Download 3D angiography in the interventional clinical routine

Clinical applications
3D angiography in the interventional
clinical routine
K.Willhelm
D. Babic
E DSA is indispensable for
any endovascular therapy.
Department of Radiology, University Hospital Bonn, Germany
Cardio/Vascular Department, Philips Medical Systems, Best, the Netherlands.
Although non-invasive contrast-enhanced
imaging techniques such as CTA and MRA have
become the method of choice for most diagnostic
procedures in vascular diseases, DSA is
indispensable for any endovascular therapy.
Moreover, the number of minimally invasive
image-guided interventional procedures being
performed under angiographic control continues
to increase.
Interventional X-ray angiographic procedures are
still based on real-time fluoroscopic 2D image
guidance. Due to the complex anatomical
vascular architecture and the increasing intricacy
of interventional procedures, three-dimensional
rotational angiography (3D-RA) is rapidly
gaining popularity as it moves out of the research
environment into the clinical setting.
E 3D-RA is a significant
improvement on standard
2D angiography.
24 MEDICAMUNDI 50/3 2006/12
3D-RA is a significant improvement on the
standard 2D angiography imaging, as the added
third dimension allows for a better understanding
of vessel morphology and the relationships
between vessel pathology and surrounding
structures. In complex neuro interventional
angiographic procedures, such as intracranial
aneurysm coil embolization and stenting
procedures, rotational image acquisition with a
fluoroscopic C-arm unit has become an
established method for obtaining vascular 3D
imaging, and provides essential information for
planning and performing the interventional
procedures.
With the introduction of flat-panel detectors, it
has also become possible to acquire CT-like
images via a rotational C-arm system. Flat-panel
detectors have much better contrast resolution
than that of the conventional image intensifiers,
providing high-resolution imaging of nonenhanced soft tissue and bony structures. The
ability to obtain volumetric images immediately
after, or even during, an intervention under
fluoroscopic control in the angio suite is clearly
a key advantage over CT. In addition, the
combined visualization of blood vessels
segmented from 3D-RA data sets with CT and
MRI data sets showing the surrounding
anatomical structures helps in planning and
performing minimally invasive procedures.
These three-dimensional angiographic
techniques, comprising 3D DSA, overlaying of
segmented vessels for 3D-roadmapping, as well
as fusion imaging and Xper-CT, have been used
in numerous vascular and non-vascular
interventions in our department [1]. The
following cases provide an overview of useful
applications. In all cases the new techniques offer
valuable, detailed information while the patient
is still on the angiography table, representing an
important aid to the clinical decision-making.
Materials and methods
All the examinations were performed on an
Allura Xper FD20 angiography system (Philips
Medical Systems, Best, the Netherlands). The
FD20 system (Figure 1) is specifically designed
for angiography and interventional radiology,
and can be used for the acquisition of soft-tissue
data sets (XperCT technique). The system is
equipped with a rotational angiography program,
allowing fast acquisition of data sets for observing
contrast distribution as well as for creating 3D
reconstructions of vessels and soft tissue.
The reconstructions were acquired from patients
with clinically indicated rotational angiography,
and are based on two different acquisition
settings, depending upon the anatomy:
• high-contrast object-based reconstructions
(contrast agent, bony structures) based on
240° movement range with 120 acquired images
F
Figure 1.The Allura Xper FD20
angiography system.
1
• soft tissue-based reconstructions with the same
C-arm movement range but with 310 acquired
images.
The acquisition times were 6 and 10 s respectively.
The matrix size used in both the acquisitions
was 1024 x 1024 with depths of 10 and 14 bits
respectively.
The acquired rotational frames were sent
automatically to the XtraVision workstation
(Dell Computer, Round Rock TX, U.S.A.). The
workstation is fully integrated with the
acquisition system. It provides real-time creation
of 3D reconstructions in the case of the 120frame acquisitions, and reconstructions within
90 s in the case of the 310-frame acquisitions.
The 3D display is directly coupled to the C-arm
geometry, allowing for synchronized movement
of the C-arm and the 3D reconstruction itself.
The Allura Xper FD20 system also allows realtime superimposition of the live fluoroscopy
frames on the 3D reconstructions (3D Roadmapping option). The accurate superimposition
of the fluoroscopic images with respect to the
3D vessel reconstruction is based on the C-arm
geometry, corrected for the slight flexing of the
C-arm due to gravity. The correction is based
on an extension of the calibration method for
volume acquisitions. The relationship between
the live fluoroscopy image and the corresponding
3D vessel reconstruction is maintained for all
random positions of the C-arm, changes in the
X-ray tube/detector distance or changes in
image magnification.
The XtraVision workstation is equipped with
specific software that enables measurement of
vessel 3D geometrical properties for use in
stenting procedures (Virtual Stenting software
functionality). The virtual stents are fitted to the
segments of the vessel defined by the radiologist,
and geometrically assessed in three dimensions
by the computer itself. The virtual stents can be
freely adjusted in order to simulate appropriate
compliance to the vessel wall, and can be virtually
over-deployed in order to assure appropriate
anchoring of the stent material etc.
