T2‐prepared balanced steady‐state free precession (bSSFP) for quantifying whole‐blood oxygen saturation at 1.5T

Purpose To establish a calibration equation to convert human blood T 2 to the full range of oxygen saturation levels ( HbO 2 ) and physiologic hematocrit (Hct ) values using a T 2 ‐prepared balanced steady‐state free precession sequence (T 2 ‐SSFP) at 1.5T. Methods Blood drawn from 10 healthy donors (29.1 ± 3.9 years old) was prepared into samples of varying HbO 2 and Hct (n = 79), and imaged using T 2 ‐SSFP sequence at 37°C and interrefocusing interval τ 180 = 12 ms. The relationship between blood T 2 , HbO 2 , and Hct was established based on the model . Measured R 2 and HbO 2 levels were fit by the model yielding values of , , and k . T 2 ‐SSFP and the established calibration equation were applied to extract HbO 2 at the superior sagittal sinus (SSS) in vivo and were compared with susceptometry‐based oximetry. Results Constants derived from the fit were: k = 74.2 s −1 , = 1.5 s −1 , = 11.6 s −1 , the R 2 of the fit was 0.95. Average HbO 2 at the SSS in seven healthy volunteers was 65% ± 7% and 66% ± 7% via T 2 ‐ and susceptometry‐based oximetry, respectively. Bland‐Altman analysis indicated agreement between the two oximetric methods with no significant bias. Conclusion The calibration constants presented here should ensure improved accuracy for whole‐blood oximetry based on T 2 ‐SSFP at 1.5T. Magn Reson Med 79:1893–1900, 2018. © 2017 International Society for Magnetic Resonance in Medicine.