|Animal Cardiac Imaging Frontiers|
Four-Dimensional MR Microscopy of the Mouse Heart
Using Radial Acquisition and Liposomal Gadolinium Contrast Agent
Elizabeth Kathleen Bucholz1, Ketan Ghaghada1, Yi Qi1, Srinivasan Mukundan1, G. Allan Johnson1
1Duke University, Durham, North Carolina, USA
We propose a 3D-plus-time radial (4DRA) MRI pulse sequence that allows rapid acquisition of high-resolution cine images at isotropic 87 μ;m resolution through the use of a liposomal Gd contrast agent. High-resolution images allow more sensitive calucation of functional cardiac parameters, e.g. ejection fraction (EF), end-diastolic volume (EDV), end-systolic volume (ESV) and stroke volume (SV), as well as visualization of coronary arteries and all 4 cardiac valves. The study was applied to 10 mice and EDV, ESV, EJ and SV were measured. The high spatial resolution and rapid acquisition time of 31 minutes present the 4DRA as an excellent candidate for high throughput cardiovascular imaging of the mouse.
Cardiac Magnetic Resonance Imaging Without General
Anesthesia in Mice
Christopher J. Berry1, Daniel R. Thedens1, Nikhil K. Iyengar1, Jordan D. Miller1, Kathy Zimmerman2, Robert M. Weiss1
1University of Iowa, Iowa City, Iowa, USA; 2VA Medical Center, Iowa City, Iowa, USA
The purpose of this study was to determine whether cardiac MRI (CMR) can be reliably performed using deep sedation with midazolam and morphine and to assess its impact on image quality and cardiac function compared to traditional anesthesia protocols. Six normal mice and four mice with ischemic heart failure underwent two sessions of CMR with each anesthesia regimen. CMR performed under deep sedation yielded comparable image quality and significantly less artifactual depression of heart rate and ejection fraction compared to CMR performed under general anesthesia and is thus advantageous over traditional anesthesia protocols for assessment of cardiovascular function.
A Relaxographic Analysis of
Multi-Compartmental Water Exchange in Isolated Perfused Rat Hearts
John Georg Seland1, Morten Bruvold1, Sissel Skarra1, Heidi Brurok1, Per Jynge1
1Norwegian University of Science and Technology, Trondheim, Norway
We have determined water exchange rates across membranes in isolated perfused rat hearts together with volume fractions of the intracellular, intravascular and extracellular compartments. The exchange rate across cell- and vascular membranes was found to be equal in values. Intriguingly the water exchange from ic to ec compartments was found to be more restricted using manganese ions, indicating an intracellular spatially localization of this substance.
Combined Functional MRI and μPET Measurements in a
Mouse Model of Cardiac Infarction
Edwin Heijman1, 2, Lars Stegger3, Michael Schäfers3, Klaas Nicolay2, Gustav J. Strijkers2
1Philips Research, Eindhoven, Netherlands; 2Eindhoven University of Technology, Eindhoven, Netherlands; 3University Hospital of Münster, Münster, Germany
Global mouse cardiac function of a control group (n=12) and infarct group (n=11) were compared with MRI and PET. In addition, for the permanent occlusion model (n=4) and ischemia-reperfusion mouse model (n=4) PET infarct size was determined and compared with contrast-enhanced MRI and CINE MRI infarct size measures. Global functional parameters determined by MRI and PET were in good agreement, while LVM was underestimated by PET. PET infarct size did not correlate with the different MRI infarct size measures, probably caused by the different definition of transmurality. A high correlation was found between MRI ejection fraction and MRI infarct size.
Myocardium Structural Remodeling with Relation of
Infarct Location and Size in Porcine Model Using DTI
Yin Wu1, 2, Hung Fat Tse3, Ed X. Wu1, 2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong; 2Dept. of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong; 3Dept. of Medicine, The University of Hong Kong, Pokfulam, Hong Kong
Myocardial infarction leads to altered myocardium geometry and mechanical function of left ventricle. Infarct size and location have been recognized as the determinants of LV remodeling. However, the effect of infarct location on cardiac remodeling is still controversial. In this study, CMR and DTI were performed to investigate the influence of infarct location and size on myocardium structural and fiber architectural alterations in porcine models. Results indicate that infarct size is the most dominant factor in the overall functional and structural degradation after myocardial infarction. However, both infarct size and location affect the myocardial fiber structural remodeling.
