Presented by: Dean Lefebvre

300 - 1870 Albert Street Regina S4P 4W1 1-800-567-7233 Fax: (306) 787-2208 Megan Hunt (306) 787-4006 Kerry Babcock (306) 787-9578 122 – 3rd Avenue North Saskatoon S7K 2H6 1-800-667-5023 Steve Webster (306) 933-7775 Heather Nikota (306) 933-7775 Jamie Keil (306) 933-5445

Ministry of Labour Relations and Workplace Safety Occupational Health & Safety Radiation Safety Unit

Comparison of Usage by Imaging Receptor

D-Speed 10%

Digital 70%

E/F Speed 20%

2006 Results: 20% Digital 80% Film

Dental X-Ray Equipment in Saskatchewan (2013) 255 offices with 1144 x-ray units Type of X-Ray Unit

Number of Units Registered

Intraoral

1000

Panoramic/ Cephalometric Cone Beam

134 10

Quality Assurance?  Everything possible is done to produce the highest

quality diagnostic radiographs  Everything involved in that process needs to be

assessed to ensure it is in optimal working order 

Equipment and procedures

Quality Assurance  Continual self-evaluation to minimize operator error

and retakes  

Technique- knowledge and understanding Diagnosis is only as good as the assessment that is done!

QA includes extraoral radiographs too!

The Radiation Health and Safety Act and Regulations Saskatchewan Labour

Occupational Health & Safety The Radiation Health and Safety Act, 1985 and The Radiation Health and Safety Regulations, 2005

The Act and its accompanying regulations were enacted to protect the health of Saskatchewan people exposed to radiation. Jurisdiction:

Electromagnetic Spectrum (except -rays in fuel cycle and high energy linacs) Ultrasound

Radiation Health and Safety Act (2005) Quality assurance 16(1) An owner of ionizing radiation equipment that is used for diagnosis or treatment of human beings must ensure that a quality assurance procedures manual that meets the requirements of subsection (2) is prepared for use with that equipment. (2) The quality assurance procedures manual must: (a) be acceptable to an officer in form and content; (b) clearly specify the quality assurance procedures that are to be followed by the operators and other occupational workers; and (c) be appropriate to: (i) the extent of use of ionizing radiation by the facility; and (ii) the level of expertise of the operators and other occupational workers. (3) An owner of ionizing radiation equipment that is used for diagnosis relating to human beings must ensure that: (a) at the times specified by an officer, the operators of the equipment participate in the Radiation Safety Unit’s postal quality assurance program by: (i) conducting the tests that are required as part of the program; and (ii) returning the exposed test package to the department promptly;

What Does the Legislation Say About Quality Assurance? QA procedures manual MUST:  be prepared for use with the x-ray equipment  be acceptable to an officer  include all raw data kept for previous 12 months and summaries for life of equipment plus 3 years You are also required to participate in the Postal QA Program Whose responsibility is it?

Quality Assurance Programs for Dental X-Ray Imaging Are

MANDATORY

Radiation Safety Unit- 2013 (over 90% offices non-compliant)

Typical Audit Findings 1. No Manual or QA inconsistently

done 2. Different timer setting for different dental professionals, no child setting& chart not posted 3. Lead aprons – folded, when to remove from service? 4. Image receptors - when to remove from service? 5. Developer Temperature!!

Radiation Exposure Risks & Protection

Safety Considerations  provide a safe environment for all involved  Know measurements and maximum dosages  Risks of radiation and how dental radiography relates

to this  Provincial & Federal Regulations

Radiation Risks and Protection  Dental x-rays are low levels but biological damage still

occurs!

Biology • Changes to body chemistry, cells, tissues & organs How? X-Ray

Ionization Excitation Break Bonds

Chemical/Biological Changes

Free Radical Formation  X-ray photon ionizes water = H + Free Radical  uncharged atom with 1 electron in outer shell

 Reactive, unstable, may recombine to form a toxin

Ionization may have little effect on cells if they are not sensitive to radiation or if the cells heal the damage from ionization

pH Scale

Factors that Determine Radiation Effects 1.

2. 3.

Dose – (quantity of radiation) Area – (amount of tissue exposed) Age – (children more susceptible because cells are underdeveloped)

4.

