Optical Diagnostic Tools Research Articles

Calibration of laser tomography as a new optical diagnostic tool applied to dosimetric polymer gels

Numerous medical applications, as radiotherapy for example, require accurate and reproducible three-dimensional dose measurements with high spatial resolution. A solution of great interest and which has been exploited for many years is the use of dosimetric gels based on different physico-chemical principles, as Fricke’s gels or polymer gels. Fricke’s gels take advantage of the oxidation of ferrous ions in ferric while polymer gels are the result of the synthesis of polyacrylamide hydrogel from monomer and cross-linking agent. Fricke’s gels have particular limitations not encountered with polymer gel dosimeters: the time delay between irradiation and measurement must be reduced in order to limit the diffusion of ferric ions which may remove the spatial dose information. That’s why, during the past decade, many compositions of polymer gels have been studied (PAG, MAGIC,…), elaborated and even commercialized (BANG gels). However the gel composition remains of great interest regarding its physical properties. In this work, the authors propose a new optical diagnostic tool more flexible and less expensive in comparison with existing techniques like magnetic resonance imaging (MRI) and Optical-CT. This technique is based on light scattering behaviour occurring in an irradiated polymer gel (note that light scattering in Fricke’s gels is very feeble, the latter being essentially absorbant).

Optical characterization of Zn0.96Be0.04Se and Zn0.93Mg0.07Se mixed crystals

A detailed optical characterization of Zn0.96Be0.04Se and Zn0.93Mg0.07Se mixed crystal samples grown by the modified high-pressure Bridgman method has been carried out via photoluminescence (PL), contactless electroreflectance (CER), and photoreflectance (PR) in the temperature range of 15–400 K. With these optical diagnostic tools we observed features originating from exciton emission, an edge emission due to recombination of shallow donor-acceptor pairs (DAPs), and a broad band related to recombination through deep-level defects, as well as band-edge and spin-orbit splitting critical points interband transitions in CER and PR experiments. The optical properties of these two mixed crystals are compared. Our comparative study revealed that the beneficial effect of beryllium (Be) incorporation is superior to that of magnesium (Mg), in the sense that a Be-containing ternary alloy resulted in better crystalline quality with more intense excitonic emission line and weaker DAPs and deep-level defect-related bands. The peak positions of the excitonic emission lines in the PL spectra correspond quite well to the energies of the fundamental transitions obtained by means of electromodulation spectra. The parameters that describe the temperature dependence of the fundamental and spin split-off band gaps, and the broadening function of the band-edge excitons, are evaluated and discussed.

Design Optimization of a Novel pMDI Actuator for Systemic Drug Delivery

Pressurized metered dose inhalers (pMDIs) are the most widely prescribed and economical respiratory drug delivery systems. Conventional pMDI actuators-those based on "two-orifice-and-sump" designs-produce an aerosol with a reasonable respirable fraction, but with high aerosol velocity. The latter is responsible for high oropharyngeal deposition, and consequently low drug delivery efficiency. Kos' pMDI technology is based on a proprietary vortex nozzle actuator (VNA), an innovative actuator configuration that seeks to reduce aerosol plume velocity, thereby promoting deep lung deposition. Using VNA development as a case study, this paper presents a systematic design optimization process to improve the actuator performance through use of advanced optical characterization tools. The optimization effort mainly relied on laser-based optical diagnostics to provide an improved understanding of the fundamentals of aerosol formation and interplay of various geometrical factors. The performance of the optimized VNA design thus evolved was characterized using phase Doppler anemometry and cascade impaction. The aerosol velocities for both standard and optimized VNA designs were found to be comparable, with both notably less than conventional actuators. The optimized VNA design also significantly reduces drug deposition in the actuator as well as USP throat adapter, which in turn, leads to a significantly higher fine particle fraction than the standard design (78 +/- 3% vs. 63 +/- 2% on an ex valve basis). This improved drug delivery efficiency makes VNA technology a practical proposition as a systemic drug delivery platform. Thus, this paper demonstrates how advanced optical diagnostic and characterization tools can be used in the development of high efficiency aerosol drug delivery devices.

Laser effect on the 248 nm KrF transition using heavy ion beam pumping

In December 2005 the first successful operation of a UV excimer laser pumped with a heavy ion beam was demonstrated at GSI. It was the first experiment in which the specific power deposition was sufficient to overcome laser threshold for a UV excimer scheme. The well known KrF * excimer laser line at λ = 248 nm has been chosen for this experiment, because the wavelength is short, but still in the range of usual optical diagnostic tools and the emitted light can propagate in air without attenuation. A bunch compressed U + 73 238 beam with a particle energy of 250 MeV / u and about 110 ns pulse duration (FWHM) was used for this experiment. Single pulses of a beam intensity up to 2.5 × 10 9 particles per bunch were focused into the laser cell along the cavity axis. Compact spectrometers, high speed UV-photodiodes and gated CCD-cameras were used for diagnostics of the spontaneous and stimulated emission. As a main result of the experiment laser effect on the 248 nm KrF * excimer laser line has been obtained and verified by temporal and spectral narrowing of the laser line as well as the threshold behaviour and exponential growth of intensity with increasing pumping power. In summary it could be shown that the pumping power of the heavy ion beam at GSI is now sufficient to pump short wavelength lasers. It is planned to extend laser experiments in near future to the VUV range of the spectrum ( λ < 200 nm ) .

