CT virtual endoscopy and 3D stereoscopic visualisation in the evaluation of coronary stenting
1 Discipline of Medical Imaging, Department of
Imaging and Applied Physics, Curtin University of Technology, Perth, Australia
2 School of Public Health, Curtin University of Technology, Perth, Australia
The aim of this case report is to present the additional
value provided by CT virtual endoscopy and 3D stereoscopic visualisation when
compared with 2D visualisations in the assessment of coronary stenting. A
64-year old patient was treated with left coronary stenting 8 years ago and
recently followed up with multidetector row CT angiography. An in-stent
restenosis of the left coronary artery was suspected based on 2D axial and
multiplanar reformatted images. 3D virtual endoscopy was generated to
demonstrate the smooth intraluminal surface of coronary artery wall, and there
was no evidence of restenosis or intraluminal irregularity. Virtual fly-through
of the coronary artery was produced to examine the entire length of the
coronary artery with the aim of demonstrating the intraluminal changes
following placement of the coronary stent. In addition, stereoscopic views were
generated to show the relationship between coronary artery branches and the
coronary stent. In comparison with traditional 2D visualisations, virtual endoscopy
was useful for assessment of the intraluminal appearance of the coronary artery
wall following coronary stent implantation, while stereoscopic visualisation
improved observers� understanding of the complex cardiac structures. Thus, both
methods could be used as a complementary tool in cardiac imaging. � 2009
Biomedical Imaging and Intervention Journal. All rights reserved.
Keywords: Coronary artery disease, virtual endoscopy,
coronary stent, three-dimensional visualisation, stereoscopic visualisation
In recent years, coronary artery disease has been
increasingly treated by coronary stent placement. Although stent implantation
has been shown to greatly reduce restenosis after balloon angioplasty [1, 2],
in-stent restenosis can occur in 20-35% of patients for bare metal stents [3,
4], and 5-10% for drug-eluting stents [3, 4]. Conventional catheter-based
coronary angiography remains the gold standard technique for detection of
in-stent restenosis. However, coronary angiography has limitations due to its
invasiveness and associated potential risks of morbidity and mortality. Given
the high number of patients who receive coronary stents yearly, a non-invasive
imaging technique for follow-up of coronary stenting and detection of in-stent
restenosis will be clinically important and beneficial.
Currently multi-detector row computed tomography (MDCT) is
increasingly used for non-invasive imaging of coronary artery disease and has
been reported to have a high diagnostic accuracy in the detection of coronary
artery stenosis and in-stent restenosis, especially with the development of the
latest 64-detector row CT scanners [5-7]. Nearly isotropic volume data are
acquired with 64 MDCT scanners which allow generation of a series of 3D
reconstructions of the coronary artery and stents. Of these reconstructions,
multiplanar reformation (including curved reformation), maximum-intensity
projection and volume rendering are commonly used in the visualisation of
coronary stenting. In contrast, two other types of 3D visualisations including
virtual endoscopy and stereoscopic views offer additional information when
compared to 2D reconstructions. Virtual endoscopy offers unique intraluminal
views of the artery lumen and stent structures [8-10], while stereoscopic visualisation
provides a realistic 3D view which allows demonstration of complex anatomic
structures [11, 12].
In this case report, we presented our experience of using
virtual endoscopy and 3D stereoscopic views for visualisation of the coronary
artery and coronary stent in a patient treated with coronary stenting. The aim
of the case report was to identify the potential value of these 3D
visualisations in demonstration of complicated cardiac structures when compared
to conventional 2D visualisations.
A 64-year old man presented with exertional angina in 1998
and was investigated with an exercise ECG, which showed weakly positive
results. Thallium scans were negative for differential differences in left
ventricular coronary artery flow. Persistent angina was further investigated in
1999 with coronary angiography and showed a 70% stenosis at the origin of the
left main coronary artery. This was treated with a Left Internal Mammary Artery
(LIMA) bypass to the descending and long saphenous Vein Bypass (LSV) to the
circumflex coronary arteries. Angina persisted and repeated angiography in 2000
showed that the LIMA bypass was not patent and the stenosis had progressed. The
origin of the left main coronary artery was treated with a bare stent and
dilated to 4 mm. In 2008 further investigation was requested for travel
insurance and the CT angiography was performed to avoid invasive investigation.
Imaging Generation and Visualisation
Conventional 2D reconstructions
Coronary CT angiography was performed using a 64-detector
row CT scanner (64x0.625, Lightspeed VCT, GE Medical Systems) with a section
thickness of 0.625 mm and reconstruction interval of 0.4 mm. Curved
multiplanar reformatted images were generated at the CT scanner workstation.
Figure 1 shows the multiplanar views of right and left coronary arteries. Left
coronary stent was confirmed to be patent on CT images, but restenosis was
suspected at the left coronary artery based on the multiplanar reformatted
Virtual endoscopy and 3D stereoscopic visualisation
The original DICOM (digital imaging and communication in
medicine) data was transferred to a separate workstation equipped with Analyze
V 7.0 (AnalyzeDirect, Inc., Lexana, KS, USA) for generation of virtual
endoscopic and stereoscopic images. Generation of virtual endoscopic images was
performed with a CT thresholding technique, which has been described before
. Intraluminal views of the proximal, middle and distal left stented
coronary artery were produced with no evidence of restenosis, as shown in
figure 2. The lumen of the left coronary artery remained smooth and there was
no sign of any endothelial thickness or endoluminal irregularity caused by the
In addition to the static virtual endoscopy
visualisations, we also produced dynamic fly-through of the coronary arteries
with the aim of demonstrating the entire coronary arteries. This was performed
by setting a number of virtual cameras along the path of the coronary arteries.
