Biomedical Engineering Reference
In-Depth Information
Fig. 16.1
Examples of typically acquired CMR images in relation to a patient-specific TCPC
reconstruction (
central panel
).
Left
: magnitude and phase velocity images through the IVC.
Right
:
axial steady-state free precession (SSFP) anatomic image through the right and left pulmonary
arteries (RPA, LPA); SVC: superior vena cava
16.2 Methods and Results
The fundamental components of the current surgical planning procedure are the fol-
lowing: (i) cardiovascular magnetic resonance (CMR) image acquisition and recon-
struction; (ii) virtual surgery, (iii) computational fluid dynamic (CFD) simulations.
16.2.1 CMR Imaging and Image Processing
Medical imaging provides the patient-specific anatomy and boundary conditions
that inform the rest of the modeling. CMR is the preferred modality as it provides the
means to both image the anatomic structures and make quantitative measurements
of blood flow through variations in the sequence of magnetic field excitation. Fig-
ure
16.1
shows examples of these various image types in the context of the TCPC.
The right image is taken from an axial stack of steady-state free precession images
spanning the thorax. Here, the blood pool in the vessels produces a signal (with-
out the use of a contrast agent), facilitating anatomical reconstruction (Frakes et al.,
2005
). The left set of images shows an instantaneous through-plane phase contrast
measurement in a slice through the inferior vena cava (IVC). By acquiring such
2D images through each of the TCPC vessels, the local velocity fields (inlet/outlet
boundary conditions) can be measured (Sundareswaran et al.,
2009b
).
These acquisitions provide the minimum information required to perform the
subsequent anatomic and fluid mechanical modeling; however, advances in CMR
sequence designs and image processing have provided additional means to directly
assess
in vivo
flow patterns (Sundareswaran et al.,
2012
). Specifically, phase contrast
sequences can be expanded to acquire three orthogonal components of the velocity
vectors on a single slice; furthermore, the vector values between the slices can be in-
terpolated using a novel divergence-free scheme. Therefore, a stack of such images
spanning the TCPC can provide detailed 4D hemodynamic information throughout
