Shinji TANOSAKI, Yoshiaki SASAKI, Michiaki TAKAGI¹, Akira ISHIKAWA¹, Hiroki INAGE, Ryota EMORI, Jyota SUZUKI, Tetsuya YUASA, Hiroshi TANIGUCHI², Balasigamani DEVARAJ³ and Takao AKATSUKA

Faculty of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa 992-8510, Japan
¹School of Medicine, Yamagata University, 2-2-2 Iida-Nishi, Yamagata 990-9585, Japan
²Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka 020-8551, Japan
³New Focus Inc., 5215 Hellyer Avenue, San Jose, CA 95138-1001, U.S.A.

(Received January 20, 2003; Accepted May 21, 2003)

The coherent detection imaging (CDI) technique based on the optical heterodyne detection method enables selective filtering of the directional coherent retaining emergent photons from biological tissues with a highly scattering nature. Therefore, the CDI can acquire on-axis information in the transillumination mode and use the same data-acquisition protocol and reconstruction algorithm as those in X-ray computed tomography (CT). Although the CDI-based laser CT cannot image thick subjects such as the head and chest, it can delineate subjects with a thickness up to several cm at a spatial resolution of sub-millimeters. We are planning to apply the technique to early diagnosis of rheumatoid arthritis (RA). Here, we performed an experiment using mice to confirm the feasibility. We compared in vivo CT images at the level of ankle joints of two mice, one normal and the other with collagen induced arthritis (CIA) as an RA model, and demonstrated that there occur significant discrepancies between the two distributions of image intensities, i.e., reconstructed scattering coefficients in each region of interest (ROI) prepared. We suggest that combining the morphological information with the quantitative information can be effective for early diagnosis of bone diseases and disorders such as rheumatoid arthritis.

Key words: laser computed tomography, coherent detection imaging, optical heterodyne detection, rheumatoid arthritis