Enhanced Stent Imaging Improves the Diagnosis of Stent Underexpansion and Optimizes Stent Deployment

Original Studies

Enhanced Stent Imaging Improves the Diagnosis ofStent Underexpansion and Optimizes Stent Deployment

Elias A. Sanidas, MD, Akiko Maehara, MD, Ravit Barkama, MD, Gary S. Mintz, MD,Varinder Singh, MD, Ariel Hidalgo, MD, Diaa Hakim, MD, PhD, Martin B. Leon, MD,

Jeffrey W. Moses, MD, and Giora Weisz,* MD

Objectives: To investigate the clinical value and diagnostic accuracy of enhanced stentimaging (ESI) as compared with quantitative coronary angiography (QCA) and intravascu-lar ultrasound (IVUS). Background: ESI is an image acquisition and processingangiography-based software that improves visualization and provides measurements ofdeployed stents. Methods: A total of 40 consecutive patients (42 stents) were studied.Stent deployment was evaluated sequentially and independently by angiography, ESI, andIVUS. Following each imaging modality, the operator determined the necessity of postdila-tion unrelated to the other modalities. Stent diameters were measured off-line by QCA,ESI, and IVUS at several sites along the deployed stent and compared. Results: Followingstent deployment and based solely on angiography, the operator decided to postdilateseven of the 42 stents (16.7%). This decision was not changed after reviewing the ESIimages of these seven stents. Of the 35 stents not requiring postdilation based on angiog-raphy alone, ESI influenced the operator to change the decision and postdilate 10 of 35stents (28.6%). The ESI-based measurements had better correlation with IVUS (r 5 0.721,P < 0.0001) than did QCA with IVUS (r 5 0.563, P < 0.0001). Bland-Altman analysis showeda trend towards better agreement between ESI and IVUS than between QCA and IVUS(mean differences 5 0.038 vs. 0.121; P 5 0.19, respectively). Conclusions: ESI is an easyto use modality that enhances stent visualization, helps in the decision making processwhether to postdilate the stent, and provides estimation of stent expansion with bettercorrelations than QCA when compared to IVUS. VC 2012 Wiley Periodicals, Inc.

Key words: coronary artery disease; angiography; percutaneous coronaryinterventions; intravascular ultrasound; enhanced stent imaging

INTRODUCTION

Coronary angiography is the primary imaging mo-dality used to evaluate coronary artery disease (CAD)severity and guide percutaneous coronary interventions(PCI). The success of PCI is related to precise deploy-ment of stents in terms of placement and expansion.Current stents are minimally radiopaque, and standardfluoroscopic angiography has limited sensitivity indiagnosing stent underexpansion. Postinterventionimaging with intravascular ultrasound (IVUS) candetermine whether there is adequate stent expansion,but is not often used.

Stent underexpansion is a strong predictor of stentthrombosis and restenosis. The final minimum stentarea (MSA) is considered to be a major determinantfactor of drug-eluting stent (DES) restenosis [1–5].Furthermore, stent underexpansion has also been a

New York-Presbyterian Hospital, Columbia University MedicalCenter and the Cardiovascular Research Foundation, NewYork, New York

Conflict of interest: Dr. Barkama was a prior employee of Paieon

(until June 2008), but currently has no other potential conflict of inter-

est with the sponsor. Dr. Maehara has received research/grant support

from Volcano Corporation and Boston Scientific Corporation.

Dr. Mintz is consultant for Volcano Corporation and Boston Scientific

Corporation and has received grant/fellowship support from both

Volcano Corporation and Boston Scientific Corporation. Dr. Leon is

member of the advisory boards for Boston Scientific Corporation.

*Correspondence to: Giora Weisz, MD, Columbia University, Center

for Interventional Vascular Therapy, Columbia University Medical

Center, 161 Fort Washington Ave., 5th Floor, New York, NY 10032.

E-mail: [email protected]

Received 4 August 2011; Revision accepted 21 January 2012

DOI 10.1002/ccd.24353

Published online in Wiley Online Library (wiley

onlinelibrary.com)

VC 2012 Wiley Periodicals, Inc.

Catheterization and Cardiovascular Interventions 00:000–000 (2012)

consistent finding in IVUS reports of acute or subacutestent thrombosis [6,7].

