DEVELOPMENT OF A FINGER JOINT PHANTOM FOR THE OPTICAL-SIMULATION OF EARLY STAGES OF RHEUMATOID-ARTHRITIS

In the field of rheumatology, conventional diagnostic methods permit t he detection only of advanced stages of the disease, which is at odds with the current clinical demand for the early diagnosis of inflammato ry rheumatic diseases. Prompted by current needs, we developed a finge r joint phantom that enables the optical and geometrical simulation of an early stage of rheumatoid arthritis (RA). The results presented he re form the experimental basis for an evaluation of new RA diagnostic systems based on near infrared light. The early stage of RA is charact erised mainly by a Vigorous proliferation of the synovial membrane and clouding of the synovial fluid. Using a double-integrating-sphere tec hnique, the absorption and scattering coefficients (mu(a)-mu(s)') are experimentally determined for healthy and pathologically altered synov ial fluid and capsule tissue. Using a variable mixture of Intralipid(R ) Indian ink and water as a scattering/absorption medium, the optical properties of skin, synovial fluid or capsule can be selected individu ally. Since the optical and geometrical properties of bone tissue rema in constant in early-stage RA, a solid material is used for its simula tion. Using the finger joint phantom described herein, the optical pro perties of joint regions can be adjusted specifically, enabling an eva luation of their effects on an optical signal-for example, during fluo rography-and the investigation of these effects for diagnostically use ful information. The experimental foundation for the development of a new optical system for the early diagnosis of RA has now been laid.