Speckle noise is one of the dominant factors that degrade image quality in optical coherence tomography (OCT). Here, we propose a new strategy, interleaved OCT (iOCT), for spatial compounding and angular compounding. We demonstrate the efficiency of compounding with iOCT to restrain speckle noise without compromising imaging speed in phantoms and tissue samples.

We demonstrate the first in-fiber light-induced bioactive biotin-functionalization via photobleaching fluorophore-conjugated biotin. Photobleaching the fluorophores generated free radicals that bind to the albumin-passivated inner surface of pure silica photonic crystal fiber. The subsequent attachment of dye-conjugated streptavidin to the bound biotin qualified the photo-immobilization process and demonstrated a potential for the construction of in-fiber macromolecular assemblies or multiplexes. Compared with other in-fiber bioactive coating methods, the proposed light-induced technique requires only a low-power light source, without the need for additional preactivation steps or toxic chemical reagents. This method, hence, enables a simple and compact implementation for potential biomedical applications.

Supercontinuum (SC) source is a new kind of artificial light source, having the characteristics of both laser and traditional incoherent light source, i.e., high brightness, good direction, and super broadband spectrum. The rapid development of SC source stimulates our concern on its ocular damage potency. However, the damage effects of SC source have never been explored. The retinal damage threshold of chinchilla grey rabbit induced by a Vis-infrared SC source was determined for the first time. Additionally, a theoretical method was also developed for analyzing the hazard risks of SC source.

Recently, the number of blast injuries of the inner ear has increased in the general population. In blast-induced inner ear injury, a shock wave (SW) component in the blast wave is considered to play an important role in sensorineural hearing loss. However, the mechanisms by which an SW affects inner ear tissue remain largely unknown. We aimed to establish a new animal model for SW-induced inner ear injury by using laser-induced SWs (LISWs) on rats. The LISWs were generated by irradiating an elastic laser target with 694-nm nanosecond pulses of a ruby laser. After LISW application to the cochlea through bone conduction, auditory measurements revealed the presence of inner ear dysfunction, the extent of which depended on LISW overpressure. A significantly lower survival rate of hair cells and spiral ganglion neurons, as well as severe oxidative damage, were observed in the inner ear exposed to an LISW. Although considerable differences in the pressure characteristics exist between LISWs and SWs in real blast waves, the functional and morphological changes shown by the present LISW-based model were similar to those observed in real blast-induced injury. Thus, our animal model is expected to be useful for laboratory-based research of blast-induced inner ear injury.

The correlation between histologic grade, an increasingly important measure of prognosis for patients with breast cancer, and tryptophan levels from tissues of 15 breast carcinoma patients was investigated. Changes in the relative content of key native organic biomolecule tryptophan were seen from the fluorescence spectra of cancerous and paired normal tissues with excitation wavelengths of 280 and 300 nm. Due to a large spectral overlap and matching excitation–emission spectra, fluorescence resonance energy transfer from tryptophan-donor to reduced nicotinamide adenine dinucleotides-acceptor was noted. We used the ratios of fluorescence intensities at their spectral emission peaks, or spectral fingerprint peaks, at 340, 440, and 460 nm. Higher ratios correlated strongly with high histologic grade, while lower-grade tumors had low ratios. Large tumor size also correlated with high ratios, while the number of lymph node metastases, a major factor in staging, was not correlated with tryptophan levels. High histologic grade correlates strongly with increased content of tryptophan in breast cancer tissues and suggests that measurement of tryptophan content may be useful as a part of the evaluation of these patients.

Magnetomotive optical coherence tomography (MM-OCT) can be utilized to spatially localize the presence of magnetic particles within tissues or organs. These magnetic particle-containing regions are detected by using the capability of OCT to measure small-scale displacements induced by the activation of an external electromagnet coil typically driven by a harmonic excitation signal. The constraints imposed by the scanning schemes employed and tissue viscoelastic properties limit the speed at which conventional MM-OCT data can be acquired. Realizing that electromagnet coils can be designed to exert MM force on relatively large tissue volumes (comparable or larger than typical OCT imaging fields of view), we show that an order-of-magnitude improvement in three-dimensional (3-D) MM-OCT imaging speed can be achieved by rapid acquisition of a volumetric scan during the activation of the coil. Furthermore, we show volumetric (3-D) MM-OCT imaging over a large imaging depth range by combining this volumetric scan scheme with full-range OCT. Results with tissue equivalent phantoms and a biological tissue are shown to demonstrate this technique.

