Echo planar Imaging- Echo Train Length

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Oscar307307
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Echo planar Imaging- Echo Train Length

Post by Oscar307307 » Mon Oct 30, 2017 10:27 pm

In a Echo Planar Imaging sequence, How would you
Calculate the echo train length (ETL) of a sequence using a square matrix size of 64 pixels (64 X64) for an echo spacing(ESP) of 1 ms.
ETL is the number of echos in 1 TR.

Dave Higgins
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Re: Echo planar Imaging- Echo Train Length

Post by Dave Higgins » Tue Oct 31, 2017 9:36 am

63 x 1 ms? (63 spacings in 64 echo readout)

Oscar307307
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Re: Echo planar Imaging- Echo Train Length

Post by Oscar307307 » Tue Oct 31, 2017 10:36 am

Would you then assume that in 128 pixels (128 x128) matrix with echo spacing(ESP) of 1 ms has an ETL of 127 x 1ms=127ms?

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Re: Echo planar Imaging- Echo Train Length

Post by Dave Higgins » Tue Oct 31, 2017 12:23 pm

Assuming no partial Fourier, yes

Oscar307307
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Re: Echo planar Imaging- Echo Train Length

Post by Oscar307307 » Tue Oct 31, 2017 1:31 pm

Firstly Thank you Very much for your help David, I am just starting to learn about MRI this year.
I have another question relation to the previous questions,

What is the (effective) echo time TE for 64square matrix (64 x64) and 128 square martix (128x 128)if you start the ETL immediately after the excitation?
From this; please correct me if I am approaching it incorrectly

TE(Echotime)=ETL X ESP
ESP=1ms
63 X 1ms=63ms?
127 x 1ms=127ms?

Dave Higgins
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Re: Echo planar Imaging- Echo Train Length

Post by Dave Higgins » Tue Oct 31, 2017 2:38 pm

No, the effective echo time for EPI is whenever the central k-space line is acquired.
For a single shot EPI, this would be half way along the echo train.

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