Effect of thermal damage on the in vitro optical and fluorescence characteristics of liver tissues

Thermal energy generated by radio-frequency current or other means may be employed in treating liver tumors by means of thermal coagulation when conventional resection is impossible. Currently, these thermal energy-based therapeutic procedures suffer from the lack of an adequate feedback control system, making it difficult to determine the optimal therapeutic endpoint. In this study, the potential of optical spectroscopy to provide such an objective endpoint for these procedures is presented. Freshly harvested canine liver samples were exposed to 50/spl deg/C, 60/spl deg/C, and 70/spl deg/C water baths for times ranging from 0 to 60 min. Transmission and reflectance were measured from each sample using an integrating sphere and the optical properties of each sample were accordingly derived. Excitation-emission matrices were recorded from the samples using a spectrofluorometer to identify the intrinsic fluorescence characteristics of native and thermally coagulated liver tissues. In addition, fluorescence and diffuse reflectance spectra were separately obtained from the samples prepared using a portable spectroscopic system. Results of this study show that fluorescence and optical properties of liver tissues exhibit clear and consistent changes through the thermal coagulation process. Specifically, the primary peak in the fluorescence spectra from liver tissues shifts from 480 nm in the native state to 510 nm in the fully coagulated state. In addition, a three- to fourfold increase in the absolute intensity of the diffuse reflectance spectra is observed upon complete coagulation of liver tissues. These dynamic spectral features indicate that fluorescence and diffuse reflectance spectroscopy may provide a direct measure of the biochemical and structural changes associated with tissue thermal damage in the liver.     

Investigation of near-infrared autofluorescence imaging for the detection of breast cancer

Detection of breast cancer in fresh tissue obtained from surgery is investigated using near-infrared autofluorescence imaging under laser excitation at 532 and 632.8 nm. The differences in intensity between the three main components of breast tissue (cancer, fibrous, and adipose) are estimated and compared to those obtained from cross-polarized light scattering images recorded under polarized illumination at 700 nm. The optical spectroscopic images for each tissue sample were subsequently compared with the histopathology slides. The experimental results indicate that the intensity of the near-infrared emission is considerably different in breast cancer compared to that of the adjacent nonneoplastic tissues (adipose and fibrous tissue). The experimental results suggest that 632.8-nm excitation offers key advantages compared to 532 nm excitation.     

光声、光热效应对早期乳腺癌的检测和治疗

提出了一种利用组织的光声、光热效应对早期乳腺癌检测和治疗的方法。采用蒙特卡罗仿真,模拟了近红外光到达人体乳腺组织时的能量沉积分布,仿真了由此产生的压力信号;再在肿瘤组织中加入了纳米金粒子,使近红外光在人体乳腺中产生的能量沉积聚集到肿瘤附近,从而在特定部位产生较高的温度。结果表明,光声信号的探测能有效的定位组织中肿瘤的位置,确定肿瘤大小、形状等特性,且在加入半径50 nm的纳米金粒子后,对靶组织的加热效率得到了提升,可提高特定组织光照后的温度,且对周边组织影响较小,基本可达到对早期乳腺癌的检测和治疗效果。     

Spectroscopic imaging and the characterization of the autofluorescence properties of human bronchus tissues using UV laser diodes

Ultraviolet laser diodes (UV-LD) were used for the excitation source of autofluorescence (AF) measurements and spectroscopic imaging of the AF originating from the human bronchus was obtained. The AF spectra from normal bronchus tissues were measured and a clear AF spectrum was obtained by using a short wavelength (400 nm) laser diode; the overlap of the AF signal and excitation source could be substantially eliminated. In order to study the origin of AF intensity deterioration from bronchus tissue due to the formation of tumor tissues, the fluorescence spectrum was measured for various AF substances under various conditions. The blue AF signal of elastin and NADH solutions, which could not be easily studied by conventional excitation light sources, as well as the green AF became weak by adding lactic acid. The AF spectrum was measured for 512/spl times/512 pixels and the intensity mapping as a function of emission wavelength was obtained. Two-dimensional information of the AF signal intensity distribution for a certain wavelength component was measured. The feature originating from a region as small as about 100 /spl mu/m could be recognized. Numerical calculations of the data were performed and precise features of the AF were revealed.     

