RADT 1065 Chapter 1
The Ten Commandments of Radiation Protection
(Box 1-2, pg. 12)
Becquerel
(Bq) -the unit of radioactivity.
The gray
(Gyt) is the unit of radiation absorbed dose (rad)
work
(J) — the product of force and distance
power
(P) — the quotient of work by time
Sievert
(Sv) — the unit of occupational radiation exposure and effective dose
weight
(Wt) — a force on a body caused by the pull of gravity on it; the product of mass and the acceleration of gravity on Earth: 1 lb = 4.5 N
acceleration due to gravity
(g) — objects that fall to Earth accelerate at a constant rate
momentum
(p) — the product of the mass of an object and its velocity
natural environmental radiation
*annual dose of approx. 3 mSv (unit of effective dose used to express radiation exposure of populations and radiation risk in those populations) *approx. 0.02-0.1 microgray (µGy)/hr at waist level = 0.2 milligram (mGy)/yr in the Rocky Mountains region *cosmic rays, terrestrial radiation, internally deposited radionuclides, and radon
man-made radiation
*annual dose of approx. 3.2 mSv *x-rays constitute the largest source *the annual dose has increased over the last 16 years or so because of the increased use of CT and high-level fluoro
Newton's Laws of Motion
-Inertia — a body will remain at rest or will continue to move with constant velocity in a straight line unless acted on by an external force -Force — the force (f) that acts on an object is equal to the mass (m) of the object multiplied by the acceleration (a) produced *the SI unit of force is the newton (N) -Action/reaction — for every action, there is an equal and opposite reaction
Discovery of X-Rays
-Wilhelm Roentgen was experimenting with a type of Crookes tube (Sir William Crookes-Englishman) when he discovered x-rays -November 8, 1895: fluorescence of the plate coated with barium platinocyanide that happened to be near the Crookes tube when he was experimenting with cathode rays in the tube
matter
-anything that occupies space and has mass; material substance of which physical objects are composed; atoms and molecules
atoms
-fundamental building blocks
Sources of ionizing radiation
-natural environmental radiation -man-made radiation
mass
-the quantity of matter contained in any physical object as described by its energy equivalence *measured in kg *remains unchanged regardless of its state; it can be transformed from one size, shape, and form to another (ex: block of ice to water to vapor)
List five clinical skills required by the ARRT.
1. Patient care 2. Radiation protection 3. Equipment operation 4. Image production 5. Equipment maintenance 6. Radiographic procedures
Air kerma:
1/1000 of a rad, where the rad (radiation absorbed dose) is 100 ergs of energy absorbed per gram of tissue.
What percentage of average radiation exposure to a human is attributable to medical x-rays?
51%
Barium platinocyanide:
A phosphor that glows when excited with x-rays. This is the phosphor with which Roentgen was experimenting when he discovered x-rays.
Describe the process that results in the formation of a negative ion and a positive ion?
An x-ray, for instance, interacts with an orbital electron of an atom of tissue. The electron absorbs some energy from the x-ray and is released from the atom. The electron (negative ion) and resulting atom (positive ion) are called an ion pair.
Ionizing radiation:
Any electromagnetic or particulate radiation that has sufficient energy to remove an electron from an atom.
The average level of natural environmental radiation:
Approximately 300 mrad/yr.
The acronym ALARA stands for what?
As Low As Reasonably Achievable.
The term applied to the chemistry of the body:
Biochemistry.
What are the three natural sources of whole-body radiation exposure?
Cosmic rays, terrestrial radiation, and internally deposited radionuclides.
What are the four special quantities of radiation measurement?
Exposure Air Kerma Gya (R); Absorbed Dose Gyt (rad); Effective Dose Sv (rem); and Radioactivity Bq (Ci).
Potter-Bucky grid
Introduced in 1921
What naturally occurring radiation source is responsible for radiation dose to lung tissue?
Radon 222, a gas.
Derived quantity:
Secondary quantities that are derived from a combination of one or more of the three base quantities (e.g., volume, density, and velocity).
Energy:
The ability to do work or physically influence surroundings because of position,. chemical state, or nuclear state.
