Infrared LED Research Articles

VR穿刺トレーニングシステムのための顔位置追跡可能なイメージオーバーレイ環境の構築

The system overlaying the stereoscopic images onto the haptic interface is proposed. In order to develop the tnaining systems based on virtual reality for medical doctors to experience medical treatments, it is important to improve the reality that visual and haptic information are synchronized. Our training system proposed in a previous paper for central venous injection uses the stereoscopic glasses and the haptic interface. This system has a palpation phase and an injection phase. During the injection phase, it is important that the user can see 3D injector images and the stylus of the haptic interface corresponding. In the proposed system, the user can look down the images projected from the display and reflected on the half mirror, and the haptic interface through the mirror. Using infrared LEDs wirelessly attached to the stereoscopic glasses and the infrared camera set under the display, the proposed system can show the 3D images considering with the face position in real-time. This system can achieve higher reality and more effectiveness than our conventional system. This system is evaluated by the experienced medical doctor as effective one.

Infrared imaging of subcutaneous veins

Imaging of subcutaneous veins is important in many applications, such as gaining venous access and vascular surgery. Despite a long history of medical infrared (IR) photography and imaging, this technique is not widely used for this purpose. Here we revisited and explored the capability of near-IR imaging to visualize subcutaneous structures, with a focus on diagnostics of superficial veins. An IR device comprising a head-mounted IR LED array (880 nm), a small conventional CCD camera (Toshiba Ik-mui, Tokyo, Japan), virtual-reality optics, polarizers, filters, and diffusers was used in vivo to obtain images of different subcutaneous structures. The same device was used to estimate the IR image quality as a function of wavelength produced by a tunable xenon lamp-based monochrometer in the range of 500-1,000 nm and continuous-wave Nd:YAG (1.06 microm) and diode (805 nm) lasers. The various modes of optical illumination were compared in vivo. Contrast of the IR images in the reflectance mode was measured in the near-IR spectral range of 650-1,060 nm. Using the LED array, various IR images were obtained in vivo, including images of vein structure in a pigmented, fatty forearm, varicose leg veins, and vascular lesions of the tongue. Imaging in the near-IR range (880-930 nm) provides relatively good contrast of subcutaneous veins, underscoring its value for diagnosis. This technique has the potential for the diagnosis of varicose veins with a diameter of 0.5-2 mm at a depth of 1-3 mm, guidance of venous access, podiatry, phlebotomy, injection sclerotherapy, and control of laser interstitial therapy.

Developments in radiation, stimulation and observation facilities in luminescence measurements

This paper summarises recent developments in the Risø TL/OSL reader. These new developments include an elevated temperature irradiation facility that has been expanded to measure variable temperature radioluminescence (RL) during beta irradiation. This RL facility allows the measurement of TL, OSL and RL in the same software-controlled automatic sequence. To provide an alternative to the 90 Sr beta source, the performance of a software-controlled mini X-ray generator has been investigated. This has the advantage of providing a range of dose rates spanning more than three orders of magnitude up to more than 2 Gy/ s . A separate bleaching facility has also been added to the reader, new powerful infrared (IR) light-emitting diodes have replaced the IR laser diode in the general OSL unit, and an IR laser has been included in the single-grain OSL attachment. This paper describes these new facilities, and illustrates their applications with representative measurements.

Non-linear viscoelastic models predict fingertip pulp force-displacement characteristics during voluntary tapping

