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1. Introduction (2010)

1. Introduction (2010) - ‫‪Principles of Nuclear‬‬...

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Unformatted text preview: ‫‪Principles of Nuclear‬‬ ‫‪Medicine‬‬ ‫‪Medicine‬‬ ‫الدكتور قصي المقبل‬ ‫أستاذ مشارك- قسم الشعة والطب‬ ‫النووي‬ ‫كلية الطب-جامعة العلوم والتكنولوجيا‬ ‫الردنية‬ THE ATOM THE The nucleus has protons and The neutrons. neutrons. Protons are positively charged Protons particles. particles. Neurons are particles without charge. Electrons orbit the nucleus in Electrons precisely defined shells and subprecisely shells. Atomic Structure • A t o m is s m alle s t p a r t is pa o f e le m e nt t h a t r e t a ins c h e m ic al p r o pe r t ie s o f t h a t pe o e le m e nt • A t o m s a r e ne ut r al ( no c h a r g e ) , • b ut a r e d ivis ib le int o s m alle r e le m e nt a r y o r “f und am e nt al” p ar t ic le s N o t t o s c ale N uc le us Atom anatomy Atom Electron Proton Neutron Nucleons The Atom The The symbol “X” is given to any atom. “A” is the atomic mass number which is A” the total number of protons and neutrons. the “Z” is the atomic number which is the Z” number of protons. Atomic number defines the atom. the Atomic Shorthand Atomic Mass Element X Z A Atomic Number 131 I 53 53 Protons + 78 Neutrons = 131 Nucleons ISOTOPES ISOTOPES If proton number “Z” changes, the atom If will change (different element). will If neutron number change, the element will If be the same, but we will have isotopes. be By definition; all isotopes of a given By element have the same number of protons and differ only in the number of neutrons. and Example: 53I123, 53I125, 53I131. 53 53 Example: 53 Nuclear Families and Nomenclature 12 6 C 13 6 C 14 6 C Same number of Prot ons = I sot opes Same Radioactive Isotopes Radioactive Some isotopes are stable (nonradioactive). Some isotopes are unstable (radioactive). UNSTABILITY AND DECAY UNSTABILITY Unstable isotope seeks greater stability by Unstable some kind of radiation (decay). some Isotopes Isotopes Half-Life Half-Life The time required for half of the The radioactive isotope to undergo decay is called the half-life. called After 4 half-life's, the residual activity After would be 6.25% of original activity, which means there is no significant activity left. means Types of Radiation Types Particulate: Emission of beta particles (electrons) Emission The isotope is converted into different element. Photonic (electromagnetic) : gamma ray Photonic and x-ray and Emission of photons (gamma ray or x-ray) Emission The isotope does not change. Types of radiation Types Decay of Radioactive Isotopes (electron emission) Isotopes ν Single Step Radioactive Decay β . ν 131 I 53 53 (unstable) 131 Xe 54 (stable) Decay of Radioactive Isotopes (photon emission) (photon Photons Photons Photon is electromagnetic wave. It is part of electromagnetic spectrum. Photons are used in imaging in Photons radiology (conventional radiography and CT scanning) and in nuclear medicine. medicine. Electromagnetic Spectrum Frequency (Hz) 105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 10171018 1019 1020 Wavelength (m) Wavelength 103 102 101 10-1 10-2 10-3 10-4 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 10-10 10 Radio/TV Infrared UV X-rays Gamma Gamma Visible 7,000A 4,000A MRI Visual Imaging X-ray Imaging Electromagnetic radiation IONIZING RADIATON MICROVAVES TV, RADIO VISIBLE X-RAYS COSMIC INFRARED ULTRAVIOLET GAMMA Decreasing wave length Increasing frequency Increasing photon energy X-Ray and Gamma Ray X-Ray X-ray is emitted from outside the nucleus X-ray (electron shells). (electron Gamma ray is a photon emitted form some Gamma isotopes in the process of their decay. isotopes X-rays and gamma rays Ionizing Radiation Ionizing Radiation causes ionization of atoms and Radiation molecules. molecules. Ionization is the underlying mechanism for Ionization most radiation detectors and also is responsible for most radiobiological effects. effects. Biological Effect of Radiation Biological Why should we protect ourselves from Why radiation? radiation? Radiation Effects at the Molecular Level - Direct Action Level Direct molecular Direct absorption of energy energy DNA most DNA susceptible susceptible DNA lesions and chromosome esions hromosome aberrations DNA SİNGLE STRAND BREAK DNA DOUBLE STRAND BREAK Indirect Action-Radiolysis of Water Indirect Ionization Dissociation Free Radical Biological Damage Free Cause damage to Cause (DNA/RNA) which become nonbecome functional functional Somatic Effects Somatic Acute or early (deterministic) within days dose dependent Seen in accidents and nuclear wars Seen Affects acutely bone marrow, GI tract and Affects skin and less neurological system. Latent or delayed (stochastic). not seen for years cancer, cataract, shortened life span Principals of Radiation Protection Principals Time Distance Shielding TIME TIME • The total radiation exposure to an The individual is directly proportional to the time he is exposed to the source. • Therefore, it is wise to spend no more Therefore, time than necessary near the source of radiation. DISTANCE DISTANCE • The intensity of radiation from a source The varies inversely with the square of the distance. • Therefore, radiation workers should Therefore, maximize the distance between themselves and the radiation source. themselves Shielding Shielding • Lead is most commonly used to shield photons Lead in diagnostic imaging. Vial Shields 560 mGy/h 1 mGy/h 2 mm lead Nuclear Medicine Imaging Nuclear Technetium 99m (Tc 99m) 99m) It is the main isotope used in nuclear It medicine imaging. It is used in more than 70-80% of cases. 70-80% It emits gamma ray only. It Its half life is 6 hours. It can easily label different kind of It pharmaceuticals. pharmaceuticals. It is always given intravenously. It Radiopharmaceuticals Radiopharmaceuticals Pharmaceuticals are chemical compounds Pharmaceuticals that have pharmacokinetics but do not have pharmacological effects. They are usually labeled with Tc99m. For each organ there is certain For radiopharmaceuticals In general, nuclear medicine images the In function (physiology), not the anatomy as in conventional radiology. Pharmaceutical Pharmaceutical Different Phrmaceuticals Different Radio-labeling of Glucose with radioactive Flourine-18 The Gamma Camera The It is a device that uses gamma rays to It make an image of radiopharmaceutical distribution and uptake in patients. distribution Its crystal has a chemical propriety that if it Its is hit by a photon it will scintillate. is Nuclear Imaging Nuclear • Not enough to detect just radioactive “levels” Not or concentrations or • Need device to “map” the radioactive Need distribution distribution External Radiation Detector Gamma camera-cont.. Gamma Scintillation means light production. • The light is converted into electrical The current which then is stored in the computer as a dot. computer Scintillation of Gamma Camera Light Crystal Gamma Ray Gamma Camera Crystal (B) Gamma • NaI(Tl) • 1/4 - 1/2**” thick 1/4 – 3/8” most popular • 10- 21” in diameter – rectangular popular • Sensitive to Sensitive moisture and temperature temperature Gamma Camera Gamma Dy am ic Ac q uis it io n I m ag e s S t at ic I m ag e Mo b ile Cam e r a S t at io nar y Dual He ad Cam e r a S t at io nar y S ing le He ad Cam e r a Gamma Camera Gamma ...
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