Radiation protection II
(in dental radiology)
Jiří Štěpán
head of ORD FN Brno
• Dental examinations are the most frequent type of
radiological procedure, and account for 21 % of the total
on a global scale.
• X-rays examinations help dentists to diagnose, plan
treatments and monitor both treatments and lesion
development.
• There are four types of dental radiological procedure
1. intraoral (bite wing, periapical and occlusal) radiography
2. panoramic radiography
3. cephalometric radiography
4. cone-beam CT (CBCT)
Introduction
Radiation protection in dental
radiology
2
• Individual doses are small but collective doses cannot be
ignored due to the high volume of procedures.
• The estimated annual number of dental examinations is
about 520 million, with a frequency ranging from less than
one to more than 800 per 1000 population per year.
Introduction
Radiation protection in dental
radiology
3
• The most effective way to reduce dose in dental
radiography is to avoid unnecessary X-ray examinations
by justification.
• Routine dental X-ray examination for all patients is not
justified.
• The patient dose for each X-ray examination should be
optimized so that it is As Low As Reasonably Achievable
(ALARA) and consistent with producing the required
image quality.
• It is important that the equipment is subject to formal
acceptance testing, routine quality control, undergoes
proper maintenance, and has all the standard dose
reduction features.
A good radiation protection practice in dentistry
Radiation protection of patients
4
• With well-designed and optimized equipment and
procedures there is no need for routine use of lead
aprons for the patient in dental radiology.
• Lead aprons may provide some protection in the rare
case of the vertex occlusal examination, especially in a
patient who is, or may be, pregnant.
• On the other hand, the use of a lead apron may reassure
patients that every effort is being made to ensure their
safety, and may reduce the amount of time that needs to
be taken to reassure them.
• Certainly, a lead apron should be provided for any patient
who requests one.
An use of lead aprons and personal protective devices
Radiation protection of patients
5
• It may also be advisable to consider using them on a
cautionary basis where equipment and/or technique have
not been verified by a radiation protection specialist, and
where they will not otherwise interfere with the
examination.
• Thyroid collars should be used in all examinations where
the thyroid may be exposed to the main beam or to a
considerable amount of scatter radiation.
• Lead aprons must be provided for a person who is
required to support a patient during the radiographic
procedure (i.e., a comforter or carer).
• Assisting adults should be positioned so that all parts of
their body are out of the main beam.
An use of lead aprons and personal protective devices
Radiation protection of patients
6
• Many actions are similar to those recommended in adult
procedures.
• Although radiation exposure arising from dental radiology
is low, a child may undergo many repeated procedures
during childhood and adolescence.
• Therefore, the accumulated effect of the radiation
exposure should be taken into consideration.
• The salivary and the thyroid glands are among the organs
at risk in dental radiology.
• The salivaries are often within the primary beam, while
the thyroid receives dose mainly due to scattered
radiation.
Safety measures for children undergoing dental radiography
Radiation protection of patients
7
• Since the thyroid is one of the most radiosensitive organs
in children, it may be necessary to consider shielding it
from time to time.
• Useful guidance in this regard is available in European
Guidelines on Radiation Protection in Dental Radiology
published by European Commission (2004).
Safety measures for children undergoing dental radiography
Radiation protection of patients
8
• Employees performing dental radiography should not
normally receive significant radiation dose provided
normal radiation protection measures are employed, such
as distance and shielding.
• A report from UK estimates a mean level of less than 0.1
mSv per year, in the practice conditions that prevail there.
• In the USA the mean dose received by dental workers is
reported to be 0.2 mSv.
• For CBCT (cone beam computed tomography), in the
absence of shielding, scatter doses between 4.1 and 46.8
µSv at 1 m have been reported; therefore, this modality
should be installed in a protected enclosure.
Typical staff dose levels in dental radiology
Radiation protection of staff
9
• Given the low doses received by staff involved in dental
radiography, routine personnel monitoring is generally
considered to be desirable but not necessary.
• Different national regulations should be taken into
consideration.
• UK guidance recommends that monitoring is not normally
required unless the risk assessment indicates that
individual doses are likely to exceed 1 mSv per year.