Enhanced stent imaging (ESI) is an angiographybased software tool designed to improve visualizationof deployed stents and to provide quantitative dataregarding stent dimensions. The aim of this study wasto assess the impact of an ESI system on poststent dila-tion strategy and to compare the ESI measurements toquantitative coronary angiography (QCA) and IVUS.

METHODS

Study Population

This was a non-randomized study that includedpatients who had planned IVUS guided stent implanta-tion. Total of 40 consecutive patients who underwentPCI with stent implantation were enrolled. Patients withacute ST-elevation myocardial infarction (STEMI),hemodynamic instability, and pregnant or nursingfemale patients were excluded. Baseline demographicand procedural characteristics of all patients werecollected. The protocol was approved by the institu-tional review board, and written informed consent wasobtained from all patients.

Procedure Flow

The study was performed according to the followingsteps: (1) conventional stent deployment with poststentangiograms in two orthogonal projections; (2) ESI withthe StentOptimizer algorithm to create an enhancedimage of the stent in two orthogonal projections that wastemporarily hidden from the operator; (3) documentingthe decision of the operator whether to postdilate thestent based on the poststent angiogram; (4) display theESI images and documenting the operator’s decisionwhether the ESI images changed the decision to postdi-late the stent; (5) IVUS imaging and analysis on-line; (6)final decision, IVUS-based, whether to postdilate thestent. This procedural decision was made by the opera-tor, and was not based on protocol pre-defined criteria.

Enhanced Stent Imaging Procedure

The StentOptimizer is part of an image acquisitionand processing software system (IC-Pro, Paieon Inc.)designed as an add-on to conventional X-ray angio-graphic systems. After stent deployment and balloondeflation, an enhanced stent image is produced from aminimum of 20 cine frames over 3 sec using the radio-paque markers of the delivery balloon as an anchor toalign the stent across all frames. The StentOptimizersystem automatically grabs the cine images to create astill image of the stent with enhanced edges and theassociated region of interest (Fig. 1). The software per-

forms automatic enhancement of stent’s visibility fad-ing out anatomical structures and background noise. Inthe current study the operator evaluated two separateenhanced-stent images using two different angiographicprojections at least 30� apart. Stent visibility wasassessed using both standard angiography and ESI.

The interventional cardiologists who performed theprocedures graded the quality of the ESI images from 1to 5 (1 ¼ low quality, 5 ¼ high quality). The degree thatESI contributed to the decision-making process was alsograded from 1 to 5 (1 ¼ not at all, 5 ¼ significantly),along with how easily this modality intergraded into theprocedure’s workflow (1 ¼ difficult, 5 ¼ easy).

Following the procedure, ESI diameter measurementswere obtained independent of and blinded to the QCAand IVUS measurements. Quantitative measurementswere performed by manual tracing of enhanced stentedges and algorithmic processing of denoted lines.Measurements were done at the edges and the middle ofthe stent. Stent diameters included minimum, maximumand mean (defined as the average of minimum andmaximum) stent diameters were calculated.

Quantitative Coronary Angiography

QCA analysis was performed using a validatedsemi-automated QCA software (QAngio XA version7.1.43.0, by MEDIS medical imaging systems Nether-lands). Frames for QCA analysis were selected fromfully-opacified angiograms that provided optimal visu-alization of the lesion/treated segment with the leastdegree of foreshortening. Calibration was performedwith the use of the contrast-filled guiding catheter asthe reference. Post-PCI diameters of the stentedsegments as well as the diameters at the proximal anddistal stent edges were obtained. QCA measurementswere obtained independent of and blinded to the ESIand IVUS measurements.

Intravascular Ultrasound Imaging and Analysis

The I-Lab or Galaxy (with Atlantis SR Pro, 40-MHzcatheters - Boston Scientific, Boston, MA) or S5 (with

Fig. 1. An enhanced stent image (ESI) is produced using theradiopaque markers of the delivery balloon from severalframes (minimum 20). The result is a still image of the stentwith enhanced edges.

2 Sanidas et al.

Catheterization and Cardiovascular Interventions DOI 10.1002/ccd.Published on behalf of The Society for Cardiovascular Angiography and Interventions (SCAI).