E The vessel geometry is
measured in three
dimensions for use in
stenting procedures.
The software provides a method for
determining the ideal patient-customized stent
geometry and corresponding dimensions, or for
assessing compliance of the commercially
available stents to the specific patient anatomy.
All the pre-interventional (DICOM based) CT
and MR scans of patients undergoing
interventional procedures can be re-used in the
interventional lab and registered with the periinterventional X-ray images, either in the form
of 3D reconstructions or as 2D live fluoroscopy
images. This matching software (3DRA/CT/MR
matching) provides a highly accurate display of
spatially and contrasting resolutions. Different
data sets are adjusted to the same imaging
matrix and accurately matched on the basis of
common anatomical landmarks.
MEDICAMUNDI 50/3 2006/12 25
Case 1
2a
2b
EE
Figure 2c,d. Lateral view.
2c
2d
Figure 3.Treatment planning.
3a
3b
Figure 2. Right vertebral angiography
showing a fusiform complex
aneurysm of the tortuous
basilar artery.
E
Figure 2a,b. Frontal view.
E
Figure 3a.Three-dimensional volumerendered image from the lateral view
shows the extent of the fusiform
basilar aneurysm. For automatic
aneurysm evaluation.The end and
starting points (green and yellow
circle) for automatic aneurysm
evaluation are defined.
EE
Figure 3b. Automatic aneurysm
measurement and virtual stenting:
The aneurysm was segmented automatically (blue, translucent) showing
geometrical information such as the
size and volume of the aneurysm.
In addition, automated virtual stent
placement (orange) is performed
showing the spatial relationship
between the basilar artery and the
fusiform aneurysm.
Clinical cases
Case 1 Three-dimensional rotational angiography (3D RA) in cerebrovascular stenting. A 64 year old female patient
presented with multiple transient ischemic attacks due to occlusion of the left internal carotid artery.
Diagnostic angiography of the vertebro-basilar system showed an additional fusiform complex aneurysm of the tortuous
basilar artery.
Case 2 Three-dimensional rotational angiography (3D-RA) in cerebral aneurysm.A 66 year old female patient
presented with bleeding from a right middle cerebral artery aneurysm (MCA-A).Three-dimensional angiography with
rotational flat panel DSA is a valuable tool for defining the shape, size and structure of an aneurysm [2].
3D reconstruction gives geometrical information such as the size and volume of the aneurysm.The EndoView mode
26 MEDICAMUNDI 50/3 2006/12
provides additional inside information of the aneurysm neck and the feeding temporo-basal branch.
4a
4b
Case 2
FF/F
Figure 4a,b. Right internal carotid
angiogram (frontal view) showing
lateral MCA aneurysm (arrow).
5a
5b
Figure 5.The three-dimensional
volume-rendered image clearly
shows the aneurysm.
FF
Figure 5a. Maximum intensity
projection (MIP).
F
Figure 5b.Volume-rendered image
(VR).
Case 3 3D-Rotational dacryocystography and Xper-CT for imaging of the lacrimal drainage system [3,4].A 70 year old
female patient presented with a 2-year history of permanent epiphora of the left eye.
6
7a
Case 3
FF
Figure 6. A patient with permanent
epiphora demonstrating complete
obstruction of the nasolacrimal duct
system.
Figure 7. XperCT after
dacryocystography shows the
widened contrast-filled nasolacrimal
sac in relationship to the adjacent
soft tissue end bony structures.
F
Figure 7a. Coronal MPR
8
FF
Figure 7b. SSD.
7b
F
Figure 8. XperCT after
dacryocystography (axial MPR)
demonstrates the soft tissue swelling
within the obstructed left
nasolacrimal duct (arrow) in contrast
to the contralateral duct.
MEDICAMUNDI 50/3 2006/12 27
Case 4
9
10
11
12
E
Figure 9. Fluoroscopy (PA projection)
shows needle placement for
unilateral transpedicular approach.
EE
Figure 10. Lateral view after needle
placement in Th 12 during cement
application.
E
Figure 11. Xper-CT acquired during
the percutaneous vertebroplasty
displays the bony structures and the
paravertebral soft tissue.There is no
cement extravasation.
EE
Figure 12. Image fusion of the
segmented 3D-RA data set and
pre-interventional CT (MPR sagittal
reconstruction) demonstrates
cement distribution overlaid with
the bony structures.
Case 4 Three-dimensional reconstruction with Xper-CT and imaging fusion for planning and control in percutaneous
vertebroplasty [5,6].A 68 year old female patient presented with severe focal back pain related to osteoporotic endplate
fracture of Th 12.A unilateral transpedicular approach was
used for the percutaneous vertebroplasty.
13a
Case 5
Figure 13. PRG tube placement.
