Unilateral intracarotid injection of holmium microspheres to induce bilateral MRI-validated cerebral embolization in rats

BackgroundCerebral embolization models have been hindered by the fact that delivery is predominantly one-sided and cannot be quantified easily. We have developed a model for bilateral cerebral micro-embolization. By using holmium microspheres, it is possible to quantify intracerebral delivery using MRI.MethodsTo validate the quantification of holmium microspheres a phantom study was performed in which concentration of microspheres in solution was compared with the number of holmium-induced artifacts on MRI. After that identical microspheres were administered by unilateral injection in the carotid artery, while the opposite carotid artery was clamped. On post-injection MRI scans, intracerebral delivery and right/left distribution of the microspheres was determined.ResultsIn the phantom study it was shown that quantification by MRI is possible and that MRI artifacts represent single microspheres. In the rat brain, about one-third of the injected dose was consistently located on the contralateral side. The administration was reproducible regarding distribution and number of microspheres.ConclusionsThe use of holmium microspheres enables quantification of delivered dose as single microspheres induce artifacts on MRI. By clamping the contralateral carotid artery, one-third of the dose is diverted to the contralateral hemisphere.