Добавил:
Sekretar
kiopkiopkiop18@yandex.ru
t.me/Prokururor I Вовсе не секретарь, но почту проверяю
Опубликованный материал нарушает ваши авторские права? Сообщите нам.
Вуз:
Предмет:
Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5196_Библиотеки_им_академика_М_И_Перельмана.pdf
CHAPTER 1 Introduction to Radiation Protection
7
A B
Fig. 1.4 (A) Patient protection. (B) Radiographer protection. Medical radiation exposure should always be
kept as low as reasonably achievable (ALARA) for protection of the patient and for imaging personnel.
does not appear to have a fixed threshold, that is, a dose
level below which a person would have no chance
of developing this disease, so the selection of exposure
factors should always follow ALARA for all medical
imaging procedures.
For many radiation regulatory agencies the ALARA
principle provides a method for comparing the amount
of radiation used in various health care facilities in a
particular region for specific imaging procedures.
Cardinal Rules of Radiation Protection
The three cardinal (basic, central) principles of radiation protection are as follows:
• Time
• Distance
• Shielding
These principles can be applied to the patient and
the radiographer. To reduce the exposure to the patient:
• Reduce the amount of the x-ray “beam-on” time.
• Use as much distance as warranted between the x-ray
tube and the patient for the examination.
• Specific area shielding devices may be required under
some circumstances.
Occupational radiation exposures, radiation expo-
sure received by the radiographer while performing
their professional responsibilities, can be minimized by
the use of these fundamental principles:
• Shorten the length of time spent in a room where
x-radiation is produced.
• Stand at the greatest distance possible from an
energized x-ray beam.
• Interpose a radiation-absorbent shielding material
between the radiographer and the source of radiation.
Responsibility for Maintaining ALARA in the Medical Industry
Both employers of radiation workers and the workers
themselves have a responsibility for radiation safety in
8
CHAPTER 1 Introduction to Radiation Protection
the medical industry. For the welfare of patients and
workers, facilities providing imaging services must
have an effective radiation safety program in place. This
requires a firm commitment to radiation safety by
all participants. It is the responsibility of the employer
to provide the necessary resources and appropriate
environment in which to execute an ALARA program.
A written policy statement describing this program
and identifying the commitment of management to
keeping all radiation exposure ALARA must be available to all employees in the workplace. In a hospital
setting, an individual called the Radiation Safety Officer
(RSO) is expressly charged by the hospital administration with being directly responsible for the execution,
enforcement, and maintenance of the ALARA program.
To determine how radiation exposure in the work-
place may be lowered, management should perform
8
periodic exposure audits.
Radiation workers with
appropriate formal education and practical training
must always function with full awareness of rules
governing the work situation. They are required to
perform their occupational practices in a manner consistent with the ALARA principle (Box 1.3). When
radiation producing devices are safely and prudently
used in the imaging of patients, the benefit of the
exposure can be maximized while the potential risk
of biologic damage is minimized.
BOX 1.3 Responsibilities for an Effective
Radiation Safety Program
Employers’ Responsibilities
• Implement and maintain an effective radiation safety
program in which to execute ALARA by providing the
following:
• Necessary resources
• Appropriate environment for ALARA program
• Make a written policy statement describing the
ALARA program and identifying the commitment of
management to keep all radiation exposure ALARA
available to all employees in the workplace.
• Perform periodic exposure audits to determine how
to lower radiation exposure in the workplace.
PATIENT PROTECTION AND PATIENT EDUCATION
Educating Patients About Imaging Procedures
Facilities that provide imaging services have a responsibility not only to ensure the highest quality of service
but also its completeness. An important aspect of
the latter is education of patients regarding imaging
procedures. Patients not only should be made cognizant of what a specific procedure involves and what
type of cooperation is required, but also they must be
informed of what needs to be done, if anything, as a
follow-up to their examination. Through appropriate
and effective communication, patients can be made to
feel that they are active participants in their own health
care (Fig. 1.5).
Risk of Imaging Procedure Versus Potential
Benefit
In general terms, risk can be defined as the probability
of injury, ailment, or death resulting from an activity.
