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The Impact of Ultrasound Imaging
In the field of Musculoskeletal Medicine
What is Musculoskeletal Ultrasound?
Ultrasound has been a big part of diagnostic medicine for the last 60 years. Well recognised for its use in Obstetrics (Field of Pregnancy) and now routinely used in general medicine, gynaecology, vascular and musculoskeletal medicine
Ultrasound is particularly useful at examining soft tissue and therefore lends itself well to musculoskeletal structures including fat, muscle, tendons, ligaments, cartilage, nerves, synovium, bursae and fluid.
Ultrasound excels at demonstrating the fine fibrillar/fibre strands of a tendon/ligament and thus effectively accentuates wear or tears.
The dynamic nature of ultrasound scanning provides a unique advantage in providing functional information regarding the movement and course of a structure such as a tendon, providing the practitioner with information such as areas of impingement (Pinching or trapping of structure), compression or scarring.
In some circumstances it is also particularly useful at assessing bone such as looking for occult/hidden fractures (Fractures not well visualised on plain X-rays) and monitoring fracture healing.
Lumps and bumps felt under the skin are another territory where ultrasound has been well utilised. Whilst it is not always possible to characterise the lesion on ultrasound, it can more than often provide essential information such as: location/origin, dimensions, shape, consistency, likely content, relationship to surrounding structures, vascular perfusion. Such information can at the very least give the well read practitioner a good level of confidence of whether this is benign, malignant or indeterminate and in need of further investigation.
How does it work?
Advantages of Ultrasound
The advantages of ultrasound in medical imaging are well documented:
- Considered a 'safe' imaging technique: Ultrasound does not have the associated risks of ionising radiation as seen in CT and plain X-rays. Nor does it use strong magnetic fields associated with MRI scanning, which is risky for those with types of implanted cardiac devices and other types of metallic prosthesis.
- Lower cost imaging: Compared to the alternate musculoskeletal imaging modality MRI, the cost of an ultrasound scan is typically much cheaper.
- Much more tolerable: It is no secret that patients often struggle with the claustrophobic, noisy confines of the typical MRI scanner for extended periods of time. In contrast, if you can tolerate a lick of cold ultrasound gel, you can tolerate an ultrasound scan.
Specifically relating to musculoskeletal medicine, ultrasound brings further unique advantages:
- Its Dynamic: Unlike any other method of imaging, ultrasound has the advantage of being able to easily assess the effect of movement or stress on a tendon, ligament, joint or muscle in 'real time'. Perfect for getting the answers if "it only hurts when I move like this" or "I can't move it past here".
- Its Interactive: You have the opportunity to actively participate in the scan, providing the operator with real time feedback of areas of maximum tenderness or certain movements that hurt. The Sonographers can also talk you through the scan and demonstrate features on the image such as tendons moving.
High resolution for soft tissues: Ultrasound is superior than CT and Xrays for soft tissue imaging and has now shown comparable and in some cases superior sensitivity for many musculoskeletal examinations. Click here for some peer reviewed examples
Advantages of Ultrasound
Advantages of Ultrasound
See the advantages of Musculoskeletal
What to expect during your visit?
- We will run through your referral. It's imperative that we can correlate any clinical findings, past medical/surgical history, previous imaging and any new signs/symptoms.
- As long as we can get to the area that needs to be scanned, you should not need to get changed for the examination.
However, its advisable to arrive in/with shorts for lower limb examinations and short sleeve t-shirts for upper limb. Shoulder examinations require us to expose the whole rotator cuff of the shoulder but dignity will be preserved at all times.
-A small amount of gel will be applied to the area being scanned. The ultrasound probe will be moved over the area and occasionally the joint will need to be moved to assess the joint in motion. The examination should not be painful however some discomfort should be expected if the area being scanned is already tender.
-Throughout the examination, the Sonographer will explain the anatomical features and findings, with a full detailed report provided for you to take away and where appropriate forward onto your referring clinician.
- Whilst the pertinent images will be included on the report, a digital copy of your images can happily be made available on request.
Without going into all the complexities of ultrasound physics, the fundamental concept is as follows:
1) The ultrasound probe/camera sends out high frequency ultrasound waves (higher frequency than is audible to the human ear) into the body
2) The sound waves propagate through different human tissues, some waves are reflected back towards the ultrasound probe/camera.
3) The reflected waves/echoes are received by the ultrasound probe/camera, converted into an electrical signal for the processor to interpret
4) The machine makes an assumption of the speed of ultrasound waves through tissue, 1540m/s (Although this is not constant so artefacts are commonplace, hence the clinician has to be highly qualified to establish what's real and what isn't)
5) So basically, the machine 'knows' how fast the wave is travelling and therefore depending on how long it took for the echo to return, the machine can calculate how deep the structure is which the reflected wave bounced off
6) The machine also detects how much energy/power is in the returning echo and can therefore decide how reflective/dense the structure was.
7) So the machine places a dot on the screen at the depth where the echo returned from and a shade of grey is assigned to that dot depending on how reflective that structure is (i.e. bone is more reflective than fat)
8) A picture/frame is then built up of hundreds of thousands of these dots, and each picture/frame is refreshed multiple times a second!! This gives us the unique 'real time' image.