Special Section Guest Editorial: Pioneer in Biomedical Optics: Introduction to the Special Section in Honor of Steven L. Jacques

This guest editorial introduces the special section honoring Prof. Steven L. Jacques. We present this special section of the Journal of Biomedical Optics in honor of Steven L. Jacques, PhD, a leading pioneer in the field of biomedical optics. In the late eighties, Steve was part of a small group of researchers from various disciplines who clearly saw the potential of light and optics for new approaches to medical diagnostics and treatment of various diseases. Since then the field has grown exponentially and biomedical optics has become an integral part in many medical disciplines. Through his work and many seminal contributions, Steve has actively shaped this development

Parallel Programming of gradient-based iterative image reconstruction schemes for optical tomography

Summary Optical tomography (OT) is a fast developing novel imaging modality that uses near-infrared (NIR) light to obtain cross-sectional views of optical properties inside the human body. A major challenge remains the time-consuming, computationalintensive image reconstruction problem that converts NIR transmission measurements into cross-sectional images. To increase the speed of iterative image reconstruction schemes that are commonly applied for OT, we have developed and implemented several parallel algorithms on a cluster of workstations. Static process distribution as well as dynamic load balancing schemes suitable for heterogeneous clusters and varying machine performances are introduced and tested. The resulting algorithms are shown to accelerate the reconstruction process to various degrees, substantially reducing the computation times for clinically relevant problems

How source/collector placement and subsurface absorbing layer affect time-resolved and phase/modulation-resolved photon migration

The time-resolved reflectance of photons from a homogeneous tissue was modeled using a Monte Carlo simulation. The data was then converted by fast Fourier transform (FFT) into the frequency domain. In the frequency domain, the phase, Φ, and modulation, M, of collected light from a frequency-modulated light source was determined. A comparison of Monte Carlo and diffusion theory was made for various separation distances between the source and collector on the tissue surface. The results showed that Monte Carlo and diffusion theory agreed in the time domain only for times larger than 500 ps after injection of an impulse of photons. In the frequency domain, Monte Carlo and diffusion theory agreed only if the probe separation, r, was at least 2 cm apart for µ_s' = µ_s(1 - g) = 5 cm^(-1), or in dimension less units rµ_s' > 10. The effect of buried absorbed is also tested in the time and frequency domains. A semi-infinite volume of absorber is placed at 0, 3 mm, 6 mm, or (infinity) from the surface of a nonabsorbing tissue. The presence of a deep absorber on the time and frequency domain data show that attenuation of longer pathlength photons causes the phase of collected photons to reduce and the modulation of collected photons to increase. Both effects are indicative of the net shorter pathlength of the ensemble of collected photons

The influence of boundary conditions on the accuracy of diffusion theory in time-resolved reflectance spectroscopy of biological tissues

The applicability of diffusion theory for the determination of tissue optical properties from time-resolved reflectance spectroscopy is investigated. Analytical expressions from diffusion theory using the three most commonly assumed boundary conditions at the air-tissue interface are compared with time-resolved Monte Carlo simulations and measurements on tissue phantoms. The effects of the choice of the boundary conditions on the accuracy of the findings for the optical parameters are quantified, and criteria for accurate curve-fitting algorithms are developed

Wearable toe band system for monitoring of peripheral artery disease

Approximately 8 to 12 million people in the United States suffer from peripheral artery disease (PAD). PAD causes narrowed arteries and reduces blood flow to the lower extremities. People with PAD begin to experience discomfort and pain while walking. Untreated PAD can lead to ulcers, gangrene, and amputation. Before experiencing those severe conditions, detection of narrowing blood vessel enables early diagnosis and treatment. Therefore, accurate and timely diagnosis is necessary. Please click Additional Files below to see the full abstract

Time-resolved reflectance measurements on layered tissues with strongly varying optical properties

Most biological tissues consist of layers with different optical properties. A few examples are the skin, the esophagus, the stomach and the wall of arteries. An understanding of how the light propagates in such layered systems is a prerequisite for any light based therapy or diagnostic scheme. In this study we investigate the influence of different kinds of layers on time resolved reflectance measurements. Experiments were performed on layered gel phantoms and the results compared to Monte Carlo simulations and diffusion theory. It is shown that when a low absorbing medium is situated on top of a high absorbing medium, the absorption coefficient of the lower layer is accessible if the differences in the absorption coefficient are only small. In the case of large difference the optical properties of the upper layer dominate the signal and shield information on the lowest layer. The degree of this shielding effect depends on layer thickness as well as optical properties. In the case of an almost absorption and scattering free layer in between two normal tissues, an overall increase of the signal is visible. However, the overall shape of the curve is about preserved. The apparent scattering coefficient is slightly decreased, while the apparent absorption coefficient is unaltered

Special Section Guest Editorial: Pioneer in Biomedical Optics: Introduction to the Special Section in Honor of Steven L. Jacques

This guest editorial introduces the special section honoring Prof. Steven L. Jacques. We present this special section of the Journal of Biomedical Optics in honor of Steven L. Jacques, PhD, a leading pioneer in the field of biomedical optics. In the late eighties, Steve was part of a small group of researchers from various disciplines who clearly saw the potential of light and optics for new approaches to medical diagnostics and treatment of various diseases. Since then the field has grown exponentially and biomedical optics has become an integral part in many medical disciplines. Through his work and many seminal contributions, Steve has actively shaped this development