different among mprage, mprage sense, accelerated mprage, mprage grappa

[Ehsan Karimi]

Hello

I have problem with description of images in image selection stage from baseline mprage images. Does anyone know the difference among images which have the following descriptions?
mprage, 

mprage sense and sense2

accelerated mprage, 

mprage grappa,

 adni mprage,

irfspgr

(see attached file)

[Danielle J Harvey]

Hello,

 

Over the different phases of ADNI, we have had different protocols. MPRAGE and IRSPGR (or IRFSPGR) are descriptions for the same type of scan, but from different vendors of the MRI (for example,  GE scanners have IRSPGR or IRFSPGR). SENSE/SENSE2/GRAPPA/Accelerated all refer to an accelerated acquisition (in ADNI-GO/2, the protocol consisted of both a non-accelerated and an accelerated acquisition) – in ADNI-1, all scans were non-accelerated scans, and in ADNI-3, all scans should be an accelerated acquisition. Other differences across phases of ADNI that you should be aware of include ADNI-1 scans were 1.5T scans for everyone, with a subset also getting 3T scans, while from ADNI-GO on, acquisitions were at 3T (though carry-over participants may have continued at 1.5T)…so field strength is something you will want to pay attention to.

 

Danielle

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[Anita Sinha]

It was mentioned that " MPRAGE and IRSPGR (or IRFSPGR) are descriptions for the same type of scan, but from different vendors of the MRI". Is it reasonable to combine data for subjects with both types of T1 image acquisitions or has scanner variability shown to be a confounding factor with this data? I ask because once we look for subjects with multiple time points >2), the sample size gets considerably smaller if we only choose subjects with MPRAGE or IRSPGR.

Could you clarify this?

[Danielle J Harvey]

I am not aware of issues combining the MPRAGE and IRSPGR/IRFSPGR. The ADNI MRI Core came up with a protocol that was as harmonized as possible across vendors. I have not seen analyses restricted to one type or the other…

 

Danielle

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[Anita Sinha]

Danielle,

Thank you for the clarification. I have noticed that for the rs-fMRI data (which was downloaded as nifi files), some subjects have 197 files(volumes), whereas others have 750-970. Is there a standard way of obtaining the 4d timeseries for each subject? I'm not sure if I can combine subjects with different numbers of volumes for analysis or if this is related to the vendor used.

Could you clarify this?

Thank you.

Anita

[Danielle J Harvey]

Hi Anita,

 

While I am less familiar with the rs-fMRI than the structural MRI, I do know that in ADNI-3, we are using a basic and an advanced protocol, depending on the scanners at the different sites…if sites are able to run the advanced protocol with their scanner, they are, but if the scanners aren’t capable of that protocol, there is a basic protocol that can be used. From information that the MRI Core has posted, the basic protocol in ADNI-3 should be compatible with the rs-fMRI obtained in ADNI-2, but the advanced protocol images would not be. The following shows the different protocols (JG_ADNI3_AAIC_poster_FINAL.pptx (usc.edu) ). I’m not sure if the basic vs advanced protocol is accounting for the differences, but that seems like a good possibility…

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[Anita Sinha]

Danielle,

With respect to ADNI3 data, is there an easy way to identify which subjects were scanned using the basic vs advanced protocol? Or is it reasonable to combine all subjects together? Or could you refer me to someone that I can chat with regarding combining rs-fMRI data acquired using different sequences?

-Anita

[Danielle J Harvey]

Hi Anita,

 

One option is to ask a question through the Ask the Experts tool and direct the question to the MRI Core (ADNI |  Ask the Experts (usc.edu)). They should be able to help with the identification of the basic vs advanced protocols. They might even be able to provide some  insight into whether or not it is appropriate to combine across them (I suspect that it isn’t, but they’ve been looking at the images more closely than I have!).

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[Anita Sinha]

Danielle,

Yes, I've tried to post a few questions using "Ask the experts", but had not received any response, so I moved to this forum to get some clarification. Just to make sure I'm understanding correctly, with identical scanner protocols, it would be reasonable to combine subject data with different T1 sequences (MPRAGE and  IRSPGR/IRFSPGR)? In the literature, it seems as though most people end up reporting a small N because they only used subject data that had T1 data acquired using the MPRAGE sequence, but it's not clear.

-Anita

[Danielle J Harvey]

Hi Anita,

 

Okay, let me see what I can find out for you regarding the fMRI protocols. As I mentioned, I have not seen the labs processing the T1 sequences making a distinction between the MPRAGE or IRSPGR sequences. I have seen FreeSurfer analyses, for example, that have used all available data (from the same field strength).

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[Anita Sinha]

Danielle,

That would be extremely helpful! Given that a large sample size will help with statistical power, if it's reasonable to combine fMRI dat acquired using different sequences (that should be identical) from different vendors, that would be ideal. Please let me know what you find.

Thank you for your continued help.