Re: T2* computation...

Posted by Fred Damen on Feb 05, 2020; 1:26am
URL: http://imagej.273.s1.nabble.com/T2-computation-tp5022909p5022918.html

Greetings Gonzalo,

If you tell me what you are conceptually trying to accomplish, I could
better guide you.

Technically, all MR images are T2* weighted, as R2* (1/T2*) is the
observed rate at which the MR signal attenuates due to the spins
dephasing. Using a spin-echo sequence, the spins dephased by deltaB0 are
rephased during image acquisition window and thus eliminates the T2'
information from the image; thus making spin-echo the acquisition method
of choice for T2 mapping.  If using a gradient echo sequence is a
requirement, then I assume that you can acquire enough images with
properly spaced TE(s) such that you can do a bi-exponential fit to extract
both T2 and T2'.  Although note, that deltaB0 causes blurring/displacement
in addition to signal attenuation.

Enjoy,

Fred

On Mon, February 3, 2020 2:53 pm, Gonzalo Rojas Costa wrote:

> Hi Fred:
>
> For T2* mapping I mean T2 mapping for gradient echo sequence...
>
> Sincerely,
>
>
> Gonzalo Rojas Costa
>
>
> El lun., 3 de febrero de 2020 21:06, Fred Damen <[hidden email]>
> escribió:
>
>> Greetings,
>>
>> It depends on what exactly what you mean by T2* mapping?
>>
>> If you are referring to determining the time constant then the same post
>> processing plugin will work.  1/T2* = 1/T2 + 1/T2'; A spin echo pulse
>> sequence eliminates, i.e, reduces to negligible level, the T2' component
>> leaving just the T2 component.  A gradient echo sequence includes the
>> T2'
>> component.
>>
>> If you are referring to creating deltaB0 map, then you need to do a
>> linear
>> fit to the phase image, albeit with special handling of the phase wrap.
>> I
>> have a plugin for this. (I have not yet dressed the code up for release
>> though)
>>
>> If you are referring to Susceptibility Weighted Imaging, I do not know
>> of
>> a ImageJ plugin, albeit there are other tools out there.
>>
>> Enjoy,
>>
>> Fred
>>
>> On Mon, February 3, 2020 12:44 pm, Gonzalo Rojas Costa wrote:
>> > Hi:
>> >
>> >   Which plugin computes T2* mapping ?.. Because "MRI Analysis
>> Calculator
>> > v1.0" only computes T2 mapping...
>> >
>> >   Sincerely,
>> >
>> >
>> > Gonzalo Rojas Costa
>> > Chair LABMAN (OHBM)
>> >
>> > Laboratory for Advanced Medical Image Processing
>> > Department of Radiology
>> > Health Innovation Center
>> > Clínica las Condes
>> > Lo Fontecilla 441, Las Condes, Santiago, Chile.
>> > Tel: [phone]
>> > Cel: 56-9-97771785
>> > http://www.aribrain.info
>> > https://scholar.google.com/citations?user=LO7LZ3oAAAAJ
>> > https://www.researchgate.net/profile/Gonzalo_Rojas2
>> > http://www.researcherid.com/rid/B-2036-2013
>> > https://cl.linkedin.com/in/gonzalorojascosta
>> >
>> > --
>> > ImageJ mailing list: http://imagej.nih.gov/ij/list.html
>> >
>>
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