An investigation into the accuracy of orbital X-rays, when using CR, in detecting ferromagnetic intraocular foreign bodies.

PURPOSE

The aim of this study is to determine the accuracy of orbital X-rays, when using computed radiography (CR), in detecting ferromagnetic intra-ocular foreign bodies (IOFBs) prior to magnetic resonance imaging (MRI).

METHODS

A total of 64 orbital X-rays of an anthropomorphic head phantom were acquired using CR. For each image 1, 2, 3, or 4, large, medium, or small IOFBs were fixed to the anterior surface of the left or right orbit. Each of the acquired images with an IOFB was duplicated in order to increase the sample size. A further 16 normal images (no IOFB) were also included in the sample. Observers were invited to review the images and were permitted to manually magnify and window the images to detect any IOFBs present on each image.

RESULTS

10 observers (4 radiographers; 4 reporting radiographers; 2 consultant radiologists) independently reviewed the images. The mean (SD) sensitivity and specificity were 72.1% (7.3%) and 99.2% (0.8%) for all observers, respectively. According to size the sensitivity in detecting small, medium and large IOFB were 46%, 76% and 93%, respectively. According to location, the lower lateral quadrants had the lowest sensitivity (53%) whereas the upper medial had the greatest (88%).

CONCLUSION

Findings from this study using CR support previous conclusions that conventional X-rays fail to detect metallic IOFBs in all cases. Diagnostic performance is governed by IOFB size and location.