Objectives: To determine the degree of contrast enhancement of normal TM joint (TMJ) in children and to provide reference data for patients with JIA.
Methods: A total of 100 dynamic contrast-enhanced MRI of 46 children from 1.6 to 18 years (median 9.1 years), who underwent the examinations for reasons other than TMJ disease, were retrospectively analysed in accordance with our local ethics committee. Time-intensity curves of the mandibular condyle and the soft tissue of the joint were assessed in relation to pre-contrast images and to muscle tissue.
Results: After contrast injection the soft tissue of all joints showed a rapid initial increase of signal intensity (SI) followed by a slow increase, with the maximum after 6 min (end of the scan). Maximum SI in the joint tissue was on average 73% higher than pre-contrast, 53% higher than in the condyle and 20% higher than in an adjacent muscle. However, in 15% of measurements post-contrast SI of the muscle was higher than that of the joint tissue. The enhancement curve of the bone marrow in the condyle showed a peak by 2 min post-contrast.
Conclusion: Contrast enhancement is a normal finding in the soft tissue and the condyle of the TMJ in children and adolescents. This should be taken into account when assessing the TMJ of children with JIA. As the relative enhancement of joint in comparison with muscle tissue proved to be variable, subtraction analysis of pre- and post-contrast T1 weighted images seems to provide a better basis for visual assessment.