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Archives of cardiovascular diseases
Volume 103, n° 4
pages 215-226 (avril 2010)
Doi : 10.1016/j.acvd.2010.03.002
Received : 10 February 2010 ;  accepted : 4 Mars 2010
High-resolution coronary imaging by optical coherence tomography: Feasibility, pitfalls and artefact analysis
Tomographie par cohérence optique : faisabilité, limites et analyses des artéfacts d’une imagerie coronaire de haute résolution
 

Pascal Motreff a, , b , Sébastien Levesque a, Géraud Souteyrand a, b, Laurent Sarry b, Lemlih Ouchchane b, c, Bernard Citron a, Jean Cassagnes a, b, Jean-René Lusson a, b
a Department of Cardiology, Gabriel-Montpied Hospital, CHU Clermont-Ferrand, 63003 Clermont-Ferrand, France 
b ERIM-EA3295, University of Auvergne, Clermont-Ferrand, France 
c Department of Biostatistics, Faculty of Medicine, University of Auvergne, Clermont-Ferrand, France 

Corresponding author. Fax: +33 4 73 75 19 33.
Summary
Background

Optical coherence tomography is an imaging method that enables cardiologists to study atheromatous plaques, and to check the implantation and evolution of coronary stents. It is an invasive technique, providing high-resolution (10μm) in vivo images, but with limitations and artefacts that need to be understood before the field of application can be extended.

Aim

To determine the feasibility and limitations of optical coherence tomography coronary imaging from a single-centre experience.

Methods

We analysed the first 301 optical coherence tomography (version M2, LightLab Imaging) sequences obtained in our department from examination of 73 patients.

Results

Results showed that 92% of sequences for selected lesions were usable, with a mean examination time of 17min. Only one complication occurred (ventricular fibrillation, reduced by external electroshock). In our registry, sequence quality depended on operator experience (improving after 20 examinations), and was impaired by artefacts, especially in right coronary analysis and in arteries of greater than 3.5mm calibre.

Conclusions

Proximal coronary occlusion and the distal flush quality currently required for quality imaging should no longer be indispensable with the new generation of optical coherence tomography systems.

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Résumé

La tomographie par cohérence optique (OCT) est une imagerie qui permet en cardiologie d’étudier les plaques athéromateuses, de contrôler l’implantation et l’évolution d’endoprothèses coronaires. Cette technique invasive fournit des images in vivo de haute résolution (dix microns) mais comporte des limites et artéfacts qu’il est important de connaître avant d’en étendre le champ d’application. Nous avons analysé les 301 premières séquences OCT (version M2, LightLab Imaging) obtenues dans notre institution à partir des examens de 73 patients. Il ressort de cette expérience que 92 % des séquences sur des lésions sélectionnées sont exploitables au cours d’examens réalisés en moyenne en 17minutes. Une seule complication a été observée (fibrillation ventriculaire réduite par choc électrique externe). Dans notre registre, la qualité des séquences dépend de l’expérience des opérateurs (meilleure au-delà de 20 examens), est altérée par des artéfacts plus fréquemment retrouvés dans l’analyse de coronaires droites, d’artères de calibres de plus de 3,5mm. L’occlusion proximale de la coronaire et la qualité du flush distal actuellement nécessaires à l’obtention d’une image de qualité ne devraient plus être indispensables avec la nouvelle génération d’OCT.

The full text of this article is available in PDF format.

Keywords : Optical coherence tomography, Feasibility, Limitations, Artefacts

Mots clés : Tomographie par cohérence optique, Imagerie coronaire, Faisabilité, Limites, Artéfacts

Abbreviations : DES, IVUS, OCT, ROI


Background

Optical coherence tomography (OCT) is a high-resolution imaging method based on the reflection of near-infrared radiation by biological tissue [1]. The light emitted by OCT requires a transparent medium in which to propagate. In coronary imaging this is achieved by saline flush downstream of an occlusion balloon. OCT provides cross-sectional imaging of higher resolution than with intravascular ultrasound (IVUS). The precision of OCT imaging of the more superficial layers of the arterial wall makes it the method of choice for analysis of atheromatous plaque and assessment of coronary stents [2, 3, 4, 5]; the latter indication applied to most of the present series.

We report the results of the first 73 examinations performed in our department, with 301 automatic pullbacks exploring 112 stents. Analysing the data from this registry disclosed the artefacts and pitfalls of OCT as a method of coronary imaging, enabling us to better define indications and focus research on post-processing to enhance image quality and improve interpretation.

