Transcript PowerPoint Presentation - Infection Control in Dental

Quality Assurance in Maxillofacial
Imaging
Dr. Enrique Platin
Clinical Professor
UNC School of Dentistry
Oral and maxillofacial Radiology
Quality Assurance in Oral & Maxillofacial Radiology
Quality assurance comprises all
of the management practices
instituted by the dentist to assure
that every imaging procedure is
necessary and appropriate, the recorded
information is correctly interpreted and the
examination results in the highest image quality
and lowest possible radiation exposure, cost
and inconvenience to the patient.
© Dr. E. Platin
Benefits of quality Assurance
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Improved diagnosis
Reduced radiation exposure to patients
More reliable equipment function
Time savings
Cost savings
© Dr. E. Platin
Areas of radiography that should be
monitored to promote consistency
in image production
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X-ray machine
Chemical & electronic processing
integrity if image receptors
Viewing conditions
© Dr. E. Platin
Representative images
© Dr. E. Platin
Patient exposure and dose
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There are no limits for diagnostic exposure
Know benefits and hazards
Know patient selection criteria
ALARA
(As Low As Reasonably Achievable) This is
the guiding principle of radiation protection
everywhere including the dental office And……GET
THE MOST INFORMATION FOR THE LEAST RADIATION
© Dr. E. Platin
Use & prescription of radiographs
Radiographic examination shall be
performed only when indicated by
patient history, physical examination, or
laboratory findings (3.1.1)
http://www.ada.org/prof/resources/topics/radiography.asp
NCRP report No. 145
© Dr. E. Platin
Monitoring devices
 If monitoring devices are used they should be
worn at waist or collar level only while working.
 Devices should be stored at work in a radiation
free area.
© Dr. E. Platin
Film Holding Devices
 Reduce finger exposure
 Reduce number of re-takes
© Dr. E. Platin
Assessment of x-ray units
recommended parameters to check
American Academy of Oral and Maxillofacial Radiology
American Dental Society
 X-ray output and
representative exposure
 Kilovoltage accuracy
 Half Value
Layer (filtration)
 Exposure
reproducibility
 Milliamperage linearity
 Beam alignment &
diameter of x-ray field
 Tube head stability
Check yearly
© Dr. E. Platin
X-ray output and representative
x-ray exposure test
This test evaluates the
reproducibility of the x-ray
output. It measures the
amount of radiation at cone tip
for a given kilovoltage,
milliamperage, time, and
distance. This test can be
used to assess compliance
with acceptable exposure
ranges used for D and E films
(see chart) and to make
longitudinal comparisons of
exposure values.
© Dr. E. Platin
Position indicating device (PID) test
Patients can be exposed to a great deal of
unproductive radiation if the x-ray tube is
misaligned or the diameter of the Position
Indicating device (PID) “tube” exceeds
federal guidelines. The guidelines state
that if the source-to-skin distance is 18
centimeters or more, the x-ray field at that
distance should be confinable in a circle of
no more than 7 centimeters, (2.75 inches)
in diameter.
© Dr. E. Platin
Procedure
To check the beam alignment and the diameter
of the PID do as follows. Place a film large
enough to cover the diameter of the PID on a
flat surface, or arrange four No. 2 films in a
cross pattern as shown above; place the PID
flush to the films so that approximately half of
each film is covered and make an exposure to
blacken the films.
© Dr. E. Platin
Results
Diameter = 2.56”
Process the films and arrange them in the same
pattern as exposed. If the exposed area is greater
than 2.75 inches in diameter, the PID opening is too
large and should be replaced. If the exposed area is
out of alignment with the circumference of the cone,
the diaphragm in the collimator may be mal-positioned
and the problem should be corrected. In the above
example the PID tested falls within the guidelines.
© Dr. E. Platin
Stability of tube head
The suspension of the tube head and retractable area
must be stable in all positions so that motion artifacts
can be minimized. To check for stability, fully extend
the tube head and arm, then observe for signs of drift
or vibrations when the tube head is released. Any
instability should be corrected by adjusting the
suspension arm according to the owner’s manual.
© Dr. E. Platin
Chemical processing conditions
Studies have shown that poor processing
conditions are responsible for a large
percentage of radiographic re-takes.
