T1 recovery

body of water wave
  • Also known as spin lattice energy transfer
  • It is the time taken to for the spins to dissipate energy so that they regain their longitudinal magnetization
  • It is an exponential process
  • It is tissue specific
  • Defined as time taken for 63% of the longitudinal magnetization to be recovered
  • The time taken for this extends from one RF pulse to the next (i.e., TR)
  • TR determines how much T1 recovery occurs in a tissue
  • T1 recovery is proportional to strength of external magnetic field. Stronger the field, longer the recovery times.
  • Absorbs energy very quickly
  • T1 recovery time is very short
  • 200 ms
  • Very poorly receives energy from spins
  • T1 recovery time is very long
  • 2500 ms
What happens if you control the T1 recovery?
  • A short TR does not permit sufficient recovery of longitudinal magnetization. As a result, when a successive RF pulse is applied, it pushes the NMV beyond the transverse plane. This is called saturation.
  • When saturation occurs, signal from fat and water demonstrate a difference
  • On the contrary, a long TR permits sufficient time for recovery of longitudinal magnetization. As a result, there is no difference between fat and water other than the inherent contrast that is there due to the proton density. Proton density is an intrinsic contrast, and inherent to the tissue being imaged.