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 5 Radiation Monitoring
77
a measure of radiation dose occurring within different
energy ranges. Thus, a situation in which high-energy
radiation strikes the dosimeter would demonstrate a
similar reading through all three filters. Conversely,
if the dosimeter had been subjected to only very lowenergy radiation, the laser readout would be much more
pronounced in the region covered by the aluminum
filter than in the other filter-blocked portions. Somewhat more energetic radiation would enhance the
intensity of the region beneath the tin filter. This is
the manner in which radiation energy discrimination
is achieved by the OSL dosimeters. The varied energy
ranges are typically classified as “deep,” “eye,” and “shallow” and physically correlate with different penetration
depths and therefore different effective radiation energies, with “deep” being the most penetrating at a centimeter or more, “eye” at 0.3 cm, and “shallow” at the
surface, or below 0.01 cm.
In the OSL dosimeter from one manufacturer1 a
“bare” or unfiltered portion of the aluminum oxide
is used to detect dynamic exposures, that is, those
received during rapid motion between the source
of radiation and the dosimeter. Examination of the
laser-produced glow curves from this bare region
demonstrates a shift or spread in their light frequency
that can be correlated with motion (technically classifiable as a Doppler shift*).
Optically stimulated luminescence dosimeter sensitivity. The OSL dosimeter provides an accurate reading as
low as 10 µSv (1 mrem) for x-ray and gamma ray photons,
with energies ranging from 5 kiloelectron volts (keV) to
greater than 40 megaelectron volts (MeV). Because of this,
the OSL dosimeter is actually very sensitive. The OSL’s
maximum equivalent dose measurement for x-ray and
gamma ray photons is 10 Sv (1000 rem). For beta particles
with energies from 150 keV to in excess of 10 MeV, dose
measurement ranges from 100 µSv to 10 Sv (10 mrem to
1000 rem). For neutron radiation with energies of 40 keV
to greater than 35 MeV, the OSL has a more limited dose
measurement range: up to 200 µSv (20 mrem) for fast
neutrons and up to 250 µSv (25 mrem) for thermal energy
neutrons (eV energy range).
*Doppler shift refers to the apparent change in frequency of a
light wave as observer and light source move toward or away
from each other. This is similar to the increase in pitch of a
train whistle experienced by a pedestrian as the locomotive
moves toward the individual and its decrease in pitch noted by
the pedestrian as the train moves away from the person.
Control monitor. The vendor that supplies health
care facilities with OSLs provides control monitors
with each batch of dosimeters. These control monitors
serve as a basis for comparison with the remaining OSL
dosimeters after they have been returned to the company for processing. The control monitors must be kept
in a radiation-free area within an imaging facility;
therefore, their response should be minimal or zero.
After processing, if the average control monitor reading
is greater than zero, then the associated batch of OSLs
may have been exposed to radiation while in transit. To
ensure that false readings are not recorded, the control
monitor reading is reported to the health care facility.
This reading, if different from zero, must be subtracted
from each of the remaining OSLs in the batch to ensure
accuracy in exposure reporting.
Advantages of the OSL dosimeter. The OSL is light-
weight, durable, and easily worn. The OSL contains
an integrated, self-contained, preloaded packet. Colorcoding, graphic formats, and body location icons provide simple identification. This monitoring device has a
tamperproof blister packet that is not affected by heat,
moisture, and pressure. The OSL offers complete
reanalysis in the event a health care facility believes that
an error in reading the dosimeter has occurred. Because
of the OSL dosimeter’s sensitivity to as low as 10 µSv
(1 mrem) for x-ray and gamma ray photons in the
energy range 5 keV to 40 MeV, it is an excellent and
practical monitoring device for employees working in
low-radiation environments and for pregnant workers.
This device can be worn for long periods of time (up to
one year) to record occupational exposure.
Disadvantages of the OSL dosimeter. A disadvan-
tage of the OSL is that occupational radiation exposure
is recorded only in the body area where the device is
attached. In addition, if the facility does not have an
in-house reader, exposure cannot be determined on
the day of occurrence. The OSL dosimeter is not an
efficient monitoring device if it is not regularly used.