Thus, a reduction in the re-take rate can
have a significant reduction in radiation
exposure to patients. This is significant,
since dental practitioners in the U.S. are
responsible for exposing over 600 million
intraoral dental films and over 17 million
panoramic images per year. Today 61% general
dentists and 73% specialists own panoramic units.
(American Dental Association ‘s Survey Center.The 200 survey of dental practice-characteristics of dentists
and patients. Chicago, Il. American Dental Association:2002)
© Dr. E. Platin
Processing pitfalls
(automatic processor)
Dark images can result from high developer temperatures,
long development times or overactive developers. Check
the thermostat, adjust it if necessary. Also, inspect the
transport system for excessive wear of the gears and
sprockets, and check the roller alignment and lubrication.
Check the replenishing mechanism as the developer may
be overactive. High water temperatures can also be
responsible for dark films. Periodically check mixing valve
adjustment and correct settings if appropriate.
© Dr. E. Platin
Conversely, light films may occur if the
developer or water temperature is too low,
the development time is too short, or there
is a decrease in developer activity. To
assess developer activity, run a strip test
and check for the possibility of
contaminated or exhausted solutions.
© Dr. E. Platin
Films could turn green- orange- brown
from weak fixer solutions or when
stained by an oxidized developer, or by
improper washing. Check the
replenishment mechanism and replenish
or replace solutions if necessary.
© Dr. E. Platin
Safelighting
QuickTime™ and a
TIFF (LZW) decompressor
are needed to see this picture.
Safelights provide adequate lighting without
fogging the film. A light emitting diode LED
safelight or universal safelight filter such as the
kodak GBX is recommended for both intraoral
and extraoral films. The wattage of the bulb
should not exceed 15 and should be placed at
least 4 feet away from the working surface.
© Dr. E. Platin
Procedure
Safelights should be evaluated every six months.
Proceed by exposing a #2 film to radiation using a
very low exposure time (the lowest setting on your
machine). Turn off all the lights including the
safelights. Look for light leaks, these must be
eliminated. Then turn on the safelight/s, open the
package of the pre-exposed intraoral film and place it
on the counter where you normally open your films.
Place a few coins on top of the film (as shown above)
and wait two minutes before processing the films.
© Dr. E. Platin
Results
Examine the processed film and if no image of the
coins are present, it can be assumed that the
safelight is safe. If images of the coin appear on the
film (as seen above), the safelight/s need to be
replaced. As a rule of thumb, if a safelight is on for
8 hours each day, replace it every 3 years.
© Dr. E. Platin
Automatic processing
During automatic processing, the film is
transported through the developing, fixing and
washing stages at controlled speeds. Most
mechanical processors use roller transport
modules and specifically formulated chemistries.
The film is not rinsed between the development
and fixing cycles. Chemistries are manufactured
in concentrate form (requires mixing) and Readyto-use (does not require mixing). Ready mixed
chemistries are the most widely used.
© Dr. E. Platin
In automatic processing, the
temperature of the chemicals is
thermostatically controlled and
the processing time is regulated
by the speed of the rollers in the
transport mechanism. Always
follow the recommended
processing temperatures
provided by the manufacturer
© Dr. E. Platin
Automatic Processing
Time/Temp method
Temp.
810
0
83
850
Time
5 min
4 1/2 min
4 min
© Dr. E. Platin
Chemical Replenishment
Chemical solutions should be replenished daily
by adding 8 ounces (236 ml) of developer and
fixer to maintain optimal concentration. This
should be done regardless of the levels of
chemicals visible in the tank. (It may be
necessary to remove some of the existing
solutions before adding replenisher. This
prevent solutions in tanks from overflowing.
© Dr. E. Platin
Chemical replenishment
To maintain the stability and consistency of the
processing chemicals, replenish developer and fixer
solutions daily. For intraoral film processors without
automatic replenishment, use 8 oz. (236 mL) of
replenisher solution daily, even if no films are
processed. This is based on an average daily run of
20 to 30 intraoral films. If you process more than 30
intraoral films per day, you should increase the
amount of daily replenisher at a rate of .25 fluid
ounces (7 ml) per additional film processed. For
example, 50 intraoral films per day would require
that 5 additional ounces (140 ml) be added to the
daily 8 ounces, a total of 13 ounces (376 ml).
