Northwestern College
Course Syllabus
DEPARTMENT: SHS - Radiography Program
COURSE CODE: RADS.105
CREDIT HOURS: 3
Course Meeting Date/Times: M/W 1:50 p.m. - 3:40 p.m.
TITLE: Radiation Protection
INSTRUCTOR: Gary Gruenewald M.S., R.T(R)
PHONE: 708-237-5000 ext. 2825
EMAIL: ggruenewald@nc.edu
COURSE DESCRIPTION: Students are introduced to the principles of, and the reasons for, radiation protection. The responsibilities of the radiographer and protective measures for patients, personnel and the public are studied. Also covered is discussion of the sources of radiation, the units of radiation measurement, and federal and state radiation health and safety regulations.
Prerequisite: Admission into Radiography Program
REQUIRED TEXTBOOKS:
Statkiewicz Sherer, Mary Alice, Radiation Protection in Medical Radiography, 7th edition, Mosby Elsivier, 2014
Statkiewicz, Mary Alice, Radiation Protection in Medical Radiography Workbook, 7th edition, Mosby Elsivier, 2014
COURSE OBJECTIVES:
At the completion of this course, the student will be able to:
1. recognize the need for radiation protection of
both the patient and radiology personnel.
2. discuss and implement various protective means
and measures used commonly in the radiology
department.
3. understand and discuss various state and federal
radiation protection specifications.
Units of Instruction
- Introduction to Radiation Protection
- Interaction of X-Radiation with Matter
- Radiation Quantities and Units
- Dose Limits for Exposure to Ionizing Radiation
- Equipment Design for Radiation Protection
- Management of Patient Radiation Dose During Diagnostic X-Ray Procedures
- Management of Imaging Personnel Radiation Dose
- Radiation Monitoring
Unit Objectives
Found at the beginning of each chapter of the text.
- Introduction to Radiation Protection
- Interaction of X-Radiation with Matter
- Radiation Quantities and Units
- Dose Limits for Exposure to Ionizing Radiation
- Equipment Design for Radiation Protection
- Management of Patient Radiation Dose During Diagnostic X-Ray Procedures
- Management of Imaging Personnel Radiation Dose
- Radiation Monitoring
Chapter 1 - Introduction to Radiation Protection
CRITICAL THINKING QUESTIONS
Why is radiation protection necessary for both patients and imaging personnel during diagnostic
x-ray procedures?
Healthy normal biologic tissue can be injured by ionizing radiation; therefore, it is necessary to protect humans against significant and continuous exposure.
Why is patient education important in medical imaging?
Through appropriate and effective communication, patients can be made to feel they are active participants in their own health care.
Link to Flight Attendent Radiation:
http://www.youtube.com/watch?v=XpuYJ8Wnv0s
Link to Radiation Exposure on an Intercontinental Flight
http://www.youtube.com/watch?v=XuQgVGDENbU
POWERPOINT NOTES:
•These ions may cause injury in normal biologic tissue
Radiation protection is defined simply as effective measures employed by radiation workers to safeguard patients, personnel,
and the general public from unnecessary exposure to ionizing radiation.
Radiation exposure should always be kept at the lowest possible level for the general public.
When an illness or injury occurs, however, or when a specific imaging procedure for health screening purposes is necessary,
a patient may elect to assume the risk of the exposure to
A prime example of an examination in which the benefits of the exam outweigh the risks is mammography.
ionizing radiation to obtain essential diagnostic medical information.
The benefits of the exam must outweigh the risks.
ALARA - As Low As Reasonably Achievable
•An acronym synonymous with the term optimization for radiation protection (ORP).
Radiation induced cancer does not have a threshold (a dose level below which individuals would have no chance of sustaining this disease)
Patients need to be aware of the specifics of the procedure that has been ordered on them.
They must also be informed of any follow-up protocols.
Through appropriate and effective communication, patients can be made to feel that they are active participants in their own health care (autonomy).