Revolution 45-MHz catheters - Volcano Therapeutics,Rancho Cordova, CA) IVUS systems were used. IVUSimaging was performed after intracoronary administra-tion of 100–200 lg nitroglycerin, using a motorizedtransducer pullback at 0.5 mm/sec. Images were continu-ously recorded throughout the stent, including >5 mmsegments distal and proximal to the stent. IVUS imageshad immediate interpretation for procedural decisionmaking by the operator, and additional off-line quantita-tive and qualitative analyses by IVUS core laboratory(Cardiovascular Research Foundation, New York, NY).Quantitative analysis was performed using validatedplanimetry software (EchoPlaque, INDEC Systems,Mountain View, CA). Grayscale IVUS external elasticmembrane (EEM), lumen, and stent borders were man-ually traced. Measurements of EEM, lumen, stent, pla-que and media (P&M, defined as EEM minus lumen)cross-sectional areas (CSA) and plaque burden (definedas P&M divided by EEM) were performed at the follow-ing locations: proximal and distal reference (defined asthe most normal looking areas within 5 mm of the proxi-mal and distal stent edge); the middle of the stent(exactly half distance of the total stent length), the MSAsite, and the proximal and distal stent edge sites (the firstframe with more than 75% of visible stent struts) [8].IVUS measurements were obtained independent of andblinded to the ESI and QCA measurements. IVUS exam-ination was performed in all patients and clinically usedfor decision making by the operator. Although IVUSwas performed in all 40 patients (42 stents), due to tech-nical issues nine IVUS studies were not analyzable; forthe specific off-line analysis needed for this study, IVUSwas available for only 31 stents.

Statistical Analysis

Categorical variables were summarized as absolutevalues and percentages. Continuous variables werepresented as means and standard deviations. IVUS meas-urements with or without postdilation were comparedusing the unpaired Student’s t-test. The correlationamong ESI, QCA, and IVUS measurements was eval-uated using linear regression analysis and the Bland-Alt-man formula [9,10]. Differences among ESI, QCA, andIVUS measurements were also compared using thepaired Student’s t-test. A P value <0.05 was consideredstatistically significant. All statistical analysis wasperformed using StatView 5.0 (SAS Institute, Cary, NC).

RESULTS

Patient Characteristics

Total of 40 patients were enrolled. Their mean agewas 62.2 � 9.2 years. Of them 30 patients (75%) were

men, and 15 (37.5%) were diabetics. Mean body massindex was 28.9 � 5.9 kg/m2. Thirty eight patients hadonly one lesion treated with only one stent per lesion;and two patients had two lesions treated, with one stentper lesion, located in two different coronary arteries.

Total of 42 native coronary arteries were treated: rightcoronary artery (n ¼ 13, 31%), left anterior descending(n ¼ 12, 28.6%), left circumflex (n ¼ 9, 21.4%), diagonalbranch (n¼ 3, 7.1%), obtuse marginal (n¼ 3, 7.1%), ramusintermedius (n¼ 1, 2.4%), and left main (n¼ 1, 2.4%).

Total of 42 stents (one stent per lesion) were placed;37 (88.1%) were everolimus-eluting stents. The overallstent diameter was 3.0 � 0.4 mm, and the stent lengthwas 17.5 � 6.5 mm. The baseline clinical, lesion, andstent characteristics of the cohort are outlined in Table I.

Postdilation Decisions Based on Angiography,ESI, and IVUS

The decision algorithm for stent postdilations issummarized in Fig. 2. Following stent deployment andbased solely on angiography, the operator decided topostdilate seven stents (7/42, 16.7%). This decisionwas not changed after reviewing the ESI images ofthese seven stents. Of the 35 stents not requiringpostdilation based on angiography alone, ESI imagesinfluenced the operator to change the decision andpostdilate 10 additional stents (10/35, 28.6%). Of these10 stents, IVUS imaging confirmed the postdilatationdecision in eight stents (8/10, 80%). Of the 25 patientsin whom angiography and ESI suggested no need foradditional postdilation, IVUS confirmed this decisionin 23 and changed the decision towards postdilatationin two. A case example is presented in Fig. 3.

ESI and IVUS Measurements of Stents thatNeeded Postdilation

Stents that needed postdilation based on ESIinterpretation had a statistically significant smaller ESIminimum stent diameter (MSD) than those who didnot need postdilation (2.2 � 0.3 mm vs. 2.6 � 0.4mm, P ¼ 0.0068; Table II).

According to IVUS measurements stents that neededpostdilation based on ESI interpretation had a statisti-cally significant smaller IVUS MSD than those whodid not need postdilation (2.0 � 0.3 mm vs. 2.5 � 0.5mm, P ¼ 0.008; Table II).