The Coolidge Tube:
The first heated filament x-ray tube was developed by a physicist, William Coolidge, in 1913.
Fluoroscopy:
The production of continuous x-ray images in real time using a special x-ray imaging system, the fluoroscope, with continuous low mA. The fluoroscope was first demonstrated by Thomas Edison in 1898.
Acceleration:
The rate of change of velocity (speed and/or direction) with time.
How would you define the term "radiation"?
The transfer of energy from one area or medium to another.
What is the purpose of x-ray beam filtration?
To keep low-energy x-rays from reaching the patient. Such x-rays do not reach the image receptor. Filtration results in lower patient radiation dose.
What is the velocity of the mobile x-ray imaging system if the hospital elevator travels 20 m to the next floor in 30 s?
Velocity = Distance divided by time = 20 m/30 s = 0.67 m/s.
Describe how weight is different from mass.
Weight is determined by the force of gravity. Weight changes in value with position in a gravitational field such as that of the Earth or the moon. Mass is constant. It is independent of position and is determined by the object's energy equivalence.
A radiographer has a mass of 58 kg. What is her weight on earth? On the moon?
Weight on Earth = 58 kg × 9.8 m/s2 = 568 N. Weight on the moon = 58 kg × 1.6 m/s2 = 93 N.
Name devices designed to minimize radiation exposure to the patient and the operator.
X-ray beam filtration, x-ray beam collimation, protective apparel and barriers, fluoroscopic cumulative timer, and the protective tube housing.
How is x-ray interaction different from that seen in other types of electromagnetic radiation?
X-rays interact at the electron level or nuclear level, ionizing an atom or ejecting a nuclear particle, respectively. Lower-energy electromagnetic radiation interacts with molecules, cells, and larger objects in a way that will usually elevate the temperature of the object.
Name four examples of electromagnetic radiation.
X-rays, gamma rays, visible light, radio waves (also microwaves, infrared radiation, ultraviolet radiation).
computed tomography uses
a rotating x-ray source and detector array
fluoroscopy is usually conducted with
an x-ray tube located under the exam table *moving images
Heat is transferred by
conduction, convection, and radiation
Place the following in chronologic order of appearance: a. Digital fluoroscopy b. ASRT, c. CT, d. Radiographic grids, e. Automatic film processing,
d. Radiographic grids, b. ASRT, e. Automatic film processing, c. CT, a. Digital fluoroscopy
radiology is now considered a safe occupation protective devices and apparel developed by radiologists because of
effective radiation protection practices,
matter and energy can exist side by side
ex: moving automobile has mass and kinetic energy
energy can be transformed from one type to another
example: the electrical energy in the x-ray imaging system is used to produce electromagnetic energy, which then converts into chemical energy in the film or an electrical signal in a digital IR
radiography uses
film or a solid-state IR and usually an x-ray tube mounted from the ceiling on a track that allows the tube to be moved in any direction
It was found that restricting the x-ray beam with a sheet of lead with a hole in the center, a diaphragm, and inserting a leather or aluminum filter __________________.
improved the quality *collimation and filtration
the velocity of light
is constant and is symbolized by c:
x-ray voltages are measured in
kilovolt peak (kVp) *one kV = 1000 V of electric potential
What are the three units common to the SI and MKS systems?
length (meters, m), mass (kilograms, kg), and time (seconds, s).
x-ray currents are measured in
milliampere (mA)
The same system of units must always be used when
one is working on problems or reporting answers
Three general types of x-rays
radiography, fluoro, and CT
intensifying screens, in conjunction with glass photographic plates, helped
reduce exposure time
Mechanics is a segment of physics that deals with
statics and dynamics
to provide an x-ray beam that is satisfactory for imaging, you must
supply the x-ray tube with a high voltage and an electric current
radiology emerged as a medical specialty because of
the Snook transformer and the Coolidge tube
energy
the ability to do work *SI unit: joules; in radiology: eV (electron volt)
physics
the study of interactions of matter and energy in all their diverse forms
the motion of an object can be described by
velocity (speed) and acceleration
1895
— Roentgen discovers x-rays.
