This thesis describes the development of three-dimensional power Doppler angiography (3D-PDA) and finally magnetic resonance imaging (MRI) perfusion techniques for the assessment of the human placental blood flow. Assessment of changes in placental blood flow may inform the clinical management of pregnancies complicated by placental dysfunction and allow modification of care with the ultimate aim of improving fetal outcome and maternal health. Ideally this should involve a non-invasive technique. I hypothesised that 3D-PDA would prove to be a reliable tool to quantify placental blood flow and demonstrate reduction in conditions associated with aberrant vascularity such as pre- eclampsia, fetal growth restriction and diabetes. I began by determining the validity of 3D-PDA and whether the 3D vascular indices would change in a predictable manner, by examining their relationship to blood flow in both the myometrium in labour and placental tissue in a phantom model. This work demonstrated that there was a relationship between the 3D vascular indices and flow rates, erythrocyte concentration and depth. The relationship was, however, complex. I then assessed within- and between-observer reliability for both data measurement and acquisition in the placenta at various gestational ages using different measurement techniques depending upon whether the entire placenta could be acquired or not. These experiments revealed variable degrees of reliability and demonstrated that the 3D-PDA whole placental technique before 21 completed weeks' gestation was most reliable. Preliminary experiments testing the reliability of an MRI perfusion technique as a tool to assess placental vascularity in the third trimester are also described in the penultimate chapter. The most reliable 3D-PDA techniques where then used to examine placental vascularity between clinical groups. Between 12 and 21 weeks whole placental FI.fmbv was Significantly higher in the diabetic compared to the normal group [54.48 (SE 0.68); 50.60 (SE 0.54) p=O.OOl] and there was a significant difference across gestation (p=0.003). Between 12 and 32 weeks the stereology within a volume technique demonstrated significant differences in FrVolBV between normal and diabetic subjects (p=0.036) and across gestation (p<O.OOl) and the significant difference occurred between 16 and 32 weeks. Mean FrVolBV was also Significantly lower in subjects with pre-eclampsia 0.107 (SE 0.012) compared to those without 0.139 (0.006); p=0.021.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:555340 |
| Date | January 2011 |
| Creators | Jones, Nia Wyn |
| Publisher | University of Nottingham |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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