Figure 13a. Fluoroscopic image of the
upper abdomen (frontal view)
showing the insufflated stomach
(star).
E
Figure 13b. Xper-CT coronal MPR
shows the widened stomach (star)
in relation to the adjacent soft tissue
structures.There is interposition of
the liver (arrow) or colon.The
access site is localized, showing the
edge of the left liver lobe and the
adjacent transverse colon.
E
Figure 13c. Image fusion of the
segmented 3D-RA dataset (volume
rendered, red) obtained after PEG
placement and the pre-interventional
CT (axial MPR) demonstrates
correct PRG tube placement.
EE
28 MEDICAMUNDI 50/3 2006/12
Case 5 3D-RA and Xper-CT for percutaneous
radiographic gastrostomy (PRG) [7]. Percutaneous radiographic gastrostomy was performed in a 56 year old
male patient with impaired swallowing due to a malignant
esophageal tumor, necessitating enteral feeding.
13b
13c
Case 6 3D-RA and Xper-CT in endovascular abdominal aortic aneurysm repair [8,9]. A 67 year old male patient
presented with a type II endoleak following stenting of an abdominal aortic aneurysm.
14a
14b
Case 6
Figure 14. 3D-RA volume-rendered
images showing an endoleak
originating from two lumbar arteries
(star).
FF
Figure 14a. Left lateral view).
F
Figure 14b. Right lateral view
showing extent of the leak
(translucent blue).
15a
15b
Figure 15a. Xper-CT.The relationship
between the stent, endoleak (arrow)
and feeding lumbar arteries (star) is
nicely shown.
FF
Figure 15a. Sagittal MPR.
15c
F
F
Figure 15b,c. Axial MPRs.
MEDICAMUNDI 50/3 2006/12 29
Case 6 (continued)
16
17
E
Figure 16. Arteriogram obtained
after selective catheterization shows
the feeding vessel supplying the left
lumbar artery (star).
EE
Figure 17. Fluoroscopy during
embolization using a microcatheter
introduced via the left lumbar artery.
Case 7 3D-RA in transcatheter arterial embolization (TACE).A 56 year old male patient presented with multifocal
hepatocellular carcinoma (HCC).
Case 7
18
19
E
Figure 18. Indirect portal venogram
shows splenic artery (white vessel)
and patency of the main, left and
right portal venous branches.
EE
Figure 19. DSA images of the hepatic
artery before therapy show
prominent neovascularization of the
targeted lesion in both liver lobes.
E
Figure 20.Volume-rendered image
shows feeding hepatic vessels,
segmented from 3D-RA dataset.
20
21
EE
Figure 21.The segmented hepatic
vessels overlaid with a slab from the
MR data set show the segmental
arteries feeding the enhancing HCC
foci, allowing selective
catheterization.
Discussion
30 MEDICAMUNDI 50/3 2006/12
The recent advances in minimally invasive
image-guided interventional radiology have
numerous potential clinical benefits. The new
imaging advances are based on the interventional
X-ray imaging platform that allows for real time
2D and 3D imaging, which is highly interactive
and completely incorporated in the interventional
treatment workflow.
The recent integration of the newly developed
soft tissue scanning (XperCT), providing
volumetric scanning capabilities of low contrast
objects (soft tissue) in the interventional lab has
a significant potential for peri- and post-procedural
depiction of intracranial bleedings during neuro
procedures, for neoplastic liver tissue targeting
in transarterial chemoembolization, and for
assessment of cement injection distribution
during vertebroplasty procedures.
The soft tissue scanning performed with the
Allura Xper FD20 system provides higher spatial
resolution than corresponding CT scans, and a
satisfactory contrast resolution that allows for
clinically justified soft tissue differentiation. Soft
tissue scanning can therefore be considered as
clinically proven for use in virtually every
interventional setting.
In transarterial chemoembolization, immediate
3D reconstruction allows better visualization of
the hepatic vascular anatomy with a single
injection of contrast medium [10]. Furthermore,
the 3D roadmap technique and fusion imaging
lead to better detection of tumor feeding vessels,
avoiding the need for multiple DSA and
fluoroscopic views, resulting in reduced radiation
exposure for patients and staff [11].
Conclusion
Having a pre-procedural scan that clearly reveals
intermediate results of the procedures, as well as
providing an instantaneous feedback of the
interventional procedure after completion, has
significantly changed the interventional
workflow in our institution.
We expect that the new soft tissue imaging
technique, in combination with 3D roadmapping,
virtual stenting and automated aneurysm
detection software, will become indispensable
tools in the interventional suite within the near
future. They provide the user with a high level
of confidence during and after the interventional
procedures by providing instantaneous access to
the treatment results during and after treatment.
E The new techniques are
expected to become
indispensable tools in
the interventional suite.
We believe that the new advances described in
this article open new horizons in interventional
treatment that will be both useful to the
radiologist and beneficial for the patient K
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