212 Material point tracking with enforced incompressibility using MRI
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BioMed Central
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Meeting abstract
212 Material point tracking with enforced incompressibility using MRI Scott Lipnick*, Abbas Moghaddam and J Paul Finn Address: University of California, Los Angeles, Los angeles, CA, USA * Corresponding author
from 11th Annual SCMR Scientific Sessions Los Angeles, CA, USA. 1–3 February 2008 Published: 22 October 2008 Journal of Cardiovascular Magnetic Resonance 2008, 10(Suppl 1):A73
doi:10.1186/1532-429X-10-S1-A73
Abstracts of the 11th Annual SCMR Scientific Sessions - 2008
Meeting abstracts – A single PDF containing all abstracts in this Supplement is available here. http://www.biomedcentral.com/content/pdf/1532-429X-10-S1-info.pdfThis abstract is available from: http://jcmr-online.com/content/10/S1/A73 © 2008 Lipnick et al; licensee BioMed Central Ltd.
Introduction Phase-contrast (PC) MRI and displacement encoding with stimulated echoes (DENSE) MRI can be used to image heart muscle contraction, from which unique insight into a variety of cardiac diseases can be acquired. Abnormal function can be a result of impaired blood flow and/or tissue necrosis as in coronary artery disease or other primary diseases of the heart muscle. Accurate displacement information is necessary for calculation of strain, which is considered a key indicator of myocardial function. We propose a method for material point tracking using PCMRI and DENSE-MRI. In order to ensure accurate tissue tracking it is important that material point displacement is physiologically constrained. Muscle tissue maintains constant density at all times, which through conservation of mass this leads to the divergence of the velocity field equaling zero. The proposed method enforces the physiological constraint of incompressibility through a multiresolution Gauss-Seidel successive over-relaxation technique. After enforcing incompressibility material points follow physiological tracks. This study describes the implementation of the tissue tracking method and subsequent clinical trials.
ity through minimizing the divergence of the instant velocity which is acquired from the data field; instantaneous velocity in PC-MRI, and displacement in DENSE-MRI. Further, we evaluate the feasibility of the proposed method using simulations.
Methods In PC-MRI instantaneous velocity is directly encoded in the phase of the magnetization, as opposed to DENSEMRI where displacement is directly encoded. If we assume that the phase step is small enough that there is minimal change in the velocity we can conclude the displacement is proportional to the instantaneous velocity. The tissue tracking method can be summarized through three steps: 1) Removal of high frequency spatial modulations in the velocity through Fourier analysis. 2) Enforcing tissue incompressibility through minimizing the divergence of the velocity field. To acquire the numerical solution we use an iterative multi-resolution method with the Gauss-Seidel successive over-relaxation method.
Purpose A limitation in tissue tracking and subsequent strain calcul
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