Identification and Imaging of the Nerves Responsible for Erectile Function in Rat Prostate,In Vivo, Using Optical Nerve Stimulation and Optical Coherence Tomography

The cavernous nerves on the prostate surface are responsible for erectile function. Optical diagnostic tools such as optical coherence tomography and laser nerve stimulation may assist in the identification, imaging, and preservation of these microscopic nerves during prostate cancer surgery, and thus, help preserve sexual function after surgery. The feasibility of noncontact laser stimulation of the cavernous nerves is demonstrated in an in vivo rat prostate model with comparison to conventional electrical nerve stimulation. High-resolution optical coherence tomographic images of the nerves are also obtained and compared with histology. These optical technologies may be suitable as surgical guidance tools during laparoscopic and robotic nerve-sparing prostate cancer surgery.

Investigation of pinch dynamics in plasma-focus discharges by means of fast-streak-and fast-frame-cameras

In order to investigate the Plasma-Focus (PF) pinch dynamics within the large PF-1000 facility the use was made of fast streak-and frame-cameras operated as the routine optical diagnostic tools. They enabled images of a current-sheath (CS) layer and the PF-pinch to be recorded within the visible range (VR) at chosen instants of the investigated PF-discharges. The measurements were carried out end-and side-on the PF-1000 electrode system under different experimental conditions. For the temporal synchronization of both cameras with the chosen phases of the PF discharge, we used current derivative (dI=dt) waveforms and X-ray signals recorded for each shot. During the described PF-1000 experiments, we performed also other complimentary measurements. Particular attention was paid to studies of current-and voltage-waveforms of the investigated discharges, to a comparison of the total neutron yields measured by means of silver activation counters, and to the analysis of time-resolved neutron-and X-ray-signals recorded with several scintillation detectors. Results of the observations carried out with the fast streak-and frame-cameras, which were compared with other experimental studies, allowed better understanding of all the PF-discharge phases to be achieved. In particular, the correlation of different quantum-and corpuscular-radiation pulses, which has influence on the total fusion-neutron yield, has been analyzed.

Laser Induced Breakdown Spectroscopy for Quality Control in Pharmaceuticals Industry

A description of the basic principal and experimental approach of the laser induced breakdown spectroscopy (LIBS), a fast emerging optical diagnostic tool, is followed by the evaluations of this technique for the quality control in pharmaceutical industry. Four popular antacid products available in tablet form have been investigated for quantitative analysis of the active/inactive ingredients as well as for impurities. The calibration curves prepared show a good linearity. Elements not listed in the product labels have been identified and quantified. Also potential of LIBS to monitor intrabatch uniformity has been investigated.

Telescience and interferometric metrology on the international space station

Scientific experiments performed in space require real-time control by the scientists on earth, i.e. Telescience/Teleoperation. In fluid science research, non-invasive optical diagnostic tools help to gain a better understanding of phenomena within transparent media. During the last years, electronic cameras started to take over the role of quantitative imaging from photographic imaging. For that purpose cameras must offer at least 1 k × 1 k spatial resolution, 8 bit pixel depth and 33 ms (30 fps) time resolution. This results in data rates (240 Mbps) far beyond the downlink capacities of typical carriers for scientific payloads. A double rack on the International Space Station (ISS), e.g. gets only 2 Mbps continuously. This paper concentrates on the compressibility of interferometric image data for Telescience. In particular, a solution is presented for Electronic Speckle Pattern Interferometry ( ESPI), one of the interferometers, e.g. planned for the Fluid Science Laboratory (FSL) on ISS. Pre-tests had shown that ESPI raw images could hardly be compressed, i.e. by a factor 1–1.5 only. But a factor of 60 is at least required to allow Telescience with an image sequence of 15 fps (120 Mbps), still providing a good qualitative impression about the spatial and temporal behaviour of an experiment. This paper provides answers concerning qualitative imaging with ESPI in addition to Shearing Interferometry and Holographic Interferometry.

