dxparaspinalus3

Ultrasonography is sensitive in the detection of incomplete soft tissue injuries (56-60). Bonica states "Because CT scans and myelograms are usually negative they should not be considered unless evidence of a neurologic problem is found" (62). While intravenous Godolinium contrasted STIR MRI offers a sensitive method of evaluating soft tissue injuries (63), this option is not always a suitable tool for the clinician who wishes to evaluate paraspinal soft tissue pain; utrasonography is a reasonable alternative.

4. Pitfalls:

As with other imaging procedures, proper instrumentation must be utilizedfor diagnostic musculoskeletal ultrasonography. Echoes are produced at the junction or interface of tissues of

different acoustic impedances. Theseechoes return to the transducer only if the sound beam strikes the interfaceperpendicularly - otherwise they are reflected away from the transducer and are not recorded on the face of the cathode ray tube (64,65).

Experienced sonographers should continually attempt to direct the sound beam at an angle perpendicular to the structures being examined. In the case of diagnostic musculoskeletal ultrasonography for paraspinal structures, deeper structures are frequently of interest. The signals reflected from the posterior interfaces of the body are of low amplitude in comparison to more anterior echoes. This is due to signal attenuation secondary to reflection, absorption and dissipation (64,65).

Time gain control mechanisms are incorporated into all ultrasound equipment to provide progressive amplification of echoes in the depth of the interface. As greater emphasis is pon deeper structures, these control knobs should be