• However, national guidance in other countries
recommends personal monitoring for all dental practices
using X-ray equipment.
A need for personnel monitoring in dental practice
Radiation protection of staff
10
• Where regulations do not require individual personnel
monitoring, it may be valuable to monitor the practice
through monitoring one or more individuals from time to
time.
A need for personnel monitoring in dental practice
Radiation protection of staff
11
• It is unusual for any member of staff in dentistry to get the
foetal dose limit of 1 mSv from work.
• A female staff member should understand the importance
of notifying her employer if she becomes pregnant.
• If notified, the employer should ensure that the pregnant
employee’s working conditions are optimised and that the
prescribed dose limits are not exceeded.
• Generally, the working conditions, after declaration of
pregnancy, should be such that it is unlikely that the
foetal dose will exceed 1 mSv during the remainder of the
pregnancy.
A pregnant employee in the dental radiology department
Radiation protection of staff
12
• In a dental setting, extensive modifications of the working
environment are usually not needed; general protection
measures (e.g. personal shielding) suffice.
• A qualified expert can be contacted to estimate the
projected foetal dose based on equipment factors and
workload.
A pregnant employee in the dental radiology department
Radiation protection of staff
13
• Film (or other image receptor) should not be hand held by
a member of the dental practice staff.
• If necessary it should be held by the patient, but only
when it cannot otherwise be kept in position.
• If the patient cannot hold it, and a comforter/carer must
be involved, then this should be done using forceps or
other device (eg., a specifically designed dental film
holder) so that fingers are not in primary beam.
Holding a dental film (or a digital image receptor) during radiography
Radiation protection of staff
14
• Handheld portable X-ray equipment for intraoral
radiography should be used only for examinations where
it is impractical or not medically acceptable to transfer
patients to a fixed unit.
• Examples are patients in nursing homes, residential care
facilities or homes for persons with disabilities; in forensic
practice; or for military operations abroad without dental
facilities.
• The use of portable X-ray equipment in other settings
(e.g. dental clinic) is discouraged.
An use of portable (handheld) intra-oral radiography equipment
Radiation protection of staff
15
• The purpose of facility design includes ensuring that
prescribed dose limits are not exceeded.
• This requires consideration of workload, the size of the
facility, the duration for which people are in the
surrounding area, and is best achieved with the advice of
a radiation protection expert.
• Formal approval and/or licensing for the structural
shielding and other radiation safety measures may be
required, depending on national regulations.
A structural shielding in dental radiography department
Radiation protection of staff
16
• In the case of a single-chair room, persons must not be
present in the room during a radiographic exposure
unless their presence is necessary for conduct of the
examinations.
• Persons present must be located behind a shield allowing
a view of the patient and the “exposure on” indicator, or
wearing protective apron, or at least 2 m from the source
of scattered radiation, i.e. the patients head, and not in
line with the primary beam.
• In the case of the multi-chair room, there should be
adequate shielding between the chairs.
A presence of persons in the room during radiographic exposure
Radiation protection of staff
17
• The foetal dose from a dental X-ray exam, including
CBCT, has been estimated to be between 0.009 μSv and
7.97 μSv. (A threshold for malformations is 100 mSv!)
• This is usually less than the estimated daily natural
background dose received by the foetus.
• The use of an apron with lead shielding and/or a
thyroid shield can reduce the dose to the foetus even
further.
• However, the use of shielding should be done with proper
care, to assure that the radiograph is of adequate
diagnostic quality (i.e. keeping the shielding outside of the
X-ray beam) and that it does not lead to overexposure
(for equipment using some form of automatic
exposure control – AEC).
Typical foetal doses in dental radiographic procedures
Radiation protection of pregnant
women
18
• Information on possible pregnancy should be obtained
from the patient.
• A female of reproductive capacity should be considered
pregnant unless proved otherwise.
• If the patient is pregnant the possibility of obtaining
information from a non-radiological investigation should
be considered.
• If the radiological examination is considered essential it
should be performed and due consideration should be
given to optimisation.
Possible pregnancy of a woman before a dental radiological procedure
Radiation protection of pregnant
women
19
• Because of the widespread fears of radiation induced
damage to the unborn child, it is reasonable to counsel
the woman on level of radiation exposure and associated
risks prior to performing the procedure.
