Analysis of lithotripsy efficiency and stone retropulsion displacement according to pulse characteristics of Ho: YAG laser with Moses effect

BACKGROUND AND OBJECTIVES

Compared to the conventional Ho: YAG laser, a Ho: YAG laser device has been reported that has a Moses effect to reduce stone retropulsion and increase lithotripsy efficiency. The principle of this equipment is to convert a single laser pulse into two pulses. Most studies on such lasers are limited to lithotripsy efficiency and the prevention of stone retropulsion; studies according to each pulse condition have not been performed. Therefore, the purpose of this study was to quantify the bubble shape, lithotripsy efficiency, and stone retropulsion displacement in a ureteral phantom according to the modulation of the first pulse characteristics of the Moses effect laser under conditions that maintained the total energy and repetition rate.

MATERIAL AND METHODS

In this study, a Ho: YAG laser system (Holinwon Pro, Wontech Inc., Korea) with an emission wavelength of 2.10 μm and a Moses effect was used. To verify the Moses effect based on the changes in the pulse, a water tank was fabricated, and the ureteral phantom was manufactured in a structure that could be easily installed in the water tank. Additionally, a spherical artificial stone in the ureteral phantom was prepared by mixing calcined gypsum (Cacinated Gypsum) and water at a ratio of 3:1. In the ureteral phantom, a high-speed camera (FASTCAM NOVA S12, Photron Inc.) and visible light were used to record pulse-dependent image analysis of bubbles and stone retropulsion.

RESULT

After mounting the artificial stone in the ureteral phantom, the pulse duration and energy of the first pulse of the Moses effect laser were varied; 30 laser shots for 3 s at a repetition rate of 10 Hz were applied to quantify the lithotripsy efficiency and stone retropulsion displacement, and the experimental values were compared. The fragmentation efficiency was confirmed by measuring the mass before and after the laser pulse application, the original position of the stone retropulsion displacement, and the distance moved. The minimum value of stone retropulsion displacement appeared when the pulse duration of the first pulse was 300 μs, the pulse energy was 100 mJ, and the value was approximately 0.28 mm. The highest fragmentation efficiency was observed under the same conditions, and the mass loss of the artificial stone at that time was approximately 3.7 mg.

CONCLUSION

Quantitative indices, such as lithotripsy efficiency and stone retropulsion displacement, were confirmed using ultrahigh-speed cameras to determine the effect of the first pulse energy and duration of the Ho: YAG laser with the Moses effect on stone removal. It was confirmed that the longer the duration of the primary pulse and the lower the energy, the higher the fragmentation efficiency. In this study, the possibility of manufacturing a laser with an optimal stone-removal effect was confirmed according to the first-pulse condition of the laser with the Moses effect.

Non-contact oxygen saturation monitoring for wound healing process using dual-wavelength simultaneous acquisition imaging system

Here we report the fabrication of a noncontact pulse oximeter system based on a dual-wavelength imaging system and its oxygen saturation monitoring performance during wound healing. The dual-wavelength imaging system consists of 660 nm and 940 nm light-emitting diodes and a multi-spectral camera that simultaneously accepts visible and near-infrared images. Using the proposed system, images were acquired at 30 fps at both wavelengths, and photoplethysmography signals were extracted by specifying a specific region in the images. We removed the signals caused by small movements and smoothed them using the discrete wavelet transform and moving average filter. To confirm the feasibility of the proposed noncontact oxygen saturation system, a wound model was created using a hairless mouse and oxygen saturation was measured during wound healing. The measured values were compared and analyzed using a reflective animal pulse oximeter. Through a comparative analysis of these two devices, the error of the proposed system was evaluated and the possibility of its clinical application and wound healing monitoring through oxygen saturation measurement confirmed.

Analysis of penetration depth and healing process of a needleless laser lancet using swept-source optical coherence tomography

BACKGROUND AND OBJECTIVES

Needleless laser lancets have been used to reduce needle pain in people who undertake self-monitoring of blood glucose (SMBG). Although clinical trials have been conducted to understand the degree of pain associated with the developed laser blood sampling device, it is only judged by the patients' subjective judgment. This study aimed to analyze the performance and healing process of a needleless laser lancet. In particular, the penetration depth and healing process of a conventional lancet and a needleless laser lancet were quantitatively analyzed using a swept-source optical coherence tomography (SS-OCT) system.

MATERIALS AND METHODS

To reduce unnecessary animal sacrifice, pig skin was used to establish and set the conditions for needleless laser lancets (wavelength of 2.94 μm; LMT-5000; Lameditech), and the penetration depth and healing process were quantitatively assessed at 0, 6, 9, and 16 h after laser (energy, 150-270 mJ in stages; voltage, 7.4 V_dc ; pulse width, approximately 200 microsecond) irradiation using 7-week-old male BALB/c nude mice. The penetration depth and healing process were measured using homemade SS-OCT, and histopathological examination was performed to observe the healing process.