© Dr. E. Platin
Processing QC
Optimal processing quality control requires the
use of a sensitometer and a densitometer,
however in the average dental office, QC can be
accomplished with the use of monitoring strips as
described in the next two slides.
© Dr. E. Platin
Dental Radiographic Normalizing
and Monitoring Device
The DRNMD has a reference (strip) that can be used to
compare the films that are exposed daily to monitor
processor performance. Follow the instruction on the
tool to perform QC.
Daily strip
Comparison of strip with reference
Image of reference step wedge
Dental Radiographic Normalizing & Monitoring Device
http://www.cspmedicalstore.com/s.nl/sc.2/category.1628/.f
© Dr. E. Platin
Preventive maintenance
Although monitoring film chemistry with film
strips is an effective way to track chemistry
performance, processor upkeep and care are
probably more important. Processors should be
cleaned at every solution change. This should
include inspecting all working parts and
lubricating mechanism where indicated.
© Dr. E. Platin
At each solution change
 Always fill the fixer tank first and the
developer tank second. This will prevent
contamination of the developer while the
fixer tank is being filled.
 After filling up the processor, turn it on
and let it reach the pre-determined
operating temperature before developing
films.
© Dr. E. Platin
Processor
Daily care
At the end of the day, remove the main cover,
the developer and fixer covers (unless
otherwise stated by the manufacturer) and
allow the processor to aerate. This prevents
condensation droplets from forming under the
covers and drip to the rollers resulting in film
artifacts.
© Dr. E. Platin
Maintain a log documenting changing
of solutions, any problems that were
encountered, and any corrective
action/s taken.
© Dr. E. Platin
Helpful checklist for
automatic processing
 Clean tanks and rollers thoroughly with a
non-abrasive brush to remove chemical
deposits and contaminants. Use a bland
soap or commercial cleaner.
 Rinse rollers thoroughly to remove any
trace of soap or cleaner.
 Inspect rollers, gears, and turning
mechanism for signs of wear.
© Dr. E. Platin
Summary
1.
Clean processors regularly
2.
Replenish solutions daily
3.
Check dev. temperature daily
4.
Perform Q.C. daily
© Dr. E. Platin
Maintain accurate records to document
maintenance and interventions.
© Dr. E. Platin
Screens and films
The selection of intensifying screens and
radiographic film should result in a system
that produces the highest diagnostic yield
with the least possible amount of radiation
to the patient and operator. Today, this is
possible with the faster-speed systems
that require short exposure times.
© Dr. E. Platin
Intraoral film
Currently there are two film speeds available for intraoral
imaging, Speed Group D, and speed group F. Group D film
is the most widely used. It provides high contrast, fine detail
and excellent image quality. Group F is more sensitive to
radiation exposure requiring only about 60% less radiation
than D. A review of the scientific literature has shown that
these two films produce equivalent diagnostic yields. On
that basis the radiology community highly recommends the
use of F speed film.
© Dr. E. Platin
Extraoral film
Extraoral or screen film is primarily
designed to be used with intensifying
screens. The selection of the film should
be based on the clinical application.
Ideally, one should select the most
sensitive system without compromising
diagnostic quality.
© Dr. E. Platin
Film selection
When selecting a film, strong consideration
should be given to films containing
emulsions which employ flat tabular grains
of silver halide. Tabular grains gather more
light and by design result in an increase in
image sharpness.
© Dr. E. Platin
Soft tissue
In addition, the object of the examination should
be factored in, for example, in cephalometric
radiography where bone and soft tissue
visualization are important a wide latitude film
should be selected. In temporomandibular joint
radiography where bone detail is of particular
importance, a high contrast film is more useful.
© Dr. E. Platin
Intensifying
screens
Intensifying screens should be selected based on their
conversion efficiency (converting x-ray energy into light
energy). Screens using Rare Earth phosphors should be
favored over screens that use Calcium Tungstate
phosphors. Rare earth phosphors have a higher
conversion efficiency, and can be four times as efficient
as calcium tungstate phosphors. That means that they
require one fourth of the x-ray energy to produce the
same amount of light energy produced with Calcium
Tungstate phosphors.
