Question
Question Posted 04/15/26:
Dear experts,
Some of the ADNI T1 images are reported to use the MP-RAGE sequence, while others report the use of IR-SPGR. I am attempting to retrieve the signal mathematical models for each of these sequences, but it seems like some papers in the literature treat them as the same sequence. Would you please be able to clarify if the same signal equation would be expected for both of them? Thanks in advance.
Dear experts,
Some of the ADNI T1 images are reported to use the MP-RAGE sequence, while others report the use of IR-SPGR. I am attempting to retrieve the signal mathematical models for each of these sequences, but it seems like some papers in the literature treat them as the same sequence. Would you please be able to clarify if the same signal equation would be expected for both of them? Thanks in advance.
Response posted 04/15/26 by ADNI MRI Core:
Thank you for your question to the ADNI MRI Core.
MP-RAGE and IR-SPGR are both spoiled fast gradient echo sequences with inversion recovery. They differ in view order and acquisition timing. Fundamentally the signal models are not going to be exactly the same, however with certain approximations they can be similar. It will depend on the model. I would recommend, as a start, looking at:
1. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096899 for MP-RAGE.
and
2. https://cds.ismrm.org/protected/17MProceedings/PDFfiles/4554.html#:~:text=THEORY&text=where%20M0%20is%20the,time%20between%20successive%20inversion%20pulses.&text=where%20%CF%81%20is%20a%20factor,flip%20angle%20from%20the%20prescribed.&text=where%20TR%20is%20the,in%20the%20calculated%20T1%20maps for IR-SPGR.
It is also possible for you to directly reach out to Dr. John Mugler, the inventor of MP-RAGE, who is still active in the field and would probably help with some of the nuances in the existing signal models.
MP-RAGE and IR-SPGR are both spoiled fast gradient echo sequences with inversion recovery. They differ in view order and acquisition timing. Fundamentally the signal models are not going to be exactly the same, however with certain approximations they can be similar. It will depend on the model. I would recommend, as a start, looking at:
1. https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0096899 for MP-RAGE.
and
2. https://cds.ismrm.org/protected/17MProceedings/PDFfiles/4554.html#:~:text=THEORY&text=where%20M0%20is%20the,time%20between%20successive%20inversion%20pulses.&text=where%20%CF%81%20is%20a%20factor,flip%20angle%20from%20the%20prescribed.&text=where%20TR%20is%20the,in%20the%20calculated%20T1%20maps for IR-SPGR.
It is also possible for you to directly reach out to Dr. John Mugler, the inventor of MP-RAGE, who is still active in the field and would probably help with some of the nuances in the existing signal models.