RESULTS

Four 7-week-old male BALB/c nude mice were tested at intensity levels of 1-3 using a needleless laser lancet and compared with the experimental values using a conventional lancet. After the lancet test, the diameter and depth of the puncture were measured using SS-OCT and the healing process was confirmed using SS-OCT and pathological slides. The puncture diameter of the needleless laser lancet was about 0.5 mm regardless of the level. In addition, the average depths at Levels 1, 2, and 3 of the measured needleless laser lancet were approximately 1.05, 1.18, and 1.52 mm, respectively, and the last common lancet was approximately 0.9 mm. In addition, the healing process of the needleless laser lancet and conventional lancet was confirmed through the SS-OCT system.

CONCLUSION

After using the needleless laser lancet, quantitative indicators such as the diameter of puncture, penetration depth, and healing process were confirmed through two-dimensional and three-dimensional images of the homemade SS-OCT system and microscopic imaging of pathological slides.

Development of Intraoperative Near-Infrared Fluorescence Imaging System Using a Dual-CMOS Single Camera

We developed a single-camera-based near-infrared (NIR) fluorescence imaging device using indocyanine green (ICG) NIR fluorescence contrast agents for image-induced surgery. In general, a fluorescent imaging system that simultaneously provides color and NIR images uses two cameras, which is disadvantageous because it increases the imaging head of the system. Recently, a single-camera-based NIR optical imaging device with quantum efficiency partially extended to the NIR region was developed to overcome this drawback. The system used RGB_NIR filters for camera sensors to provide color and NIR images simultaneously; however, the sensitivity and resolution of the infrared images are reduced by 1/4, and the exposure time and gain cannot be set individually when acquiring color and NIR images. Thus, to overcome these shortcomings, this study developed a compact fluorescent imaging system that uses a single camera with two complementary metal-oxide semiconductor (CMOS) image sensors. Sensitivity and signal-to-background ratio were measured according to the concentrations of ICG solution, exposure time, and camera gain to evaluate the performance of the imaging system. Consequently, the clinical applicability of the system was confirmed through the toxicity analysis of the light source and in vivo testing.

Simple Shading Correction Method for Brightfield Whole Slide Imaging

Whole slide imaging (WSI) refers to the process of creating a high-resolution digital image of a whole slide. Since digital images are typically produced by stitching image sequences acquired from different fields of view, the visual quality of the images can be degraded owing to shading distortion, which produces black plaid patterns on the images. A shading correction method for brightfield WSI is presented, which is simple but robust not only against typical image artifacts caused by specks of dust and bubbles, but also against fixed-pattern noise, or spatial variations in pixel values under uniform illumination. The proposed method comprises primarily of two steps. The first step constructs candidates of a shading distortion model from a stack of input image sequences. The second step selects the optimal model from the candidates. The proposed method was compared experimentally with two previous state-of-the-art methods, regularized energy minimization (CIDRE) and background and shading correction (BaSiC) and showed better correction scores, as smooth operations and constraints were not imposed when estimating the shading distortion. The correction scores, averaged over 40 image collections, were as follows: proposed method, 0.39 ± 0.099; CIDRE method, 0.67 ± 0.047; BaSiC method, 0.55 ± 0.038. Based on the quantitative evaluations, we can confirm that the proposed method can correct not only shading distortion, but also fixed-pattern noise, compared with the two previous state-of-the-art methods.

Indocyanine green-loaded injectable alginate hydrogel as a marker for precision cancer surgery

Background

Accurate identification of tumor sites and boundaries is of paramount importance during minimally invasive surgery. Although laparoscopic resection is being increasingly and widely performed for early gastric and colorectal cancers, the detection of tumors located inside the stomach and intestine is difficult owing to the lack of tactile sensation. Here, we propose the application of an indocyanine green (ICG)-loaded alginate hydrogel system as a fluorescence surgical marker for precise laparoscopic operations.

Methods

A physical complex of ICG and human serum albumin (HSA) was mixed with sodium alginate to form an injectable hydrogel system. Calcium carbonate and D-gluconic acid (GA) were added to the gel to control its strength and gelation time, respectively. The optimal conditions for the preparation of injectable hydrogels were determined by analyzing the fluorescence spectra and sol-gel transition time of the prepared samples at various concentrations and compositions. Next, the aqueous solutions of ICG, ICG-HSA, and ICG-HSA-loaded alginate were subcutaneously injected into nude mice (three mice per group), and near-infrared (NIR) fluorescence images of the mice (λ_ex. =780 nm, λ_em. =845 nm) were obtained at different points in time for 8 days. Then, fluorescence intensities at the injection sites, target-to-background ratio, and areas of ICG fluorescence were analyzed. Finally, the potential utility of ICG-HSA-loaded alginate hydrogel as a surgical marker was evaluated in a porcine model. The ICG-HSA-loaded alginate solution was injected into three sites in the submucosal space of the porcine stomach via a catheter. A fluorescent laparoscopic system was installed on the abdomen of the pig 3 days post-injection, and the fluorescence signal generated from the fluorescence surgical marker located inside the stomach was evaluated using the fluorescence laparoscope system (λ_ex. =785 nm, λ_em. =805 nm).

