Biomedical Engineering Reference
In-Depth Information
flow evaluation. Nevertheless, the visualization of flow patterns remains concise for
the two modes of flow field generation.
The comparison of flow results by experimental and computational approaches
showed good qualitative and quantitative agreements. The simulated results were
validated using the measured flow from velocity-encoded medical imaging success-
fully. The proposed functional analysis using combined phase contrast MRI and
CFD is of interest to research into the pathologies or interventions which involve
altered relations between form, flow, mobility, and timing of the heart.
7.6
Intra-Atrial Flow and Mitral Plane Velocity Profile
2
The left atrium is the upper left chamber of the heart and connected to the left
ventricle via the mitral valve. Intraventricular flow has been widely investigated
during the last decades both in vivo, in vitro and by computational fluid dynamics
(CFD). In this section we present a three-dimensional computational fluid dynam-
ics framework of the left atrium and its pulmonary veins. MRI is used to render
subject-specific atrial and venous geometries to investigate: the diastolic flow field
in an anatomically representative model of the left atrium and the pulmonary veins;
the impact of different venous entry locations on the intra-atrial flow and; the result-
ing mitral plane velocity distribution. Three 3D models with different venous entry
locations were created.
7.6.1
Left Atrium Models
3D geometries were obtained from MRI recordings of a young healthy adult. This
included the left atrium and each of the pulmonary vessel stubs were acquired from
a 25-year-old healthy male on a Siemens Avanto 1,5 T system. A temporal resolu-
tion of 26 ms was achieved, resulting in 40 frames during one cardiac cycle. Images
were acquired in the four-chambers (Fig.
7.35
) and the short-axis orientation. A
total of 14 slices with a slice thickness of 5 mm were needed in both orientations
to cover the atrium and the mitral plane. In-vivo measurements of the flow velocity
through the mitral orifice and the mass flow rate through each of the venous inlets
were performed by velocity phase mapping scans.
The segmentation data was used to build a subject-specific atrial geometry. The
first model, denoted
C
A
has its four pulmonary veins located in the anatomically
correct positions adopted from the magnetic resonance recordings. The geometry
of
C
A
is shown in Fig.
7.35a
,
b
. There is close proximity between the ostia of the
right pulmonary veins and between the ostia of the left pulmonary. In general, and
2
This section has been contributed to by
S. K. Dahl
, in Dahl, S., Thomassen, E., Hellevik, L.,
Skallerud, B. (2012a). Impact of Pulmonary Venous Locations on the Intra-Atrial Flow and the
Mitral Valve Plane Velocity Profile. Cardiovascular Engineering and Technology 3:269-281.
Search WWH ::
Custom Search