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Question Posted 07/07/20:
What refocusing flip train was used for the dual-echo FSE sequence by GE scanners in the ADNI-1 study? I cannot find the protocol sheet for GE scanners.
Response posted 07/28/20 by Matt Senjem:
I have asked our MR physicist and he said that he believes that in the ADNI-1 GE Axial PD/T2 FSE pulse sequence, refocusing flip angle was defaulted, and not a user input.
You should be able to find it in the DICOM header element (0018,1314). I hope this helps, please let us know if you still have questions.
Response posted 07/28/20 by Gitanjali:
Thank you for your reply.
(0018,1314) has a value of 90 degree. Isn't it too low for FSE?
As per GE's DICOM Conformance statement-(0018,1314) reports Primary excitation pulse spin tip angle with the exception: "Represents spin-echo refocusing pulse tip angle when (0019, 109E) equals FSE, (0018, 0023) equals 2D (2D Fast Spin Echo), AND
(0019, 10B5) (user data 14) equals 1."
I checked the header- (0019, 10B5) equals 0.
Is there any other dicom tag/ document that specifically states the value of the Refocusing pulse tip angle? (Just want to add that I am looking at ADNI-1, 3T data).
Response posted 07/29/20 by Matt Senjem:
Upon further inspection, the value you are searching for may be this one in GE private tag (0021,105b).

(0021, 105b) [Tagging Flip Angle] DS: "180.000000"

Response posted 07/29/20 by Gitanjali:
Thank you for your patience with my query.
I looked at the (0021,105b) in ten 3T GE subjects from ADNI-1 and only one of them has a value of 180 in (0021,105b). The value is set to '0' in all other 3T subjects.
Response posted 08/24/20 by Matt Senjem:

I sent your inquiry to our on-site GE MRI physicist and he did some digging to see if he could find an answer to your question. Below is his reply. This is the most accurate info we have about this.
"I believe that tag (0021,105b) is related to cardiac tagging (SPAMM). I believe in the old days the software that generates the DICOMs did not do any checking to see if the scan had cardiac tagging and just pulled the corresponding values directly from the psd variables (so these DICOM elements were populated with the default tag flip angle regardless of whether the scan was a cardiac tagging scan).

I unfortunately don’t have a simulator or access to a target with that old of software on it so I can’t doublecheck this but based on the source code from the time and your protocol, it looks like this wasn’t using tailored RF and so the refocusing flip angle (on 3T) would most likely have been a constant 125 degrees (for standard 8ch head receive coil – T/R coil would have been 160deg). There are a number of special conditions for this particular setting but I tried my best to sort through all the lines of code and come up with my best guess."

Best regards,
Response posted 08/25/20 by Gitanjali:
Thank you Matt for going through the source code to help me out.
I am replying via this old link as the recent one is broken. I just want to confirm the refoc. flip angle for standard 8ch head receive coil. Is it constant 160 deg throughout the train?
Response posted 08/25/20 by Matt Senjem:
That is my understanding.
Response posted 08/25/20 by Gitanjali:
OK and thank you once again for helping me with the queries.
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