• It is essential to have pregnancy warning signs in the
waiting rooms.
Possible pregnancy of a woman before a dental radiological procedure
Radiation protection of pregnant
women
20
• The risk to the foetus from a few µSv of radiation
exposure arising from a dental radiographic procedure is
extremely small.
• The cancer risk to the unborn child resulting from a 10
µSv foetal dose is several thousand times less than the
background risk of childhood cancer.
• The risk of inducing a genetic abnormality is an even
smaller fraction of the background risk of genetic
disorder.
• Hence patient doses received in the normal practice of
dental radiology would never warrant consideration of a
termination, and patients with concerns in this regard
should be counselled accordingly.
The risk to the foetus from a dental X-ray procedure on a pregnant woman
Radiation protection of pregnant
women
21
• Radiation dose is a measure of how much energy is
absorbed when something or someone is exposed to X-
rays.
• This is important because it is this absorption of energy
that can cause damage to a person.
• Different quantities are used to express dose, see below.
• The basic quantity is absorbed dose.
• The quantity of energy (dɛ) deposited by the radiation per
unit mass of tissue (dm).
• The unit of absorbed dose is the gray (Gy) and one gray
is equal to 1 joule of energy deposited in 1 kg of tissue.
A radiation dose of X-rays
Radiation doses
22
dε
D
dm

• A commonly used quantity to express the dose to a
person is effective dose, which takes into account the
dose to different organs/tissues which are exposed (as
different organs/tissues have varying sensitivity to
radiation). The SI unit is the sievert (Sv).
• wT – tissue weighting factor (a factor representing the
radiosensitivity of a particular tissue or organ)
• HT – equivalent dose
• wR – radiation weighting factor (for X-rays = 1)
• DTR – mean absorbed dose in tissue or organ
A quantity used to relate radiation dose to risk
Radiation doses
23

T
TT.HwE
TRRT .DwH 
• Effective dose is related to the risk for stochastic effects
(cancer and genetic effects).
• The approach internationally adopted for risk estimation
is the “linear-no-threshold (LNT)” model, which assumes
a linear relation between exposure and risk down to zero
dose.
• Effective dose and its associated risk should not be
applied to individuals, but can be used to compare
between modalities, techniques and other sources of
exposure (e.g. natural background levels).
• Non-stochastic effects (tissue reactions / deterministic
effects) may also occur at organ dose levels above a
specific threshold.
A quantity used to relate radiation dose to risk
Radiation doses
24
• Since the effective dose cannot be measured, in practice,
other dose quantities that are directly measurable are
used for the purpose of optimization, dose monitoring,
and quality assurance.
• They are specific to a certain imaging modality.
• The measurable quantity is the entrance surface air
kerma/dose. Note: kerma is numericaly equal with dose
for energies of X-rays used in medicine.
• The unit of entrance surface kerma is the gray (Gy), but in
dental radiology the dose levels are usually a small
fraction of one gray – milligray (mGy), or even microgray
(µGy).
Quantities used to measure the dose from dental X-ray equipment
Radiation doses
25
• In cephalometric, panoramic radiography and in CBCT
the measurable quantity is usually the product of kerma
(dose) and the X-ray field, called Kerma-area product,
measured in mGy · cm2.
Quantities used to measure the dose from dental X-ray equipment
Radiation doses
26
• In the scope of quality assurance, measurable doses
from radiological procedures are often expressed as
diagnostic reference levels (DRL), based on local surveys
of typical patient doses.
• DRL values for adult exposures from various national
surveys are in the following ranges:
Intraoral radiography
entrance surface kerma: 0.65–3.7 mGy
kerma-area product: 26–87 mGy · cm2
Panoramic radiography
entrance surface kerma: 3.3–4.2 mGy
kerma-area product: 84–120 mGy · cm2
Lateral cephalometric radiography
kerma-area product: 41–146 mGy · cm2 (adults)
kerma-area product: 25–121 mGy · cm2 (children)
Typical doses from dental radiological procedures
Radiation doses
27
• Typical effective doses are for:
• intraoral dental X-ray imaging procedure 1–8 μSv
• panoramic examinations 4–30 μSv
• cephalometric examinations 2–3 μSv
• CBCT procedures (based on median values from
literature): 50 μSv or below for smaller medium-sized
scanning volumes, and 100 μSv for large volumes
Typical doses from dental radiological procedures
Radiation doses
28
• Thus the doses from intraoral and cephalometric dental
radiological procedures are lower, usually less than one
day of natural background radiation.
