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Файл:Ординатура / Хирургия / Библиотека им академика М.И. Перельмана / Книга_5196_Библиотеки_им_академика_М_И_Перельмана.pdf
CHAPTER 15 Management of Imaging Personnel Radiation Dose
297
Fig. 15.2 (A) A lead apron protects occupationally exposed personnel from scattered radiation. (B) A lead
mobile x-ray barrier of 0.5 or 1.0 mm lead equivalent provides protection from scattered radiation. It may be
used during special procedures, in the operating room, and in cardiac units.
Depending on the energy range of the radiation for a
specific procedure, an apron containing the lead equivalent of 0.5 mm or an apron containing the minimum required lead equivalent of 0.25 mm may be sufficient for
use. The standard 0.5 mm lead equivalent apron, which
has traditionally been worn during routine fluoroscopic
procedures, weighs 3 to 7 kg. In contrast, the 0.25 mm
minimum lead equivalent apron can weigh 1 to 5 kg.2
Some physical attributes of protective lead aprons, including the percentage of x-ray attenuation at selective peak
kilovoltages (kVps), are listed in Table 15.1.
If any personnel could have the posterior surface of
their body turned toward the x-ray source during a radiologic procedure, a wraparound style apron would be
desirable to afford the best protection. When taking into
consideration both the amount of protection provided
BA
TABLE 15.1 Physical Attributes of
Protective Lead Aprons
PERCENTAGE X-RAY ATTENUATION
KILOVOLTS AT
Lead Equivalent
Thickness (mm)
0.25 1–5 97 66 51
0.50 3–7 99.9 88 75
1.00 5–12 99.9 99 94
At 100 kVp, x-ray attenuation for a 0.50-mm lead equiv-
alent apron and a 1-mm lead equivalent apron is 75%
and 94%, respectively.
Modified from Bushong SC: Radiologic science for technolo-
gists: physics, biology and protection, ed 11, St. Louis, 2017,
Elsevier.
Weight
(kg)
PEAK
50 75 100
298
CHAPTER 15 Management of Imaging Personnel Radiation Dose
by an apron and its weight, the 0.5 mm lead equivalent
apron provides a good compromise for general use.
All protective apparel must be stored correctly when
not in use to preserve the integrity of the garment. Lead
aprons should be hung on racks or draped over a bar
designed for storage to prevent unnecessary damage.
They are never to be folded or crunched up in any fashion
because this will lead to cracks or breaks in the leadimpregnated material, thereby compromising the device’s
effectiveness for protection from radiation. Regulatory
requirements state that all aprons be inspected annually
for cracks or other defects either by fluoroscopy or by
imaging the apparel with a high kVp technique.
Technical Exposure Factors
Technical exposure factors can influence the quantity of
scattered radiation produced and thereby reaching imaging personnel. For lower kVps, more mA is needed to
secure a high-quality image, and therefore more significant amounts of low-energy photons are present. These
characteristics of the x-ray beam lend themselves to the
production of increased large-angle scatter radiation.
Conversely, higher kVp techniques:
• Increase the mean energy of the photons comprising
the radiographic beam, leading to a decrease in large
angle scatter
• Require lower incident photon beam intensity (i.e.,
lower milliampere-seconds [mAs])
Therefore, with higher selected kVp values, less sidescattered radiation is available to strike imaging personnel,
and the potential EqD is reduced.
Patient Restraint
Radiographers must never stand in the primary (useful)
beam to restrain a patient during a radiographic exposure
(Fig. 15.3A). When patient restraint is necessary, me-
chanical restraining devices should be used to immobilize
the patient whenever possible. If mechanical means of
restraint are not feasible, nonoccupationally exposed persons, wearing appropriate protective apparel, are to perform this function. These individuals should be positioned so that their lead-protected torsos are not struck by
the primary, or direct, beam (Fig. 15.3B). Holding patients
may be necessary when they are unable to support themselves. For example, a weak elderly male or female patient
may be unable to stand without assistance and raise both
arms above the head for a lateral chest x-ray examination.
In this situation, a nonoccupationally exposed person
(relative or friend) equipped with a lead apron can hold
the patient in position during the exposure. A mechanical
restraining device is often used to hold an infant in the
upright position for chest images to be obtained. If such a
device is not available, the child has to be physically held
(usually by a parent) during the exposure. Pregnant
women, however, are never to be permitted to assist in
holding a patient at that time.
PROTECTION FOR PREGNANT PERSONNEL
Imaging Department Protocol
Pregnant staff members should be able to continue performing their duties without interruption of employment if they follow established radiation safety practices.
