I am a state-registered clinical scientist (BSc Physics Birmingham 1991, MSc Medical Physics with Electronics London 1995) providing the physiological measurement service to the Rheumatology department at the Royal Free Hospital, where we investigate the microvascular aspects of scleroderma.
I am an associate member of the Institute of Physics and Engineering in Medicine (IPEM), and currently acting representative for the medical section on the committee of the United Kingdom Thermography Association (UKTA). I have published over 10 peer-reviewed papers, and presented work in both Britain and mainland Europe.
In the microvasvular lab. the degree of vasospasm suffered by our Raynaud's phenomenon patients is assessed by a cold challenge of the hands in water followed by measurement of finger temperature recovery using a thermal imager. This process is known as thermography . In addition, video capillary microscopy allows us to visualise the tiny blood vessels of the finger nailfold. These vessels are commonly enlarged or reduced in number in connective tissue diseases such as scleroderma. The laboratory is also active in the development of other vascular measurement techniques for clinical research, such as laser-Doppler flowmetry .
Capillaroscopy
This technique comprises the study of the nailfold capillary bed using television microscopy. The images are video recorded so that the capillaries may be studied and graded for damage at a later stage. The microcirculation is easier to see under the microscope if a thin layer of oil or clear nail polish is painted over the nailfold beforehand. An ophthalmoscope may be used if a microscope is not available.
Signs of microangiopathy include:
* Enlargement of capillaries, most obviously in the row nearest the nail. This damage is not in all loops; loops of normal size still dominate in most patients. * Loss of capillaries from the nailbed. In addition, one may sometimes see: loops which are more tortuous (bushy) than normal * Extravasation, i.e. the appearance of blood outside of the capillary lumens. In primary Raynaud's phenomenon, the capillaries are commonly normal in size and number. In secondary Raynaud's phenomenon, however, microangiopathy is often seen. This provides the Unit with a powerful yet simple technique for early disease diagnosis, which complements clinical and immunological findings.
Approximately 80% of scleroderma patients have abnormal capillaroscopic findings. Capillary damage is also common in mixed connective tissue disease and dermatomyositis, but is reported less often in lupus erythematosus and eosinophilic fasciitis.
Thermography
Thermography is used to assess the degree of vasospasm in the peripheral circulation of Raynaud's phenomenon patients.
The patient is adapted to a room temperature of 23°C for 15 minutes before a thermal image of the hands is recorded using the unit's Thermacam SC500 thermal imager. (FLIR Systems). The patient's hands are then gloved and immersed in water at 15°C for one minute. After this procedure the hands are then imaged for a further 10 minutes to assess the speed of re-warming.
Healthy hands tend to re-warm to the baseline temperature within 10 minutes, with a rapid heating of the fingertips as blood flows through dilated small arteries.
In Raynaud's patients, peripheral vasoconstriction of the small arteries causes a greatly delayed rewarming of the fingertips.
Fingertip temperature over the test period may be extracted from the thermal images and plotted on a graph to allow comparison between patients, or of the same patient before and after therapy.