Methods

Between November 2006 and March 2009, 73 OCTs were performed, during which 112 stents were studied and 301 sequences acquired. All patients provided informed consent to participate in the study.

Optical coherence tomography examination

OCT examination was performed by two operators, following a pre-established protocol. It immediately followed coronary angiography, after intravenous injection of 500mg aspirin and 30IU/kg of unfractionated heparin. The guide catheter used was a 6-French large lumen model. A long guide catheter was progressively inserted beyond the region of interest (ROI) under X-ray control. The coaxial occlusion balloon was positioned upstream of the ROI before the guide was withdrawn.

The fibre-optic connecting to the console (version M2, LightLab Imaging, Westford, MA, USA) was pre-calibrated manually, introduced into the coaxial balloon and carefully fed downstream of the ROI. The occlusion balloon was inflated, using a dedicated manometer, to between 0.5 and 0.7atm. Flush was performed manually, using 30mL of saline in a syringe with a Y-shaped haemostatic connector via the coaxial balloon. When the coronary was flushed with transparent fluid, the OCT image appeared; flush continued during 30s automatic pullback at 1–2mm/s. The balloon was deflated at end of pullback. Images were saved in DICOM format to the LightLab console, enabling re-reading and post-real-time measurement. This protocol is similar to ones described elsewhere [6, 7].

Optical coherence tomography pullback analysis

For each examination, a report detailed the indication, results, limitations and complications, including number of coronaries explored, number of stents studied and number of pullbacks per patient. Examination time was measured from intracoronary introduction of the guide catheter to the end of the last fibre-optic pullback. Procedural complications and hardware problems (e.g., fibre rupture) were inventoried.

For stent analysis, diameters and lengths, time from implantation, rate of complete exploration and number of pullbacks required were recorded.

Concerning pullbacks, artery diameter and site (left anterior descending, circumflex, right coronary artery) were recorded. Pullback quality was assessed by two independent operators, with a third reading in case of disagreement.

Quality criteria

Quality was assessed on predefined scores: 0 equals no usable image; 1 equals less than 50% of pullback images usable; 2 equals greater than 50% of pullback images usable; 3 equals all pullback images usable. An image was defined as usable when the coronary lumen was perfectly distinct from the wall, contrasted, with no break in contour. Pullback acquisition speed was also recorded, as was recourse to proximal occlusion upstream of saline flush.

Artefact identification

Rotation artefacts correspond to false breaks in lumen contour on cross-sectional images. Decentration artefacts are caused by excentric fibre positioning in the lumen, leading to deformation or signal attenuation in the most remote structures and hypersignal in contact structures. Calibre artefacts are caused by an arterial diameter too great for the fibre’s field of exploration to include the entire lumen contour. Flow artefacts comprise all situations of non-optimal lumen transparency (flush defect, incompletely occlusive balloon, or collateral branches). Balloon artefacts occur when the occlusion balloon is present in the most proximal millimetres of pullback, preventing analysis at that point.

Statistical analysis

Quantitative variables are expressed as mean±standard deviation per group. Comparative analysis used the non-parametric Wilcoxon test quantitative variables, and Fisher’s exact test for qualitative variables. All tests were run bilaterally, with first-order risk set at 5%, and performed on SAS v9 software (SAS Institute, Cary, NC, USA).

Results

Table 1 presents the characteristics of the 73 OCT examinations, grouping separately the first 20 and the following 53. Mean exploration time was 17min, with more than four pullbacks per examination. Experience enabled exploration time to be shortened by greater than 4min, despite more sequences being acquired per examination. In all the procedures performed, only one complication arose: a case of ventricular fibrillation at end of acquisition following prolonged occlusion and flush, which was rapidly reduced by external electroshock. Fibre rupture, although always a risk considering the fragility of the fibres, ceased to occur after the 35th examination, and was never of concern for the patient.

The characteristics of the 112 stents are presented in Table 2, distinguishing the same two learning-curve examination groups. The stents were mainly drug-eluting stents (DES), mostly explored 6 months after implantation. In 96.4% of cases, the stent (mean length, 19.39mm) was explored in its entirety, sometimes at the price of iterative pullback (mean number, 1.63 per stent).