Most health care facilities have policies for protecting
pregnant personnel from radiation. Under these policies,
an imaging professional who becomes pregnant first informs her supervisor. After this voluntary declaration
has been made, the health care facility officially recognizes the pregnancy. The facility, through its radiation
safety officer:
• Provides essential counseling
• Furnishes an appropriate additional radiation dosimeter for monitoring of any possible radiation exposure
to the embryo-fetus
This additional dosimeter is to be worn at the waist
level during all radiation procedures. When a protective
lead apron is used, the dosimeter should be worn at
waist level beneath the apron. The purpose of this
additional monitor is to ensure that the monthly EqD to
the embryo-fetus does not exceed 0.5 mSv. This EqD
limit excludes:
• Medical radiation
• Natural background radiation
This practice is designed to significantly lower the
total lifetime risk of leukemia and other malignancies in
persons exposed in utero.
Acknowledgment of Counseling and Understanding of Radiation Safety Measures
After receiving radiation safety counseling, the pregnant radiologic technologist must read and sign a form
acknowledging that she has received counseling and
understands the practices to be followed to ensure the
safety of the embryo-fetus. For monitoring of pregnant
personnel, a separate monthly report is provided to
CHAPTER 15 Management of Imaging Personnel Radiation Dose
299
Fig. 15.3 (A) The radiographer should never stand in the primary (useful) beam to restrain the patient. (B) A
nonoccupationally exposed person restraining a patient during a radiographic exposure should wear a lead
apron, gloves, and thyroid shield and stand outside the primary beam.
specifically document the exposure of the worker and
the embryo-fetus. A copy of this report is sent to the
facility’s radiation safety officer.
Protective Maternity Apparel
Protective maternity apparel, when needed, should be
available for pregnant radiologists and radiographers.
Specially designed maternity protective aprons consist
of 0.5 mm lead equivalent over their entire length and
width. They have an extra 1 mm lead equivalent protective panel that runs transversely across the width of the
apron to provide added safety for the embryo-fetus.
Wraparound protective aprons of 0.5 mm lead
equivalent can also be used during pregnancy. The overall physical size of the apron must be appropriate for the
pregnant worker to ensure safety and provide reasonable comfort.
BA
Work Schedule Alteration
In accordance with ALARA guidelines, work schedules
are designed to distribute radiation exposure risk
evenly to all employees. If a declared pregnant radiographer is reassigned to a lower radiation exposure risk
area (e.g., removed from interventional fluoroscopy
and assigned to general radiography), then the remaining radiographers in the higher-risk area who
must fill in can be subject to increased risk. Therefore,
the declared pregnant radiographer does not necessarily need to be reassigned to a lower radiation exposure
position as a direct consequence of a declared pregnancy. However, it is imperative that, while remaining
in her current position, the EqD to the embryo-fetus
does not exceed the NCRP recommended monthly
EqD limit of 0.5 mSv or a total of 5.0 mSv during the
entire pregnancy.
300
CHAPTER 15 Management of Imaging Personnel Radiation Dose
BASIC PRINCIPLES OF RADIATION PROTECTION FOR PERSONNEL EXPOSURE REDUCTION
As previously stated, the three basic principles of radiation protection are:
• Time
• Distance
• Shielding
Occupational radiation exposure of imaging personnel
can be minimized by the use of these cardinal principles.
Time
The amount of radiation a worker receives at a particular
location is directly proportional to the length of time the
individual is in the path of ionizing radiation. During
fluoroscopy, the reduced exposure time will decrease both:
• Patient exposure
• Personnel exposure
For this reason, fluoroscopic x-ray units are equipped
with 5 minute timers to alert the radiologist or other
authorized equipment operator that a specific amount
of time has elapsed. To minimize radiation exposure, a
radiographer should be present in a fluoroscopy room
only when needed to perform appropriate patient care
and to fulfill the duties associated with the procedure.
Otherwise, the radiographer should remain behind a
protective barrier.
Distance
Distance is the most effective means of protection from
ionizing radiation. Because there is a significant decrease in the radiation level as a consequence of the
dispersion or spread of the radiation beam with distance, imaging personnel will receive significantly less
radiation exposure by standing farther away from a
source of radiation.
More
distance
2 d
3 d
4 d
Fig. 15.4 As the distance between the source of radiation and
any given measurement point increases, radiation intensity
(quantity) measured at that point decreases by the square of
the relative change in distance between the new location and
the old.
