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Spectroscopy System (spectroscopy + system)
Selected AbstractsIncreased brain tumor resection using fluorescence image guidance in a preclinical modelLASERS IN SURGERY AND MEDICINE, Issue 3 2004Arjen Bogaards BSc Abstract Background and Objectives Fluorescence image-guided brain tumor resection is thought to assist neurosurgeons by visualizing those tumor margins that merge imperceptibly into normal brain tissue and, hence, are difficult to identify. We compared resection completeness and residual tumor, determined by histopathology, after white light resection (WLR) using an operating microscope versus additional fluorescence guided resection (FGR). Study Design/Materials and Methods We employed an intracranial VX2 tumor in a preclinical rabbit model and a fluorescence imaging/spectroscopy system, exciting and detecting the fluorescence of protoporphyrin IX (PpIX) induced endogenously by administering 5-aminolevulinic acid (ALA) at 4 hours before surgery. Results Using FGR in addition to WLR significantly increased resection completeness by a factor 1.4 from 68±38 to 98±3.5%, and decreased the amount of residual tumor post-resection by a factor 16 from 32±38 to 2.0±3.5% of the initial tumor volume. Conclusions Additional FGR increased completeness of resection and enabled more consistent resections between cases. Lasers Surg. Med. 35:181,190, 2004. © 2004 Wiley-Liss, Inc. [source] Development of an in situ polarization-dependent total-reflection fluorescence XAFS measurement systemJOURNAL OF SYNCHROTRON RADIATION, Issue 2 2001Wang-Jae Chun An in situ polarization-dependent total-reflection fluorescence X-ray absorption fine structure (PTRF-XAFS) spectroscopy system has been developed, which enables PTRF-XAFS experiments to be performed in three different orientations at various temperatures (273,600,K) and pressures (10,10,760,torr). The system consists of a measurement chamber and a preparation chamber. The measurement chamber has a high-precision six-axis goniometer and a multi-element solid-state detector. Using a transfer chamber, also operated under ultra-high-vacuum conditions, the sample can be transferred to the measurement chamber from the preparation chamber, which possesses low-energy electron diffraction, Auger electron spectroscopy and X-ray photoelectron spectroscopy facilities, as well as a sputtering gun and an annealing system. The in situ PTRF-EXAFS for Cu species on TiO2 (110) has been measured in three different orientations, revealing anisotropic growth of Cu under the influence of the TiO2 (110) surface. [source] Optical touch pointer for fluorescence guided glioblastoma resection using 5-aminolevulinic acid,LASERS IN SURGERY AND MEDICINE, Issue 1 2010Neda Haj-Hosseini MS Abstract Background and Objective Total tumor resection in patients with glioblastoma multiforme (GBM) is difficult to achieve due to the tumor's infiltrative way of growing and morphological similarity to the surrounding functioning brain tissue. The diagnosis is usually subjectively performed using a surgical microscope. The objective of this study was to develop and evaluate a hand-held optical touch pointer using a fluorescence spectroscopy system to quantitatively distinguish healthy from malignant brain tissue intraoperatively. Study Design/Materials and Methods A fluorescence spectroscopy system with pulsed modulation was designed considering optimum energy delivery to the tissue, minimal photobleaching of PpIX and omission of the ambient light background in the operating room (OR). 5-Aminolevulinic acid (5-ALA) of 5,mg/kg body weight was given to the patients with a presumed GBM prior to surgery. During the surgery a laser pulse at 405,nm was delivered to the tissue. PpIX in glioblastoma tumor cells assigned with peaks at 635 and 704,nm was detected using a fiber optical probe. Results/Conclusion By using the pulsed fluorescence spectroscopy, PpIX fluorescence is quantitatively detected in the GBM. An effective suppression of low power lamp background from the recorded spectra in addition to a significant reduction of high power surgical lights is achieved. Lasers Surg. Med. 42:9,14, 2010. © 2010 Wiley-Liss, Inc. [source] Effect of Photothermal Therapy on Breast Tumor Vascular Contents: Noninvasive Monitoring by Near-infrared Spectroscopy,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 4 2005Yueqing Gu ABSTRACT The goal of this study was to investigate the effect of photothermal laser irradiation on rat breast tumor (DMBA-4) vascular contents. An 805-nm diode laser was used in our experiment with a power density ranging from 0.32 to 1.27 W/cm2. The dynamic changes of oxygenated hemoglobin and total hemoglobin concentrations, ,[HbO2] and ,[Hb]total, in rat tumors during photothermal irradiation were noninvasively monitored by a near-infrared spectroscopy system. A multichannel thermal detection system was also used simultaneously to record temperatures at different locations within the tumors. Our experimental results showed that: (1) photoirradiation did have the ability to induce hyperthermic effects inside the rat breast tumors in a single exponential trend; (2) the significant changes (P < 0.005) of ,[HbO2] and ,[Hb]total in response to a low dosage of laser irradiation (0.32 W/cm2) have a single exponential increasing trend, similar to that seen in the tumor interior temperature; and (3) the increase in magnitude of ,[Hb]total is nearly two times greater than that of ,[Hb]total, suggesting that photoirradiation may enhance tumor vascular oxygenation. The last observation may be important to reveal the hidden mechanism of photoirradiation on tumors, leading to improvement of tumor treatment efficiency. [source] Low-temperature MBE-grown GaBiAs layers for terahertz optoelectronic applicationsPHYSICA STATUS SOLIDI (C) - CURRENT TOPICS IN SOLID STATE PHYSICS, Issue 12 2009Vaidas Pa, ebutas Abstract Gallium bismide arsenide epitaxial layers were grown by molecular-beam-epitaxy