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MRI quantification of human fetal O 2 delivery rate in the second and third trimesters of pregnancy
Author(s) -
RodríguezSoto Ana E.,
Langham Michael C.,
Abdulmalik Osheiza,
Englund Erin K.,
Schwartz Nadav,
Wehrli Felix W.
Publication year - 2018
Publication title -
magnetic resonance in medicine
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.696
H-Index - 225
eISSN - 1522-2594
pISSN - 0740-3194
DOI - 10.1002/mrm.27094
Subject(s) - hematocrit , fetus , gestational age , umbilical cord , medicine , umbilical vein , gestation , pregnancy , oxygen saturation , blood flow , nuclear medicine , anesthesia , chemistry , oxygen , anatomy , biology , in vitro , biochemistry , organic chemistry , genetics
Purpose The purpose of this study was to estimate fetal O 2 delivery rate in vivo across a range of gestational ages. Toward this, a calibration equation for T 2 ‐based oximetry was derived. Methods Umbilical cord blood of varying hematocrit (Hct) and oxygen saturation (HbO 2 ) levels was prepared and T 2 measured using a T 2 ‐prepared balanced steady‐state free‐precession sequence at 1.5 T. The relationship between blood R 2 = 1/T 2 , HbO 2 and Hct was established based on the modelR 2 = ( 1 − Hct ) R 2 , plasma + Hct R 2 , RBC + k · Hct · ( 1 − Hct ) ·( 1 − HbO 2 ) 2 . Experimental R 2 , HbO 2 , and Hct levels were fit to the model‐yielding values of k,R 2 , plasma , andR 2 , RBC(R 2 of plasma and erythrocytes). Umbilical vein T 2 measured in vivo was then converted to HbO 2 , yielding—together with blood flow rate—the fetal O 2 delivery rate in 22 pregnancies (gestational age 30 ± 3 weeks). Results Constants derived from the fit (R 2 = 0.94) were k = 83.1 s −1 ,R 2 , plasma = 1.1 s − 1, andR 2 , RBC = 12.9 s − 1. TheR 2 , RBCand k were found to be larger than those obtained for adult blood, likely the result of differences in dominant hemoglobin type. Data suggest that the use of adult blood calibration could entail errors up 10% in fetal blood HbO 2 . The average umbilical vein blood flow rate (89.5 ± 17.2 mL/min/kg), HbO 2 (84 ± 7%,), and fetal O 2 delivery rate (15.1 ± 3.8 mL O 2 /min/kg) were independent of gestational age. The fetal O 2 delivery rate agreed well with the results obtained with invasive methods at term. Conclusion The present work describes strategies for measuring umbilical vein blood flow rate and HbO 2 in vivo and estimates fetal O 2 delivery rate noninvasively with quantitative MRI during the second and third trimesters of pregnancy. Magn Reson Med 80:1148–1157, 2018. © 2018 International Society for Magnetic Resonance in Medicine.