Confocal Probe Research Articles

A Novel Semi-Autonomous Control Framework for Retina Confocal Endomicroscopy Scanning.

In this paper, a novel semi-autonomous control framework is presented for enabling probe-based confocal laser endomicroscopy (pCLE) scan of the retinal tissue. With pCLE, retinal layers such as nerve fiber layer (NFL) and retinal ganglion cell (RGC) can be scanned and characterized in real-time for an improved diagnosis and surgical outcome prediction. However, the limited field of view of the pCLE system and the micron-scale optimal focus distance of the probe, which are in the order of physiological hand tremor, act as barriers to successful manual scan of retinal tissue. Therefore, a novel sensorless framework is proposed for real-time semi-autonomous endomicroscopy scanning during retinal surgery. The framework consists of the Steady-Hand Eye Robot (SHER) integrated with a pCLE system, where the motion of the probe is controlled semi-autonomously. Through a hybrid motion control strategy, the system autonomously controls the confocal probe to optimize the sharpness and quality of the pCLE images, while providing the surgeon with the ability to scan the tissue in a tremor-free manner. Effectiveness of the proposed architecture is validated through experimental evaluations as well as a user study involving 9 participants. It is shown through statistical analyses that the proposed framework can reduce the work load experienced by the users in a statistically-significant manner, while also enhancing their performance in retaining pCLE images with optimized quality.

1463 Underwater Cap-Assisted Endoscopic Diagnosis and Treatment of Anal Intraepithelial Neoplasia

INTRODUCTION: Anal intraepithelial neoplasia (AIN) is a premalignant lesion which can progress to squamous cell carcinoma of the anus. Although rare, therate of anal canal cancer is rising within the United States and is associated with significant morbidity and mortality. Early detection of premalignant lesions is critical. AIN is frequently missed because detailed examination of the anal canal is difficult. Here we present two cases describing techniques to aid in the diagnosis and resection of AIN including endomicroscopy, distal attachment caps, and underwater endoscopy. CASE DESCRIPTION/METHODS: Patient 1 A 78-year-old woman with a history of HPV and AIN presented for follow up. A flexible sigmoidoscopy (FS) with a distal attachment cap was used to examine the anal canal and revealed two verrucous polypoid-appearing lesions just distal to the dentate line. Probe based confocal endomicroscopy of these lesions showed abnormal cellular structure and capillaries. The lesions were completely resected using a combination of biopsy forceps and cold snare. Both lesions were consistent with high-grade squamous AIN II-III. Repeat flexible sigmoidoscopy 6 months later showed no evidence of recurrence. Patient 2 A 63-year-old woman with a history of AIN with high grade dysplasia was referred to our center for resection. FS with a ESD cap attachment and water-immersion revealed a 5 mm villiform lesion (Figure 1). Using water-immersion the lesion appeared to float up off the mucosa. Probe based confocal endomicroscopy showed highly vascularized abnormal cellular architecture. The lesion was removed with cold forceps and pathology was consistent with low grade squamous AIN I. A follow up FS 1 year later showed a lesion consistent with AIN using narrow band imaging and near focus (Figure 2 and 3). The lesion was removed in piecemeal fashion with cold forceps underwater. Pathology again was consistent with low grade squamous AIN 1. DISCUSSION: Here we described techniques to improve identification and resection of AIN. Our approach is to use an ESD cap which helps stabilize the scope tip in the anal canal and spread mucosal folds to flatten areas of interest. Confocal probe based endomicroscopy has been described to take “optical biopsies.” Narrow band imaging and near focus of endoscopic images aids in the identification of lesions. Finally, water-immersion technique frequently causes AIN lesions to float up off the mucosa which aids in identification and resection.