Colitis-associated cancer (CAC) arises from premalignant flat lesions of the colon, which are difficult to detect with current endoscopic screening approaches. We have developed a complementary fluorescence and polarization reporting strategy that combines the unique biochemical and physical properties of dysplasia and cancer for real-time detection of these lesions. Using azoxymethane-dextran sodium sulfate (AOM-DSS) treated mice, which recapitulates human CAC and dysplasia, we show that an octapeptide labeled with a near-infrared (NIR) fluorescent dye selectively identified all precancerous and cancerous lesions. A new thermoresponsive sol-gel formulation allowed topical application of the molecular probe during endoscopy. This method yielded high contrast-to-noise ratios (CNR) between adenomatous tumors (20.6±1.65) and flat lesions (12.1±1.03) and surrounding uninvolved colon tissue versus CNR of inflamed tissues (1.62±0.41). Incorporation of nanowire-filtered polarization imaging into NIR fluorescence endoscopy shows a high depolarization contrast in both adenomatous tumors and flat lesions in CAC, reflecting compromised structural integrity of these tissues. Together, the real-time polarization imaging provides real-time validation of suspicious colon tissue highlighted by molecular fluorescence endoscopy.

Laser diodes are widely used in diffuse optical tomography (DOT) systems but are typically expensive and fragile, while light-emitting diodes (LEDs) are cheaper and are also available in the near-infrared (NIR) range with adequate output power for imaging deeply seated targets. In this study, we introduce a new low-cost DOT system using LEDs of four wavelengths in the NIR spectrum as light sources. The LEDs were modulated at 20 kHz to avoid ambient light. The LEDs were distributed on a hand-held probe and a printed circuit board was mounted at the back of the probe to separately provide switching and driving current to each LED. Ten optical fibers were used to couple the reflected light to 10 parallel photomultiplier tube detectors. A commercial ultrasound system provided simultaneous images of target location and size to guide the image reconstruction. A frequency-domain (FD) laser-diode-based system with ultrasound guidance was also used to compare the results obtained from those of the LED-based system. Results of absorbers embedded in intralipid and inhomogeneous tissue phantoms have demonstrated that the LED-based system provides a comparable quantification accuracy of targets to the FD system and has the potential to image deep targets such as breast lesions.

The analysis of urinary stones is mandatory for the best management of the disease after the stone passage in order to prevent further stone episodes. Thus the use of an appropriate methodology for an individualized stone analysis becomes a key factor for giving the patient the most suitable treatment. A recently developed hyperspectral imaging methodology, based on pixel-to-pixel analysis of near-infrared spectral images, is compared to the reference technique in stone analysis, infrared (IR) spectroscopy. The developed classification model yields >90% correct classification rate when compared to IR and is able to precisely locate stone components within the structure of the stone with a 15  μm resolution. Due to the little sample pretreatment, low analysis time, good performance of the model, and the automation of the measurements, they become analyst independent; this methodology can be considered to become a routine analysis for clinical laboratories.

Oral cancer is one of the most common cancers worldwide. One-fifth of the world’s oral cancer subjects are from India and other South Asian countries. The present Raman mapping study was carried out to understand biochemical variations in normal and malignant oral buccal mucosa. Data were acquired using WITec alpha 300R instrument from 10 normal and 10 tumors unstained tissue sections. Raman maps of normal sections could resolve the layers of epithelium, i.e. basal, intermediate, and superficial. Inflammatory, tumor, and stromal regions are distinctly depicted on Raman maps of tumor sections. Mean and difference spectra of basal and inflammatory cells suggest abundance of DNA and carotenoids features. Strong cytochrome bands are observed in intermediate layers of normal and stromal regions of tumor. Epithelium and stromal regions of normal cells are classified by principal component analysis. Classification among cellular components of normal and tumor sections is also observed. Thus, the findings of the study further support the applicability of Raman mapping for providing molecular level insights in normal and malignant conditions.

