On 7/3/2024 7:19 PM, Hickman, Leonard B. MD wrote:
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Hello all,
I am using FreeSurfer to measure specific cortical parcellations and
subcortical segmentations in a medium-sized dataset (over 150 scans).
About a fifth of the scans include cortical lesions (ischemic stroke,
hemorrhagic stroke, focal traumatic injuries, neoplasm) that visibly
disrupt recon-all's white matter surface and the pial surface locally
at the lesion.
Assuming there is no midline shift, does the recon-all processing
stream perform segmentations and parcellations in each hemisphere
independently? Or, could a unilateral lesion impact
segmentation/parcellation on the contralateral side?
The segmentation is done on each hemi separately. A lesion on one side
should not affect the contralateral side.
For segmentation/parcellation measurements on the side ipsilateral to
a lesion, how robust are recon-all's measurements in non-lesioned
regions? For instance, are hippocampal volume measurements impacted by
a cortical lesion in the frontal convexity? Or a lesion in a lateral
temporal gyrus? Are there any general guides on how close a lesion can
be to a ROI before automated measurements are invalid?
I think a lesion would have to be adjacent to a given structure to
affect its segmentation, at least between cortical lesions and
subcortical structures as your describe. For cortical-cortical, there
could be some effect as the surface placement might be affected. If the
curvature is affected, then it could change the registration to fsaverage.
Thank you much in advance,
Brian
--
L. Brian Hickman, MD, MSc
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