Article Figures & Data
Figures
- Fig 1.
Phantom. A cylindrical PMMA phantom (A) with a cylinder containing a clip (B).
- 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).
- 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).
- 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.
- 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).
- Fig 6.
Aspect of a cobalt clip artifact, positioned in the scanplane, at increasing pitch. The numbers of white streaks increase with increasing pitch.
Tables
Ratio KVp* 90 vs 120, High mode 1.3 120 vs 140, High mode 1.2 90 vs 120, Standard mode 1.4 120 vs 140, Standard mode 1.2 Conebeam reconstruction vs linear interpolation* 1.1 Cobalt-containing alloy vs Titanium clip# High mode 1.3 Standard mode 1.5 In plane vs perpendicular‡ 1.4 Note:—CBR indicates conebeam reconstruction.
* for titanium- and cobalt-containing alloy clip.
# for all kVp/mAs combinations.
‡ for both clips in high and standard mode.
Position of Clip to Scan Plane Completely Diagnostic Clinically Useful Not Diagnostic In plane 3 (6.3%) 25 (52%) 20 (42%) (24 clips, 48 evaluations*) Diagonal 6 (15%) 25 (63%) 9 (23%) (20 clips, 40 evaluations) Perpendicular 3 (25%) 8 (67%) 1 (8.3%) (6 clips, 12 evaluations) Total (all positions) 12 (12%) 58 (58%) 30 (30%) (50 clips, 100 evaluations) * A double reading per clip site results in twice as many evaluations as clip sites.
