Better sound and vision
Published on 01 January 2009
Ultrasound is playing an ever-bigger role in the diagnosis and treatment of inflammatory types of arthritis, as well as being used increasingly as a research tool. Expert Dr Richard Wakefield explains how it works and why this imaging tool is so important in examining joints and the surrounding soft tissue.
Ultrasound imaging has become an increasingly visible feature in UK rheumatology departments in recent years. In the 1990’s, improvements in technology allowed clearer images and better differentiation between different joint-related tissues. In addition, the cost of machines fell, making it a more affordable and accessible technology than MRI. One significant advantage of ultrasound is that it can be performed immediately in clinic providing instant information to the clinician and avoiding the need for a patient to return for a further appointment.
What is ultrasound and how does it work?
The technique uses supersonic waves which are emitted from a hand-held probe and penetrate the skin. These then bounce off structures in the body and are re-captured by the probe and converted into an image. To what extent they bounce back depends on the type of tissue – each tissue, such as bone, synovium (joint lining tissue), joint fluid, tendon, ligament, and fat, has a different density. Some structures transmit sound (for example fluid appears black) whilst other reflect it (bone appears white). There are two basic types of imaging: Grey scale and Doppler. Grey scale is what is meant by the black and white image and gives us information on the structure and amount of tissue. In contrast, Doppler gives us information about blood flow and may assist in the demonstration of active inflammation. Using both techniques gives us a unique insight into the development of musculoskeletal conditions and allows greater accuracy than just feeling and moving joints with our fingers - the standard method of assessing joints.
Why has ultrasound become popular?
In recent years it has become increasingly recognised that early identification and treatment of disease, in particular joint inflammation, can prevent joint damage and increase patients’ quality of life. In addition, new (but potentially toxic) therapies have driven a desire for more accurate diagnoses. Imaging techniques such as ultrasound may not only help with diagnosis but have the potential to help predict which patients will do badly (hence require stronger treatments), allow more accurate disease monitoring and allow direction of needles into joints.
Who can perform ultrasound?
Ultrasound can potentially be performed by any practitioner as long as they are adequately trained. Traditionally, the radiologist was the one who fulfilled this role but due to the fact that there is a preference to have the information at the time of clinical assessment, the clinicians themselves have begun to learn. As a result, it is now possible that such an investigation will be performed by your rheumatologist, sports physician, podiatrist, physiotherapist or clinical nurse specialist. This increase in demand has meant that the development of training has become even more important.
Why isn’t ultrasound provided in all hospitals?
One major reason for ultrasound not being provided in some hospitals is a lack of training facilities in the UK. This reflects the relatively few trainers and a current lack of infrastructure. Providing training is a costly and time consuming business. Another reason is a lack of expertise amongst clinicians as it is still a relatively new technique in the UK. Additionally, there is a general lack of musculoskeletal radiologists in the UK and in particular ones who are trained at looking for signs of inflammation, which is what rheumatologists particularly want. Currently most musculoskeletal ultrasound imaging is performed in teaching hospitals but it is likely that this will change over time.
Researchers and medics in Leeds have been actively investigating the role of ultrasound for the management of arthritis since 1997. It was one of the first centres in the UK and Europe to establish a dedicated ultrasound unit within a rheumatology department. There are two main strands to our work in Leeds - clinical research and training and education.
I joined the Academic Section of Musculoskeletal Disease in Leeds as a research fellow in 1997 and now lead the ultrasound research within the department, developing the technique with Professor Paul Emery and the musculoskeletal radiologists. At that time, there were no guidelines to follow. As ultrasound was such a new tool much work had to be done in order to validate it, (ie provide what we were seeing represented true picture of what was happening in the joint.) This meant comparing it with other imaging methods (like MRI) and tissue samples and testing its reliability. As a result, the group has made important contributions to the field by demonstrating the accuracy of the tool for detecting synovitis, tendon disease and bone damage in a number of joints such as the hand, knees and feet. This work was fundamental to the development of the first international consensus-derived pathological definitions of US detected pathology which the Leeds group has led. Further work with European and American researchers is currently underway to develop guidelines for acquiring and reading images.
How ultrasound is helping patients
One of the great strengths of the Leeds group has been the application of ultrasound in clinical practice. Much work has focussed on the better characterisation of early inflammatory disease. We have uniquely demonstrated that ultrasound can be used to detect inflammation not found on clinical examination (so called subclinical disease) such that it might change a specific diagnosis, for example, demonstrating that diagnoses may change in up to 50 per cent of patients after using ultrasound. Recently, we have also shown that ultrasound may be helpful in predicting which patients will go on to have a more serious disease. Our group has recently investigated the role of imaging of arthritis patients’ joints in remission. They have shown that ultrasound and MRI continue to show signs of inflammation in many patients even when they feel well. This implies that treatments should not be immediately stopped even if the examination or blood tests are normal.
Further clinical research
Much of our original work has concentrated on rheumatoid arthritis but work has also been done in collaboration with Professor Philip Conaghan and Dr Helen Keen in osteoarthritis and Professor Dennis McGonagle and Dr Ai Lynn Tan in spondyloarthropathies (such as psoriatic arthritis and ankylosing spondylitis). The team has also successfully collaborated with the academic podiatry department through Arthritis Research UK senior lecturer Dr Tony Redmond and Arthritis Research UK PhD fellow Heidi Siddle. As a result we have set up an inter-disciplinary group to allow better clarification of disease processes in the foot and potentially more tailored management plans.
Another important area that the group has recognised as important is the development of a training programme for aspiring rheumatology sonographers. My colleague Dr Andrew Brown, through an Arthritis Research UK educational fellowship, developed the first ever consensus-derived curriculum which will become a standard to work by. These have been influential in the formation of UK and European training guidelines. Further work is currently planned to develop future teaching strategies.
Arthritis Research UK has recently given an equipment grant for a new ‘state of the art’ ultrasound machine. This will enable our group to continue in their scientific work across a number of projects and provide further opportunities for training. We hope that ultrasound will further improve our understanding of early disease processes and the potential methods by which the disease processes will be managed. High quality research using state of the art ultrasound equipment will encourage the refinement and provision of improved clinical care for patients with a variety of musculoskeletal disorders.
Dr Richard Wakefield is a senior lecturer in rheumatology in the Academic Section of Musculoskeletal Disease at Leeds University