Quality Assurance in Dental Radiography Chapter 17 Quality Assurance in Dental Radiography

Quality Assurance – planning and carrying out procedures to assure quality radiographs and max. diagnosis, while minimizing exposure to patients and personnel. ALARA concept – “as low as reasonably achievable”. Use min. amt. of radiation to get job done; increase quality of radiographs and decrease re-takes.

Quality Control – series of tests to assure radiographic system is functioning properly and radiographs are of acceptable quality. Quality Control tests should be conducted for x-ray machines, darkroom, processing equip., film and processing solutions. Logs of tests performed, dates, results and corrective action should be kept.

Quality Control Tests for Dental X-ray Machines Beam alignment Collimation Filtration (beam quality) Radiation Output Timer accuracy Tube head stability Accuracy of mA and kV Focal spot size **most of these tests must be done by qualified personnel.

Output Test Can be done using step wedge device. Layered metal steps used to determine film density and contrast (may also be used to test strength of processing chemicals). Can be bought or made in office. Divide piece of cardboard (size of film) into thirds. Leave first third uncovered, cover remaining two thirds with 2 pieces of lead foil. Cover final third with 3 more pieces of lead foil, tape down.

See procedures for testing output with stepwedge (x-ray checker) on pg Use 3 films from same package. Expose 1 with stepwedge on top (tubehead perpendicular, 1 inch from film; use molar setting. Expose 2nd film same after some time. Expose 3rd film same after time. Process all at same time (to ensure not a chemical problem) All films should have same density and contrast, output ok; if different, have machine tested.

Expose and process film periodically View radiographs side by side to compare density. Can be used to check chemical strength; expose and process one, save; expose and process another after week or two, then compare… If densities match, chemicals ok. If densities do not match, may need to change chemicals.

If developer deteriorates and loses strength, radiograph will lighten. Can keep supply of reference films to check chemicals daily, weekly, etc. See Procedure 17-4 for details.

Tubehead Stability Check for drifting of tubehead by placing in different positions. Must be adjusted by technicians. To avoid problems, place folded into a closed position against wall.

Darkroom should be adequately ventilated Free from chemical fumes Within temp. ranges Light tight Have proper safelight and filter Proper wattage Filter compatible with film used 4 ft. from working area

Test for light leaks in darkroom: Close door and turn off lights (including safelight) Leaks become visible after about 5 minutes (when eyes become accustomed to dark) Fix light leaks (can cause film “fogging”)

Testing of Safelight: Using “coin test” Turn off all lights Unwrap unexposed (slightly exposed works better) dental film Turn on safelight Place coin on film emulsion for 2-4 minutes Process film **if outline of coin appears, safelight is not safe for use; filter may be scratched; bulb wattage might be too strong; safelight too close to film, or working surface.

Automatic Processors Check to make sure water is on and circulating Check levels of chemicals Replenishment (automatic or manual) Temperatures maintained Clean with proper liquids Feed films carefully (bent films get stuck and jam in machine)

Autoprocessors con’t Feed slowly and straight Begin day by processing unexposed film with safelight, should be clear (bluish tint) and dry. If not, check solutions, safelight, etc. Then, process film exposed to light, should be black and dry.

Manual Processing Use thermometer to monitor temp. Stir compartments in morning, not mixing paddles. Keep work area clean, do not lay film on wet or dirty countertops.

Periodically check: cassettes for panorex for warping, light leaks, and screen-film contact. intensifying screens for cleanliness and scratches; dirt can leave white specks on radiograph. Viewboxes for uniform, subdued light; some viewboxes have fluorescent light tubes that glow after turned off.

Use fresh film Properly store in cool, dry place; away from radiation, chemicals, light, etc. Use by expiration date. Rotate stock and use oldest film first.

Quality Assurance Programs should include: Written plan Monitoring and maintenance schedule Assigned staff responsibilities Record-keeping log and periodic evaluation

Acceptable radiographs should: Show entire area to be studied with min. distortion. Have proper density. Exhibit sufficient definition and sharpness. Have sufficient contrast.

Retakes should not be taken without knowing why. Causes for substandard radiographs: Equipment problems Processing errors Personnel errors Patient problems

Check chemical levels daily Radiation monitoring badges should be worn, if provided. Lead aprons and thyroid collars should be inspected and maintained on regular basis; do not fold aprons!