Data for the 301 pullbacks are presented in Table 3. Pullback quality was generally good (usable in 92% of cases), and improved with experience (95% for the later examinations). More than half of the good-quality sequences were judged excellent (score 3), and a large majority of the suboptimal sequences (score 2: 43.5% of sequences as a whole) were usable (83% of images per sequence, on average). Taking all acquired images together, 88.8% were usable. It is noteworthy that in the present registry, almost all sequences were acquired with proximal occlusion, and at a pullback speed of 1mm/s.

Artefacts or limitations preventing some or all of the images in a sequence being analysed mainly concerned fibre decentration or proximal presence of the balloon, and affected 30.9% of sequences. Flow, calibre and rotation artefacts were less frequent.

Univariate analysis for factors hindering acquisition of a usable OCT sequence (Table 4) identified large-calibre coronary artery (diameter greater or equals to than 3.5mm) and operator inexperience (affecting both selection of indications and performance conditions: manual flush quality and optimal occlusion balloon positioning). The poorer results for right-coronary OCT analysis may be due to larger arterial calibre (mean 3.37mm±0.47 vs 2.97mm±0.47 elsewhere) and to greater angularity, contributing to fibre decentration (52.9% right coronary artery decentration artefacts vs 19.6% in left anterior descending and circumflex). Increased pullback speed (2mm/s) did not seem to impair image quality.

Discussion

OCT coronary imaging supplements IVUS. The literature shows OCT to be especially useful for analysing the more superficial vessel layers and for checking stents (Figure 1), whereas it is less adapted for assessing deep layers, total vessel area and hence remodelling index [6]. It is also generally agreed that OCT is more complex and difficult to perform than IVUS. Mastering the technique requires in particular a good knowledge of artefacts to optimize indications and avoid interpretation bias [8].



Figure 1


Figure 1. 

Examples of optical coherence tomography images. A. Healthy coronary. B. Thin cap fibro-atheroma plaque. C. Six-month follow-up of a few stents: different levels of neointimal hyperplasia thickness and strut coverage. A few struts remain uncovered (top left). Stent restenosis (bottom right).

Zoom

Technical limitations of optical coherence tomography
Difficulty of locating the exploration region

The OCT light source is not radio-opaque, making it harder than with IVUS to locate the examination region with respect to angiography. Even so, with enough experience, the occlusion balloon and fibre tip can be properly positioned by making use of landmarks. The starting point for automatic pullback acquisition lies 6mm upstream of the tip of the guide catheter, which is radio-opaque over a length of 15mm.

Proximal occlusion

The need to occlude the upstream segment using a poor-profile dedicated balloon hampers exploration of bent segments, segments downstream of angles, and calcifications. Moreover, upstream occlusion precludes analysis of the most proximal segments (left main coronary artery and large-branch ostia) or those immediately downstream of a major bifurcation.

It is noteworthy that although proximal presence of the balloon was inventoried, it did not always impact examination quality, as the resultant artefact lies upstream of the ROI and does not interfere with analysis.

Fibre fragility

The fibre-optic is fragile and physically connected to the console, and so cannot be rotated without risk of rupture. In the present series there were only three cases of rupture, all within the first 35 examinations. Experience enabled up to 10 automatic pullbacks per examination with no deterioration in image quality. To protect the fibre-optic in exploration of complex lesions, it may be preferable to lead the coaxial balloon beyond the ROI and then bring it back once the fibre-optic has been positioned. It is noteworthy that no non-uniform rotational distortion was observed; this type of artefact seems to be less frequent than with IVUS [9].

Limited longitudinal acquisition

Finally, coronary occlusion limits acquisition time to 30s, which in turn limits the length of the analysed segment to 30–60mm, depending on pullback speed (1–2mm/s).

Imaging pitfalls
Movement artefacts

The 0.4 mm-diameter fibre-optic is very mobile within the coronary artery, which itself moves over the cardiac cycle. Acquisition rate is 15.6 images/s (version M2) and longitudinal pullback speed is classically set at 1mm/s. Any sudden movement of the fibre-optic with respect to the artery causes an artefactual break in parietal continuity. On longitudinal reconstruction, this shows up as oscillation in rhythm with the heart beat.

These artefacts are not found with immobile phantoms or explanted heart coronaries, but can easily be induced in test-bench simulation of such movement (Figure 2). Algorithms could be developed to correct such artefacts and reduce the risk of false diagnosis of rupture. Faster pullback and acquisition could also reduce this source of error.



Figure 2


Figure 2. 