In the medical industry with reference to the utilization
of ionizing radiation, risk is the possibility of inducing
adverse biologic effects, such as injury to the skin or
induction of cancer or a genetic defect after irradiation.
Typically, people are more willing to accept a risk if they
perceive that the potential benefit to be obtained by
themselves is greater than the risk of injury. Regarding
exposure to ionizing radiation, patients who are educated to understand the medical benefit of an imaging
procedure are more likely to suppress any radiation
phobia and be willing to assume a small chance of possible biologic damage. A significant understanding of
biologic effects associated with diagnostic radiology has
been acquired throughout the twentieth century and
beyond. The medical imaging industry currently continues to build on this knowledge. This information,
coupled with ever improving designs of medical imaging equipment and more stringent radiation safety
standards, has greatly reduced risk from imaging procedures for both patients and radiographers.
Radiation Workers’ Responsibilities
• Be aware of rules governing the workplace.
• Perform duties consistent with ALARA.
ALARA, As low as reasonably achievable.
Background Equivalent Radiation Time
Besides a normal explanation of a medical imaging
procedure, another way that radiographers can improve
understanding and reduce fear and anxiety for the
CHAPTER 1 Introduction to Radiation Protection
Fig. 1.5 Effective communication is an important part of the
patient–radiographer relationship. Patients need to be educated about imaging procedures so that they can understand
what the procedure involves and what type of cooperation is
required. The radiographer must answer patient questions
about the potential risk of radiation exposure honestly. To
create understanding and reduce fear and anxiety for the
patient, the radiographer can provide an example that compares the amount of radiation received for a specific procedure
with natural background radiation received over a given period.
patient is to use the background equivalent radiation
time (BERT) method. On occasion, a radiographer will
receive the question “Are x-rays safe?” Radiologic technologists are responsible for providing an honest and
understandable answer to the patient. An example
of this is advising patients that for normal diagnostic
examinations, such as the one they are about to undergo, there are no existing data of any unsafe effects
from the x-rays used in the examination. A second potential question about the amount of radiation that the
patient will receive from the procedure is difficult to
answer in a manner that the patient will understand
because (1) the received dose is specified in a number of
different units of measure and (2) the scientific units for
radiation dose are normally not comprehensible to a
patient. The intent of this dialog with the patient is not
to provide high scientific accuracy but to relieve anxiety
about radiation by giving an understandable and reasonably correct answer. The BERT method compares
the amount of radiation received, for example, from a
patient’s chest x-ray examination or from radiography
of any other part of the anatomy, with natural background radiation received over a specified period such
as days, weeks, months, or years (Table 1.1). This
method is also recommended by the US National Council on Radiation Protection and Measurements (NCRP).9
As an example of its usage, consider a patient who
is having a chest x-ray examination and asks the radiographer, “How much radiation will I receive from this
x-ray?” The radiographer can then respond by using
an estimation based on the comparison of radiation
received from the x-ray to natural background radiation
received, for example, over a certain number of days.
Thus the radiographer can respond, “The radiation
received from having a chest x-ray is equivalent to
what would be received while spending approximately
10 days in natural surroundings” (see Table 1.1).
BERT is based on an annual US population exposure
of approximately 3 millisieverts per year.
Using the BERT method in this context has the
following advantages:
• BERT does not imply radiation risk; it is simply a
means for comparison.
• BERT emphasizes that radiation is an innate part of
the environment.
• BERT provides an answer that is easy for the patient
to comprehend.
Patients may mistakenly think that radiation made
by humans is more dangerous than an equal amount
of natural radiation. Most patients are unaware that
most of their background radiation comes from natural
radioactivity in their own body. In summary, radiation
phobia can be greatly reduced by explaining the diagnostic radiation dose to the patient by using the BERT
method. BERT is not a radiation quantity. It is a method
of explaining radiation to the public. Its name is never
used in the explanation.
