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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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Related in: MedlinePlus

White Matter Tractography Reconstruction Ability Increases as a Function of Distance from Artifact Border. The artifact masks derived from the diffusion-weighted image volume were dilated in 2 mm increments, and the volume of white matter tracts that intersected any component of the dilated mask was computed. Components of the uncinate fasciculus (loop from temporal to ventral frontal) and inferior fronto-occipital fasciculus (occipital to temporal) in both patients' left hemisphere can be resolved within 2 mm of the artifact border by visual inspection of the orange tractography pathways. Both views are sagittal left hemisphere where A, P, S, and I indicate anterior, posterior, superior and inferior directions.
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Figure 3: White Matter Tractography Reconstruction Ability Increases as a Function of Distance from Artifact Border. The artifact masks derived from the diffusion-weighted image volume were dilated in 2 mm increments, and the volume of white matter tracts that intersected any component of the dilated mask was computed. Components of the uncinate fasciculus (loop from temporal to ventral frontal) and inferior fronto-occipital fasciculus (occipital to temporal) in both patients' left hemisphere can be resolved within 2 mm of the artifact border by visual inspection of the orange tractography pathways. Both views are sagittal left hemisphere where A, P, S, and I indicate anterior, posterior, superior and inferior directions.

Mentions: The ability to reconstruct nearby white matter fiber pathways as a function of distance from the artifact border was examined in both patients. The artifact mask delineated on the diffusion-weighted sequence was expanded by 3D morphological dilation incrementally in 2 mm steps (Figure 3) and the volume of the white matter tracts intersecting the dilated mask was found to increase markedly from the border, from 592 micro liters within 2 mm of the artifact border to 2752 micro liters within 6 mm of the border for Patient A with the 7 mm clip, and from 1348 to 4556 in Patient B with the larger 11 mm clip. After just one increment of dilation, pathways of the uncinate fasciculus (connecting anterior temporal and ventral frontal lobe) and pathways of the inferior fronto-occipital fasciculus, connecting parieto-occipital and ventral frontal lobe [57-59], were visible in the data of both patients (Figure 3).


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)

White Matter Tractography Reconstruction Ability Increases as a Function of Distance from Artifact Border. The artifact masks derived from the diffusion-weighted image volume were dilated in 2 mm increments, and the volume of white matter tracts that intersected any component of the dilated mask was computed. Components of the uncinate fasciculus (loop from temporal to ventral frontal) and inferior fronto-occipital fasciculus (occipital to temporal) in both patients' left hemisphere can be resolved within 2 mm of the artifact border by visual inspection of the orange tractography pathways. Both views are sagittal left hemisphere where A, P, S, and I indicate anterior, posterior, superior and inferior directions.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: White Matter Tractography Reconstruction Ability Increases as a Function of Distance from Artifact Border. The artifact masks derived from the diffusion-weighted image volume were dilated in 2 mm increments, and the volume of white matter tracts that intersected any component of the dilated mask was computed. Components of the uncinate fasciculus (loop from temporal to ventral frontal) and inferior fronto-occipital fasciculus (occipital to temporal) in both patients' left hemisphere can be resolved within 2 mm of the artifact border by visual inspection of the orange tractography pathways. Both views are sagittal left hemisphere where A, P, S, and I indicate anterior, posterior, superior and inferior directions.
Mentions: The ability to reconstruct nearby white matter fiber pathways as a function of distance from the artifact border was examined in both patients. The artifact mask delineated on the diffusion-weighted sequence was expanded by 3D morphological dilation incrementally in 2 mm steps (Figure 3) and the volume of the white matter tracts intersecting the dilated mask was found to increase markedly from the border, from 592 micro liters within 2 mm of the artifact border to 2752 micro liters within 6 mm of the border for Patient A with the 7 mm clip, and from 1348 to 4556 in Patient B with the larger 11 mm clip. After just one increment of dilation, pathways of the uncinate fasciculus (connecting anterior temporal and ventral frontal lobe) and pathways of the inferior fronto-occipital fasciculus, connecting parieto-occipital and ventral frontal lobe [57-59], were visible in the data of both patients (Figure 3).

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