Optical coherence tomography images of rotation artefacts on stented (A) and healthy coronary (B). Absence of artefact on immobile acquisitions on phantom (C) or explanted heart coronary (E). Test-bench reproductions of rotation artefacts (60 oscillations/min; amplitude, 1cm) for both models (D and F).

Zoom

Fibre decentration and non-parallelism artefacts

The same kind of decentration and non-parallelism artefacts are found on OCT as on IVUS: the fibre-optic does not always lie in the centre of the vessel or run parallel to the vessel axis, and this deforms the cross-sectional image, which is perpendicular to the fibre axis. Furthermore, the light signal is especially intense in regions close to the light source, and attenuated in more remote regions (Figure 3C).



Figure 3


Figure 3. 

Examples of artefacts on optical coherence tomography cross-sections. A. Decentrated fibre at a large angle. Only the semi-circumference nearer the fibre is analysable. B. Same artery as (A), 4.47mm diameter with centred fibre. C. Signal intense near decentrated fibre and defective illumination of remote structures. D. Petal-shaped deformation on decentrated fibre. E. Flush defect. F. Same coronary as (E) with effective flush.

Zoom

Non-parallelism artefacts are limited by the fibre-optic being contained in the inflated coaxial balloon during acquisition, and are rare when the vessel under exploration is straight (left anterior descending), while the angularities of the right coronary artery are highly subject to this kind of artefact (Figure 3A and 3D). Better analysis of fibre geometry with respect to the lumen could enable such deformations to be corrected; such algorithmic correction could hardly be feasible in real time, but might be applied in post-processing of certain stent parameters.

Large-calibre arteries

OCT analysis is limited to a radius of 3.5–4.0mm, which may not be enough if the probe is decentred or the vessel (e.g., left anterior descending) is too wide (Figure 3A).

Flush quality artefacts

OCT image quality depends on the quality of the flush, which will not be perfect when the upstream diameter makes the balloon less than fully occlusive or in case of collaterality (Figure 3E). A few attempts at acquisition without proximal occlusion, on the other hand, proved disappointing, with insufficient flush and images that were often less usable.

An animal study confirmed that image quality depended on arterial calibre and that flush quality was much improved by occlusion [10]. Automatic injection should improve flush, but the future lies rather in shorter flush times and faster pullback, as with the new generation of fibre-optics [11].

Balloon masking

The occlusion balloon positioned upstream of the ROI may prevent analysis of the most proximal segments (Figure 4).



Figure 4


Figure 4. 

Example of stent analysis hindered by occlusion balloon. Perfect image in (A), unaffected by balloon tip (B). Uninterpretable images due to radio-opaque balloon markers stopping signal (C) or upstream of balloon (D).

Zoom

Interpretation pitfalls

OCT image interpretation needs to take account of the above artefacts; the pitfalls of interpretation, as such, concern tissue characterization and stent analysis.

Depth analysis

Failure of light to penetrate sets a limit to the analysis of deep tissue. Beyond 1.5–2mm thickness on average, the signal is too attenuated for reliable analysis. Dense and thick (fibrosis, calcifications) and especially opaque (metal) structures exert an attenuation effect, which hinders analysis of deep wall structures. Poor signal penetration also prevents assessment of total vessel area and remodelling index in pathological vessels (Figure 5). Moreover, the optical properties of fibrino-cruoric thrombus severely limit penetration by light near the infrared end of the spectrum. In our experience, a large persisting thrombotic load tended to limit OCT analysis of culprit lesions on examinations performed during the first 72hours following acute coronary syndrome.



Figure 5


Figure 5. 

Intravascular ultrasound (top) and optical coherence tomography (OCT) (bottom) cross-sections at same level in pathological right coronary artery (mixed fibrocalcified plaque). Example of advantages and limitations of OCT, with penetration defect preventing full analysis of wall thickness, but higher superficial resolution, enabling measurement of fibrous cap thickness.

Zoom

Tissue characterization

Comparisons with histology have demonstrated the usefulness of OCT in characterising plaque tissue [12, 13]. Even so, discriminating the various components (fibrosis, lipid core, calcification) is not always straightforward in practice, and signal attenuation further hinders deep plaque analysis.

Stent-strut coverage

There have been many reports of OCT study of stent-strut coverage [14, 15, 16, 17]. Nascent re-endothelialization by a thin monocellular layer with a thickness less than the OCT resolution value may go undetected (Figure 6A). Moreover, it is not always possible to specify the type of cover (fibrin, neointimal proliferation or thrombus), although this may sometimes be indicated by the morphological aspect of the signal around the strut (Figure 6B).



