RADIATION Each ionization releases approximately 33 electron volts (eV) of energy.

Material surrounding
• is a process of emitting energy. the atom absorbs the energy.
• an energy that can be transformed from one body to another across empty space.
• an energy emitted and transferred through matter, rays and particles. Compared to other types of radiation that may be absorbed, ionizing radiation deposits a large
amount of energy into a small area. In fact, the 33 eV from one ionization is more than energy
Radiation that has enough energy to move around atoms in a molecule or cause them to to disrupt the chemical bond between two carbon atoms. All ionizing radiation is capable,
vibrate, but not enough to remove electrons, is referred to as “non-ionizing radiation”. directly or indirectly, of removing electrons from most molecules, the process called
Examples of this kind of radiation include visible light and microwaves. ionization.

Radiation that falls within the “ionizing radiation” range has enough energy to remove tightly There are Three Main Kinds of Ionizing Radiation:
bound electrons from atoms, thus creating “ions”. This is the type of radiation that people
usually think of as radiation. We take advantage of its properties to generate electric power, to 1. Alpha Particles, which includes two protons and two neutrons
kill cancer cells, and in many manufacturing processes. 2. Beta Particles, which are essentially high speed electrons.
3. Gamma rays and X-rays, which are pure energy (photons).
CLASSIFICATION OF RADIATION
2. NON-IONIZING RADIATION– refers to any type of electromagnetic radiation that does
1. IONIZING RADIATION- Higher frequency ultraviolet radiation begins to have enough not carry enough energy per quantum to ionize atom or molecule--- that is, to completely
energy to break chemical bonds. X-ray and Gamma ray, which are at the upper end of remove an electron from an atom, which includes ultraviolet rays, visible light, infrared rays,
magnetic radiation, have very high frequencies (in the range of 100 billion billion Hz) and very radiowaves, etc.
short wavelength of about 1 picometer (1 trillionth of a meter).
Non-ionizing radiation does not have sufficient energy to remove electrons from atoms.
Radiation in this range has extremely high energy. It has enough energy to strip off electrons Although non-ionizing radiation has lower energy, too much of it may still affect our health,
or, in the case of a very high energy radiation, break up the nucleus of atoms. e.g. lengthy exposure to UV radiation may cause sunburn.

Ionization is the process in which a charged portion of a molecule (usually an electron) is given We Take Advantage of the Properties of Non-ionizing radiation for common Tasks:
enough energy to break away from the atom. This process results in the formation of two  Microwave radiation telecommunications and heating foods.
charged particles or ions; the “molecule” with a net positive charge and the “free electron”  Infrared radiation infrared lamps to keep food warm in restaurants.
with a negative charge.  Radiowaves broadcasting

Ionization occurs when incident ionizing radiation on passing through matter passes close Non-ionizing radiation ranges from extremely low frequency radiation that has very long
enough to an orbital electron of a target atom to transfer sufficient energy to the electron to wavelengths and frequencies in the range of 100 Hz (cycle per second) or less. Radio
remove it from the atom. frequencies have wavelengths of between 1 and 100 meters and frequencies in the range of
one million to 100 million Hz. Microwaves that we use to
heat food have wavelengths that are about one hundredth of a meter and have frequencies of BETA Particle- is smaller and much lighter but is also classified as a particle, with each
about 2.5 billion Hz. particle carrying a single, negative electric charge. The speed of this rays is much greater than
that of the Alpha particles and maybe stopped by an inch or less of aluminum. They can pass
IONIZING RADIATION IS CLASSIFIED INTO TWO (2) CATEGORIES: (2 TYPES through 1-2cm of water and human flesh.
OF IONIZING RADIATION):
2. Non- Particulate or Electromagnetic Radiation (EMR) - is in the form of waves with no
1. Particulate Radiation – are radiation in the form of particles WITH mass and/or charge that mass and/or charge, some are ionizing that travels at the speed of light and behaves like a
travels at the speed of light. Speed of light = 186,000 miles per second or 3 x 10 cm/second or photon particles.
300,000 km/second/3 x 10 m/second.
Principal Types of EMR:
Examples of Particulate Ionizing Radiation:
1. Electrons 1. X-RAY – is an Ionizing EMR with no mass and/or charge, travels at the speed of light and is
2. Protons produced outside the nucleus of an atom. (produced extra-nuclearly) –produced by machine.
3. Neutrons
2. GAMMA RAY – is an Ionizing EMR with no mass and/or charge of a very short wavelength,
Two Principal Types of Particulate Radiation: travels at the speed of light and are emitted inside the nucleus of an atom. Gamma rays are
 Alpha Particles/Radiation produced intra-nuclearly (from body→ outside); and are very penetrating and can pass right
 Beta Particles/Radiation through the body.