Less
intensity
(quantity of
radiation)
1
⁄4 intensity
1
⁄9 intensity
1
⁄16 intensity
To be more explicit, as the distance between the radiation source and a measurement point increases, the
intensity, or quantity of radiation measured at the more
distant position decreases by the square of the ratio of
the original distance from the source to the new distance
from the source (Fig. 15.4). This lowering of radiation
intensity physically occurs because the total x-rays emitted are spread over a new area that has increased by the
square of the relative distance change. For example, when
the distance from the x-ray target, a point source* of
radiation, is doubled, the radiation at the new location
spans an area four times larger than the original area.
However, because the same amount of radiation exists to
cover this larger area, the intensity at the new distance
consequently decreases by a factor of four (Fig. 15.5).
The formula for ISL is shown in the equation in
Box 15.2. A mathematical example is also provided. The
inverse square law should be used whenever possible
to reduce the radiographer’s exposure from sources of
Application of the Inverse Square Law. When light is
emitted from a source, such as a flashlight, the intensity
decreases quickly with the distance from the source.
X-rays act in the same manner, as the distance from the
source increases, the intensity decreases. The inverse
square law (ISL) expresses the relationship between dis-
tance and intensity (quantity) of radiation and is an important tool for limiting the dose received by personnel.
The law is simply stated as: “The intensity of radiation is
inversely proportional to the square of the distance from
the source.”
*Point source: To correctly treat finite-sized radioactive
sources as “point sources” so as to facilitate the calculation
of exposure rates at points of interest, it is necessary that the
distance of such points from the radioactive source be at
least equal to 10 times the largest dimension of the source.
As an example of this concept, consider a spherical radioactive source whose diameter is 2.5 cm. Then the smallest
distance away from this source at which it may be accurate
enough to regard it mathematically as a “point source” will
be 25 cm.
CHAPTER 15 Management of Imaging Personnel Radiation Dose
301
Point
source of
x-rays
d
At d (1 m),
area x
Fig. 15.5 When the distance from a point source of radiation
is doubled, the radiation at the new location spans an area four
times larger than the original area. However, the intensity at
the new distance is only one-fourth of the original intensity.
x
d
x
2
At 2d (2 m),
area 4x
2x
2x
2
BOX 15.2 Inverse Square Law Formula
and Example
2
II(d )
122
5
2
(d )
1
where I1 expresses the exposure (intensity) at the original distance, I
new distance, d
the source of radiation, and d
tance from the source of radiation.
Example: If a radiographer stands 1 m away from an
x-ray tube and is subject to an exposure rate dose* of
2 mGy
a
moves to a position located 2 m from the x-ray tube?
Answer:
*Exposure rate dose, given in units of mGya per hour, is the
same quantity as air kerma rate.
expresses the exposure (intensity) at the
2
expresses the original distance from
1
per hour, what will it be if the same radiographer
2I4
(Cros s-multiply )
1
2
I 0.5 mGy /hr
2 a
expresses the new dis-
2
2
II(d )
122
2
(d )
1
2
2I(2)
2
(1)
2
4I 2
2
x-radiation. (This law also may be applied to sources of
gamma and neutron radiation.)
Conversely, the ISL also implies that if a radiographer moves closer to a source of radiation, this individual’s radiation exposure can dramatically increase.
For example, if the radiographer stands 2 m away
from an x-ray source instead of 6 m away, the radiographer’s radiation exposure increases by a factor of
(6/2)2 5 9.
Shielding
When it is not possible to use the principles of time and/
or distance to minimize occupational radiation exposure,
shielding of appropriate thickness may be used to provide
adequate protection from radiation. The most common
materials used for structural protective barriers are:
• Lead
• Concrete
Accessory protective devices are made of lead-
impregnated vinyl. These accessory devices include:
• Aprons
• Gloves
• Thyroid shields
• Protective eyeglasses
This apparel is to be used when it is not possible to
remain wholly behind either a stationary or movable
protective barrier. The ability of materials to attenuate
radiation depends on their atomic number, density, and
thickness.
Protective Structural Shielding. Structural barriers
such as walls and doors in an x-ray room have been
designed to provide radiation shielding for both:
• Imaging department personnel
• The general public
These barriers are necessary to ensure that occupa-
tional and nonoccupational annual EfD limits are not
exceeded. Lead impregnated drywalls of appropriate
thickness are used in the walls of the radiography or
fluoroscopy room to provide adequate shielding. A
qualified medical physicist determines the exact lead
requirements for a particular imaging facility. Although
radiographers should understand the concept of shielding, they are not responsible for determining barrier
thickness.