Personnel monitoring report. Results from person-
nel monitoring reports must be recorded accurately
and maintained for a review to meet state and federal
regulations. To comply with such requirements, health
care facilities use established dosimetry services. These
monitoring services process various types of personnel
dosimeters, such as the OSL dosimeter, and then supply
written personnel monitoring reports to the health
care facility (Fig. 5.4A). These statements, typically one
for each hospital department that is being monitored,
78
CHAPTER 5 Radiation Monitoring
A
CHAPTER 5 Radiation Monitoring
B
Fig. 5.4 (A) The personnel monitoring report must include the items of information shown here. (B) Modified
report showing a summary of occupational exposure. (From Landauer, Inc., Glenwood, IL.)
79
80
CHAPTER 5 Radiation Monitoring
list the deep, eye, and shallow occupational exposure
of each covered person on a monthly, quarterly, year
to date, and lifetime equivalent basis. In addition, if
requested, the total effective dose equivalent (TEDE) for
persons of interest can be supplied at year’s end. Information on the report is arranged in a series of columns.
These columns include the items listed in Box 5.2.
The cumulative columns shown in Fig. 5.4A provide
a continuous audit of actual absorbed radiation equivalent dose. These totals can be compared with allowable
values established by regulatory agencies. Whenever the
letter M appears under the current monitoring period
or in the cumulative columns, it signifies that an equivalent dose below the minimum measurable radiation
quantity was recorded during that time. The minimal
reporting levels vary according to the dosimeter type
and radiation quality as follows:
X-ray, gamma 10 µSv (1 mrem)
Beta 100 µSv (10 mrem)
Neutron 200 µSv (20 mrem) fast, 100 µSv
(10 mrem) thermal
Fetal 10 µSv (1 mrem)
Rings 300 µSv (30 mrem)
BOX 5.2 Information Found on a
Personnel Monitoring Report
1. Personal data: participant’s identification number,
name, (and may also include) birth date, and sex.
2. Type of dosimeter: P represents Luxel optically
stimulated luminescence (OSL) dosimeter* for x-ray,
beta, and gamma radiation; J represents Luxel OSL
dosimeter for x-ray, beta, gamma, and fast neutron
radiation; U represents a finger dosimeter used to
monitor x-radiation and gamma and beta radiation.
3. Radiation quality (e.g., x-rays, beta particles, neutrons,
combined radiation exposure).
4. Equivalent dose data, including current deep, eye,
and shallow recorded dose equivalents (millirem) for
the time indicated on the report (e.g., from the first
day of a given month to the last day of that month).
5. Cumulative equivalent doses for deep, eye, and shal-
low radiation exposures for specific time period, the
year to date, and lifetime radiation.
6. Inception date (month and year) that the monitoring
company began keeping dosimeter records for a
given dosimeter for an individual listed on the account
who is wearing a monitoring device.
*Luxel OSL dosimeter is manufactured by Landauer, Inc.,
Glenwood, IL.
Change in employment by radiation worker. When
changing employment, the radiation worker must
convey the data pertinent to accumulated permanent
equivalent dose to the new employer so that this
information can be placed on file. Fig. 5.4B is an
example of an appropriate summary of an occupational exposure report. A copy of such a report should
be given to the radiation worker on termination
of employment.
In health care facilities that have a well-structured
radiation safety program, personnel monitoring
reports are received and reviewed and, if necessary,
because some readings have exceeded a certain threshold value set by the facility, investigated by the radiation safety officer (RSO). Such a process should be
an integral component of the facility’s radiation
safety program. This practice is compatible with the
ALARA policy.
