Radiologic investigation of rheumatic diseases

A variety of imaging techniques is now available to investigate the child with rheumatic disease. Sonography and MRI, for example, are playing an increasing role in the evaluation of joint, tendon, and soft tissue inflammation or other abnormalities in children with rheumatic diseases. Imaging modalities offer the potential for earlier visualization and diagnosis of inflammatory abnormalities such as synovitis or cartilage damage along with improved assessment of therapeutic response. Each imaging modality has advantages and disadvantages when applied to selected anatomic regions and in imaging of children (Boxes 1, 2). These advantages and disadvantages must be understood before an appropriate investigative can be selected. To understand the imaging appearance of the growing joint, especially when using conventional radiography, one must recognize the significant postnatal development that occurs in the musculoskeletal system. In the newborn, there is extensive unossified epiphyseal cartilage that cannot be distinguished from adjacent soft tissues by conventional radiography. With increasing age, epiphyseal cartilage transforms to bone, narrowing the radiographic joint space to the thickness of the opposing layers of articular cartilage as seen in adolescence or adulthood. Normal articular soft tissue components are primarily of a similar radiographic density and cannot be clearly differentiated from each other or from adjacent muscles, fascia, tendons, ligaments, nerves, or vessels by conventional radiography. Displacement of fat deposits in fascial and intermuscular planes integrity of the cartilaginous tissue and quantitatively assess the degree of cartilaginous degeneration, as previously shown in the pediatric population [95].