Conventional Radiology in Crystal Arthritis: Gout, Calcium Pyrophosphate Deposition, and Basic Calcium Phosphate Crystals

Imaging of Rheumatic Diseases Affecting the Lower Limb

Imaging methods capable of detecting inflammation, such as MR imaging and ultrasound, are of paramount importance in rheumatic disease management, not only for diagnostic purposes but also for monitoring disease activity and treatment response. However, more advanced stages of arthritis, characterized by findings of cumulative structural damage, have traditionally been accomplished by radiographs and computed tomography. The purpose of this review is to provide an overview of imaging of some of the most prevalent inflammatory rheumatic diseases affecting the lower limb (osteoarthritis, rheumatoid arthritis, and gout) and up-to-date recommendations regarding imaging diagnostic workup.

Selective pyrophosphate detection via metal complexes

Pyrophosphate (PPi) anions are crucial in numerous biological and ecological processes involved in energy conversion, enzymatic reactions, and metabolic regulation along with adenosine. They are also significant biological markers for various processes related to diseases. Fluorescent PPi sensors would enable visual and/or biological detection in convenient settings. However, the current availability of commercial sensors has been limited to costly enzymes that are not compatible for imaging. Sensor development has also encountered challenges such as poor selectivity and stability, and limited practical applications. In this review, we analyze the situation of PPi sensing via commercial kits and focus on sensors that use metal complexes. We address their designs, sensing mechanisms, selectivities and detection limits. Finally, we discuss limitations and perspectives for PPi detection and imaging.

Dual-Energy Computed Tomography (DECT) Resolves the Diagnostic Dilemma in an Atypically Presenting Case of Gout

Gout is a common inflammatory arthropathy that presents as acute monoarthritis, most commonly of the first metatarsophalangeal (MTP) joint. Chronic polyarticular involvement may lead to confusion with other inflammatory arthropathies, including rheumatoid arthritis (RA). A thorough history, physical examination, synovial fluid analysis, and imaging are keys to establishing a correct diagnosis. Although a synovial fluid analysis remains the gold standard, the affected joints may be difficult to access by arthrocentesis. In cases where a large monosodium urate (MSU) crystal deposition is in the soft tissues - the ligaments, bursae, and tendons, it becomes a clinical impossibility. In such cases, dual-energy computed tomography (DECT) can assist in differentiating gout from other inflammatory arthropathies, including RA. Additionally, DECT can perform quantitative analysis of tophaceous deposits and, therefore, assess response to treatment.

Imaging of Rheumatic Diseases Affecting the Lower Limb

Imaging methods capable of detecting inflammation, such as MR imaging and ultrasound, are of paramount importance in rheumatic disease management, not only for diagnostic purposes but also for monitoring disease activity and treatment response. However, more advanced stages of arthritis, characterized by findings of cumulative structural damage, have traditionally been accomplished by radiographs and computed tomography. The purpose of this review is to provide an overview of imaging of some of the most prevalent inflammatory rheumatic diseases affecting the lower limb (osteoarthritis, rheumatoid arthritis, and gout) and up-to-date recommendations regarding imaging diagnostic workup.

Radiographic Findings of Inflammatory Arthritis and Mimics in the Hands

Clinical presentation could be challenging in patients with arthralgia, and imaging plays an important role in the evaluation of these patients to make the diagnosis or narrow the differential diagnosis. Radiography of the hands is a commonly available imaging modality that can provide crucial information with regard to the pattern and pathology of the involved joints. It is important that radiologists and rheumatologists are familiar with the imaging findings of different rheumatic diseases to make the diagnosis in the early stages of disease to initiate treatment.

Imaging of Crystal Disorders:: Calcium Pyrophosphate Dihydrate Crystal Deposition Disease, Calcium Hydroxyapatite Crystal Deposition Disease and Gout Pathophysiology, Imaging, and Diagnosis

Crystal arthropathies are a group of joint disorders due to deposition of crystals in and around joints that lead to joint destruction and soft tissue masses. Clinical presentation is variable and diagnosis might be challenging. In this article the pathophysiology is addressed, the preferred deposition of crystal arthropathies and imaging findings. Case studies of calcium pyrophosphate dihydrate crystal deposition disease, hydroxyapatite crystal deposition disease, and gout are shown. Guidelines for the use of dual-energy computed tomography are given to enable the diagnosis and follow-up of gout.

