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Keirnan Willett, Mike Sheng, John Woo, Thomasine Gorry; Computed tomography imaging of periocular metallic foreign bodies can be improved by artifact reduction software. Invest. Ophthalmol. Vis. Sci. 2017;58(8):664.
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© ARVO (1962-2015); The Authors (2016-present)
Computed tomography (CT) is the standard of care for assessment of ocular and orbital trauma. In cases of retained metallic foreign bodies, streak artifacts can significantly degrade CT image quality. Methods have been used to reduce metallic streak artifacts elsewhere in the body but their utility in the eye and orbit has not yet been reported.
Ten cases of retained periocular metallic foreign bodies (FB) evaluated by CT scan were identified retrospectively from a large urban trauma center. Post-acquisition images were processed with a metal streak artifact reduction software (MAR) called metal deletion technology. The change in the severity of the metal streak artifact was assessed objectively by 1) the size of the artifact and 2) the standard deviation of pixel intensities along a path surrounding the foreign body. For subjective assessment, radiologists (4), ophthalmologists (4) and oculoplastic specialists (3) used a Likert scale to grade images on 6 clinically relevant criteria.
Average grading of “severity of metal streak artifact” and overall “confidence in prognosis” was improved after MAR in all ten cases (p<0.001). The standard deviation of pixel intensity for a path surrounding the FB was decreased in all cases (p<0.001) and area of streak artifact was reduced in all cases (p<0.001). The improvement in the confidence of assessment for specific criteria and structures was variable for individual cases, including – identification of all FB, assessment extra ocular muscles, assessment of optic nerve, assessment for globe rupture and assessment for orbital fracture.
Metal artifact reduction algorithms in computed tomography have potential benefits in improving diagnostic accuracy and confidence in emergent periocular trauma cases.
This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.
Example of CT streak artifact from metallic foreign body before (left) and after (right) metal artifact reduction (MAR). The area of the artifact was reduced after MAR in all ten cases studied (plot) (p<0.001).
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