A segmentation-based volumetric approach to localize and quantify cerebral vasospasm based on tomographic imaging data

Abstract

IntroductionQuantification of cerebral vasospasm after subarachnoid hemorrhage (SAH) is crucial in animal studies as well as clinical routine. We have developed a method for computer-based volumetric assessment of intracranial blood vessels from cross-sectional imaging data. Here we demonstrate the quantification of vasospasm from micro computed tomography (micro-CT) data in a rodent SAH model and the transferability of the volumetric approach to clinical data.MethodsWe obtained rodent data by performing an ex vivo micro-CT of murine brains after sham surgery or SAH by endovascular filament perforation on day 3 post hemorrhage. Clinical CT angiography (CTA) was performed for diagnostic reasons unrelated to this study. We digitally reconstructed and segmented intracranial vascular trees, followed by calculating volumes of defined vessel segments by standardized protocols using Amira® software.ResultsSAH animals demonstrated significantly smaller vessel diameters compared with sham (MCA: 134.4±26.9μm vs.165.0±18.7μm, p<0.05). We could highlight this difference by analyzing vessel volumes of a defined MCA-ICA segment (SAH: 0.044±0.017μl vs. sham: 0.07±0.006μl, p<0.001). Analysis of clinical CTA data allowed us to detect and volumetrically quantify vasospasm in a series of 5 SAH patients. Vessel diameters from digital reconstructions correlated well with those measured microscopically (rodent data, correlation coefficient 0.8, p<0.001), or angiographically (clinical data, 0.9, p<0.001).ConclusionsOur methodological approach provides accurate anatomical reconstructions of intracranial vessels from cross-sectional imaging data. It allows volumetric assessment of entire vessel segments, hereby highlighting vasospasm-induced changes objectively in a murine SAH model. This method could also be a helpful tool for analysis of clinical CTA.

Large Vessel Vasospasm Is Not Associated with Cerebral Cortical Hypoperfusion in a Murine Model of Subarachnoid Hemorrhage

“…Anesthesia was induced with 4% (v/v) isoflurane for 1 min and maintained with 2% (v/v) isoflurane in spontaneously breathing mice [28]. Body temperature was monitored and maintained at 37°C with a heating pad during all procedures.…”

“…For analgesia, buprenorphine (Indivior, Slough, Berkshire, UK, 0.1 mg/kg body weight) was injected subcutaneously twice daily starting at the time of induction of SAH or sham surgery. SAH was induced under continuous monitoring of ICP, as described previously [28]. Animals were randomized to the SAH or sham group prior to surgery.…”

“…Figure 1 illustrates the experimental setting. Perfusion, Intravascular Casting, Microcomputed Tomography (Micro-CT) of Murine Brains, and Volumetric Analysis of CV After LSCI measurement 72 h after SAH, animals were sacrificed by a perfusion casting procedure with a radiopaque compound (Microfil MV-122, Flow Tech Inc., Carver, Massachusetts, USA), as previously described [28,30]. Brain samples were scanned with a micro-CT (μCT40, Scanco Medical AG, Brüttisellen, Switzerland) with power settings of 70 kVp and 114 μA and a voxel size of 20 μm.…”

“…Resulting DICOM data were imported to Amira® software, version 5.4.2 (FEI Visualization Sciences Group, Hillsboro, OR, USA). The intracranial vascular tree was reconstructed and the vessel volume of a defined 2.5-mm vessel segment of the MCA distal of the carotid T was calculated as previously described [28]. Volumetric analysis was selected on the basis of a methodological study, which compared vessel volumes and diameters in mice with SAH-induced vasospasm [28] and showed that the analysis of vessel diameters can determine vasospasm-induced vascular changes with a greater sensitivity.…”

“…This time point was selected to determine the impact on cortical perfusion at the peak of CV [16,23,24]. We analyzed the vessel volume of a 2.5-mm vessel segment of the left MCA distal of the carotid T, which is a highly sensitive parameter for evaluating vasospasm [28]. Vessel volumes of the left MCA were significantly lower in SAH animals compared to sham animals (SAH, 5.6 ± 0.6 nL; sham, 8.3 ± 0.5 nL, p < 0.01), indicating CV in the SAH group (Fig.…”