Radiology & Radiation Protection Flashcards

What is the purpose of a 'dental panoramic tomograph' (DPT/OPG) compared to periapical radiographs?

Answer: DPT provides a broad overview of the dentition, alveolar bone, mandible, and TMJ in a single image but with less detail; periapicals provide superior detail of individual teeth and periapical areas

DPT (Panoramic/OPG) provides a single overview image of the full dentition, alveolar bone, sinuses, and TMJ regions — useful for initial assessments, impacted teeth, and pathology screening. Periapicals offer superior detail for individual teeth and periapical regions.

What is the 'dead man's handle' (deadman switch) concept in dental radiography?

Answer: The X-ray exposure switch must be actively held by the operator — releasing it automatically stops exposure, preventing accidental prolonged radiation release

The deadman switch (non-latching exposure switch) ensures the operator must actively maintain pressure throughout exposure. Releasing the switch immediately terminates exposure, preventing accidental prolonged irradiation.

What is the recommended minimum distance the operator should stand from the X-ray tube head during exposure?

Answer: At least 1.5–2 metres away, outside the primary beam, ideally behind a lead screen or wall

Operators should stand at least 1.5–2 metres from the tube head, outside the primary beam (not at 90° to it), and ideally behind a structural barrier during dental X-ray exposures.

What is the significance of a 'cone beam CT' (CBCT) scan in dental practice compared to conventional dental X-rays?

Answer: CBCT provides 3D volumetric imaging but delivers significantly higher radiation dose than 2D dental radiographs — use must be justified by need for 3D information unavailable from conventional imaging

CBCT provides three-dimensional imaging crucial for implant planning, surgical anatomy, and complex endodontics. However, the effective dose is significantly higher than conventional dental radiographs (approximately 40–500 µSv), requiring strict justification.

What is 'fog' on a dental radiograph and what causes it?

Answer: Overall grey, low-contrast appearance caused by: light leakage in darkroom, expired film, improper processing, or secondary/scatter radiation reaching the film

Radiographic fog is a general increase in film density reducing contrast and diagnostic quality. Causes include: secondary/scatter radiation, light leaks, outdated film, improper processing temperatures, or chemical contamination.

Which radiographic technique is used to assess the alveolar crest bone level in periodontal disease?

Answer: Horizontal bitewing radiographs

Horizontal bitewing radiographs are the gold standard for assessing alveolar bone levels in the premolar and molar regions, clearly showing the interdental crest bone height relative to the cemento-enamel junction.