Biomedical Engineering Reference
In-Depth Information
3.4.2
Left Atrium
1
MRI recordings of 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 tem-
poral resolution of 26 ms was achieved, resulting in 40 frames during one cardiac
cycle. Images were acquired in the four-chamber 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 MR images were analyzed using the freely available
software Segment v1.8 R1172. The anatomical geometry of the atrium was recon-
structed using the automatic segmentation tool to outline the endocardial border in
the short-axis view. By combining both image stacks (short-axis and four chamber
view), the proposed contour in every short-axis slice was evaluated using the in-
tersection points to the four chamber view. If necessary, the contours were refined
using the manual dynamic contour editing tool.
The MRI showed that the subject had the typical pulmonary vein pattern consist-
ing of four main pulmonary veins with four separate ostia. The location and inlet
angle of each pulmonary vein relative to the left atrium were determined with fairly
good accuracy. The veins are denoted left or right according to their position rela-
tive to the center of the body, and superior (upper) or inferior (lower) according to
their distance from the head.
Hence, the name of the four common pulmonary veins are the right superior
pulmonary vein (RSPV), left superior pulmonary vein (LSPV), right inferior pul-
monary vein (RIPV) and left inferior pulmonary vein (LIPV). The orifice of each
pulmonary vein was reconstructed by measuring the major and minor diameter of
each vein in their respective MR scan (see Table
3.1
). The measured values fall
within clinical reported data (Fung 1993; Popel and Johnson 2005). Figure
3.15
shows an elliptic pulmonary vein orifice, the two lines indicate the minor and major
diameters.
Table 3.1
Diameters and areas of pulmonary veins extracted from MRI scans
Left superior
pulmonary vein
Left inferior
pulmonary vein
Right superior
pulmonary vein
Right inferior
pulmonary vein
Minor diameter [mm]
11.9
10.6
12.1
16.1
Major diameter [mm]
15.4
15.8
17.0
16.1
Area [mm
2
]
113.8
131.2
156.4
203.1
1
This section has been contributed to by
S. K. Dahl
in Dahl, S. K., Thomassen, E., Hellevik, L.
R., Skallerud, B. (2012b). Impact of Pulmonary Venous Locations on the Intra-Atrial Flow and
the Mitral Valve Plane Velocity Profile. Cardiovascular Engineering and Technology 3:269-281.
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