Typically, patients are more willing to accept a risk if they perceive that the potential benefit to be obtained is greater than the risk involved.
A means by which radiographers can alleviate a patient’s fear regarding radiation exposure during their exam is through the use of
the concept of Background Equivalent Radiation Time (BERT).
This method compares the amount of radiation received from an exam to that of natural background radiation per a given time frame.
BERT is based on an annual background exposure of
3 milliseiverts (300mrem) per year.
The radiation one typically encounters is one of four types: alpha radiation, beta radiation, gamma radiation,
and x radiation. Neutron radiation is also encountered in nuclear power plants and high-altitude flights and emitted
from some industrial radioactive sources.
Radiation |
Type of Radiation |
Mass (AMU) |
Charge |
Shielding material |
Alpha |
Particle |
4 |
+2 |
Paper, skin, clothes |
Beta |
Particle |
1/1836 |
-1 |
Plastic, glass, light metals |
Gamma |
Electromagnetic Wave |
0 |
0 |
Dense metal, concrete, Earth |
Neutrons |
Particle |
1 |
0 |
Water, concrete, polyethylene, oil |
Interaction of X-Radiation with Matter - PowerPoint Notes (Chapter 2)
•The processes of interaction between radiation and matter are emphasized because a basic understanding of the subject is necessary to select technical exposure factors such as
- Peak kilovoltage (kVp)
- Milliampere-seconds (mAs)
•Peak kilovoltage (kVp) controls
- Quality, or penetrating power, of the photons in the x-ray beam and to some degree also affects the
quantity or number of photons in the beam
•Milliampere-seconds (mAs) controls
- Quantity of radiation that is directed toward a patient during a selected x-ray exposure
(mA x s = mAs)
•Radiographer
- Selects technical exposure factors that control beam quality and quantity
- Is actually responsible for the dose the patient receives during an imaging procedure
•With a suitable understanding of technical exposure factors, radiographers can select appropriate techniques that can
minimize the dose to the patient and produce optimal-quality images.
•X-rays are carriers of manmade, electromagnetic energy
- Interact with the atoms of the biologic material in the patient
- Pass through without interaction
•When x-rays interact with human tissue
- Electromagnetic energy is transferred from the x-rays to the atoms of the patient’s biologic
material (absorption), and the amount of energy absorbed per unit mass is the absorbed dose (D).
•Without absorption and the differences in the absorption properties of various body structures, it would not
be possible to produce diagnostically useful images in which different anatomic structures could be perceived and distinguished.
Benefit for the Radiographer When Patient Dose Is Minimal
•Production of primary radiation
- A diagnostic x-ray beam is produced when a stream of high-speed electrons bombards a positively charged target in a highly evacuated glass tube.
•Target (anode) composition used in general radiography
- Tungsten (a metal)
- Tungsten rhenium (a metal alloy)
- Reasons tungsten and tungsten rhenium are used as target materials
- High melting points
- High atomic numbers
Filtration of the Diagnostic X-Ray Beam
•Inherent filtration (built-in)
•Direct and indirect transmission x-ray photons
- When an x-ray beam passes through a patient, it goes through a process called attenuation.
- Some primary photons will traverse the patient without interacting (direct transmission).
These noninteracting x-ray photons reach the radiographic image receptor (e.g.,
phosphor plate, digital radiography receptor, or radiographic film).
- Other primary photons can undergo Compton and/or coherent interactions and, as a result,
may be scattered or deflected. Such photons may still traverse the patient and strike
the image receptor (indirect transmission).
The Optimum X-Ray Image:
- Scattered photons do reach the image receptor and degrade image quality.
Several methods—air gaps and radiographic grids are the most common—have
been devised to limit effects of indirectly transmitted x-ray photons.
•In conventional or digital radiography, the image receptor covers a broad enough area
that x-ray photons scattered from one part of the beam might still strike the image receptor in another area.
•Result
- The radiographic image is formed from both directly transmitted x-ray photons and indirectly
transmitted (i.e., scattered) x-ray photons.
