Evaluation of myocardial infarct size in rat heart by pinhole SPECT

Background. High-resolution single photon emission computed tomography (SPE CT) with a pinhole collimator is a new method for evaluating the regional p roperties of radiopharmaceuticals in small laboratory animals in vivo. Alth ough several reports of normal images of rat taken by this new technique ar e available, there are as yet few reports on its use in disease models, suc h as myocardial infarction, In this study, we clearly visualized myocardial flow in the rat heart with myocardial infarction using this system, and ev aluated the relationship between SPECT images and histologic analysis. Methods and Results, For visualization of myocardial flow in rat heart, Tl- 201 images were taken just before and 24 days after left coronary artery li gation, The images were taken using a 4-head SPECT scanner with pinhole col limators. The percent infarct size on Tl-201-SPECT imaging (%SI) and the de fect score were then assessed and compared with the percent infarct size on histologic analysis (%HI). Both the %SI and defect score correlated well w ith %HI (r = 0.97 and 0.74, respectively). Conclusion. Serial SPECT imaging using pinhole collimators permits estimate s of myocardial flow even in small laboratory animals noninvasively in vivo .