Direct Ion Storage Dosimeter. The personnel direct
ion storage (DIS) dosimeter is a recent development,
using electronic components developed in the 1990’s
and first applied to miniaturized personnel dosimetry
systems in the early 2000’s.2 The DIS is basically a small
(several mm3) ionization gas filled dosimeter connected
to a “solid state” device, with electrically erasable programmable read-only memory (EEPROM, or
E2PROMs). EEPROMs are used in microcomputers and
various consumer products to store small amounts of
data while allowing some memory to be erased and reprogrammed to store more data. EEPROMs are used in
voice activated greeting cards, keyless entry systems, and
various other “smart card” applications.
In the personnel dosimeter, (Fig. 5.5) when radiation
ionizes the gas in the ionization chamber, the cumulative electric charge is stored in the EEPROM and will
remain in the device indefinitely, until either added
to by additional ionization or until “read out” by the
introduction of a small control signal.3 The amount of
charge stored in the device is directly proportional to
the amount of radiation exposure produced ionization
that has occurred in the chamber. Other memory chips
within the DIS store information pertaining to the facility and the badge wearer.
The DIS dosimeter is read out through a physical
connecting device such as a universal serial bus (USB)
or via wireless connection, and the data can then be
stored electronically at the facility. However, it may
also be read out by the device wearer via a cellphone
A
Communication
Detector
Detector
battery
B
Fig. 5.5 Personnel direct ion storage dosimeter. (A) External
(unopened) view. (B) Internal (opened) view. (From Mirion Technologies, Dosimetry Services Division, Irvine, CA.)
battery
application. Thus, the individual wearer may obtain an
instantaneous readout while the facility is able to obtain their own reports, such as:
• Radiation exposure summary
• Exposure history
• Individuals who have not had their devices read
Advantages of the direct ion storage dosimeter. Ad-
vantages of the personnel DIS dosimeter include instant
access to data and no need for the institution to collect
individual dosimeters, mail them to the manufacturer
for readout, and issue new dosimeters to the individuals. DIS dosimeters are also lightweight, durable, and
can be dropped or scratched with little chance of harm
to the device.
Disadvantages of the direct ion storage dosimeter.
Radiation exposure cannot be determined if the dosimeter is not regularly used.
CHAPTER 5 Radiation Monitoring
81
RADIATION SURVEY INSTRUMENTS FOR AREA MONITORING
Radiation Detection and Measurement
Radiation monitoring instruments are used for both
individual monitoring and area monitoring.
Radiation survey instruments fall into three catego-
ries: those without a readout scale, those with a readout
scale, and those that have a readout scale and are
ionization-chamber based.
The most common of these have a Geiger–Müller
(GM) tube as their detector, the operation of which is described later in this chapter. Such instruments can be used
in multiple conditions, depending on their level of calibration (“the adjustment of an instrument to accurately read
the radiation level from a reference source”4) and associated components. The simplest version, lacking any readout scale but possibly allowing adjustable sensitivity levels,
is only a “detector” used to indicate the presence of any
radiation above background. The detector will emit a repetitive sound, whose volume or repetitive frequency is
directly associated with the intensity of radiation. Other
versions, more fully equipped, contain calibrated readout
scales, as well as audible indicators, and are typically used
either as area or room monitors or as portable survey instruments for measuring exposure rates at any location or
object of interest. These instruments, however, do not
directly supply a cumulative radiation exposure reading.
Finally, there are ionization chamber–based instruments,
which are described in more detail later in this chapter. The
most common type of survey meter that incorporates an
ionization chamber as its radiation detector is the cutie pie
(Fig. 5.6). The meter acquired this nickname sometime
during 1943 or 1944 “due to its diminutive size.”5 This instrument, when properly calibrated, is capable of measuring
radiation exposure rates over a very wide range and also
determining cumulative radiation exposure for the period
of time the instrument is irradiated. In this regard, the cutie
pie can be considered a dosimeter, as are all properly calibrated ionization chamber–based devices.
Types of Instruments
When in contact with ionizing radiation, survey
instruments respond to the charged particles that are
produced by the radiation interacting with and subsequently ionizing the gas (usually air) in the detector.
These instruments measure either the total quantity
of electrical charge resulting from the ionization of
82
Fig. 5.6 Ionization chamber–type survey meter, or “cutie pie.”
