BOLD MRI in sheep fetuses: a non-invasive method for measuring changes in tissue oxygenation
Article first published online: 21 SEP 2009
Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.
Ultrasound in Obstetrics & Gynecology
Volume 34, Issue 6, pages 687–692, December 2009
How to Cite
Sørensen, A., Pedersen, M., Tietze, A., Ottosen, L., Duus, L. and Uldbjerg, N. (2009), BOLD MRI in sheep fetuses: a non-invasive method for measuring changes in tissue oxygenation. Ultrasound Obstet Gynecol, 34: 687–692. doi: 10.1002/uog.7322
- Issue published online: 1 DEC 2009
- Article first published online: 21 SEP 2009
- Manuscript Accepted: 3 JUN 2009
- Forskningsinitiativet, Aarhus University Hospital
- BOLD MRI;
- brain sparing;
- fetal sheep;
- tissue oxygenation
The purpose of this descriptive study was to correlate changes in the blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) signal with direct measurements of fetal tissue oxygenation.
Seven anesthetized ewes carrying singleton fetuses at 125 days' gestation (term 145 days) underwent BOLD MRI, covering the entire fetus in a multislice approach. The fetuses were subjected to normoxic, hypoxic and hyperoxic conditions by changing the O2/N2O ratio in the maternal ventilated gas supply. The partial pressure of oxygen (pO2) in the fetal liver was measured using an oxygen-sensitive optode. Maternal arterial blood samples were simultaneously withdrawn for blood gas analysis. These measurements were compared with BOLD MRI signals in the fetal liver, kidney, spleen and brain.
We demonstrated a consistent increase in the BOLD MRI signal with increasing tissue pO2. For the fetal liver, spleen and kidney we observed a clear association between changes in maternal arterial blood pO2 and changes in BOLD MRI signal. Interestingly, we found that the BOLD signal of the fetal brain remained unchanged during hypoxic, normoxic and hyperoxic conditions.
This experimental study demonstrated that BOLD MRI is a reliable non-invasive method for measuring changes in tissue oxygenation in fetal sheep. The unchanged signal in the fetal brain during altered maternal oxygen conditions is probably explained by the brain-sparing mechanism. Copyright © 2009 ISUOG. Published by John Wiley & Sons, Ltd.