Article Figures & Data
Figures
- Fig 1.
A graphic depiction of the metal artifacts prototype algorithm used for the flat panel detector CT images. An initial volume is reconstructed from the raw data containing metal artifacts. The metallic implant is then segmented, creating a binary volume of the implant, which is forward-projected onto the first reconstruction to identify data corrupted by artifacts. The corrupted data are replaced by a nonlinear interpolation procedure by using the data along the metal region boundaries (depicted in green). A new MAR-corrected volume is reconstructed. The segmented metallic implant is overlaid back onto the dataset for the final reconstruction.
- Fig 2.
A, A phantom aneurysm model constructed of silicone elastomer tubing used to test the MAR algorithm prototype. Platinum coils were deployed in the aneurysm, and a small piece of polyurethane was placed inside a stent deployed across the aneurysm neck to model a clot. B and C, Uncorrected FDCT images acquired of the model constructed with stent, coils, and the simulated clot show streak artifacts created by the metal alloys of the stent and coils. D and E, Corresponding MAR-corrected FDCT images show reduced artifacts.
- Fig 3.
Flat panel detector CT uncorrected (A–D) and corresponding MAR-corrected (E–H) images depicting reduction of streak artifacts caused by coils deployed to treat intracranial aneurysms. The images were independently scored for the amount of metal artifacts and the number of visualized vessel segments within a 3-cm radius surrounding the metal objects.
- Fig 4.
Sample FDCT images of various metallic objects causing streak artifacts and the application of the MAR algorithm. A and E, Onyx embolization of an intracranial AVM. The MAR algorithm was less effective at reducing the artifacts caused by Onyx. B and F, A bullet lodged within the cervical spine. C and G, A vascular clip used to treat an intracranial aneurysm. D and H, Stent-assisted coil embolization of an intracranial aneurysm. This example is similar to the phantom model created to evaluate the MAR algorithm. The stent is completely obscured by the metal artifacts but is visible after the application of the MAR algorithm.
- Fig 5.
Relative frequencies of metal artifacts scores assigned to FDCT scans for areas immediately adjacent to the implanted metal object (A) or 3 cm away from the implanted metal object (B). The median P value for the uncorrected and MAR-corrected image pairs adjacent to the metal object was P = .05, and the median P value for the image pairs 3 cm away was P = .03. The uncorrected and MAR-corrected images were independently evaluated by 7 clinicians on a 3-point scale (n = 59).
- Fig 6.
The mean number of visualized vessel segments within a 30-cm radius of the implanted metal object before and after MAR correction. The images were independently evaluated by 7 clinicians. The error bars represent the standard error of the mean (n = 25).
Tables
Metal Objects No. of Datasets Coils only 19 Clips 10 Stent 3 Onyx 3 Stent and coils 21 Other (bullet, spinal screws, mandibular fixtures) 3 Score Definition 0 No metal artifacts; relevant surrounding anatomy well-visualized 1 Moderate metal artifacts; relevant anatomy visible but affected by artifacts 2 Severe artifacts; relevant anatomy not visible
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