Analysis on performance and optimization of frequency-domain near-infrared instruments

Abstract

Frequency-domain near-infrared techniques have been widely used to detect the optical properties of biological tissues noninvasively. In this paper we propose an analytical model to evaluate the performance of frequency-domain instruments. Based on the diffusion equation and the transfer properties of optoelectronic components, we treat all parts, including the medium, as two-port networks and apply systematic methods to answer questions concerning frequency-domain instruments. Experiments show that this method can reasonably reflect the properties of the instrument within an accuracy of 7%. This kind of method can be used to design suitable instruments for various applications. We also analyze the selection of the instrument parameters to achieve optimal performance at an efficient cost using this analytical model.

Effect of noise on modulation amplitude and phase in frequency-domain diffusive imaging

“…Furthermore, the modulation depth m p in Eqs. (17) and (19) is dramatically decreased as the modulation frequency increases, which further degrades the estimation forφ. Although recently developed noise models for heterodyne and homodyne measurements indicate that small m p reduces σ 2 AC in Eq.…”

“…Substituting a AC and σ 2 DC of Eqs. (17) and (18) to Eq. (14) produces γ for the case of heterodyne measurements, which is…”

“…11,16 In another study, the influence of system parameters on amplitude and phase signal-to-noise ratios (SNRs) was analyzed. 17 The statistical characteristics of the frequency-response quantities also play an important role in FLI, where the fluorescent lifetime of fluorophores, an indicator of biological characteristics of tissues, is estimated. Instead of directly measuring the lifetime, which is typically a few or tens of nanoseconds, the frequencyresponse of fluorophores is measured using intensifymodulated beams.…”

A Photoplethysmography Melanin Evaluation System by Modified Boltzmann Transport Equation (BTE)

“…Due to large attenuation of light propagating in the medium, about 100 dB, and the noise that interferes with the signal, an appropriate design of the system is quite important to have good performance in subsequent analysis [72]. The signal first passes a transimpedance amplifier (TIA), bandpass filters (BPF), a multiplexer (MUX), and a constant gain amplifier (AMP).…”

Noise characteristics of heterodyne/homodyne frequency-domain measurements

“…The noise is especially significant in diffusive medical imaging, such as DOT and FLI, because of low photon counts. [12][13][14][15][16][17] The performance of noise-contaminated systems can be evaluated quantitatively by considering figures of merit (FOMs) that are chosen to reflect an observer's ability to perform these medial-relevant tasks. 15,18 Task-based assessment of image quality evaluates and/or optimizes diffusive imaging systems by employing FOMs that assess observer performance.…”