Multimodality imaging of intraosseous ganglia of the wrist and their differential diagnosis.

Intraosseous ganglion (IOG) is the most frequently occurring bone lesion within the carpus and is often an incidental finding on radiographs obtained for other reasons. Two types of IOG have been described: an "idiopathic" form (or type I), the pathogenesis of which has not been completely clarified, and a "penetrating" form (or type II), caused by the intrusion of juxtacortical material (often a ganglion cyst of the dorsal soft tissue) into the cancellous bone compartment. The differential diagnosis for IOG is wide-ranging and complex, including lesions of posttraumatic (posttraumatic cystlike defects), degenerative (subchondral degenerative cysts), inflammatory [cystic rheumatoid arthritis, chronic tophaceous gout (CTG)], neoplastic (benign primary bone tumours and synovial proliferative lesions), ischaemic (Kienböck's disease or avascular osteonecrosis of the lunate) and metabolic (amyloidosis) origin. Multimodality imaging of IOGs is a useful diagnostic tool that provides complete morphological characterisation and differentiation from other intraosseous cystic abnormalities of the carpus. Thin-slice multidetector computed tomography (MDCT) can provide high-spatial-resolution images of the cortical and cancellous bone compartments, allowing detection of morphological findings helpful in characterising bone lesions, whereas magnetic resonance (MR) imaging can simultaneously visualise bone, articular surfaces, hyaline cartilage, fibrocartilage, capsules and ligaments, along with intra- and periarticular soft tissues.

Imaging studies of crystalline arthritides.

Gout, calcium pyrophosphate dihydrate (CPPD) deposition disease, and calcium hydroxyapatite deposition disease (HADD) are the three most common crystal-induced arthropathies. Multimodality imaging may help in their diagnosis, and is useful for a precise and comprehensive assessment and grading of the related osteoarticular damage. Plain film radiography, due to its low cost and wide availability, is the first imaging technique to be used in crystal deposition diseases, providing well-known and specific findings for CPPD deposition disease and HADD, while it may undergrade the early osteoarticular lesions in gouty patients. Ultrasonography (US) is a radiation-free approach that accurately depicts crystal deposits in cartilage, peri- and intra-articular soft tissues, but it does not give a panoramic view of the affected joints. Cross-sectional imaging techniques can examine crystal deposits in the spine and axial joints. CT has the potential to distinguish monosodium urate (MSU) crystals from calcium containing crystals, due to their different attenuation values. MRI may demonstrate synovitis, erosions and bone marrow edema in gouty patients and it may differentiate tophi from other soft tissue nodules due to its high contrast resolution and power of tissue characterization.

[Multimodality imaging of chronic tophaceous gout]. / Imaging integrato nella gotta cronica tofacea.

The diagnosis of gout is usually based on clinical presentation and laboratory findings. Imaging plays a role in the assessment and grading of articular damage related to chronic, long-standing disease, which is characterized by granulomatous synovitis, tophi, and erosions. Multimodality imaging of chronic tophaceous gout may be useful in clinical practice for a variety of purposes, including assessment of disease-related anatomical changes and monitoring of articular and soft-tissue lesions over time, especially in response to urate-lowering therapy. Radiography remains the primary imaging technique. Ultrasonography may detect monosodium urate crystals on cartilage, is helpful to assess small joint effusion, to guide to joint aspiration, and to evaluate the volume of tophi. Computed tomography is considered to be more sensitive than plain radiography in the detection and evaluation of cortical bone erosions associated with tophi. MRI represents the only imaging modality which provides visualization of bone marrow oedema associated with erosions and may be useful to characterize and distinguish tophi from other soft tissue nodules.