The accuracy of spectral CT with quantitative parameters in differentiating septic from aseptic periprosthetic complications

OBJECTIVES: To explore the accuracy of spectral CT, using quantitative parameters, in differentiating septic from aseptic periprosthetic complications. MATERIALS AND METHODS: This study consecutively included patients with clinically suspected periprosthetic complications who underwent preoperative spectral CT and planned revision surgery between September 2020 and June 2024. Spectral quantitative parameters, including iodine concentration (IC), effective atomic number (Zeff), and normalized iodine concentration (NIC) on arterial and venous phases (AP, VP) for periprosthetic bone and soft tissue lesions were measured. Qualitative assessment of periprosthetic joint infection (PJI) was conducted by reviewing spectral CT images. The diagnostic performance of quantitative parameters for PJI was evaluated and compared to qualitative assessment. RESULTS: A total of 59 patients with 62 prostheses (mean age ± SD, 67.20 years ± 12.12; 26 men; septic group: aseptic group 26: 36 prostheses) were included. The IC-AP values were significantly higher in the septic group compared to the aseptic group across integrated and separate analyses of bone and soft tissue lesions (1.25 ± 0.59 vs. 0.50 ± 0.36; 1.58 ± 0.74 vs. 0.53 ± 0.37; and 1.10 ± 0.43 vs. 0.43 ± 0.32, respectively; all p < 0.001). IC-AP showed the highest diagnostic accuracy, with values of 84.3% (integrated), 90.7% (bone), and 89.6% (soft tissue). Other parameters also showed significant differences (all p ≤ 0.012) and good diagnostic performance. The diagnostic accuracy of qualitative assessment by the senior and junior radiologists, based on CT imaging features of PJI, was 82.3% and 75.8%, respectively. CONCLUSIONS: Spectral CT with quantitative parameters has the potential to improve the differentiation between septic and aseptic periprosthetic complications. CRITICAL RELEVANCE STATEMENT: Spectral CT may offer quantitative imaging biomarkers with the potential to improve visualization and identification of periprosthetic joint infections, particularly in complex cases and among less-experienced radiologists, thereby facilitating the clinical decision-making process. KEY POINTS: Accurate diagnosis of periprosthetic joint infection is crucial for treatment decisions. Quantitative parameters of spectral CT showed significant increases and high diagnostic accuracy in identifying septic periprosthetic complications. Spectral CT with quantitative parameters may serve as an imaging biomarker to enhance the clinical decision-making process.