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Atherosclerosis 229 (2013) 459e461

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Atherosclerosis

journal homepage: www.elsevier .com/locate/atherosclerosis

Invited commentary

Pseudo-enhancement does not explain the increased carotidadventitial vasa vasorum signal in diabetic patients

Maria Vittoria Arcidiacono a,b,c, Esther Rubinat b,c,d, Emilio Ortega e, Angels Betriu a,b,c,Elvira Fernández a,b,c, Didac Mauricio b,c, f,*

aDepartment of Nephrology, Hospital Universitari Arnau de Vilanova, Rovira Roure, 80, 25198 Lleida, SpainbUnitat de Detecció i Tractament de Malalties Aterotrombòtiques, Hospital Universitari Arnau de Vilanova, Rovira Roure, 80, 25198 Lleida, Spainc Institut de Recerca Biomedica de Lleida, University of Lleida, Rovira Roure, 80, 25198 Lleida, SpaindDepartment of Endocrinology and Nutrition, Hospital Universitari Arnau de Vilanova, Rovira Roure, 80, 25198 Lleida, SpaineDepartment of Endocrinology and Nutrition, Hospital Clinic, IDIBAPS, Villarroel, 170, 08036 Barcelona, SpainfDepartment of Endocrinology and Nutrition, Hospital Universitari Germans Trias i Pujol, Carretera Canyet, S/N, 08916 Badalona, Spain

a r t i c l e i n f o

Article history:Received 11 May 2013Accepted 13 June 2013Available online 24 June 2013

Keywords:Vasa vasorumCarotid ultrasoundContrast-enhanced ultrasound imagingType 2 diabetes mellitusAtherosclerosis

We read with great interest the comments of Van der Oord et al.on our recently published study [1]. Unfortunately, at the time atwhich our study was designed and conducted [2], the two inter-esting articles on the artifacts produced by pseudo-enhancementduring contrast-enhanced ultrasound (CEUS) imaging of the ca-rotid arteries had not yet been issued [3,4]. We acknowledge that apseudo-enhancement artifact may exist under several conditions,as reported by these authors [3,4], but as they pointed out, there arecurrently no commercially available tools to avoid this artifact. Weare hereby contributing additional comments and data to addressthe issues raised by Van der Oord and colleagues.

We carefully revised the reports on pseudo-enhancement,considering previous data from other researchers and our ownprocedures and database of images. Concerning the procedure usedin our studies, several issues deserve consideration. First, we care-fully selected the patients included in our study. As explained in the

DOI of original article: http://dx.doi.org/10.1016/j.atherosclerosis.2013.04.036.* Corresponding author. Department of Endocrinology & Nutrition, Hospital

Universitari Germans Trias i Pujol, Carretera Canyet, S/N, 08916 Badalona, Spain.Tel.: þ34 934978860; fax: þ34 934978497.

E-mail address: didacmauricio@gmail.com (D. Mauricio).

0021-9150/$ e see front matter � 2013 Elsevier Ireland Ltd. All rights reserved.http://dx.doi.org/10.1016/j.atherosclerosis.2013.06.007

description of the methods [2], the subjects who showed any vesselconditions that precluded adequate conventional and/or contrast-enhanced ultrasound image acquisition were excluded. Theseconditions included any increased echogenic signal in the far arte-rial wall during CEUS imaging (cadence pulse sequencing) beforecontrast injection; this exclusion was made to avoid any possibilityof background artifact images. In addition, only the subjects withconsistent bilateral image acquisition were included. These inclu-sion criteria are stricter than those applied in previous studies.Fortunately, we excluded the subjects who presented vessel wallconditions that otherwise may have produced potential artifactimages similar to those reported in studies describing the pseudo-enhancement effect [3,4]. The images in those two papers clearlyindicate that the areas with high intensity observed during B-modeultrasound coincided with high signals on CEUS imaging that wereconsidered to represent pseudo-enhancement. Similar results werenot observed for the subjects included in our study when wethoroughly re-assessed all of the images, following the recom-mendations of the authors of the commentary [1]. We are herebyproviding additional examples of images in which this phenome-non is not observed (Fig. 1). The readers are encouraged to comparethe images of our procedurewith the pseudo-enhancement images

Fig. 1. Conventional (left) and contrast-enhanced (right) ultrasound images of the common carotid artery in 3 different subjects. Each panel (A, B and C) corresponds to a differentsubject. The areas with high intensity in the far wall on the conventional B-mode images do not correspond to those of the CEUS images. For example, panel B shows a higherintensity in the far wall on conventional ultrasound examination than does panel A; these high intensity images (panel B) do not correspond with higher CEUS signals (less intensein B than in A). As observed in all 3 examples, each of the 3 patients exhibited a different signal. The CEUS images also clearly show the intima-media complex and delimitate themedia-adventitia and intima-lumen boundaries. There are also highly intense signals apparent in the near wall of the carotid arteries (right).

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of previous reports [3,4]. These images do not show the expectedartifact signal, not only from the adventitia, but also from all of theother layers of the arterial wall and the surrounding tissues.Furthermore, it should be noted that to avoid any additional signalbeyond the adventitia, we calculated the vasa vasorum (VV) ratiousing a method that included measuring the intensity of the signalonly in the 2mmbelow the intima-lumen boundary, as explained inthe methods section [2].

In contrast to previous reports, many of the images acquired inour study during the carotid contrast-enhanced ultrasound exam-ination exhibited a high non-specific signal in the near wall of thecarotid artery that could be regarded as artifacts. The readers caneasily identify these hyperechogenic signals in both Fig.1 and in theSupplemental Fig. 1 provided in the original article [2]. The pres-ence of these images prevented us from assessing the VV signal atthis level. It is important to remember that, as for the assessment ofthe intima-media thickness, the optimal ultrasound measurementof the contrast is obtained on the far wall of the artery [5].