Results

The optimal concentration of ICG-HSA complex was determined to be 30 µM, and maximum fluorescence intensity of the complex was obtained at a 1:1 mole ratio of HSA to ICG. The subcutaneous injection of ICG or ICG-HSA solution in mice resulted in the rapid spread of the fluorescence signal around the injection site in 3 h, and a weak fluorescence was detected at the injection site 24 h post-injection. In contrast, the fluorescence detection time was effectively prolonged up to 96 h post-injection in the case of ICG-HSA-loaded alginate gel, while diffusion of the injected ICG from the injection site was effectively prevented. In the laparoscopic operation, injection sites of the hydrogel in porcine stomach could be accurately detected in real time even after 3 days.

Conclusions

This alginate hydrogel system may be potentially useful as an effective surgical marker in terms of accuracy and persistence for laparoscopic operation.

Mini-Platform for Off-On Near-Infrared Fluorescence Imaging Using Peptide-Targeting Ligands

Here, we propose a zwitterionic near-infrared (NIR) fluorophore-tryptophan (Trp) conjugate with a cleavable linker as a minimal-sized versatile platform (MP) for the preparation of peptide ligand-based off-on type molecular probes. The zwitterionic NIR fluorophore in MP undergoes fluorescence quenching via a photoinduced electron transfer mechanism when in close proximity to tryptophan, and nonspecific binding with serum proteins is minimized by the zwitterionicity of the fluorophore. The linker can be cleaved inside cancer cells in response to tumor-associated stimuli. As a proof-of-concept experiment, ATTO655 was covalently linked with Trp via a diarginine linker to form an MP. A cyclic peptide consisting of Arg-Gly-Asp-d-Phe-Lys (cRGD) was used as a cancer-targeting ligand and was conjugated to the MP to form cRGD-MP. The NIR fluorescence of cRGD-MP could be selectively turned on inside the target cancer cells, thereby enabling specific fluorescence imaging of integrin α_vβ₃-overexpressing cancer cells in vitro and in vivo.

Responsive alginate-cisplatin nanogels for selective imaging and combined chemo/radio therapy of proliferating macrophages

Background

Atherosclerosis is a major global health concern. Targeting macrophages is hypothesized as an alternative treatment for atherosclerosis.

Methods

We synthesized alginate-based cisplatin-loaded nanogels (TANgel) as a pH-responsive drug-releasing theranostic nanoplatform for macrophage cells. Carboxylic acid groups of alginic acid were modified with iminodiacetic acid (IDA) to enhance chelation of platinum ions. The near infrared (NIR) fluorophore ATTO655 was conjugated to the modified alginic acid. Cisplatin was used as an antiproliferation drug and as a crosslinking agent between alginate molecules to form TANgel. Release behavior of cisplatin from TANgel was analyzed under different pH conditions. Cellular uptake and therapeutic efficacy of TANgel were tested in the macrophage cell line J774A.1 and normal human cell lines such as HDMVECn.

Results

The nanogel had a narrow size distribution of approximately 100 nm. The nanogel showed highly pH-responsive drug release behavior. All incorporated cisplatin was released at pH 5 within 48 h, while less than 15% was released at pH 7.4. The nanogel was preferentially taken up by J774A.1 cells compared to normal human cells, enabling selective NIR fluorescence imaging and chemotherapy of macrophage cells. In addition, the nanogel formulation lowered the therapeutic concentration of the drug with and without low dose radiation therapy (RT) compared to the free drug form.

Conclusions

This nanogel system may have potential utility for selective NIR fluorescence imaging and combined chemo/radio therapy of proliferating macrophage cells in atherosclerotic regions, allowing for reduction of systemic toxicity.

Wide field of view optical coherence tomography for structural and functional diagnoses in dentistry

We report herein the fabrication and performance response of a three-dimensional (3-D) intraoral scan probe based on optical coherence tomography (OCT) that enables 3-D structural and functional diagnoses of the human teeth. The OCT system was configured using a swept-source OCT (SS-OCT) with a center wavelength of 1310 nm. The scan probe was built using an MEMS mirror and an optical collimator. The implemented SS-OCT equipped with the MEMS-based scan probe yielded an axial resolution of 10  μm and a scan range of 8  ×  8  mm2. Two-dimensional (2-D) cross-sectional images of the teeth were acquired by the scan probe based on the OCT. The 3-D volume image was acquired by combining a series of 2-D images, which includes internal and structural information of the human teeth. To utilize the OCT system as an intraoral scanner, partially overlapped 3-D volume images were sequentially acquired and stitched. The 3-D stitching was implemented based on an iterative closest point algorithm. The feasibility of the intraoral scan probe is demonstrated based on its ability to image and characterize the structure and function of the human teeth.