 ALPHA Particles – are relatively slow and heavy, each carrying a double-positive electric PARTICLES THAT PROVIDES THE BASIS FOR THE SCIENCE OF NUCLEAR
charge. Because of its relatively large size, Alpha particles travel slowly, collide readily with MEDICINE:
matter and lose their energy quickly.
Alpha Particle – is a Helium nucleus having a fast moving stable groups of two protons and
Alpha Particles are not very penetrating and maybe stopped by a sheet of Aluminum foil 0.002 two neutrons. It has a Mass number of 4 AMU and has an energy ranging from 4-10 meV
inch thick or a sheet of paper or first layer of the skin. (million-electron volt); and it has a low penetrating power, does not penetrate the dermis of
the skin.
Alpha Particle is a Helium nucleus composed of two protons and two neutrons and said to be
the single most damaging particle emitted from radioactive material, provided the radioactive Beta Particle – is a high speed or high velocity electron ejected or emitted from the Nucleus.
atom is inside the body. (Example: by swallowing or breathing, they can affect the body cells). This can penetrate from a few millimeters to 1cm beneath the skin surface.

While from inside the body, they give up energy over a relative short distance thereby these Positron – is a positively charged electron emitted from the nucleus of those atoms whose
particles can inflict more biological damage than other kind of radiation. ability is disturbed by the existence of too many protons in the nucleus (NeutronPoor).
Neutrino Particles – are hypothetic particles which Scientists have postulated to account for  The valuable information not attainable by any other means.
the difference between the total energy before and after the change of a proton to a neutron,  The awareness of the clinician as to worth of the test.
or vice-versa. This particles carries some of the excess energy away from the nucleus.  Increased accessibility.
(All of these particles play a role in Nuclear Medicine whether they are a result of the normal TO UNDERSTAND THE PRINCIPLES INVOLVED IN ALL RADIO-ISOTOPIC PROCEDURES, ONE
constituents of the atom, or are created by the radioactive atom). MUST HAVE A GOOD WORKING KNOWLEDGE OF:
1. Radiopharmaceuticals
GREAT DISCOVERIES: 2. Instrumentation
1879 - William Crookes had shown the existence of Cathode rays.
1895 – Wilhelm Conrad Roentgen – discovery of X-ray. Radioactivity - is the spontaneous disintegration of atomic nuclei by emission of subatomic
1897 – J.J. Thomson’s discovery of Electron. particles called the Alpha & Beta Particles, or an EMR called the X-rays and Gamma rays which
1896 – Antoine Henri Becquerel discovered Radioactivity. are often called as “Photons”
1898 – Thomas Alva Edison (T.A. Edison ) Fluoroscope.
- It is the result of changing Neutrons into Protons or Protons into Neutrons and oftentimes,
Neutron – first discovered/established by James Chadwick and Ernest Rutherford. subsequent emission of gamma rays from the Nucleus and possibly x-rays from the orbits.
began studying Becquerel’s results (radioactivity). And on July 1898, Marie Curie isolated new
element “Marie S. Curie Polonium". Six months later, she announced the discovery of - is the property of those atomic nuclei that spontaneously change their nucleonic
“Radium”. configuration and/or energy content. As we know that some atoms have nuclei that contains
excess energy. Such an atom like this exists in an abnormally excited state in which it is
When Rutherford was appointed at Mc Gill University in Montreal, teamed up with and characterized by an unstable nucleus.
influenced Frederick Soddy on the study of Thorium. Thorium – gives off gas and 3rd type of
ray known as the “Gamma ray”. To reach stability, the nucleus spontaneously emits particles (alpha or beta) and transform
itself into another atom in which the process is called “Radioactive Disintegration” or
Positron– first detected by Anderson at UCLA. “Radioactive Decay”. The atoms involved in this process are “Radionuclides”.

