Errors - Theory

Characteristics of quality radiograph

Max detail & distortion. Opt. density & contrast.

Artefact

Artificially created phenomenon reducing image quality.

The big 3

Positioning, exposure & processing.

Positioning errors

Pt preparation, film placement artifacts & projection errors.

Positioning errors - PT prep

Shadow artifacts & blurred image.

Positioning errors - Film placement artifacts

Lead foil artifact, ID dot, cut off roots/crowns, black line & distortion.

Positioning errors - projection errors

Incorrect vertical angulation, incorrect horizontal angulation & partial image.

Exposure errors

blank images, under/over-exposure, black image, double expo & partial image (cone cutting)

Processing errors - Handling errors

Fingerprints, scratched films & sunlight/UV.

Projection errors - incorrect vertical angulation (CORRECT + CORRECT BISECTOR & PARALLEL)

• Vertical angulation = tube/beam moving up or down. 

• Correct: Vertical dimension of tooth in xray corresponds w/reality.

• Bisector: Beam perpen. to bisector dividing angle b/w l.a. of tooth & film.

• Parallel: Beam perpen. to l.a. of tooth.

Projection errors - incorrect vertical angulation BEAM TOO SMALL & TOO LARGE

• Central beam too large angle: Image shortened.

• Central beam too small: Image elongated. 

Projection errors - incorrect horizontal angulation CORRECT

• Horizontal angulation: Lateral movement of tube/beam. 

• Central beam is perpen. to vestibular surfaces of teeth & parallel to M/D surfaces of teeth. 

• Central beam should be dir. via interproximal contact areas. 

Projection errors - incorrect horizontal angulation INCORRECT

• Inc. hor. central beam projection: Image has overlap.

Exposure error: blank image

No radiation recieved. Xray machine turned off/broken. Image is blank.

Exposure error: Black image

Film exposed to sunlight. Image development turns black.

Exposure error: Underexposure

“Low density.” Result of insufficient radiation. Image too bright.

Exposure error: Overexposure.

“High density.” Result of excessive radiation. Image too dark.

Exposure error: Double exposure

The same receptor/film used twice. Exposes patient to double radiation dose. 

Processing errors

Fingerprints & scratched films.

Storage & processing

Image mirrored if incorrectly inserted into reader. Xray saved for wrong patient.