10
Increased Radiation Sensitivity of Children
Although any received radiation dose is important for
all patients, there are clear indications that children are
9
10
CHAPTER 1 Introduction to Radiation Protection
TABLE 1.1 Typical Adult Patient Effective
Dose (EfD) and Background Equivalent
Radiation Time (BERT) Values
BERT (AMOUNT OF TIME
TO RECEIVE THE SAME
Radiologic
Procedure
Dental,
intraoral
Chest
radiograph
Cervical spine 0.1 2 weeks
Thoracic spine 1.5 6 months
Lumbar spine 3.0 1 year
Upper GI series 4.5 1.5 years
Lower GI series 6.0 2 years
Skull 0.07 11 days
Hip 0.3 7 weeks
Pelvis 0.7 4 months
Abdomen 0.7 4 months
Limbs and joints
(except hip)
CT brain 2.0 1 year
CT chest 8.0 3.6 years
CT abdomen/
pelvis
CT, Computed tomography; GI, gastrointestinal; mSv,
millisievert.
Adapted from Wall BF. Patient Dosimetry Techniques in
Diagnostic Radiology. York: Institute of Physics and Engineering
in Medicine; 1988, 53, 117; Cameron JR. Are X-rays Safe?
Med Phys World, 1999;15:20; Stabin MG. Radiation Protection
and Dosimetry: An Introduction to Health Physics, New York:
Springer; 2008.
EfD
(mSv)
0.06 1 week
0.08 10 days
,0.01 ,1.5 days
10.0 4.5 years
EfD FROM NATURE)
significantly more radiation sensitive than are adults,
and that exposure to radiation early in life, at levels
found in CT and even lower, leads to a measurable increase in cancer incidence as these individuals age into
their 50s and 60s. A study from the Radiation Effects
Research Foundation published in March 2008, in
which a particular number of “n” individuals were
followed, showed that exposure in utero (n 5 2452,
where n is the number of individuals followed from
childhood exposure from the atomic bombs of Hiroshima and Nagasaki) and as a child (#6 years old, n 5
15,288) was associated with a significantly increased
risk of fatal cancer in adulthood.11 Even older children
were affected. A study of patients with scoliosis (in
which the mean age at exposure was 10.6 years, the
mean dose received was 0.11 Gy, and the number of
persons exposed was 4822) who were followed up into
adulthood found 70 cases among the exposed individuals when 35 cases were expected from comparison with
a control group.12 The National Academy of Science’s
most recent report on the biologic effects of ionizing
radiation summarized the available data as follows13:
The same radiation exposure in the first year of life for
boys produces three to four times the cancer risk as does
that exposure between the ages of 20 and 50 years. For
girls, the difference is six to eight times. For children in
general, the risk is approximately three times greater
than for adults.
Alliance for Radiation Safety in Pediatric Imaging
The Alliance for Radiation Safety in Pediatric Imaging
was founded in 2007. It is a partnership of medical
societies whose overall common purpose is to reduce
the radiation dose for pediatric patients. The Alliance’s
first goal is to raise awareness among nonradiology
users (e.g., emergency room physicians, referring physicians, orthopedists, neurosurgeons, etc.) of potentially
high radiation exposure from computed tomography.
If a child receives a dose of radiation in a CT scan where
adult protocols are used, the child, because of being
smaller in size, will receive a higher effective dose than
would an adult, but the image produced will appear
to be of acceptable quality—it will not appear overexposed, as would an image formed on an electronic image receptor. Radiologists have been aware of this for
some time, and many practices have altered their protocols for pediatric patients. However, as of 2007, many
referring physicians and nonradiology owners of CT
scanners were not aware of the problem. Since 2007 the
Alliance for Radiation Safety in Pediatric Imaging has
continued in their pursuit to raise awareness of the need
for dose reduction protocols by promoting pediatricspecific scan protocols to be used for both radiology
and nonradiology users of CT. A study was performed
to determine the general prevalence of the use of CT in
the pediatric emergency department from 2003 to 2010.
Although an increase in prevalence was demonstrated
during that period, it was also demonstrated that “in
CHAPTER 1 Introduction to Radiation Protection
11
areas where alternative nonradiation-based modalities
were options, there were decreased trends in CT usage
and increased deployment of alternative nonradiationbased modalities.”
