MFDS Radiology and Radiography 2

Question 1

On a dental panoramic tomograph (DPT/OPG), which anatomical structures are commonly misidentified as pathology?

Accepted Answer

The mental foramen, incisive canal, maxillary sinus floor, and the ghost image of the opposite mandibular angle

Answer

Only the zygomatic arch can be misidentified

Answer

No normal structures are ever confused with pathology

Answer

The tonsils and adenoids are the only structures commonly misidentified

Question 2

What is the bisecting angle technique for periapical radiography, and when might it be preferred over the paralleling technique?

Accepted Answer

The X-ray beam is directed perpendicular to the bisector of the angle formed between the long axis of the tooth and the film/sensor plane; it may be preferred when palatal/floor of mouth anatomy prevents parallel placement of the sensor

Answer

It involves bisecting the tooth in half for measurement purposes

Answer

It is a technique used only for panoramic radiography

Answer

The film is placed at 45 degrees to the tooth and exposed from behind the patient

Question 3

A patient requires a radiographic assessment of the TMJ (temporomandibular joint). Which imaging modality provides the best visualisation of the articular disc and soft tissue components?

Accepted Answer

MRI (magnetic resonance imaging)

Answer

Periapical radiograph

Answer

Dental panoramic tomograph (DPT)

Answer

Lateral cephalometric radiograph

Question 4

What quality assurance measures should be routinely performed on dental X-ray equipment in the UK?

Accepted Answer

Regular testing of tube output, timer accuracy, beam alignment, film processing (if applicable), image quality using test objects, and maintaining QA records as required by IRR17 and IRMER 2017

Answer

No quality assurance is required for dental X-ray equipment

Answer

Only annual servicing by the manufacturer is required

Answer

Quality checks are only needed when the equipment is new

Question 5

What is the typical effective dose of a dental panoramic tomograph (DPT/OPG) and how does it compare to other dental radiographic examinations?

Accepted Answer

A DPT gives an effective dose of approximately 5-25 microsieverts, equivalent to approximately 2-8 periapical radiographs, and much less than a medical CT scan

Answer

A DPT gives a dose of approximately 50 mSv, much higher than a chest X-ray

Answer

A DPT gives zero radiation dose as it uses ultrasound

Answer

A DPT gives approximately 1 millisievert, equivalent to a full mouth series

Question 6

What are the radiographic features of a dentigerous cyst on a dental panoramic tomograph?

Accepted Answer

A well-defined, unilocular radiolucency with a corticated margin, attached to the cemento-enamel junction of an unerupted tooth and surrounding its crown

Answer

A diffuse, ill-defined radiopacity surrounding an erupted tooth

Answer

A multilocular radiolucency with a soap-bubble appearance not associated with any tooth

Answer

A radiopaque mass replacing the normal tooth structure