Investigation and Improvement of Thermal Stability of a Chromatic Confocal Probe with a Mode-Locked Femtosecond Laser Source

An intentional investigation on the thermal stability of a mode-locked femtosecond laser chromatic confocal probe, which is a critical issue for the probe to be applied for long-term displacement measurement or surface profile measurement requiring long-time scanning, is carried out. At first, the thermal instability of the first prototype measurement setup is evaluated in experiments where the existence of a considerably large thermal instability is confirmed. Then the possible reasons for the thermal instability of the measurement setup are analyzed quantitatively, such as the thermal instability of the refractive index of the confocal lens and the thermal expansion of mechanical jigs employed in the probe. It is verified that most of the thermal instability of the measurement setup is caused by the thermal expansion of mechanical jigs in the probe. For the improvement of the thermal stability of the probe, it is necessary to employ a low thermal expansion material for the mechanical jigs in the measurement setup and to shorten the optical path length of the laser beam. Based on the analysis result, a second prototype probe is newly designed and constructed. The improved thermal stability of the second prototype probe is verified through theoretical calculations and experiments.

Evaporation of thin liquid film of single and multi-component hydrocarbon fuel from a hot plate

Evaporation of liquid film is of great importance, especially to the automotive industry, owing to its prevalence in automotive wet components. Thin liquid films usually deposit/spread in the inlet ports of engines using port fuel injection (PFI), at the nozzle tip of gasoline direct injection (GDI) engines, on the piston head of GDI and diesel engines, etc. It is important to predict the evaporation rate of these liquid films which have the thickness of the order of micrometers and may potentially lead to carbon deposits and consequent emissions. In this work, results of extensive experimental and numerical investigations of the evaporation of single and multi-component hydrocarbon film are presented. Liquid films are created by spraying the fuel on a smooth aluminum plate, and its evaporation pattern is studied at various temperatures of the plate. The film thickness reduction was monitored over time using a confocal point probe until the liquid film is completely evaporated. A one-dimensional numerical model is developed to predict the reduction of film thickness due to evaporation for single and multi-component fuels. The numerical results compared well with the measurements.

Measurement and Analysis of the Stepwise Curved Surface of Diffractive Optical Elements by a Constant Speed Confocal Probe

Diffractive optical elements (DOEs) play an important role in improving imaging quality and reducing system volume. The measurement of DOE surface topography is of great significance to the evaluation of DOE quality and the optimization of its manufacturing process. However, there are still some difficulties in measuring the large curvature and the large sag of curve-based DOEs. In this paper, considering the geometrical feature information and measurement problems of curve-based DOEs, a measurement method based on a confocal measurement principle for DOE measurement is proposed. The proposed measurement data processing method is verified by a high-precision motion axis system and the stability of an ultra-precision lathe. The results show that the proposed measurement method can reconstruct and accurately evaluate the three-dimensional surface topography of DOEs.

Controlling Doping Profiles in Enriched Semiconducting Carbon Nanotube Networks for Novel Energy Harvesting Electronic Devices

Carbon nanotubes have drawn lots of interest due to their unique chemical structure, which confers excellent thermal, mechanical and electronic properties. In particular, semiconducting single-walled carbon nanotubes (s-SWCNTs) are being seen as the most promising candidate for future optical, electronic, and energy conversion applications, due to their structure-tunable electronic bandgap. The demand for high-performance, flexibility, and low weight miniaturized and portable electronic devices and power sources, suggest s-SWCNTs as a strong candidate for such applications. However, the ability to exert fine control over the optical and electronic performance of s-SWCNT components in these devices is critical to their widespread applicability. One strategy toward achieving this control is through manipulation of the Fermi level of the semiconducting single-walled carbon nanotubes through various doping approaches. In this presentation, we will first illustrate the strategies we have developed to create controlled charge-carrier doping profiles in highly pure s-SWCNT networks. And we characterize the spatial distribution of the charge-carrier doping profile using confocal resonant Raman microscopy and probe the resulting variation in the electronic transport properties using field effect transistor measurements. We will subsequently discuss the incorporation of these tailored spatial charge-carrier doping profiles into energy harvesting device architectures and discuss the various factors that determine the observed device performance.

Correlative Confocal Raman and Scanning Probe Microscopy in the Ionically Active Particles of LiMn2O4 Cathodes.

