Free electron laser ablation of urinary calculi: an experimentalstudy

Infrared laser ablation of urinary calculi was investigated as a function of wavelength to determine the relation of ablation threshold fluences, ablation depths, and optical absorption. A simple photothermal ablation model was employed to examine this relationship. Human urinary calculi composed of >95% uric acid, >95% cystine, >95% calcium oxalate monohydrate (COM), and >90% magnesium ammonium phosphate hexahydrate (MAPH) were used. Various wavelengths between 2.1 and 6.5 μm were selected to perform threshold fluence and ablation depth measurements. The laser source for this study was the tunable pulsed infrared free electron laser (FEL) at Vanderbilt University. Experimental results indicated a correlation of threshold fluence and ablation depth to the optical absorption properties of the calculi. When calculus optical absorption increased, the threshold fluences decreased. Although the ablation depths increased with calculus optical absorption, results indicated that in certain calculi the ablation depth was affected by optical attenuation through the ablation plume. These observations were in agreement with the photothermal ablation model, but fractures in striated calculi at higher optical absorptions indicated the contribution of a photomechanical mechanism     

Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry Using a Mid-Infrared Tunable Laser for Direct Protein Analysis

Matrix-assisted laser desorption/ionization (MALDI) using a mid-infrared (MIR) laser is a promising technique for the study of biomolecules. We achieved the measurement of an insoluble protein under strong denaturing conditions using two lasers, a UV laser and a free electron laser (FEL). The FEL is a powerful tool for the IR-MALDI; however, it is expensive and difficult to operate. We developed a MIR-MALDI time-of-flight mass spectrometer combined with a tunable MIR nanosecond pulsed laser, which was developed by the Institute of Physical and Chemical Research (RIKEN; Wako, Japan) and Kawasaki Heavy Industries, Ltd. (Tokyo, Japan). We evaluated the advantages of MIR-MALDI using this MIR nanosecond pulsed laser with a urea matrix and compared the results with that from previous study using the FEL. The molecular mass of insulin with urea was obtained at wavelength between 5.8 and 6.2 mum, which corresponds to the >C=O stretching vibration mode. In particular, a high SNR was observed at a wavelength of 5.9 mum. This technique produced a better SNR than that of a previous study that used the FEL.     

Erbium 3 μm fiber lasers

With its recent breakthrough in terms of output power the erbium 3-μm fiber laser has become an object of intense scientific research and an increasingly attractive tool for medical applications. The paper reviews the research on the erbium 3-μm fiber laser since its first demonstration. Its development is seen in relationship to the early success of the corresponding crystal laser system, to the foundations that were laid by the investigation of its spectroscopy and population mechanisms, and the recent technological developments in related fields     

Robotic surgeons

A small number of medical robots have already been applied in actual orthopedic surgery. More broadly, other surgical robots have found clinical application in the fields of neurosurgery and prostate surgery. In addition to these robots, which have reached the stage of clinical trial, many more prototype systems have been developed in research laboratories. Potential orthopedic applications include total hip replacement, total knee replacement, spine placements, ligament reconstruction, hand and other microsurgery, and total shoulder replacement. These prototypes have reported improved accuracy and consistency of surgical intervention.     

LED光源在医学中的应用

发光二极管(LED)作为一种新型的医用光源,由于其独有的特点,引起了各方的广泛关注和深入研究。该文分别对医用照明、医学诊断、医学治疗领域进行了分析,并对LED光源应用于医学治疗进行了重点研究,从多方面简单比较了LED光疗法与传统激光光源疗法,突出了LED光疗的优势。LED光源疗法将在医学领域有广阔的应用,在产品商业化上也会有较大的发展。     

