Page 15 - Imaging of Osteoarthritis and Rheumatoid Arthritis in Hand Joints
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 Use of radiological imaging methods 1 Radiological imaging methods are used to depict the current anatomical status
of joints. In clinical practice they can be used to help form a diagnosis, determine
the current amount of joint damage, help decision-making for treatment by determining if there is current inflammation, and compare with previous images
to determine progression. The radiological imaging methods are conventional radiology (CR), computed tomography (CT), magnetic resonance imaging (MRI) and ultrasound (US). They use different physical properties, resulting in each method having its own advantages and disadvantages and specific uses. A short description of the underlying mechanism of each technique follows below to aid the understanding of their specific uses in hand joints, so that we can discuss how they may improve earlier detection of disease and help in treatment-trials for RA and OA.
Conventional radiography
The radiological imaging methods originate from the year 1895, in which Wilhelm Conrad Röntgen discovered the existence of x-rays, and created the first radiograph: an image of the hand of his wife (fig 2a). This technique was soon used for medical imaging and is mostly called conventional radiography (CR). Over the years the technique improved significantly, but the fundamentals stayed the same. Electromagnetic radiation with a wavelength of approximately 0.01 to 0.1 nm is produced in an x-ray tube creating a stationary beam of x-rays, which is then passed through the human body. Part of the x-rays are scattered and absorbed by the human body, with dense structures like bone absorbing more x-rays then soft-tissues. The unaltered x-rays are received on a detector on the other side of the patient, creating an image (fig 2b). As bone can be well differentiated from soft-tissues with this method, it is mostly used in joint imaging to detect bony pathology. Usually x-rays from two different directions are made to get a sense of the 3-dimensional aspect.
If CR is used to image the early stages of osteoarthritis, findings are likely normal. The earliest visible signs on CR are small osteophytes and joint space narrowing (JSN), which is an indirect measure of cartilage destruction and can only be seen when a sufficient amount of cartilage is destroyed.8, 9 Later in the disease course the increase of density in the subchondral bone is seen as subchondral sclerosis, and subchondral cyst formation can be seen in
General introduction

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