QA in Dental Radiography - Quick Reference

Quality Assurance in Dental Radiography - Quick Reference

• QA Definition

  • QA is a systematic framework to ensure diagnostic quality of radiographs while protecting patients and staff from excess exposure.

  • QA includes: quality administration and quality control.

• QA Objectives (essential points)

  • Every radiographic procedure is justified based on prior clinical evaluation.

  • Images provide diagnostic information and reflect appropriate technique (may require peer review/refresher).

  • Identify deficiencies before image quality is compromised (saves time and cost).

  • Maintain high standards of image quality and safety.

  • Keep patient and occupational exposure at ALARA; perform yearly output tests.

  • Reduce retakes and unnecessary exposure.

Quality Administration

• Assign QA responsibilities – tasks should be shared among staff.

• Proper record keeping is mandatory; poor records can lead to fines (e.g., up to $50,000); keep test results for 6 years.

• The Act requires that tests be performed and records maintained of results and corrective actions.

• QA log should include tests, repairs, and corrective actions.

• Monitor maintenance schedules to ensure QA tests are performed.

• Supplies: ensure proper storage and handling; track usage and quality.

• Sharing radiographs with third parties

  • Use secure email with strong encryption or approved services (e.g., CDA e-Referral Service) per RCDSO guidance.

Quality Control (QC)

• QC = specific tests used to maintain and monitor x-ray units, supplies, film processing (where applicable), and imaging equipment.

• Goal: avoid unnecessary exposure by understanding QC procedures for units, films, screens, and viewing equipment.

Equipment & Supplies (Film-based/Analogue)

• Film-based systems require QC of machines, film, screens, cassettes, and viewing systems.

• All x-ray machines must be inspected annually and calibrated by a qualified technician.

• Yearly QC tests include: output, collimation, beam alignment, calibration, and HVL.

• HVL: \text{HVL} = \text{thickness of aluminum required to reduce beam intensity by }50\%.

• Film storage: store properly; test new boxes by processing a film; expect a clear film with a blue tinge; fogged film indicates discard.

• Screens & cassettes: check for dirt/scratches; clean monthly; use antistatic solution; replace scratched screens; inspect light leaks.

• Viewing equipment: verify working viewbox; inspect and clean plexiglass; replace bulbs as needed.

• Film processing: daily QC to avoid retakes; monitor solution strength, time, temperature, and processing chemistry.

Dark Room & Processing (Analogue)

• Darkroom light-tightness: test monthly before safelight checks.

• Light leak test: close door, turn off lights, check for light leaks; seal as needed.

• Safelight coin test: use unexposed film, a coin, and safelight for 3–4 minutes; processing should show no fog; panoramic film is more sensitive.

• Processing equipment QC: check time/temperature of solutions; monitor water bath; ensure fresh solutions; follow manufacturer instructions.

• Daily tests: run two test films and a stepwedge to monitor processing consistency.

• Automatic processor QC: expose one film to light and process with unexposed; expect clear/blue-tinted film; exposed film should be black and dry.

• Processing solutions: top up daily; change every 3–4 weeks or per manufacturer guidance; process more films -> greater chemical depletion.

• Stepwedge testing: use a fresh reference film and stepwedge; compare daily films to reference; if density degradation > 2 steps, replace solutions and retake reference.

• Reference film management: keep a daily reference after solution changes.

WHMIS & Waste Management

• WHMIS (Workplace Hazardous Materials Information System)

  • Legislation from 1987; provides information on first aid, precautions, and MSDS.

  • Addresses developers (pH >7) and fixers (pH <7); accidents can occur during mixing and splashes; proper storage information.

• Waste disposal (three types):

  • Waste solids

  • X-ray processing effluent (liquids from developer and fixer)

  • Medical waste (potentially infectious)

• Waste solids examples: cardboard boxes, foil wraps, banding, trays, black paper, lead foil (recovery option), old films can be recovered, bottles from fixer/developer recyclable.

• Effluent: silver can be recovered via silver recovery units; developer is alkaline, fixer acidic; when mixed, effluent is often neutral and within sewer limits; offices rarely exceed discharge limits; do not discharge effluent indiscriminately.

