Radiology & IRMER Flashcards

What does the 'fovea centralis' on the hard palate represent radiographically?

Answer: Not a radiographic term — fovea palatinae are bilateral depressions at the junction of hard and soft palate, visible clinically for posterior denture border

Fovea palatinae are bilateral depressions on the posterior hard palate at the hard-soft palate junction; they serve as clinical landmarks for the posterior palatal seal of complete dentures but are not a primary radiographic finding.

What radiographic feature suggests a malignant rather than benign lesion in the jaw?

Answer: Ill-defined 'moth-eaten' borders, cortical destruction, and periosteal reaction ('sunray spiculation' in osteosarcoma)

Malignant jaw lesions characteristically show poorly defined irregular borders ('moth-eaten' or permeative), cortical destruction, soft tissue involvement, and periosteal reactions such as Codman's triangle or sunray spiculation.

What is the Nasopalatine duct cyst (NPC) classic radiographic appearance?

Answer: Well-defined, heart-shaped or oval corticated radiolucency in the anterior maxilla between and above the central incisors (incisive canal/nasopalatine region)

The NPC appears as a well-defined, corticated, often heart-shaped radiolucency in the incisive canal region; vital central incisors help distinguish it from periapical pathology — the teeth are vital.

What cone beam CT (CBCT) field of view (FOV) is recommended for implant planning?

Answer: Limited FOV (5 × 5 cm or 8 × 8 cm) focused on the implant site — minimises dose while providing accurate measurement

ALARP requires the smallest FOV that provides the required diagnostic information; limited FOV CBCTs (5 × 5 or 8 × 8 cm) are recommended for implant site assessment, significantly reducing dose compared to large FOV scans.

What is the effect of increasing mAs (milliampere-seconds) on a dental radiograph?

Answer: Increases the number of X-ray photons produced, increasing image density (exposure/film blackening) — used to correct underexposure

Increasing mAs increases the quantity (number) of photons produced by increasing tube current or exposure time; this directly increases image density and is the primary control for image exposure (overexposure/underexposure).

What is the maximum permissible annual occupational dose limit for a classified radiation worker in the UK?

Answer: 20 mSv per year (effective dose limit for occupationally exposed workers under IRR 2017)

IRR 2017 sets the annual dose limit for classified radiation workers at 20 mSv effective dose (and 500 mSv for extremities/skin); the limit for members of the public is 1 mSv/year.