ESI Image Quality Evaluation by the Operator

In the majority of the cases, ESI image quality wasrated with the highest grade 5 (mean 4.4 � 0.9). StentOp-timizer was very easy to use and blended successfullyinto the procedure’s routine (mean 4.4 � 0.7). It

Enhanced Stent Imaging 3


contributed positively (mean 4.0 � 1.0) to the clinical de-cision for postdilation, based on operator evaluation.

ESI, QCA, and IVUS Measurements

In the 42 stents, ESI distal stent edge diameter was2.8 � 0.4 mm, proximal stent edge diameter was 2.9� 0.5 mm, and middle stent diameter was 2.8 � 0.4mm. The MSD measured 2.6 � 0.4 mm (Table III).

In the 42 stents QCA postintervention MSD measured2.2 � 0.5 mm. The distal stent edge stent diameter was2.8 � 0.5 mm, and the proximal stent edge diametermeasured 2.8 � 0.5 mm (Table III).

Off-line quantitative and qualitative IVUS analyseswere available in only 31 out of 40 patients (31 stents).The MSD was 2.5 � 0.5 mm; and the distal and proxi-mal stent edge diameters measured 2.8 � 0.5 mm and2.7 � 0.5 mm, respectively (Table III).

Comparisons Between ESI, QCA, and IVUS

The ESI-based measurements had better correlationwith IVUS (r ¼ 0.721, P < 0.0001) at the proximal

and distal stent edges, at the middle of the stent, and atthe MSA sites than did the QCA measurements corre-late with IVUS at proximal and distal stent edges andat the MSA sites (r ¼ 0.563, P < 0.0001). Particularlyat the MSA site, ESI showed even better correlationwith IVUS (r ¼ 0.741, P < 0.0001) than did QCAwith IVUS (r ¼ 0.509, P ¼ 0.0034; Table III).

Bland-Altman analysis tended to show better agree-ment of ESI with IVUS at proximal and distal stentedge, in the middle of the stent, and at the MSA sites,than did QCA with IVUS at the proximal and distalstent edge and at the MSA sites (mean differences ¼0.038 vs. 0.121; P ¼ 0.19, respectively; Fig. 4). Partic-ularly at the MSA site, Bland-Altman analysis alsotended to show better agreement of ESI with IVUSthan QCA with IVUS (mean differences ¼ 0.078 vs.0.271; P ¼ 0.14, respectively).

DISCUSSION

The current study investigated the use of enhancedstent imaging (ESI) as adjunct to angiography. The firstpart of the study examined the clinical use of ESI tohelp the decision whether stent-dilatation is needed.The second part of the study compared the ESI-basedmeasurements to commonly used QCA and IVUS meas-urements. The study demonstrated that ESI can beeasily integrated into the procedure flow, enhancesdigitally-acquired fluoroscopic images resulting inimproved stent visualization, and contributes to theprocedural decision-making. ESI contributed to thedecision-making whether balloon postdilatation isneeded. In 28.6% of the cases, ESI led the operator toperform a post dilatation, despite of a ‘‘satisfactoryangiographic result’’. The decision was confirmed by

TABLE I. Baseline Clinical, Lesion, and Stent Characteristics

Number of patients 40

Mean age (years) 64.2 � 9.2

Male gender 30 (75%)

Mean body mass index (kg/m2) 28.9 � 5.9

Risk factors

Hypertension 34 (85%)

Hyperlipidemia 27 (67.5%)

Diabetes mellitus 15 (37.5%)

Current smoker 19 (47.5%)

Indication for PCI procedure

Unstable angina 18 (45%)

Stable angina 13 (32.5%)

Positive stress test 9 (22.5%)

Medical history

Prior Coronary artery bypass graft 9 (22.5%)

Peripheral artery disease 5 (12.5%)

Treated coronary artery

Number of lesions treated 42

Right coronary artery 13 (31%)

Left anterior descending artery 12 (28.6%)

Left circumflex artery 9 (21.4%)

Diagonal branch 3 (7.1%)

Obtuse marginal 3 (7.1%)

Left main 1 (2.4%)

Ramus intermidius 1 (2.4%)

Stents

Number of stents implanted 42

Stent length, mm 17.5 � 6.5

Stent diameter, mm 3.0 � 0.4

Stent type

Everolimus eluting stents 37 (88.1%)

Paclitaxel eluting stents 2 (4.7%)

Sirolimus eluting stents 1 (2.4%)

Zotarolimus eluting stents 1 (2.4%)

Bare metal stents 1 (2.4%)

PSI, percutaneous coronary intervention.

