutron- rich nucleus will undergo the conversion represented schematically by n - p+ + e- + A + energy (3-1) where n, p', e- and fie represent neutron, proton, electron or beta particle, and anti-electron neutrino, respectively. On the other hand, a proton-rich nucleus may undergo the conversion P+ - n + e+ + v, + (3-2) is an electron neutrino and is the antiparticle of an electron, also known as positron. Table VII Characteristics of particles emitted by decaying unstable nuclei Rest mass Charge Energy Particle (kg) (electron charge) Nature distribution Alpha 6.6 x +2 Beta 9.0 x lo-" -I Gamma 0 0 helium nucleus monoenergetic electron continuous photon Table Vlll Characteristics of important radionuclides . . ., Photon energy Halt- Element Radionuclide Carbon Nitrogen Oxygen Fluorine Cobalt Gallium * Technetium Indium lodip Iodine Thallium Emission e + e e e Y Y Y Y Y Y Y life 20 min 10 min 124 sec 109 min 270 days 68 min 6 hrs 102 min 13 hrs 8 days 73 hrs
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Table IX Modes of radioactive decay Radioactive decay Parent Daughter nucleus Emission Alpha decay z* x $:$Y a, Y Beta decay :x :+by e- (continuous energy). v. Y Positron decay 2 x :-IY e' (continuous energy), ". Y Isomeric decay " X X Y Electron capture ?X + ec :-IY v. Y. characteristic X-rays, Internal conversion "X X Auger electrons ei (ejected), cha&terislic X-rays, Auger electrons (A = atomic mass number; Z = atomic number). B. Nuclear Activity and Half-life Radioactivity decay can be described by the mathematical expression N(t) = NO^-^' (3-3) where No and N(t) are the numbers of radionuclide at time t = 0 and t, respec- tively. The factor e-A' is the fraction of radionuclide remaining after time t and is called the decay fictor. The decay constant A is related to the half-life of the ra- dionuclide
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This note was uploaded on 01/12/2011 for the course BME 325 taught by Professor Sahak during the Fall '10 term at Northwestern.

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Radionuclide - 1 - In general, nuclear medicd imaging may...

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