The critical optical properties of a Gaussian laser beam in two-photon or multiphoton fluorescence imaging, including the beam spot size, depth of focus, and intensity profile, are investigated for spatially locating nanoscale solutes in and surrounding the microvessels of rat brain.

Dual-band optical coherence tomography (OCT) can greatly enhance the imaging contrast with potential applications in functional (spectroscopic) analysis. A new simultaneous dual-band Fourier domain mode-locked swept laser configuration for dual-band OCT is reported. It was based on a custom-designed dual-channel driver to synchronize two different wavelength bands at 1310 and 1550 nm, respectively. Two lasing wavelengths were swept simultaneously from 1260 to 1364.8 nm for the 1310-nm band and from 1500 to 1604 nm for the 1550-nm band at an A-scan rate of 45 kHz. Broadband wavelength-division multiplexing was utilized to couple two wavelength bands into a common catheter for circumferential scanning to form dual-band OCT. The proposed dual-band OCT scheme was applied to endoscopic OCT imaging of mouse esophageal wall ex vivo and human fingertip in vivo to justify the feasibility of the proposed imaging technique. The proposed dual-band OCT system is fast and easy to be implemented, which allows for in vivo high-speed biomedical imaging with potential applications in spectroscopic investigations for endoscopic imaging.

Microscopic images of a living cell are the main source of information on its functional state. Modern interference microscopy techniques allow the numerical parameters of cell images to be obtained with an accuracy not available with other methods. Quantitative analysis of phase images of T lymphocytes (TCs) in different functional states demonstrated that variations of the properties of intracellular water should be taken into account. This conclusion agrees with the current view that the physical parameters of water, including the refractive index (RI) of a water layer, depend on the hydrophilicity and other characteristics of the adjacent surface. Application of this concept to phase images of TCs showed that the contribution of the fourth phase of water (4-water) or the structured water component, which has an increased RI, should be considered. The proportion of 4-water depends on the functional state of the cell determined by the culture medium composition. Normally, the proportion of 4-water in organelles is as high as 30%; it is considerably lower in organelles of cells with inhibited metabolism.

We propose a theoretical framework for consecutively reconstructing absorption and scattering distributions in turbid soft tissue in an iterative manner. This approach takes advantage of the stability of a recently reported least-squares fixed-point iterative method for reconstructing an optical absorption coefficient map to iteratively update estimates of absorption and scattering for each iteration. Simulations demonstrate that this method converges to an accurate estimate of the optical properties within only a small number of iterations and is robust to noise at realistic signal-to-noise levels.

We present a noninvasive phase-variance (pv)–based motion contrast method for depth-resolved imaging of the human chorioretinal complex microcirculation with a newly developed phase-stabilized high speed (100-kHz A-scans/s) 1-μm swept-source optical coherence tomography (SSOCT) system. Compared to our previous spectral-domain (spectrometer based) pv-spectral domain OCT (SDOCT) system, this system has the advantages of higher sensitivity, reduced fringe wash-out for high blood flow speeds and deeper penetration in choroid. High phase stability SSOCT imaging was achieved by using a computationally efficient phase stabilization approach. This process does not require additional calibration hardware and complex numerical procedures. Our phase stabilization method is simple and can be employed in a variety of SSOCT systems. Examples of vasculature in the chorioretinal complex imaged by pv-SSOCT from normal as well as diseased eyes are presented and compared to retinal images of the same subjects acquired with fluorescein angiography and indocyanine green angiography. Observations of morphology of vascular perfusion in chorioretinal complex visualized by our method are listed.

