Artifact reduction of different metallic implants in flat detector C-arm CT.
OBJECTIVE
Flat detector CT has been increasingly used as a follow-up examination after endovascular intervention. Metal artifact reduction has been successfully demonstrated in coil mass cases, but only in a small series. We attempted to objectively and subjectively evaluate the feasibility of metal artifact reduction with various metallic objects and coil lengths.


METHODS
We retrospectively reprocessed the flat detector CT data of 28 patients (15 men, 13 women; mean age, 55.6 years) after they underwent endovascular treatment (20 coiling ± stent placement, 6 liquid embolizers) or shunt drainage (n = 2) between January 2009 and November 2011 by using a metal artifact reduction correction algorithm. We measured CT value ranges and noise by using region-of-interest methods, and 2 experienced neuroradiologists rated the degrees of improved imaging quality and artifact reduction by comparing uncorrected and corrected images.


RESULTS
After we applied the metal artifact reduction algorithm, the CT value ranges and the noise were substantially reduced (1815.3 ± 793.7 versus 231.7 ± 95.9 and 319.9 ± 136.6 versus 45.9 ± 14.0; both P < .001) regardless of the types of metallic objects and various sizes of coil masses. The rater study achieved an overall improvement of imaging quality and artifact reduction (85.7% and 78.6% of cases by 2 raters, respectively), with the greatest improvement in the coiling group, moderate improvement in the liquid embolizers, and the smallest improvement in ventricular shunting (overall agreement, 0.857).


CONCLUSIONS
The metal artifact reduction algorithm substantially reduced artifacts and improved the objective image quality in every studied case. It also allowed improved diagnostic confidence in most cases.
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanDepartment of Biomedical Imaging and Radiological Sciences (S.-C.H.)School of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan.
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SC
Hung
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan.
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Wu
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan.
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Lin
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan. wyguo@vghtpe.gov.tw.
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WY
Guo
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan.
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Luo
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan.
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Chang
From the Department of Radiology (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), Taipei Veterans General Hospital, Taipei, TaiwanSchool of Medicine (S.-C.H., C.-C.W., C.-J.L., W.-Y.G., C.-B.L., F.-C.C., C.-Y.C.), National Yang-Ming University, Taipei, Taiwan.
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Chang
D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000465:Algorithms; D016477:Artifacts; D002533:Cerebral Angiography / Q000379:methods*; D005240:Feasibility Studies; D005260:Female; D006801:Humans; D008297:Male; D008670:Metals; D008875:Middle Aged; D019736:Prostheses and Implants; D011856:Radiographic Image Enhancement / Q000379:methods*; D015641:Radiography, Interventional / Q000379:methods*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014057:Tomography, X-Ray Computed / Q000295:instrumentation / Q000379:methods*; D014963:X-Ray Intensifying Screens; D055815:Young Adult
D008670:Metals