ROLE OF MRI VERSUS US IN ASSESSMENT OF SKELETAL EFFECTS OF RHEUMATOID ARTHRITIS

Abstract

RA is a heterogeneous disease of unknown cause, disputed origin and variable clinical presentations. Its prevalence and incidence vary from one population to another and from time to time. In individual patients, it takes a variable course with remissions and exacerbations, and has a variable outcome, from a remitting disease leaving no damage to a severe disease bringing disability and even death.

The ability to directly visualize important joint structures coupled with high sensitivity in detecting pathology early in the course of joint disease are the reasons why US and MRI are particularly well suited for RA joint evaluation.

US can detect synovitis by demonstrating effusion, Synovial hypertrophy and power Doppler signal. It is particularly good at dynamic tendon assessments and can detect tenosynovitis and tendon rupture. It has a relatively lower operating cost, no ionizing radiation and allows multiple joints to be assessed in a multi-planar, dynamic and interactive manner over a reasonably short time span. It can also be used to guide invasive joint procedures. Its main disadvantages include its inability to look below the bony cortex and inaccessibility to certain sites due to lack of acoustic window. Moreover, US is operator dependent and requires a significant period of training before reaching competency.

MRI is capable of directly visualizing all structures seen by US. Additionally, it visualizes bone marrow pathologies not seen by US, especially bone marrow oedema. MRI also avoids ionizing ra