In tumor resection surgery, the entire tumor must be removed to prevent local recurrence of cancer. To achieve effective and successful tumor resection surgery, an intraoperative examination is performed for quick decision-making during the surgical process. Examination of frozen sections is a common method, but it has limitations that it requires time-consuming tissue processing procedures which leads to interpretation errors. Photoacoustic microscopy (PAM) with ultraviolet (UV) laser is a promising intraoperative surgical margin assessment method that provides depth-resolved and label-free imaging of cell nuclei without sectioning and staining. Despite these advantages, conventional PAM still has limited imaging speed that does not allow real-time imaging, because it achieves the volumetric images by raster scanning using 2-axis step motors. To overcome the limitation, we developed a high-speed reflection-mode OR-PAM based on a UV scanner. Using the scanner module, it took 180 seconds to acquire one volumetric data over 1 × 1 mm2. In an in-vitro test, the measured lateral and axial resolution were 1.2 μm and 65.1 μm, respectively. We performed ex-vivo experiments on paraffin sections of tissues after deparaffinization that had been excised from a kidney, liver, colon-cancer and a liver-cancer patient. We could find structures in tumorous tissues distinguishable from normal tissues in 4 × 8 mm2 which is clinically meaningful FOV. We could also identify single nucleus in UV-PAM images, and match it with the corresponding nucleus in microscopic images.
Photoacoustic microscopy (PAM), an emerging biomedical imaging technology, has demonstrated the label-free imaging capability to visualize biomolecules with the aid of superior optical contrast in them. Especially employing ultraviolet (UV) laser at the wavelength of 266 nm, we have developed an UV-PAM. Unlike conventional histology methods such as frozen and formalin-fixed paraffin-embedded (FFPE) sections, UV-PAM can illustrate cell nuclei by utilizing superior light absorption of DNA/RNA without time consuming procedures. In-vitro experiments were conducted to evaluate the spatial resolutions of the developed system. The measured lateral resolution was 1.3 μm, and axial resolution was 62.2 μm. Then we performed ex-vivo experiments using frozen sections of mouse brain to demonstrate the imaging capability of UVPAM as a rapid histology tool. Oxidative stress induced by kainic acid (KA) was monitored using UV-PAM, which is considered as a significant cause for epileptic neuronal brain damage. We have shown the apoptotic feature resulted from the KA-induced hippocampal cell death in a mouse brain section. In contrast to the brain section of the control mouse model, the substantial nuclear marginalization of hippocampal cell death was illustrated in the vulnerable neurons of the CA1 and CA3 regions on the KA-treated mouse with PA imaging. In addition, the PA histologic results were evidenced by the corresponding HE stained images on both the control and the KA-treated mouse, showing similar hippocampal cell death. The PA histologic results could also provide its potential application for use in the monitoring of the morphological changes observed in astrocytes including hypotrophy, hyperplasia, and neoplasia. Further, it might be a beneficial histologic tool for treatment monitoring of neurodegenerative diseases such as acute traumatic brain injury and neuroprotective effects of treatments on the diseases.
A Frozen section examination is the conventional intraoperative histology method widely used in cancer surgery for tumor margin assessment. However, this method is necessary to perform complicated process including sectioning and staining, which require approximately 15 minutes. Particularly with the ultraviolet (UV) laser (266 nm), photoacoustic microscopy (PAM) showed the capability to visualize cell nuclei without the time consuming procedures by utilizing superior optical contrast of DNA/RNA at this wavelength, which can be a potential alternative of the frozen section. However, previously developed UV-PAM is limited to be applied in intraoperative scenarios because it has suffered from slow imaging speed because of 2D mechanical scanning with linear stepper motors. To overcome this limitation, we developed a fast UV-PAM system based on a 2-axis waterproof microelectromechanical systems (MEMS) scanner with the specially fabricated optical components for UV light. This MEMS scanner enables to scan 3 × 3 mm2 range and acquire 400 × 400 pixels image within 20 seconds. The measured spatial and axial resolutions of the developed system are 2.2 and 39 μm, respectively. Finally, we acquired the histology-like PA image of the mouse kidney with characteristic tubular structures of kidney epithelial cells. In the mouse brain, distinct microstructures such as hippocampus and dentate gyrus were differentiated with the validation of frozen section sample.