14
Image Gently Campaign
On January 22, 2008 the Alliance initiated the Image
Gently Campaign. The campaign includes dissemina-
tion of information on pediatric CT dose reduction
among the various medical specialties that refer patients
for CT examinations or even operate their own CT
scanners. It also included the establishment of the Image Gently website. The website (www.imagegently.org)
delivers the message that CT scanning saves children’s
lives but that patient dose should be lowered by “child
sizing” the kV and mA settings, by scanning only the
indicated area (e.g., if ultrasound demonstrates a possible dermoid in the upper abdomen and a follow-up
CT is ordered, there is rarely a need to scan the entire
abdomen and pelvis) and by removing multiphase scans
from the pediatric protocol (e.g., precontrast, postcontrast, and delayed CT scans rarely add more information in children yet can double or triple the dose). The
website also contains a downloadable worksheet that
allows a medical physicist to determine the technique
factors that will ensure the pediatric dose on different
manufacturers’ scanners is substantially below that of
adult scanning doses. Input for the worksheet is a series
of measurements made on a CT scanner by a medical
physicist. With the use of these techniques, the pediatric
dose may be reduced considerably from prior near
adult values by as much as 50%, with no reduction in
image quality. Even greater dose reductions are possible
if the viewer is willing to tolerate an increase in noise,
or grainy appearance, in the image. A high-contrast
imaging situation (a more black-and-white image with
fewer shades of gray) such as bone imaging or verification of tube placement (i.e., scout view) may be successfully interpreted in the presence of increased noise.
Radiology departments or individual radiologic
technologists can “pledge” to image gently. The pledge
(see Appendix B) includes the following:
• Make the Image Gently message a priority in staff
communications each year.
• Review the protocol recommendations, and, where
necessary, implement adjustments to practice processes.
• Communicate openly with parents.
The Alliance for Radiation Safety in Pediatric Imaging consists of more than 24 medical societies, including
the American Society of Radiologic Technologists and
the American Association of Physicists in Medicine.
Therefore it represents more than 600,000 physicians,
medical physicists, and technologists. The alliance has
held summit meetings with all the major vendors of CT
equipment and has lobbied for features that encourage
the use of dose reduction techniques, more training of
vendors’ application specialists in implementation of
dose reduction techniques, and display of patient dose
for patients of all sizes.
Pause and Pulse: Image Gently in Fluoroscopy Campaign. The latest campaign of the Image Gently
Alliance was created to provide radiologic technologists a full understanding of the safe operation of
fluoroscopic devices on pediatric patients. Children
are more sensitive to radiation exposure than adults
because of the presence of many still reproducing
cells. To image kids with care, pause and child-size the
technique factors. Instead of continuous fluoroscopic
radiation, use pulsed radiation and the lowest pulse
rate possible and consider the employment of ultrasound or magnetic resonance imaging (MRI) whenever possible. The campaign, Pause and Pulse, actually
consists of three educational modules for radiologic
technologists. The areas of concentration include: a
guide to enhance radiation protection in pediatric
fluoroscopy, steps to manage radiation dose during
the examination, and steps to manage possible tissue
effects after a fluoroscopic procedure. Also, radiologic
technologists can attest to practicing Image Gently
during fluoroscopy and download a certificate displaying the education received (See Appendix B). The
Image Gently website (http://www.ImageGently.org)
serves as an excellent resource for information regarding fluoroscopy procedures and associated radiation
dose for radiologic technologists, parents, physicians,
and providers.
Image Wisely Campaign
In June 2009 The American College of Radiology
(ACR) and the Radiological Society of North America
(RSNA) formed the Joint Task Force on Adult Radiation Protection to address concerns about the observed
large increase of the general public exposure to ionizing
12
CHAPTER 1 Introduction to Radiation Protection
radiation from present day medical imaging.
15
The
Joint Task Force collaborated with the American Association of Physicists in Medicine (AAPM) and the
American Society of Radiologic Technologists (ASRT)
to create the Image Wisely Campaign, with the objectives of lowering the amount of radiation used in
medically necessary imaging studies and eliminating
unnecessary procedures.
Image Wisely offers resources and information
as guidance to radiologists, medical physicists, other
imaging practitioners, and patients. Imaging professionals can “Pledge” to Image Wisely (See Appendix B).
