Design and implementation of a multifrequency near-infrared diffuse optical tomography system

Abstract

Abstract. The design and implementation of a multifrequency and multispectral diffuse optical tomography system is described. Four wavelengths are utilized: 665, 785, 808, and 830 nm. The system is based on a network analyzer, which provides rf modulation signals for the laser diodes, as well as measures the amplitude and the phase of the detected signals. Six different modulation frequencies ranging from 110 to 280 MHz are used. The details of instrumentation, calibration, data acquisition, and performance of the system are given. A finite element algorithm is used to solve the diffusion equation, and an inverse solver based on this forward solver is implemented to calculate the absorption and scattering maps from the acquired data. Data acquisition for one wavelength is completed in less than 2.5 min for a single modulation frequency. The measurement repeatability is 0.5% in ac intensity and 0.2 deg in phase. The performance of the system is evaluated with phantom studies. A multifrequency reconstruction algorithm is used, in which a single absorption and scattering image pair is obtained using the whole dataset obtained at different modulation frequencies. It is shown that the multifrequency reconstruction approach provides superior image quality compared to the single frequency counterpart.

Modeling and reconstruction of diffuse optical tomography using adjoint method

“…The DOT system is based on a network analyzer that not only measures the amplitude and the phase of the detected signals, but also provides RF signals to modulate the amplitude of laser diode sources. The details of the system were given in Gulsen et al [21]. While the system employs four different wavelengths, only the data acquired at 785 nm were used in this study.…”

Parametric image reconstruction using the discrete cosine transform for optical tomography

“…To this end, researchers have suggested, for example, multispectral methods 1 as well as multifrequency measurement systems. 2 In addition, or alternatively, one can seek to reduce the number of unknowns. In this direction, various groups have suggested combining optical tomography ͑OT͒ with other imaging modalities, such as magnetic resonance imaging ͑MRI͒ 3 or ultrasound ͑US͒.…”

Tumor characterization in small animals using magnetic resonance-guided dynamic contrast enhanced diffuse optical tomography

“…10,11 Hagen et al showed that invasive carcinomas retain an ICG fluorescence signal after being largely clear out from the body, indicating the high permeability of malignant tumors. 12 During the last couple of years, our center has developed a combined MRI-DOT small animal imaging system, 13 which provides a unique opportunity to utilize MRI a priori information for guided dynamic contrast enhanced (DCE)-DOT reconstruction. In this study, Fisher rats bearing R3230 breast tumors are imaged at different stages by our combined MRI-DOT system.…”