We conducted a canine study to investigate the in vivo feasibility of photoacoustic imaging for intraoperative updates to brachytherapy treatment plans. A fiber coupled to a 1064-nm Nd:YAG laser was inserted into high-dose-rate brachytherapy needles, which diffused light spherically. These needles were inserted through the perineum into the prostate for interstitial light delivery and the resulting acoustic waves were detected with a transrectal ultrasound probe. Postoperative computed tomography images and ex vivo photoacoustic images confirmed seed locations. Limitations with insufficient light delivery were mitigated with short-lag spatial coherence (SLSC) beamforming, providing a 10–20 dB contrast improvement over delay-and-sum (DAS) beamforming for pulse energies ranging from 6.8 to 10.5 mJ with a fiber-seed distance as large as 9.5 mm. For the same distance and the same range of energy densities, signal-to-noise ratios (SNRs) were similar while the contrast-to-noise ratio (CNR) was higher in SLSC compared to DAS images. Challenges included visualization of signals associated with the interstitial fiber tip and acoustic reverberations between seeds separated by ≤2 mm. Results provide insights into the potential for clinical translation to humans.

Planar sensor arrays have advantages when used for photoacoustic imaging: they do not require the imaging target to be enclosed, and they are easier to manufacture than curved arrays. However, planar arrays have a limited view of the acoustic field due to their finite size; therefore, not all of the acoustic waves emitted from a photoacoustic source can be recorded. This loss of data results in artifacts in the reconstructed photoacoustic image. A detection array configuration which combines a planar Fabry–Pérot sensor with perpendicular acoustic reflectors is described and experimentally implemented. This retains the detection advantages of the planar sensor while increasing the effective detection aperture in order to improve the reconstructed photoacoustic image.

Fluorescence molecular tomography (FMT) is a promising imaging technique in preclinical research, enabling three-dimensional location of the specific tumor position for small animal imaging. However, FMT presents a challenging inverse problem that is quite ill-posed and ill-conditioned. Thus, the reconstruction of FMT faces various challenges in its robustness and efficiency. We present an FMT reconstruction method based on nonmonotone spectral projected gradient pursuit (NSPGP) with l₁-norm optimization. At each iteration, a spectral gradient-projection method approximately minimizes a least-squares problem with an explicit one-norm constraint. A nonmonotone line search strategy is utilized to get the appropriate updating direction, which guarantees global convergence. Additionally, the Barzilai–Borwein step length is applied to build the optimal step length, further improving the convergence speed of the proposed method. Several numerical simulation studies, including multisource cases as well as comparative analyses, have been performed to evaluate the performance of the proposed method. The results indicate that the proposed NSPGP method is able to ensure the accuracy, robustness, and efficiency of FMT reconstruction. Furthermore, an in vivo experiment based on a heterogeneous mouse model was conducted, and the results demonstrated that the proposed method held the potential for practical applications of FMT.

We demonstrate the invivo assessment of human scars by parametric imaging of birefringence using polarization-sensitive optical coherence tomography (PS-OCT). Such in vivo assessment is subject to artifacts in the detected birefringence caused by scattering from blood vessels. To reduce these artifacts, we preprocessed the PS-OCT data using a vascular masking technique. The birefringence of the remaining tissue regions was then automatically quantified. Results from the scars and contralateral or adjacent normal skin of 13 patients show a correspondence of birefringence with scar type: the ratio of birefringence of hypertrophic scars to corresponding normal skin is 2.2±0.2 (mean±standard deviation), while the ratio of birefringence of normotrophic scars to normal skin is 1.1±0.4. This method represents a new clinically applicable means for objective, quantitative human scar assessment.

A methodology that employs confocal Raman microscopy (CRM) on ex vivo skin samples is proposed for the investigation of drug content and distribution in the skin. To this end, the influence of the penetration enhancers propylene glycol and polyoxyethylene-23-lauryl ether on the penetration and permeation of procaine as a model substance was investigated. The drug content of skin samples that had been incubated with semisolid formulations containing one of these enhancers was examined after skin segmentation. The experiments showed that propylene glycol did not affect the procaine content that was delivered to the skin, whereas polyoxyethylene-23-lauryl ether led to higher procaine contents and deeper penetration. Neither substance was found to influence the permeation rate of procaine. It is thereby shown that CRM can provide additional information on drug penetration and permeation. Furthermore, the method was found to enhance the depth from which Raman spectra can be collected and to improve the depth resolution compared to previously proposed methods.