• Doses for panoramic procedures are more variable, but
even at the high end of the range are equivalent to a few
days of natural background radiation which is similar to
that of a chest radiograph (E ≈ 0,02 mSv).
• CBCT doses cover a wide range, but may be tens or
even hundreds of µSv of effective dose higher than
conventional radiographic techniques, depending upon
the technique.
• Rapid technological improvements to CBCT equipment
mean that typical dose ranges are likely to change.
Typical doses from dental radiological procedures
Radiation doses
29
• Only a qualified expert (e.g. medical physicist) can
measure the abovementioned dose quantities, and is
able to provide more detailed information regarding these
subjects.
Providing of detailed information regarding doses
Radiation doses
30
• It is done by making sure that radiographs are selected
for each individual patient based on clinical need.
• An use of a “routine” protocol for X-rays of patients should
be avoided and the patient must always be examined
before choosing any X-ray procedures.
• Just as a physician prescribes drug therapy, such as
antibiotics or painkillers, to suit a patient’s diagnosis, so
he should try to select any X-ray examinations according
to their clinical need.
Avoiding unnecessary examinations
Justification
31
• Guidelines that can support you and the patient in this
decision, called referral criteria (or selection criteria),
have been developed by various professional
organizations (EC-RP136; Haute Autorité de Santé;
SEDENTEXCT Provisional Guidelines; Espelid et al.,
2003; Harris et al., 2002; Isaacson et al., 2008;
Pendlebury et al., 2004
(http://www.sedentexct.eu/system/files/sedentexct_projec
t_provisional_guidelines.pdf)).
• These are systematically developed statements of “good
practice” for radiology in specific clinical dental situations.
• Even though they are not rules, they can give you a
framework against which to consider your patient’s
needs.
An advice to help with a selection of X-ray examinations
Justification
32
• There is no justification for this routine practice!
• Radiography may be required when a clinical
examination suggests the presence of an abnormality, or
when interceptive and active orthodontic treatment is
being considered.
• Clinical indicators, used to identify patients who might
benefit from a panoramic radiograph, are effective in
excluding children for whom an X-ray examination is not
likely to be of value.
A monitoring the dental development of children by a panoramic radiograph
Justification
33
• Professional societies in collaboration with national
authorities often recommend that users make regular
image quality performance checks on X-ray equipment
(and viewing screens where relevant).
• This is particularly important for dental cone-beam CT
systems and panoramic X-ray equipment.
• To enable users to do this, manufacturers should provide
details of the test procedures and the expected results in
the equipment’s instruction manual.
• Any test objects or phantoms that are necessary for these
tests and specific to individual equipment models or
manufacturers should be provided with the equipment as
standard.
Routine quality assurance (QA) checks of X-ray equipment
Optimization
34
• Professional societies, in collaboration with national
authorities should publish guidance for users of dental Xray
equipment on how to optimize the radiation exposure
of patients during justified X-ray examinations.
• For each imaging modality, there are many actions that
can be taken to achieve a significant reduction in dose.
• These are listed below for intra oral; panoramic and
cephalometric, dental CBCT.
• In addition, ensuring high quality clinical images a
significant means of protecting patients by maximizing the
benefits of the X-ray examination.
The most important features of dental X-ray for dose reduction
Optimization
35
For intra oral equipment
• Using tube voltage in the range 60 (minimal) to 70 kV.
• Nominal focal spot size should range between 0.4 mm
and 0.7 mm.
• Tube current usually ranges between 3.5 to 8 mA, the
exposure time should be below 1s in every exposition.
• The X-ray tube filtration should be sufficient to reduce
entrance skin dose to the patient consistent with
producing satisfactory image quality.
