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Non-invasive evaluation of soft-plaque-restenosis in coronary artery stents

Philips CT Clinical Science Philips Healthcare • USA

Initial in-vitro comparison of a spectral photon counting CT and a spectral dual layer CT system

Tilman Hickethier, MD

Department for Diagnostic and Interventional Radiology

University Hospital Cologne

Kerpener Street 62

50935 Cologne




Even when compared to the latest Spectral dual layer CT systems (SDLCT) future Spectral photon counting detector CT systems (SPCCT) promise an improved spatial resolution as well as decreased stent related blooming artifacts, two likely beneficial characteristics for the challenging task of evaluating in-stent restenosis. Therefore, we investigated the influence of different conventional (Conv) and monoenergetic (MonoE) reconstructions from a SDLCT and a SPCCT on the delineation of soft-plaque-restenosis in coronary stents.


Method and Materials

Artificial stenosis (~30HU) were implanted into 10 different coronary stents (diameter 3mm) embedded in plastic tubes filled with Iohexol-based contrast agent (~400HU). CT data was acquired with a 128-slice SDLCT (IQon Spectral CT, Philips, 120 kV, 100 mAs, 0.2 x 0.2 x 0.67 mm³ voxel size (VS)) and a 9-slice SPCCT (Prototype, Philips, 120 kV, 100 mAs, 0.2 x 0.2 x 0.25 mm³ VS). Sharp FBP kernels were used for reconstructions with Conv and MonoE at 50, 70, 100 and 140 keV. Visibility of the stenosis and the remaining lumen was evaluated by two readers for each stent and reconstruction using a 5-point Likert scale:

  1. Image quality impedes lumen assessment
  2. Lumen appears stenosed, extent unclear
  3. Stenosis and extent clear, remaining lumen undistinguishable
  4. Stenosis clear and remaining lumen slightly distinguishable
  5. Stenosis and remaining lumen clear



Interrater agreement was very good (weighted kappa=0.9). Stenosis delineation was best in Conv, 50 and 70 keV MonoE SPCCT images (median score 5). Differentiation was significantly more difficult in the corresponding SDLCT images (median score 3; p<0.01). Despite visibly lower stent blooming artifacts, 100 and 140 keV MonoE images showed significantly poorer results compared to the corresponding 50 keV MonoE images due to reduced contrast enhancement resulting in impaired visualization of the unaltered stent lumen (median score of 2 for 100 keV and 1 for 140 keV on both scanners; p<0.01).



Evaluation of soft-plaque-restenosis can be significantly improved by using conventional and low keV MonoE reconstructions of future SPCCT. High keV MonoE reconstructions are not recommended for coronary stent assessment with SPCCT or SDLCT due to impeded stenosis delineation.


Clinical Relevance/Application

SPCCT will have the potential to significantly improve the important but still challenging non-invasive evaluation of coronary stents and possible restenosis.


Stainless steel stent (Coroflex Please, Braun, diameter 3.0 mm, length 19 mm, strut thickness 0.12 mm) with artificial soft-plaquerestenosis scanned with a SPCCT (A) and a SDLCT (B). Images were reconstructed with FBP (1) and MonoE at 50 (2), 70 (3), 100 (4) and 140 (5) keV. Window-settings were 330/1650 (C/W) for 50 keV SPCCT (A2) and 600/3000 for 50 keV SDLCT (B2) due to increased attenuation and 300/1500 for all other images. Best delineation eligibility was rated for FBP as well as 50 and 70 keV MonoE images from SPCCT (A1, A2, A3).

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Oct 31, 2017

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IntelliSpace Portal, IQon Spectral CT
13th MDCT Users Meeting abstracts, artifacts, Cardiac, coronary arteries, image quality, MonoE, plaque, spectral CT, stenosis, stent, Vascular

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