Pergamon l zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA Original Contribution zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCBA MagneticResonance Imaging, Vol. 12, No. 8, pp. 1183-1190, 1994 Copyright 0 1994 Elsevier ScienceLtd Printedin the USA. All rightsreserved 0730-725X/94 $6.00 + .OO 0730-725X(94)00061-1 HIGH RESOLUTION HIGH FIELD RODENT CARDIAC IMAGING WITH FLOW ENHANCEMENT SUPPRESSION STEPHEN E. ROSE, STEPHEN J. WILSON, FERNANDO 0. ZELAYA, STUART CROZIER, AND DAVID M. DODDRELL Centre for Magnetic Resonance, University of Queensland, St. Lucia Qld 4072, Australia A method that incorporates cardiorespiratory-gated 2DFT spin-echo imaging with blood flow enhancement sup- pression is described which enables high resolution microimaging of the rodent heart. This methodology was ap- plied to obtain in vivo cardiac mouse and rat images with in-plane resolutions of 100-200 pm using high field vertical bore magnet systems. Suppression of intraventricular blood flow enhancement was achieved using a combined spin-echo/gradient-refocussed sequence to dephase magnetization from flowing spins prior to imaging. Keywords: Rodent cardiac MR imaging; Cardiorespiratory triggered imaging; Blood flow enhancement compensation. INTRODUCTION Magnetic resonance imaging (MRI) is now a widely es- tablished diagnostic imaging modality in clinical radio- logical practice. Similarly, MR microscopy and to a lesser extent image guided localized magnetic resonance spectroscopy (MRS) are currently being extensively used to study human disease in laboratory animal mod- els, in vivo. In this field of research, most imaging studies have primarily targeted the rodent brain and ab- domen, using either small or medium bore (~40 cm) horizontal magnet systems. I*’Rodent thoracic imaging, on the other hand, has not been as extensively investi- gated,3-6 partially due to the additional requirement of suitable respiratory and cardiac gating hardware. Com- pared with human MR cardiology, constraints on ro- dent gating hardware are more severe because of the requirement of monitoring and gating heart rates up to 450 beats/min. In our present study we have utilized a modified cardiorespiratory gated 2DFT spin-echo imaging tech- nique coupled with blood flow enhancement suppres- sion to obtain high resolution cardiac images in both the rat and mouse. All imaging experiments were per- formed on vertical bore magnet systems using custom designed shielded gradient sets, birdcage resonator ra- dio frequency (RF) probes and animal handling systems with cardiorespiratory gating capabilities. Although fast scan methods employing ultra fast gradient echo techniques have been successfully used to assess rodent heart dynamic function,’ gated single and multislice spin-echo techniques were utilized in this study to ensure optimal spatial resolution and morpho- logical information. A flow suppression sequence (see Fig. 1) comprising a combined spin-echo/gradient- refocussed preparation sequence (based on a similar scheme proposed by Nishimura et al8 for flow angi- ography) was modified to suppress signal from flow- ing blood. To our knowledge, this is the first reported application of the use of this sequence to minimize vas- cular and ventricular blood flow enhancement. With this methodology, in vivo mouse heart images with in-plane resolutions of - 100 pm (transverse slices, Figs. 3A and 3B) and - 120 pm (sagittal/coronal slices, Figs. 4A and 4B) and rat heart images of -200 pm (transverse slices, Fig. 5A) were readily achievable. With respect to in-plane resolution, we believe the in vivo images presented in this study represent a signifi- cant improvement over previously reported rodent car- diac imaging results. RECEIVED 11/15/93; ACCEPTED 6/16/94. Address correspondence to David M. Doddrell. zyxwvutsrqponm 1181