FUNCTIONAL MRI OF THE PATELLOFEMORAL JOINT - COMPARISON OF ULTRAFAST MRI, MOTION-TRIGGERED CINE MRI AND STATIC MRI

In recent years ultrafast gradient echo sequences have been used in MR I that allow functional MRI studies of the joints during active motion in an acquisition time of seconds. To evaluate the feasibility and us efulnes of ultrafast MRI (u), patellar tracking from 30 degrees of fle xion to knee extension (0 degrees) was analysed and compared with moti on-triggered cine MRI (m) and a static MRI technique (s). The differen t imaging methods were compared in respect of the patellofemoral relat ionship, the examination time and image quality. Eight healthy subject s and four patients (in total 18 joints) with patellar subluxation or luxation were examined. Significant differences between the static MRI series without quadriceps contraction and the functional MRI studies (motion-triggered cine MRI and ultrafast MRI) were found for the patel lar tilt angle (PTA: P-m/s = 0.01; P-u/s < 0.01). In the dynamic joint studies there was no statistical difference of the regression coeffic ients between the motion-triggered cine MRI studies and the ultrafast MRI studies (P-m/u = 0.8). The findings of the functional MRI studies compared with the static MRI images were significantly different for t he lateralisation of the patella, expressed by the lateral patellar di splacement (LPD: P-m/s < 0.01; P-u/s = 0.01) and bisect offset (BSO: P -m/s = 0.01; P-u/s < 0.05). No significant differences in patellar lat eralisation were found between motion-triggered cine MRI and ultrafast MRI (LPD: P-m/u = 0.89; BSO: P-m/u = 0.33). Ultrafast MRI was superio r to motion-triggered cine MRI in terms of the reduction in imaging ti me and improvement of the image quality.