ULTRASOUND

practers are among some clinicians who are embracing this technology.

BRIEF HISTORY High frequency ‘ultrasound’ was first dis- covered in 1794 by Spallanzani, an Italian biologist; he demonstrated that the ability of bats to navigate accurately in the dark was through echo reflection from high fre- quency inaudible sound. The real break- through in the evolution of high frequency echo-sounding techniques came when the piezo-electric effect was discovered by the Curie brothers Pierre and Jacques, in Paris, France in 1880. This phenomenon is still used today in the manufacture of modern hi-tech ultrasound probes.

In the 1950s, Dr John Wild (a Cambridge- trained surgeon who emigrated to America) collaborated in Minnesota with scientific colleagues to develop the first crude but useful ultrasound images of bowel tissue, noticing that abnormal tissue had a higher echo signal than healthy tissue.

This led

to a landmark paper published in 1956 reporting on the use a 15MHz probe to help diagnose superficial breast tumours (4). In the audience of one of Wild's 1954 lectures was a Professor Ian Donald. Donald had developed an amateur interest in gadgets during his time with the RAF in World War II.

Four years later, and with

the help of basic industrial ultrasound equipment originally designed to detect metal flaws, Donald was credited with another seminal (and historically famous) medical paper that showed pulsed ultra- sound's use in the diagnosis of gynaeco- logical tumours (5).

One of the first papers on the use of ultra- sound in superficial (musculoskeletal) tis- sues was by Dussik in 1958 (6). MacDonald then reported on scanning Bakers Cysts in 1972 (7) and in 1978 ultrasound was shown to demonstrate synovitis of the knee (8). However, despite the work of these enthu- siasts, over the next 30 years muscu- loskeletal ultrasound (MSKUS) largely failed to exist as a serious medical subject, not aided by the advent of MRI in the 1980s.

Eventually the first widely recognised mod- ern 'bible' of musculoskeletal ultrasound was published in 1991 by Van Holsbeek (9) and the second edition of this textbook is still one of the standard reference resources for common musculoskeletal pathologies and teaching courses.

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Display – shows a detailed image of the inside of the body for analysis and diagnosis

THE PROS AND CONS OF MUSCULOSKELETAL ULTRASOUND Advantages Essentially ultrasound is relatively cheap (especially compared to MRI), quick to per- form and allow imaging dynamically

as

well as allowing rapid comparison with the same structure on the contra-lateral side. MSKUS also allows the patient to be inter- active; in many cases it is invaluable for the patient to be able to literally point to the area of most concern. Images can be reported in real time.

Ultrasound is safe and free from ionising radiation. 'MRI claustrophobia' is reported to affect between 5-10% of MRI scans patients (10); in these case ultrasound can be an attractive alternative, assuming that the lesion is suitable for examination by ultrasound. Interventions can be ultra- sound guided. Newer type machines also

Finally, if the MSKUS scanner possesses a Power Doppler facility, then additional information can be gleaned about the absence or presence of very subtle blood flow in new vessels in tendons or soft tis- sue masses (neovascularisation).

Finally, when MSKUS is used by clinicians (rather than as a pure diagnostic tool by radiologists/radiographers) it can stren- gthen the clinician-patient relationship. In turn, objective US evidence of the diagno- sis should serve to enhance shared under- standing of the injury and compliance with ongoing treatment and rehabilitation strategies.

allow the scanner to sweep over an extend- ed area and 'memorise' the images, so cre- ating an extended view. This is very useful in being able to measure large muscle tears, lumps or tendon lesions, also giving some anatomical perspective.

CPU – sends electrical impulses to the Probe that are converted to soundwaves, the recievs the reflected soundwaves back from the Probe and converts them into an image for display

Elpac Power Supply - Synchronised to the operating frequency of the CPU so no image degrading interference is generated

Probe – emits soundwaves into the body that are reflected back and sent to the CPU for image processing

injured tissue

A schematic diagram of a typical basic ultrasound circuit. Probe frequency in nor- mally in the range of 3-17MHz. The lower frequency probes (3-8MHz) penetrates tissue better to visualise deeper areas such as the hip. The higher frequencies (10- 17MHz) give better resolution, but struggle to image beyond 4-5 cm depths due to attenuation (essentially this is deterioration of the image signal strength as the ultrasound beam passes deeper and deeper into the body (black arrows) losing energy as it penetrates and then is reflected back (blue arrows).

Figure 2: A schematic overview of the main elements of ultrasound equipment sportex medicine 2007:33(Jul):20-26