Irene Joliot-Curie & Frediric Joliot – discovered artificial Radium/Radioactivity. Factors that affect Nuclear Stability is too many. The most important is the number of
Through a series of experiments, produced new element and one of them is “Plutonium” by neutrons. When the Nucleus contains either too few or too many neutrons, the atom
Enrico Fermi undergoes radioactive decay in which the result is having the number of neutrons and protons
into a stable and proper ratio.
NEILS BOHR – theorizes his model of the atom, featuring a nucleus and a planetary electrons in
1913. RADIOACTIVE DECAY/RADIOACTIVE PROCESS:
- is the process whereby a nucleus that contains an excess of energy undergoes a
The Rapid Growth of this Specialty has been due to many Factors: transformation to a more stable state by emitting energy in the form of particles (alpha & beta)
 Simplicity and low morbidity associated with procedure. or an EMR.
TYPES OF RADIOACTIVITY 3 Processes will be described in the Beta Decay Mode/Three Classifications of Beta Decay:
A. Natural Radioactivity – radioactive materials existing in nature.  Beta Minus Decay  Beta Plus Decay  Electron Capture

Existing Radioactive Families or Radioactive Series: * In BETA MINUS or NEGATRON EMISSION, the nucleus emits Beta particles and it
Uranium, Actinium, Thorium occurs when there are too many neutrons in the nucleus. A Neutron is converted into a
proton, an electron and a neutrino.
Neptunium Other Sources of Natural Radioactivity:
Cosmic rays, Air, Water, Food, Cosmogenic Radionuclides BETA PLUS or POSITRON Decay is the emission of positively charged electron called
“Positron”. It emits Beta
3 Types of Natural Sources of Radiation According to Origin: particles which originate from the Nucleus. It occurs when there are too many protons in the
nucleus. A proton is converted into a neutron, a positron and a neutrino.
 Cosmic Radiation – radiation that comes from the sun and outer space varies with latitude
and altitude. ELECTRON CAPTURE is an alternative decay method for the Beta Plus Emission or
 Cosmogenic Radiation – are radiation produced through interaction of the cosmic rays with Positron. It is another mode
atoms in the atmosphere. of decay that occurs when there is a relative excess of Protons. This mode of decay is
 Primordial Radiation – radiation existed in the crust throughout its history. They were essentially a reverse
formed at the time of the earth’s formation. process and is also known as “Reverse Beta Decay”.
-In Electron Capture, an orbital electron (usually from K-shell) is captured by the nucleus and
B. ARTIFICIAL RADIOACTIVITY – radioactivity produced by man. combines with the proton to become a neutron.
Example: X-rays →produced by mechanical devices.
3. GAMMA DECAY. In Gamma Decay, after an electron leaves an excited state, it must
THREE BASIC MODES OF DECAY immediately return to the ground state by releasing energy in the form of Gamma ray. In some
cases, especially in high atomic number (Z) material, instead of emitting gamma ray, all energy
1.Alpha Decay – is the radioactive decay by alpha emission which is much more violent maybe transferred to one of its own orbital electron (K or L shell) which is then ejected from
process. And when it does, it losses two units of positive charge and four units of mass. In this the orbit with the process called “Internal Conversion”, while the ejected electron is called
decay mode, the nucleus emits analpha particle which is the Helium nucleus. “Conversion Electron”.
2. Beta Decay. –Radioactive Beta decay by Beta emission is much more frequently than Alpha
emission, wherein the nucleus emits a Beta particle, but only heavy radioisotopes are capable RADIONUCLIDES/RADIOISOTOPES- Maybe defined as one of two or more forms of
of alpha emission. In Beta decay mode, the nucleus is transformed to another nucleus by same element having identical chemical properties. They are atoms having essentially the
changing a proton to a neutron or vice-versa. same number of Protons and Electrons, but different number of Neutrons in the Nuclei. (An
-If the nucleus has too many neutrons (proton deficient), a neutron will be converted to a Atom having the same atomic number (Z), but different Mass number (A) is an “Isotope”.
proton. If there too many protons, a proton will be converted to a neutron.
This can be used therapeutically because the radioactive counterpart will be picked up by the 1. CYCLOTRON PRODUCTION – uses a device for accelerating some sub-atomic particles
various organs and resides within that organ to irradiate the diseased tissue. by accelerating these particles to very high speeds and then directing them towards a target
material.
RADIONUCLIDES DIFFER FROM MEDICALLY EMPLOYED DRUGS IN 2 WAYS:
The Cyclotron produces certain changes in the nucleus of the target material rendering the
1. They are not generally used to produce a pharmacological effect. material “Radioactive”
2. They all contain a radionuclide (radioisotopes) which is used for localization and/or
measurement in diagnostic procedures and for radiation effects in “Therapy”. Cyclotron – an apparatus for accelerating Protons of Deuterons to high energies by means of a
constant magnetic and an oscillating electric field.
Radionuclides /Radioisotopes – are unstable radiation substances or they present an unstable
nucleus but they behave chemically in a manner similar to its non- radioactive counterpart. Advantage of Cyclotron:
 Low Absorb dose to patient because of short Physical Half-Life.
CHARACTERISTICS OF RADIONUCLIDES
Deuteron – is the nucleus of a Deuterium atom consisting of 1 proton and 1 neutron which is
regarded as sub-atomic particle with a unit of charge and is used as bombarding particle in
1. They disintegrate (change) at a constant rate and they are with fixed Half-Life ranging from a
accelerators.
seconds to billions of years. Some naturally occurring radioisotopes such as Uranium have a
Half-Life of millions of years and that they exist on earth until now.
2. FISSION PRODUCTION - is the production of heavy nuclides wherein there is splitting of
Physical Half-Life (T ½ or Tp) – is the time required for half of the atoms/material to an atom by neutrons into two almost equal parts.
disintegrate/decay. It is often called “Radioactive Half –Life” in which it is defined as the
length of time it takes for the original number of atoms in a given radioactive sample to 3. GENERATORS - is the most common production to produce radionuclides for clinical
disintegrate or decay to ½ the original number. purposes.

