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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?
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?
Thank you much in advance, Brian -- L. Brian Hickman, MD, MSc
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On 7/3/2024 7:19 PM, Hickman, Leonard B. MD wrote:
External Email - Use Caution
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
UCLA HEALTH SCIENCES IMPORTANT WARNING: This email (and any attachments) is only intended for the use of the person or entity to which it is addressed, and may contain information that is privileged and confidential. You, the recipient, are obligated to maintain it in a safe, secure and confidential manner. Unauthorized redisclosure or failure to maintain confidentiality may subject you to federal and state penalties. If you are not the intended recipient, please immediately notify us by return email, and delete this message from your computer.
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Hickman, Leonard B. MD