Radiology · patient case question
Which is the most likely cause of Film A's appearance?
Patient case: Two radiographs of poor quality
Patient: Radiographic quality assurance review
Chief Complaint: Not applicable.
Background: Two periapical radiographs from the same day are being reviewed. Manual processing is used in this practice, and the developer solution has not been replenished for some weeks.
Findings: Film A appears uniformly LIGHT, with low overall density and poor contrast between enamel, dentine and bone. Film B, taken later the same day, appears uniformly DARK.
Show answer and explanation
Correct answer: D. Insufficient exposure — mA, kVp or time set too low, or depleted or cold developer
- A. Developer that is too WARM accelerates the reaction and causes OVERDEVELOPMENT, producing a DARK film. The direction of this error is the whole point: cold developer lightens, warm developer darkens.
- B. Excessive exposure produces a DARK film, because more silver halide crystals are exposed and subsequently reduced to metallic silver.
- C. Overdevelopment darkens the film, by reducing more crystals than intended.
- D. CORRECT. A LIGHT film means too few silver halide crystals were exposed and reduced. The causes divide into two groups. EXPOSURE causes: mA, kVp or exposure time set too low, or an excessive source-to-film distance. PROCESSING causes: developer that is DEPLETED, DILUTED or COLD, or insufficient development time. Cold or exhausted developer is the classic and easily missed cause — and the stem points directly at it by mentioning that the solution has not been replenished.
Note: Distinguish a LIGHT film from a FOGGED one. Fog produces a grey, low-contrast image rather than a pale one, and is caused by light leaks, stray radiation, outdated or heat-damaged film, or contaminated or overwarm processing solutions. An OVER-FIXED film appears bleached and pale for a different reason again — prolonged fixation dissolves away reduced silver from the emulsion.