We evaluated whether lumped-parameter non-linear viscoelastic models of human fingertip tissue can describe fingertip force-displacement characteristics during a range of rapid, dynamic tapping tasks. Eight human subjects tapped with their index finger on the surface of a rigid load cell while an optical system tracked fingertip position using an infra-red LED attached to the fingernail. Four different tapping conditions were tested: normal and high-speed taps with a relaxed hand, and normal and high-speed taps with the other fingers co-contracted. A non-linear viscoelastic model comprised of an instantaneous stiffness function and viscous relaxation function was capable of predicting fingertip tissue force response due to measured pulp compression under these four different loading conditions. The model could successfully reconstruct very rapid (less than 5 ms) force transients, and forces occurring over time periods greater than 100 ms, with errors of 10%. Model parameters varied by less than 20% over the four conditions, despite almost 3-fold differences in average forces and 38% differences in fingertip velocities. Energy dissipation by the fingertip averaged 81%, and varied little (<3%) across conditions, despite a 1. 5-fold range of energy input. The ability of a lumped-parameter model to describe fingertip force-displacement characteristics during a range of conditions contributes both to understanding the transmission of force through the fingertip to the musculoskeletal system and to predicting the stimulation of mechano-receptors located within the fingertip.

Current crowding in InAsSb light-emitting diodes

High-resolution two-dimensional infrared (IR) imaging of dynamic electronic processes in the surface-emitting p-InAsSb/n-InAsSbP light-emitting diodes (LEDs) (λ=4.3 μm, T&amp;gt;300 K) showed that forward current crowding drastically decreases efficiency of LEDs with point contacts. Current flows and IR emittance “forget” the emitting area size and geometry, whereas extended areas far off the point contacts become even “darker” with the current increase. Contrary to this, the reverse bias causes remarkable current spreading and uniform “negative emittance” distribution. Therefore the negative luminescence mode is more favorable for IR LEDs operating at higher temperatures.

The use of infra-red light-modulated temperature in DSC created by pulse-width modulation

Infra-red light, generated by diodes, is applied to produce a sinusoidal temperature modulation in the standard heat-flux DSC of TA instruments. The temperature of the sample and reference are controlled by both, the original temperature controller of the instrument, and by the radiant energy generated by two high-power infra-red light-emitting diodes (LEDs). This allows for isothermal or quasi-isothermal experimentation in the standard mode of operation of the calorimeter. The additional infra-red irradiation is provided only for temperature modulation. The radiant energy transferred to the specimens is controlled by pulse-width modulation (PWM) which provides a high linearity in the temperature modulation program. This feature enables to obtain any arbitrary temperature profile with the limits of frequency set by the calorimeter response and speed of the computer. Simple electronics and a computer algorithm for the PWM control are described. The method was tested in the melting range of indium and by measurement of the heat capacity of sapphire (Al 2O 3) and polystyrene. The problem of frequency correction arising from a wide frequency range is analyzed and discussed.

Local Fundus Response to Blue (LED and Laser) and Infrared (LED and Laser) Sources

Light damage research began during the early years of laser light exploration. There is a clear and significant literature that identifies an easily demonstrated retina-pigment epithelium pathology which is associated with short wavelength exposures below 520nm. Recent interest has expanded because of the growing evidence for a blue light contribution to the retina aging process by way of a poorly understood chemical process(es) that involve circulation, oxidative reactions and the spectral absorption properties of the pigment epithelium. New powerful sources of relatively inexpensive blue energy have become available as a family of light emitting diodes. In this experiment, we examined funduscopic, angiographic and scanning laser tomographic measures of the retinal-pigment epithelium response to LED and laser spectral blue and infrared emissions closely matched in wavelengths and delivered under carefully matched circumstances. Ten retinas in normal young rhesus monkeys were locally exposed to various energy density values at 458nm (Argon laser) ranging from 5 to 54Jcm−2. Eight rhesus eyes were exposed to LED irradiation with a peak wavelength of 460nm ranging from 9 to 62Jcm−2. Similarly, a matched infrared (IR) laser and IR LED pair were used to expose an additional ten eyes for comparison of the long wavelengths. IR irradiance ranged from 21 to 306Jcm−2. There was no response to IR exposure in any of the eyes. Blue light exposure results were measured from the color fundus photographs, scanning laser tomographs and early- and late-phase fluorescein angiogram responses at 2 and 30 days after the exposure. Results scores were accumulated for the four measures at the two time periods. The resulting lesion scores when plotted against the exposure in Jcm−2showed no demonstrable effect at irradiance lower than 10Jcm−2and near 100% effectiveness for irradiance greater than 30Jcm−2. The most sensitive and enduring indicator of change was the late fluorescein angiograms. Nonparametric statistical analysis of the scores from the two samples support the conclusion that there is no difference in the consequences of LED and laser light exposures under these matched conditions.