(From Victoreen, Inc., Cleveland, OH.)
CHAPTER 5 Radiation Monitoring
the gas or the rate at which the electrical charge is
produced.
Gas-filled radiation detectors serving as field instru-
ments include:
• Ionization chamber–type survey meter (“cutie pie”)
• Proportional counter
• GM survey meter
All three detect the presence of radiation and, when
properly calibrated, provide a reasonably accurate measurement. The cutie pie and the proportional counter
measure both exposure and exposure rate, whereas the
GM meter typically provides only exposure rate. Each of
these instruments has its own special use, and they are not
all equally sensitive in the detection of ionizing radiation.
Requirements
Radiation survey instruments for area monitoring
should meet the following requirements:
1. Portable, so one person can carry and operate the
device in an efficient manner for a period of time.
2. Durable enough to withstand normal use, including
routine handling that occurs during standard operating procedures.
3. Reliable; accurately assess radiation exposure, or
exposure rate, in a given area.
4. Interacts with ionizing radiation similar to how
tissue reacts, thereby permitting a more accurate
determination of tissue dose.
5. Detects all common types of ionizing radiation.
6. The energy of the radiation should not significantly
affect the response of the detector, and the direction
of the incident radiation should not affect the performance of the unit, ensuring consistency in unit
operation among individual users.
7. Cost effective; the initial cost and subsequent
maintenance expenses should be reasonably
affordable.
8. Calibrated annually to ensure accurate operation.
Gas-Filled Radiation Survey Instruments
Three types of gas-filled radiation survey instruments
exist: the ionization chamber–type survey meter (cutie
pie), the proportional counter, and the GM detector.
These instruments are individually discussed in the
paragraphs below.
Ionization Chamber–Type Survey Meter (Cutie Pie).
The ionization chamber–type survey meter (cutie
pie) is both a rate meter device (for exposure rate) used
for area surveys and an accurate integrating or cumulative exposure instrument (see Fig. 5.6). The cutie pie
measures x-radiation and gamma radiation, and, if
equipped with a suitable window, can also record beta
radiation.
Sensitivity ranges and uses. In the rate mode, the
cutie pie can measure radiation intensities ranging from
10 to several thousand microgray per hour (1 mR/h
to several thousand milliroentgens per hour); in the
integrate mode, it can sum exposures from as low as
10 µGy2a to a Gy2a (1 mR to tens of R). This device is
useful for monitoring radiographic x-ray installations
and for measuring fluoroscopic and computed tomography scatter radiation exposure rates, when exposure
timers exceed 1 second in duration. The cutie pie is
typically the instrument of choice when determining
exposure rates from patients containing therapeutic
doses of radioactive materials and when assessing the
exposure rates in radioisotope storage facilities. Finally,
the cutie pie is especially valuable when quantifying the
cumulative exposures received outside of protective
barriers associated with radiation oncology treatment
rooms.
Advantages and disadvantages. The advantages of
the cutie pie include the ability to measure a wide range
of radiation exposures within a few seconds over a
CHAPTER 5 Radiation Monitoring
83
broad expanse of radiation energies, exhibiting essentially the same response or sensitivity. The delicate
detector of the unit, however, may be considered a
disadvantage. Another caveat is that without adequate
warm-up time, its meter will drift on its most sensitive
scales and thereby potentially produce an inaccurate
reading. This device cannot be used to accurately measure exposures or exposure rates produced by typical
diagnostic procedures because the exposure times are
too short to permit the meter to respond appropriately.
Proportional Counter. The proportional counter
serves no useful purpose in diagnostic imaging because
it is generally used in a laboratory setting to detect alpha
and beta radiation and small amounts of other types
of low-level radioactive contamination. The proportional counter can discriminate between alpha and
beta particles. Because alpha radiation travels only a
short distance in air, the operator of the proportional
counter must hold the unit’s probe close to the surface
of the object being surveyed to obtain an accurate reading of the alpha radiation emitted by the object.