In this contribution, a correlative confocal Raman and scanning probe microscopy approach was implemented to find a relation between the composition, lithiation state, and functional electrochemical response in individual micro-scale particles of a LiMn2O4 spinel in a commercial Li battery cathode. Electrochemical strain microscopy (ESM) was implemented both at a low-frequency (3.5 kHz) and in a high-frequency range of excitation (above 400 kHz). It was shown that the high-frequency ESM has a significant cross-talk with topography due to a tip-sample electrostatic interaction, while the low-frequency ESM yields a response correlated with distributions of Li ions and electrochemically inactive phases revealed by the confocal Raman microscopy. Parasitic contributions into the electromechanical response from the local Joule heating and flexoelectric effect were considered as well and found to be negligible. It was concluded that the low-frequency ESM response directly corresponds to the confocal Raman microscopy data. The analysis implemented in this work is an important step towards the quantitative measurement of diffusion coefficients and ion concentration via strain-based scanning probe microscopy methods in a wide range of ionically active materials.

A Method for Expansion of Z-Directional Measurement Range in a Mode-Locked Femtosecond Laser Chromatic Confocal Probe

A method is proposed to expand the Z-directional measurement range of a fiber-based dual-detector chromatic confocal probe with a mode-locked femtosecond laser source. In the dual-detector chromatic confocal probe, the Z-directional displacement of a measurement target is derived from the peak wavelength in the normalized intensity ratio from the two light intensities obtained by the two identical fiber detectors. In this paper, a new method utilizing the main-lobe and side-lobes of axial responses acquired from both the normalized intensity ratio Ia and the invert normalized intensity ratio In, which is the inverse of Ia, is proposed to obtain the seamless relationship between the peak wavelength and the Z-directional displacement of a measurement target. Theoretical calculations and experimental investigation are carried out to demonstrate the feasibility of the proposed measurement range expansion method.

Theoretical investigation on measurement range expansion of a femtosecond laser chromatic confocal probe

Theoretical investigation on measurement range expansion of a femtosecond laser chromatic confocal probe

Single Layer Graphene for Estimation of Axial Spatial Resolution in Confocal Raman Microscopy Depth Profiling.

Single layer graphene (SLG), with its angstrom-scale thickness and strong Raman scattering cross section, was adapted for measurement of the axial ( Z-direction) probe beam profile in confocal Raman microscopy depth-profiling experiments. SLG adsorbed to a glass microscope coverslip (SLG/SiO2) served as a platform for the estimation of axial spatial resolution. Profiles were measured by stepping the confocal probe volume through the SLG/SiO2 interface while measuring Raman scattering from the sample. Using a high numerical aperture (1.4 NA) oil immersion objective, axial profiles were derived from the graphene 2D vibrational mode and fit to a Lorentzian instrument response function (IRF). Subsequently, the Z-direction spatial resolution in depth-profiling studies of polymer interfaces was estimated through convolution of the Lorentzian IRF with a step function representing the ideal junction separating the phases of interest. In the study of a bipolar polymer membrane, confocal Raman depth profiles of the AEM/CEM (anion exchange membrane/cation exchange membrane) interface show that the transition region is broader than the limiting response and are consistent with roughness at the boundary on the order of a few micrometers. Using ClO4- as a Raman active mobile ion probe, application of self-modeling curve resolution (SMCR) to spectral data sets within a profile showed ClO4- ions track the spatial distribution of the AEM phase. Finally, in measurements on a liquid-solid interface formed between 1-octanol and a polydimethylsiloxane (PDMS) membrane, the IRF derived from fitting the experimental profile was slightly narrower than those obtained from profiling SLG, indicating the potential to use polymer-liquid interfaces formed from widely available materials and reagents for estimation of axial spatial resolution in confocal Raman depth-profiling.

Additive Benefit of Confocal Laser Endomicroscopy and Micro-Forceps Needle Biopsy in the Evaluation of a Mucinous Cystic Neoplasm