Effect of Scatter on Radiographic Density
•Problem caused by radiographic fog
- Interferes with the radiologist’s ability to distinguish different structures in the image
•Reduction of the amount of fog produced by small-angle scatter
- Reducing the amount of tissue irradiated reduces the amount of fog produced by small-angle scatter.
Therefore, adequately collimating the x-ray beam is one way to reduce fog.
•Interaction of photons with biologic matter is random
- It is impossible to predict with certainty what will happen to a single photon when it enters human tissue.
- It is possible to predict what will happen on the average, when a large number of
photons enter the human body, and this is more than adequate to determine the characteristics
of the image that results from such numerous interactions.
•Five types of interaction between x-radiation and matter are possible.
•Only two are important in diagnostic radiology - Compton and Photoelectric
Coherent Scattering:
Coherent scattering. The incoming low-energy x-ray photon interacts with an atom and transfers its energy by
causing some or all of the electrons of the atom to vibrate momentarily. The electrons then radiate energy in
the form of electromagnetic waves. These waves nondestructively combine with one another to form a scattered
wave, which represents the scattered photon. Its wavelength and energy, or penetrating power, are the same as those of the incident photon.
Compton Scattering:
Compton scattering is responsible for most of the scattered radiation produced during a radiologic procedure.
Compton scattering results in all-directional scatter. The scatter created may be directed onward as small-angle
scatter, backward as backscatter, and to the side as sidescatter. The intensity of radiation scatter in various
directions is a major factor in planning protection for medical imaging personnel during a radiologic examination.
Photoelectric Interaction:
Photoelectric absorption. A, On encountering an inner-shell electron in the K or L shells, the incoming
x-ray photon surrenders all its energy to the electron, and the photon ceases to exist. B, The atom
responds by ejecting the electron, called a photoelectron, from its inner shell, creating a vacancy
in that shell. C, To fill the opening, an electron from an outer shell drops down to the vacated inner
shell by releasing energy in the form of a characteristic photon. Then, to fill the new vacancy in the
outer shell, another electron from the shell next farthest out drops down and another characteristic
photon is emitted, and so on until the atom regains electrical equilibrium. There is also some probability
that instead of a characteristic photon, an Auger electron will be ejected.
Additional Process That Can Occur As a Result of Photoelectric Interactions:
•Auger effect (pronounced “awzhay”)
- Pierre Victor Auger discovered effect in 1925
- Produces an Auger electron
- Radiationless effect
Probability of Occurence of Photoelectric Effect:
•Depends on
1. Energy of the incident x-ray photon
2. Atomic number (Z) of the atoms comprising the irradiated object
•Increases markedly as
1. Energy of the incident photon decreases
2. Atomic number of irradiated atom increases
Difference in Absorption Properties Between Different Body Structures:
•Make diagnostically useful images possible.
- Choose the highest-energy x-ray beam that permits adequate radiographic contrast
Use of Contrast Media to Ensure Visualization of Anatomic Structures:
•If tissues or structures are similar in atomic number and mass density, use of appropriate contrast media may be
needed to ensure visualization of those tissues or structures
Use of Annihilation Radiation in Positron Emission Tomography:
•Source of positrons
Chapter 3 - Radiation Quantities and Units
Somatic Damage = biologic damage to the body of the radiation exposed individual
1st American Radiation Fatality = Clarence Madison Dally
1900 - 1930 Skin Erythema Dose
1930 - 1950 Tolerance Dose
1950 - 1977 Maximum Permissible Dose (MPD)
1977 - 1991 Effective Dose Equivalent
1991 - Present Effective Dose (EfD)
Today's radiation standards and guidelines are based on a linear, non-threshold dose response.
