Elastic light-scattering spectra acquired with single-fiber optical probes with diameters of 100, 200, 400, 600, 800, 1000, 1200, and 1500 μm were used to differentiate cancerous from noncancerous prostate tissues. The spectra were acquired ex vivo on 24 excised prostate tissue samples collected from four patients. For each probe, the spectra and histopathology results were compared in order to investigate the correlation between the core diameters of the single-fiber optical probe and successful differentiation between cancerous and noncancerous prostate tissues. The spectra acquired using probes with a fiber core diameter of 400 μm or smaller successfully differentiated cancerous from noncancerous prostate tissues. Next, the spectra were acquired from monosized polystyrene microspheres with a diameter of 5.00±0.01 μm to investigate the correlation between the core diameters of the probes and the Mie oscillations on the spectra. Monte Carlo simulations of the light distribution of the tissue phantoms were run to interrogate whether the light detected by the probes with different fiber core diameters was in the ballistic or diffusive regime. If the single-fiber optical probes detect light in the ballistic regime, the spectra can be used to differentiate between cancerous and noncancerous tissues.
Tissue oxygen saturation (StO2) is known quite useful parameter for medical applications. A spectroscopic method has been developed to diagnose pathologic tissues due to lack of normal blood circulation by measuring tissue oxygen saturation. In the study, human blood samples with different level of oxygen saturations have been prepared and spectra were taken using an optical fiber probe to investigate correlation between the oxygen saturations and the spectra. The experimental set up for the spectroscopic measurements was consists of a miniature NIR light spectrometer, an optical fiber probe, a halogen-tungsten light source and a laptop. A linear correlation between the oxygen saturation of the blood samples and the ratio of the light of wavelengths 660 nm to 790 nm has been found from the spectra. Then, oxygen saturations of the blood samples were estimated from the spectroscopic measurements within an error of 2.9%. Furthermore, it has been shown that the linear dependence between the ratio and the oxygen saturation of the blood samples was valid for the blood samples with different hematocrits. Tissue oxygen saturation has been estimated from the spectroscopic measurements were taken from the fingers of healthy volunteers using the correlation between the spectra and blood oxygen saturation. The tissue StO2 measured was 80% as expected. The technique developed to measure tissue oxygen saturation has potential to diagnose premalignant tissues, follow up prognosis of cancerous tissues, and evaluation of ischemia reperfusion tissues.
Elastic light single-scattering spectroscopy (ELSSS) system has been developed and tested in diagnosis of cancerous tissues of different organs. ELSSS system consists of a miniature visible light spectrometer, a single fiber optical probe, a halogen tungsten light source and a laptop. Measurements were performed on excised brain, skin, cervix and prostate tumor specimens and surrounding normal tissues. Single fiber optical probe with a core diameter of 100 μm was used to deliver white light to and from tissue. Single optical fiber probe mostly detects singly scattered light from tissue rather than diffused light. Therefore, measured spectra are sensitive to size of scatters in tissue such as cells, nuclei, mitochondria and other organelles of cells. Usually, nuclei of tumor cells are larger than nuclei of normal cells. Therefore, spectrum of singly scattered light of tumor tissue is different than normal tissue. The spectral slopes were shown to be positive for normal brain, skin and prostate and cervix tissues and negative for the tumors of the same tissues. Signs of the spectral slopes were used as a discrimination parameter to differentiate tumor from normal tissues for the three organ tissues. Sensitivity and specificity of the system in differentiation between tumors from normal tissues were 93% and %100 for brain, 87% and 85% for skin, 93.7% and 46.1% for cervix and 98% and 100% for prostate.
The reversible aggregation of red blood cells (RBC) is of current basic science and clinical interest. Using a flow channel and light transmittance (LT) through RBC suspensions, we have examined the effects of wavelength (500 to 900 nm) on the static and dynamic aspects of RBC aggregation for normal blood and suspensions with reduced or enhanced aggregation; the effects of oxygenation were also explored. Salient observations include: 1. significant effects of wavelength on aggregation parameters reflecting the extent of aggregation (i.e., number of RBC per aggregate); 2. no significant effects of wavelength on parameters reflecting the time course of RBC aggregation; 3. a prominent influence of hemoglobin oxygen saturation on both extent and time-course related aggregation parameters measured at wavelengths less than 700 nm, but only on the time-course at 800 nm; and 4. the power of parameters in detecting a given alteration of RBC aggregation is affected by wavelength, in general being greater at higher wavelengths. It is recommended that light sources with wavelengths around 800 nm be used in instruments for measuring RBC aggregation via LT.
