Questions about HCP-Aging PCASL acquisition parameters

[Yen-Wen Chen]

Dear experts, 

I am working on the HCP-Aging (2.0 Release) unprocessed images and I am trying to convert the data into BIDS (v1.6.0) format. 

I have some questions about the PCASL data as some required information for BIDS is not available in the corresponding json file ('HCA7467588_V1_MR_mbPCASLhr_PA' from 'imagingcollection01'). 

(1) Is 'ArterialSpinLebelingType' 'PCASL'?

(2) the 'PostLabelingDelay': from the imaging protocol ('HCP_VE11C_CMRRmb_CMRRmbPCASL_MartinosT1T2vNav_2019.01.14', which I downloaded from the Study protocol), the Postlabeling delay is "1641860 us" (= 1.641860 seconds). However, from Harms et al. (2018) Extending the HCP across ages, multiple post-labeling delays (5 PLDs: 0.2, 0.7, 1.2, 1.7, 2.2 s) were used. Which value (or array of values, if multiple PLDs) should I include in BIDS json file?

(3) 'BackgroundSuppression': no background suppression was implemented, correct?

(4) 'M0Type': the protocol (CMRR MB-EPI PCASL) suggests that "two M0 images after label/control image series were acquired, and the mean image can be used for CBF quantification". My question is that are these two M0 images contained within the '*_mbPCASLhr_PA.nii.gz'? 

(5) 'TotalAcquiredPairs': are there 45 pairs of label/control images? (the Measurements from the protocol is 90)

(6) 'LaeblingDuration': from the protocol, it is 1.5 seconds?

Any inputs would be very helpful. Thank you so much.

Best, 

Samantha

 

[Harms, Michael]

 

Hi,

We can’t really speak to how to translate the PCASL sequences into BIDS, as I don’t know the BIDS specification for ASL (e.g., how it handles the case of multiple post-label delays).

 

The protocol acquired 12, 12, 12, 20, and 30 volumes at post-labeling delays of 0.2, 0.7, 1.2, 1.7, and 2.2 sec, respectively.  Label duration of 1.5 sec.  No background suppression.

 

There are 43 label/control pairs (86 frames), followed by 2 noise images and 2 M0 images (I don’t recall the order, but it is obvious from the data).  Thus 90 frames in total.

 

Cheers,

-MH

 

-- 

Michael Harms, Ph.D.

-----------------------------------------------------------

Associate Professor of Psychiatry

Washington University School of Medicine

Department of Psychiatry, Box 8134

660 South Euclid Ave.                        Tel: 314-747-6173

St. Louis, MO  63110                          Email: mha...@wustl.edu

 

From: Yen-Wen Chen <yen-we...@stonybrook.edu>
Reply-To: "hcp-...@humanconnectome.org" <hcp-...@humanconnectome.org>
Date: Thursday, October 7, 2021 at 1:00 PM
To: HCP-Users <hcp-...@humanconnectome.org>
Subject: [hcp-users] Questions about HCP-Aging PCASL acquisition parameters

 

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[Yen-Wen Chen]

Hello Michael, 

Thank you for the response and clarification. Those information is really what I need for the moment!

Thank you.

Best, 
Sam.