Geiger–Müller Survey Meter
Sensitivity and use. The Geiger–Müller (GM) sur-
vey meter serves as the primary portable radiation survey
instrument for area monitoring in nuclear medicine facilities (Fig. 5.7). With the exception of alpha particle
emission, the unit is sensitive enough to detect individual
particles (e.g., electrons emitted from certain radioactive
nuclei) or photons. Hence it can easily detect any area
contaminated by radioactive material. Because the GM
survey meter allows rapid monitoring, it can be used to
locate a lost radioactive source or low-level radioactive
contamination. By utilizing its audio mode, the GM
survey meter may also be employed to scan radiation
barriers for shielding defects.
Components. The GM survey meter has an audible
sound system (an audio amplifier and speaker) that
alerts the operator to the presence of ionizing radiation.
Metal encloses the counter’s gas-filled tube or probe,
which is the unit’s sensitive ionization chamber. When
the shield covering the probe’s sensitive chamber is
open, very low-energy x-radiation and gamma radiation, and beta radiation can be detected. Meter readings
are usually displayed in milliroentgens per hour. Because GM tubes tend to lose their calibration over time,
the instrument generally has a “check source” of a weak,
long-lived radioisotope located on one side of its external surface to verify its constancy daily.
Disadvantages. The scale reading of a GM survey
meter is not independent of the energy of the incident
photons. This means that photons of widely different
energies cause the instrument to respond quite differently and thus, unless corrected for, provide erroneous
readings. The cutie pie (ionization chamber–type survey meter), as mentioned previously, exhibits a much
flatter, or more constant, response, with varying photon
energies. In addition, the GM survey meter is likely
to saturate or jam when it is placed in a pulsed (i.e.,
noncontinuous) high-intensity radiation area (e.g., that
associated with a linear accelerator used in radiation
therapy), thereby yielding a false reading.
Fig. 5.7 Geiger–Müller (GM) survey meter.
INSTRUMENTS USED TO MEASURE X-RAY EXPOSURE
Ionization chambers can be used to measure radiation
output from both radiographic and fluoroscopic x-ray
equipment. As previously described, the cutie pie ionization chamber may be used for radiation protection surveys. If a cutie pie ionization chamber operating in “rate”
mode were placed in the primary beam during a radiographic exposure, the electrical signal produced during
the very brief (usually a fraction of a second) exposure
duration would be too small to be recorded and measured
reliably. An ionization chamber device specifically designed
84
Fig. 5.8 Ion chamber connected to an electrometer. Ionization
chamber (probe with black sensitive element containing electrodes at its end) and electrometer (in carrying case) that may
be used for measurement of x-ray machine output. Also shown
(stored in the lid of the carrying case) is a larger, more sensitive
disk-shaped ionization chamber that may be used for measurement of scattered radiation. (Photo from RadCal Corp.)
CHAPTER 5 Radiation Monitoring
for such measurement conditions consists of an ion cham-
ber connected to an electrometer, a very fast-responding
electrical instrument that can measure tiny electrical
currents with high precision and accuracy, see Fig. 5.8.
Both the ionization chamber and the electrometer
system must be precisely calibrated periodically to
meet state and federal requirements. A current listing
of accredited calibration laboratories is available from
the American Association of Physicists in Medicine.*
Medical physicists utilize ionization chambers,
connected to electrometers to perform annual standard
measurements required by state, federal, and health care
accreditation organizations for radiographic and fluoroscopic devices. These annual measurements (usually
referred to as a physics survey) include x-ray output in
Gy or mGy, fluoroscopic radiation entrance rates in
mSv/min or R/min, kVp setting accuracy, exposure timer
exactness, and half-value layers or beam quality. From
these measurements important x-ray machine performance values such as µSv/mAs or mR/mAs as a function
of selected kVp and linearity of machine radiation
output are obtained. Data that can be utilized for
determining radiation dose to patients are another
by-product of this annual survey. The ion chamber and
electrometer combination, but equipped with a specially calibrated parallel plate shaped thin window ion
chamber, sensitive to the very low x-ray energies, is normally used for similar measurements for mammography x-ray units.
