Motivation: Determine the tryptophan (TRP) relaxation rates from human brain 1H downfield spectrum in vivo. Goal(s): To estimate the T1 and T2 of TRP in healthy human brains at 7 T Approach: We determined TRP relaxation times using a spectrally- and slice-selective downfield MRS sequence. Results: The mean T1 and T2 estimates of TRP from in vivo human brain were 74.5±12.5ms (n=6) and 19.3±3.5ms (n=8), respectively. Impact: Reliable in vivo brain TRP relaxation measures in normal subjects could help establish reference values and also aid in utilizing it as a novel non-invasive in vivo biomarker for various aging-related and neuropsychiatric disorders.
Nanga et al. (Tue,) studied this question.