[OPTICAL REVIEW Vol. 15, No. 1 (2008) 51-56]
© 2008 The Optical Society of Japan

Depth-Adaptive Regularized Reconstruction for Reflection Diffuse Optical Tomography

Reiko ENDOH*, Mamiko FUJII, and Kiyoshi NAKAYAMA

Department of Electrical and Electronics Engineering, Faculty of Science and Technology, Sophia University, Tokyo 102-8554, Japan

(Received May 15, 2007; Accepted June 13, 2007)

We study reflection diffuse optical tomography using two-dimensional (2D) continuous-wave source-detector arrays on the surface of semi-infinite medium, aiming at imaging the perfusion and the hemoglobin oxygen saturation variation of human cerebral cortex with brain activation. We had previously formulated the inverse problem with Moore–Penrose inversion. When we use simple regularization in this inverse problem, the reconstruction sensitivity decreases markedly with the depth so that the signal in the deep range may be masked by an unwanted signal in the shallow range. In this paper, we propose a depth-adaptive regularized reconstruction, in which we assign a smaller regularization parameter with the depth. We demonstrate improvement of the three-dimensional (3D) reconstruction uniformity using the proposed scheme.

Key words: diffuse optical tomography, DOT, 3D image reconstruction, depth-adaptive regularized reconstruction, inverse problem, regularization parameter, brain activity measurement

*Present affiliation: Research Center for Medical Sciences, The Jikei University School of Medicine.
Present affiliation: Electro Design Corporation.