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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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Example Clip Artifact Volume Reconstructions in Relation to Cortical Surface Models. Basal and mid-sagittal views of each patient's cortical surface model are shown shaded by curvature (top row) and as a point cloud (second row). Superimposed on the point could displays to aide artifact visualization are the reconstructed clip artifact volumes colored according to MR sequence in descending order by clip volume as percentage of brain volume (T2 = green, T1 = yellow, DWI = blue, EPI = red). These artifact volumes are 0.27%, 0.56%, 1.70%, and 4.67% respectively for Patient A (two columns on left), and 0.48%, 1.04%, 3.62%, and 4.74% respectively for Patient B (two columns on right).
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Figure 2: Example Clip Artifact Volume Reconstructions in Relation to Cortical Surface Models. Basal and mid-sagittal views of each patient's cortical surface model are shown shaded by curvature (top row) and as a point cloud (second row). Superimposed on the point could displays to aide artifact visualization are the reconstructed clip artifact volumes colored according to MR sequence in descending order by clip volume as percentage of brain volume (T2 = green, T1 = yellow, DWI = blue, EPI = red). These artifact volumes are 0.27%, 0.56%, 1.70%, and 4.67% respectively for Patient A (two columns on left), and 0.48%, 1.04%, 3.62%, and 4.74% respectively for Patient B (two columns on right).

Mentions: Computed whole-brain volumes were 229,705 and 242,419 mm3 for patient's A and B respectively. These values are in line with an average of whole brain volumes, 235,821 (SD 22,571), computed from a group of similar aged controls (N = 7, 3F, 1LH, 54.0 years, SD 7.8) published recently [49]. To help aide visualization of clip artifact volume in relation to brain size, example artifact volume reconstructions from the range of MR sequences are shown in relation to patient cortical surface models in Figure 2.


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)

Example Clip Artifact Volume Reconstructions in Relation to Cortical Surface Models. Basal and mid-sagittal views of each patient's cortical surface model are shown shaded by curvature (top row) and as a point cloud (second row). Superimposed on the point could displays to aide artifact visualization are the reconstructed clip artifact volumes colored according to MR sequence in descending order by clip volume as percentage of brain volume (T2 = green, T1 = yellow, DWI = blue, EPI = red). These artifact volumes are 0.27%, 0.56%, 1.70%, and 4.67% respectively for Patient A (two columns on left), and 0.48%, 1.04%, 3.62%, and 4.74% respectively for Patient B (two columns on right).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Example Clip Artifact Volume Reconstructions in Relation to Cortical Surface Models. Basal and mid-sagittal views of each patient's cortical surface model are shown shaded by curvature (top row) and as a point cloud (second row). Superimposed on the point could displays to aide artifact visualization are the reconstructed clip artifact volumes colored according to MR sequence in descending order by clip volume as percentage of brain volume (T2 = green, T1 = yellow, DWI = blue, EPI = red). These artifact volumes are 0.27%, 0.56%, 1.70%, and 4.67% respectively for Patient A (two columns on left), and 0.48%, 1.04%, 3.62%, and 4.74% respectively for Patient B (two columns on right).
Mentions: Computed whole-brain volumes were 229,705 and 242,419 mm3 for patient's A and B respectively. These values are in line with an average of whole brain volumes, 235,821 (SD 22,571), computed from a group of similar aged controls (N = 7, 3F, 1LH, 54.0 years, SD 7.8) published recently [49]. To help aide visualization of clip artifact volume in relation to brain size, example artifact volume reconstructions from the range of MR sequences are shown in relation to patient cortical surface models in Figure 2.

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