© Dr. E. Platin
Spectral matching
Film should be sensitive to the light emitted
by the screen’s phosphor. In the case of
Calcium Tungstate, a blue-light-sensitive
film should be selected. In the case of Rare
Earth phosphors, a green-light-sensitive
film should be selected. This is essential in
creating the ideal spectral match to
maximize the efficiency of the system.
© Dr. E. Platin
Cleaning intensifying screens
Cassettes should be cleaned and inspected for
light leaks and artifacts. A screen cleaner, mild
soap and water or denatured ethyl alcohol may be
used as substitutes. The following procedure is
suggested for cleaning cassettes:
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Open cassette.
Look for worn or stain areas.
Dampen a clean cotton ball or gauze with cleaner.
Wipe one screen at a time
Wipe each screen with dry cotton ball or gauze
Leave cassette open until dried
© Dr. E. Platin
After each cleaning apply antistatic
solution to reduce static electricity artifacts
and leave the cassette open until the
screens are completely dried.
© Dr. E. Platin
Film storage
Unexposed and unprocessed film should be
kept in a cool, dry place. High temperatures
decrease contrast and increase fog. Ideally,
film should be stored at temperatures
ranging between 50 and 700 F (100 and 210
C) and between 30 and 50 percent relative
humidity. Films should be used before their
expiration date.
© Dr. E. Platin
Film handling
Improper film handling can result in artifacts
such as streaks, lines, and marks that could
interfere with the diagnostic quality of the
image. Films should be handled with care.
Avoid bending or touching them with wet
hands. Handle film by the edges and protect
them from potential fogging sources.
© Dr. E. Platin
Film artifacts
The crescent or halfmoon artifact
observed in this
example resulted
from finger nail
pressure. Avoid
putting pressure on
the film or making
sharp bends, grasp
film by its edges.
© Dr. E. Platin
Static electricity is responsible for
electrical discharges on the film.
It produces a tree-like artifact or
smudge marks. Prevent static
electricity by controlling humidity
during the winter months. Other
potential sources of static
electricity come from uniforms
made of polyester materials, and
rugs. Static electricity can also be
caused by careless handling,
such as by rapidly pulling films
from their containers.
© Dr. E. Platin
Film fog results from unsafe
light, white light exposure,
overactive film chemistry or
expired films. This film was
exposed to white light when
the film packet was
accidentally opened outside of
the darkroom. The dark area
represents light exposure.
Other potential sources of film
fog are light leaks, placing the
daylight loader under bright
lights, and from faded safelight
filters.
© Dr. E. Platin
Exposure
selection
Careful exposure technique selection is equally as
important as choosing the proper image receptors.
Exposure factors should be selected to produce
images of optimal quality, density, and contrast. High
kilovoltages (90 kVp) permit the use of shorter
exposure times, thus reducing patient movement.
High kilovoltages are useful when imaging patients
suspected of having periodontal disease. Low
kilovoltages (60-70 kVp) on the other hand are use to
produce higher-contrast images and are best suited
for imaging patients suspected of having carious
© Dr. E. Platin
Compare these two
radiographs of a dental
phantom exposed using
two different kilovoltages.
Notice the decrease in
contrast as the
kilovoltage is increased
from 70 to 90 kilovolts.
For these two films, the
time was adjusted in
order to maintain
approximately the same
radiographic density.
70 kVp
90 kVp
© Dr. E. Platin
Technique charts
TECHNICAL CHART: GENDEX (GE) 1000
PROJECTION
mA
kVp Impulses
ANTERIOR
15
70
21
PREMOLAR
15
70
24
MOLAR
15
75
24
BITEWING
15
75
18
OCCLUSAL
15
75
24
For large patients add 5 Kilovolts (kVP)
For small patients reduce 5 Kilovolts (kVP)
FILM
F
F
F
F
F
Technique charts should be posted outside of each
operatory. The charts should include guidelines to
assist operators adjust techniques for large and
small patients. In some states, the posting of
technique charts is required by law.
© Dr. E. Platin
Viewboxes
The condition of the viewbox can have an effect on the
perceived density and contrast of the images.
