Computer generated odontoid peg “fracture”, a cause for concern?
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Computer generated odontoid peg ‘‘fracture’’, a cause for concern? Andrew Collier and David King York District Hospital, Wigginton Road, York YO3 7HE, U.K. Injury, Vol. 29, No. 9, 719–723, 1998 Introduction A computed radiography system (Fuji, AC3) is used in our casualty radiology department. Advantages include reduced radiation dose, better images and image manipulation (for soft tissue definition and image size) [1]. Case report A patient involved in a road traffic accident with entrapment underwent assessment, resuscitation and re-evaluation in accordance with ATLS guidelines [2]. X-ray images of the cervical spine using three views were taken. The through-mouth view showed a type 2 [3] peg fracture (Figure 1), not seen on the lateral view, as does occur in a number of cases [2, 4]. A CT scan of the cervical spine was performed to rule out any non-contiguous injury. This failed to confirm the injury to C 2 (Figure 2a and b) as did AP and lateral plain film X-ray tomograms (Figure 3a and b) and open mouth peg view, repeated using conventional film radiography (Figure 4). Injury Vol. 29, No. 9, pp. 719–723, 1998 # 1998 Elsevier Science Ltd. All rights reserved Printed in Great Britain 0020-1383/98 $19.00 + 0.00 PII: S0020-1383(98)00154-5 Figure 1.
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Transcript of Computer generated odontoid peg “fracture”, a cause for concern?
Computer generated odontoid peg ``fracture'', acause for concern?
Andrew Collier and David KingYork District Hospital, Wigginton Road, York YO3 7HE, U.K.
Injury, Vol. 29, No. 9, 719±723, 1998
Introduction
A computed radiography system (Fuji, AC3) is usedin our casualty radiology department. Advantagesinclude reduced radiation dose, better images andimage manipulation (for soft tissue definition andimage size) [1].
Case report
A patient involved in a road traffic accident withentrapment underwent assessment, resuscitation
and re-evaluation in accordance with ATLS
guidelines [2].
X-ray images of the cervical spine using three
views were taken. The through-mouth view showed
a type 2 [3] peg fracture (Figure 1), not seen on the
lateral view, as does occur in a number of
cases [2, 4].
A CT scan of the cervical spine was performed to
rule out any non-contiguous injury. This failed to
confirm the injury to C 2 (Figure 2a and b) as did
AP and lateral plain film X-ray tomograms (Figure 3a
and b) and open mouth peg view, repeated using
conventional film radiography (Figure 4).
Injury Vol. 29, No. 9, pp. 719±723, 1998# 1998 Elsevier Science Ltd. All rights reserved
Printed in Great Britain0020-1383/98 $19.00 + 0.00
PII: S0020-1383(98)00154-5
Figure 1.
Figure 2.
720 Injury: International Journal of the Care of the Injured Vol. 29, No 9, 1998
Figure 3.
Case reports 721
Figure 4.
Figure 5.
722 Injury: International Journal of the Care of the Injured Vol. 29, No 9, 1998
Discussion
The manufacturers (Fuji, Japan) inform us that thisimaging technique has potential for generatingerrors if certain technical details are not adhered to(personal communication).
The primary cause for the ``fracture'' artefact inthis case was an incorrect setting of the grey scaleby the computed radiography system. This scale isset by reading the cassette, and assigning the lightestpart of the grey scale to that area that has beenexposed least.
The actual through-mouth image was a coneddown area in the centre of an oversized film, with apartial exposure of the surrounding area of the cas-sette by scattered radiation (Figure 5). This was mis-read as part of the image, and the lowest part of thegrey scale assigned to this scatter area, resulting ininsufficient tonal values for more exposed parts ofthe recognised area. Such areas were assigned a uni-form black appearance, in this case corresponding toa linear area overlying the base of the odontoid peg,simulating a fracture.
Methods of avoiding errors include the use of agrid, and a correctly sized cassette. Both of thesereduce the scatter area. Finally, care in the set up ofthe computed radiography system is important in sofar as the setting of the lowest limits of grey scale.
Conclusion
This case illustrates the need for continued care inthe use and interpretation of films obtained throughnew imaging techniques, and emphasises thatawareness of new artefacts is important when intro-ducing any new imaging system into a departmentas is the need to adhere to the manufacturers'advice.
References
1 Murphy M. D., Quale J. L., Martin N. L., Bramble J. M., CookL. T. and Dwyer S. J. III Computed radiography in musculos-keletal imaging: state of the art. American Journal ofRoentgenology 1992; 158: 19±27.
2 ATLS Course Student Manual, 5th Edn. American College ofSurgeons, 1993.
3 Anderson L. D. and D'Alonso P. T. Odontoid process of theaxis. Journal of Bone and Joint Surgery 1974; 56A: 1663±1674.
4 Mace S. E. Unstable occult cervical spine fracture. Annals ofEmergency Medicine 1991; 20: 1373.
Paper accepted 12 June 1998.
Requests for reprints should be addressed to: Mr A. Collier,Friarage Hospital, Northallerton, N. Yorks, U.K. Fax: +44-1609-764638; E-mail: [email protected].
Case reports 723
