# Clinical Validation of a New Enhanced Stent Imaging Method  
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1 Department of Cardiology, University of Mons (UMONS), 7000 Mons, Belgium; [EMAIL_ADDRESS] (C.G.) claudiu-mih.ungureanu@jolimontbe (C.U. )1  
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2 Department of Cardiology, Military Hospital of Tunis, Tunis 1000, Tunisia; [EMAIL_ADDRESS]  
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3 Cardiology Department, Ziekenhuis Oost-Limburg, 3600 Genk, Belgium; [EMAIL_ADDRESS]  
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4 Cradiology Department, Hopital Jolimment, 7100 La Louviere, Belgium  
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5 Cardiology Department, Jessa Ziekenhuis, 3500 Hasselt, Belgium; [EMAIL_ADDRESS]  
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6 Faculty of Medicine, Free University of Brussels (ULB), 1050 Bruxelles, Belgium; [EMAIL_ADDRESS]  
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1 Department of Cardiology, University of Mons (UMONS), 7000 Mons, Belgium; [EMAIL_ADDRESS] (C.G.) claudiu-mih.ungureanu@jolimontbe (C.U. )1  
Footnote 25: email: email: c.daudiudue to the added time and cost to the procedure along with the image interpretation difficulties. Despite conventional angiography often falling behind in the detection of stent underexpansion and presenting a suboptimal accuracy assessing stent position, it is still carried out during routine clinical practice especially with newer generation scaffolds that are implanted at a higher pressure followed by a post-dilatation step and rely on the radiopaque nature of the material used for visualization. Thicker stent struts were associated with higher in-stant restenosis rates in the ISAR STEREO trials [18; 19]. On the other hand, thinner strut scaffolds used in new generation stents have been advocated to significantly reduce the risk of myocardial infarction at the expense of being more radiolucent on fluoroscopy [3; 20; 21; 22; 23]. Moreover, the trend towards the use of lower X-ray power during angiographic procedures presents another challenge for stent visualization which is further altered due to motion during the angiography sequence secondary to X-ray scattering. More recently, several enhanced stent imaging (ESI) methods have been developed. These angiography-based software improve stent visualization and provide quantitative as well as qualitative data post-stent deployment but remain dependent on the X-ray angiographic system of each vendor [24; 25]. The StentBoost(r) system (SB) (Philips Healthcare, Andover, MA, USA) is a motion-corrected X-ray stent visualization software that allows better assessment of stent expansion without using contrast [25]. It was designed as an add-on to conventional X-ray angiographic system and was found to be superior to conventional angiography in detecting stent underexpansion. The algorithm relies on the motion-compensated noise reduction by using landmarks (balloon markers) on 45 registered frames acquired over 3-4 s [26]. These images are transferred automatically to a workstation and corrected by averaging the images from each cine frame in relation to the two balloon markers. The software enhances stent visibility, fading out anatomical structures and background noise [25]. SB was found to have good correlation with IVUS regarding stent diameter and was found to be superior to quantitative coronary angiography (QCA) [14; 17; 24; 27; 28; 29; 30; 31]. Pie Medical Imaging (Maastricht, The Netherlands) introduced the CAAS StentEnhancer(r) (SE), a method similar to SB with the main advantage of being completely independent of the X-ray angiographic system of the vendor and hence, runs on a side station. SE uses a maximum of 40 frames from a Digital Imaging and Communications in Medicine (DICOM) file. Its algorithm automatically detects the markers of the stent balloon or of the balloon used for post-dilation in order to compute a single image in which the visibility of a deployed stent is improved. Following background subtraction, all frames are transformed into a common reference frame. The resulting images are combined into a single image after weighted averaging. A sharpening filter is then applied. This filter works by first extracting the high-frequency components from the image.