Description

The T2 times for tissue and blood are automatically defined by ExploreASL but Amnah suggested that we use these instead:

t2 = 0.085 s
t2b = 0.165 s

Ref: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3554863/?report=reader#!po=42.5000 (Table 1) --> reference 30 of this paper – which is an ISMRM abstract [https://cds.ismrm.org/ismrm-2003/0131.pd]) – says T2b for 1.5T = 240ms, T2b at 3T = 165ms -> however these values are at 100% O2 level...)

T2 of blood:
https://onlinelibrary.wiley.com/doi/pdf/10.1002/mrm.21342, this paper's Table 1 says that the T2 of blood changes a lot with Hct:
Hct = 0.21, T2bl = 175 ms
Hct = 0.44, T2bl = 112 ms
Hct = 0.57, T2bl = 92 ms

--> We really need to have subject-specific Hct and a T2 mapto get sub-specific values of T2 in GM and WM

T2 of tissue:
https://onlinelibrary.wiley.com/doi/10.1002/jmri.20356 says:
-> at 3T, T2 of GM = 88 ms and T2 of WM = 69 ms;
-> at 1.5 T, T2 of GM = 99 ms and T2 of WM = 79 ms;

T2 of tissue and blood:
Other paper says very different values.. Stanisz GJ, Odrobina EE, Pun J et al. T1, T2 relaxation and magnetization transfer in tissue at 3T. Magn Reson Med 2005; 54:507-512.

My conclusion:
Since we know that T2 of tissue is between 80-90, I htink using 0.085 as Amnah does is reasonable

Tasks

• Change the default values of T2art and T2star
• Provide a reference for T2=85ms
• Try to find the values to 1.5 and 7T
• Check if it works

(I'm not sure where neither x.Q.T2art nor x.Q.T2 values come from, though - see below)

How to test

Test quantification with Fabber with these values. I've done it and it works.

Release notes

T2 timings of blood and tissue have been updated