Andersons pediatric cardiology 200

FIG 7.7 Fetal T1 mapping The T1 map shown here is from a fetal sheep umbilical vein (UV) This approach uses an inversion recovery technique to quantify the rate of recovery of the longitudinal magnetization of blood ROI, Region of interest FIG 7.8 Impact of variation in oxygen saturation on the relationship between T1 and hematocrit (Hct) Reductions in oxygen saturation (SaO2) shorten T1 (A) Adult blood (B) Cord blood FIG 7.9 Noninvasive quantification of oxygen saturation (SaO2), hematocrit (Hct), and blood oxygen content using a combination of vessel T1 and T2 The dotted curve represents all of the possible combinations of oxygen saturation and hematocrit for a given T2 relaxation rate; the vertical line represents the combinations for a given T1 recovery rate The point where the lines intersect indicates the unique solution for oxygen saturation and hematocrit for this combination of T1 and T2 The accuracy of the approach has been proven in vitro, as demonstrated by the comparison with conventional blood gas analysis in Fig 7.10 FIG 7.10 In vitro validation of combined T1 and T2 mapping approach to the noninvasive quantification of (A) hematocrit (Hct) and (B) fetal oxygen saturation (SaO2) Human umbilical cord blood taken from elective cesarian sections was manipulated through a range of oxygen saturations through graded exposure to nitrogen gas and hemodiluted/hemoconcentrated to produce a range of hematocrits Solutions for hematocrit and oxygen saturation based on magnetic resonance relaxometry were compared with conventional blood gas analysis