Tc-99m-ECD brain image on B6 stroke mice animal model by small animal multi-pinhole SPECT – Physical surgical operation alter BBB permeability

Objectives Some evidences reveal that the retention of technetium-99m-ethylcysteinate dimer (Tc-99m -ECD) in rodent brain is not for a long enough period to acquire SPECT image. We use B6 mice stroked by physical surgical operation to evaluate that whether physical processing alters BBB permeability by multi-pinhole SPECT.

Methods Male C57BL/6J mice (20-25 grams) were used in this study. Permanent focal ischemia was induced by occlusion of the right middle cerebral artery (MCA) in mice. We prepared Tc-99m -ECD using a two-vial kit, the concentration of radioactivity was about 20 mCi/mL. The multi-pinhole collimater we used is five pinholes, 1.0 mm aperture. After the onset of MCA occlusion and SPECT imaging, the brain was sliced coronally at 2-mm intervals, stained with TTC and the infracted area was defined. Then ex vivo autoradiography was performed to acquire radioactivity distribution.

Results Regions unstained with TTC, were observed in mice that underwent occlusion of the right MCA. Interestingly, Tc-99m–ECD SPECT imaging demonstrated that higher radioactivity was detected on the same side of ischemia compared with left hemisphere. Besides, ex vivo autoradiography results also showed that more radioactivity on right side identically to SPECT imaging. In addition, control brain without ischemia had equal radioactivity distribution in right and left hemisphere.

Conclusions Our results showed that obviously higher Tc-99m-ECD radioactivity could be detected and displayed parallel to occlusive side than non-occluded side, indicated Tc-99m-ECD retain for longer time in brain after physical surgical operation via altering the BBB permeability.

Research Support This study was supported by grant awarded by the Department of Industrial Technology, Ministry of Economic Affairs, R.O.C