*1631 Prince Street, Alexandria, VA 22314 or www.aapm.org.
S U M M A R Y
• Personnel monitoring ensures that occupational
radiation exposure levels are kept well below the
annual effective dose (EfD) limit.
• Personnel monitoring is required whenever radiation workers are likely to risk receiving 10%
or more of the annual occupational EfD limit of
50 mSv (5 rem) in any 1 year as a consequence
of their work-related activities.
• To keep radiation exposure ALARA, most health care
facilities issue dosimeter devices when personnel
could receive approximately 1% of the annual occupational EfD limit in any month, or approximately
0.5 mSv (50 mrem).
• The working habits and conditions of diagnostic
imaging personnel with respect to radiation exposure can be assessed over a designated period through
the use of the personnel dosimeter.
• Even when a protective apron is not normally required, a radiation worker should wear a personnel
monitoring device attached to the clothing on the
front of the body at collar level during routine radiographic procedures to detect any potential radiation
dose to the thyroid and the head and neck.
• During high-level radiation procedures, imaging
professionals are required to wear both a thyroid
shield and a lead apron, with the dosimeter worn
CHAPTER 5 Radiation Monitoring
85
outside the front of the protective garment at collar
level, so as to provide a reading of the approximate
equivalent dose to the eyes and the head as a whole.
• Commercially available lead aprons typically have
either 0.5 mm or 0.25 mm lead equivalent shielding.
• Pregnant radiation workers may wear a second
dosimeter beneath a lead apron to monitor the
abdomen during gestation to provide an estimate
of the equivalent dose to the embryo-fetus. Many
facilities provide pregnant radiographers with a
second dosimeter for this purpose.
• An extremity dosimeter, which is commonly a
thermoluminescent ring dosimeter (TLD) ring
dosimeter, should be used as a second monitor
when performing fluoroscopic procedures that
require the hands to be near the primary x-ray beam.
• In general, personnel dosimeters must be lightweight, portable, durable, and cost efficient.
• Two types of whole-body personnel monitoring
devices are now used. the optically stimulated luminescence (OSL) dosimeter, and direct ion storage
dosimeter (DIS).
• Reports from personnel monitoring programs must
be recorded accurately and maintained for review to
meet state and federal regulations. A record of radiation exposure is required by regulatory agencies to be
contained in the employment record of all radiation
workers.
• Personnel monitoring reports list the deep, eye,
and shallow occupational exposure of each covered
person on a monthly, quarterly, year-to-date, and
lifetime equivalent basis.
• Whenever the letter M appears under the current
monitoring period or in the cumulative columns on
a radiation monitoring report, it signifies that an
equivalent dose below the minimum measurable
radiation quantity was recorded during that time.
• In health care facilities that have a well-structured
radiation safety program, personnel monitoring
reports are received and reviewed by the Radiation
Safety Officer (RSO).
• Area monitoring can be accomplished through the
use of radiation survey instruments.
• When in contact with ionizing radiation, survey
instruments respond because of the charged particles
that are produced by the incident radiation interacting with and subsequently ionizing the gas (usually
air) in the detector. These instruments measure
either the total quantity of electrical charge resulting
from the ionization of the gas or the rate at which
the electrical charge is produced.
• Three different types of gas-filled radiation detectors
serve as field instruments, including the ionization
chamber–type survey meter (“cutie pie”), the proportional counter, and the Geiger–Müller (GM)
survey meter.
• Radiation survey instruments for area monitoring
must be durable, easy to carry, able to detect all
common types of ionizing radiation, and not be
substantially affected by the energy of the radiation
or the direction of the incident radiation.
• Ionization chambers can be used to measure the
radiation output from both radiographic and fluoroscopic x-ray equipment.
• Medical physicists use ionization chambers connected to electrometers to perform the annual standard measurements or qualified physicist survey
required by state, federal, and health care accreditation organizations for radiographic and fluoroscopic
devices.
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. How is personnel exposure monitoring accom-
plished?