Fluorescence Anisotropy of Cellular NADH as a Tool to Study Different Metabolic Properties of Human Melanocytes and Melanoma Cells

In this study, we wanted to see if fluorescence anisotropy could be used to detect changes in metabolism in cells with significant light scattering and absorption properties. Fluorescence anisotropy measurements of nicotinamide adenine dinucleotide (NADH) were performed with human melanocytes and melanoma cell lines. To demonstrate the feasibility of using fluorescence anisotropy for detecting metabolic changes, the electron transport chain was blocked using rotenone, inducing an accumulation of intracellular NADH. Total fluorescence increased in all cells as a result of rotenone treatment. Fluorescence anisotropy decreased in the rotenone-treated cells relative to the controls, suggesting an increased ratio of free to protein-bound NADH in the treated cells. In general, the fluorescence anisotropy of the melanocytes was significantly higher than that of the melanoma cell lines. Reflectance spectroscopy showed that the differences in fluorescence anisotropy between the cell types were not due to differences in scattering and absorption properties. Intrinsic cellular NADH fluorescence was experimentally extracted by ratioing polarized fluorescence to polarized reflectance. NADH binding, measured as the ratio of fluorescence intensity at 430 and 465 nm, showed more protein-bound NADH in the melanocytes than in the melanoma cells, consistent with the fluorescence anisotropy measurements.     

Experimental validation of a backpropagation algorithm forthree-dimensional breast tumor localization

To validate a new backpropagation algorithm for three-dimensional (3-D) tumor localization in breast tissue with a two-dimensional measurement, we performed experiments on breast phantoms using a heterodyne, frequency-domain photon migration system. The near-infrared (680 or 780 nm) laser diode used to provide illumination was intensity modulated at both megahertz (20-60 MHz) and kilohertz (10 kHz) frequencies. The breast phantoms were made of plastic resin with a variety of simulated tumors imbedded inside and then scanned with the system in a planar geometry. With megahertz modulation signals, both of the amplitude and phase of the transmitted light were used in the data reduction process, whereas with kilohertz modulation signals only the amplitudes were used for the reconstruction. In both cases, the backpropagation reconstruction algorithm was used to accomplish 3-D localization of the imbedded tumors. In all cases, the reconstructed locations for the hidden objects are in good agreement with the true values. Our current work demonstrates the possibility and potential of developing low-cost optical tomographic instruments     

An overview of activities at the Laser Biomedical Research Center

Research projects on laser heating and ablation and on spectroscopy of biological tissues are described. The discussion focuses on studies regarding microscopic laser light scattering of biological cells and structures, ablation of calcific tissue using pulsed HF laser radiation, and fluorescence and its use in diagnosing atherosclerosis. A specifically designed multifiber laser catheter constructed to collect tissue fluorescence spectra using fiber optics is described.     

Fluorescence lifetime imaging: an application to the detection ofskin tumors

A portable system based on fluorescence lifetime imaging has been developed and tested for the detection of skin tumors in humans. The Heme precursor δ-aminolevulinic acid, which promotes the preferential accumulation of the endogenous Protoporphyrin IX (PpIX) in proliferative tissues, is used as an exogenous marker to target the tumor, δ-aminolevulinic acid is topically administered to the patient 1 h before the measurement. Then, using a gated intensified camera, two or more images of the sample are acquired after different delays with respect to the excitation pulses. The images are processed in real time in order to calculate the spatial map of the fluorescence decay time of the sample. The localization of the tumor is based on the longer decay time detected in neoplastic tissues as a result of the stronger emission of PpIX, which has a long decay time, and the reduction in the short living natural tissue fluorescence     

Widely wavelength-tunable ultrashort pulse generation usingpolarization maintaining optical fibers