A 76 F presented with 6 months of abdominal pain and CT images of a pancreatic cyst. Multiple inconclusive EUS FNA procedures were performed at an outside hospital. We used a linear array echoendoscope to visualize the pancreatic parenchyma at our facility and then passed a confocal probe (AQ Flex) and micro-forceps (Moray needle) through a 19g needle (Cook Medical) into the cystic lesion. Initial on-site cytopathology evaluation of cyst fluid suggested atypical cells. Cyst fluid analysis subsequently demonstrated elevated CEA 8537 ng/mL and amylase 1788 U/L. The AQ flex probe was advanced along the cyst wall for CLE and the pattern demonstrated a single thick band suggestive of a mucinous cystic neoplasm (MCN). The micro forceps were advanced to that region and biopsy the cyst wall. Touch prep evaluation of the forceps biopsy and cell block analysis were positive for mucinous lesion. The patient received Cipro 400 mg IV during the procedure then discharged on 3-day oral course. She developed intense abdominal pain with syncope before outpatient resection. An outside hospital CT showed the pancreatic cyst with moderate amount of peripancreatic fluid with an intralesional linear density, possibly a stent or remnant of a biopsy apparatus. A distal pancreatectomy, splenectomy, left nephrectomy and left adrenalectomy was performed and revealed MCN with dysplasia measuring 8 cm with no invasive carcinoma. Margins were negative for tumor and no malignancy was identified in the lymph node sampled. Also obtained was the foreign body. At 2 week follow up, patient was doing well with no abdominal pain. We examined a pancreatic cyst case using EUS-FNA, CLE, micro-forceps needle biopsy and surgical pathology. This unique case report demonstrates the additive efficacy of EUS-FNA, CLE and micro-forceps biopsy for diagnosis. The case also describes a complication of retained foreign material within the cyst cavity; 19 g needle from the EUS device. Future prospective studies evaluating the added benefit of pancreatic cyst confocal and micro-biopsy are warranted. Additionally, it is important to note that many products utilized in clinical practice have not been designed for that specific purpose. The passage of the CLE probe and moray needle through the 19g needle at an appropriate echoendoscope position for cyst sampling may have resulted in breakage of the needle. Our institution now performs evaluations on devices after use as part of a post-procedure checklist.1382_A.tif Figure 1: CT of pancreas tail cystic lesion.1382_B.tif Figure 2: The dysplastic images show the mucinous cystic neoplasm with multilayered cells and nuclei that are coming off the basement membrane. There is also some nuclear pleomorphism as well. This is in contrast to the non-dysplastic image attached which shows a single layer of uniform cells. Note in both instances the ovarian type stroma underneath the epithelial layer, characteristic of a mucinous cystic neoplasm1382_C.tif Figure 3: FNA needle in the surgically resected pancreatic cyst specimen.

Application of a chromatic confocal measurement system as new approach for in-line wet film thickness determination in continuous oral film manufacturing processes

The key parameter of the oral film production process is the wet film thickness since it regulates the active pharmaceutical ingredient (API) content of the finished product. There is no general recommendation on how to adjust the gap height of the coating knife during the film manufacturing process to obtain the target content. Therefore, trial and error approaches are common to determine the surplus of drug for every newly developed formulation. This wastes resources, money and time and calls for an adequate in-line tool for wet film thickness measurement during the film manufacturing process to ensure consistent quality. In this work, a chromatic confocal optical probe was implemented into a continuous oral film manufacturing process on a pilot-scale coating bench. The optical probe allows a non-destructive and contactless wet film thickness measurement. The validation of the method showed good results. Linearity was demonstrated over a wide range of film thicknesses (R2 = 0.999). A good precision between different films was revealed by a coefficient of variation smaller than 2%. The robustness investigations showed that the method is applicable for transparent and non-transparent film forming masses. Furthermore, coloring agents, particles in the polymer mass and different viscosities do not influence the thickness measurement.

Ultrasound Acoustic Radiation Force Impulse imaging for High Intensity Focused Ultrasound focal spot localization.

Focal spot precise localization highly contributes to the accuracy and safety of High Intensity Focused Ultrasound (HIFU) therapies, and it is usually performed by means of Magnetic Resonance-Acoustic Radiation Force Impulse imaging (MR-ARFI). Acoustic Radiation Force Impulse imaging using ultrasound (US-ARFI) is herein proposed as a valid alternative to MR-ARFI for an accurate and non-destructive detection of the focal spot position during the pre-treatment phase. To this aim, a system composed of a HIFU transducer for generating the acoustic radiation force and a 2D confocal ultrasound probe for measuring the induced micro-displacement have been used. Then, an algorithm based on the Normalized Cross Correlation was implemented for the creation of a displacement map in which the highest displacement area, corresponding to the focal spot region, is unequivocally visualized. The feasibility of the proposed USARFI method for HIFU focal spot localization was successfully demonstrated in a tissue mimicking phantom model.

