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Artifact quantification and tractography from 3T MRI after placement of aneurysm clips in subarachnoid hemorrhage patients.

Khursheed F, Rohlffs F, Suzuki S, Kim DH, Ellmore TM - BMC Med Imaging (2011)

Bottom Line: Artifact volume varied by MR sequence for length (p = 0.007) and volume (p < 0.001) ratios: it was smallest for structural images, larger for DW-MRI acquisitions, and largest on fMRI images.Inter-rater reliability was high (r = 0.9626, p < 0.0001), and reconstruction of white matter connectivity characteristics increased with distance from the artifact border.In both patients, reconstructed white matter pathways of the uncinate fasciculus and inferior fronto-occipital fasciculus were clearly visible within 2 mm of the artifact border.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Vivian L. Smith Department of Neurosurgery and Mischer Neuroscience Institute, The University of Texas Medical School at Houston, Houston TX 77030, USA.

ABSTRACT

Background: The application of advanced 3T MRI imaging techniques to study recovery after subarachnoid hemorrhage (SAH) is complicated by the presence of image artifacts produced by implanted aneurysm clips. To characterize the effect of these artifacts on image quality, we sought to: 1) quantify extent of image artifact in SAH patients with implanted aneurysm clips across a range of MR sequences typically used in studies of volumetry, blood oxygen level dependent signal change (BOLD-fMRI), and diffusion-weighted imaging (DW-MRI) and 2) to explore the ability to reconstruct white matter pathways in these patients.

Methods: T1- and T2-weighted structural, BOLD-fMRI, and DW-MRI scans were acquired at 3T in two patients with titanium alloy clips in ACOM and left ACA respectively. Intensity-based planimetric contouring was performed on aligned image volumes to define each artifact. Artifact volumes were quantified by artifact/clip length and artifact/brain volume ratios and analyzed by two-way (scan-by-rater) ANOVAs. Tractography pathways were reconstructed from DW-MRI at varying distances from the artifacts using deterministic methods.

Results: Artifact volume varied by MR sequence for length (p = 0.007) and volume (p < 0.001) ratios: it was smallest for structural images, larger for DW-MRI acquisitions, and largest on fMRI images. Inter-rater reliability was high (r = 0.9626, p < 0.0001), and reconstruction of white matter connectivity characteristics increased with distance from the artifact border. In both patients, reconstructed white matter pathways of the uncinate fasciculus and inferior fronto-occipital fasciculus were clearly visible within 2 mm of the artifact border.

Conclusions: Advanced 3T MR can successfully image brain tissue around implanted titanium aneurysm clips at different spatial ranges depending on sequence type. White matter pathways near clip artifacts can be reconstructed and visualized. These findings provide a reference for designing functional and structural neuroimaging studies of recovery in aSAH patients after clip placement.

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Appearance of Aneurysm Clip Artifact on Different Aligned MRI Sequences. Axial slices taken in the same imaging plane for Patient A are displayed in the axial plane (radiological convention) with the crosshair placed in the center of the clip artifact.
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Figure 1: Appearance of Aneurysm Clip Artifact on Different Aligned MRI Sequences. Axial slices taken in the same imaging plane for Patient A are displayed in the axial plane (radiological convention) with the crosshair placed in the center of the clip artifact.

Mentions: Artifact size differences are easily visualized by comparing an image plane across different MR sequences taken through the center of the artifact (Figure 1). On all sequences in both patients, the maximum length measured along the long axis of the artifact was larger than the actual clip length, ranging from 2.82 times the length of the clip for the T2 structural sequence to 6.5 times the length of the clip for the EPI sequence.


Artifact quantification and tractography from 3T MRI after placement of aneurysm clips in subarachnoid hemorrhage patients.

Khursheed F, Rohlffs F, Suzuki S, Kim DH, Ellmore TM - BMC Med Imaging (2011)

Appearance of Aneurysm Clip Artifact on Different Aligned MRI Sequences. Axial slices taken in the same imaging plane for Patient A are displayed in the axial plane (radiological convention) with the crosshair placed in the center of the clip artifact.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3198881&req=5

Figure 1: Appearance of Aneurysm Clip Artifact on Different Aligned MRI Sequences. Axial slices taken in the same imaging plane for Patient A are displayed in the axial plane (radiological convention) with the crosshair placed in the center of the clip artifact.
Mentions: Artifact size differences are easily visualized by comparing an image plane across different MR sequences taken through the center of the artifact (Figure 1). On all sequences in both patients, the maximum length measured along the long axis of the artifact was larger than the actual clip length, ranging from 2.82 times the length of the clip for the T2 structural sequence to 6.5 times the length of the clip for the EPI sequence.

Bottom Line: Artifact volume varied by MR sequence for length (p = 0.007) and volume (p < 0.001) ratios: it was smallest for structural images, larger for DW-MRI acquisitions, and largest on fMRI images.Inter-rater reliability was high (r = 0.9626, p < 0.0001), and reconstruction of white matter connectivity characteristics increased with distance from the artifact border.In both patients, reconstructed white matter pathways of the uncinate fasciculus and inferior fronto-occipital fasciculus were clearly visible within 2 mm of the artifact border.

View Article: PubMed Central - HTML - PubMed

Affiliation: The Vivian L. Smith Department of Neurosurgery and Mischer Neuroscience Institute, The University of Texas Medical School at Houston, Houston TX 77030, USA.

ABSTRACT

Background: The application of advanced 3T MRI imaging techniques to study recovery after subarachnoid hemorrhage (SAH) is complicated by the presence of image artifacts produced by implanted aneurysm clips. To characterize the effect of these artifacts on image quality, we sought to: 1) quantify extent of image artifact in SAH patients with implanted aneurysm clips across a range of MR sequences typically used in studies of volumetry, blood oxygen level dependent signal change (BOLD-fMRI), and diffusion-weighted imaging (DW-MRI) and 2) to explore the ability to reconstruct white matter pathways in these patients.

Methods: T1- and T2-weighted structural, BOLD-fMRI, and DW-MRI scans were acquired at 3T in two patients with titanium alloy clips in ACOM and left ACA respectively. Intensity-based planimetric contouring was performed on aligned image volumes to define each artifact. Artifact volumes were quantified by artifact/clip length and artifact/brain volume ratios and analyzed by two-way (scan-by-rater) ANOVAs. Tractography pathways were reconstructed from DW-MRI at varying distances from the artifacts using deterministic methods.

Results: Artifact volume varied by MR sequence for length (p = 0.007) and volume (p < 0.001) ratios: it was smallest for structural images, larger for DW-MRI acquisitions, and largest on fMRI images. Inter-rater reliability was high (r = 0.9626, p < 0.0001), and reconstruction of white matter connectivity characteristics increased with distance from the artifact border. In both patients, reconstructed white matter pathways of the uncinate fasciculus and inferior fronto-occipital fasciculus were clearly visible within 2 mm of the artifact border.

Conclusions: Advanced 3T MR can successfully image brain tissue around implanted titanium aneurysm clips at different spatial ranges depending on sequence type. White matter pathways near clip artifacts can be reconstructed and visualized. These findings provide a reference for designing functional and structural neuroimaging studies of recovery in aSAH patients after clip placement.

Show MeSH
Related in: MedlinePlus