Characteristics of widely wavelength tunable ultrashort pulse generation using several types of polarization maintaining fibers have been experimentally analyzed. Using the diameter reduced type of polarization maintaining fibers, the wavelength tunable soliton pulse is generated from 1.56 to 2.03 μm. It is confirmed that the almost transform-limited 340-fs soliton pulse is generated at a wavelength of around 2 μm using a frequency-resolved optical gating method. When low-birefringence fibers are used, it is observed that the orthogonally polarized small pulse spectrum is trapped by the soliton pulse and is also shifted toward the longer wavelength side in the process of soliton self-frequency shift. The wavelength of the orthogonally polarized pulse spectrum is 40-50 nm longer than that of the soliton pulse, and the birefringence of the fiber is compensated by the chromatic dispersion. Finally, a polarization maintaining highly nonlinear dispersion-shifted fiber is used as the sample fiber. When the fiber input power is low, the wavelength-tunable soliton and anti-Stokes pulses are generated. As the fiber input power is increased, the pulse spectra are gradually overlapped and the 1.1-2.1 μm widely broadened supercontinuum spectra are generated by only 520 pJ pulse energy     

基于小波变换的脑电高阶奇异谱分析

奇异谱分析是数字信号分析的一种新方法。信号的奇异谱反映信号的奇异特征。但奇异谱分析方法是基于二阶统计的方法,反映的是信号时间上和空间上的一种线性相关关系。因而很难反映非线性信号内在的非线性关系。本文提出一种基于小波变换和高阶统计的奇异谱分析的新方法,并将其运用于正常脑电和癫痫患者的脑电信号分析中。实验结果表明,正常脑电和癫痫脑电的奇异谱有明显的不同。     

电沉积坡莫合金薄膜的组成、结构及磁性研究

采用电沉积技术与半导体材料相结合,在Ga As(100)单晶表面制备了表面光亮、致密、平整的坡莫合金薄膜。用X射线荧光技术与线偏振X射线吸收谱(XAS)确定了薄膜的组成为Fe21Ni79。磁光克尔效应(MOKE)测量结果表明样品薄膜具有典型的软磁性能。采用元素分辨的X射线磁性圆二色(XMCD)技术得到了合金薄膜中各元素的圆二色谱,利用加和定则计算了Fe和Ni的自旋磁矩和轨道磁矩,结果表明薄膜的磁性主要来源于Fe和Ni的自旋磁矩。     

Sensitivity of laser opto-acoustic imaging in detection of smalldeeply embedded tumors

Current imaging modalities fail to detect small tumors in the breast. Opto-acoustic tomography is a novel technique for early cancer detection with promising diagnostic capability. The experimental limit of sensitivity and maximal depth of the laser opto-acoustic detection for small model tumors located within bulk phantom tissue were studied. Two phantoms with optical properties similar to that of breast tissue in the near infrared spectral range were used in these studies: turbid gelatin slabs with the thickness of 100 mm and chicken breast muscle slabs with the thickness of up to 80 mm. Gelatin spheres with enhanced absorption coefficient relative to the background absorption and liver tissue were used to simulate small tumors. The experiments demonstrated the capability of laser optoacoustic imaging to detect and localize phantom tumors with the diameter of 2 mm at a depth of up to 60 mm within the gelatin phantoms and 3×2×0.6-mm piece of liver tissue within 80-mm chicken breast tissue. Theoretical studies on sensitivity of opto-acoustic detection at various diameters, depths of location, and absorption coefficients of small tumors were performed using the experimental data. Our results suggest that the opto-acoustic imaging may occupy a significant niche in early detection of cancer in the breast and other organs     

自适应小波压缩算法在连续录波装置中应用

针对连续录波海量数据的存储和对称电力系统故障持续时间短的运行特点,基于Clark变换和小波变换提出了一种自适应录波数据压缩技术以解决连续录波中的海量数据存储与存储设备安全和容量之间的矛盾.根据小波变换最大比例系数区分出正常数据与故障数据,对故障数据利用小波分解和自适应阈值处理同Lz77相结合的方法直接进行自适应小波压缩存储,对于非故障数据则在Clark变换基础上再进行自适应小波压缩存储,以提高数据压缩效率.应用Simulink仿真模拟输电线路的正常和故障运行2种情况对所提出的压缩算法的有效性进行验证.仿真数据表明所提出的压缩方法比不进行数据区分压缩算法的压缩率更高,可有效地解决连续录波器中海量数据的存储与设备容量之间的矛盾.     