During embryogenesis, presumptive brain compartments are patterned by dynamic networks of gene expression. The spatiotemporal dynamics of these networks, however, have not been characterized with sufficient resolution for us to understand the regulatory logic resulting in morphogenetic cellular behaviors that give the brain its shape. We have developed a new, integrated approach using ultrashort pulse microscopy [a high-resolution, two-photon fluorescence (2PF)-optical coherence microscopy (OCM) platform using 10-fs pulses] and image registration to study brain patterning and morphogenesis in zebrafish embryos. As a demonstration, we used time-lapse 2PF to capture midbrain-hindbrain boundary morphogenesis and a wnt1 lineage map from embryos during brain segmentation. We then performed in situ hybridization to deposit NBT/BCIP, where wnt1 remained actively expressed, and reimaged the embryos with combined 2PF-OCM. When we merged these datasets using morphological landmark registration, we found that the mechanism of boundary formation differs along the dorsoventral axis. Dorsally, boundary sharpening is dominated by changes in gene expression, while ventrally, sharpening may be accomplished by lineage sorting. We conclude that the integrated visualization of lineage reporter and gene expression domains simultaneously with brain morphology will be useful for understanding how changes in gene expression give rise to proper brain compartmentalization and structure.

We sought to elucidate the mechanisms underlying two common intravascular optical coherence tomography (IV-OCT) artifacts that occur when imaging metallic stents: “merry-go-rounding” (MGR), which is an increase in strut arc length (SAL), and “blooming,” which is an increase in the strut reflection thickness (blooming thickness). Due to uncontrollable variables that occur in vivo, we performed an in vitro assessment of MGR and blooming in stented vessel phantoms. Using Xience V and Driver stents, we examined the effects of catheter offset, intimal strut coverage, and residual blood on SAL and blooming thickness in IV-OCT images. Catheter offset and strut coverage both caused minor MGR, while the greatest MGR effect resulted from light scattering by residual blood in the vessel lumen, with 1% hematocrit (Hct) causing a more than fourfold increase in SAL compared with saline (p<0.001). Residual blood also resulted in blooming, with blooming thickness more than doubling when imaged in 0.5% Hct compared with saline (p<0.001). We demonstrate that a previously undescribed mechanism, light scattering by residual blood in the imaging field, is the predominant cause of MGR. Light scattering also results in blooming, and a newly described artifact, three-dimensional-MGR, which results in “ghost struts” in B-scans.

Key tissue parameters, e.g., total hemoglobin concentration and tissue oxygenation, are important biomarkers in clinical diagnosis for various diseases. Although point measurement techniques based on diffuse reflectance spectroscopy can accurately recover these tissue parameters, they are not suitable for the examination of a large tissue region due to slow data acquisition. The previous imaging studies have shown that hemoglobin concentration and oxygenation can be estimated from color measurements with the assumption of known scattering properties, which is impractical in clinical applications. To overcome this limitation and speed-up image processing, we propose a method of sequential weighted Wiener estimation (WE) to quickly extract key tissue parameters, including total hemoglobin concentration (C_tHb), hemoglobin oxygenation (StO₂), scatterer density (α), and scattering power (β), from wide-band color measurements. This method takes advantage of the fact that each parameter is sensitive to the color measurements in a different way and attempts to maximize the contribution of those color measurements likely to generate correct results in WE. The method was evaluated on skin phantoms with varying C_tHb, StO₂, and scattering properties. The results demonstrate excellent agreement between the estimated tissue parameters and the corresponding reference values. Compared with traditional WE, the sequential weighted WE shows significant improvement in the estimation accuracy. This method could be used to monitor tissue parameters in an imaging setup in real time.