Current status of flexible waveguides for IR laser radiationtransmission

Minimal invasive surgery (MIS) is the preferred method for performing medical operations today due to its lower cost, fast healing, and minimal post-operative pain and discomfort to the treated patients. It is rapidly expanding with the development and miniaturization of two-dimensional (2-D) and three-dimensional (3-D) endoscopic imaging systems. Laser surgery has also proved itself to be a preferred tool of operation over standard tools in a lot of the cases. Development of a reliable flexible fiber or waveguide will enable surgeons to bring the laser beam transcendoscopically within body cavities. It will combine the endoscopy technique with the advantageous laser interaction with tissue to create a powerful surgical tool which will be the ultimate choice of operating procedure. A number of research groups have suggested flexible waveguides for the mid-IR region between 2.5 and 11 μm, which contains very important and useful laser wavelengths and is not covered by silica fibers. The chief goals for the development of such delivery devices are summarized. The different solutions suggested are broadly described and thoroughly analyzed for their performance and potential     

Research on medical applications of nanotechnology in the European Union [Cellular/tissue engineering]

Discusses research on medical applications of nanotechnology in the European Union. Nanobiotechnology is based on the idea that the ability to design synthetic materials on a nanoscale base toward molecular architecture of biologically relevant molecules will ultimately lead to the integration of artificial and biological matter. This concept has applications in the environment, biomedical sensors, and artificial tissues. Biomaterials and medical devices represent a fast emerging market that is estimated at about US$260 billion worldwide, with Europe's share being about 30%. Biomaterial and tissue engineering research are of high quality and in strong competition with the United States, who is still the world leader. The biomimetic approach to developing advanced materials is a new field that provides different solutions to existing challenges. In all living organisms, nature produces a plethora of materials, architectures, systems, and functions, which have been optimized during a long and tough evolution process. An essential feature of these highly structured materials is their structural organization in many scales, as is the case of ceramics and composites found in animal shells or in bone and dental tissues.     

Investigation of Ultrafast Laser--Photonic Material Interactions: Challenges for Directly Written Glass Photonics

Currently, direct-write waveguide fabrication is probably the most widely studied application of femtosecond laser micromachining in transparent dielectrics. Devices such as buried waveguides, power splitters, couplers, gratings, and optical amplifiers have all been demonstrated. Waveguide properties depend critically on the sample material properties and writing laser characteristics. In this paper, we discuss the challenges facing researchers using the femtosecond laser direct-write technique with specific emphasis being placed on the suitability of fused silica and phosphate glass as device hosts for different applications.     

Analysis of cavitation dynamics during pulsed laser tissue ablationby optical on-line monitoring

Flashlamp pumped mid-IR laser systems emitting in the 2-3-μm wavelength range are widely used for various medical applications, especially for tissue ablation. Explosive evaporation is inevitably associated with this process due to the short pulse durations of these laser systems and the high absorption of tissue and water in this spectral regime. Tissue displacement and dissection occur in liquid environment as a consequence of the induced cavitation. Depending on the application these processes might enhance the tissue ablation but can also cause adverse tissue effects. The ablation dynamics were investigated by evaluating the change in reflected probe-light intensity re-emitted from the application fiber tip. The ablated cavity and the signal was correlated to fast-flash photographs of the event. Based on this reflection signal a water/tissue discrimination system is introduced which can widely support medical laser applications. In laser sclerostomy ab externo, for example, this approach can be used as a feedback system to automatically control the ablation process. With such a system, adverse effects to adjacent tissue in the anterior chamber of the eye can be minimized     

An automated laser system for eye surgery

The use of lasers in ophthalmology is discussed, and the procedure and requirements of ophthalmic laser surgery are described. An overview of a proposed laser system for eye surgery is given, and its operation is described. Progress and research to date are reviewed.     

Infrared Scanning Near-Field Optical Microscopy Below the Diffraction Limit

Infrared scanning near-field optical microscopy (IR-SNOM) is an extremely powerful analytical instrument since it combines IR spectroscopy's high chemical specificity with SNOM's high spatial resolution. In order to do this in the infrared, specialty chalcogenide glass fibers were fabricated and their ends tapered to generate SNOM probes. The fiber tips were installed in a modified near-field microscope and both inorganic and biological samples illuminated with the tunable output from a free-electron laser located at Vanderbilt University. Both topographical and IR spectral images were simultaneously recorded with a resolution of ~ 50 and ~ 100 nm, respectively. Unique spectroscopic features were identified in all samples, with spectral images exhibiting resolutions of up to lambda/60, or at least 30 times better than the diffraction limited lens-based microscopes. We believe that IR-SNOM can provide a very powerful insight into some of the most important biomedical research topics.     