A thermoreflectance microscopy (TRM) system has emerged as a non-destructive and non-contact tool for a high resolution thermal imaging technique for micro-scale electronic and optoelectronic devices. Quantitative imaging of the temperature distribution is necessary for elaborate thermal characterization under operating conditions, such as thermal profiling and performance and reliability analysis. We introduce here a straightforward TRM system to perform quantitative thermal characterization of microelectronics devices. The quantitative imaging of the surface temperature distribution of a polysilicon micro-resistor is obtained by a lock-in measurement technique and calibration process in the conventional CCD-based widefield microscope. To confirm the quantitative thermal measurement, the measured thermal information is compared to that obtained with an infrared thermography (IRT) system. In addition to quantitative surface temperature distribution, the sub-micron defects on microelectronic devices can be clearly distinguished from the thermoreflectance images, which are hardly perceptible with a conventional widefield microscopy system. The thermal resolution of the proposed TRM system is experimentally determined by measuring standard deviation values of thermoreflectance data with respect to the iteration number. The spatial and thermal resolutions of our system are measured ~670 nm and ~13 mK, respectively. We believe that quantitative thermal imaging in the TRM system can be used for improvement of microelectronic devices and integrated circuit (IC) designs.
Cancer is increasing fast nowadays through all over the world. Early diagnosis of cancer is a desirable subject as it can
significantly improve the patient's chances of survival. In most cases the cancer is diagnosis using MRI, CT, PET. But,
there are several disadvantages associated with high cost, low sensitivity and specificity, and health risks from
radioactive. For that reason, significant efforts are being invested to improve the current imaging system.
Thermography can offer some advantages. Chief among these are the contact free and low cost for detect cancer. But
thermography has some disadvantages associated with low sensitivity for small tumors.
In this research develops non contact, safe, high sensitivity, and low cost infrared imaging technique. Experiments were
performed using lock in thermography with a small amount of magnetic nanoparticle (MNP) and radiofrequency
generator. As a result, highly sensitive infrared thermography can a small amount of MNP be detected by the technique.
KEYWORDS: Optical coherence tomography, Luminescence, Cladding, Imaging systems, Fluorescence spectroscopy, Tissues, Skin, Single mode fibers, Signal detection, In vivo imaging
We report a combined swept source optical coherence tomography (SSOCT) and fluorescence spectroscopy (FS) system
for multimodal measurements of biochemical information and internal structures with fast imaging speed. The FS probe
composed of a double clad fiber (DCF) coupler is adopted into the single mode fiber based SSOCT system. Here, the
DCF coupler acts as a FS system as well as a multifunctional probe for the SSOCT-FS system. The performances of the
single-unit SSOCT-FS system is confirmed by monitoring the fluorescence signal from photosensitizer in cancerous
region of in-vivo rat and by imaging the internal structures of same region with speed of 40 frames/sec.
We present a common-path optical frequency domain imaging (CP-OFDI) system for non-invasive evaluation of various
pearls. By adopting a high speed ready-to-ship scanning light source and a common-path lensed fiber probe, with the
help of a rotation stage, real-time display of whole circumference of a pearl could be achieved. The common-path lensed
fiber probe was fabricated by simply forming a focusing lens directly on the tip of an optical fiber, thus the fiber lens
acted as a reference reflector as well as a focusing lens. The focal length of the lensed fiber probe was over 600 μm in
free space and the average imaging depth reached up to 3 mm, which was deep enough to examine the internal structure
of the pearl. The sensitivity of the system was experimentally obtained as 100dB. With an implemented system, the
presence of nucleus and the nacreous laminated pattern were confirmed and analyzed. Experimental results show that the
CP-OFDI system has great potential for identifying and grading pearls non-invasively but precisely.