Elastic light single-scattering spectroscopy (ELSSS) system with a single optical fiber probe was employed to
differentiate cancerous prostate tissue from non-cancerous prostate tissue ex-vivo just after radical prostatectomy. First,
ELSSS spectra were acquired from cancerous prostate tissue to define its spectral features. Then, spectra were acquired
from surgical margins of excised prostate tissue to detect positive surgical margins based on the spectral features of the
spectra taken from cancerous prostate tissues. Of the total 128 tissue samples were evaluated from 18 patients by ELSSS
system. Comparing of histopathology results and ELSSS measurements revealed that sign of the spectral slopes of
cancerous prostate tissue is negative and non-cancerous tissue is positive in the wavelength range from 450 to 750 nm.
Sign of the spectral slopes were used as a discrimination parameter between cancerous and non-cancerous prostate
tissues. Based on the correlation between histopathology results and sign of the spectral slopes, ELSSS system
differentiates cancerous prostate tissue from non-cancerous with a sensitivity of 0.97 and a specificity of 0.87.
Joint cartilage thickness has been estimated using spatially resolved steady-state reflectance spectroscopy noninvasively
and in-real time. The system consists of a miniature UV-VIS spectrometer, a halogen tungsten light source, and an
optical fiber probe with six 400 um diameter fibers. The first fiber was used to deliver the light to the cartilage and the
other five were used to detect back-reflected diffused light. Distances from the detector fibers to the source fiber were
0.8 mm, 1.6 mm, 2.4 mm, 3.2 mm and 4 mm. Spectra of back-reflected diffused light were taken on 40 bovine patella
cartilages. The samples were grouped into four; the first group was the control group with undamaged cartilages, in the
2nd, 3rd and 4th groups cartilage thickness was reduced approximately 25%, 50% and 100%, respectively. A correlation
between cartilage thicknesses and hemoglobin absorption of light in the wavelength range of 500 nm- 600 nm for source-detector
pairs was found. The proposed system with an optical fiber probe less than 4 mm in diameter has the potential
for cartilage thickness assessment through an arthroscopy channel in real-time without damaging the cartilage.
We have investigated the potential application of elastic light single-scattering spectroscopy (ELSSS) as an adjunctive tool
for screening of cervical precancerous lesions non-invasively and in real time. Ex-vivo measurements were performed on
95 cervix biopsy tissue of 60 patients. Normal cervix tissue from 10 patients after hysterectomy was used as a control
group. Correlation between ELSSS spectra and histopathology results were investigated. It was found that the spectral
slope was positive for all the spectra taken on normal cervix tissue samples from the control group. We assumed that if
there is only one spectrum with a negative spectral slope among the all spectra taken on a biopsy specimen, the biopsy
specimen is pathologically abnormal. This shows that pap smear and ELSSS results are in good agreement. Most biopsy
tissue samples had both positive and negative spectral slopes. Therefore, we calculated the percentage of negative spectral
slopes and hypothesized that this was correlated to dysplastic percentage of the epithelial tissue of the biopsy material.
The ROC curve was calculated using the dysplastic percentage and high squamous intraepithelial lesion (HSIL) and low
squamous intraepitherlial lesions (LSIL) biopsy specimens were differentiated from non HSIL and LSIL with a sensitivity
and specificity of 70.4% and 66.7% respectively, with p < 0.05.
We have investigated the potential application of elastic light single-scattering spectroscopy (ELSSS) as an adjunctive tool for intraoperative rapid detection of brain tumors and demarcation of the tumor from the surrounding normal tissue. Measurements were performed on 29 excised tumor specimens from 29 patients. There were 21 instances of low-grade tumors and eight instances of high-grade tumors. Normal gray matter and white matter brain tissue specimens of four epilepsy patients were used as a control group. One low-grade and one high-grade tumor were misclassified as normal brain tissue. Of the low- and high-grade tumors, 20 out of 21 and 7 out of 8 were correctly classified by the ELSSS system, respectively. One normal white matter tissue margin was detected in a high-grade tumor, and three normal tissue margins were detected in three low-grade tumors using spectroscopic data analysis and confirmed by histopathology. The spectral slopes were shown to be positive for normal white matter brain tissue and negative for normal gray matter and tumor tissues. Our results indicate that signs of spectral slopes may enable the discrimination of brain tumors from surrounding normal white matter brain tissue with a sensitivity of 93% and specificity of 100%.
