The hydrogen T1, T2 and spin density values for common brain tissues are listed in the following table.

 

Tissue T1 (s)  T2 (ms)  ρ* 
CSF 0.8 - 20  110 - 2000  70-230 
White 0.76 - 1.08  61-100  70-90 
Gray 1.09 - 2.15  61 - 109  85 - 125 
Meninges 0.5 - 2.2  50 - 165  5 - 44 
Muscle 0.95 - 1.82  20 - 67  45 - 90 
Adipose 0.2 - 0.75  53 - 94  50 - 100 
*Based on ρ=111 for 12mM aqueous NiCl2

At what TI value is the signal from fat approximately equal to zero in an inversion recovery sequence?

S(TI) = kρ(1 - 2 exp(-TI/T1>)) = 0
TI(s=0) = T1 * ln( 2 )

where:

Given: TI(s=0) = 0.2 s * ln( 2 ) = 0.14 s

TI(s=0) = 0.75 s * ln( 2 ) = 0.52 s

TI(s=0) would vary from 0.14 to 0.52 seconds