Biomedical Engineering Reference
In-Depth Information
systems can improve the speed and effectiveness of assessing the cardiac condi-
tion. Diagnostic accuracy and therapeutic effect may be significantly improved if
patient-specific engineering information could be provided in a timely manner in
clinical practices.
The first step would typically involve high-resolution imaging techniques to de-
termine the location of cardiovascular problems, such as artherosclerosis in blood
vessels. Despite the significant advances achieved, obtaining real-time CFD solu-
tions to biomedical flow problems are still not well developed due to difficulties in
modelling the physics, in image processing and geometric modelling.
There have been various studies of medical imaging used to support CFD simu-
lation of cardiovascular structures. For instance, a surgical remedy named surgi-
cal ventricular restoration aims to restore abnormal ventricular shape and size for
subjects that are diagnosed with left ventricular dysfunction. The type of medical
imaging and CFD platform used to assess the success of surgical intervention in this
instance can quantify the left ventricle flow behaviour pre-and post-surgical ven-
tricular restoration (eg. usually a combination of flow patterns, pressure differences
in the chamber, vorticity analysis, as well as left ventricle ejection fraction). Studies
have shown that surgical ventricular restoration can reduce left ventricle volumes
and augmented left ventricle ejection fraction (Khalafvand et al. 2014).
Wong et al. (2012b) reviews flow analysis based on computer-aided evaluation
of magnetic resonance intensity images, in comparison with other commonly used
medical imaging modalities. CT and MRI provide excellent anatomical information
on myocardial structures, but fail to show the cardiac flow and detect heart defects
in vivo condition. The computerized technique for fluid motion estimation by pixel
intensity tracking based on magnetic resonance signals represents a promising tech-
nique for functional assessment of cardiovascular disease, as it can provide func-
tional information of the heart in addition to analysis of its anatomy. Cardiovascu-
lar flow characteristics can be measured in both normal controls and patients with
cardiac abnormalities such as atrial septal defect, thus enabling identification of the
underlying causes of these flow phenomena.
9.3.3
MRI Flow Imaging
Cardiac MRI possesses superior resolution, good blood and tissue contrast and of-
fers a wide topological field of view. Unlike X-ray based techniques, it is a nonion-
izing modality. Cardiac MRI allows multiple contiguous slices at various orienta-
tions scanned at various phases of one cardiac cycle. Typically, the scan can either
be short axis (SA) or long axis (LA), and based on the two-chamber (2C), three-
chamber (3C) or four-chamber (4C) configurations, illustrated in Fig.
9.4
.
Estimating motion is achieved by harnessing image signals of varying spatio-
temporal intensity. This theory is based on observations which we can deduce from
visual motion registration. In the context of electromagnetic signals which is analo-
gous to magnetic resonance signals, and based on our knowledge of identifying
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