Portal de Periódicos da CAPES

Non‐invasive evaluation of blood oxygen saturation and hematocrit from T 1 and T 2 relaxation times: In‐vitro validation in fetal blood

2017; Wiley; Volume: 78; Issue: 6 Linguagem: Inglês

10.1002/mrm.26599

1522-2594

Sharon Portnoy, Mike Seed, John G. Sled, Christopher K. Macgowan,

MRI in cancer diagnosis

Purpose We propose an analytical method for calculating blood hematocrit ( Hct ) and oxygen saturation ( sO 2 ) from measurements of its T 1 and T 2 relaxation times. Theory Through algebraic substitution, established two‐compartment relationships describing and as a function of hematocrit and oxygen saturation were rearranged to solve for Hct and sO 2 in terms of R 1 and R 2 . Resulting solutions for Hct and sO 2 are the roots of cubic polynomials. Methods Feasibility of the method was established by comparison of Hct and sO 2 estimates obtained from relaxometry measurements (at 1.5 Tesla) in cord blood specimens to ground‐truth values obtained by blood gas analysis. Monte Carlo simulations were also conducted to assess the effect of T 1 , T 2 measurement uncertainty on precision of Hct and sO 2 estimates. Results Good agreement was observed between estimated and ground‐truth blood properties (bias = 0.01; 95% limits of agreement = ±0.13 for Hct and sO 2 ). Considering the combined effects of biological variability and random measurement noise, we estimate a typical uncertainty of ±0.1 for Hct, sO 2 estimates. Conclusion Results demonstrate accurate quantification of Hct and sO 2 from T 1 and T 2 . This method is applicable to noninvasive fetal vessel oximetry—an application where existing oximetry devices are unusable or require risky blood‐sampling procedures. Magn Reson Med 78:2352–2359, 2017. © 2017 International Society for Magnetic Resonance in Medicine.