The most important features of dental X-ray for dose reduction
Optimization
36
• Rectangular collimation is strongly recommended, it
approximates the size and shape of the receptor reduces
dose significantly in comparison to circular collimation; a
dose reduction exceeding 60 % can be achieved in dental
radiology by using rectangular collimation.
• A position indication device which ensures a minimum
focus-to-skin distance of 20 cm should be attached to the
tube head (eg. by use of a long collimator/cone as
opposed to a short conical one).
The most important features of dental X-ray for dose reduction
Optimization
37
• Exposure settings used should be the minimum
consistent with the speed of the imaging system used.
Advice on exposure settings should be provided in the
manual for the X-ray equipment, which should be
available in the user’s native language and written in
easily understood terminology.
• The fastest available film consistent with achieving
satisfactory diagnostic results should be used. E-speed
and F-speed films reduce dose by more than 50 %
compared with D-speed films.
The most important features of dental X-ray for dose reduction
Optimization
38
• Digital detectors have the potential for further dose
reduction, even compared with F-speed film, provided the
repeat rate and use of higher exposure factors than
necessary are controlled.
• Portable intra-oral X-ray units should only be selected in
specific situations (Berkhout et al. 2015; UK PHE 2016;
HERCA).
• Where old X-ray equipment is used, it may be possible to
take immediate action to achieve a significant reduction in
patient dose.
The most important features of dental X-ray for dose reduction
Optimization
39
For panoramic and cephalometric equipment
• The X-ray beam for cephalometric imaging should be
collimated to the area of clinical interest.
• Modern panoramic systems also allow the field to be
limited to the area of clinical interest, thereby offering a
significant potential for dose reduction. If available,
limitation of field size to the area required for diagnosis
should be used for panoramic radiography.
The most important features of dental X-ray for dose reduction
Optimization
40
• Where available, paediatric examination modes should
always be used for examinations of children. If not
available, the exposure factors (such as kV, mA,
exposure time) should be suitably adjusted. This may
result in a dose saving to the patient of 50 % or more
[Lecomber et al.1993].
• The inclusion of wedge filters in cephalometric equipment
reduces exposure to the soft-tissue facial profile and
allows optimal imaging, while the provision of asymmetric
collimation allows the exposed area to be confined to the
area of clinical interest.
The most important features of dental X-ray for dose reduction
Optimization
41
• Only the fastest screen-film combinations (at least 400)
that are compatible with imaging requirements should be
used for conventional panoramic and cephalometric
imaging. Note that the intensifying screen and film must
be spectrally matched, for example, if the screen emits
light in the green region of the spectrum, the film used
should be one that is sensitive to green light.
Furthermore, the physical condition of screens
deteriorates over time and it is important that their
condition is monitored and that badly damaged screens
are replaced.
The most important features of dental X-ray for dose reduction
Optimization
42
• The use of photostimulable phosphor (PSP) receptors
should be discouraged due to inferior image quality
(Benediktsdottir et al. 2003).
The most important features of dental X-ray for dose reduction
Optimization
43
For dental CBCT equipment
• The Field of View (FOV) should be adapted to the clinical
indication ensuring that a region of interest can be
covered with a reasonable margin of error, without
exposing areas which are not needed for diagnostics [EC,
2012].
• CBCT units should at least offer a small-FOV option (not
larger than 6 × 6 cm), but do not necessarily need a
large-FOV option.
The most important features of dental X-ray for dose reduction
Optimization
44
• Exposure parameters (kV and mAs) should be optimized
for each clinical application and patient. Specifically, highmedium-
and low-mA settings should be available in
order to optimize scans for patients with different head
sizes.
• Regarding scan/exposure time, a high-speed scan option
(10 s scan time or faster, regardless of the exposure time)
should be available for patients at risk for movement (e.g.
small children).
The most important features of dental X-ray for dose reduction
Optimization
45
• Users should be aware that the voxel size is one of many
parameters determining image sharpness, and not
compare units based on this parameter. While smaller
voxel sizes do not always yield a diagnostic benefit [Uzun
et al. 2015, Kamburoğlu et al. 2015], it is recommended
that CBCT units have a high-resolution mode with a voxel
size below 0.2 mm, in order to properly visualize
trabecular bone [Pauwels et al. 2015a] as well as other
anatomical details and small pathologies [Kolsuz et al.