Efficient 1.94-μm Tm:YALO laser

Laser emission from Tm:YALO is observed over the range 1.93-2.00 μm. A model including reabsorption loss and polarization effects, predicting the output wavelength as a function of laser parameters, is used to design a Tm:YALO laser with output restricted to 1.94 μm, without employing a tuning element. This laser is potentially useful for medical applications, offing to the strong absorption coefficient at 1.94 μm in liquid water (twice that of the 2.02-μm Tm:YAG laser and four times that of the 2.09-μm Ho:YAG laser)     

Multimodality Molecular Imaging

Molecular imaging is a newly emerging and rapidly developing biomedical imaging field in which the modern technologies and instruments are being merged to study biological and medical processes, as well as diagnosing and managing diseases. In the study of molecular imaging, the three research focuses are the imaging techniques, specific molecular probes, and molecular imaging applications in pathology and pharmacology. Therefore, novel molecular imaging theories and algorithms, new molecular probes, multimodality molecular imaging prototype systems, experiments, and biomedical applications are introduced as a whole project.     

An industry perspective on senior biomedical engineering design courses

Most senior design courses involve lectures covering the various aspects of the typical product development cycle followed by the selection of a design project from one of several areas of biomedical engineering (BME). This article summarizes a four-year relationship between Datex-Ohmeda, Vanderbilt University [the senior design course and VaNTH (Vanderbilt University; Northwestern University; the University of Texas at Austin; and Health, Science and Technology at Harvard/MIT) Engineering Research Center (www.vanth.org) programs], and the cooperative (co-op) and summer internship programs with Marquette University and the University of Wisconsin. The involvement of industry in the senior design curriculum has been beneficial to students, the university, and industry. Datex-Ohmeda has successfully accomplished its goals in working closely with the universities. The company has provided a guest lecturer, projects for the seniors to work on, equipment, and input to the curriculum via the Biomedical Engineering Industrial Board and the VaNTH Engineering Research Council. Datex-Ohmeda has gained input on research projects and the opportunity to look at potential employees.     

High-power continuous-wave 3- and 2-μm cascadeHo3+:ZBLAN fiber laser and its medical applications

A new medical fiber laser oscillating at two useful wavelengths (3 and 2 μm) is reported. We have demonstrated highly efficient and high-power continuous-wave cascade oscillation at room temperature with a holmium ion-doped fluoride glass fiber laser pumped with a 1.15-μm fiber Raman laser. The simultaneous oscillation wavelengths were 3 and 2 μm, and their combined output power was 3.0 W with a slope efficiency of 65%. To our best knowledge, this is the first achievement of watt-level-output power in the mid-infrared region with ZrF₄-BaF₂-LaF₃-AlF₃-NaF (ZBLAN) glass fiber. In experiments to evaluate potential for medical applications, we tested the two wavelength beam as a laser surgical knife on soft rabbit tissues and demonstrated that it had strong cutting capability, and that the coagulation layer thickness could be controlled by varying the power ratio of the two-wavelength laser     

Joint angle control by FES using a feedback error learning controller.

The feedback error learning (FEL) scheme was studied for a functional electrical stimulation (FES) controller. This FEL controller was a hybrid regulator with a feedforward and a feedback controller. The feedforward controller learned the inverse dynamics of a controlled object from feedback controller outputs while control. A four-layered neural network and the proportional-integral-derivative (PID) controller were used for each controller. The palmar/dorsi-flexion angle of the wrist was controlled in both computer simulation and FES experiments. Some controller parameters, such as the learning speed coefficient and the number of neurons, were determined in simulation using an artificial forward model of the wrist. The forward model was prepared by using a neural network that can imitate responses of subject's wrist to electrical stimulation. Then, six able-bodied subjects' wrist was controlled with the FEL controller by delivering stimuli to one antagonistic muscle pair. Results showed that the FEL controller functioned as expected and performed better than the conventional PID controller adjusted by the Chien, Hrones and Reswick method for a fast movement with the cycle period of 2 s, resulting in decrease of the average tracking error and shortened delay in the response. Furthermore, learning iteration was shortened if the feedforward controller had been trained in advance with the artificial forward model.     