Figure 6


Figure 6. 

Ambiguities in analysis of strut coverage in two drug-eluting stents checked at 6 months post-implantation. Some struts appear covered (white arrows), but endothelial coverage may in some cases be too thin for optical coherence tomography’s resolution (10μm) (yellow arrows) (A). Coverage aspect suggests thrombus (red arrows) (B).

Zoom

Shadow cones

As with IVUS, shadow cones are found on OCT in case of structures that strongly attenuate or stop propagation (stent struts, thrombi), although the degree of resolution limits their lateral extension. It is noteworthy that the guide itself does not induce shadow in OCT, as it does in IVUS, since the catheter is coaxial.

Stent-strut apposition

The resolution of OCT is a real advantage in checking stent apposition. Stent struts are superficial and hyper-reflective, making them easily visualized on OCT by hyper-reflection at the interface between the translucid lumen and the metal structure. A clear space between the hyper-reflection and the vessel wall corresponds to strut thickness, which ranges from 60 to 150μm depending on the type of stent. This clear space, extended by a shadow, could be mistaken for malapposition, so that the latter can only be positively affirmed if the distance between hyper-reflection and vessel wall is greater than the known thickness of the strut. This can be demonstrated on a phantom (Figure 7), where a 2.75mm strut is impacted at 20atm inside a latex cylinder of 2.5mm internal diameter: despite perfect strut apposition, there is a clear space between the wall of the hollow cylinder and the strut interface.



Figure 7


Figure 7. 

Illustration of false image of malapposition. A clear space corresponds to strut thickness (yellow rectangles), between wall and luminous signal from the first interface between strut and transparent medium.

Zoom

Quantitative analysis

As in IVUS, measurements should, for reasons of reliability and reproductibility, be made from leading edge to leading edge. OCTs’ high resolution limit quantitative error margins, but some potential bias remains. In our own team, analysis of greater than 10,000 struts by two operators, however, proved entirely reproducible, with a near-perfect kappa value of 0.99. Finally, the M2 version of LightLab Imaging®’s OCT console requires calibration on a known fibre diameter of 0.4mm before any acquisition. An error in calibration (performed at maximum zoom) will affect the reliability of subsequent measurements.

Limitations of optical coherence tomography examination

OCT is invasive, requiring an arterial approach and intracoronary insertion of material. This raises risks of thrombosis and dissection, on top of those entailed by transitory distal occlusion and flush, which generally cause chest pain and considerable transitory ECG disturbance; they may also disturb ventricular rhythm.

Yamaguchi et al. [18] reported the results of a multicentre study in which 76 patients underwent complication-free exploration. The present series included a single case of ventricular fibrillation, reduced by external electroshock, out of 301 acquisitions. This same complication was the one mainly encountered (1.1% of 468 patients) in the multicentre registry published by Barlis et al. [19]. We found no cases of dissection or iatrogenic thrombosis.

Clinical perspectives

The forthcoming new generation of OCT based on optical frequency-domain imaging (OFDI) coupled with new types of fibre will remove certain limitations and artefacts [20]. Despite the non-coaxial guide (a source of artefact), the expected image precision with a claimed axial resolution of 12μm and a speed of 100 images per second should be a great improvement. The main advance is the fibre-optic pullback speed on the C7-XR™ OCT Imaging System (LightLab), which can reach 20mm/s. Per-coronary angiographic injection of contrast medium will enable simultaneous OCT examination of a 60–80mm segment (the artery remaining translucid for the necessary 3–4s). Proximal occlusion will no longer be a requirement, enabling exploration of the large epicardial branches, notably the left main.

Conclusions

OCT is an endocoronary imaging technique providing hitherto unobtainable in vivo information. It is complementary to IVUS, thanks to its high resolution, in the exploration of the more superficial layers.

OCT opens up interesting perspectives for the study of vulnerable plaque and for stent assessment. After a 20-examination learning curve on selected lesions, effectiveness is excellent, with 95% of sequences being usable. It is, however, important to be aware of the limitations, so as to define the optimal fields of application, and to take a critical approach to quantitative and qualitative analysis of results, and finally to develop solutions ensuring progress. The availability of new OCT fibre-optics, further enhancing resolution, will open up new perspectives.

Conflict of interest

None.

