Purpose
To establish a calibration equation to convert human blood T2 to the full range of oxygen saturation levels (HbO2) and physiologic hematocrit (Hct) values using a T2‐prepared balanced steady‐state free precession sequence (T2‐SSFP) at 1.5T.
Methods
Blood drawn from 10 healthy donors (29.1 ± 3.9 years old) was prepared into samples of varying HbO2 and Hct (n = 79), and imaged using T2‐SSFP sequence at 37°C and interrefocusing interval τ180 = 12 ms. The relationship between blood T2, HbO2, and Hct was established based on the model
. Measured R2 and HbO2 levels were fit by the model yielding values of
,
, and k. T2‐SSFP and the established calibration equation were applied to extract HbO2 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 R2 of the fit was 0.95. Average HbO2 at the SSS in seven healthy volunteers was 65% ± 7% and 66% ± 7% via T2‐ 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 T2‐SSFP at 1.5T. Magn Reson Med 79:1893–1900, 2018. © 2017 International Society for Magnetic Resonance in Medicine.