The purpose of this research was to waterproof a near-infrared spectroscopy device (PortaMon, Artinis Medical Systems) to enable NIR measurement during swim exercise. Candidate materials were initially tested for waterproof suitability by comparing light intensity values during phantom-based tissue assessment. Secondary assessment involved repeated isokinetic exercises ensuring reliability of the results obtained from the modified device. Tertiary assessment required analysis of the effect of water immersion and temperature upon device function. Initial testing revealed that merely covering the PortaMon light sources with waterproof materials considerably affected the NIR light intensities. Modifying a commercially available silicone covering through the addition of a polyvinyl chloride material (impermeable to NIR light transmission) produces an acceptable compromise. Bland–Altman analysis indicated that exercise-induced changes in tissue saturation index (TSI %) were within acceptable limits during laboratory exercise. Although water immersion had a small but significant effect upon NIR light intensity, this resulted in a negligible change in the measured TSI (%). We then tested the waterproof device in vivo illustrating oxygenation changes during a 100 m freestyle swim case study. Finally, a full study compared club level swimmers and triathletes. Significant changes in oxygenation profiles when comparing upper and lower extremities for the two groups were revealed, reflecting differences in swim biomechanics.

Intrinsic fluorescence spectra of the human normal, cervical intraepithelial neoplasia 1 (CIN1), CIN2, and cervical cancer tissue have been extracted by effectively combining the measured polarized fluorescence and polarized elastic scattering spectra. The efficacy of principal component analysis (PCA) to disentangle the collective behavior from smaller correlated clusters in a dimensionally reduced space in conjunction with the intrinsic fluorescence is examined. This combination unambiguously reveals the biochemical changes occurring with the progression of the disease. The differing activities of the dominant fluorophores, collagen, nicotinamide adenine dinucleotide, flavins, and porphyrin of different grades of precancers are clearly identified through a careful examination of the sectorial behavior of the dominant eigenvectors of PCA. To further classify the different grades, the Mahalanobis distance has been calculated using the scores of selected principal components.

The statistical model of scattered by flowing Brownian particles coherent radiation is suggested. The model includes the random Doppler shifts caused by particle Brownian motion and the speckle fluctuations caused primarily by the flow motion of particles. Analytical expressions are obtained for the correlation function, power spectrum, and spectral width of scattered radiation in the imaging geometry typically used in optical coherence tomography (OCT). It is shown that the spectral density has the Voigt shape, a well-known spectral profile from atomic and molecular spectroscopy. The approach enables the choice of the experimental regimes for the measurement of Brownian particle motion parameters even in the presence of flow. These regimes are characterized by the dominant contribution of Brownian motion in the spectral width of the flow-caused Doppler shift component. Further, the new formalism suggests that prior attempts to extract transverse flow velocity are only valid at near-perpendicular geometry. The impact of the small scattering volume contributing to the OCT signal is also discussed.

We describe a method for dual-view biomechanical strain measurements of highly asymmetrical biological objects, like teeth or bones. By using a spherical mirror, we were able to simultaneously record a digital hologram of the object itself and the mirror image of its (otherwise invisible) rear side. A single laser beam was sufficient to illuminate both sides of the object, and to provide a reference beam. As a result, the system was mechanically very stable, enabling long exposure times (up to 2 min) without the need for vibration isolation. The setup is simple to construct and adjust, and can be used to interferometrically observe any object that is smaller than the mirror diameter. Parallel data processing on a CUDA-enabled (compute unified device architecture) graphics card was used to reconstruct digital holograms and to further correct image distortion. We used the setup to measure the deformation of a tooth due to mastication forces. The finite-element method was used to compare experimental results and theoretical predictions.

This study presents a method for measuring scattering in explanted intraocular lenses (IOLs). Currently, determining scattering in IOLs is usually performed by Scheimpflug cameras and the results are expressed in the units used by this apparatus. The method we propose uses a spectrophotometer and this makes it possible to measure the total transmission of the IOL by using an integrating sphere; the direct transmission is determined by the double-beam mode. The difference between these two transmissions gives a value of the scattering in percentage values of light lost. In addition, by obtaining the spectral transmission curve, information about the most scattered wavelengths is also obtained. The IOL power introduces errors when directly measured, particularly with high powers. This problem can be overcome if a tailor-made cuvette is used that shortens the distance between the IOL and the condensing lens of the spectrophotometer when the IOL powers are below 24 diopters. We checked the effectiveness of this method by measuring the scattering of three explanted IOLs from cornea donors. This method, however, does not make it possible to ascertain whether the scattering measured is caused by surface light scattering or internal light scattering.

