Radiography
Collimation error – ‘cone cutting’ Fig 3
Fig 2 Frankfort plane error – patient positioned ‘chin up’ TABLE 2
Results: Panoramic with faults
without faults Cone cutting Contrast
Vertical angulation errors Horizontal angulation errors Scratches
Delaminated plates Cracked plates
Anterior/Posterior Errors Patient anterior Patient posterior
Frankfort plane errors Chin up
Chin down Continued »
such that the intra-pupillary line is parallel to the floor (no evidence of tilting of the image).
Discussion In our sample of intra-oral radiographs, 84 per cent of the images had at least one common radiographic error present. This falls well short of our target of 70 per cent of images being devoid of common radiographic errors. The most common error was
a ‘contrast’ error. As the images were digitally transferred to Dundee Dental Hospital, it was impossible to say if the contrast issues were due to an exposure error or post image capture alteration. Conversely,
% of Radiographs 92 8
34 6
56 0
54 28 60
% of Radiographs 2 4
% of Radiographs 24 32
post image capture alteration may also have been used in these images to camouflage incorrect exposure. Other significant errors included vertical or horizontal image angulation discrepan- cies. These were identified due to image elongation/fore- shortening or the presence of avoidable overlap between adjacent teeth respectively. This may be due to failure to use commonly accepted methods of capturing accurate images, e.g. the use of beam aiming devices. This finding may open up the potential future project to lead and assess image capture methods utilised by referring practitioners. Of the panoramic radio-
graphs, 92 per cent were found to contain errors in
Fig 8
Incorrect horizontal angulation Fig 7
exposure, patient positioning, radiograph equipment or image processing/transfer. This, again, was well below our target of having 70 per cent of images devoid of common radiographic errors. Evidence of air shadows was
the most common radiographic error identified on panoramic images. In the sample popula- tion, 60 per cent of images were found to have an avoid- able air shadow, i.e. patient not positioning their tongue against their palate present on the image and detracting from the information yielded. Errors in the positioning of
the patient’s Frankfort plane were found also to be common, with 32 per cent of patients being positioned ‘chin down’ and 24 per cent of patients being positioned ‘chin up’. This resulted in an increased or reduced angle of the occlusal plane on the image. Additionally, 54 per cent
of patients were found to be tilted when the panoramic images were assessed. This was identified through different reference markers on each side of the image appearing higher or lower than their contralateral counterpart, most commonly
Missing apices and vertical angulation error
the condyle was used for assessment. Rotation (patient rotation upon positioning) and contrast errors were also found in significant numbers in our sample. During the planning stage of
the audit, the radiographs were to initially be scored according to the three-point scoring scale from the FGDP guidelines2. During the calibration stage, the audit team independently scored the radiographs using errors present on the image. It became evident that the subjective nature of this scoring system caused an inability for the assessors to come to an agreement on individual image scoring. This
Continued »
ABOUT THE AUTHORS
Andrew MacInnes BDS (hons) MFDS RCPS (Glasg) is a senior house officer in the restorative department at Dundee Dental Hospital.
Fig 6
Delaminated and collimation error Fig 5
Frankfort plane error – patient positioned ‘chin up’
Delaminated and bent plate Fig 4
Donald Thomson BDS, FDS RCSEd DDR RCR is a consultant oral and maxillofacial radiologist at Dundee Dental Hospital. Alison Menhinick is a superin- tendent radiographer at Dundee Dental Hospital.
Scottish Dental magazine 61
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