The effect of ceramic tribo-elements on friction and wear of smooth steel surfaces

The pin-on-disc dry sliding friction and wear experiments have been made on 42CrMo4 steel in contact with Si3N4, SiC, WC, Al2O3, and ZrO2 ceramic balls. The tests were carried out at sliding speeds of 0.16 m/s, 0.24 m/s, and 0.32 m/s. During the tests, the friction force was monitored as a function of time. Discs and balls wear was measured after the tests using a white light interferometer Talysurf CCI Lite and Altisurf 520 optical profilometer with a CL1 confocal probe. To decrease variations in the experimental results, during the tests, wear debris was continuously removed from the disc surfaces. It was found out that with Al2O3 counterpart the wear volume of the steel discs was the largest. However, the largest wear volume of the balls was observed for Si3N4 ceramic balls.

Confocal Raman Microscopy for in Situ Measurement of Phospholipid-Water Partitioning into Model Phospholipid Bilayers within Individual Chromatographic Particles.

The phospholipid-water partition coefficient is a commonly measured parameter that correlates with drug efficacy, small-molecule toxicity, and accumulation of molecules in biological systems in the environment. Despite the utility of this parameter, methods for measuring phospholipid-water partition coefficients are limited. This is due to the difficulty of making quantitative measurements in vesicle membranes or supported phospholipid bilayers, both of which are small-volume phases that challenge the sensitivity of many analytical techniques. In this work, we employ in situ confocal Raman microscopy to probe the partitioning of a model membrane-active compound, 2-(4-isobutylphenyl) propionic acid or ibuprofen, into both hybrid- and supported-phospholipid bilayers deposited on the pore walls of individual chromatographic particles. The large surface-area-to-volume ratio of chromatographic silica allows interrogation of a significant lipid bilayer area within a very small volume. The local phospholipid concentration within a confocal probe volume inside the particle can be as high as 0.5 M, which overcomes the sensitivity limitations of making measurements in the limited membrane areas of single vesicles or planar supported bilayers. Quantitative determination of ibuprofen partitioning is achieved by using the phospholipid acyl-chains of the within-particle bilayer as an internal standard. This approach is tested for measurements of pH-dependent partitioning of ibuprofen into both hybrid-lipid and supported-lipid bilayers within silica particles, and the results are compared with octanol-water partitioning and with partitioning into individual optically trapped phospholipid vesicle membranes. Additionally, the impact of ibuprofen partitioning on bilayer structure is evaluated for both within-particle model membranes and compared with the structural impacts of partitioning into vesicle lipid bilayers.

A chromatic confocal probe with a mode-locked femtosecond laser source

The high spatial coherence and high stability of a mode-locked femtosecond laser source make it ideal for chromatic confocal imaging. Nevertheless, the high non-smoothness of spectrum of the mode-locked laser source often restricts its application in chromatic confocal probes for a wide range of depth measurement. To eliminate the spectral non-smoothness of the mode-locked laser source, we propose a new chromatic confocal setup in such a way that the reflected laser beam is divided into two sub-beams which are then made to pass through two optical paths with different confocal settings where two identical fiber detectors are placed at the focal position and a defocus position, respectively, for acquiring two confocal signals. An axial response is then obtained from the intensity ratio of the two confocal signals for depth measurement. With the proposed confocal setup, we can expand the working spectral range of a mode-locked laser source to its whole spectrum. Theoretical and experimental investigation have revealed that the developed chromatic confocal probe with the specific mode-locked laser source employed in experiments has a measurement sensitivity of about −4 nm/μm, a depth measurement range of about 40 μm, and a depth resolution of better than 30 nm, respectively.

Assessing the feasibility of confocal laser endomicroscopy in solitary pulmonary nodules for different part of the lungs, using either 0.6 or 1.4 mm probes.