A Systematic Approach to Diagnosing Arthritis Based on Radiological Imaging

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Radiology plays key roles in diagnosis of arthritis. We herein suggest an algorithmic approach to diagnosing arthritis. First, the number of joint involvements is reviewed. Monoarticular arthritis includes septic arthritis, pigmented villonodular synovitis, and synovial chondromatosis. Second, polyarticular arthritis can be categorized by its characteristics: erosive, productive and mixed. Erosive disease includes rheumatoid arthritis, hemophilia, and amyloidosis while productive disease includes osteoarthritis, and hemochromatosis. Third, mixed diseases are subcategorized by symmetricity. Ankylosing spondylitis and inflammatory bowel disease related arthritis affect joints symmetrically while psoriatic arthritis, reactive arthritis, and crystalline arthropathy are asymmetric. Adjacent soft tissue density, periostitis, and bone density are ancillary findings that can be used as additional differential diagnostic clues. The final step in identifying the type of arthritis is to check whether the location is a site frequently affected by one particular disease over another. This systematic approach would be helpful for radiologist to diagnose arthritis.

Periarticular calcifications

Periarticular calcification and ossification is a frequent finding on imaging and may sometimes pose a diagnostic challenge. The differential diagnoses for this radiological finding are wide and can be classified into broad groups such as idiopathic, developmental, trauma, burns, infection, tumor, connective tissue disease, crystalline, metabolic, vascular, and foreign bodies. With careful consideration of the clinical and imaging findings as well as awareness of mimickers of periarticular mineralization, the list of differential diagnoses can be narrowed down. This article aims to review the clinical-radiologic findings of periarticular calcified or ossified lesions with relevant imaging illustrations.

Osteoid osteoma: the great mimicker

Osteoid osteoma is a painful, benign and common bone tumor that is prevalent in young adults. The typical clinical presentation consists of pain that becomes worse at night and is relieved by nonsteroidal anti-inflammatory drugs. The most common imaging finding is a lytic lesion, known as a nidus, with variable intralesional mineralization, accompanied by bone sclerosis, cortical thickening and surrounding bone marrow edema, as well as marked enhancement with intravenous contrast injection. When the lesion is located in typical locations (intracortical bone and the diaphyses of long bones), both characteristic clinical and radiological features are diagnostic. However, osteoid osteoma is a multifaceted pathology that can have unusual presentations, such as intraarticular osteoid osteoma, epiphyseal location, lesions at the extremities and multicentric nidi, and frequently present atypical clinical and radiological manifestations. In addition, many conditions may mimic osteoid osteoma and vice versa, leading to misdiagnosis. Therefore, it is essential to understand these musculoskeletal diseases and their imaging findings to increase diagnostic accuracy, enable early treatment and prevent poor prognosis.

Imaging of Joints and Bones in Autoinflammation

Autoinflammatory disorders are commonly characterized by seemingly unprovoked systemic inflammation mainly driven by cells and cytokines of the innate immune system. In many disorders on this spectrum, joint and bone involvement may be observed and imaging of these manifestations can provide essential diagnostic information. This review aimed to provide a comprehensive overview of the imaging characteristics for major diseases and disease groups on the autoinflammatory spectrum, including familial Mediterranean fever (FMF), Behçet disease (BD), crystal deposition diseases (including gout), adult-onset Still's disease (AoSD), and syndromatic synovitis, acne, pustulosis, hyperostosis, and osteitis (SAPHO)/chronic recurrent multifocal osteomyelitis (CRMO). Herein, we discuss common and distinguishing imaging characteristics, phenotypical overlaps with related diseases, and promising fields of future research.

Radiographic/MR Imaging Correlation of Soft Tissues

MR imaging is nowadays regarded as the preferred imaging modality for evaluation of soft tissue lesions. As plain radiographs are often the first step in evaluation of musculoskeletal disorders, identification of subtle soft tissue signs may be helpful to select patients who need to be referred for subsequent MR imaging. Although not very sensitive, certain plain film findings, such as intralesional calcification or gas, may allow one to make to a more specific tissue diagnosis and may obviate the need for invasive diagnostic procedures and potential harmful treatment.