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Biomedical subjects

M S Feld

Publications and source records attributed to M S Feld.

61 records · Page 4Linked to original sources
PubMed1987

A model for thermal ablation of biological tissue using laser radiation.

We present a theory of thermal laser ablation based on the heat equation and on an energy balance equation derived from it. Ablation is assumed to be brought about by the heating and evaporation of tissue water. The model is three-dimensional, and scattering and the water-steam phase transition are explicitly taken into account. The model predicts threshold parameters and a steady-state ablation velocity in terms of the optical and thermal properties of the tissue and the laser beam intensity and spot diameter.

Biophysical Phenomena↗
PubMed1975

Maintenance of labour.

In 160 women large but variable amounts of intravenous oxytocin were needed to induce labour within a reasonable time interval to 5 cm cervical dilatation. Thereafter 7 mU of oxytocin/min would maintain progress. Since large maintenance doses may cause obstetric problems it is recommended that a maintenance regimen should be used once labour has progressed to this stage.

Cervix Uteri↗
PubMedDate not supplied

Diagnosis of human coronary atherosclerosis by morphology-based Raman spectroscopy.

BACKGROUND: Recent studies have shown that chemical composition and morphology, rather than anatomy (degree of stenosis), determine atherosclerotic plaque instability and predict disease progression. Current clinical diagnostic techniques provide accurate assessment of plaque anatomy, but have limited capability to assess plaque morphology in vivo. Here we describe a technique for a morphology-based diagnosis of atherosclerosis in the coronary arteries using Raman spectroscopy that can potentially be performed in vivo using optical fiber technology. METHODS: Raman tissue spectra were collected from normal and atherosclerotic coronary artery samples in different stages of disease progression (n=165) from explanted transplant recipient hearts (n=16). Raman spectra from the elastic laminae (EL), collagen fibers (CF), smooth muscle cells (SMC), adventitial adipocytes (AA) or fat cells, foam cells (FC), necrotic core (NC), cholesterol crystals (CC), beta-carotene containing crystals (beta-C), and calcium mineralizations (CM) were used as basis spectra in a linear least squares-minimization (LSM) model to calculate the contribution of these morphologic structures to the coronary artery tissue spectra. RESULTS: We developed a diagnostic algorithm that used the fit-contributions of the various morphologic structures to classify 97 coronary artery samples in an initial calibration data set as either nonatherosclerotic, calcified plaque, or noncalcified atheromatous plaque. The algorithm was subsequently tested prospectively in a second validation data set, and correctly classified 64 (94%) of 68 coronary artery samples. CONCLUSIONS: Raman spectroscopy provides information about the morphologic composition of intact human coronary artery without the need for excision and microscopic examination. In the future, it may be possible to use this technique to analyze the morphologic composition of atherosclerotic coronary artery lesions and assess plaque instability and disease progression in vivo.

Adipocytes↗
PubMedDate not supplied

Raman microspectroscopy of human coronary atherosclerosis: biochemical assessment of cellular and extracellular morphologic structures in situ.

BACKGROUND: We have previously shown that Raman spectroscopy can be used for chemical analysis of intact human coronary artery atherosclerotic lesions ex vivo without tissue homogenization or extraction. Here, we report the chemical analysis of individual cellular and extracellular components of atherosclerotic lesions in different stages of disease progression in situ using Raman microspectroscopy. METHODS: Thirty-five coronary artery samples were taken from 16 explanted transplant recipient hearts, and thin sections were prepared. Using a high-resolution confocal Raman microspectrometer system with an 830-nm laser light, high signal-to-noise Raman spectra were obtained from the following morphologic structures: internal and external elastic lamina, collagen fibers, fat, foam cells, smooth muscle cells, necrotic core, beta-carotene, cholesterol crystals, and calcium mineralizations. Their Raman spectra were modeled by using a linear combination of basis Raman spectra from the major biochemicals present in arterial tissue, including collagen, elastin, actin, myosin, tropomyosin, cholesterol monohydrate, cholesterol linoleate, phosphatidyl choline, triolein, calcium hydroxyapatite, calcium carbonate, and beta-carotene. RESULTS: The results show that the various morphologic structures have characteristic Raman spectra, which vary little from structure to structure and from artery to artery. The biochemical model described the spectrum of each morphologic structure quite well, indicating that the most essential biochemical components were included in the model. Furthermore, the biochemical composition of each structure, indicated by the fit contributions of the biochemical basis spectra of the morphologic structure spectrum, was very consistent. CONCLUSIONS: The Raman spectra of various morphologic structures in normal and atherosclerotic coronary artery may be used as basis spectra in a linear combination model to analyze the morphologic composition of atherosclerotic coronary artery lesions.

Biomarkers↗