A fly-through of the left coronary artery including left anterior descending
and left circumflex branch confirmed the findings of static virtual endoscopic
visualisations, which showed the smooth appearance of coronary lumen.
A stereoscopic pair of images consists of two projections
of the same 3D object acquired from two slightly different viewing angles. The
pair of stereoscopic images is displayed so that only the left eye sees the
left projection and only the right eye sees the right projection. As a result,
the observer is able to reconstruct and appreciate the 3D object mentally
including the depth dimension. In our study, the reviewers used red/blue
glasses for the stereoscopic display of the cardiac anatomic structures as
shown in Figure 3. This allows the reviewers to better appreciate the complex
anatomic structures when compared with 2D visualisations.
Discussion and Conclusion
MDCT has been increasingly used for the diagnosis of
coronary artery disease and follow-up of coronary stenting due to its improved
spatial and temporal resolution, especially with the advancement of 64‑detector
row scanners [5-7]. In addition to axial CT images, a number of reconstructed
visualisations are essential and play an important role in the demonstration of
complex coronary arteries. Of these reconstructions, curved multiplanar
reformation is the most commonly used tool for visualisation of the coronary
artery tree, complemented by maximum-intensity projection or volume rendering.
However, there are still limitations with curved multiplanar reformation as it
does not provide intraluminal information about the coronary artery or coronary
stent. This can be easily resolved with virtual endoscopy and virtual
fly-through visualisations, as reported previously in other endovascular
Our results in this case study demonstrated the
superiority of virtual endoscopy with intraluminal views over conventional
extraluminal visualisations. This is manifested by visualisation of the smooth
intraluminal surface in both stented and normal coronary artery lumen. In this
case, virtual endoscopy excludes the presence of coronary in-stent re-stenosis
or any stent-related changes in the coronary artery wall.
We also included stereoscopic visualisation in this case
and our results showed that it offers better understanding of the complex
cardiac structures. Our previous study confirmed that stereoscopic viewing
provides additional information regarding any distortions of the fenestrated
stents compared with conventional 2D visualisations . Thus, stereoscopic
visualisation was recommended as a complementary tool for follow-up of
fenestrated stent grafting. Similarly, this visualisation tool can be used as
complementary to 2D views in the follow-up of coronary stenting, although this
needs verification in a large cohort.
Drug-eluting stents are increasingly being used in
clinical practice with the aim of preventing in-stent restenosis, and research
has shown the decreased incidence of stent re-stenosis when compared to bare
metal stents [13, 14]. However, there is growing concern that delayed
endothelisation and incomplete neointimal healing might lead to adverse cardiac
outcomes and death as a result of late or very late stent thrombosis [15, 16].
The inevitable arterial injury due to balloon deployment of a stent coupled
with the presence of a metallic foreign body can cause inflammatory and
proliferative responses . The development of in-stent restenosis after
implantation is due to the neointimal hyperplasia around the stent in the
arterial lining, which increases the risk of blocking the artery again. We
believe that virtual endoscopy, as a unique visualisation technique of
presenting the intraluminal appearance of arterial wall as shown in our report,
can be used as a valuable tool to identify any intimal changes of coronary
artery due to tissue overgrowth before it leads to in-stent restenosis or
thrombosis. With the aid of virtual endoscopy visualisation, this might then
influence the time period needed for antiplatelet therapy, especially if
further major open surgery is required. The potential applications of virtual
endoscopy and stereoscopic visualisation in coronary stenting lie in the
following aspects based on our report:
- Follow-up of coronary stenting (especially drug-eluting stent) with
regard to the appearance of intraluminal wall with the aim of identifying the
artery wall changes by use of virtual endoscopy;
- Confirmation of suspected in-stent re-stenosis in any section of the
coronary artery branch with aid of virtual endoscopy;
- Enhancement of endovascular specialists� understanding of the
relationship between coronary stents and coronary arteries and appreciation of
complex anatomic structures with the aid of 3D stereoscopic visualisation.
Figure 1 (a) Is a multiplanar reformatted image of the right coronary artery, while (b) and (c) show the left coronary artery with coronary stent implanted (arrows) at the ostium of left main stem, visualised on multiplanar reformatted and 2D axial views.
Figure 2 (a) Virtual endoscopy views of the ostium, and (b) proximal segment of left coronary artery, (c) left anterior descending (LAD), and (d) left circumflex (LCX). The internal wall of these artery branches looks smooth on virtual endoscopy images with no sign of intraluminal irregularity.
Figure 3 Stereoscopic visualisation of right coronary artery and left coronary stent as well as bypass graft compared with conventional surface rendered visualisation, observed in (a) frontal view and (b) lateral view. (red/blue glasses are required to appreciate the stereoscopic effect).
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|Received 18 May 2009; received in revised form 2 July 2009, accepted 15 July 2009
Correspondence: Discipline of Medical Imaging, Department of Imaging and Applied Physics, Curtin University of Technology, GPO Box, U1987, Perth, Western Australia 6845, Australia. Tel.: +61-8-9266 7509; Fax: +61-8-9266 2377; E-mail: firstname.lastname@example.org (Zhonghua Sun).
Please cite as: Sun Z, Lawrence-Brown MMD,
CT virtual endoscopy and 3D stereoscopic visualisation in the evaluation of coronary stenting, Biomed Imaging Interv J 2009; 5(4):e22