2. 12 P. Perini et al.
a b
Fig. 2.1 3D-VR (a) and MIP (b) reconstructions of a descending thoracic aortic aneurysm
Fig. 2.2 Practical steps for the generation of a “stretched” aorta using
centreline technique. A centreline of flow (green line; left image) is
generated by the workstation. Before a stretched reconstruction is
obtained (right image), the centreline can be modified by adding,
retrieving, or moving the numerous dots of the line (middle image)
3. 132 Advanced Computed Tomography Imaging, Workstations, and Planning Tools
Nowthat3Dworkstationsareintuitiveand“user-friendly,”
they are accessible to cardiovascular surgeons and not only
experienced radiologists. Reliable default VR and MIP tem-
plates and quick access to advanced segmentation algorithms
that automatically edit and grow vessel territories are essen-
tial (Fig. 2.3).
Vessel caliber, patency, tortuosity, and burden of calcium
and thrombus are important vascular features to assess
preoperatively (Fig. 2.4).
Diameters, lengths, and angles are often necessary dimen-
sions to measure (Fig. 2.5).
Although much of this imaging information can be visu-
alized on conventional axial images, 3D-VR, multiplanar,
and curved planar reconstructions provide quick and clear
visualization of the complex relationships of anatomy and
pathology (Fig. 2.6).
The combined use of the various visualization techniques
is critical in surgical planning.
The advantage of VR is the accurate spatial perception
through a complete 3D angiographic overview. Care, how-
ever, must be taken in interpreting these reformatted images.
For example, a critical stenosis may appear like a complete
Fig. 2.3 3D-VR of a juxtarenal abdominal aortic aneurysm treated
with a fenestrated endograft
Fig.2.4 CPR of a renal artery used for planning a fenestrated endograft
depicting a severe stenosis at the origin of the vessel
Fig. 2.5 Sagittal MPR showing the superior mesenteric artery and its
angle with the aorta. The catheterization of this vessel via a femoral
approach during fenestrated endovascular aneurysm repair is antici-
pated to be challenging (angle of the target vessel to the aortic
wall<60°)
4. 14 P. Perini et al.
occlusion. It is important to correlate 3D findings with corre-
sponding 2D images to avoid such pitfalls. With MPR, a 2D
analysis through the original dataset is performed in axial,
coronal, sagittal, or oblique orientations. Analysis of the ves-
sel wall and the flow lumen with accurate display of stenosis,
occlusions, and calcification can be performed. The only dis-
advantage is the limited spatial display. MIP is also a 2D
analysis option for an angiographic overview, but
semiautomated or complete manual editing is required to
remove structural overlay. It can be useful to depict small
caliber vessels and poorly enhanced vessels. Its accuracy is,
however, limited in calcified vessels. Confirmation of stenosis
and vessel caliber measurements should always be done with
orthogonal MPR. As vessels curve in and out of the planes,
standard MPRs cannot display an entire vascular territory and
flow lumen in one image. To obtain a complete longitudinal
vessel display, the solution is to generate a longitudinal cross-
section using either 2D or rotating CPR techniques.
Themeasurementsrequiredforaccurateplanningofbranched
and fenestrated endografts are complex and beyond the scope of
what can be achieved accurately with standard 2D axial images
and table positions to measure aortic lengths and the relative
positions of visceral arteries. Indeed, there is significant potential
for error when trying to measure aortic lengths using a combina-
tion of coronal and sagittal images of the angulated aorta. The
evolutionofmodernworkstationshasconsignedthesedifficulties
to history with rapid generation of accurate 3D images now fea-
sible in real-time (Figs. 2.7 and 2.8).
It is likely that some of the ongoing improvements in clini-
cal outcomes that are continuously being reported in the endo-
vascular literature are in part attributable to more accurate graft
design, with consequent benefits in terms of improved target
vessel perfusion rates, less graft migration/endoleak, and
shorter procedure times. Clearly, in striving to improve clinical
outcomes, it is incumbent on all endovascular surgeons to
become comfortable with this remarkable technology.
a b
Fig. 2.6 3D-VR (a) and
stretched CPR (b) of an
infrarenal aortic aneurysm
associated with a right common
iliac aneurysm. The combination
of the various visualization
techniques is vital to properly
size and plan the endograft
5. 152 Advanced Computed Tomography Imaging, Workstations, and Planning Tools
Fig. 2.7 Various phases of the planning of a fenestrated endograft using
a workstation. On the upper left, the 3D-VR is generated. The centreline
(in green) is used to generate the stretched CPR (right). The 2D image
(lower left) is the reconstruction perpendicular to the centre-lumen line.
It is used to precisely assess the diameter of the aorta. AAA abdominal
aortic aneurysm, CIA common iliac artery, RA renal artery, SMA superior
mesenteric artery
6. 16 P. Perini et al.
Fig. 2.8 Postoperative 3D-VR of a type II thoracoabdominal aneurysm
treated with a four-branch endograft (right). A meticulous analysis of
the preoperative CT scan on the workstation was mandatory to design
an endograft that perfectly matched the aortic anatomy (left). The length
and diameter of the sealing zone in each target vessel has also been
evaluated. LRA left renal artery, RRA right renal artery, SMA superior
mesenteric artery CT celiac trunk?