The pathogenic process of Alzheimer’s disease (AD) begins years before clinical diagnosis. Here, we suggest a method that may detect AD several years earlier than current exams. The method is based on previous reports that relate the concentration ratio of biomarkers (amyloid-beta and tau) in the cerebrospinal fluid (CSF) to the development of AD. Our method replaces the lumbar puncture process required for CSF drawing by using fluorescence measurements. The system uses an optical fiber coupled to a laser source and a detector. The laser radiation excites two fluorescent probes which may bond to the CSF biomarkers. Their concentration ratio is extracted from the fluorescence intensities and can be used for future AD detection. First, we present a theoretical model for fluorescence concentration ratio estimation. The method’s feasibility was validated using Monte Carlo simulations. Its accuracy was then tested using multilayered tissue phantoms simulating the epidural fat, CSF, and bone. These phantoms have various optical properties, thicknesses, and fluorescence concentrations in order to simulate human anatomy variations and different fiber locations. The method was further tested using ex vivo chicken tissue. The average errors of the estimated concentration ratios were low both in vitro (4.4%) and ex vivo (10.9%), demonstrating high accuracy.

Using a validated in vitro ureter model for laser lithotripsy, the performance of an experimental thulium fiber laser (TFL) was studied and compared to the clinical gold standard holmium:YAG laser. The holmium laser (λ=2120  nm) was operated with standard parameters of 600 mJ, 350  μs, 6 Hz, and 270-μm-core optical fiber. The TFL (λ=1908  nm) was operated with 35 mJ, 500  μs, 150 to 500 Hz, and a 100-μm-core fiber. Urinary stones (60% calcium oxalate monohydrate/40% calcium phosphate) of uniform mass and diameter (4 to 5 mm) were laser ablated with fibers through a flexible video-ureteroscope under saline irrigation with flow rates of 22.7 and 13.7  ml/min for the TFL and holmium laser, respectively. The temperature 3 mm from the tube’s center and 1 mm above the mesh sieve was measured by a thermocouple and recorded throughout each experiment for both lasers. Total laser and operation times were recorded once all stone fragments passed through a 1.5-mm sieve. The holmium laser time measured 167±41  s (n=12). TFL times measured 111±49, 39±11, and 23±4  s, for pulse rates of 150, 300, and 500 Hz, respectively (n=12 each). Mean peak saline irrigation temperatures reached 24±1°C for holmium, and 33±3°C, 33±7°C, and 39±6°C, for TFL at pulse rates of 150, 300, and 500 Hz, respectively. To avoid thermal buildup and provide a sufficient safety margin, TFL lithotripsy should be performed with pulse rates below 500 Hz and/or increased saline irrigation rates. The TFL rapidly fragmented kidney stones due in part to its high pulse rate, high power density, high average power, and observation of reduced stone retropulsion and may provide a clinical alternative to the conventional holmium laser for lithotripsy.

The purpose of this study was to analyze thermal effects during laser-assisted periodontal treatment. An in vitro model for temperature measurements was developed to investigate different laser settings regarding pulp safety. Additionally, the influence of transmission on pulp temperature elevation was evaluated. Longitudinal root sections were irradiated with a 940-nm diode laser with 1.0 and 1.5 W in continuous wave mode. According to wall thicknesses, irradiation times were adjusted to 20 s for upper and 10 s for lower incisors, respectively. Transmission was relatively low in both upper (4.8% to 8.3% of incident power) and lower incisors (10.2% to 15.0%). Samples were embedded in a polyurethane model and six thermocouples were affixed. Regardless of dentine thickness, the middle third of the root was identified to be the area with the most heat load, where a temperature rise of 7.5°C (1.0 W) and 10.5°C (1.5 W) was registered in upper incisors. A difference of 1.5°C to 3°C was detected in lower incisors compared with uppers. All settings were safe except for 1.5 W, 20 s. Transmission affected heat generation remarkably. The proposed model provides advantages regarding heat transfer and enables for spatially resolved temperature measurements.

This PDF file contains the editorial “Terahertz Biomedical Science and Technology” for JBO Vol. 19 Issue 12