To improve the spatial resolution and to obtain the depth information of absorbers buried in highly scattering material, we developed a noncontact backscatter-mode near-infrared time-resolved imaging ...system (noncontact B-TRIS) that is intended for functional human brain mapping. It consists of mode-locked Ti-sapphire lasers as light sources and a charge-coupled device camera equipped with a time-resolved intensifier as a detector. The system was tested with a white polyacetal phantom as a light-scattering medium and black polyacetal particles as absorbers. Illumination and detection of light through an objective lens system
enabled us to capture images from an area whose diameter is about
without coming into contact with it. The scattering and absorption coefficients of the white phantom obtained by B-TRIS were similar to those obtained by a conventional time-resolved spectroscopy. Although the imaged diameter of an absorber buried within a phantom was considerably larger than the actual diameter, the center position of the absorber coincided with the actual position with accuracy
. Furthermore, the depth information can be also detected by the noncontact B-TRIS. These results suggest a potential of noncontact B-TRIS for imaging cognitive human brain function.
We present a novel method for estimating the intrinsic fluorescence lifetime of deeply embedded localized fluorophores. It is based on scaling relations, characteristic for turbid media. The approach ...is experimentally substantiated by successfully reconstructing lifetimes for targets at depths up to
. A derived correction factor was determined from the product of the transport-corrected scattering coefficient
and the index of refraction
. In addition, data from an array of detectors
can be used to estimate
. The suggested algorithm is a promising tool for diagnostic fluorescence, since lifetime can be a sensitive indicator of the fluorophore environment.
We have developed a new descanned parallel (32-fold) pinhole and photomultiplier detection array for multifocal multiphoton microscopy that effectively reduces the blurring effect originating from ...scattered fluorescence photons in strongly scattering biological media. With this method, we achieve a fourfold improvement in photon statistics for detecting ballistic photons and an increase in spatial resolution by 21 in the lateral and 35 in the axial direction compared to single-beam non-descanned multiphoton microscopy. The new detection concept has been applied to plant leaves and pollen grains to verify the improvements in imaging quality.
Since the mid-1980s, the development of a therapeutic, computer-assisted laser photocoagulation system to treat retinal disorders has progressed under the guidance of Dr. Welch, the Marion E. Forsman ...Centennial Professor of Engineering, Department of Biomedical Engineering, the University of Texas at Austin. This paper reviews the development of the system, related research in eye movement and laser-tissue interaction, and system implementation and testing. While subsets of these topics have been reported in prior publications, this paper brings the entire evolutionary design of the system together. We also discuss other recent "spinoff" uses of the system technology that have not been reported elsewhere and describe the impact of the latest technical advances on the overall system design.
We present the fourth in a series of studies devoted to the issue of improving image quality in diffuse optical tomography (DOT) by using a spatial deconvolution operation that seeks to compensate ...for the information-blurring property of first-order perturbation algorithms. Our earlier reports consider only static target media. Here we report spatial deconvolution applied to media with time-varying optical properties, as a model of tissue dynamics resulting from varying metabolic demand and modulation of the vascular bed. Issues under study include the influence of deconvolution on the accuracy of the recovered temporal and spatial information. The impact of noise is also explored, and techniques for ameliorating its information-degrading effects are examined. At low noise levels (i.e,
of the time-varying signal amplitude), spatial deconvolution markedly improves the accuracy of recovered information. Temporal information is more seriously degraded by noise than is spatial information, and the impact of noise increases with the complexity of the time-varying signal. These effects, however, can be significantly reduced using simple noise suppression techniques (e.g., low-pass filtering). Results suggest that the deconvolution scheme should provide considerable enhancement of the quality of spatiotemporal information recovered from dynamic DOT techniques applied to tissue studies.
The topical application of drugs, such as nicotinates, affects cutaneous blood flow. Such a biological response, which is dependent on the drug and the individual, can be measured noninvasively using ...laser Doppler flowmetry. We illustrate the kinetics of vasodilation caused by topically applied benzyl nicotinate using a new frequency-selective laser Doppler flowmeter. This flowmeter measures the blood flow in the superficial dermal plexus and the deeper lying larger capillaries simultaneously and indirectly by determining the flow velocity. Both sets of data are compared with the skin temperature and redness. Four biological parameters are measured consecutively on a skin area treated with gel containing benzyl nicotinate and on an untreated control area. A linear relationship between both blood flows is observed. However, no correlation is obtained between the microcirculation with either the cutaneous temperature or the redness. These results indicate the transport of the drug in the blood from the upper to the deeper capillaries. Cutaneous temperature and redness are unsuitable parameters to measure the kinetics of the blood flow after topical application of drugs.
In this study, an automatic blood vessel searching system (BVSS) is newly developed, which is built in the Health Monitoring System (HMS) and the drug delivery system (DDS) to extract the blood, ...evaluate the blood sugar level and inject the insulin for the diabetic patients. Main subjects of this BVSS development are 1) a transmittance photo imaging of the finger by using the LED light as the near-infrared light source with the peak wave length of 870 nm, and 2) an image processing to detect the location of the center of blood vessel. To estimate the depth of blood vessel, the lens focal method was employed in the BVSS. To confirm the availability of this method, we carried out experiments by using a skin tissue phantom having a blood vessel, whose vessel part is made of the teflon tube, and whose skin tissue part is made of the silicone rubber. The teflon blood vessel was 0.6 mm in diameter and wasfilled with the human blood. Experimental results demonstrated that the estimated depth has shown a good agreement with the given depth.
During stereotactic brain tumor biopsies, the detection of protoporphyrin IX (PpIX) fluorescence and microvascular perfusion using laser Doppler flowmetry (LDF) with a handheld fiber optic probe ...allows the identification of tumor tissue while decreasing the risk of intracranial hemorrhage. Neurosurgeons performing this procedure usually view the measurement values on a screen. When their visual focus is directed at the surgical site, they require an assistant to verbally relay the values. An auditory and visual user interface (UI), which displays measurement values accurately and allows fast and intuitive signal recognition, can improve this procedure. This paper experimentally evaluates an auditory and visual UI for providing real-time measurement feedback during stereotactic brain tumor biopsies. In a user study (n = 15), the accuracy of auditory and visual response was determined using function response tests, and user acceptance was evaluated. The auditory signals proved to be intuitive and easy to recognize and remember. The visual display of measurement values was easy to understand and facilitated the user's decision-making process. Moreover, the UI exhibited high user acceptance.
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