Rodent Brain Imaging with SPECT and CT

We describe in vivo single photon emission computed tomography (SPECT) and contrast-enhanced computed tomography (CT) techniques to image perfusion and vasculature structures within rodent brains using a combined SPECT-CT scanner dedicated to small animal imaging. A highly-focusing pinhole SPECT with 99m Tc-exametazime (HMPAO) was acquired to image brain perfusion in rat models of stroke. We used a well-established middle cerebral artery occlusion (MCAO) model to induce stroke in rat brains. Validation of the animal model was performed by triphenyltetrazolium chloride staining and histologic analyses. The in vivo imaging results from successful MCAO models were compared against ex vivo autoradiography. A CT with a constant infusion of iodinated contrast media was acquired to image the vasculature around a rat brain including carotid arteries and the Circle of Willis. A visual comparison of image contrast to identify vascular structure in rat brains was made between contrast-enhanced and noncontrast CT images. This CT technique is useful to investigate rat models of intracranial aneurysm. We could identify the region of perfusion deficit indicating infarction through 99m Tc-HMPAO SPECT. Contrast-enhanced CT revealed the vascular structure of carotid arteries and the Circle of Willis, which were invisible by noncontrast CT. We have demonstrated SPECT and contrast-enhanced CT capabilities to investigate cerebrovascular disease identification and treatment studies involving rodent models.