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Unformatted text preview: Principles of Nuclear
الدكتور قصي المقبل
أستاذ مشارك- قسم الشعة والطب
كلية الطب-جامعة العلوم والتكنولوجيا
الردنية THE ATOM
THE The nucleus has protons and
neutrons. Protons are positively charged
particles. Neurons are particles without charge. Electrons orbit the nucleus in
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
the total number of protons and neutrons.
the “Z” is the atomic number which is the
number of protons. Atomic number defines
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
will change (different element).
will If neutron number change, the element will
be the same, but we will have isotopes.
be By definition; all isotopes of a given
element have the same number of protons
and differ only in the number of neutrons.
and Example: 53I123, 53I125, 53I131.
Example: 53 Nuclear Families and
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
some kind of radiation (decay).
Half-Life The time required for half of the
radioactive isotope to undergo decay is
called the half-life.
called After 4 half-life's, the residual activity
would be 6.25% of original activity, which
means there is no significant activity left.
means Types of Radiation
Emission of beta particles (electrons)
The isotope is converted into different element. Photonic (electromagnetic) : gamma ray
Emission of photons (gamma ray or x-ray)
The isotope does not change. Types of radiation
Types Decay of Radioactive
Isotopes (electron emission)
Isotopes ν Single Step Radioactive
. ν 131 I
53 (unstable) 131 Xe
(stable) Decay of Radioactive Isotopes
Photons Photon is electromagnetic wave. It is part of electromagnetic spectrum. Photons are used in imaging in
radiology (conventional radiography
and CT scanning) and in nuclear
medicine. Electromagnetic Spectrum
105 106 107 108 109 1010 1011 1012 1013 1014 1015 1016 10171018 1019 1020
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
4,000A MRI Visual
Imaging Electromagnetic radiation
RADIO VISIBLE X-RAYS COSMIC INFRARED ULTRAVIOLET GAMMA
Decreasing wave length
Increasing photon energy X-Ray and Gamma Ray
X-Ray X-ray is emitted from outside the nucleus
(electron Gamma ray is a photon emitted form some
isotopes in the process of their decay.
isotopes X-rays and
rays Ionizing Radiation
Ionizing Radiation causes ionization of atoms and
molecules. Ionization is the underlying mechanism for
most radiation detectors and also is
responsible for most radiobiological
effects. Biological Effect of Radiation
Biological Why should we protect ourselves from
radiation? Radiation Effects at the Molecular
Level - Direct Action
Level Direct molecular
energy DNA most
susceptible DNA lesions and chromosome
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
functional Somatic Effects
Somatic Acute or early (deterministic)
Seen in accidents and nuclear wars
Affects acutely bone marrow, GI tract and
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
• The total radiation exposure to an
individual is directly proportional to the
time he is exposed to the source.
• Therefore, it is wise to spend no more
time than necessary near the source of
• The intensity of radiation from a source
varies inversely with the square of the
distance. • Therefore, radiation workers should
maximize the distance between
themselves and the radiation source.
• Lead is most commonly used to shield photons
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.
It emits gamma ray only.
Its half life is 6 hours.
It can easily label different kind of
It is always given intravenously.
Radiopharmaceuticals Pharmaceuticals are chemical compounds
that have pharmacokinetics but do not
have pharmacological effects. They are usually labeled with Tc99m. For each organ there is certain
radiopharmaceuticals In general, nuclear medicine images the
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
make an image of radiopharmaceutical
distribution and uptake in patients.
distribution Its crystal has a chemical propriety that if it
is hit by a photon it will scintillate.
is Nuclear Imaging
• Not enough to detect just radioactive “levels”
• Need device to “map” the radioactive
External Radiation Detector Gamma camera-cont..
Gamma Scintillation means light production.
• The light is converted into electrical
current which then is stored in the
computer as a dot.
computer Scintillation of Gamma Camera
Light Crystal Gamma Ray Gamma Camera Crystal (B)
• 1/4 - 1/2**” thick
– 3/8” most popular • 10- 21” in diameter
– rectangular popular • Sensitive to
temperature Gamma Camera
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
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This note was uploaded on 01/21/2012 for the course PDBIO 305 taught by Professor Woods,a during the Fall '08 term at BYU.
- Fall '08