Fig. 2. Flow chart showing how many stents were postdi-lated after implantation and which imaging modality amongangiography, ESI, and IVUS influenced the decision makingprocedure.

4 Sanidas et al.


IVUS in 80% of the cases. ESI also provides accuratemeasurements as compared with IVUS.

The development of image processing algorithms forX-ray based evaluation of coronary stents allows supe-rior visualization compared to standard images as hasbeen previously reported and validated [11]. TheStentOptimizer software produces the enhanced image

using the radiopaque markers of the delivery balloonas a reference for the stent edges. The same procedurecan be also used in case of two or more overlappingstents. In this study ESI assisted in the decision makingprocess for optimizing stent results by influencing thepost deployment treatment strategy in almost one-thirdof the cases. Additionally, ESI image quality was very

Fig. 3. A: Post stent angiography image of a left circumflex (LCX) lesion (arrow) with an ac-ceptable angiographic result. B: Angiographic stent image before StentOptimizer enhance-ment. C: Enhanced stent image by StentOptimizer showing underexpansion at the middlepart of the stent (arrow). D: IVUS image at the minimum stent diameter site and the IVUSminimum stent diameter (MSD) of 2.4 mm, which confirmed the ESI finding of underexpan-sion in the middle part of the stent within the pre-existing heavily calcified lesion.

TABLE II. Comparison of Stent Diameters Between Stents With or Without the Need of Postdilation Based on ESI and IVUS

ESI IVUS

Need for

postdilation

n ¼ 17/42 (stents)

No need for

postdilation

n ¼ 25/42 (stents) P value

Need for

postdilation

n ¼ 8/31 (stents)

No need for

postdilation

n ¼ 23/31 (stents) P value

Distal stent edge site, SD (mm) 2.7 � 0.4 2.8 � 0.5 0.56 2.5 � 0.5 2.9 � 0.5 0.12

Middle of the stent site, SD (mm) 2.5 � 0.4 2.8 � 0.4 0.49 2.4 � 0.5 2.8 � 0.5 0.05

Minimum stent diameter site (mm) 2.2 � 0.3 2.6 � 0.4 0.0068 2.0 � 0.3 2.5 � 0.5 0.008

Proximal stent edge site, SD (mm) 2.7 � 0.4 2.9 � 0.5 0.39 2.6 � 0.4 2.7 � 0.5 0.55

ESI, enhanced stent imaging; IVUS, intravascular ultrasound; SD, stent diameter.



high and the whole method was easily integrated withthe PCI procedure’s routine.

Although the inherent high spatial and temporal re-solution of modern flat-detector technology deliversexcellent angiographic results, image quality of smalland moving objects may be mediocre and lead to lowlevel of confidence. Coronary stent visualization hasparticularly become suboptimal with the on-goingreduction in stent strut thickness [12]. The highincidence of obesity, as noticed in this study cohort,further degrades image quality.

In clinical practice, adequate stent deployment has animportant effect on immediate and long-term results

after percutaneous coronary interventions. In particular,suboptimal or incomplete stent expansion is associatedwith increased restenosis, target vessel revascularizationrates and, especially with DES, predispose to stentthrombosis. Stent expansion of DES using current stentdelivery systems is frequently suboptimal. Adjunctiverepeat inflations with larger balloons or higher-pressureinflations are often necessary to improve the MSA andthe uniform volumetric stent expansion in the majorityof cases. Angiographically, the incidence of incompletestent deployment ranges from 20% to 30% of the cases,[13,14]. Correspondingly, in our cohort a 16.7% of thestents needed postdilation based solely on angiography.

