To the Editor:
It is possible to examine the inflammation of a joint, bursa, or tendon area with ultrasonography (US) using greyscale or Doppler imaging1. The detection of perfusion in synovium is a relatively new phenomenon in rheumatology and the detection of a Doppler signal in the synovium is also thought to reflect the inflammatory state2. Rheumatoid synovium is imaged by using color Doppler or power Doppler modes. The latter is thought to be better suited for depicting slow flows3, although there is an article in the literature showing no big difference between these modes4.
The aim of this report is to consider what a positive or negative power Doppler signal in the synovium means, especially in terms of histological data. And as well, to raise a question: have we thought too much of anatomy, i.e., the number of vessels (angiogenesis) in Doppler imaging, instead of explaining the existence or absence of Doppler signal with changes of flow (perfusion) in healthy and diseased synovium?
In the rheumatoid synovium the thickness of synovial lining hyperplasia, number of vessels, and stage of inflammation of the synovium correlate positively with each other, and the number of vessels is increased5. The question is whether the angiogenesis of the synovitis is the cause or consequence (“chicken or egg”)6. Another study with 44 synovial biopsies in patients with inflammatory joint diseases also showed that the number of vessels correlated positively with the inflammatory state of the synovium r = 0.629, p < 0.01; this statistic was not shown in the original report)7 …
Address correspondence to Dr. Koski; E-mail: f.koski{at}fimnet.fi