Primary protective barrier. The purpose of a pri-
mary protective barrier is to prevent direct, or unscat-
tered, radiation from reaching personnel or members of
the general public on the other side of the barrier. The
primary beam consists of the x-ray photons that follow
straight-line paths through all sets of collimator shutters. Primary protective barriers are located perpendicular to the undeflected line of travel of the x-ray beam
(Fig. 15.6).
302
CHAPTER 15 Management of Imaging Personnel Radiation Dose
Secondary
protective
barrier
Fig. 15.6 Protective barriers are lined with lead to protect per-
sonnel and the general public from radiation. The primary protective barrier is located perpendicular to the undeflected line
of travel of the x-ray beam. The walls that are not in the direct
line of travel of the primary beam are called secondary protec-
tive barriers because they are designed to shield only against
secondary (leakage and scattered) radiation.
0.8 mm (
Primary
protective
barrier
1
⁄32-inch) rolled
lead sheet
Leakage
radiation
Collimator
Primary
(useful)
beam
Scattered
radiation
Exit or image
formation
radiation
X-ray tube
(peak energy
130 kVp)
1.5 to 2.1 meters (5 to 7 feet)
1.6 mm (1⁄16-inch) rolled
lead sheet
If the peak energy of the beam is 120 kVp, the pri-
mary protective barrier in a typical installation:
• Contains of 1.6 mm (1/16 inch) lead
• Extends 2.1 m upward from the floor of the x-ray
room, when the x-ray tube is 1.5 to 2.1 m from the
wall in question
Secondary protective barrier. Secondary radiation
consists of radiation that has been deflected from the
primary beam. Leakage from the tube housing (photons
that pass through the housing) and scatter (primarily
from the patient) make up the secondary radiation. A
secondary protective barrier protects against leakage
and scatter radiation. Any wall or barrier that is never
struck by the primary x-ray beam is classified as a
secondary barrier (see Fig. 15.6). This does not mean
that secondary radiation cannot strike primary barriers
as well. A secondary barrier should overlap the primary
protective barrier by approximately 1.3 cm (1/2 inch).
In a typical installation, the secondary barrier consists
of 0.8 mm (1/32 inch) of lead.
Radiographic and fluoroscopic exposures should be
made only when the doors to x-ray rooms are closed.
This practice affords a substantial degree of protection
for persons in areas adjacent to the room door because
in most facilities room doors have attenuation for diagnostic energy x-rays equivalent to that provided by
0.8 mm (1/32 inch) of lead.
Control-booth barrier. X-ray rooms housing per-
manent radiographic equipment contain a control-
booth barrier for the protection of the radiographer.
This barrier must:
• Extend at least 2.1 m upward from the floor
• Be permanently secured to the floor
Diagnostic x-rays should scatter a minimum of two
times before reaching any area behind this barrier. Because this booth is situated so that it intercepts leakage
and scattered radiation only, it may be regarded as a
secondary protective barrier. To ensure maximum protection during radiographic exposures, personnel must
remain entirely behind the barrier. The radiographer
may observe the patient through the lead glass window*
in the booth (Fig. 15.7). This window typically consists
of 1.5 mm (1/16-inch) lead equivalent. With the appropriate degree of shielding in the barrier, the radiographer’s exposure will not exceed a maximum allowance of
1 mSv (100 mrem) per week; in actual practice in a welldesigned facility, exposure should not exceed 0.02 mSv
(2 mrem) per week. For further protection, the exposure
cord, if one is present, must be short enough that the
exposure switch can be operated only when the radiographer is completely behind the control-booth barrier.
Clear lead–acrylic secondary protective barrier.
Clear lead–acrylic material impregnated with approximately 30% lead by weight may be fashioned into an
effective secondary protective barrier, such as for the
control booth (Fig. 15.8). This creates a modern appearance for the facility and permits a panoramic view, allowing diagnostic imaging personnel to observe the patient
more completely. Modular or movable x-ray barriers:
• Are shatter-resistant
• Can extend 2.1 m upward from the floor
• Are available in lead equivalency from 0.3 to 2 mm
* The wall barrier of the control booth should be at least 46 cm
(18 inches) beyond the edge of the view window.
CHAPTER 15 Management of Imaging Personnel Radiation Dose
303
Fig. 15.7 While making a radiographic exposure with a station-
ary radiographic unit, the radiographer must remain completely
within the control-booth barrier (behind the fixed protective barrier) for safety. The radiographer may observe the patient
through the lead glass observation window in the control booth.