Comprehensive Characterization of a Sooting Laminar Methane‐Diffusion Flame Using Different Laser Techniques

The potential of a combination of optical diagnostic tools is demonstrated for the characterization of a sooting laminar methane diffusion flame. Time‐resolved laser‐induced incandescence, Rotational CARS spectroscopy, spontaneous Raman scattering, and the laser‐induced fluorescence technique have been applied to measure the soot primary particle size and volume concentrations and the concentration of species in the surrounding gas.

From an Integrated Biochip Detection System to a Defensive Weapon Against the SARS-CoV Virus: OBMorph

AbstractIn this paper, an integrated multifunctional biochip detection system, which we call “OBMorph“, are presented. This unique system integrates several optoelectronic-based biological diagnostic tools such as an ellipsometer, a laser Doppler vibrometer/interferometer, a SPR (surface plasmon resonance) analyzer, an interference microscope, a photon tunneling microscope, an optical coherence tomography unit and a confocal scanning microscope. This OBMorph system, useful as a powerful optical metrology diagnostic tool, can be used at the beginning of sensor chip fabrication, on to signal detecting and monitoring, and to the final biological analysis. The principles and experimental results of this multifunctional biochip detection OBMorph system are presented.In addition, an innovative SARS (Severe Acute Respiratory Syndrome) virus denaturing chemical compound that was derived using the OBMorph system to study biolinker fabrication in biochips, are discussed. Several testing strategies are presented herein which proves the effectiveness of the new chemical compound, biochip technology in denaturing the SARS virus. Analysis under an atomic force microscope confirms the actual breaking down of the virus treated by the chemical compound. The fundamentals of how the chemical compound denatures the virus and renders it toxicity useless, is based on principles of nanotechnology and bio-mechanics. Results from preliminary studies show that this denaturing principle can be also effective against other deadly viruses and even bacteria. Some design strategies and innovative working mechanisms derived from study of this chemical compound which can denature the SARS-CoV, are also discussed.

Raman spectral mapping in the assessment of axillary lymph nodes in breast cancer.

This paper is the first reported description of Raman Spectroscopy in the assessment of axillary lymph nodes in breast cancer patients. Raman Spectroscopy is an inelastic scattering spectroscopic technique appropriate for the assessment of unprocessed complex biological tissues. Spectra represent biochemical signatures of the tissue under scrutiny. The described method of Raman spectral mapping produces false-color spectral images of lymph node sections. These can be compared with standard histopathology slides and white light images of nodal tissue. This method has the potential to allow the detailed biochemical assessment of heterogeneous lymph node features, and to contribute towards the development of an optical diagnostic tool for use in a clinical setting.

Research on high pressure cryogenic combustion

Due to their high specific impulse, Oxygen/Hydrogen systems are often used to increase launcher performance and will probably continue to be the preferred option for the next decades. In order to get insight into complex processes involved in the combustion of such propellants, research efforts have been conducted in both France and Germany including theoretical and experimental activities. This article deals with recent progress achieved by research teams from both countries in high pressure Oxygen/Hydrogen (O 2/H 2) combustion systems. In France, the research program was conducted in the framework of the GDR group including Snecma Moteurs-Rocket Engine Division, Centre National d'Études Spatiales (CNES), Centre National de la Recherche Scientifique (CNRS) and ONERA. In Germany, research was conducted in the framework of the national technology program “TEKAN” involving universities, DLR and Astrium. A close cooperation between teams was made possible through a Memorandum of Understanding (MoU) on research on high pressure cryogenic combustion. First, general design issues of liquid propellant engines are addressed, demonstrating a clear need for a new approach in engine development taking into account the complex chemical and physical processes in rocket engines. A brief description about the organization of the research programs is followed by a short presentation of the test facilities and the experimental setup's in use. Examples of experimental as well as numerical achievements applying sophisticated optical diagnostic tools are discussed and finally, the paper summarises the results achieved so far and addresses the questions still open.

Quantitative temperature imaging in gas-phase turbulent thermal convection by laser-induced fluorescence of acetone

In this paper, an acetone planar laser-induced fluorescence (PLIF) technique for nonintrusive temperature imaging is demonstrated in gas-phase (Pr = 0.72) turbulent Rayleigh–Bénard convection at Rayleigh number Ra = 1.3×105. The PLIF technique provides quantitative spatially correlated temperature data without the flow intrusion or time lag associated with physical probes, and without the significant path averaging that plagues most optical heat-transfer diagnostic tools, such as the Mach–Zehnder interferometer, thus making PLIF an attractive choice for quantitative thermal imaging in easily perturbed, complex three-dimensional flow fields. The "instantaneous" (20-ns integration time) thermal images presented have a spatial resolution of 176×176×500 µm and a single-pulse temperature measurement precision of ± 2.5 K, or 2.5% of the total temperature difference. These images represent a two-dimensional slice through a complex three-dimensional flow, allowing for thermal structure of the turbulence to be quantified. Statistics such as the horizontally averaged temperature profile, root-mean square (rms) temperature fluctuation, two-point spatial correlations, and conditionally averaged plume structures are computed from an ensemble of 100 temperature images. The profiles of the mean temperature and rms temperature fluctuation are in good agreement with previously published data, and the results obtained from the two-point spatial correlations and conditionally averaged temperature fields show the importance of large-scale coherent structures in this turbulent flow.

