A general model to calculate the spin-lattice (T1) relaxation time of blood, accounting for haematocrit, oxygen saturation and magnetic field strength

Many MRI techniques require prior knowledge of the T1-relaxation time of blood (T-1bl). An assumed/fixed value is often used; however, T-1bl is sensitive to magnetic field (B-0), haematocrit (Hct), and oxygen saturation (Y). We aimed to combine data from previous in vitro measurements into a mathematical model, to estimate T-1bl as a function of B-0, Hct, and Y. The model was shown to predict T-1bl from in vivo studies with a good accuracy (+/- 87 ms). This model allows for improved estimation of T-1bl between 1.5-7.0 T while accounting for variations in Hct and Y, leading to improved accuracy of MRI-derived perfusion measurements.