An Attractive Imaging Modality for Studying Murine Cardiac Function
September 25, 2013
In vivo cardiac imaging in mouse models is widely used as a platform for the rapid translation of new research in cardiovascular medicine to the clinical arena. High spatial as well as temporal resolution is required due to the small size of the mouse heart and rapid heart rate. CT and MR have long been considered as the “gold standard” in this field. However, Dr. Allan Johnson’s group at the Center for In Vivo Microscopy at Duke University has conducted a systematic evaluation of a new generation sub-half-mm microSPECT as a feasible imaging modality, comparing it with microCT for the quantitative in vivo assessment of cardiac function. The microSPECT system used in this study is the U-SPECT-II/CT from MILabs with 0.35mm resolution collimator while their CT system was developed in-house explicitly for dynamic imaging applications. The study has been published in the September issue of Molecular Imaging and Biology.
The use of microSPECT as an imaging modality for studying murine cardiac function had not been widely explored due to the lower resolution of older-generation microSPECT systems. However, the improved, next generation spatial and temporal resolution of the U-SPECT-II/CT enabled the researchers to simultaneously perform anatomic, functional and molecular imaging in control mice and a mouse model with myocardial infarction. The researchers found that despite differences in spatial resolution and CNR (contrast noise ratio), the two modalities, i.e. microSPECT and microCT, showed excellent correlation in measured cardiac function. Quantitative parameters for cardiovascular dynamics such as mean wall motion, wall thickening and regional ejection fraction were closely matched among the two groups. The study also showed good internal agreement between the calculated EDV (End Diastolic Volume) and ESV (End Systolic Volume) values in the datasets for both modalities.
The authors have stated that microSPECT is a valuable alternative to MR for cardiac imaging in mouse models. Both microSPECT and microCT offer the first distinctive advantage over MR in their ability to produce 3D isotropic datasets. A tremendous additional advantage of microSPECT in imaging is that quantitative analysis of both cardiac function and multiple myocardial radiotracer distributions can be done from a single 4D acquisition. This eliminates the need for multiple contrast agents or additional acquisition protocols. It was also found that the U-SPECT could accurately identify the regions of ischemia or infarction that were not visible in the microCT images. The study concludes that state-of-the-art microSPECT, provides distinct advantages over both microCT and MR while also delivering a functional analysis equivalent to that from an advanced microCT system. This firmly establishes it as a valid preclinical imaging tool in the study of murine cardiac function.
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