Assessment of bone-implant interface image quality for in-vivo acetabular cup implants using photon-counting detector CT: Impact of tin pre-filtration.

PURPOSE

To assess the image quality of the bone-implant interface of acetabular cup implants using photon-counting detector (PCD) CT with and without tin pre-filtration in a clinical setting.

METHODS AND MATERIALS

Twenty-four patients underwent PCD-CT imaging of their total hip replacement (THR). Twelve patients were scanned using 140 kVp and twelve patients using 140 kVp with tin pre-filtration (Sn140 kVp). All scans were acquired with a collimation of 120 × 0.2 mm. The acquired data was reconstructed with different slice thickness (0.2 mm - 0.6 mm) and kernel (Qr) strengths (56, 76, 89) with and without metal artifact reduction (iMAR). Two observers assessed the image quality of the bone-implant interface for the cup based on four image quality criteria. Bone contrast, contrast-to-noise ratio (CNR) of bone/fat and cortical sharpness was performed as quantitative measures.

RESULTS

Image quality was rated highest for 0.2 mm slice thickness and Qr89 kernel across all four criteria for both the 140 kVp and Sn140 kVp by both observers, with a slight preference for the Sn140kVp over the 140 kVp. In all cases and for all image criteria the 0.2 mm/Qr89 was preferred above the Qr76 and Qr56/iMAR for both the 140 kVp and Sn140 kVp by both observers. Quantitative measurements confirmed significantly improved bone contrast as well as cortical sharpness using 0.2 mm/Qr89. Tin pre-filtration did not affect the CNR at 0.2 mm/Qr89 but tended to decrease cortical sharpness.

CONCLUSIONS

High resolution PCD-CT allows for in-vivo assessment of the bone-implant interface in patients with THR and is preferably acquired with tin pre-filtration.