TABLE III. Postintervention Measurements and Comparison Among QCA, IVUS, and ESI

QCA n ¼ 42/42

(stents)

IVUS n ¼ 31/31

(stents)

ESI n ¼ 42/42

(stents)

P value r

QCA versus

IVUS

ESI versus

IVUS

QCA versus

IVUS

ESI versus

IVUS

Distal stent edge site, SD (mm) 2.8 � 0.5 2.8 � 0.5 2.8 � 0.4 <0.0001 <0.0001 0.667 0.843

Middle of the stent site, SD (mm) N/A 2.8 � 0.5 2.8 � 0.4 N/A <0.0001 N/A 0.678

Minimum stent diameter site (mm) 2.2 � 0.5 2.5 � 0.5 2.6 � 0.4 0.0034 <0.0001 0.509 0.741

Proximal stent edge site, SD (mm) 2.8 � 0.5 2.7 � 0.5 2.9 � 0.5 0.0447 0.0002 0.363 0.618

All sites, mean SD (mm) 2.6 � 0.6 2.7 � 0.5 2.8 � 0.4 <0.0001 <0.0001 0.563 0.721

ESI, enhanced stent imaging; QCA, quantitative coronary angiography; IVUS, intravascular ultrasound; SD, stent diameter.

Fig. 4. A: Linear regression analysis scatter plot comparingESI and IVUS minimum stent diameters (MSD) at proximal anddistal stent edge, middle of the stent, and minimum stentarea (MSA) sites. B: Linear regression analysis scatter plotcomparing QCA and IVUS MSD at proximal and distal stentedge and minimum stent area (MSA) sites. C: Bland-Altman

plot for ESI and IVUS MSD at proximal and distal stent edge,middle of the stent and minimum stent area (MSA) sites.D: Bland-Altman plot for QCA and IVUS MSD at proximal anddistal stent edge and minimum stent area (MSA) sites. [Colorfigure can be viewed in the online issue, which is available atwileyonlinelibrary.com.]

6 Sanidas et al.


IVUS is more sensitive than plain angiography andQCA in determining stent expansion [15]; and the rou-tine use of IVUS results in improved stent expansion[16]. Clinical trials with BMS show a beneficial effectof IVUS in PCI, primarily by achieving better stentexpansion and larger acute lumen dimensions [16–18].Likewise, studies with DES and IVUS indicate thatstent expansion remains a clinically important predictorof both DES restenosis and thrombosis [5,6,19,20].Optimizing stent dimensions is mandatory especiallywhen risk factors for DES restenosis or thrombosis arepresent and/or when consequences of failure are signif-icant (i.e., unprotected left main lesions) [21,22].

Moreover, interventionalists routinely rely on manu-facturer supplied compliance charts to target final stentdimensions based on stent size and inflation pressure.These compliance charts are determined ex-vivo in airor in a water bath and do not take into account vesselstiffness, compliance, calcification, and atherosclerosis.A critical IVUS analysis showed that by using angio-graphic guidance alone stents achieved only 75% � 10%of predicted (by manufacturer compliance chart) MSDand 66% � 17% of predicted MSA and approximately25% of stents implanted into >3.0 mm vessels do notachieve an MSA >5.0 mm2. This is independent of stentmanufacturer, length, diameter, and deployment pressure[23]. However, there are considerations that limit theworld-wide routine use of IVUS. It is invasive, labor in-tensive, associated with radiation and contrast mediause, expensive, and not free of complications [24].

Limitations

This is a relatively small study designed to evaluatethe procedural decision about postdeployment dilata-tion not powered to evaluate the outcome of patients.The operator decision of his postdilatation strategy wasqualitative and not based on pre-defined criteria ormeasurements. Thus, this study evaluated the clinical-procedural use of ESI as a convenient decision-enhanc-ing tool integrated into the PCI procedure flow. Sec-ond, only single-stent treated lesions were evaluated.Overlapping stents and complex bifurcation lesionswere not studied. Third, lumen and stent diameterswere considered equal without taking into considera-tion strut thickness of the implanted stents.

CONCLUSIONS

Enhanced Stent Imaging with the StentOptimizer sys-tem is a novel angiographic based software whichenhances stent visualization. It was easily integrated intothe procedure flow and decision-making process follow-ing stent deployment. Stent diameter measurements

provided by ESI are reliable and correlate better thanQCA when compared with IVUS. When IVUS is notavailable or its use is questionable, ESI may be used forthe evaluation of stent expansion to help optimize stentdeployment by reducing rates of stent underexpansion.

ACKNOWLEDGEMENTS

This study was sponsored by a grant from Paieon Inc.The sponsor had no access to the raw data, and all theanalyses and manuscript writing and editing wereperformed by the authors. The authors thank Mr. DannyHarel from Paieon Inc. for his organizational supportand technical help.

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