Imaging in early rheumatoid arthritis

Imaging in early rheumatoid arthritis (RA) has undergone extraordinary change in recent years and new techniques are now available to help the clinician diagnose and manage patients much more effectively than previously. While established modalities such as plain radiography (X-Ray) remain important, especially for detection of erosions and determining the progression of joint damage, there are many instances where ultrasound (US), magnetic resonance imaging (MRI) and computed tomography (CT) scanning provide added information. MRI and US are now used regularly by clinicians to help diagnose RA in the pre-radiographic stage as they offer improved visualisation of joint erosions. They also have the potential to provide prognostic information as MRI bone oedema/osteitis is linked to the later development of erosions and power Doppler ultrasound (PDUS) joint positivity is also a predictor of joint damage. Nuclear imaging techniques such as single photon emission computed tomography (SPECT) and positron emission tomography (PET) are also highly sensitive for detecting joint change in early RA and pre-RA but not yet used clinically mainly because of accessibility and radiation exposure. MRI, US, scintigraphy, SPECT and PET have all been shown to detect sub-clinical joint inflammation in patients in clinical remission, a state that is now the goal of most treat-to-target management strategies. Thus, imaging may be used to direct therapeutic decision making and MRI is also now being used in clinical trials to determine the impact of disease-suppressing therapy on the course of synovitis and osteitis. As is the case for all tests, it would be unwise to rely completely on any one imaging result, as false positives and negatives can occur for all modalities. Thus, the clinician needs to choose the most relevant and reliable imaging test, while also striving to minimise patient discomfort, radiation burden and economic impact.