Subarachnoid haemorrhage (SAH) is the leading cause of acute death and permanent disability in people suffering stroke worldwide. 1 Clinical and laboratory investigations have shown that early brain injury (EBI) is closely linked to poor outcomes and the development of delayed cerebral ischaemia in patients after SAH. 2,3 Cerebral blood flow (CBF) autoregulation can be impaired by a wide variety of pathological conditions including post-SAH EBI. For preclinical studies, visualization of anatomy and functional processes is mandatory. Although there are many neuroimaging techniques (eg, magnetic resonance imaging [MRI], single-photon emission computed tomography [SPECT], positron-emission tomography [PET], two-photon excitation laser microscopy, laser speckle and photoacoustic imaging), 4-13 these can suffer from limitations in resolution, insufficient depth, the use of ionizing radiation or expense. High-frequency ultrasound can provide real-time microvascular information noninvasively with high spatiotemporal resolution.With the recent advancement in three-dimensional (3D) power Doppler ultrasound technology, quantitative 3D analysis in the assessment of the vascularization of tumour tissues and foetal brain has become feasible. 14,15 This in vivo study aimed to validate the feasibility of 3D power Doppler-based analysis of CBF during the acute phase of experimental SAH in mice, compared with conventional measurements.
| RE SULTSA total of 25 mice were subjected to SAH by endovascular perforation; 3 (12%) were scored as grade 1, 2 (8%) as grade 2, 11 (44%) as grade 3, and 9 (36%) as grade 4, according to the MRI grading scale. 16,17 Acute infarction was detected in three mice (grade 3 in two mice and grade 4 in one) by diffusion-weighted MRI on day 1.Global depression of 3D reconstructed CBF signals within the scanned brain area (±6 mm coronal slices from the level of the basal ganglia) was notable early (~24 hours) after SAH induction (P < 0.001; one-way analysis of variance [ANOVA] and Bonferroni post hoc test) ( Figure S1). This depression recovered to close to the baseline level
SummaryWe aimed to evaluate the feasibility of a non-invasive method of cerebral blood flow (CBF) measurement using high-frequency power Doppler ultrasound imaging in a mouse model of subarachnoid haemorrhage (SAH). The 3-dimensionally (3D) reconstructed blood flow signals (%vascularity) within the brain volume of the middle cerebral artery territory correlated well with reference parameters, baseline carotid artery blood flow (r 2 = 0.52, P < 0.0001) and normalized CBF changes (r 2 = 0.74 P < 0.0001). These data suggest that the 3D power Doppler analysis may have the potential for reflecting real-time CBF changes during the acute phase of experimental SAH, which may be applicable to preclinical studies on early brain injury.
K E Y W O R D Scerebral blood flow, mouse model, subarachnoid haemorrhage, ultrasound imaging