2015, Lukat et al. 2015].
The most important features of dental X-ray for dose reduction
Optimization
46
• There are number of projections and reconstruction
algorithm. Some CBCT systems allow the operator to opt
for imaging based on a reduced number of basis
projections. Such options should be used where the
resulting image quality is acceptable for the clinical
situation.
• When considering buying a CBCT unit, you should check
to see whether it is able to comply with national reference
doses for dental CBCT where available.
The most important features of dental X-ray for dose reduction
Optimization
47
• Two types of digital system are used in intraoral,
panoramic and cephalometric imaging. One involves
imaging sensors based on charge-couple devices (CCD)
and another uses photostimulable storage phosphor
(PSP) plates (see the image of a PSP in its plastic cover
below).
• Radiographic technique for digital imaging should be
adjusted for the minimum patient doses required to
provide the required image quality for each examination
type.
An influence of digital image receptor on patient dose in dental radiology
Optimization
48
• Intraoral digital radiography offers a potential for
significant dose reduction; some studies report that,
depending on the diagnostic task, a lower exposure may
be used when density and contrast is adjusted using the
software features.This is one of the benefits of digital
radiography where image quality can be optimized after
the image has been taken.
An influence of digital image receptor on patient dose in dental radiology
Optimization
49
• Although digital radiography offers possibility of
significant dose reduction, it can, in practice, lead to
increased patient dose.
• This can arise from, for example:
• using an image quality higher than is necessary
• use of unduly long exposure times
• retakes by staff (e.g. due to bad positioning) that may go
undetected
• lack of concern for collimation.
• Furthermore, due to smaller sensor size, more than one
exposure may be required to cover the anatomical area
imaged using a single conventional film.
An influence of digital image receptor on patient dose in dental radiology
Optimization
50
Optimization radiographic quality
• If a patient is exposed to X-rays for the purpose of
producing a radiograph, but the resulting image is not of
adequate quality for clinical use, then the patient has
been put at risk for no benefit. Ensuring adequate quality
is, therefore, a fundamental part of radiation protection.
An influence of digital image receptor on patient dose in dental radiology
Optimization
51
• It is needed to compare one’s performance by reviewing
his radiographic quality against a recognized standard.
• Such quality standards for clinical images, and guidance
on the audit process, are available in European
guidelines on radiation protection in dental radiology
(https://ec.europa.eu/energy/sites/ener/files/documents/1
36.pdf).
• As a minimum target, the aim should be to ensure that no
greater than 10 % of radiographs are of unacceptable
quality.
• If it fails this test, then actions can be taken to reduce the
proportion of unacceptable radiographs, with a target of a
50 % reduction at each successive audit cycle.
A good standard of radiographs
Optimization
52
• Choosing the correct exposure factors, ensuring accurate
patient and X-ray source position (using film holders),
along with careful processing should together contribute
to achieving excellent results in radiography.
• For intraoral radiography a simple test tool – an image of
a step wedge is useful for maintaining high image quality
(see the image – Sensitometric steps).
• During installation, a reference standard radiograph of the
step wedge should be made using the optimized
exposure setting for an adult/child.
A getting high quality intraoral radiographs
Optimization
53
• Subsequent radiographs of the step wedge/phantom
should be made during clinical use and compared with
the reference one to ensure that image quality is
maintained.
An ensuring of a getting high quality intraoral radiographs
Optimization
54
• By achieving accurate patient positioning and by good
processing of the film.
• These are the two commonest causes of poor panoramic
radiographic quality.
• Accurate positioning is helped by using all the positioning
aids correctly and by adequate training.
• Test tools for panoramic radiography are available.
An ensuring of a getting high quality panoramic radiographs
Optimization
55
• By using a cephalostat (a head-positioning device) and a
fixed X-ray source/patient/image receptor relationship.
• This is achieved using a dedicated cephalometric
attachment to panoramic X-ray equipment.
• In cases where there is no alternative to using a dental Xray
set as the source, it is very important to ensure
correct collimation of the beam and alignment with the
cephalostat.