Tissue type– (rapidly dividing cells and young cells)  

 

Reproductive Lymphatic Circulatory (bone marrow) Endocrine (thyroid in children)

Effects of Radiation in Dentistry Critical Organs- an organ, if damaged, diminishes the quality of the person’s life Sensitive tissues    

Lens of eye Skin Thyroid Bone marrow

Health Canada Considerations 1.

Patients should not be subjected to unnecessary dental radiography

2. Patients need to be protected from unnecessary exposures 3. It is essential that personnel in dental facilities be

protected from unnecessary exposure to radiation in the course of their work 4. The public requires adequate protection

Radiation Protection 1. Client Protection

Before Exposure  Take radiographs for a reason!  New clients: get radiographs forwarded from other office

 Keep # of radiographs to a minimum (2 BW’s vs 4 BW’s)

 Dental equipment has protective features  Filter Filter

 Collimator

 Position Indicating Device  Aligns the beam  Long PID = less divergence, penumbra & magnification

Collimator

Radiation Protection DEXshield  30% less radiation

Tru-Align  LED system  60% less radiation  Clearer images  Less retakes

During Exposure  Use a thyroid collar lead apron (except for Pan’s)  Children and pregnant women are most sensitive

 Use the fastest film available (F-speed)  F to E speed = 20% reduction  E to D speed= 60% reduction  Use the minimal amount of radiation to capture a

diagnostically acceptable image (kVp, mA, exposure time)  1 pulse = 1/60th second = 0.0167 seconds  5 pulses = 1/12th second = 0.083 seconds  12 pulses = 1/5th second = 0.200 seconds

 Proper operator technique to minimize retakes  X-ray holders  Knowledge and trouble shooting abilities  Confidence & competence  ALARA (As Low As Reasonably Achievable)

After Exposure  Proper film handling  Avoid exposure to light (& fluorescent finger nail polish) ,

scratches, bending, and wet hands

 Proper film processing  Film processing and image retrieval/manipulation

2. Dental Professional Protection

Positioning  Must be 3 meters away and at angle of 90-135 degrees  Behind a wall and no one else in room or pathway

Monitoring  Use of dosimeter badges  Workers who have received an effective dose of 1mSv in a one year period must be provided with a dosimeter  If a dentist has established that exposure is below threshold, monitoring is not required

Radiation Exposure Guidelines Person

Time Period

Occupational Worker

1 year

Effective Dose (millisieverts) 50

Occupational Worker

5 years

100

Member of Public

1 year

1

•Part II subsection 2 states, “If the effective dose received by an occupational worker in a one-year dosimetry period exceeds 20 millisieverts, the owner of ionizing radiation equipment must submit to the Radiation Safety Unit a written report explaining in full the circumstances in which the dose arose and summarizing the steps that will be taken to minimize the possibility of similar doses arising in the future.”

Dental X-ray Characteristics 1. Density  Degree of blackness



mA, KvP, exposure time =

density

 Target-receptor distance affects density  X-rays that travel 2x as far = ¼ density  You must increase the exposure time by 4 to retain the same density

Film-based only  Hot developer or more time = too dark  Decreasing time, cold, under-replenished devloper or contaminated developer chemistry = too light

Digital  “noise” or dottedness of the image  Under-exposure = noisy image  Over-exposure = low noise  Software systems respond differently to over-exposure

 X-rays must hit the sensor at right angles to

reduce noise  Images that are too noisy are not acceptable

2. Contrast  Differences in black and white shades on a radiograph  For diagnostic quality, we want to have a good mix of

shades to determine if disease is present  Affected by KvP (60-70)  KvP = contrast  Low = many shades

 You must investigate the type of generator your x-ray

unit has Single-phase produce more contrast at 70KvP than high frequency generators Single-phase = 70KvP (also higher patient exposure than high freq.) High Freq. = 60-65 KvP

Film only  Hot, cold, contaminated, improperly mixed, and old processing chemistry can affect contrast  For x-ray units with adjustable kVp settings, increasing

the kVp decreases the contrast but increases the film density if the time and/or mA are not reduced

3. Detail  Sharpness of the dental image  Categorized into motion unsharpness, geometric

unsharpness and detail visibility Motion unsharpness  If the tube head or client moves = less detailed sharpness

Geometric unsharpness  Affected by focal spot size (0.4- 1.0 mm)  Smaller focal spot size = better geometric detail

