Quality Assurance in Maxillofacial Imaging

1
Quality Assurance in Maxillofacial Imaging
Dr. Enrique Platin Clinical Professor UNC School
of Dentistry Oral and maxillofacial Radiology
2
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.

3
Benefits of quality Assurance

• Improved diagnosis
• Reduced radiation exposure to patients
• More reliable equipment function
• Time savings
• Cost savings

4
Areas of radiography that should be monitored to
promote consistency in image production

• X-ray machine
• Chemical electronic processing
• integrity if image receptors
• Viewing conditions

5
Representative images
6
Patient exposure and dose

• 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 AndGET
  THE MOST INFORMATION FOR THE LEAST RADIATION

7
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/radiograp
hy.asp
NCRP report No. 145
8
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.

9
Film Holding Devices

• Reduce finger exposure
• Reduce number of re-takes

10
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

11
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.

12
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.

13
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.

14
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.

15
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 owners manual.

16
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
  Association2002)

17
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.
18
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.
19
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.
20
Safelighting

• 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.

21
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.

22
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.

23
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
Ready-to-use (does not require mixing). Ready
mixed chemistries are the most widely used.
24
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
25
Automatic Processing Time/Temp method
Temp. 810 830 850
Time 5 min 4 1/2 min 4 min
26
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.
27
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).
28
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.
29
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
30
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.

31
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.

32
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.
33
Maintain a log documenting changing of solutions,
any problems that were encountered, and any
corrective action/s taken.
34
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.

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Summary
1. Clean processors regularly 2. Replenish
solutions daily 3. Check dev. temperature
daily 4. Perform Q.C. daily
36
Maintain accurate records to document maintenance
and interventions.
37
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.

38
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.
39
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.
40
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.
41
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.
42
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.
43
Spectral matching
Film should be sensitive to the light emitted by
the screens 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.
44
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

• 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

45

• After each cleaning apply antistatic solution to
  reduce static electricity artifacts and leave the
  cassette open until the screens are completely
  dried.

46
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.

47
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.
48
Film artifacts
The crescent or half-moon 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.
49
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.
50
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.
51
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
  lesions.

52

• 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
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Technique charts
TECHNICAL CHART GENDEX (GE)
1000 PROJECTION mA kVp Impulses
FILM ANTERIOR 15 70 21
F PREMOLAR 15 70 24
F MOLAR 15 75 24
F BITEWING 15 75 18
F OCCLUSAL 15 75 24
F For large patients add 5 Kilovolts (kVP) For
small patients reduce 5 Kilovolts (kVP)

• 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.

54
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.

55
Silver recovery

• 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.

http//www.kodak.com/eknec/PageQuerier.jhtml?pq-pa
th2879/4191/4197/4233pq-localeen_US
http//www.safety-kleen.com/SKInternet/SKHome.aspx
?channelid18e2afcfbd6ed010VgnVCM1000001203200aRCR
D Local Tel [phone]
56
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/?CIDexitidhbxdrna
57

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.
58
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
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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.