Minimizing Clip Artifacts in Multi CT Angiography of Clipped Patients
I. van der Schaafa,
M. van Leeuwena,
A. Vlassenbroekb and
B. Velthuisa
a Department of Radiology, University Medical Center Utrecht, Best, the Netherlands
b Philips Medical Systems, Best, the Netherlands
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Fig 1. Phantom. A cylindrical PMMA phantom (A) with a cylinder containing a clip (B).
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Fig 2. Metal artifact of Cobalt clips scanned at pitch 1 positioned in the scanplance (A–C) and perpendicular to the scan plane (D). The metal artifact consists of a black-and-white component. The aspect of the artifact changes with decreasing window width: widest width (A); window width as used in clinical practice (B); and binary picture (C). The artifact volume largely depends on the position of the clip to the scan plane, with much less artifact for a clip perpendicular to the scan plane (D) compared to a clip in the scan plane (B).
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Fig 3. Artifact quantification in patients: quantification of the black-and-white component of the artifact in patients in CTA source images.
A, Clip artifact in clinical window setting, with background of 32 HU and an SD of 21.
B, Area of the black component of the artifact enclosing all pixels with HU < 31 (±3 SD).
C, Area of the white component of the artifact enclosing all pixels with HU > 95 (±3 SD).
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Fig 4. Artifact volume of the Cobalt containing alloly and titanium clip at increasing pitch. Volume of clip artifact at increasing pitch for cobalt-containing alloy (upper, black lines) and titanium (lower, white lines) clip. Both clips were scanned in the high mode (superscript H, open symbols) up to pitch 1, and standard mode (superscript S, closed symbols) up to pitch 1.5 at 90 (triangles), 120 (squares), and 140 (circles) kVp.
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Fig 5. Number of white streaks for the cobalt-containing alloy (upper, black lines) and titanium clips (lower, white lines) scanned in high mode (H) (open symbols, up to P 1) and standard mode (S) (closed symbols, up to P 1.5).
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Fig 6. Aspect of a cobalt clip artifact, positioned in the scanplane, at increasing pitch. The numbers of white streaks increase with increasing pitch.
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AJNR - American Journal of Neuroradiology