Department of Paediatric Research, Oslo University Hospital, Oslo, Norway.
Invest Radiol. 2011 Nov;46(11):686-96. doi: 10.1097/RLI.0b013e3182266431.
Cerebrovascular factors are crucially involved in the early injury after perinatal asphyxia. With magnetic resonance imaging (MRI) and ultrasonography (US), this study aimed to quantify microvascular perfusion changes due to hypoxia and resuscitation, by comparing contrast-enhanced ultrasound (CEUS) to dynamic susceptibility contrast-enhanced (DSC)-MRI and diffusion-weighted MRI.
Newborn piglets (n = 12/17) were reoxygenated with 21% (n = 6) or 100% O2 (n = 6) after global hypoxia. Five piglets served as controls. CEUS and MRI were performed before, during, and up to 7 hours after hypoxia. Following are the perfusion parameters for CEUS: peak intensity (PI), area under the curve (AUC), time to peak (TTP), and upslope a and perfusion/diffusion parameters for MRI: relative cerebral blood volume, relative cerebral blood flow, mean transit time, and apparent diffusion coefficient were compared between different regions in the brain across time points and also compared with histology at the end.
In CEUS, compared with the control group, perfusion changed significantly over time, in the hyperoxic group in all regions for PI, AUC in all regions of interests. The changes presented mainly as decreased perfusion during and shortly after resuscitation: for PI in the basal ganglia (BG), cortex, and the whole brain with 50 to 60% (P ≤ 0.001); for AUC in the BG and cortex with 90% (P ≤ 0.02) and in the whole brain with 70% (P = 0.004). In the injured brains (confirmed by histology), significant changes over time were seen in TTP and AUC with mainly increased perfusion during hypoxia: for TTP in the cortex, AUC in the BG and whole brain with 90 to 100% (P ≤ 0.04), and for TTP in the whole brain with 50% (P = 0.02). DSC-MRI showed the same trends in perfusion with regard to relative cerebral blood volume as CEUS. In all pigs exposed to hypoxia, perfusion returned toward baseline values at 7 hours after hypoxia in both methods. Apparent diffusion coefficient decreased significantly after 7 hours in the injured brains in the BG from 114.6 ± 1.2 × 10mm/s to 90.3 ± 24 × 10 mm/s (P = 0.03).
CEUS and DSC-MRI can detect an early temporal evolution of cerebral perfusion in perinatal hypoxia and resuscitation, reversible after 7 hours. Hyperoxic resuscitation caused early decreased cerebral perfusion, not present in the normoxic group. The combined use of CEUS and DSC-MRI can provide important diagnostic information and give new insights into perinatal vascular hypoxia mechanisms.
脑血管因素在围产期窒息后的早期损伤中起着至关重要的作用。本研究通过对比超声造影（CEUS）与动态磁敏感对比增强（DSC）-磁共振成像（MRI）和弥散加权 MRI，旨在利用 MRI 和超声检查来量化因缺氧和复苏引起的微血管灌注变化。
新生仔猪（n = 12/17）在经历完全缺氧后用 21%（n = 6）或 100%氧气（n = 6）再给氧。5 只仔猪作为对照组。在缺氧前、缺氧期间和缺氧后 7 小时进行 CEUS 和 MRI 检查。CEUS 的灌注参数包括峰值强度（PI）、曲线下面积（AUC）、达峰时间（TTP）和上升斜率 a，MRI 的灌注/弥散参数包括相对脑血容量、相对脑血流量、平均通过时间和表观弥散系数。将这些参数在不同时间点在不同脑区进行比较，并与终末组织学进行比较。
在 CEUS 中，与对照组相比，灌注在高氧组的所有区域的 PI 和 AUC 均随时间发生显著变化。这些变化主要表现为再灌注期间和之后的灌注减少：在基底节（BG）、皮质和整个大脑中，PI 分别减少了 50%到 60%（P ≤ 0.001）；AUC 在 BG 和皮质中减少了 90%（P ≤ 0.02），在整个大脑中减少了 70%（P = 0.004）。在损伤的大脑（通过组织学证实）中，TTP 和 AUC 随时间发生显著变化，主要表现为缺氧期间的灌注增加：皮质中的 TTP 和 AUC 增加了 90%到 100%（P ≤ 0.04），BG 和整个大脑中的 AUC 增加了 90%到 100%（P ≤ 0.04），BG 和整个大脑中的 AUC 增加了 90%到 100%（P ≤ 0.04），BG 和整个大脑中的 AUC 增加了 90%到 100%（P ≤ 0.04），BG 和整个大脑中的 AUC 增加了 90%到 100%（P ≤ 0.04），BG 和整个大脑中的 AUC 增加了 90%到 100%（P ≤ 0.04），BG 和整个大脑中的 AUC 增加了 90%到 100%（P ≤ 0.04）。在整个缺氧的仔猪中，两种方法均在缺氧后 7 小时内恢复至基线灌注值。在 BG 损伤的大脑中，表观弥散系数在 7 小时后从 114.6 ± 1.2×10mm/s 显著下降至 90.3 ± 24×10mm/s（P = 0.03）。
CEUS 和 DSC-MRI 可以检测到围产期缺氧和复苏过程中早期的脑灌注时间演变，在 7 小时后可恢复。高氧复苏导致了早期的脑灌注减少，而在正常氧组中则没有这种情况。CEUS 和 DSC-MRI 的联合使用可以提供重要的诊断信息，并为围产期血管缺氧机制提供新的见解。