RAD = radiation absorbed dose unit of absorbed dose SI = Gray
REM = radiation equivalent man unit of dose equivalence SI = Sievert
Roentgen unit of radiation exposure in air SI = C/kg
Curie unit of radioactivity SI = Becquerel
#RADS x Quality Factor = #Rems
Quality Factor for x-rays, gamma rays and beta particles = 1
Quality Factor for alpha particles = 20
Number of rad / 100 = # of Gray
Number of Gray x 100 = # of rads
EqD = Dose x radiation weighing factor
radiation weighing factor: 1 - x-rays, gamma rays and electrons 20 for alpha particles
EfD = Dose x radiation weighing factor x tissue weighing factor
Chapter 9 - Dose Limits for Exposure to Ionizing Radiation
Organizations which are responsible for evaluating the relationship between radiation EqD and induced biologic effects and
making reccomendations:
ICRP - International Comission of Radiological Protection
NCRP - National Council on Radiation Protection and Measurements
UNSCEAR - United Nations Scientific Committee on the Effects of Atomic Radiation
NAS/NRC-BEIR - National Academy of Sciences/National Research Council Committee on the Biological
Effects of Ionizing Radiation
U.S. Regulatory Agencies include:
NRC - Nuclear Regulatory Commission
Agreement States
EPA - Environmental Protection Agency
FDA - U.S. Food and Drug Administration
OSHA - Occupational Safety and Health Administration
The above agencies are responsible for enforcing radiation protection standards.
PowerPoint Chapter 10 - Equipment Design for Radiation Protection
State-of-the-Art Diagnostic and Fluoroscopic Equipment
•Has been designed with many devices that radiologists and imaging personnel can use
- To optimize the quality of the image.
- To reduce radiation exposure for patients undergoing various imaging procedures.
•Many safety features are built into x-ray-producing machines by their manufacturer to ensure radiation safety.
•Some safety features are included to meet federal regulations.
RADIATION SAFETY FEATURES OF RADIOGRAPHIC EQUIPMENT, DEVICES, AND ACCESSORIES
•Take measures to ensure that radiographic equipment operates safely to ensure radiation protection for
- Patients
- All personnel
•Every diagnostic imaging system must have a
- Protective tube housing
- Correctly functioning control panel
•A radiographic examination table and other devices and accessories must be designed to reduce patient radiation dose.
•Accessories are available to lower radiation dose for the patient.
Diagnostic-Type Protective Tube Housing
Requirements
X-Ray Tube Housing Construction
The housing enclosing the x-ray tube must be constructed so that the leakage radiation measured at a
distance of 1 m (3.3 feet) from the x-ray source does not exceed 100 mR/hr (2.58 x 10-5 C/kg per hour)
when the tube is operated at its highest voltage at the highest current that allows continuous operation
Control Panel
Radiographic Examination Table
•Must be strong
- Light-localizing variable-aperture rectangular collimator
- Aperture diaphragms
- Cones
- Cylinders
•All of these devices confine the useful, or primary, beam before it enters the area of clinical interest,
thereby limiting the quantity of body tissue irradiated. This also reduces the amount of scattered radiation
•Benefit of restricting x-ray field size to include only the anatomic structures of clinical interest
- Significant reduction in patient dose because less scatter is produced
- Improves the overall quality of the radiographic image
Light-Localizing Variable-Aperture Rectangular Collimators
- Reduction of off-focus, or stem, radiation
- Confinement of the radiographic beam
- Minimizing skin exposure to electrons produced by photon interaction with the collimator
Light-Localizing Variable-Aperture Rectangular Collimators
- The radiographer must ensure that collimation is adequate by collimating the radiographic beam so that it is no larger than
the image receptor.
