Ultrasound (US) is one of the best imaging techniques in musculoskeletal radiology because it is low in cost, has high spatial resolution, wide availability in hospitals, is well-tolerated by patients and is not biologically invasive, as it uses sound waves and non ionizing radiation, as in conventional radiology or computed tomography (CT). These features make ultrasound the ideal technique for the diagnosis and follow up of many pathologies and rheumatic syndromes and for the evaluation of the effects of therapy.
The high diagnostic value of ultrasound is strictly related both to the operator's knowledge of normal anatomy and to the effectiveness of ultrasound equipment to depict anatomical details (Fig. 1.1 a-c).
For this reason, the equipment and transducers' characteristics become very important when studying small and superficial structures, such as flexor and extensor tendons in fingers, which are very difficult to assess with other imaging techniques because of their superficial location.
The most recent generation of ultrasound equipment allows highly detailed depiction of structures located just a few millimeters from the transducer.
New generation transducers may reach very high frequencies (up to 20 MHz), that allow the evaluation of submillimetric structures, such as tendon pulleys (Fig. 1.2).
The availability of new multifrequency probes allows the simultaneous study of both superficial and deep structures, granting a good penetration of ultrasound waves through the tissues.
Assistance can be given by a silicone spacer or by a thick layer of gel when using old equipment (e.g. transducers under 10 MHz frequency).
Musculoskeletal sonography should be per-
Evolution in the resolution capability of tendon fibrillar echo-texture. a Image obtained with ultrasound equipment from the early 90s: it is panoramic but has low spatial resolution. b Image obtained using ultrasound equipment from the late 90s with a good demonstration of the fibrillar echotexture. c Image obtained using the most recent generation of ultrasound equipment, showing great anatomical detail
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