An introduction to the basics of spectral imaging as applied to biological tissues is presented. An example of a spectral image of a face is used to demonstrate the data and spectral analysis that specify the melanin content (M), blood content (B), tissue oxygen saturation (S), water content (W), fraction of scattering due to Rayleigh scattering (f) and due to Mie scattering (1 - f), and the reduced scattering coefficient at 500-nm wavelength (μ's 500 nm). The sensitivity of reflectance spectra to variation in the various parameters is illustrated.

We investigate the propagation of polarized light in fibrous tissues such as muscle and skin. The myofibrils and collagen fibers are approximated as long cylinders and the tissue phantom is composed of spherical and cylindrical structures. We apply Monte Carlo method based on this phantom to simulate and analyze polarization imaging process of muscle. The good agreement between the simulation results and the experimental results validate the assumption of the phantom composition. This paper also presents how to describe the fiber orientation distribution and tissue anisotropy according to three parameters derived from the polarization imaging.

This paper explains the Moire chromatography technique and the optical characteristics when the light crosses the 3D air flow field. Based on this, taking grating, CCD camera, optical filter and diaphragm as the main device, a multi-direction Moire chromatography optical system was designed. The system consists of five detective light paths, in each detective light path there is parallel and same periodic grating and filtering minipore placed on the lens’ focal length plane; the grating is used to adjust the space length and angle between the two gratings, and the filtering minipore is used to remove the unorderly high frequency intermix in the Moire fringe. Utilizing the computer escalator method to convert the tested value, the vivid interference fringe of tested parameter can be obtained. The application of this system in precision measurement and medicine is also analyzed and discussed.

An image-reconstruction approach for optical tomography is presented, in which a two-layered BP neural network is used to distinguish the tumor location. The inverse problem is solved as optimization problem by Femlab software and Levenberg–Marquardt algorithm. The concept of the average optical coefficient is proposed in this paper, which is helpful to understand the distribution of the scattering photon from tumor. The reconstructive μ's by the trained network is reasonable for showing the changes of photon number transporting inside tumor tissue. It realized the fast reconstruction of tissue optical properties and provided optical OT with a new method.

To provide a computational efficient forward model with moderate accuracy for rapid 3D optical tomography in small volumes, radiative transport in the delta-P1 approximation combined with the approximation of the reciprocity was examined. Perturbations of optical signals caused by absorption and fluorescence heterogeneities submerged in a resin-based liquid phantom with background parameters close to rat brain tissues were measured using a recently constructed laminar optical tomography system. These measured perturbations were used to examine the theoretically calculated fluence perturbations based on the delta-P1 approximation and the reciprocity approximation. Results show that the errors between the predicted and measured data are acceptable, especially for fluorescence perturbations.

Fluorescence tomography can obtain a sufficient dataset and optimal three-dimensional images when projections are captured over 360? by CCD camera. Herein a non-stop dynamic sampling mode for fluorescence tomography is proposed in an attempt to improve the optical measurement speed of the traditional imaging system and stability of the object to be imaged. A series of simulations are carried out to evaluate the accuracy of dataset acquired from the dynamic sampling mode. Reconstruction with the corresponding data obtained in the dynamic-mode process is also performed with the phantom. The results demonstrate the feasibility of such an imaging mode when the angular velocity is set to the appropriate value, thus laying the foundation for real experiments to verify the superiority in performance of this new imaging mode over the traditional one.

The purpose of this study is to investigate whether a near-infrared fluorescence (NIRF) probe, Cy5.5-d-glucosamine (Cy5.5-2DG), can image arthritis in collagen-induced arthritic (CIA) mice. The presence of arthritis was verified by both visual examination and micro-computed tomography (MicroCT) imaging. CIA mice were imaged by a micro-positron emission tomography (MicroPET) scanner one hour after intravenous injection of 2-deoxy-2-[18F]fluoro-d-glucose ([18F]FDG). After radioactivity of [18F]FDG decayed away, Cy5.5-2DG was injected into a lateral tail vein of the mice. Arthritic tissue targeting and retention of Cy5.5-2DG in CIA mice were evaluated and quantified by an optical imaging system. Inflammatory tissue in CIA mice was clearly visualized by [18F]FDG-MicroPET scan. NIRF imaging of Cy5.5-2DG in the same mice revealed that the pattern of localization of Cy5.5-2DG in the arthritic tissue was very similar to that of [18F]FDG. Quantification analysis further showed that [18F]FDG uptake in arthritic tissues at one hour post-injection (p.i.) and Cy5.5-2DG uptakes at different time points p.i. were all well correlated (r2 over 0.65). In conclusion, Cy5.5-DG can detect arthritic tissues in living mice. The good correlation between the [18F]FDG uptake and Cy5.5-2DG accumulation in the same arthritic tissue warrants further investigation of Cy5.5-2DG as an approach for assessment of anti-inflammatory treatments.

We present a catheter-based optical diffusion and fluorescence (ODF) probe to study the functional changes of the brain in vivo. This ODF probe enables the simultaneous detection of the multi-wavelength absorbance and fluorescence emission from the living rat brain. Our previous studies, including a transient stroke experiment of the rat brain as well as the brain response to cocaine, have established the feasibility of simultaneously determining changes in cerebral blood volume (CBV), tissue oxygenation (StO2) and intracellular calcium ([Ca2+]i, using the fluorescence indicator Rhod2). Here, we present our preliminary results of somatosensory response to electrical forepaw stimulation obtained from the rat cortical brain by using the ODF probe, which indicate that the probe could track brain activation by directly detecting [Ca2+]i along with separately distinguishing CBV and StO2 in real time. The changes of CBV, StO2 and [Ca2+]i are comparable with the blood-oxygen-level-dependent (BOLD) response to the stimulation obtained using functional magnetic resonance imaging (fMRI). However, the high temporal resolution of the optical methodology is advanced, thus providing a new modality for brain functional studies to understand the hemodynamic changes that underlie the neuronal activity.

Using a near-infrared (NIR) light flood-illumination imager equipped with a high-speed (120Hz) CCD camera, we demonstrated optical imaging of stimulus-evoked retinal activity in isolated, but intact, frog eye. Both fast and slow transient intrinsic optical signals (IOSs) were observed. Fast optical response occurred immediately after the stimulus onset, could reach peak magnitude within 100ms, and correlated tightly with ON and OFF edges of the visible light stimulus; while slow optical response lasted a relatively long time (many seconds). High-resolution images revealed both positive (increasing) and negative (decreasing) IOSs, and dynamic optical change at individual CCD pixels could often exceed 10% of the background light intensity. Our experiment on isolated eye suggests that further development of fast, high (sub-cellular) resolution fundus imager will allow robust detection of fast IOSs in vivo, and thus allow noninvasive, three-dimensional evaluation of retinal neural function.

Apoptosis is an important cellular event that plays a key role in the therapy of many diseases. The mechanism of the initiation and regulation of photodynamic therapy (PDT)–induced apoptosis is complex. Our previous study found that Photofrin was localized primarily in mitochondria, the primary targets of Photofrin-PDT. The key role of Bax in the mitochondria-mediated apoptosis has been demonstrated in many systems. In order to determine the role of Bax in the mitochondrion-mediated apoptosis induced by Photofrin-PDT, we used the GFP-Bax plasmid to monitor the dynamics of Bax activation after PDT treatment. With laser scanning confocal microscopy, we found that Bax did not translocate from the cytosol to mitochondria when the mitochondrial membrane potential (ΔΨm) disappeared, measured by TMRM. Thus, for Photofrin-PDT, the commitment to cell death is independent of Bax activation.