Simulation and Measurement of Fetal Blood Oxygen Saturation based on T2 Values at 3T MRI

Abstract

Objective: Recent studies have proven a dependency between MRI relaxation times (T2 , T2) and blood oxygen saturation levels (sO2) applying blood oxygenation level dependent (BOLD) sequences [24, 27, 49]. With this approach, the present work focuses on measuring the T2 dependency on fetal sO2 at 3T MRI in-vitro and quantifying its relationship. Thereafter this quanti cation would be applied to in-vivo fetal imaging to develop a non-invasive method that measures sO2 based on signal intensities. Method: T2 measurements were performed on a 3T MRI scanner using a T2 preparation pulse and a balanced- SSFP sequence. Calibration experiments where made using MnCl2 phantoms and hole blood samples retrieved from the umbilical cord. Signal intensities where tted by a monoexponential equation to calculate T2 values, and a quadratic model was applied to determine the oxygen dependency. Afterwards, signal intensities in the fetal left ventricle where obtained in-vivo and correlated with the in-vitro calibration. Results: The resulting quantitative correlation equation used for calculating fetal oxygenation in-vivo is R2 = 0:0041+0:058(1