We present the method measuring the thickness and the refractive index of a transparent specimen at a same time based on
full-field optical coherence tomography. As a sample a small drop of epoxy was placed on a flat plate and the high-resolution
depth resolved en-face images of the epoxy drop were taken. With adopting the plate surface as a reference plane,
the physical thickness and the refractive index distribution could be obtained. Owing to the full-field imaging capability, we
could obtain the transverse distributions of the thickness and the refractive index without any transverse scanning. The
measured thickness at the center of the sample was 24 μm and the average index was 1.4055 with the standard deviation of
0.0002.
We report an all-fiber system aided by double-clad fiber (DCF) and DCF devices for simultaneous measurements of
optical coherence tomography (OCT) and fluorescence spectroscopy (FS). The DCF together with DCF coupler and
single-body DCF lens helped in realizing a multifunctional single-unit probe for the OCT-FS system. The fiber lens
formed on the DCF aids in effective focusing and signal collection, while the DCF coupler collects the OCT signal from
the core and the fluorescence signal from the cladding of the DCF. The OCT image and fluorescence spectra of plant
tissues are simultaneously measured and presented to validate the performance.
We propose a fiber-based hand-held scanning probe suitable for the sample arm of spectral domain optical coherence
tomography (SD-OCT). To achieve a compact and miniaturized probe, a single-body lensed-fiber, on which an
iron-bead ferromagnetic material is loaded was fabricated and a solenoid actuator driven by readily available driving
voltage (10 V) and current (120 mA) was utilized. A focusing lens was directly formed in a single-body onto the distal
end of a fiber, which eliminated any complement optical components in front of a conventional sample probe and
removes any optical alignment problem. By using the soft-iron solenoid actuator, the fiber in the probe is activated
which gives the sample scanning for the OCT imaging. Moreover, the simple design of the solenoid allowed easy
fabrication and a good practicality. With the implemented probe, OCT images of a pearl and a human finger tip were
obtained at an imaging speed of 30 Hz and a scanning range of 4 mm.
We report on the fabrication and performance of a lensed photonic crystal fiber (PCF) designed as a compact but effective side-viewing optical imaging probe. The lensed-PCF probe was implemented in a single body without using any other fibers or additional optics. The beam expansion region and a focusing ball lens, necessary as a focuser, were simultaneously formed along a small piece of PCF by using arc discharges. The side-viewing ability was endowed by polishing the ball lens with a femto-second laser to form a TIR (total internal reflection) surface. The working distance and the transverse resolution of the fabricated single-body lensed-PCF were experimentally measured to be ~570 μm and 6.8 μm, respectively. With the proposed lensed-PCF probe, OCT images of an in vitro biological sample were successfully obtained
We propose an all-fiber probe for the sample arm of an optical coherence tomography (OCT) system. By forming a
focusing lens directly on the tip of an optical fiber, a compact sample probe could be implemented. To achieve a long
enough working distance and a high enough lateral resolution at the same time, a coreless silica fiber (CSF) having a
diameter larger than that of a conventional single mode fiber was utilized. With the specially fabricated CSF having a
diameter of 180 μm, a fiber-lens having a 120 μm radius of curvature could be made, which allowed the sample probe
having a working distance as long as 920 μm and a lateral resolution as high as 9.4 μm. To present the performance of
the OCT system equipped with the proposed sample probe, the OCT images of a rat finger skin and a pearl were taken.
The system could image as deep as 1.0 mm of the rat finger skin and 3.5 mm of the pearl, and the images are compared
with the ones taken by using a conventional objective lens (10x, NA0.25). Owing to the small form factor of the
proposed probe, it can find good applications in the field of optical imaging based on endoscope or catheter.