Aperture Diaphragm
- Inherent
- Added
•Total filtration = Inherent + Added
Filtration for Mammographic Equipment
Filtration for General Diagnostic Radiology
Compensating Filters
•Made of aluminum, lead-acrylic, or other suitable materials
- Wedge filter
- Trough, or bilateral wedge filter
- Rare-earth screens
•Effect of faster screen-film systems on patient dose
- Availability of relative speeds from 200 to 1200
- 400-speed system standard for use in general radiography
- Reduction in radiation dose for patients
•Effect of kilovoltage on screen speed and patient dose
•Selection of film-based image receptor systems
- Comparing use of slower rare-earth film-screen image receptor systems with faster rare-earth film screen image receptor systems
- Quantum mottle effect
•Benefits of rare-earth intensifying screens
•Use of carbon as a front material in a radiographic cassette
•Use of asymmetric film emulsion and intensifying screen combinations
Radiographic Grids
Construction, Purpose, Technical Value and Impact of a Radiographic Grid on Patient Dose
Function of a Radiographic Grid
Grid Ratio and Patient Dose
Minimal Source to Skin Distance for Mobile Radiography
Requirement
Effect of Source-Skin Distance on Patient Entrance Exposure
Use of Mobile Units
RADIATION SAFETY FEATURES OF DIGITAL IMAGING EQUIPMENT, DEVICES, AND ACCESSORIES
Digital Imaging
•Conventional radiography: Analog image
- Process of producing the conventional radiographic image
- Disadvantages to the use of this technology
•Digital radiography (DR)
- Process of producing a digital radiographic image
- Components of the digital image
- Resolution (detail) of the digital radiographic image
- Composition and function of digital radiography image receptors
- Function of charge-coupled devices (CCDs)
- Access of DR images
Retake Rates in Digital Radiography
Computed Radiography (CR)
- Responsibility of the radiographer to use correct technical exposure factors the first time a patient is x-rayed to minimize radiation exposure
- Phenomenon known as “dose creep”
•Computed radiography phosphor sensitivity
•CR imaging kilovoltage flexibility
Fluoroscopic Procedures
- Patient radiation exposure rate
- Dynamic images of selected anatomic structures
- Greatest patient radiation exposure rate in diagnostic radiology
- Responsibility of physician to evaluate the need for the examination
- Benefit versus risk
- Minimizing patient exposure time
Fluoroscopic Procedures
- Size
- Normal viewing mode
- Components
- Method of operation
- Image quality
- Patient dose considerations
Fluoroscopic Procedures
- Intermittent, or Pulsed, Fluoroscopy
- Effect on patient dose
- Last-image-hold feature
- Limiting Fluoroscopic Field Size
- Benefit of fluoroscopic field size limitation
- Fluoroscopic beam length and width limitation
Fluoroscopic Procedures
- Technical Exposure Factors
- Selection of technical exposure factors for adult patients
- kVp range
- Source-to-skin distance (SSD)
- Position of the input phosphor surface of the image intensifier in relation to the patient
- Selection of Technical Exposure Factors for Children
- Percent of kVp decrease compared to an adult
- Lowering of technical exposure factors
Fluoroscopic Procedures
- Filtration
- Purpose and requirements
- Half-value layer
- Source-to-Skin Distance
- Requirement
- Cumulative Timing Device
- Requirement
- Function
- Exposure Rate Limitation
- Federal standard limit for entrance skin exposure rates
- General-purpose intensified fluoroscopic units
- Fluoroscopic units equipped with high-level control (HLC)
- Primary Protective Barrier
- Fluoroscopic Exposure Control Switch
Mobile C-Arm Fluoroscopy
Mobile C-Arm Fluoroscopy
- Source-to-end of collimator assembly distance
- Patient-image intensifier distance
•Patient dose reduction
- Entrance dose
- Position of C-arm x-ray tube
Mobile C-Arm Fluoroscopy
Cinefluorography
•Film size for dose reduction
Digital Fluoroscopy
- Methods for dose reduction
•Use of last-image-hold feature for dose reduction
High-Level-Control Interventional Procedures
High-Level-Control Interventional Procedures
- Need for ongoing education and training
- Reasons for high radiation exposures during interventional procedures
- Need for monitoring and documenting procedural fluoroscopic time
- Responsibility for documentation
- Guidelines to assist physicians in developing strategies that will enable them to fulfill their
interventional clinical objectives while controlling patient radiation dose and minimizing exposure
to occupationally exposed personnel and other assisting personnel