Detection of structural failure in bridging stent grafts: photon-counting CT versus dual-energy CT in a controlled in vitro study

BACKGROUND: Bridging stent grafts (BSG) are a critical component of fenestrated and branched endovascular aortic repair (f/bEVAR) but remain prone to structural failure due to continuous biomechanical stress. Early detection of stent wire fractures is clinically relevant, yet remains challenging with conventional computed tomography (CT) because of limited effective spatial resolution and metal-related blooming artifacts. The aim of the study is to evaluate whether photon-counting detector CT (PCCT) improves the detectability of structural defects in BSG compared with dual-energy CT (DECT). METHODS: An in vitro phantom model incorporating commercially available BSGs with predefined wire fractures was examined using PCCT and DECT across multiple Siemens IQ (dose/resolution) levels. Seven experienced human observers assessed defect visibility using a five-point Likert scale. Interobserver agreement was evaluated using Fleiss' kappa. Quantitative analysis was performed using relative full width at half maximum (FWHM) measurements, expressing defect width relative to stent diameter. RESULTS: PCCT demonstrated markedly superior visibility of stent fractures compared with DECT. Mean Likert scores were 4.66±0.43 for PCCT versus 2.56±0.62 for DECT (median 4.86 vs. 2.43; P<0.001). Ratings indicating good to excellent visibility (Likert 4-5) accounted for 94.7% of PCCT assessments but only 16.9% with DECT. Interobserver agreement was substantially higher for PCCT (κ=0.295) than for DECT (κ=0.004). Quantitative analysis revealed significantly larger relative FWHM values with PCCT (0.72±0.08) compared with DECT (0.60±0.12; P<0.001), consistent across stent types and IQ levels. PCCT achieved stable high detectability already at intermediate IQ levels, whereas DECT showed a gradual dose-dependent improvement. CONCLUSIONS: In this controlled experimental setting, PCCT substantially outperformed DECT in the detection of structural bridging stent graft failure, both in subjective and quantitative analyses. These findings suggest that structural BSG defects may be substantially underdetected with conventional CT and that PCCT enables a fundamentally improved level of detectability. This has potential implications for post-f/bEVAR surveillance and warrants further in vivo evaluation.