at low substrate temperatures and investigated for their suitability in terahertz optoelectronic applications. Optical pump-terahertz probe measurements on these layers have shown that carrier dynamics can be described using two characteristic times. The faster decay component has characteristic times shorter than 1 ps, whereas the slower component decays in several tens of picoseconds. Fitting the electron lifetimes dependence on optical excitation level the electron trapping cross-section and trap density were determined. The possible mechanism of carrier recombination was discussed. The photoconductive terahertz emitters and detectors made from GaBiAs layers have been manufactured and used in time-domain spectroscopy system with a signal bandwidth larger than 4.5 THz. (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Real-time measurement of cytosolic free calcium concentration in DEM-treated HL-60 cells during static magnetic field exposure and activation by ATPBIOELECTROMAGNETICS, Issue 3 2009Camilla Rozanski Abstract This study investigated whether glutathione depletion affected the sensitivity of HL-60 cells to static magnetic fields. The effect of Diethylmaleate (DEM) on static magnetic field induced changes in cytosolic free calcium concentration ([Ca2+]c) was examined. Cells were loaded with a fluorescent dye and exposed to a uniform static magnetic field at a strength of 0 mT (sham) or 100 mT. [Ca2+]c was monitored during field and sham exposure using a ratiometric fluorescence spectroscopy system. Cells were activated by the addition of ATP. Metrics extracted from the [Ca2+]c time series included: average [Ca2+]c during the Pre-Field and Field Conditions, peak [Ca2+]c following ATP activation and the full width at half maximum (FWHM) of the peak ATP response. Comparison of each calcium metric between the sham and 100 mT experiments revealed the following results: average [Ca2+]c measured during the Field condition was 53,±,2 nM and 58,±,2 nM for sham and 100 mT groups, respectively. Average FWHM was 51,±,3 s and 54,±,3 s for sham and 100 mT groups, respectively. An effect of experimental order on the peak [Ca2+]c response to ATP in sham/sham experiments complicated the statistical analysis and did not allow pooling of the first and second order experiments. No statistically significant difference between the sham and 100 mT groups was observed for any of the calcium metrics. These data suggested that manipulation of free radical buffering capacity in HL-60 cells did not affect the sensitivity of the cells to a 100 mT static magnetic field. Bioelectromagnetics 30:213,221, 2009. © 2008 Wiley-Liss, Inc. [source] Optimal methods for fluorescence and diffuse reflectance measurements of tissue biopsy samplesLASERS IN SURGERY AND MEDICINE, Issue 3 2002Gregory M. Palmer BS Abstract Background and Objective In developing fluorescence spectroscopy systems for the in vivo detection of pre-cancer and cancer, it is often necessary to perform preliminary testing on tissue biopsies. Current standard protocols call for the tissue to be immediately frozen after biopsy and later thawed for spectroscopic analysis, but this process can have profound effects on the spectroscopic properties of tissue. This study investigates the optimal tissue handling methods for in vitro fluorescence spectroscopy studies. Study Design/Materials and Methods The epithelial tissue of the Golden Syrian hamster cheek pouch was used in this study. Three specific experiments were carried out. First, the fluorescence properties of tissues in vivo and of frozen and thawed tissue biopsies were characterized at multiple excitation wavelengths spanning the ultraviolet-visible (UV-VIS) spectrum. Next, comparison of tissue fluorescence emission spectra in vivo, ex vivo (immediately after biopsy), and after the freeze and thaw process were systematically carried out at the excitation wavelengths corresponding to the previously identified fluorescence peaks. Lastly, intensities at the excitation and emission wavelength pairs corresponding to the fluorescence peaks were measured as a function of time after biopsy. Diffuse reflectance measurements over the UV-VIS spectrum were also made to evaluate the effects of oxygenation, blood volume, and scattering on the tissue fluorescence at these different excitation,emission wavelengths. Results This study indicates that the freezing and thawing process produces a significant deviation in intensity and lineshape relative to the in vivo fluorescence emission spectral data over the entire UV-VIS range between 300 and 700 nm. By contrast, examination of ex vivo emission spectra reveals that it closely preserves both the intensity and lineshape of the in vivo emission spectra except between 500 and 700 nm. The observed deviations can be explained by the diffuse reflectance measurements, which suggest increased hemoglobin deoxygenation and wavelength dependent changes in scattering in ex vivo tissues, and increased total hemoglobin absorption in the frozen and thawed samples. Furthermore, it was found that over a time window of 1.5 hours, spectroscopic changes brought about by degradation of the tissue due to biopsy or other factors are significantly smaller (10,30% variations in intensity) than those associated with the freezing and thawing process (50,70% decrease in intensity). Conclusions It was found that the effects of freezing and thawing on the fluorescence properties of tissue are greater than any changes brought about by degradation of tissue over a time frame of 90 minutes after biopsy. Performing ex vivo fluorescence measurements within a reasonable time window has the advantage of more accurately reproducing the clinically relevant in vivo conditions in the case of the hamster cheek pouch tissue. Therefore, in tissue biopsy studies, the tissue sample should ideally be maintained in an unfrozen state prior to measurement. Lasers Surg. Med. 30:191-200, 2002. © 2002 Wiley-Liss, Inc. [source] | ||||||||||