Biomedical Engineering Reference
In-Depth Information
Fig. 16.2
Left panel
: magnitude (
top
) and 3D phase contrast velocity (
bottom
) images for a single
slice and cardiac phase from the coronal stack acquired. The TCPC is outlined in the magnitude
image for reference.
Right panel
: TCPC reconstruction with instantaneous velocity streamlines
from the 4D interpolation. Overlaid numbers represent time-averaged percentage contribution for
each vessel to the total venous return. Azy-Azygos vein; HepV-Hepatic venous baffle
flows (red streamlines), which comprised 70 % of the total volume flow rate. Fur-
thermore, only 35 % of flow through the connection exited the RPA, meaning that
a significant portion of the RSVC
Azy flow had to traverse the connection to exit
the LPA. This analysis is consistent with the right-to-left path of some of the red
streamlines seen in Fig.
16.2
, which influenced the hepatic streamlines and forced
a unilateral (left) hepatic distribution, consistent with right-sided PAVM. Based on
these observations, which were made possible by the ability to visualize the
in vivo
flow structures, it is evident that a successful surgical revision of this connection to
address the PAVM must overcome: low momentum hepatic flow, high momentum
superior venous flows, and potentially unfavorable results of their direct interaction.
+
16.2.2 Virtual Surgery
The use of CMR anatomical data to produce patient-specific models for detailed
computational and/or experimental analyses has been a standard practice for the
past decade (Frakes et al.,
2003
; de Zélicourt et al.,
2005
). However, such techniques
can only measure and characterize the current physiology; to prospectively create
connections in a realistic way to explore 'what if' scenarios required additional de-
velopments from the field of computer vision. To this end, a virtual interface was
developed that allowed the user to import patient-specific anatomical reconstruc-
tions (e.g., the TCPC, single ventricle and atria, aorta, pulmonary veins) and mimic
surgical gestures in the placement and deformation of the IVC baffle using free-form
haptic devices (Pekkan et al.,
2008
). Thus, for a given patient anatomy: the size and