Clear lead–acrylic overhead protective barrier.
Clear lead–acrylic protective barriers also can be used
as overhead x-ray barriers providing an open view
during special procedures and cardiac catheterization
(Fig. 15.9). This shielding typically offers 0.5 mm lead
equivalency protection.
Accessory Protective Devices. Accessory protective
shielding includes aprons, gloves, and thyroid shields
made of lead-impregnated vinyl. These protective
garments are available in a variety of:
• Shapes
• Sizes
• Thicknesses
As lead equivalent thickness increases, attenuation
of the x-ray beam also increases when kVp remains
the same.
Fig. 15.8 A clear lead acrylic secondary protective barrier
impregnated with approximately 30% lead lends a modern
appearance to the facility.
Fig. 15.9 A clear lead acrylic overhead protective barrier used
during special procedures and cardiac catheterization. (From
Fluke Biomedical.)
304
Fig. 15.10 A lead apron, gloves, and thyroid shield protect the
radiographer from scattered radiation.
CHAPTER 15 Management of Imaging Personnel Radiation Dose
Requirements for lead aprons and gloves. If the ra-
diographer’s hands will be near the x-ray beam, leaded
gloves should be used. A suitable lead apron is to be worn
whenever the radiographer cannot remain behind a protective barrier during an exposure (Fig. 15.10). Histori-
cally, from regulatory doctrine, if the peak energy of the
x-ray beam was 100 kVp, then a protective apron’s attenuation must be equivalent to at least a 0.25 mm thickness of
lead. An apron of 0.5 mm lead equivalent, however, affords much higher security and is the most widely used
and recommended thickness in diagnostic imaging and is
the minimum lead equivalent required for a protective
garment worn by occupationally exposed individuals during fluoroscopic or interventional procedures. Regardless
of the regulatory mention of 0.25 mm thicknesses of lead
for some purposes, the need for 0.5 mm lead equivalent
for fluoroscopy and interventional cases and the recommendations that 0.5 mm lead aprons are desirable for all
purposes have prompted most facilities to stock 0.5 mm
lead aprons only. This eliminates the possibility of personnel inadvertently selecting the wrong apron. Therefore
0.5 mm has become the all-purpose apron of choice and
in many cases, should also be in a wraparound style. A
lead apron with 0.25 mm of lead is, however, very appropriate for use in mammography.
Neck and thyroid shield. A neck and thyroid shield
(Fig. 15.11) are employed to guard the thyroid area of
occupationally exposed personnel during:
• General fluoroscopy
• X-ray special procedures
The neck and thyroid shield should be a minimum
of 0.5 mm lead equivalent.
Fig. 15.11 The neck and thyroid gland can be protected from
radiation exposure through the use of a 0.5-mm lead equivalent
protective shield.
Fig. 15.12 Eyeglasses protect the lens of the eyes during gen-
eral fluoroscopy and special procedures. (Shown are glasses
with wraparound frames; other styles are also available.)
Protective eyeglasses. Scatter radiation to the lens
of the eyes of diagnostic imaging personnel can be substantially reduced by the use of protective eyeglasses
(Fig. 15.12), fitted with optically clear lenses that contain a minimal lead equivalent protection level of 0.35
mm. Side shields on the glasses are also available and
useful for procedures that require turning of the head. A
wraparound frame containing optically clear lenses
with 0.5 mm lead equivalent may also be acquired.
X-RAY TUBE HOUSING CABLES
While the x-ray tube housing is massive enough to provide a significant degree of shielding from secondary
CHAPTER 15 Management of Imaging Personnel Radiation Dose
305
radiation, it is also designed to protect the operator
from the hazard of electric shock. Because of this, the
radiographer must be both observant* and careful when
handling this piece of equipment and its adjoining part,
the collimator. While manipulating the tube housing
assembly for a radiographic examination, the radiographer should avoid rough handling or severely bending
the high-tension cables that connect to the positive and
negative terminals of the x-ray tube. No one should ever
touch the tube housing or high-tension cables while a
radiographic exposure is in progress.