An ensuring of a getting high quality cephalometric radiographs
Optimization
56
• An increased number of rejected films may happen.
• The retake rate can increase mainly due to wrong
positioning of the X-ray tube and small image receptor
with respect to region of interest (ROI).
• Furthermore, repeating the exposure is much easier
when using digital receptors and this has been reported
to lead to increased reject rates.
• Careful positioning using sensor-holders with a beamaiming
device and audit of clinical image quality will avoid
and or reduce retakes.
Issues in a switching from film to a digital imaging receptor
Optimization
57
• Older models are more likely to operate below 60 kV,
either by design or due to deterioration of the X-ray tube
head over its working life.
• Older models are also more likely to have low values of
total filtration (= inherent and added filtration).
• Both low operating potential (kV) and low filtration are
strongly associated with high patient doses, as is the use
of speed group D, which is often observed to be used
with older X-ray equipment.
• Therefore, an immediate saving in dose can be achieved
by taking the following steps, pending the future
replacement of the X-ray equipment:
Measures of a reducing very high patient doses
Optimization
58
• Move to the use of E-speed film.
• To improve the effective X-ray beam quality and provide
a lower radiation output rate consistent with the use of Espeed
film, a further 1.0 mm of aluminium beam filtration
should be added to the X-ray tube head, as close as
possible to the X-ray beam window in the tube head. This
may require the help of a technician.
• Continue to use the exposure settings you were using
before, unless image quality is severely affected. In this
case, the help of a medical physics expert should be
sought. The above steps should provide a reduction in
dose of at least 70 %.
Measures of a reducing very high patient doses
Optimization
59
• Poor film processing conditions may have as great an
impact on patient doses as the X-ray equipment, and so
attention should also be paid to ensure that all aspects of
processing are carried out in accordance with the advice
provided in (see European Guidelines on Radiation
Protection in Dental Radiology, RP 136, published by
European Commission, Luxembourg (2004)) and that
proper quality assurance methods are in place.
Measures of a reducing very high patient doses
Optimization
60
Means for the dental office to
minimize radiation exposure
61
Means Comments
Exposure justification The exposure should yield diagnostic information that will
influence patient care.
Image receptors Film: use the fastest speed available – currently F-speed. Film
should be processed according to the manufacturers instructions.
A proper safe light should be used.
Digital: Charged Couple Device (CCD), Complementary metaloxide
semiconductor (CMOS) and photostimulable storage
phosphor (PSP) receptors are acceptable.
Receptor holders Use to optimize alignment and minimize repeat exposures.
Beam collimation For intraoral radiographs limit beam diameter to 6 or 7 cm or
smaller at the patient’s face and preferably with rectangular
collimation.
For all other radiographs, collimate the beam to the area under
investigation.
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Means Comments
kV, mA & exposure time For intraoral radiographs preferably use 60–70 kV to optimize
contrast and reduce depth dose. Reduce exposure time and/or mA
when applicable. Use machines with automatic exposure controls
(AEC) when available. If not, use technique charts or other
appropriate means to minimize over- or underexposures.
Operator protection Operators should stand out of the primary beam, at least 2 m
away from the source, and behind a protective barrier whenever
possible.
Hand-held units Where permitted, hand-held units should be stored in a locked
facility when not in use and should always be used with a
shielding ring and held close to the patient’s face.
CBCT When indicated and when lower-dose techniques are not sufficient,
use the smallest field of view sufficient to answer the clinical
question and doseminimizing procedures such as half-cycle
exposures when appropriate. Imaging data sets may need to be
interpreted by an oral and maxillofacial radiologist.
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Means Comments
Patient shielding Use leaded aprons and thyroid collars whenever possible
(according national/local regulations).
Quality Assurance Protocols should be developed and followed for assessing the
integrity of the x-ray machine, film processor, digital image
receptors, panoramic cassettes, and darkroom.
Image viewing Radiographs should be viewed and evaluated on appropriate,
quality assured viewing boxes (film) or monitors (digital) in a
darkened environment.
Education and training Persons operating x-ray devices must have appropriate training,
education and certification.
Klinika radiologie a nukleární medicíny Fakultní nemocnice Brno a Lékařské fakulty Masarykovy univerzity