We have used elastic light scattering spectroscopy to differentiate between malign and benign skin lesions. The system
consists of a UV spectrometer, a single optical fiber probe and a laptop. The single optical fiber probe was used for both
delivery and detection of white light to tissue and from the tissue. The single optical fiber probe received singly scattered
photons rather than diffused photons in tissue. Therefore, the spectra are correlated with morphological differences of the
cells. It has been shown that spectra of malign skin lesions are different than spectra of benign skin lesions. While slopes
of the spectra taken on benign lesions or normal skin tissues were positive, slopes of the spectra taken on malign skin
lesions tissues were negative. In vivo experiments were conducted on 20 lesions from 18 patients (11 men with mean age
of 68 ± 9 years and 7 women with mean age of 52 ± 20 years) applied to the Department of Dermatology and
Venerology. Before the biopsy, spectra were taken on the lesion and adjacent (approximately 1 cm distant) normal-appearing
skin. Spectra of the normal skin were used as a control group. The spectra were correlated to the pathology
results with sensitivity and specificity of 82% and 89%, respectively. Due to small diameter of fiber probe and limited
number of sampling (15), some positive cases are missed, which is lowered the sensitivity of the system. The results are
promising and could suggest that the system may be able to detect malignant skin lesion non-invasively and in real time.
The goal of this study was to differentiate the parts of lamb brain according to elastic scattering spectroscopy and detect the optical alterations due to coagulation. Cells and tissues are not uniform and have complex structures and shapes. They can be referred to as scattering particles. The process of scattering depends on the light wavelength and on the scattering medium properties; especially on the size and the density of the medium. When elastic scattering spectroscopy (ESS) is employed, the morphological alterations of tissues can be detected using spectral measurements of the elastic scattered light over a wide range of wavelengths. In this study firstly, the slopes of ESS spectra were used to differentiate the parts of lamb brains (brainstem, cerebellum, gray matter, white matter) in vitro in the range of 450 - 750 nm. Secondly, tissues were coagulated at different temperatures (45, 60, and 80 °C) and ESS spectra were taken from native and coagulated tissues. It was observed that as the coagulation temperature increased, the slope of the elastic scattering spectra decreased. Thus, optical properties of tissues were changed with respect to the change in nuclear to cytoplasmic ratio due to the water loss. Results showed that the slopes of ESS spectra in the visible range revealed valuable information about the morphological changes caused by coagulation.
We present a novel minimally invasive method to measure the concentration of photodynamic therapy drugs in real time. The method is based on measurements of backscattered and fluorescence light using a steady state fluorescence spectrometer. The ratio of the fluorescence to scattered light is found to be linearly proportional to the absorption coefficient of the photosensitizer. The fiber-optic probe used for the measurements has a small source-detector separation, therefore the measurements could be performed through the working channel of an endoscope.
As part of our ongoing efforts to understand the fundamental nature of light scattering form cells and tissues, we present data on elastic light scattering from isolated mammalian tumor cells and nuclei. The contribution of scattering from internal structures and in particular from the nuclei was compared to scattering from whole cells. Roughly 55 percent of the elastic light scattering at high- angles comes from intracellular structures. An upper limit of 40 percent on the fractional contribution of scattering form cells in tissue was determined. Using cell suspensions isolated from monolayer cultures at different stages of growth, we have also found that scattering at angles greater than about 110 percent was correlated with the DNA content of the cells. Based on model calculations and the relative size difference of nuclei from cells in different stages of growth, we argue that this difference in scattering results form changes in the internal structures of the nucleus. This interpretation is consistent with our estimate of 0.2 micrometers as the mean size of the scattering centers in cells. Additionally, we find that while scattering from the nucleus accounts for a majority of internal scattering, a significant portion must result from scattering off of cytoplasmic structures such as mitochondria.
Tissue strongly scatters light. Therefore, virtually all techniques for probing tissue with light are dependent on the scattering interactions of light with tissue. In particular, noninvasive optical methods for determining tissue morphology are dependent on light scattering. A fundamental understanding of what cellular features scatter light and of how changes internal cellular structures affect the measurement of light transport are needed. In this work, we describe some of the recent progress made towards understanding the basic mechanisms of light scattering in tissue.
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