23/01/2021
Physics 7
T1 weighted image (T1WI)
T1WI is a basic RF pulse sequence in magnetic resonance (MR) imaging and depicts differences in signal based upon intrinsic T1 relaxation time of various tissues.
When the RF energy source is turned off, the net magnetization vector realigns with the axis of B0 through the process of T1 recovery, during which the longitudinal magnetization increases in magnitude, or recovers .
Different tissues have different characteristic T1values, which is in large part what allows the differentiation of tissues and disease processes in clinical imaging.
Fat has a short relaxation time (ie. fast recovery)as compared to water because it can more easily transfer its received energy to its surroundings. and what 😳 this mean?
Fat will recover quicker to realign with longitudinal magnetization (Z axis). When a second radiofrequent pulse of 90 degrees is given, both of water and fat will deflect to x-y axis (transevers magnetization)but water will not have fully recovered in the longitudinal plane. After the second pulse, fat will make a larger deflection than water and create more transversal,processed only in the transversal plane.The higher the transversal magnetization of the tissue, the more signal is received and the more intensity signal (white).