Out of Range Values for HCP ASL pipelines

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Aikam Rai

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Dec 12, 2025, 11:06:44 PM (9 days ago) Dec 12
to HCP-Users, maryki...@gmail.com

Hi,

A colleague and I are working with the HCP-ASL pipeline and we are both getting results with outliers that have voxel values ranging up to 200, and even higher sometimes. 

I have added her on this thread since she got more typical values when she used HCP datasets as opposed to her own. It is odd because she age matched HCP healthy controls to her collect controls, but her cohort had higher values. 

We are wondering if this could be an acquisition difference, since the pipeline set up seems to be successful with HCP data. 

Best,

Aikam

Glasser, Matthew

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Dec 13, 2025, 7:31:10 AM (8 days ago) Dec 13
to hcp-...@humanconnectome.org, maryki...@gmail.com, Thomas Kirk, Michael Chappell (staff)

The HCP ASL Pipeline is designed to work with SMS EPI ASL data.  Adding ASL experts.


Matt.

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Thomas Kirk

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Dec 16, 2025, 5:44:40 AM (5 days ago) Dec 16
to Glasser, Matthew, hcp-...@humanconnectome.org, maryki...@gmail.com, Michael Chappell (staff)
Hi Aikam, 

Could you give us more information please about the ASL acquisition you are using?

The HCP ASL pipeline doesn’t implement any volumetric smoothing for the NIFTI outputs, so it’s likely there will be some individual voxels with very high perfusion values. In the T1w/ASL folder there will be some text files eg perfusion_calib_gm_mean.txt, do these also have very high values?

Thanks, 
tom
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