Optimizing knee MRI near orthopedic hardware using a 3D-printed anatomical phantom

To evaluate whether a dedicated, anatomically realistic knee phantom with orthopedic implants can be used to optimize clinical MRI sequences under realistic metallic conditions and to assess whether phantom-optimized sequences improve image quality compared with routine protocols.

A 3D-printed knee phantom integrating a titanium screw and a stainless-steel fixation plate was developed. Phantom imaging was performed on a clinical 1.5 T MRI system. In this exploratory proof-of-concept study, T1w and STIR sequences were iteratively optimized using the phantom and compared with vendor-default and routine clinical protocols. The phantom-optimized sequences were subsequently applied in three asymptomatic volunteers with metallic knee implants and compared with routine sequences. Image quality was independently assessed by four blinded readers using a 5-point Likert scale across spatial resolution, artifact reduction, and overall image quality.

Phantom-optimized sequences achieved significantly higher image quality scores compared with routine protocols. Improvements were consistent across all three predefined criteria: spatial resolution (mean increase +0.70 points, p < 0.001), artifact reduction (+0.65, p < 0.001), and overall image quality (+0.78, p < 0.001). These gains were observed for both T1-weighted and STIR acquisitions without extending acquisition times.

Phantom-guided optimization provides a reproducible, patient-independent framework for tuning MRI protocols near orthopedic hardware. Anatomically realistic phantoms represent a promising methodological tool for developing, testing, and standardizing MRI sequences under controlled and clinically relevant conditions.