Chapter 2- Radiation Types , sources, and doses received Flashcards
Two types of sources of radiation
natural and human made
Which source is always present in the environment
Natural
Which source is created by humans for specific purposes
Human made
The ability to do work—that is, to move an object against resistance.
energy
What is ionization
Removal of electron
refers to energy that passes from one location to another and can have many manifestations.
Radiation
what has no mass but does have energy
photons
Types of radiation
Mechanical vibration- ultrasound
electromagnetic wave- radio waves, microwaves, infrared, visible light ultraviolet, xrays, gamma rays
he full range of frequencies* and wavelengths* of electromagnetic waves
The Electromagnetic Spectrum
Electromagnetic waves are characterized by their:
Frequency
Wavelength
This form of radiation can travel through space in the form of a wave but can interact with matter as a particle of energy.
Dual nature of electromagnetic radiation (wave-particle duality)
name examples of ionizing radiation:
- X-rays
- Gamma rays
- Ultraviolet radiation with an energy greater than 10 eV
examples of non-ionizing radiation
- Ultraviolet radiation with energy less than 10 eV
- Visible light
- Infrared rays
- Microwaves
- Radio waves
examples of particulate radiation (another form of ionizing radiation)
- Alpha particles
- Beta particles
- Neutrons
- Protons
(x-rays, gamma rays, and high-energy ultraviolet radiation [energy higher than 10 eV]) can transfer sufficient energy to some orbital electrons to remove them from the atoms to which they were attached (the process of ionization, the foundation of the interaction of x-rays with human tissue).
Ionizing Radiation
(ultraviolet radiation [energy less than 10 eV], visible light, infrared rays, microwaves, and radio waves) does not have sufficient kinetic energy to eject electrons from atoms.
Nonionizing Radiation
Conversion of atoms to ions
Makes tissues valuable for creating images
Has the undesirable result of potentially producing some damage in the biologic material
ionization
The amount of energy transferred to electrons by ionizing radiation is the basis of the concept of :
Radiation Dose
Form of radiation that includes alpha particles, beta particles, neutrons, and protons.
Particulate Radiation
Form of radiation that includes alpha particles, beta particles, neutrons, and protons.
All these are subatomic particles that are ejected from atoms at very high speeds.
They possess sufficient kinetic energy to be capable of causing ionization by direct atomic collision.
No ionization occurs when the subatomic particles are at rest.
Particulate Radiation
which particles are less penetrating
Alpha particles are less penetrating than beta particles (fast electrons).
The amount of radiation received by a patient from diagnostic x-ray procedures may be indicated in terms of the following
Entrance skin exposure (ESE), which includes skin and glandular dose
Bone marrow dose
Gonadal dose
exposure results from the use of diagnostic x-ray machines and radiopharmaceuticals in medicine.
Medical Radiation
The two largest sources of artificial radiation are
Radiography and Fluoroscopy
Computed Tomography (CT) procedures
Accounts for approximately 2.3 mSv of the average annual individual EfD.
Medical Radiation
Consumer products containing radioactive material
Air travel
Nuclear fuel for generation of power
Atmospheric fallout from nuclear weapons testing
Nuclear power plant accidents (TMI-2 and Chernobyl)
Nuclear power plant accidents as a consequence of natural disasters (Fukushima)
Human-made (artificial) radiation
Terrestrial radiation (e.g., radon, thoron)
Cosmic radiation (solar and galactic)
Internal radiation from radioactive atoms (also called radionuclides)
Natural radiation (natural background radiation)
is a naturally occurring process in which unstable nuclei relieve that instability by various types of spontaneous nuclear emissions, one of which is the emission of charged particles.
Radioactive Decay
Alpha rays
Emitted from nuclei of very heavy elements such as uranium and plutonium during the process of radioactive decay
Each contains two protons and two neutrons.
Are simply helium nuclei (i.e., helium atoms minus their electrons)
Have a large mass (approximately four times the mass of a hydrogen atom) and a positive charge twice that of an electron
Alpha Particles
Particulate radiations vary in their ability to penetrate matter.
Alpha particles are less penetrating than beta particles (fast electrons).
They lose energy quickly as they travel a short distance in biologic matter
Considered virtually harmless.
Alpha Particles
As an internal source of radiation, they can be very damaging.
If emitted from a radioisotope deposited in the body, such as in the lungs, alpha particles can be absorbed in the relatively radiosensitive epithelial tissue and are very damaging to that tissue.
Alpha Particles
Identical to high-speed electrons except for their origin
8000 times lighter than alpha particles and have only one unit of electric charge (−1) as compared with the alpha’s two units of electric charge (+2).
Beta Rays
Will not interact as strongly with their surroundings as alpha particles do.
Capable of penetrating biologic matter to a greater depth than alpha particles with less ionization along their paths.
Beta Particles
Use
To treat superficial skin lesions in small areas
To deliver radiation boost treatments to breast tumors at tissue depths typically not exceeding 7 to 8 cm
Beta Particles
Produced in a radiation oncology treatment machine called a linear accelerator
Beta Particles
Require either millimeters of lead or multicentimeter thick slabs of wood to absorb them
For energies of less than 2 meV, either a 1-cm thick block of wood or a 1-mm thick lead shield would be sufficient for absorption.
Beta Particles
Positively charged components of an atom
Have a relatively small mass that, however, exceeds the mass of an electron by a factor of 1800
Protons
If two atoms have the same number of protons but a different number of neutrons in their nuclei, they are referred to as
isotopes.
If one of these combinations of Z protons and some neutrons leads to an unstable nucleus, then that combination is called a
radioisotope
Electrically neutral components of an atom
Have approximately the same mass as a proton
neutron
the amount of kinetic energy per unit mass that has been absorbed in a material due to its interaction with ionizing radiation.
Measured in units of milligray (mGy).
Absorbed Dose
Takes into account the type of ionizing radiation that was absorbed.
Provides an overall dose value that includes the different degrees of tissue interactions that could be caused by different types of ionizing radiation.
Measured in units of the millisievert (mSv)
Equivalent Dose
Takes into account the dose for all types of ionizing radiation (e.g., alpha, beta, gamma, x-ray) to various irradiated organs or tissues in the human body (e.g., skin, gonadal tissue, thyroid)
Effective Dose
Intended to be the best estimate of overall harm that might be produced by a given absorbed dose of radiation in human tissue.
Measured in units of the millisievert (mSv)
Effective Dose
Blood changes (e.g., measurable hematologic depression, substantial decreases within a few days in the number of lymphocytes or white blood cells that are the body’s primary defense against disease)
Radiation equivalent dose of o.25 sv
Nausea, diarrhea
EqD 1.5 sv
Erythema (diffuse redness over an area of skin after irradiation)
eqd 2.0 sv
If dose is to gonads, temporary sterility
2.5 sv
50% chance of death; lethal dose for 50% of population over 30 days (LD 50/30)
3.0 sv
death
6.0 sv
what primarily causes biologic damage
Ionizing Radiation
Result of destructive radiation interaction at the atomic level
Molecular change (has to start here)
Cellular damage
Organic damage (see Table 2.2 in textbook)
Produced by ionizing radiation while penetrating body tissues primarily by ejecting electrons from atoms composing the tissues
Biologic Damage Potential
Consumer products containing radioactive material
Air travel
Nuclear fuel for generation of power
Atmospheric fallout from nuclear weapons testing
Nuclear power plant accidents (TMI-2 and Chernobyl)
Nuclear power plant accidents as a consequence of natural disasters (Fukushima)
Human Made
