Yoshiaki SASAKI¹, Jota SUZUKI¹, Hiroki INAGE¹, Ryota EMORI¹, Shinji TANOSAKI^1,2, Tetsuya YUASA¹, Michiaki TAKAGI³, Akira ISHIKAWA³, Hiroshi TANIGUCHI⁴, Balasigamani DEVARAJ⁵ and Takao AKATSUKA¹

¹Faculty of Engineering, Yamagata University, 4-3-16 Jonan, Yonezawa, Yamagata 992-8510, Japan
²I.T. Research, Co., Ltd., 21st Century Plaza, 2-1-4 Takamori, Izumi-ku, Sendai, Miyagi 981-3203, Japan
³School of Medicine, Yamagata University, 2-2-2 Iida-Nishi, Yamagata, Yamagata 990-0031, Japan
⁴Faculty of Engineering, Iwate University, 4-3-5 Ueda, Morioka, Iwate 020-8551, Japan
⁵New Focus, Inc., 5215 Hellyer Avenue, San Jose, CA 95138-1001, USA

(Received February 13, 2003; Accepted April 8, 2003)

We recently proposed and developed a novel transillumination laser computed tomography (CT) imaging system using a fiber-optic method based on coherent detection imaging (CDI) for biomedical use. Use of optical fibers enables portability and robustness against environmental changes in a room, such as variable temperature, air-flow shifts, and unexpected vibrations. In addition, motion-artifact-free images can be obtained because measurements can be performed with the object fixed. In the present paper, we experimentally investigate in detail the fundamental imaging properties of the system, which has a 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. Based on experimental observations, the proposed system can reconstruct tomographic images of highly scattering objects in the transillumination mode, similar to X-ray CT, at sub-millimeter spatial resolution and with quantitativeness. Finally, we demonstrate with experiments using a physical phantom that the imaging system possesses high resolution and quantitative imaging abilities for highly scattering objects.

Key words: Laser computed tomography, coherent detection imaging, optical heterodyne detection, optical fiber