电晕放电中光谱特性的分析及实验程序设计

为了解电晕放电中光的光谱特性和通过光辐射光谱的测量分析电晕放电的规律,介绍了利用光栅单色仪、锁相放大器等设备检测交流电晕放电光谱特性的实现方法和软件设计并分析了光谱特性。所测光谱范围190.0～900.0nm,光谱峰值波长集中在200.0～400.0nm,主要有297.9、316.8、338.0、367.8、380.0nm等,属紫外光谱,分析得出特征波长上光谱峰值的大小可作为判断电晕放电强度的参考量,工程上可利用200.0～320.0nm波段内紫外光避开日光紫外线对电晕放电紫外线的干扰。     

The effect of heat treatment temperature on phase formation and luminescence properties of calcium magnesium silicate glass-ceramics doped with Sm2O3

Abstract

The transparent glasses of CaO-MgO-Al₂O₃-SiO₂-ZnO system doped with Sm₂O₃ was prepared by conventional melt-quenching method. The obtained glasses were heat treated at a suitable temperature (875?°C–920?°C for 2?h) identified by differential thermal analysis (DTA). Phase formation and microstructure of glass-ceramics were characterized by X-ray diffraction and scanning electron microscopy, respectively. The optical transmission spectra were recorded by UV-Vis spectrophotometer in the wavelength range between 350 and 1000?nm. It was found that the increase in heat treatment temperature reduced the transparency of the glass-ceramics. The luminescence properties were identified by fluorescence spectroscopy. The excitation spectra of Sm₂O₃ doped CaO-MgO-Al₂O₃-SiO₂-ZnO glass-ceramic samples are in wavelength range of 550–750?nm and the emission spectra exhibited a strong orange-red luminescence composed of 562, 599 and 654?nm under excited at 402?nm. The results of XRD studies revealed the occurrence of diopside (CaMgSi₂O₆) and akermanite (Ca₂MgSi₂O₇) phases. The increasing of heat treatment temperature has no effect on the shift of emission spectra.     

Choline metabolism in breast cancer;2H-,13C- and31P-NMR studies of cells and tumors

Choline metabolism in breast cancer cells and tumors has been investigated by multinuclear NMR in order to provide the biochemical basis for the presence of high phosphocholine in breast carcinoma relative to benign breast tumors and normal breast tissue. Choline was found to be transported into MCF7 human breast cancer cells and rapidly phosphorylated to phosphocholine which was then accumulated in the cells to high concentrations. The increased level of phosphocholine did not affect the rate of synthesis of phosphatidylcholine, indicating tight regulation of this pathway. The incorporation of [l,2-¹³C]choline (100 μM) into phosphocholine and phosphatidylcholine after 24 h was 69.5 and 36% of the total respective pools. Incorporation of²H₉-choline to tumors implanted in nude mice was achieved by infusing the deuterated choline to the blood circulation. The metabolism of deuterated choline was then monitored by²H localized MRS. The blood level of choline before the infusion was 58.6 ± 10.3 μM (measured by¹H-NMR of plasma samples) and increased ～ 5-fold during the infusion (measured by²H-NMR). This increase in the blood level resulted in a gradual increase of a signal at 3.2 ppm due to deuterated choline metabolites. It appears that the increased availability of choline in the blood circulation leads to accumulation of phosphocholine in the tumors by the same mechanism as in the cells. © 1998 Elsevier Science B.V. All rights reserved.     

