Wireless self‐gated multiple‐mouse cardiac cine MRI

Abstract

Despite the excellent image-contrast capability of MRI and the ability to synchronize MRI with the murine cardiac cycle, this technique is underused for assessing mouse models of cardiovascular disease because of its perceived cost and complexity. This perception stems, in part, from complications associated with the placement and adjustment of electrocardiographic leads that may interact with gradient pulses and the relatively long acquisition times required with traditional gating schemes. To improve the efficiency and reduce the cost and complexity of using cardiac MRI in mice, we combined wireless self-gating techniques (with which we derived cardiac synchronization signals from acquired data) with an imaging technique that acquires multislice cardiac cine images from four mice simultaneously. As a result, the wireless self-gated acquisitions minimized animal preparation time and improved image quality. The simultaneous acquisition of cardiac cine data from multiple animals greatly increased throughput and reduced costs associated with instrument access. More people die annually from cardiovascular disease (CVD) than from any other cause. It accounts for 1 of every 3.4 deaths globally and one of every 2.8 deaths in the United States (1,2). Small-animal models of CVD are often employed for the evaluation of novel diagnostic and therapeutic approaches to improve our understanding and treatment of disease. Noninvasive, imaging-based assessment of cardiac structure and function improves observational power by allowing disease or injury and response to therapy to be tracked longitudinally without requiring sacrifice at each observation. MRI, as one of such valuable diagnostic tools, can provide good image contrast between myocardium and blood.The potential applicability of MRI-based investigations of small animal models of CVD is reduced because of cost and experimental complexity. Delays associated with the setup of electrocardiographic (ECG) equipment and the inefficient duty cycle of ECG-gated acquisitions limits the utility of traditional prospectively gated cardiac MRI (CMRI). Additionally, the use of metallic ECG leads introduces susceptibility artifacts and can pose problems with coupling to RF and gradient pulses that may distort the anatomy of interest, especially in small-animal investigations (3).Self-gated (SG) imaging techniques allow cardiac phases to be identified from MR data, eliminating the need for ECG signals and systems. The first SG method, described by Spraggins (4), involved a rectilinear double-slice/double-echo pulse sequence, and gating data were obtained through a second readout navigator that was not phaseencoded. Because of the increased acquisition time required by this technique, Larson et al. (5) developed a radial k-space sampling method that avoided the acquisition of extra gating data by extracting the motion synchronization signal directly from imaging data. A short second echo method by Crowe et al. (6) further optimized acquisition efficiency by using a conventional rectilin...

High-throughput in vivo screening of targeted molecular imaging agents

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Multiple-mouse MRI with multiple arrays of receive coils

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