Calibration of three-dimensional ultrasound images for image-guidedradiation therapy

A new technique of patient positioning for radiotherapy/radiosurgery ofextracranial tumours using three-dimensional (3D) ultrasound images has beendeveloped. The ultrasound probe position is tracked within the treatment roomvia infrared light emitting diodes (IRLEDs) attached to the probe. In order toretrieve the corresponding room position of the ultrasound image, we developedan initial ultrasound probe calibration technique for both 2D and 3Dultrasound systems. This technique is based on knowledge of points in bothroom and image coordinates.We first tested the performance of three algorithms in retrieving geometricaltransformations using synthetic data with different noise levels. Closed formsolution algorithms (singular value decomposition and Horn's quaternionalgorithms) were shown to outperform the Hooke and Jeeves iterative algorithmin both speed and accuracy. Furthermore, these simulations show that for arandom noise level of 2.5, 5, 7.5 and 10 mm, the number of points required fora transformation accuracy better than 1 mm is 25, 100, 200 and 500 pointsrespectively. Finally, we verified the tracking accuracy of this system usinga specially designed ultrasound phantom.Since ultrasound images have a high noise level, we designed an ultrasoundphantom that provides a large number of points for the calibration. Thistissue equivalent phantom is made of nylon wires, and its room position isoptically tracked using IRLEDs. By obtaining multiple images through the nylonwires, the calibration technique uses an average of 300 points for 3Dultrasound volumes and 200 for 2D ultrasound images, and its stability is verygood for both rotation (standard deviation: 0.4°) and translation(standard deviation: 0.3 mm) transformations. After this initial calibrationprocedure, the position of any voxel in the ultrasound image volume can bedetermined in world space, thereby allowing real-time image guidance oftherapeutic procedures. Finally, the overall tracking accuracy of our3D ultrasound image-guided positioning system was measured to be on average0.2 mm, 0.9 mm and 0.6 mm for the AP, lateral and axial directions respectively.

A high-precision system for conformal intracranial radiotherapy

Purpose: Currently, optimally precise delivery of intracranial radiotherapy is possible with stereotactic radiosurgery and fractionated stereotactic radiotherapy. We report on an optimally precise optically guided system for three-dimensional (3D) conformal radiotherapy using multiple noncoplanar fixed fields. Methods and Materials: The optically guided system detects infrared light emitting diodes (IRLEDs) attached to a custom bite plate linked to the patient’s maxillary dentition. The IRLEDs are monitored by a commercially available stereo camera system, which is interfaced to a personal computer. An IRLED reference is established with the patient at the selected stereotactic isocenter, and the computer reports the patient’s current position based on the location of the IRLEDs relative to this reference position. Using this readout from the computer, the patient may be dialed directly to the desired position in stereotactic space. The patient is localized on the first day and a reference file is established for 5 different couch positions. The patient’s image data are then imported into a commercial convolution-based 3D radiotherapy planning system. The previously established isocenter and couch positions are then used as a template upon which to design a conformal 3D plan with maximum beam separation. Results: The use of the optically guided system in conjunction with noncoplanar radiotherapy treatment planning using fixed fields allows the generation of highly conformal treatment plans that exhibit a high degree of dose homogeneity and a steep dose gradient. To date, this approach has been used to treat 28 patients. Conclusion: Because IRLED technology improves the accuracy of patient localization relative to the linac isocenter and allows real-time monitoring of patient position, one can choose treatment-field margins that only account for beam penumbra and image resolution without adding margin to account for larger and poorly defined setup uncertainty. This approach enhances the normal tissue sparing, high degree of conformality, and homogeneity characteristics possible with 3D conformal radiotherapy.

