Prototype system of laser transillumination computed tomography for early diagnosis of rheumatoid arthritis

Abstract

So far we have shown, through various preliminary imaging experiments with small-animal ankle’s and human finger’s joints both healthy and joint-diseased, that early diagnosis for joint disease such as rheumatoid arthritis (RA) is feasible using a transillumination laser CT. For a practical purpose, we have recently proposed and developed a transillumination laser CT imaging system using optical fibers based on the optical heterodyne detection method for a clinical use. In the proposed system, motion-artifact free images can be obtained because measurements can be performed with the object fixed. In addition, use of fiber-optics enables portability, and robustness against environmental changes in a room, such as variable temperature, air-flow shifts, and unexpected vibrations. The imaging system has the following sensing properties: spatial resolution of 500 μm, a dynamic range of approximately 120 dB, and a minimum-detectable-optical power of 10^-14 W as a result of the excellent properties of the heterodyne detection technique. In the present paper, we describe a prototype laser CT imaging system using optical fibers for early diagnosis of joint disease such as rheumatoid arthritis by demonstrating the first in vivo tomographic image of a volunteer’s index finger joint as well as the fundamental imaging properties.