Van der Oord et al. admitted that we were able to show animportant difference in the VV signal in diabetic patients withdiabetic retinopathy. Nevertheless, they hypothesized that the

increased signal may be explained by a stiffening of the arterial walldue to the accumulation of advanced glycation end products, pro-ducing a more intense artifact. However, they do not provide anyevidence to support this explanation. Neither advanced glycationend products nor arterial stiffening have been described as sourcesof artifacts in CEUS. Moreover, any accumulated advanced glycationend products would also be present in the intima and especially themedia layer as well; however, ultrasound imaging in our handsdemonstrated the absence of an artifact signal on these layers of thecarotid wall. Alternatively, there is evidence from previous studiesthat the adventitial signal arises from the contrast in the VV. Astudy in an experimental swine model by Schinkel et al. indicatedthat the increased contrast signal measured in the adventitia usingCEUS imaging corresponds to an increased density and extent ofthe VV network of the artery wall according to histopathologicalexamination [6]. Histopathological studies confirmed similar find-ings in humans [7].

As an increased pseudo-enhancement artifact is to be expectedon plaques, it is paradoxical that we found so few plaques thatyielded an intraplaque contrast signal [2]. After careful assessmentof the recorded material of our study, we were unable to identify

M.V. Arcidiacono et al. / Atherosclerosis 229 (2013) 459e461 461

any images of artifact pseudo-enhancement on the plaque tissues.Therefore, in our hands, the pseudo-enhancement artifact is alsoirrelevant for plaque tissue.

A final issue raised by van der Oord et al. is that the artifact effectproduced an overestimation of the density of the VV. It is importantto note here that the reader of all of the images in our study wasblinded to the subject characteristics. Additionally, there is no ev-idence that any artifact effect would have been overestimated insubjects with diabetes with or without retinopathy but not in thenon-diabetic controls. If it was a factor, this overestimation effectshould have influenced the image reading process in all of the studysubjects. Therefore, the differences observed in our study remain asolid finding.

Finally, we strongly feel that the CEUS imaging methodologymerits further research, in addition to a standardization of theprocedures (from the acquisition of images to their analysis andinterpretation). We have been unable to reproduce some of theeffects described by Ten Kate et al. [3]. For example, in contrast tothe observations of the authors in a previous work, we observed alag period between the detection of the signal in the carotid lumenand the appearance of the contrast signal in the adventitia.Therefore, differences arising from the use of various tools andmethods to measure the CEUS signals should not be neglected. It isespecially important to note that the two studies that described thecontrast artifact in carotid arteries used the same device (includingits specific software), and this device is different from the one usedin our study. As described for the intima-media thickness mea-surement [5], also for CEUS imaging differences between sonog-raphers may have a much larger effect than do differences betweenreaders. Future studies should test intraindividual differences usingvarious devices and protocols. Therefore, we are in need of newresearch aimed at improving all CEUS method variations.

Based on the preceding points, we can conclude that ourmethodology allowed us to measure the contrast intensity on theadventitia, which is mainly explained by an increased adventitial

VV in the diabetic subjects. Therefore, we continue to confirm themain conclusion that type 2 diabetic patients with retinopathyshow increased angiogenesis of the VV of the common carotidartery.

Conflict of interest

All authors declare that there is no conflict of interest associatedwith this manuscript.

Acknowledgments

This research was funded by grants No. PS09/01035 and No.PS09/01999 from Instituto de Salud Carlos III, Ministry of Scienceand Innovation, Spain.

References

[1] Van der Oord SCH, Renaud G, Bosch JG, de Jong N, van der Steen AFW,Schinjel AFL. Far wall pseudo-enhancement: a neglected artifact in carotidcontrast-enhanced ultrasound. Atherosclerosis 2013;229(2):451e2.

[2] Arcidiacono MV, Traveset A, Rubinat E, Ortega E, Betriu A, Hernández M, et al.Microangiopathy of large artery wall: a neglected complication of diabetesmellitus. Atherosclerosis 2013;228:142e7.

[3] Ten Kate GL, Renaud GGJ, Akkus Z, van del Oord SCH, Ten Cate FJ, Shamdasani V,et al. Far-wall pseudoenhancement during contrast-enhanced ultrasound of thecarotid arteries: clinical description and in vitro reproduction. Ultrasound MedBiol 2012;38:593e600.

[4] Thapar A, Shalboub J, Averkiou M, Mannaris C, Davies AH, Leen EL. Dose-dependent artefact in the far wall of the carotid artery at dynamic contrast-enhanced US. Radiology 2012;262:672e9.

[5] O’Leary DH, Bots ML. Imaging of atherosclerosis: carotida intima-media thick-ness. Eur Heart J 2010;31:1682e9.

[6] Shinkel AFL, Krueger CG, Tellez A, Granada JF, Reed JD, Hall A, et al. Contrast-enhanced ultrasound for imaging vasa vasorum: comparison with histopa-thology in a swine model of atherosclerosis. Eur J Echocardiogr 2010:659e64.

[7] Coli S, Magnoni M, Sangiorgi G, Marrocco-Trischitta MM, Melisurgo G,Mauriello A, et al. Contrast-enhanced ultrasound imaging of intraplaque neo-vascularization in carotid arteries. Correlation with histology and plaqueechogenicity. J Am Coll Cardiol 2008;52:223e30.