Optimization of 635-nm tensile strained GaInP laser diodes

The authors measure the combined affect of strain and well width on the gain and recombination mechanisms in 635-nm laser structures containing three combinations of tensile strain and well width of 0.5%/10 nm, 0.6%/12.5nm, and 0.7%/15nm using the segmented contact method. They find an improvement in the intrinsic properties with increasing strain but the dominant effect in device performance is an extrinsic effect-the overall radiative efficiency, which is found to be less than 30% for all three samples even at 200 K. The authors attribute this to nonradiative recombination within the quantum well. The intrinsic gain-spontaneous current density characteristics of all three samples exhibit similar tangential gain parameters and a decreasing transparency current density from 116 to 87 to 83 Acm/sup -2/ with increasing strain and well width. They show that the reduction occurs because of a reduction in the TE polarized spontaneous recombination due to the increased splitting of light and heavy hole subbands. The quasi-Fermi level separation required to achieve a fixed value of gain is insensitive to the particular strain/well width combination. The authors use a microscopic laser theory to model the behavior of a larger range of combinations of tensile strain and well width than were examined experimentally, having first demonstrated that the model correctly describes the experimental gain spectra of the only sample exhibiting appreciable gain in both TM and TE polarizations. The calculated data suggest that using still larger values of strain and well width produces no further benefit in performance.     

In Vivo Detection of Gold Nanoshells in Tumors Using Diffuse Optical Spectroscopy

This study demonstrates the use of diffuse optical spectroscopy (DOS) for the noninvasive measurement of gold nanoshell concentrations in tumors of live mice. We measured the diffuse optical spectra (500-800 nm) using an optical fiber probe placed in contact with the tissue surface. We performed in vitro studies on tissue phantoms illustrating an accurate measurement of gold-silica nanoshell concentration within 12.6% of the known concentration. In vivo studies were performed on a mouse xenograft tumor model. DOS spectra were measured at preinjection, immediately postinjection, 1 and 24 h postinjection times, and the nanoshell concentrations were verified using neutron activation analysis.     

Quantification of Choline-containing Compounds in Malignant Breast Tumors by 1H MR Spectroscopy Using Water as an Internal Reference at 1.5 T

The quantification of choline-containing compounds (Cho) in breast tumors by proton MR spectroscopy (¹H-MRS) has been of great interest because such compounds have been linked to malignancy. In this study, an internal reference method for the absolute quantification of Cho metabolite in malignant breast tumors was presented using a clinical 1.5 T scanner. We performed in vitro measurements to examine the accuracy of absolute quantification using four phantoms of known choline chloride concentrations. There was a high correlation between the calculated concentrations by MRS and the known concentrations (r ² > 0.98). We applied the technique to in vivo breast study conducted on 45 patients with biopsy-confirmed breast cancer. After T ₁ and T ₂ relaxation times were corrected, the Cho levels in this work had a range of 0.76 – 21.20 mmol/kg from 34 MR spectra of 32 patients with malignant breast lesions. This result was rather consistent with the previously published value (i.e., 1.38 – 10 mmol/kg, Bolan et al. in Magn Reson Med 50:1134–1143, 2003). Therefore, we conclude that the internal method using the fully relaxed water as a reference could be used for quantifying Cho metabolite accurately in breast cancer patients using a clinical 1.5 T scanner.     

Intraoperative application of optical spectroscopy in the presenceof blood

A simple but effective method of spectral processing was developed to minimize or remove the effects of the presence of superficial blood on tissue optical spectra and, hence, enhance the performance of optical-spectroscopic-based in vivo tissue diagnosis and surgical guidance. This spectral-processing algorithm was developed using the principles of absorption-induced light attenuation wherein the ratio of fluorescence intensity (F) and the hth power of diffuse reflectance intensity (Rd) at a given emission wavelength λ_m is immune to spectral distortions induced by the presence of blood on the tissue surface. Here, the exponent h is determined by the absorption coefficients of whole blood at the excitation and emission wavelengths. The theoretical basis of this spectral processing was verified using simulations and was experimentally validated. Furthermore, the optical spectra of brain tissues collected in vivo was processed using this algorithm to evaluate its impact on brain tissue differentiation using combined fluorescence and diffuse reflectance spectroscopy. Based on the simulation, as well as experimental results, it was observed that using F/Rd^h h can effectively reduce or remove spectral distortions induced by superficial blood contamination on tissue optical spectra. Thus, optical spectroscopy can also be used intraoperatively for applications such as surgical guidance of tumor resection