Variations can result from dirt or discoloration of the
plexiglas front, or from the age of the bulbs. As bulbs
approach the end of their useful life, they should be
replaced. To view radiographs under optimum
conditions, clean plexiglas weekly, inspect fluorescent
bulbs and replace them if necessary.
© Dr. E. Platin
Silver is a hazardous
waste that can be
reclaimed from used fixer
by chemical replacement
or electroplating. The
shown cartridge will
effectively remove silver
for up to a year. Check
with your dental supply
house or Kodak to find
out more about silver
recovery.
Silver
recovery
http://www.kodak.com/eknec/PageQuerier.jhtml?pq-path=2879/4191/4197/4233&pq-locale=en_US
http://www.safety-kleen.com/SKInternet/SKHome.aspx?channelid=18e2afcfbd6ed010VgnVCM1000001203200aRCRD
Local # Tel 919-772-622
© Dr. E. Platin
Lead recycling
Lead foil is a hazardous waste. Contact Dental
Recycling of North America to find out how to
dispose of the lead
http://www.drna.com/?CID=exit&idhbx=drna
© Dr. E. Platin
Digital Radiography
As digital radiography continues to emerge,
quality control systems will have to be
implemented to monitor receptors,
scanners and monitors performance.
Presently, users have to rely on guidelines
set by manufacturers. However, some
universal guidelines could be applied to all
receptors (PSP, CCD, CMOS), and some
output devices such as monitors, printers
and copying media.
© Dr. E. Platin
Guidelines for testing Digital equipment
• scanners should be lubricated regularly
• clean CCD/CMOS detectors daily
• avoid scratches and bends on PSP plates and remove them
from circulation if they are damaged or interfere with the
diagnostic quality of the image
• A line pair resolution tool could be imaged every six months
and compared with a previous image to assess consistency of
system performance
20 lp/mm test tool
http://www.cspmedicalstore.com/s.nl/sc.2/category.119/it.A/id.4891/.f
© Dr. E. Platin
Recommended QC tests for basic Dental office
Te st
Esse n ti al/
Te st de vice
De sirable
Essential
Film, stepwedge
or sensit ometer
Essential
film, coins
Essential
Clean surface
Essential
Clean surface
S u gge ste d pe
rforman ce cri teri a
Exposure
reproducibility
Representative
X-ray exposure
Kilovoltage
Timer
Essential
Ion chamber
No > + 5%
Essential
Ion chamber
Essential
Essential
KVp meter
spinning t op, film
Exposure linearity
Essential
Half Value Layer
Essential
film, step wedge,
Ion chamber
Ion chamber,
filters
As recommended by the U.S.
DHHS*
+ 5% of the kilovoltage tested
0-1/4 sec (0-15 pulses) + 1
1/4-1/2 sec (15-30 pulses) + 2
1/2 sec or 30 pulses, 5% of set time
one step or adjacent exposures
within + 10%
@70 kVp
1.5 mm of Alum
@90 kVp
2.5 mm of Alum
Chemical processing
assessment
Safelight
View boxes
Image recept ors
+ 1 density steps or as indicated by
test.
Image of coin should not be visible
No artifacts
Mi n imu m
fre qu e n cy
Daily
Semiannual
Monthly
Quarterly
or as
needed
Annually
Annually
Annually
Annually
Annually
Annually
Stability of tube head Essential
Quarterly
Beam diameter
Essential
film
no > 2.75 inches
Annually
Beam alignment
Essential
film
misalignment no > + 2% of SID
Annually
Lead aprons
Essential
Radiograph
No cracks
Annually
Check and oil
Essential
As recommended by manufacturer
Bi-annual
scanners
System performance Essential
line pair t ool
Compare t o standard
Semiannual
Re-take analysis
Desirable
Quarterly
Image audit
Desirable
Quarterly
Rad safety program
Essential
Annually
review
Department of Health and Human Services. Conference of Radiation Control Program Direct ors, Inc.
© Dr. E. Platin
Conclusion
Quality assurance will not only contribute to the
reduction of radiation exposure to patients and
operators but promotes the production of higher
quality images. Higher quality images
increases the diagnostic value of the images
produced in your facility and better adherence
to ALARA.
© Dr. E. Platin