Development of Three-Dimensional Dental Scanning Apparatus Using Structured Illumination

We demonstrated a three-dimensional (3D) dental scanning apparatus based on structured illumination. A liquid lens was used for tuning focus and a piezomotor stage was used for the shift of structured light. A simple algorithm, which detects intensity modulation, was used to perform optical sectioning with structured illumination. We reconstructed a 3D point cloud, which represents the 3D coordinates of the digitized surface of a dental gypsum cast by piling up sectioned images. We performed 3D registration of an individual 3D point cloud, which includes alignment and merging the 3D point clouds to exhibit a 3D model of the dental cast.

Interferometric fiber optic sensors

Fiber optic interferometers to sense various physical parameters including temperature, strain, pressure, and refractive index have been widely investigated. They can be categorized into four types: Fabry-Perot, Mach-Zehnder, Michelson, and Sagnac. In this paper, each type of interferometric sensor is reviewed in terms of operating principles, fabrication methods, and application fields. Some specific examples of recently reported interferometeric sensor technologies are presented in detail to show their large potential in practical applications. Some of the simple to fabricate but exceedingly effective Fabry-Perot interferometers, implemented in both extrinsic and intrinsic structures, are discussed. Also, a wide variety of Mach-Zehnder and Michelson interferometric sensors based on photonic crystal fibers are introduced along with their remarkable sensing performances. Finally, the simultaneous multi-parameter sensing capability of a pair of long period fiber grating (LPG) is presented in two types of structures; one is the Mach-Zehnder interferometer formed in a double cladding fiber and the other is the highly sensitive Sagnac interferometer cascaded with an LPG pair.

Compact and multiplexible hydrogen gas sensor assisted by self-referencing technique

We have experimentally implemented a multiplexible but compact fiber sensor system suitable for multipoint sensing of hydrogen gas leakage. By making dual cavities along an optical fiber and coating a palladium film only at the end of the fiber tip, the measurement errors induced by the optical source power fluctuation and the mechanical perturbation in the lead fiber could be compensated. By adjusting the length of the dual-cavity, the capability of multiplexing several hydrogen sensors could be achieved. The experiment results showed that the response speed of the sensor was increasing with temperature, but at a low temperature the response amplitude became large.

Wavelength-division-multiplexing fiber coupler based on bending-insensitive holey optical fiber

A wavelength-division-multiplexing (WDM) coupler has been made with a bending-insensitive holey optical fiber (HOF) by using the fused biconical tapered (FBT) method. The transmission band of the proposed HOF WDM coupler could be easily tuned by adjusting the pulling length during the FBT process. Interestingly, it was observed that the air-hole structure of the HOF should be maintained to have the property of a WDM coupler. As the air holes collapse, the HOF WDM exhibits high-pass-filter-like properties. The cross-sectional scanning electron microscope images of the implemented HOF WDM coupler are presented along with the light intensity distribution measured at the coupling region of the coupler. The proposed HOF couplers may also find applications in optical coarse WDM systems and optical fiber sensors.

2x2 photonic crystal fiber splitter based on silica-based planar lightwave circuits

A 2x2 photonic crystal fiber (PCF) planar lightwave circuit (PLC) splitter, which splits optical power between two PCF channels, has been made by PCF-to-PLC connections. PCF array blocks were lithographically fabricated to have fiber V grooves and used to firmly hold PCFs and align them to the PLC splitter. The proposed splitter showed a rather flat splitting ratio over a wide wavelength range from 1250 nmto1750 nm. With the implemented splitter, we obtained a low excess loss of 1.6 dB, a low polarization-dependent loss of 0.1 dB, and a high return loss of 52 dB. The ultrabroadband operation of the proposed splitter is expected to find applications in optical performance monitoring, Ethernet passive optical networks, and biomedical optics including optical coherence tomography.

Photonic crystal fiber coupler

Fiber couplers made with photonic crystal fibers (PCF) are reported. Two types of PCF were fabricated by means of stacking a group of silica tubes around a silica rod and drawing them. The fiber couplers were made by use of the fused biconical tapered method. With a fiber that had five hexagonally stacked layers of air holes, a 33/67 coupling ratio was obtained, and with a one-layer four-hole fiber, a 48/52 coupling ratio was obtained. The fabrication processes and the characteristics of the PCFs and the PCF couplers are presented.