Waste Reduction & Recycling (Lead & Chemical Wastes in Ontario)

• Lead containing wastes: lead foil packets, lead aprons; collect as per supplier guidance; follow local sewer by-laws; participate in recycling.

• Chemicals: consult MSDS for composition; follow municipal requirements for disposal.

• Best Practice: desilvering and recycling programs; use approved waste carriers for disposal.

Common Processing & Handling Errors (essential highlights)

• Overdeveloped film: very dark; cause = improper solution strength or prolonged development; remedy = adjust time/temp; QA daily.

• Underdeveloped film: light appearance; cause = insufficient development; remedy = replenish/change solutions and adjust time/temp.

• Fogged film: overall gray; cause = improper safelight, storage, or old film; remedy = QA program and proper handling; avoid bright lights.

• Stained film: spots; cause = dirty working surface or incorrect solutions; remedy = clean surfaces and correct chemistry.

• Discolored film: opaque brown/tan or green/pink; causes include solution issues or dirty rollers; remedy = fixers/solutions checks.

• Clear films: no image; cause = emulsion washed off; remedy = avoid overnight washes and check rollers.

• Lost films: not secured on racks; remedy = ensure proper racking and daily QA run.

• Reticulation: cracked look; cause = sudden temp change between developer and water; remedy = monitor temp.

• Torn emulsion: transparent patches; cause = films overlapping during drying; remedy = feed films slowly.

• Scratched films: radiopaque lines; remedy = handle films carefully; avoid sharp nails/jewellery.

• Creased films: black lines/crests; cause = excessive handling/curled film; remedy = curve gently and use smaller film.

• Finger prints: fingerprints on emulsion; remedy = clean hands and handle by edges only; maintain darkroom hygiene.

• Static marks: black vein-like patterns; cause = static electricity from friction; remedy = reduce movement and humidity; avoid carpet; handle carefully.

• Overlapped films: films stick together; remedy = separate films and space during loading; wait briefly between films.

Quality Control for Digital Radiography

• Digital QA parallels analogue QA: ensure imaging units, sensors, and computers meet standards.

• Digital sensors: direct sensors (fragile; costly) vs phosphor plates (less expensive but bendable); handle with care and infection control.

• Wires/connectors: inspect for damage; data backups daily; software updates and overall upkeep.

• Special digital tests: use test objects/kits to check erasure cycle efficiency, sensitivity, uniformity, blurring, contrast, and resolution.

Best Practices for Digital Imaging Equipment (Overview)

• All dental x-ray machines require annual testing regardless of modality (film or digital).

• Regular sensor inspection for scratching, bending, and wear; infection control is critical since sensors are reused.

• Direct digital sensors are expensive (approx. 3000$-$10,000 per sensor).

• Indirect systems (phosphor plates) are cheaper but require careful handling.

• Computer system: daily data backup; update software; verify hardware integrity.

Disposal & Environmental Compliance (Ontario)

• Best Management Practices for silver-containing wastes

  • Separate streams; desilvered solutions; silver recovery units; proper labeling; disposal via approved carriers.

• Best Management Practices for lead-containing and other chemical wastes

  • Collect lead foil packets and items; follow chemical MSDS; consult local sewer by-laws; participate in manufacturer recycling.

• Environment Canada guidance included; follow local regulations for disposal and recycling programs.

Quick Reference Formulas & Key Terms

• \text{HVL} = \text{thickness of aluminum required to reduce beam intensity by }50\%.$$

• ALARA: As Low As Reasonably Achievable (exposure safety principle).

• Stepwedge: device with layered aluminum steps to assess imaging density and solution strength; compare daily films to a reference to detect degradation.

• Reference film: daily reference created after new solution batches; if densities degrade by >2 steps, replace solutions and reset reference.

Core Compliance & Documentation

• Maintain QA logs: tests, repairs, corrective actions, and maintenance schedules.

• Secure transmission of radiographs to third parties; use approved secure methods.

• Regular WHMIS training and MSDS review; keep records of chemical handling and disposal.