Assessing the accuracy and precision of musculoskeletal motion tracking using cine-PC MRI on a 3.0T platform

Abstract

The rising cost of musculoskeletal pathology, disease, and injury creates a pressing need for accurate and reliable methods to quantify 3D musculoskeletal motion, fostering a renewed interest in this area over the past few years. To date, cine-phase contrast (PC) MRI remains the only technique capable of non-invasively tracking in vivo 3D musculoskeletal motion during volitional activity, but current scan times are long on the 1.5T MR platform (∼ 2.5 min or 75 movement cycles). With the clinical availability of higher field strength magnets (3.0T) that have increased signal-to-noise ratios, it is likely that scan times can be reduced while improving accuracy. Therefore, the purpose of this study is to validate cine-PC MRI on a 3.0T platform, in terms of accuracy, precision, and subject-repeatability, and to determine if scan time could be minimized. On the 3.0T platform it is possible to limit scan time to 2 min, with sub-millimeter accuracy (<0.33 mm/0.97°), excellent technique precision (<0.18°), and strong subject-repeatability (<0.73 mm/1.10°). This represents reduction in imaging time by 25% (42 s), a 50% improvement in accuracy, and a 72% improvement in technique precision over the original 1.5T platform. Scan time can be reduced to 1 min (30 movement cycles), but the improvements in accuracy are not as large.

Figure 1

A. A fixed coordinate system within the MRI was established using three anatomical directions (Left, Anterior, and Superior). The motion phantom was aligned with the MRI’s axial plane (Left-Anterior) and moved such that all motion was confined to this plane. Thus, when a sagittal imaging plane (Superior-Anterior) was used, large out of plane motions occurred B. Based on high resolution cine images, the location of the four fiducials were visually tracked throughout the motion cycle. C. Next, an ROI, defined by a series of vertices, was tracked through integration of the cine-PC MRI data. D. Then these same vertices were tracked based on the kinematics derived through the visual tracking in B. E. Finally, the trajectories of the vertices from the two tracking methods (integration of the cine-PC data and visualization) were compared. The paths within the figure were derived by plotting the visual and integration tracking data.