BackgroundMalignant solitary pulmonary nodules (SPN) have become more prevalent, with upper lobes predilection. Probe-based confocal laser endomicroscopy (pCLE) provides in-vivo imaging of SPN. However, the stiffness of the 1mm confocal probe (AlveoFlex) causes difficult accessibility to the upper lobes. A thinner 600μm probe designed for bile duct exploration (CholangioFlex) has the potential to reach the upper lobes.ObjectivesTo examine the accessibility of malignant SPNs in all segments of the lungs using either the 0.6mm or 1.4 mm probe and to assess the quality and inter observer interpretation of SPN confocal imaging obtained from either miniprobes.MethodsRadial(r)-EBUS was used to locate and sample the SPN. In-vivo pCLE analysis of the SPN was performed using either CholangioFlex (apical and posterior segments of the upper lobes) or AlveoFlex (other segments) introduced into the guide sheath before sampling. pCLE features were compared between the two probes.ResultsFourty-eight patients with malignant SPN were included (NCT01931579). The diagnostic accuracy for lung cancer using r-EBUS coupled with pCLE imaging was 79.2%. All the SPNs were successfully explored with either one of the probes (19 and 29 subjects for CholangioFlex and AlveoFlex, respectively). A specific solid pattern in the SPN was found in 30 pCLE explorations. Comparison between the two probes found no differences in the axial fibers thickness, cell size and specific solid pattern in the nodules. Extra-alveolar microvessel size appeared larger using CholangioFlex suggesting less compression effect. The kappa test for interobserver agreement for the identification of solid pattern was 0.74 (p = 0.001).ConclusionThis study demonstrates that pCLE imaging of SPNs is achievable in all segments of both lungs using either the 0.6mm or 1.4mm miniprobe.

Simulation of Raman scattering including detector parameters and sampling volume.

Raman spectroscopy can be employed to measure the chemical composition of a sample, which can in turn be used to extract biological information. The aim of this paper is to introduce an efficient simulation technique for Raman spectroscopy in turbid (scattering) media taking into account relevant detector parameters and the sampling volume. We simulate the process of photon motion in turbid media by means of the Monte Carlo (MC) method. The numerical simulation of Raman scattering consists of two stages: calculation of the photon fluence at each point of the medium and subsequent generation of the corresponding amount of Raman photons at each point. The developed model allows simulation of both confocal and optical fiber probe Raman setups. In more detail, the model efficiently simulates Raman signals for different single and multi-layer phantoms and geometries, including focused and collimated (i.e., the fiber-based case) excitation laser beams as well as different values for the numerical aperture and the excitation beam radius. In the future, our results offer the potential to improve the design of Raman systems for in vivo applications in biomedical research.

An on-machine error compensation method for an ultra-precision turning machine

On-machine error compensation (OMEC) is efficient at improving machining accuracy without increasing extra manufacturing cost, and involves the on-machine measurement (OMM) of machining accuracy and modification of program code based on the measurement results. As an excellent OMM technique, chromatic confocal sensing allows for the rapid development of accurate and reliable error compensation technique. The present study integrated a non-contact chromatic confocal probe into an ultra-precision machine for OMM and OMEC of machined components. First, the configuration and effectiveness of the OMM system were briefly described, and the relevant OMEC method was presented. With the OMM result, error compensation software was then developed to automatically generate a modified program code for error compensation. Finally, a series of cutting experiments were performed to verify the validity of the proposed OMEC method. The experimental results demonstrate that the proposed error compensation method is reliable and considerably improves the form error of machined components.

Handheld optical coherence tomography-reflectance confocal microscopy probe for detection of basal cell carcinoma and delineation of margins.

.We present a hand-held implementation and preliminary evaluation of a combined optical coherence tomography (OCT) and reflectance confocal microscopy (RCM) probe for detecting and delineating the margins of basal cell carcinomas (BCCs) in human skin in vivo. A standard OCT approach (spectrometer-based) with a central wavelength of 1310 nm and 0.11 numerical aperture (NA) was combined with a standard RCM approach (830-nm wavelength and 0.9 NA) into a common path hand-held probe. Cross-sectional OCT images and enface RCM images are simultaneously displayed, allowing for three-dimensional microscopic assessment of tumor morphology in real time. Depending on the subtype and depth of the BCC tumor and surrounding skin conditions, OCT and RCM imaging are able to complement each other, the strengths of each helping overcome the limitations of the other. Four representative cases are summarized, out of the 15 investigated in a preliminary pilot study, demonstrating how OCT and RCM imaging may be synergistically combined to more accurately detect BCCs and more completely delineate margins. Our preliminary results highlight the potential benefits of combining the two technologies within a single probe to potentially guide diagnosis as well as treatment of BCCs.