Diagnostic of an ionized gas by recording linearly polarized radiation

The degree of linear polarization of radiation from an ionized gas is calculated analytically. The analytical results on the resonant transition in Al XII atoms agree (to within 4%) with the numerical results obtained from the ATOM code. The applicability of the analytic expressions derived to the analysis of the degree of linear polarization of radiation from this atomic transition and the related excitation cross section is discussed. The plots of the degree of linear polarization of radiation from an ionized gas as a function of the electron parameters are presented. The question of whether the spectropolarimetry can provide an independent optical diagnostic tool is discussed.

Digital holography as a versatile optical diagnostic method for microgravity experiments

Microgravity experiments require robust, reliable and simple measurement techniques that provide the same capabilities as on-ground laboratory applications. Interferometric measurement techniques such as conventional holographic interferometry using hologram plates have several disadvantages in microgravity research - a time-consuming development process and additional experimental effort for a quantitative evaluation of interference patterns, for example. Digital holography is an advanced optical diagnostic tool for surface deformation analysis, measurement of refractive index variations and particle analysis in transparent media: Fresnel holograms are stored electronically and the reconstruction is performed by numerical methods. Due to the reconstruction process a numerical representation of the recorded wavefront can be evaluated including amplitude and phase. This paper reports on applications of digital holography to particle analysis and to the detection of refractive index variations within transparent media. The properties and advantages of this technique for microgravity experiments with respect to other techniques are discussed.

Detection of transplant vasculopathy in a rat aortic allograft model by fluorescence spectroscopic optical analysis.

Transplant vasculopathy is a leading cause of late cardiac graft loss. We have examined laser-induced fluorescence (LIF) spectroscopy as an optical diagnostic tool for detection of intimal plaque development and inflammatory cellular invasion in a rat model of aortic allograft transplant. Infrarenal aortic segments were transplanted from Lewis to Sprague Dawley rats. A range of vasculopathy development was produced by treatment with a viral anti-inflammatory protein. LIF spectra were recorded from the intima of aortic implants at 28 days. Fluorescence intensity was analyzed for correlation with vasculopathy development. Significant differences in LIF intensity at 400-450 nm (P < or = 0.05 by ANOVA) were detected. LIF emission was correlated with plaque growth (R2 = 0.980), vessel narrowing (R2 = 0.964), and cellular invasion (R2 = 0.971) by regression analysis. LIF optical analysis provides a nontraumatic diagnostic approach for detection of atherosclerosis prior to cardiac transplant or during development of vasculopathy after transplant.

Design and demonstration of a high-speed, multichannel, optical-sampling oscilloscope

Free-space digital optical systems have demonstrated the capability to provide thousands of optical connections between optoelectronic chips. This dense concentration of channels creates substantial challenges in monitoring individual connections for diagnostic purposes without compromising performance. Prom the concept of stroboscopic techniques, we have designed and constructed a multichannel optical diagnostic tool that operates analogously to an electronic-sampling oscilloscope. The tool is economically constructed by the use of commercially available video cameras and video-enhanced personal computers. An integrated software application operates the tool and displays multiple-channel waveforms. We demonstrate the oscilloscope-sampling optical waveforms of a two-dimensional optoelectronic modulator array operating at data rates from 0.5 to 4 Gbits/s.

A new method for temperature evaluation in a nitrogen discharge

The purpose of this work is to propose a powerful optical diagnostic tool for evaluating the rotational and vibrational temperatures of a nonequilibrium N2 plasma. Using a two-dimensional detection set-up for emission spectroscopy and the construction of synthetic spectra of the second positive system and the first negative system of nitrogen emission, temperature evaluation was performed by comparing experimental and simulated spectra.

Digital holographic interferometry in high-speed flow research

A dual reference beam, plane wave, digital holographic interferometric system has been developed. It has also been applied as a non-intrusive optical diagnostic tool to a high speed flow. Quantitative density data has been extracted automatically by first generating phase-stepped interferograms. These were then digitized via a charge coupled device (CCD) camera and digitally post-processed within the memory of a computer. The results obtained have mapped an instantaneous 3-D density distribution of an unsteady flow field onto a 2-D projection plane. They show quantitatively the interaction between a shock wave and a turbulent boundary layer. A description has also been made showing how the dual reference beam technique can be extended to provide a quantitative density measurement of turbulent and unsteady flow structures.