2. Why should a personnel dosimeter be worn outside
a protective apron at collar level on the anterior
surface of the body during a fluoroscopic procedure?
3. What should a personnel dosimeter provide an indi-
cation of?
4. Why does a monitoring company supply control
monitors with every new batch of dosimeters?
5. What information is included in personnel monitor-
ing programs to meet state and federal regulations?
6. When changing employment, what responsibility
does a radiation worker have for their own personal
data that is pertinent to their accumulated permanent equivalent dose?
7. How sensitive to x-radiation and gamma radiation is
an OSL dosimeter?
8. What are some of the requirements that radiation
survey instruments must meet if they are to be used
for area monitoring?
9. How does a GM survey meter alert the operator to
the presence of ionizing radiation?
86
CHAPTER 5 Radiation Monitoring
10. What types of diagnostic x-ray equipment would
ionization chambers be used to calibrate?
11. How does a user of a personnel digital ionization
dosimeter obtain a readout from the device?
R E V I E W Q U E S T I O N S
1. When laser light is incident on the sensing material
in an OSL dosimeter, the material:
A. Becomes luminescent in proportion to the
amount of radiation exposure received
B. Fluoresces in proportion to the amount of radia-
tion exposure received and then emits beta particles
C. Phosphoresces in proportion to the amount of
radiation exposure received and then darkens
D. Turns ice blue in color and fluoresces in propor-
tion to the amount of radiation exposure received
2. Which of the following chemical compounds func-
tions as the sensing material in a thermoluminescent
ring dosimeter?
A. Barium sulfate
B. Calcium tungstate
C. Lithium fluoride
D. Sodium iodide
3. During routine radiographic procedures, when a
protective apron is not being worn, the primary personnel dosimeter should be attached to the clothing
on the front of the body at:
A. Collar level to approximate the location of maxi-
mal radiation dose to the thyroid and the head
and neck
B. Chest level to approximate the location of maxi-
mal radiation dose to the heart and lungs
C. Hip level to approximate the location of maximal
radiation dose to the reproductive organs
D. Waist level to approximate the location of maxi-
mal radiation dose to the small intestine
4. Which of the following requirements should radia-
tion survey instruments fulfill?
1. Instruments must be reliable so that radiation
exposure or exposure rate in a given area can
be accurately assessed.
2. Instruments must be durable enough to withstand normal use.
3. Instruments should interact with ionizing radiation similar to the way in which human
tissue reacts.
A. 1 only
12. When should a TLD ring dosimeter be worn to
measure occupational radiation exposure to the
hands?
B. 2 only
C. 3 only
D. 1, 2, and 3
5. During diagnostic imaging procedures, how may the
radiation dose to the abdomen of a pregnant radiographer be monitored during gestation?
A. It may be estimated from the radiation dose
recorded by the primary monitor worn at collar
level.
B. It may be obtained from the primary radiation
monitor worn at the abdominal level.
C. It may be obtained from a second radiation mon-
itor worn at the abdominal level.
D. It is not necessary to monitor the radiation dose
to the embryo-fetus that results from occupational exposure of a pregnant radiographer during gestation.
6. When a radiologic procedure requires the hands of a
radiation worker to be near the primary beam, the
equivalent dose to the hands of that individual may
be determined through the use of:
A. The primary personnel monitor worn at collar
level
B. A proportional counter attached to the wrist-
watch of the radiation worker
C. A TLD ring dosimeter worn on the hand of the
radiation worker
D. A cutie pie
7. Which of the following instruments is used to cali-
brate radiographic and fluoroscopic x-ray equipment?
A. Proportional counter
B. GM survey meter
C. Ionization chamber with electrometer
D. Direct ion storage dosimeter
8. For x-ray and gamma ray photons with energies
from 5 keV to greater than 40 MeV, the _______
gives an accurate reading as low as 10 µSv (1 mrem).
A. Personnel direct ion storage dosimeter
B. OSL dosimeter
C. Ionization chamber-type survey meter (cutie pie)
D. TLD ring dosimeter