Quantifying synovial inflammation: Emerging imaging techniques

Table 1 Comparison of various non-invasive imaging techniques in assessment of synovial inflammation

Imaging technique forquantification of synovialinflammation	Advantages	Limitations
Radiography	Cost effective, Ease of access, Wide coverage of important joint regions, newer digitised formats that allow easy retrieval and comparison of images longitudinally and relative low cost	Exposure to ionising radiation, which although relatively low for one set of X-rays can cumulate over time with a potential impact on patient longevity Lack of sensitivity for detecting early joint damage and inability to image the inflammatory processes within the joint that precede damage Very little information regarding severity of inflammation Lacks quantifiable variables of inflammation in early arthritis
Ultrasonography	It is sensitive, cost effective, can be performed by the treating physician in out-patient-department basis, and can be repeated as desired for serial monitoring of inflammation	Normal anatomical structures may have low reflectivity and mimic synovitis if careful attention is not paid to technique, particularly with lower resolution equipment Operator dependent
Positron emission tomography	Sensitive, able to assess inflammation at molecular level Used for imaging sub-clinical synovitis because of their sensitivity and ability to capture many joints	Costly, Still experimental No evidences available in early synovitis. Not available at many centres and not being used in day to day clinical practices High radiation exposure
Computed tomography scanning	Cost effective Multidetector helical CT produces very high-quality images which can be stored in a digitised format and compared with later images to determine erosion progression Gold standard for imaging of bone erosions	Computed tomography scan upon whole body scanning leads to high dose radiation exposure It does provide less coverage than plain radiography as usually only one joint area is scanned
Magnetic resonance imaging	Sensitive techniques to assess soft tissue and bone changes in the joints Very sensitive for the detection of early synovial inflammation Diffusion Tensor based imaging can evaluate molecular event during synovial inflammation without contrast medium	Time consuming, Relatively costly Contrast based enhancement required for dynamic study