MAGNETIC-RESONANCE IMAGINE OF THE TEMPOROMANDIBULAR-JOINT - VALUE OF PSEUDODYNAMIC IMAGES

Magnetic resonance fast scanning technique (gradient recalled acquisit ion at steady state) has been reported to be useful when evaluating th e dynamics of the temporomandibular joint and also to be accurate for determining the disk position. Yet in our clinical experience gradient reca;!led acquisition at steady state images have frequently been inf erior to proton density images for diagnosis of temporomandibular join t internal derangement. The first aim of this study was to compare gra dient recalled acquisition at steady state images with proton density images for diagnosis of disk position. The second aim was to identify what additional information could he gathered from gradient recalled a cquisition at steady state images when compared with static proton den sity images. We obtained unilateral images from 20 patients with sign; and symptoms of temporomandibular joint internal derangement and from 20 asymptomatic volunteers. Multiple gradient recalled acquisition at steady state images were obtained during mouth opening and closing an d proton density images were obtained at the closed and open mouth pos itions. The results showed that the gradient recalled acquisition at s teady state images were in accordance with the proton density images i n 32 joints (80%) and were false negative in 8 joints (20%). Six of th e joints with false-negative gradient recalled acquisition at steady s late images showed sideways disk displacement, and two showed partial anterior disk displacement. Gradient recalled acquisition at steady st ate images, on-the-other hand, provided information about movement pat tern and also demonstrated impingement of the joint structures on the muscles anterior to the joint at maximal mouth opening. It was conclud ed that gradient recalled acquisition at steady state images cannot re place proton density images for diagnosis of disk position but they ca n provide supplementary information for evaluation of joint function.