Feedback error learning neural network for trans-femoral prosthesis.

Feedback-error learning (FEL) neural network was developed for control of a powered trans-femoral prosthesis. Nonlinearities and time-variations of the dynamics of the plant, in addition to redundancy and dynamic uncertainty during the double support phase of walking, makes conventional control methods very difficult to use. Rule-based control, which uses a knowledge base determined by machine learning and finite automata method is limited since it does not respond well to perturbations and environmental changes. FEL can be regarded as a hybrid control, because it combines nonparametric identification with parametric modeling and control. This paper presents simulation of a powered trans-femoral prosthesis controlled by a FEL neural network. Results suggest that FEL can be used to identify inverse dynamics of an arbitrary trans-femoral prosthesis during simple single joint movements (e.g., sinusoidal oscillations). The identified inverse dynamics then allows the tracking of an arbitrary trajectory such as a desired walking pattern within a multijoint structure. Simulation shows that the identified controller responds correctly when the leg motion is exposed to a perturbation such as a frequent change of the ground reaction force or the hip joint torque generated by the user. FEL eliminates the need for precise, tedious, and complex identification of model parameters.     

Mid-IR Germanium Oxide Fibers for Contact Erbium Laser Tissue Ablation in Endoscopic Surgery

Endoscopic surgical applications of erbium lasers have been limited due to the lack of a suitable mid-IR optical fiber delivery system. Germanium oxide fibers are used for noncontact tissue ablation, but are not recommended for contact tissue ablation applications typically required during endoscopic surgery. This study describes the assembly and characterization of hybrid mid-IR fibers consisting of germanium oxide trunk fibers and sapphire fiber tips, and side-firing germanium oxide fibers with either 45deg angled tips or micromirrors. Average powers up to 8.5 W (850 mJ at 10 Hz) and transmission up to 70% was demonstrated through 450-mum-core, 1.5-m-long fibers, sufficient for endoscopic laser ablation of soft and hard tissues in contact mode.     

Hybrid ultrasonic elastic force motors micromachined in silicon

Abstract

A micromotor for low power applications is being developed using silicon micromachining technologies and organometallic PZT films sol-gel deposition. The construction of a hybrid ultrasonic motor suitable for batch fabrication is proposed. A fabrication process for the stator resonator compatible with both bulk micromachining and 0.3 μm PZT films deposition on a SiNx/Ta/Pt substrate has been tested. Comparison of PZT actuated and previously fabricated ZnO actuated diaphragms are performed using laser interferometry. PZT samples show promising results for applications where a low voltage operation is a key benefit. Poled PZT films are obtained after process completion and influence of DC biases on the resonance frequencies are observed.     

Medical applications of infrared transmitting silver halide fibers

It is clear that infrared transmitting fibers of high quality, with many uses in IR optical systems, can be fabricated from silver halide crystals. The process requires ultrapure starting material and control of extrusion parameters such as temperature and pressure. Under laboratory conditions, fibers have been produced that are usefully transparent from 2-25 μm and have a loss coefficient of less than O.2 dB/m at 10.6 μm. These fibers are flexible, and can be repeatedly bent into small radii circles without loss of transmission. The material is nontoxic, insoluble in water, and has an adequate shelf life. It is also of low cost and can be considered as a "disposable" if necessary. Lengths of several meters have been extruded, and with larger preforms and couplers, length is not a limitation. Further, much is now known of the optical and mechanical properties, and the possibility of laser-fibers is envisaged. These MIR fibers will be useful in many medical procedures, such as laser surgery, noncontact fiber-optic thermometry, and fiber-optic spectrometry. Fiber-optic medical tools based on MIR fibers will be used for diagnosis, therapy, and surgery in minimally invasive systems