The Image Wisely website (http://www.ImageWisely.
org) serves as an excellent resource for information.
16
Monitoring and Reporting Radiation Dose
There is now a strong trend toward more rigorous
reporting of patient dose in all radiologic procedures.
Especially in CT and in interventional procedures,
various added measures related to patient dose recording are becoming the norm. For example, many states
now require that a log of maximum skin dose to each
patient be kept as part of the patient record for each
interventional procedure. Also, the US Food and Drug
Administration (FDA) mandates that measures of
dose in CT be available as part of the record of each
examination.
The Joint Commission, an independent, not-forprofit organization that accredits hospitals and freestanding imaging centers for reimbursement from
Medicare and Medicaid, endorses and certifies nearly
21,000 health care organizations and programs in the
United States. Most major private health care insurance
companies also accept their guidelines for reimbursement. At the present time, the Joint Commission only
requires monitoring of patient dose in CT and in interventional procedures, however, there are indications
of it also moving toward requirements for all modalities
in radiology. The Joint Commission specifies that all
imaging equipment that uses ionizing radiation be
regularly tested by qualified personnel and properly
maintained. In particular, for CT The Joint Commission
requires17:
• Annual education of staff in dose reduction techniques
• Minimum qualifications for medical physicists
• Documentation of CT radiation doses
• Management of CT protocols to minimize radiation
dose
The NEXT Program and Reference Values
Numerous groups have compiled for various procedures acceptable reference values of patient dose. These
values are usually based upon large-scale surveys of
actual measurements of x-ray machines in hospitals.
One such survey is the Nationwide Evaluation of X-ray
Trends (NEXT) project18 which is conducted by the
FDA and the Conference of Radiation Control Program
Directors.19 In addition, most state health departments
provide numerical data on systems as they exist in the
United States as of the date of the latest survey. Dose
reference levels are set at some fraction, for example,
75% of the maximum of the distribution of dose values
measured. These levels may then be used to allow individual institutions to determine where they stand with
regard to standard practices at the majority of institutions. Because practice patterns such as age and health
status of the patient population vary widely from one
institution to another, there are no mandatory prescribed values for patient exposures for different examinations and procedures.
20,21
But such data does allow
institutions to decide whether their quality assurance
programs need improvements. Another method for
setting patient dose reference levels, used by the ACR
is based upon required measurements made in plastic
phantoms as part of ACR’s accreditation programs for
limitations.
22,23
Protocols for Dose Alerts
Facilities often have protocols for alert levels. When
patient dose is predicted to or has actually substantially
exceeded normal dose levels, the staff radiologist is notified. In some cases a medical physicist may be called
upon to estimate patient doses such as effective dose,
peak skin dose, or fetal dose.
It is the technologist’s responsibility to make sure
that the radiologist and/or medical physicist has the
information needed to carry out the dose estimate.
The information needed might include patient size,
pregnancy status, technical factors used for the examination, the anatomic regions imaged, and any dose
measurements available through the electronic information system. If the examination involves prolonged
fluoroscopy, information such as the amount of time
that specific areas of the patient remained in view as
opposed to having the field of view move through
those regions is helpful in the assessment of radiation
dose.
S U M M A R Y
CHAPTER 1 Introduction to Radiation Protection
13
• Radiation is the transfer of energy from one location
to another.
• X-rays have several unique properties.
• X-rays are a form of ionizing radiation.
• Ionizing radiation has both a beneficial and a
destructive potential.
• A team approach to patient care is an organized
collaborative approach that can also have the benefit
of increased radiation safety both to patients and
directly involved members of the imaging team.
• Radiant energy can be controlled by using the knowledge of radiation-induced hazards that has been
gained over many years and by employing effective
methods to limit or eliminate those hazards.
• Radiologic technologists and radiologists should
adhere to good radiologic practices that minimize
the possibility of causing damage to healthy biologic
tissue.
• The goal of modern radiation protection programs is
twofold: to protect persons from both short-term
and long-term effects of radiation.
• To safeguard patients, personnel, and the general
public from unnecessary exposure to ionizing radiation, effective radiation protection measures should
always be employed when diagnostic imaging procedures are performed.