•PID length- a longer PID = increase geometric detail

Detail Visibility

 Factors that reduce detail visibility:  Excessive kVp  Exposure of film to stray radiation  Expired film/old plates

 Film stored in excessive heat  Exposure of film/plate to white light prior to or

during the development process  Processing chemistry that is contaminated, too hot, too cold or improperly mixed

4. Magnification  An image that appears larger than its actual size  Affected by Target-Receptor distance  When a longer PID is used there is less divergence of x-rays

 Also affected by Object-Receptor distance  the image receptor should be placed as close o the tooth as possible to minimize magnification

5. Distortion (Noise)

 Image that is different than

the original  Affected by the object-

receptor alignment 

Use paralleling technique whenever possible so the xray beam is directed perpendicular to the tooth and receptor

Elongated and Foreshortened Images

Film Processing  Diagnostically acceptable film-based radiographs are dependent on the care and maintenance of the processing solutions, equipment and film  The manufacturer’s instructions for the storage, mixing and use of the processing solutions must be followed  Processing solutions start to deteriorate when exposed to air and

with continued use, lose strength  Equipment must be maintained for optimal working conditions.  Film must be stored properly

Considerations for Film-based offices  An accurate thermometer  Check solutions and water daily and follow manufacturer

directions  Solutions must be changed 2-4weeks depending on use

 Equipment must be kept clean to avoid contamination

and artifact formation  Film should be stored in a cool, dry place and checked if

expired

Considerations for Film-based offices  Safe light areas and daylight loaders must be

maintained and checked  Appropriate bulbs (low watt white light bulbs)

 Light safe environment (filters should be specific for

film used; orange for some and red for all; covers)

 Care when handling film and processing  Use of viewboxes

Cassettes and Screens  Checked for wear and cleanliness  If discoloring or damaged, replace  Clean screens with appropriate cleaner from

manufacturer  No rubbing alcohol or water

 Check closure mechanism

Checking the Closure Mechanism Film-based  If you suspect a light leak, place an undeveloped film in the cassette, hold up the cassette with the hinged side facing a bright light for three minutes and develop. If light is leaking into the cassette, dark areas will appear along the edges of the processed film.

Checking the Closure Mechanism Digital  If you suspect a light leak, place an exposed

phosphorous plate in the cassette, hold up the cassette with the hinged side facing a bright light for three minutes and develop. If light is leaking into the cassette, light areas will appear along the edges on the image.

Quality Assurance Procedures Manual Mission Statement

Legislation

Quality Assurance Tests

What is your objective? Who does what? The Rules Checklists and forms

Test Procedures

How to perform the tests

Reports & Documentation

Information about service, audits, training, and equipment

Same for both systems: • Repeat Analysis • X-ray Equipment • Screens and Cassettes • Technique chart

Common Tests  Visual Inspection and Preventive Maintenance  Safety (SPM) Inspection  Every 3 years for older units and every 5

for new units  You are responsible for keeping track of when this is needed to be done

 Protective Equipment Check  Technique Chart

X-ray Equipment 1. Visual Inspection  Look for anything out of the ordinary like loose screws, frayed cables or sharp edges. Ensure the tube head does not drift when placed in a variety of positions.  Inspect the lead aprons for any tears. Tears cannot exceed 1 centimeter in any critical area 2. Safety Preventative Maintenance Test  Every 3 years by technician 3. Pan Slit Alignment Test (not required)

Protective Equipment Check  Lay flat lead apron or

thyroid collar  Feel front to back for cracks, especially at neck and bodice  If tear suspected, take radiograph  Tears > 1 cm in critical area = replace lead garment

Faulty Lead Aprons

• Dental professionals should collaborate with one another to problem solve issues they may be having with radiographs

• If you are doing a lot of retakes, a Repeat Analysis Test is a great tool to measure this • No more than 5%

Critical Criteria Bitewing  Interproximal contacts have no (minimal overlap)  Distals of 3’s and 7’s (8’s) present  Occlusal plane parallel with bottom of image  Good density, contrast, and no distortion

PA’s  2mm of bone around the apices  Minimal overlap in contacts  Occlusal plane parallel with bottom of image  good density, contrast and no distortion

Imaging Quality Control

Tools for Conventional Film Digital Thermometer – developer temperature

Radiographic Check Device – System Constancy

Developer Temperature  Check the manufacturer recommendations for the

optimal temperature range of the processor you use within your office  For example, the developer temperature recommended for the Perio Pro is 75 degrees Fahrenheit  Using a reliable thermometer, the temperature must be measured and charted three times per week using the QA Processing Chart sheet to ensure consistency within 1 degree.