Modified Skeletal Myoblast Therapy for Cardiac
Failure Using AAV SDF1
Bijoy Thattaliyath1, Faris Al-Mousily1, Sean Germain1, Christina A. Pacak1, Stacy Porvasnik1, Yoshihisa Sakai1, Melissa A. Lewis1, Glenn A. Walter, Barry J. Byrne1
1University of Florida, Gainesville, USA
This study was done to evaluate the transplantation of Adeno-associated viral mediated SDF1á modified human myoblast in surgically induced cardiac failure in nude rats. Cardiac MRI was done to evaluate functional recovery and the changes in cardiac wall dimensions following transplant. The main findings of this study are that: 1.SDF1 modified myoblasts are more effective in the improvement of left ventricular function. 2. Myoblasts can be efficiently labeled with superparamagnetic iron oxide particles and followed non-invasively to better understand the cell distribution after transplantation. The improvement in cardiac function can be attributed to the improved contractility, stem cell recruitment and angiogenesis in the infarcted myocardium.
Spiral Cine DENSE MRI at 7T for
Quantification of Regional Function in the Mouse Heart
Xiaodong Zhong1, Robert L. Janiczek1, Brent A. French1, Rene J. Roy1, Christopher M. Kramer1, Craig H. Meyer1, Frederick H. Epstein1
1University of Virginia, Charlottesville, Virginia , USA
Due to limited SNR, DENSE imaging in mice at 4.7T has previously been limited to a single (usually end systolic) cardiac phase. This study developed a spiral cine DENSE method on a 7T scanner with adequate SNR for high-resolution 2D cine DENSE imaging of the mouse heart in 6-8 minutes per slice. These methods allow for the routine use of cine DENSE for the assessment of 2D regional contractile function in mouse models of heart disease, as the data acquisition time is now reasonable with respect to typical acquisition times for other imaging sequences in mice.
MR Study of Postnatal Development of Left Ventricular
Myocardium Structure and Function in Rats
Yin Wu1, 2, Ke Xia Cai1, 2, Kyle Ho Yiu Cheng1, 2, Ed X. Wu1, 2
1Laboratory of Biomedical Imaging and Signal Processing, The University of Hong Kong, Pokfulam, Hong Kong; 2Dept. of Electrical and Electronic Engineering, The University of Hong Kong, Pokfulam, Hong Kong
Development of heart is known to be essential for all organs growth. Numerous studies have been performed to investigate the growth of cardiac myocytes during postnatal period. However, development of myocardial fiber structure, which plays key role in cardiac function, remains to be explored. In current study, CMR and DTI study were performed to examine the myocardium structural maturation concurrent with the cardiac function development in postnatal rats. The results reveal that significant changes in myocardial fiber quality and helical structure mostly occur during the first 28 days. Furthermore, DTI analysis provides a potentially valuable tool to assess the microscopic changes in cellular morphology in heart.
Evaluation of Statin Therapy in a Rabbit Model of
Aortic Valve Sclerosis Using High Resolution MRI
Amanda M. Hamilton1, 2, Kyle A. MacLean1, Maria Drangova1, 2, John A. Ronald1, 2, Brian K. Rutt1, 2, Derek R. Boughner1, 2, Kem A. Rogers1
1University of Western Ontario, London, Canada; 2Robarts Research Institute, London, Canada
Aortic valve sclerosis (AVS) is a prevalent disease with severe clinical consequences but no effective preventative therapy. We propose that MRI can be used to identify AVS early in the disease process at which time pharmaceutical therapies including statins could cause significant improvements. AVS was induced by cholesterol feeding in a rabbit model of the disease for 15 months and progression was monitored with MRI. At 15 months rabbits were subdivided into 5 treatment groups and monitored for an additional 15 months. Initial findings suggest statin therapy modulates the progression of AVS.
Regional OEF Determination with the BOLD Effect in
Normal and Stenotic Dogs
Kyle Stephan McCommis1, Benjamin Edward Northrup1, Haosen Zhang1, Robert J. Gropler1, Jie Zheng1
1Washington University School of Medicine, St. Louis, Missouri, USA
In this project, we used a black blood T2 method to determine the oxygen extraction fraction (OEF) during hyperemia in both normal dogs and dogs with a coronary artery stenosis. In both normal dogs and normal regions of the stenotic dogs, the OEF is dramatically reduced during Dipyridamole-vasodilation. Stenotic regions do not show these significant decreases associated with Dipyridamole, and the effect is attenuated with the stenosis severity. Dobutamine-hyperemia induces very little change in myocardial OEF in normal or stenotic regions. With this MR method, regional OEF changes caused by stenoses and pharmacologic-induced hyperemia can be readily identified.