• Living tissue of animals and humans can be damaged
by exposure to ionizing radiation; therefore it is
necessary to safeguard against unnecessary exposure
to ionizing radiation.
• Radiation protection may be defined simply as effective measures employed by radiation workers to
safeguard patients, personnel, and the general public
from unnecessary exposure to ionizing radiation.
• There are three main types of radiation quantities to
consider: Exposure, Absorbed Dose, and Effective
Dose.
• The realized benefits of exposing patients to ionizing
radiation should far outweigh any slight chance of
inducing radiogenic cancer or any genetic defects.
• Referring physicians should justify the need for every
radiation procedure and accept basic responsibility
for protecting the patient from nonuseful radiation
exposure.
• Radiographers should select the smallest radiation
exposure settings that produce the most useful
radiographic results and should avoid errors that
result in repeated radiographic exposures.
• The three basic principles of radiation protection are
time, distance, and shielding.
• Imaging facilities must have an effective radiation
safety program in place that provides patient protection and patient education.
• A significant understanding of biologic effects of
ionizing radiation, ever improving designs of medical
x-ray equipment, and more stringent radiation safety
standards have greatly reduced the risk from imaging
procedures for both patients and radiographers.
• BERT is a method used to compare the amount of
radiation a patient receives from a radiologic procedure with natural background radiation received
over a specific period.
• Children are significantly more radiation sensitive
than are adults, and that exposure to radiation early
in life, at levels found in CT and even lower, leads to
a measurable increase in cancer incidence as these
individuals age into their 50s and 60s.
• The first goal of the Alliance for Radiation Safety in
Pediatric Imaging is to increase awareness among
nonradiology users of potentially high radiation
exposure from CT imaging.
• The Image Gently Campaign advocates lowering
patient dose by “child sizing” the kV and mA settings,
by scanning only the indicated area, and by removing
multiphase scans from pediatric protocols.
• The Pause and Pulse: Image Gently Fluoroscopy
Campaign provides radiologic technologists with a
full understanding of the safe operation of fluoroscopic devices on pediatric patients.
• The objectives of the Image Wisely Campaign are
lowering the amount of radiation used in medically
necessary imaging studies and eliminating unnecessary procedures for adults.
• In CT and in interventional procedures various
added measures related to patient dose recording
are becoming the norm. The US FDA mandates that
measures of dose in CT be available as part of the
record of each examination. At the present time,
the Joint Commission only requires monitoring of
patient dose in CT and in interventional procedures,
however, there are indications of it also moving
toward requirements for all modalities in radiology.
14
CHAPTER 1 Introduction to Radiation Protection
• Reference values for patient dose are usually based
upon large-scale surveys of actual measurement of
x-ray machines in hospitals.
• Alert levels are sometimes used when patient dose is
G E N E R A L D I S C U S S I O N Q U E S T I O N S
1. What are the consequences of ionization in the
human cell?
2. When is medical radiation exposure considered
unnecessary?
3. How can the BERT method be used to eliminate a
patient’s fears about medical radiation exposure?
4. Describe how radiographers can use the ALARA
concept in the performance of their daily responsibilities.
5. Why is a team approach of significant value in
patient care?
6. How will a patient benefit from monitoring and
reporting of radiation dose?
7. Why should the ALARA philosophy be maintained
as a main part of every health care facility’s radiation
safety program?
8. When are patients more likely to suppress any
9. On what premise is BERT based?
10. In the medical industry with reference to the radia-
11. What is the first goal of the Alliance for Radiation
12. Describe the Image Wisely Campaign, Pause and
R E V I E W Q U E S T I O N S
predicted to or has actually substantially exceeded
normal dose levels.
radiation phobia and be willing to assume a small
chance of possible biologic damage?
tion sciences, how is risk defined?
Safety in Pediatric Imaging?
Pulse: Image Gently in Fluoroscopy Campaign, and
the Image Gently Campaign.
