How is the time measured for T1 relaxation represented?

The time measured for T1 relaxation is indeed often represented as a percentage of the initial value of the magnetization. This is crucial in understanding how quickly the longitudinal magnetization returns to its equilibrium state after being disturbed by an RF pulse. The rationale behind this representation lies in the fact that T1 relaxation is inherently linked to the rate at which the spins recover, which is typically expressed in terms of their return to the original signal intensity.

Using a percentage allows for easy comparison across different conditions and imaging settings, as it provides a relative measure that can be universally applied. This method highlights the degree of recovery that has occurred within a specific time frame, offering insight into tissue properties and behavior during MRI scans.

In contrast, representing T1 relaxation over a linear time scale could lead to misinterpretations of how these values relate to the physical processes occurring in the tissue. Milliseconds are indeed a common way to measure T1 times in a quantitative sense, but the representation in percentages provides a more clinically relevant context for understanding and assessing recovery dynamics. The notion of a ratio of spins' energy does not directly describe the timing aspect of T1 relaxation, further clarifying the applicability and effectiveness of using percentages in this scenario.