PROTECTION DURING FLUOROSCOPIC PROCEDURES
Personnel Protection
To ensure protection from scattered radiation emanating from the patient during a fluoroscopic examination,
the radiographer should:
• Stand as far away from the patient as is practical
• Move closer to the patient only when assistance is
required
A protective apron of at least 0.5 mm lead equivalent
must be worn during all fluoroscopic procedures. Protective lead gloves of at least 0.25 mm lead equivalent
should be worn whenever the hands must be placed near
the fluoroscopic field (Fig. 15.13). Imaging personnel
*Observant means looking at the physical condition of the cables
and cable coverings to discern undue wear or stress effects that
could lead to a serious hazard.
assisting during a fluoroscopic examination also should
wear thyroid shields of 0.5 mm lead equivalent, especially if they are standing close to the patient being examined (Fig. 15.14). If immediate assistance during a
fluoroscopic examination is not required, the radiographer should either stand behind the radiologist, who is
also wearing protective apparel, or stand behind the
control-booth barrier until services are required. A
wrap-around protective apron is recommended to protect personnel who must move around the x-ray room
during a fluoroscopic examination.
Dose-Reduction Techniques
Many of the methods and devices that reduce the radiographer’s exposure when operating stationary (fixed)
radiographic equipment also reduce the dose received
during a fluoroscopic procedure. These methods and
devices include:
• Adequate beam collimation
• Adequate filtration
• Control of technical exposure factors
• Appropriate source-to-skin distance
• Diagnostic-type protective x-ray tube housing
To ensure adequate protection for both the radiogra-
pher and the radiologist, some additional requirements
are included in the federal government specifications for
the use of fluoroscopic equipment. An example is use of a
cumulative timing device that produces an audible signal
after 5 minutes of total beam-on time has been exceeded.
Thyroid shield
Protective
Protective curtain,
or sliding panel
Fig. 15.14 Scattered radiation produced during a fluoroscopic
examination can be absorbed by a protective curtain or sliding
panel, with a minimum of 0.25 mm lead equivalent placed between the fluoroscopist and the patient.Fig. 15.13 Lead gloves.
lead
apron
306
CHAPTER 15 Management of Imaging Personnel Radiation Dose
Remote-Control Fluoroscopic Systems
The remote-control unit provides imaging personnel
with the best radiation protection opportunity. Remotecontrol systems permit the radiologist, and assisting
radiographer, to remain at a control console located
behind a protective barrier until their presence within
the room is needed. This system also further improves
imaging personnel safety because the added distance
from the x-ray tube makes use of the inverse square law.
Protective Curtain
A protective curtain, or sliding panel, with a minimum of
0.25 mm lead equivalent should typically be positioned
between the fluoroscopist and the patient to intercept
scattered radiation above the tabletop (see Fig. 15.14).
Bucky Slot Shielding Device
A Bucky slot shielding device of at least 0.25 mm lead
equivalent must automatically cover the Bucky slot opening in the side of the x-ray table during a standard fluoroscopic examination when the Bucky tray is positioned
at the foot end of the table (Fig. 15.15). This shielding
device protects the radiologist and radiographer at the
gonadal level. Without this device and the protective curtain in place, the exposure dose rate to the fluoroscopist
could markedly exceed 1 mGya/hr at a standard distance
of 0.6 m from the side of the x-ray table.
Rotational Scheduling of Personnel
Diagnostic imaging personnel are potentially subjected
to the highest occupational exposure during:
• Fluoroscopy: fixed and mobile
• Mobile radiography
• Special procedures
• Interventional surgery
Scheduling radiographers to spend less time in these
higher radiation tasks by arranging assignments to
clinical areas in a rotational pattern can decrease this
exposure. This practice, therefore, uses the cardinal
safety principle of time as a means of additional radiation protection.
PROTECTION DURING MOBILE X-RAY EXAMINATIONS
Use of Protective Garments
Mobile radiographic systems create special radiation protection considerations for the radiographer. Some states
require radiographers to wear lead aprons whenever they
are performing mobile radiographic or fluoroscopic examinations. A protective apron should be assigned to
each mobile unit so that it is immediately available for the
radiographer.
Distance as a Means of Protection
The most recent mobile units are equipped with a remote-control exposure device. This permits the radiographer to leave the immediate vicinity and uses the
cardinal principle of distance as an effective means of
protection from radiation. Most mobile units are not
remotely controlled. For those units the cord leading to
the exposure switch must be long enough to permit the
radiographer to stand at least 2 m from the:
• Patient
• X-ray tube
• Useful beam
Head end of
radiographic
table during
fluoroscopy
Bucky slot
shielding
device
Fig. 15.15 To provide protection at the gonadal level for the fluoroscopist, the Bucky slot shielding device
should be at least 0.25 mm lead equivalent.
Foot end of
radiographic
table during
fluoroscopy
Bucky tray