Pinhole single-photon emission computed tomography for myocardial perfusion imaging of mice

Objectives Although transgenic mice have emerged as powerful experimental models of cardiovascular disease, methods for in vivo phenotypic assessment and characterization remain limited, motivating the development of new instruments for biologic measurement. Background We have developed a single-photon emission computed tomography system with a pinhole collimator (pinhole SPECT) for high-resolution cardiovascular imaging of mice. In this study, we describe a protocol for myocardial perfusion imaging of mice using technetium-99m (99mTc)-sestamibi and demonstrate the feasibility for measurement of perfusion defect size from pinhole SPECT images. Methods Mice were anesthetized and injected with 370 MBq (10 mCi) of 99mTc-sestamibi. Tomographic projection images were acquired by rotating each mouse in a vertical axis in front of a stationary clinical scintillation camera equipped with a pinhole collimator. BALB/c mice (n = 15) were imaged after the permanent ligation of the left anterior descending coronary artery. The resulting defect size was measured from circumferential profiles of short-axis images. After imaging, the hearts were excised and sectioned to obtain ultra-high resolution digital autoradiographs of 99mTc-sestamibi, from which the actual infarct size was determined. Results Reconstructed image quality was equivalent to that obtained for clinical myocardial perfusion imaging. Linear regression analysis produced a correlation coefficient of 0.83 (p < 0.001) between the measured and actual values of the defect size. Conclusions These results demonstrate that myocardial perfusion can be characterized qualitatively and quantitatively in mice using pinhole SPECT.