Page 18 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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                                Chapter 1
tissues like fat and water. As in CT, MRI is used to obtain slices through the human body in any desired direction. MRI has not only the 3d advantage for hand joint imaging, but it in contrast to previously mentioned methods it can also directly visualize the cartilage, synovium, tendons and ligaments (fig4) which are affected in RA and HOA.11-13 Because of its sensitivity to water, MRI shows increased water content in the bone marrow when this gets involved in RA and OA, and it is easier to see joint hydrops and synovial proliferation. Additionally gadolinium contrast can be injected intravenously, which will enhance areas with increased blood flow like inflamed synovium. Contrast enhanced MRI is the most sensitive imaging method to detect this increased blood flow, and therefore the most sensitive method to detect synovitis.
All these advantages of MRI, however, come with higher examination times, increased monetary costs, and not every patient is a good candidate for an MRI examination, as the magnetic field may disrupt electrical implants, and metallic implants in the region of interest distort the images.
Figure 4. Left: Single slice in the coronal plane of an MRI examination of two proximal phalanx including the MCP and PIP joints right: Sagital image of an MRI examination of a single MCP joint, depicting the cartilage layers as bands of high signal intensity (arrows) and clear depiction of the tendons as a structure of low signal intensity(asterisk).

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