1901
— Roentgen won the first Nobel Prize in physics
1913
— The Coolidge hot-cathode x-ray tube is introduced.
1907
— The Snook transformer is developed.
protective barriers
— barrier that separates the pt and technologists
secondary quantities
— derived quantities — volume is length cubed, mass density is mass divided by volume, and velocity is length divided by time
fluoroscope
— device used to image moving anatomical structures with x-rays (Edison) *original fluorescent material was barium platinocyanide *also investigated zinc cadmium sulfide and calcium tungstate (materials used today)
radiation
— energy emitted and transferred though space
matter that intercepts radiation and absorbs part of all of it
— exposed or irradiated
special quantities
— exposure, dose, effective dose, and radioactivity
double-emulsion film
— film that has an emulsion coating on both sides of the base and a layer of super coat over each emulsion; exposure time was halved
Snook transformer
— high-voltage power supply, an interrupterless transformer, superior to other devices, capability greatly exceeded the capability of the Crookes tube, widely adopted when Coolidge tube was introduced.
always practice ALARA
— keep radiation exposures as low as reasonably achievable
protective apparel
— lead aprons and gloves
gonadal shielding
— lead shields to protect reproductive organs
every measurement has 2 parts
— magnitude and unit
base quantities
— mass, length and time
Albert Einstein
— matter and energy are interchangeable; mass-energy equivalence *E=mc² *serves as the basis for the atomic bomb, nuclear power plants, and certain nuclear medicine imaging modalities
velocity
— measure of how fast something is moving or the rate of change of its position with time *measured in meters per second (m/s)
temperature
— measured with a thermometer
filtration
— metal filters (aluminum or copper) are inserted into the x-ray tube housing so that low-energy x-rays are absorbed before they reach the pt
intensifying screens
— reduce exposure of the pt to x-rays by more than 95% as compared to radiographs taken without
collimation
— restricts the useful x-ray beam to that part of the body to be imaged; reduces scatter radiation which improves image contrast
ionizing radiation
— special type of radiation that includes x-rays *x-rays, gamma rays and ultraviolet light
cellulose nitrate
— substitute for the glass plate
potential energy
— the ability to do work by virtue of position * (ex: guillotine blade)
energy
— the ability to do work; it may be transformed from one form to another, but it cannot be created or destroyed Kinetic energy (KE) — Potential energy (PE) —
thermal energy (heat)
— the energy of motion at the molecular level; kinetic energy of molecules -> the faster the molecules of a substance are vibrating, the more thermal energy it has and the higher the temp
kinetic energy
— the energy of motion; possessed by all matter in motion *(exs: moving automobiles, windmill wheel)
chemical energy
— the energy released by a chemical reaction *(ex: that which is provided to our bodies through chemical reactions involving the food we eat)
nuclear energy
— the energy that is contained within the nucleus of an atom; we control the release (ex: nuclear power plants, controlled or the atomic bomb, uncontrolled)
heat
— the kinetic energy of the random motion of molecules *unit is the calorie — the heat necessary to raise the temperature of 1 g of water by 1ºC
Air Kerma
— the kinetic energy transferred from photons to electrons during ionization and excitation *the unit of radiation exposure or intensity *measured in joule per kilogram (J/kg) ⇢ 1 J/kg is 1 gray (Gyₐ)
convection
— the mechanical "hot" molecules in a gas or liquid from one place to another
ion pair
— the orbital electron and the atom from which it was separated
acceleration
— the rate of change of velocity with time; how quickly or slowly the velocity is changing *measured in meters per second squared (m/s²)
ionization
— the removal of an electron from an atom
thermal radiation
— the transfer of heat by the emission of infrared radiation. an x-ray tube cools primarily by radiation
conduction
— the transfer of heat through a material or by touching
electrical energy
— the work that can be done when an electron moves though and electrical potential difference (voltage) * (ex. normal household electricity)
electromagnetic energy
— type of energy used in x-ray imaging; also used for microwaves, radio waves, etc.
Coolidge tube
— vacuum tube that allowed x-ray intensity and energy to be selected separately and with great accuracy