MOST COMMONLY EMPLOYED NUCLIDES

They are not affected by physical and chemical state of the radioactive material, temperature,
pressure and other physical changes.
Molybdenum- 99 Mo Technetium- 99m Tc Indium- 131 In
Iodine- 131, 132 I I Gallium- 67 Ga Gallium- 68 Ga
2. They are measured in terms of the amount of radioactive substance that disintegrates in
one (1) second. Indium- 111 In Indium- 123 In Xenon- 133 Xe

3. Obtained by converting stable elements into radioactive forms by means of Nuclear

Reactors or Cyclotrons. NUCLEAR FAMILIES/ NUCLEAR SPECIES (Categories of Atomic Configuration)
PRODUCTION OF RADIONUCLIDES
Nuclide – has a specific nuclear species with a given Atomic Number (Z) and Number of
Neutrons (n). They are species of atom characterized by the charge, mass, number of its 2. Phagocytosis – is the engulfing of microorganisms or other cells and foreign particles by
nucleus and capable of existing for a measurable lifetime (usually more than 10 sec.) Phagocytes. It is used for Liver, Spleen and Bone Marrow Scanning with Radio-colloids.

1. ISOTOPES – are nuclides or radioactive material that have the same Atomic Number (Z), Phagocytes – any cell that ingest microorganisms or other cells and foreign particles.
but different in Atomic Mass Numbers.
Example: Ba I 3. Cell Sequestration – Used for Spleen scanning with damaged RBC.

2. ISOTONES – are nuclides or radioactive material that have the same number of Neutrons 4. Capillary Blockage – For Lung scanning with labeled Macroaggregate Albumin (MAA).
(n), but different in Atomic numbers (Z). They are one of the several nuclides having the same
number of Neutrons, but different number of Protons in the Nuclei. 5. Simple or Exchange Diffusion – for Bone scanning with element “Strontium”.
Example: I Xe
Note: They have the same number of Neutrons (n), but different Atomic Numbers (Z). 6. Compartmental Localization – for cardiac scanning with tagged HSA (Human Serum
Albumin), Plasma/RBC.
3. ISOBARS – are atoms that have different number of Protons and Neutrons, but same total
number of Nucleons. They are nuclides or radioactive material having the same number of
Atomic Mass (A), but different in Atomic Numbers (Z). Scintigraphy – is the production of 2D images of the distribution of radioactivity in tissues
Example:I Xe after the internal administration of a radiopharmaceutical imaging agent, wherein images
Note: They have the same Atomic Mass number (A), but different in Atomic numbers (Z). being obtained by the Scintillation Camera.

4. ISOMERS – are nuclides or radioactive materials having the same Atomic number (Z), Scintillation - an emission of spark.
same Mass number (A), same Neutrons (n), but different in physical state/energy state - flash of light.
- particle emitted in disintegration of a radioactive element
because of differences in Nucleon arrangement. They are compound exhibiting or capable of
exhibiting

Isomerism ---- the possession by two or more distinct compounds of the same molecular
formula, wherein each molecule having the same number of atoms of each element but
different in Nucleon arrangement.

METHODS OF LOCALIZATION:

1. Active Transport Localization – can be used for Thyroid Uptake Scanning with “Iodine”.