References

Prati F., Regar E., Mintz G.S., and al. Expert review document on methodology, terminology, and clinical applications of optical coherence tomography: physical principles, methodology of image acquisition, and clinical application for assessment of coronary arteries and atherosclerosis Eur Heart J 2010 ;  31 (4) : 401-415 [cross-ref]
Barlis P., van Soest G., Serruys P.W., Regar E. Intracoronary optical coherence tomography and the evaluation of stents Expert Rev Med Devices 2009 ;  6 : 157-167 [cross-ref]
Huang D., Swanson E.A., Lin C.P., and al. Optical coherence tomography Science 1991 ;  254 : 1178-1181
Villard J.W., Paranjape A.S., Victor D.A., Feldman M.D. Applications of optical coherence tomography in cardiovascular medicine, part 2 J Nucl Cardiol 2009 ;  16 : 620-639 [cross-ref]
Pinto T.L., Waksman R. Clinical applications of optical coherence tomography J Interv Cardiol 2006 ;  19 : 566-573 [cross-ref]
Kubo T., Akasaka T. Recent advances in intracoronary imaging techniques: focus on optical coherence tomography Expert Rev Med Devices 2008 ;  5 : 691-697 [cross-ref]
Guagliumi G., Sirbu V. Optical coherence tomography: high resolution intravascular imaging to evaluate vascular healing after coronary stenting Catheter Cardiovasc Interv 2008 ;  72 : 237-247 [cross-ref]
Bezerra H.G., Costa M.A., Guagliumi G., Rollins A.M., Simon D.I. Intracoronary optical coherence tomography: a comprehensive review clinical and research applications JACC Cardiovasc Interv 2009 ;  2 : 1035-1046 [cross-ref]
Kawase Y., Suzuki Y., Ikeno F., and al. Comparison of nonuniform rotational distortion between mechanical IVUS and OCT using a phantom model Ultrasound Med Biol 2007 ;  33 : 67-73 [cross-ref]
Asawa K., Kataoka T., Kobayashi Y., and al. Method analysis for optimal continuous imaging using intravascular optical coherence tomography J Cardiol 2006 ;  47 : 133-141
Barlis P., Di Mario C., van Beusekom H., Gonzalo N., Regar E. Novelties in cardiac imaging – optical coherence tomography (OCT) EuroIntervention 2008 ;  4 (Suppl C) : C22-C26
Naghavi M., Libby P., Falk E., and al. From vulnerable plaque to vulnerable patient: A call for new definitions and risk assessment strategies: part II Circulation 2003 ;  108 : 1772-1778 [cross-ref]
Jang I.K., Bouma B.E., Kang D.H., and al. Visualization of coronary atherosclerotic plaques in patients using optical coherence tomography: comparison with intravascular ultrasound J Am Coll Cardiol 2002 ;  39 : 604-609 [cross-ref]
Prati F., Zimarino M., Stabile E., and al. Does optical coherence tomography identify arterial healing after stenting? An in vivo comparison with histology, in a rabbit carotid model Heart 2008 ;  94 : 217-221 [cross-ref]
Suzuki Y., Ikeno F., Koizumi T., and al. In vivo comparison between optical coherence tomography and intravascular ultrasound for detecting small degrees of in-stent neointima after stent implantation JACC Cardiovasc Interv 2008 ;  1 : 168-173 [cross-ref]
Motreff P, Souteyrand G, Levesque S, et al. Comparative analysis of neointimal coverage between paclitaxel versus zotarolimus eluting stent by optical coherence tomography six months after implantation. Arch Cardiovasc Dis 2009; 102(8–9):617–24.
Kim J.S.Jang I.K., Kim J.S., and al. Optical coherence tomography evaluation of zotarolimus-eluting stents at 9 month follow-up: comparison with sirolimus-eluting stents Heart 2009 ;  95 (23) : 1907-1912 [cross-ref]
Yamaguchi T., Terashima M., Akasaka T., and al. Safety and feasibility of an intravascular optical coherence tomography image wire system in the clinical setting Am J Cardiol 2008 ;  101 : 562-567 [cross-ref]
Barlis P., Gonzalo N., Di Mario C., and al. A multicentre evaluation of the safety of intracoronary optical coherence tomography EuroIntervention 2009 ;  5 : 90-95
Barlis P., Schmitt J.M. Current and future developments in intracoronary optical coherence tomography imaging EuroIntervention 2009 ;  4 : 529-533



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