Are mono-exponential fits to a few echoes sufficient to determine T2 relaxation for in vivo human brain?

Abstract

T2 relaxation decay curves from in vivo human brain tissue are rarely mono-exponential. Partial volume averaging further reduces the chance of mono-exponential decay. Moreover, the parameters derived from few-echo mono- exponential fits change with the measurement echo times and have the largest possible variance. In this note, multi-exponential fits to 32-echo relaxation decay curves from In vivo human brain are used to design simulations (where the truth is known) to demonstrate the pitfalls of few-echo mono-exponential interpretations.