1. A patient may choose to assume a relatively small
statistical risk of exposure to ionizing radiation for
a physician to obtain essential diagnostic medical
information when:
1. Illness occurs
2. Injury occurs
3. A specific imaging procedure for health screen-
ing purposes is called for
A. 1 and 2 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2, and 3
2. Effective measures employed by radiation workers
to safeguard patients, personnel, and the general
public from unnecessary exposure to ionizing radiation defines:
A. Diagnostic efficacy
B. Optimization
C. Radiation protection
D. Reference values
3. Which of the following is a method that can be
used to answer patients’ questions about the
amount of radiation received from a radiographic
procedure?
A. ALARA concept
B. BERT
C. PULSE
D. EPA
4. The term optimization for radiation protection (ORP)
is synonymous with which of the following?
A. As low as reasonably achievable (ALARA)
B. Background equivalent radiation time (BERT)
C. Effective dose (EfD)
D. Diagnostic efficacy (DE)
5. Monitoring and reporting of patient dose for CT and
interventional procedures can lead to:
A. An invasion of patient privacy
B. An increase in patient radiation dose
C. A reduction in patient radiation dose
D. Elimination of the need for imaging equipment
radiation safety features
6. The amount of ionization produced in the air when
ionizing radiation is present is known as:
A. Absorbed dose
CHAPTER 1 Introduction to Radiation Protection
15
B. Effective dose
C. Efficacy
D. Exposure
7. The degree to which the diagnostic study accurately
reveals the presence or absence of disease in the
patient while adhering to radiation safety guidelines
defines which of the following terms?
A. Radiation protection
B. Radiographic pathology
C. Effective diagnosis
D. Diagnostic efficacy
8. The millisievert (mSv) is equal to:
A. 1⁄10 of a sievert
B. 1⁄100 of a sievert
C. 1⁄1000 of a sievert
D. 1⁄10,000 of a sievert
9. An effective radiation safety program requires a
firm commitment to radiation safety by:
1. Facilities providing imaging services
2. Radiation workers
3. Patients
A. 1 and 2 only
B. 1 and 3 only
C. 2 and 3 only
D. 1, 2, and 3
10. If a child receives a dose of radiation in a CT scan
where adult protocols are used, the child, because of
being smaller in size, will receive a:
A. Lethal dose of radiation
B. Higher effective dose than would an adult, but
the image produced will appear to be of acceptable quality
C. Lower effective dose than would an adult, and
the image produced will be of acceptable quality
D. Severe radiation burns
2
Radiation: Types, Sources, and Doses Received
O B J E C T I V E S
After completing this chapter, the reader will be able to
perform the following:
• Define all key terms.
• Provide examples of different types of radiation.
• Draw a diagram to illustrate the electromagnetic
spectrum, and explain how the spectrum can be
divided for the purpose of studying radiation
protection.
• List the different forms of electromagnetic and
particulate radiations, and identify those forms
that are classified as ionizing radiation.
• Identify the unit of measure in which radiation
absorbed dose is most commonly specified.
• Explain the concepts of equivalent dose and effective dose, and identify the unit of measure in which
each of these radiation quantities is most often
specified.
• Explain how ionizing radiation can cause biologic
damage in body tissue.
• List and describe three sources of natural background ionizing radiation and six sources of
human-made, or artificial, ionizing radiation.
• Discuss the local and global consequences of
radiation exposure resulting from accidents in
nuclear power plants.
• Discuss the general responsibility for radiation
safety and the need for radiation protection in
medical imaging.
• Discuss the modalities used in medical imaging
that have caused an increase in radiation dose for
patients from 1980 until the present time.
C H A P T E R O U T L I N E
Radiation
Types of Radiation
The Electromagnetic Spectrum
Ionizing and Nonionizing Radiation
Particulate Radiation
K E Y T E R M S
absorbed dose
biologic damage
cellular damage
effective dose (EfD)
electromagnetic radiation
electromagnetic spectrum
electromagnetic wave
equivalent dose (EqD)
16
An Introduction to the Concept of Radiation Dose
Biologic Damage Potential
Sources of Radiation
Summary
human-made, or artificial,
radiation
ionization
isotopes
milligray (mGy)
millisievert (mSv)
natural background radiation
organic damage
particulate radiation
radiation
radiation dose
radioactive decay
radioisotope
radionuclides
radon