QA Processing Chart Processor

Developer/Fixer

Month/Year

Film Type

Initial each day in which the chemical levels were checked and/or replenished.

Chemical Levels

1 2

3 4

5

6

7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

   

Record the temperature at the time that the system constancy test was performed. +4 F

83°F

1 2

3 4

5

6

• • •

2

-2 0.02 -4 F

7 8

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

•

Plot the system constancy for the one x-ray unit designated as the QA unit. Perform this test throughout the week to ensure consistent processing with this system. X-ray Unit +2

4

+1

-1 -2

kVp / mA

1 2

3 4

5

6

7 8

• • • •

Timer setting

Reference Step

9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31

Read the manufacturers instructions! • The manufacturer recommendations for the Perio Pro suggest changing the solutions every 300-350 radiographs or every 2 weeks- whichever comes first

Conventional Film - Other Tests  Chemical Levels and water baths

 X-ray Exposure Test  Processor Cleaning  Darkroom / Safelight 

Darkroom and Daylight Loaders  The darkroom or day light loader must be checked

every year for any light leaks  For dark rooms, close the door and turn off the safe light.

QC Test Tool and Unexposed Film

Conventional Film – System Constancy

Film

Copper Plate

Processed Film

1 2 3 4 5 6 7

Monitor Strip

Find the matching step to the current film. If it’s within range – All OK

Out of Range? Corrective action is required.

Insert Unexposed Film

Align X-ray Tube Head

EXPOSURE!

Match the Step

Processed Film

Imaging Quality Control

Digital X-ray Tests

Tools for Digital Imaging Step Wedge – image artifact evaluation

Test Patterns – video monitor quality assurance

Dexis

Digital Imaging – Video Monitor QA • View Test Pattern on your monitor • Adjust the brightness and contrast for optimal viewing conditions •Evaluate your monitor for resolution, contrast and distortion SMPTE (Society of Motion Pictures and Television Engineers)

BWH Test Pattern

Measures grey levels

Dexis Sensors  Indicates the amount of radiation exposed to the

sensor Too little radiation

Way too little radiation Too much radiation Way too much radiation

Digital Imaging – Image Receptor Artifact Evaluation Acceptable Image This is a picture of the image receptor itself. The step wedge creates the light and dark regions. This is used to allow the optimization program to find proper contrast for viewing.

Damaged Image Receptor This image receptor is scratched, dented and bent. These artifacts will be overlaid in the images of the patient and may interfere with diagnosis. It is time to replace this image receptor.

Digital Artifacts

Crease The phosphor has been bent sufficiently to cause this damage to the phosphor plate

Digital Artifacts Hemostat Damage The phosphor has been permanently damaged in the corner – be sure to use this plate in the same orientation each time

Digital System - Reference Image Good Match!  The steps line up  The quality of the images are consistent Same distance every time!

Step wedge

Image receptor

Problems! The steps do not match, which indicates a problem with the imaging system. Check the timer setting, set up distance, and image receptor.

Cone Beam CT vs. Digital Pan Dose Comparison: ~100 µSv for Cone Beam CT1 ~ 5 µSv for digital Panoramic2

Cone Beam CT delivers Up to 20 x the radiation dose of digital Pan

1.

Imaging Sciences International, i-CAT Operator’s Manual, June 2007

2.

Gijbels F, Jacobs R, Debaveye D, Verlinden S, Bogaerts R, Sanderink G. Dosimetry of digital panoramic imaging. Part I: Patient exposure. Dentomaxillofacial Radiology, 2005.

Postal Quality Assurance Test Have you seen one of these lately? • The packet contains crystals that can measure radiation. • Put a film into the packet and expose it on adult BW setting. • Return the packet, the processed film and completed information sheet to the Radiation Safety Unit for analysis. • They will report your x-ray unit’s performance to you.

Summary  Quality Assurance ensures diagnostic integrity of

images  Troubleshoots operator/equipment error

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