Biomedical subjects

E M Sevick-Muraca

Publications and source records attributed to E M Sevick-Muraca.

5 recordsLinked to original sources

PubMed1998

Fluorescence lifetime spectroscopic imaging with measurements of photon migration.

Frequency-domain measurements of photon migration are coupled with a model of fluorescence generation and propagation in order to develop a method for reconstructing maps of fluorescent properties within interior tissue volumes from exterior measurements at the air-tissue interface. Simulation results confirm the feasibility of optical imaging through the use of exogenously administered contrast agents on the basis of fluorophore decay kinetics and yield. Experimental measurements using single-pixel and multipixel devices illustrate that the contrast owing to exogenous fluorescence exceeds that owing to absorption or scattering caused by endogenous chromophores or tissue structure and owing to absorption caused by exogenous contrast agents.

Diagnostic Imaging↗

PubMed1997

Fluorescence and absorption contrast mechanisms for biomedical optical imaging using frequency-domain techniques.

The ability to optically image or detect diseased tissue volumes located deep within tissues depends upon the degree of contrast provided by differences in local optical properties. In this report, we show that the exogenous contrast offered by fluorescent compounds is superior to that provided by nonfluorescing, light-absorbing compounds when time-dependent measurements are employed. In addition, we show that the induced contrast is not only moderated by the preferential uptake of fluorescent agents into diseased tissue volumes of interest but also by the fluorescent optical properties and the fluorescence dynamics in the specific tissue volume. Using tissue phantom studies, we demonstrated experimentally that near-infrared-absorbing and fluorescent dyes such as indocyanine green can provide detection of diseased tissue volumes from fluorescence measurements made at the periphery of tissue when there is perfect, 100-fold and 10-fold partitioning in diseased tissues over that in surrounding normal tissues. Experimental results of common laser dyes show the contrast is also mediated by the quantum yield and lifetime parameters that may be dependent upon the local tissue environment.

Diagnosis↗

PubMed1995

Fluorescence lifetime-based sensing in tissues: a computational study.

We have numerically solved the photon diffusion equation to predict the distribution of light in a tissue model system with a uniform concentration of fluorophore. Our results show that time-dependent measurements of light propagation can be used to monitor the fluorescent lifetimes of a uniformly distributed fluorophore in tissues. With proper referencing, frequency-domain measurements of phase-shift, theta, may allow quantitation of fluorescent lifetimes, tau, independent of changes in the local absorption and scattering properties. These results point to a new approach for noninvasive diagnostic monitoring through quantitation of fluorescent lifetime, tau, when the lifetime of the fluorophore is comparable with photon migration times.

Biophysical Phenomena↗

PubMed1994

Computations of time-dependent photon migration for biomedical optical imaging.

In summary, Table II is a listing of the pitfalls and advantages of using Monte Carlo simulations and numerical solution of the diffusion equation to describe photon migration in tissues. Judicious use of these techniques to describe the solution to the forward imaging problem may allow determination of the best theoretical resolution and the smallest detectable volume for the range of optical property differences expected in situ or imposed by contrast agent administration. Furthermore, an understanding of the forward imaging problem through these numerical techniques also contributes to our understanding of the most efficient solution to the inverse imaging problem.

Algorithms↗

PubMedDate not supplied

Multipixel techniques for frequency-domain photon migration imaging.

The ability to map interior optical properties of a highly scattering medium from exterior measurements of light propagation is afforded by optical tomography. In this communication, we describe the problem of optical tomography, the techniques of photon migration measurements necessary to accomplish it, and the development of multipixel measurements for rapid collection of optical signals. These multipixel measurements are shown to provide detection of contrast owing to the optical properties of absorption and fluorescence associated with dye-laden heterogeneities embedded in a tissue-like scattering medium. From these rapid measurements, successful reconstruction of an interior optical property map may now be possible with clinically realistic data acquisition times. Applications for the technology arise for biomedical optical imaging for the in vivo detection of disease and the diagnosis of tissue (bio-) chemistry.

Absorption↗