Microscopic computed tomography imaging of the cerebral circulation in mice: feasibility and pitfalls

This study evaluates the utility and practical limitations of microcomputerized X-ray tomography (CT) as a research tool for examination of the cerebral circulation in mice. Six micro CT angiograms of the circle of Willis (COW) from six mice were obtained by scanning whole head and brain specimen perfused with a radio-opaque silicone contrast agent. Two-dimensional volume rendered images were postprocessed from three-dimensional image datasets using a partially automated high-throughput model that generated 10 surface projections for each specimen. The image processing model employed a straightforward global thresholding and computerized component labeling software algorithm. Postprocessed images were analyzed and results correlated with microdissection. Micro CT demonstration of COW vessels and their branch anatomy was assessed. 71% of COW vessels were completely demonstrated, 26% were partially demonstrated, and 3% were not demonstrated. All cases of nondemonstration and most cases of partial demonstration resulted from scan coverage or postprocessing clip error. Thresholding effect caused pseudostenosis of 8% of COW vessels and accounted for a minority of partial demonstration cases. No imaging artifacts were caused by contrast extravasation or ineffective contrast perfusion. Volume averaging caused minor angioarchitectural distortion of 58% of COW vessels. Ninety-five percent of COW > or =50 microm and 52% of COW vessels <50 microm were correctly identified by micro CT. Micro CT of the murine COW using a high-throughput image processing model is feasible. Angioarchitectural distortion due to volume averaging and thresholding effect can occur and pathological findings should be confirmed.