A preliminary study on the registration of MRI and cone beam CT images of temporomandibular joint disc

Objective: To evaluate the MRI and cone beam CT (CBCT) image registration methods of the temporomandibular joint (TMJ), and to explore the clinical application of the registered images and clinical diagnostic data for examining the relationship between the articular disc and condyle. Methods: Three patients with TMJ disc disposition were recruited at the Department of Oral and Maxillofacial Surgery, School of Stomatology, Wuhan University from January to March 2018. One patient was male, aged 30, and the others were females, aged 21 and 26 respectively. Three-dimensional (3D) images of CBCT and MRI of the TMJ were reconstructed and registered by using Mimics software. The images were then evaluated after the registration. The evaluation indicators selected were the area and volume of the articular disc, the position of the articular disc or the distance between the highest point of the condyle (point C) to the center point of the articular disc (point D), the distance between the last point of the joint disc (point P) to point C, as well as the angle between line CD and FH plane (∠DCF) at either opened- or closed-mouth condition. Results: The registration images of TMJ, at the closed- and opened-mouth positions of the 3 patients, showed the anatomical structures and interrelationships of the articular disc, articular nodules, joint fossa and condyle. Combined with clinical diagnosis, the difference of CD distances at the normal articular disc position was the minimum (1.94 mm), the difference of CD distances was small at the anterior disc displacement with non-reduction and larger with reduction. When the joint disc was in the opened-mouth position, ∠DCF angle was minimal (3.81°). The patients with anterior disc displacement with non-reduction showed the largest ∠DCF angle (48.03°). Conclusions: The position of the articular disc relative to the condyle and articular nodules, either at closed- or opened-mouth conditionds, could be accurately displayed after the image registration and fusion. The registration image not only could fully show the shape and position of the articular disc in different status from a 3D perspective, but also might provide basis for clinical study of TMJ disc displacement.