Multichannel time-resolved optical tomographic imaging system

Abstract

A time-resolved optical imaging system using near-infrared light has been developed. The system had three pulsed light sources and total 64 channels of detection, working simultaneously for acquisition of the time-resolved data of the pulsed light transmitted through scattering media like biological tissues. The light sources were provided by high power picosecond pulsed diode lasers, and optical switches directed one of the light sources to the object through an optical fiber. The light signals reemitted from the surface of the object were collected by optical fibers, and transmitted to a time-resolved detecting system. Each of the detecting channels consisted of an optical attenuator, a fast photomultiplier, and a time-correlated single photon counting circuit which contained a miniaturized constant fraction discriminator/time-to-amplitude converter module, and a signal acquisition unit with an A/D converter. The performance and potentiality of the imaging system have been examined by the image reconstruction from the measured data using solid phantoms.

A near infrared instrument to monitor relative hemoglobin concentrations of human bone tissue in vitro and in vivo

“…9 The types are continuous wave ͑cw͒, 2,10-16 frequency domain, 17,18 and time domain. 19 The instrument presented in this paper is a cw type instrument. As it is required to monitor changes in the concentrations of Hb and HbO 2 in the tibia, rather than generate a topographic or tomographic image of that tissue, high spatial resolution is not required.…”

Diffuse Optical Imaging

“…In order to reduce the intensity that can reach the detector, a variable optical attenuator (VOA) can be used to attenuate light in a controlled way (Eda et al, 1999;Schmidt et al, 2000). It consists of a disk with a set of holes of different sizes, or neutral density filters with different optical densities.…”

“…Instruments for diffuse optical imaging can be classified into three groups: time-domain systems which measure the full temporal point spread function of tissue to a pulse of light (Chance et al, 1988;Delpy et al, 1988, Eda et al, 1999Schmidt et al, 2000), frequencydomain systems which measure the amplitude and phase shift of the detected light with respect to an intensity-modulated source light (Lakowicz and Berndt, 1990;Chance et al, 1998b;McBride et al, 2001;Nissilä et al, 2002a), and continuous wave systems, which measure the DC intensity of detected light (Schmitz et al, 2002). The primary advantage of time-and frequency-domain techniques is that they may provide enough information for the separation of features in scattering and absorption.…”

Towards the next generation of near-infrared spectroscopy

“…Because time-resolved instrumentation was developed as laboratory-based devices, it has been difficult to use in the clinical environment. However, recent advances in technology have made the development of a compact 64-channel time-resolved optical imaging system possible [60]. Now, single-/two-channel TRS instruments are commercially available [61].…”

“…In the 1990s, we developed the 64-channel TR-DOT system in a research and development project for optical tomographic imaging systems for the New Energy and Industrial Technology Development Organization and Ministry of International Trade and Industry of the Japanese Government [60]. This system has three 100 ps pulsed LDs (wavelengths of 761, 797 and 834 nm) and 64 fibre bundles that are connected to 64 corresponding time-resolved detection devices.…”