High-resolution CINE imaging of active guided knee motion using continuously acquired golden-angle radial MRI and rotary sensor information

To explore and extend on dynamic imaging of joint motion, an MRI-safe device guiding knee motion with an attached rotary encoder was used in MRI measurements of multiple knee flexion-extension cycles using radial gradient echo imaging with the golden-angle as azimuthal angle increment. Reproducibility of knee motion was investigated. Real-time and CINE mode anatomical images were reconstructed for different knee flexion angles by synchronizing the encoder information with the MRI data, and performing flexion angle selective gating across multiple motion cycles. When investigating the influence of the rotation angle window width on reconstructed CINE images, it was found that angle windows between 0.5 degrees and 3 degrees exhibited acceptable image sharpness without suffering from significant motion-induced blurring. Furthermore, due to flexible retrospective image reconstruction afforded by the radial golden-angle imaging, the number of motion cycles included in the reconstruction could be retrospectively reduced to investigate the corresponding influence of acquisition time on image quality. Finally, motion reproducibility between motion cycles and accuracy of the flexion angle selective gating were sufficient to acquire whole-knee 3D dynamic imaging with a retrospectively gated 3D cone UTE sequence.

Automated summary

This study utilized an MRI-safe device guiding knee motion and a rotary encoder in the MRI measurements of multiple knee flexion-extension cycles. The reproducibility of knee motion was investigated. Real-time and CINE mode anatomical images were reconstructed for different knee flexion angles by synchronizing encoder information with MRI data and performing flexion angle selective gating across multiple motion cycles. It was found that angle windows between 0.5 degrees and 3 degrees exhibited acceptable image sharpness without significant motion-induced blurring. The flexible retrospective image reconstruction allowed for reduction in the number of motion cycles included in the reconstruction and investigation of the influence of acquisition time on image quality. This study demonstrated the ability to acquire whole-knee 3D dynamic imaging using a retrospectively gated 3D cone UTE sequence.