We propose the envelope detection method that is based on Hilbert transform for image restoration in full-filed optical
coherence tomography (FF-OCT). The FF-OCT system presenting a high-axial resolution of 0.9 &mgr;m was implemented
with a Kohler illuminator based on Linnik interferometer configuration. A 250 W customized quartz tungsten halogen
lamp was used as a broadband light source and a CCD camera was used as a 2-dimentional detector array. The proposed
image restoration method for FF-OCT requires only single phase-shifting. By using both the original and the phase-shifted
images, we could remove the offset and the background signals from the interference fringe images. The desired
coherent envelope image was obtained by applying Hilbert transform. With the proposed image restoration method, we
demonstrate en-face imaging performance of the implemented FF-OCT system by presenting a tilted mirror surface, an
integrated circuit chip, and a piece of onion epithelium.
We implemented a fiber-based optical coherence tomography (OCT) system by using a photonic crystal fiber (PCF) coupler which could support an ultra-wideband spectral bandwidth. The PCF coupler fabricated by the fused biconical tapered (FBT) method showed rather flat coupling efficiency over a broad spectral bandwidth. Furthermore, the mode-field shapes at the output ports of the PCF coupler showed single mode characteristic over a wideband range. These features will enable the OCT system to operate at 1300 nm as well as at 800 nm without changing the coupler. The FWHM of the interferogram was measured to be about 3 um when a white-light source was used. While a Ti:Sapphire laser and a conventional superluminescent diode (SLD) produced interferograms with FWHMs of about 4 um and 15 um, respectively. The OCT imaging performance of the PCF-based OCT system was demonstrated by imaging an in vitro rat eye and Misgurnus mizolepis skin with a SLD source at 1300 nm and by imaging a tooth with a Ti:Sapphire laser source at 800 nm. The PCF coupler might enable the utilization of an ultra-wideband supercontinuum generated light source in fiber-optic OCT systems for obtaining high resolution, and also realization of a white-light source as a cost effective solution for fiber-based high-resolution OCT systems. Further, this coupler also can operate as single mode not only near 1000 nm but also near 500 nm wavelengths. This feature may support realization of fiber based second harmonic (SH) OCT system.
We employed OCT imaging technique to study the human teeth infected with the caries lesion in fit and fissure. A time domain OCT system using a rapid-scanning optical delay line enabled high speed imaging of extracted teeth. The OCT images presented the morphological feature and caries-involved area of the dental structure with a high resolution of ~14 μm. The OCT images could be utilized to diagnose the disease, while a signal along the axial direction could provide quantitative analysis of the disease based on the reflectivity differences in the specimen. We investigated the influence of caries in human teeth with several imaging tools such as light illuminating exam, digital intra-oral radiography and electron probe micro analyzer, which provided the distributions of chemical compositions, mainly calcium and phosphate in hard tissues. The biochemical changes acquired from EPMA and the morphological features acquired from OCT in the early stage of caries were compared and analyzed to present more objectively practical index for translating the degree of caries.
We have implemented an all-fiber optical delay line, which is composed of fiber optic components such as two linearly chirped fiber Bragg gratings, fiber optic coupler and circulator. The proposed all-fiber delay line possesses features of automatic dispersion compensation and amplified optical delay. Using the fundamental characteristics of chirped fiber Bragg gratings, the basic properties are derived to appreciate the principle of all-fiber delay line. We obtained the experimental results that reveals group delay cancellation and amplified optical delay. The non-invasive cross-sectional images of biological and transparent glass samples are acquired with the proposed all-fiber delay line, which validates the potential as an optical delay line and its feasibility for optical coherence tomography.
Optical coherence tomography (OCT) images transverse resolution mostly depends on the light source spectrum width. Unfortunately, most common sources providing the required power for decent OCT image have narrow spectrum, which generate a resolution loss. It is possible, assuming the OCT system is linear shift-invariant, to consider the consequence of this spectrum narrowness as a convolution. It becomes then possible to enhance this resolution through iterative deconvolution methods (IDM). However those methods have a drawback, as they usually significantly enhance speckle, which is another consequence of the source spectrum narrowness. To compensate this, we rely on preliminary speckle filtering; and especially the adaptative ones, which provide better final results. We first studied consequences of the most popular IDM on OCT images, and then the effect of preliminary adaptive speckle filtering by different methods.
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