This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. Primary support for the subproject and the subproject's principal investigator may have been provided by other sources, including other NIH sources. The Total Cost listed for the subproject likely represents the estimated amount of Center infrastructure utilized by the subproject, not direct funding provided by the NCRR grant to the subproject or subproject staff.
AIM I nvestigation of the spatial, temporal resolution, and SNR requirements for the optimization, validation and estimation of: i. Myocardial Motion and Eulerian strain using a multimodality realistic heart phantom using DENSE MRI ii. Myocardial strain from the in vivo mouse heart using DENSE MRI METHODOLOGY Animal Preparation and Monitoring: Mice (male/female, CB57L, CD-1, or FVB strains, weightH20-30g) will be induced using 5% isoflurane in a sealed chamber for approximately 3 minutes. The mice will then be mechanically ventilated through a nose cone (with a mixture of 1-2% isoflurane and 100% oxygen to effect), and placed in the supine position in the middle of either a birdcage transmit excitation coil or/and a receive coil, in a specially designed cradle. ECG leads will be attached to the paws and connected to a commercially available fiber optic recording system (SA Instruments Inc.) for monitoring electrical activity and heart rate. A rectal probe will be used to monitor temperature. Air pipes with circulating heated air at a set temperature of 37-38oC will maintain the animals at normal temperature levels. All studies will be performed in accordance with the rules of ethical conduct of research at Duke University and the Institutional Animal Care and Use Committee. DENSE Pulse Sequence Development and Optimization: Implementation of the pulse sequence (PSD) will be achieved by programming in the Excite EPIC environment (EPIC, General Electric, USA), as described in a separate Targeted International Collaboration proposal. In the proposed work, the pulse sequence performance will be assessed and validated in the multi-modality moving phantom and in mice, though phase map reconstructions, optimization of encoding gradients and crusher/spoiler strength-time areas (encoding strength [Genc], time duration [tenc] product), repetition (TR), echo times (TE), and mixing times (TM) for optimal T1-relaxation weighting. Application in in-vivo mouse imaging and optimization of the same parameters for maximum SNR and CNR performance will be conducted in mice, considering its ultra short systolic time intervals (20-30% of the total R-R interval).
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