Image localization for frameless stereotactic radiotherapy

Purpose: Infrared light-emitting diodes (IRLEDs) have been used for optic-guided stereotactic radiotherapy localization at the University of Florida since 1995. The current paradigm requires stereotactic head ring placement for the patient’s first fraction. The stereotactic coordinates and treatment plan are determined relative to this head ring. The IRLEDs are attached to the patient via a maxillary bite plate, and the position of the IRLEDs relative to linac isocenter is saved to file. These positions are then recalled for each subsequent treatment to position the patient for fractionated therapy. The purpose of this article was to report a method of predicting the desired IRLED locations without need for the invasive head ring. Methods and Materials: To achieve the goal of frameless optic-guided radiotherapy, a method is required for direct localization of the IRLED positions from a CT scan. Because it is difficult to localize the exact point of light emission from a CT scan of an IRLED, a new bite plate was designed that contains eight aluminum fiducial markers along with the six IRLEDs. After a calibration procedure to establish the spatial relationship of the IRLEDs to the aluminum fiducial markers, the stereotactic coordinates of the IRLED light emission points are determined by localizing the aluminum fiducial markers in a stereotactic CT scan. Results: To test the accuracy of direct CT determination of the IRLED positions, phantom tests were performed. The average accuracy of isocenter localization using the IRLED bite plate was 0.65 ± 0.17 mm for these phantom tests. In addition, the optic-guided system has a unique compatibility with the stereotactic head ring. Therefore, the isocentric localization capability was clinically tested using the stereotactic head ring as the absolute standard. The ongoing clinical trial has shown the frameless system to provide a patient localization accuracy of 1.11 ± 0.3 mm compared with the head ring. Conclusion: Optic-guided radiotherapy using IRLEDs provides a mechanism through which setup accuracy may be improved over conventional techniques. To date, this optic-guided therapy has been used only as a hybrid system that requires use of the stereotactic head ring for the first fraction. This has limited its use in the routine clinical setting. Computation of the desired IRLED positions eliminates the need for the invasive head ring for the first fraction. This allows application of optic-guided therapy to a larger cohort of patients, and also facilitates the initiation of extracranial optic-guided radiotherapy.

Temperature characteristics of near-infrared (1.7 micron), resonant cavity light-emitting diodes

The design and operation of a near infra-red resonant cavity light-emitting diode operating at 1.7 microns with a 16 nm linewidth is described. The structure is based on a wafer-bonded combination of InGaAs/InAlAs/InP quantum well emitter and an AlAs/GaAs distributed Bragg reflector. Detailed temperature characteristics over a range from 80 to 373 K are presented. The temperature dependence of the main cavity mode emission wavelength is shown to be 0.15 nm/K. The intensity is found to increase with temperature from 80 to 325 K and thereafter decrease. There is a 20 degree range in which the intensity is constant within approximately 5%. A model is suggested for this behaviour.

Use of Near Infrared Transmittance to Automatically Detect Almonds with Concealed Damage

A near infrared inspection system was built to automatically detect whole almond kernels with concealed damage at an inspection rate of 40 nuts/s. The inspection device detects transmitted light through whole almonds from six different near infrared LEDs using a sine wave modulation–demodulation scheme. Multiple linear regression and discriminant analysis to classify nuts as concealed damaged or undamaged was performed. A classification error rate of 14.3% on the validation set was obtained with discriminant analysis, and a classification error rate of 20.0% was obtained with regression analysis. Most of the incorrectly classified nuts were those where it was difficult to objectively determine if they were damaged or undamaged.

Optical tracking of a microscope for image-guided intranasal sinus surgery.

The objective of this study was to examine the effects of optical and tracking properties on the accuracy of an optically locatable operating microscope. The intraoperative arrangement was based on experimental results obtained from a skull model. Measurements were taken from 24 patients undergoing intranasal microscopic sinus surgery for various disorders. Two major groups of influencing factors were determined from measurements on the model: 1) optical properties of the microscope, such as the method of focal point adjustment, focal length, and magnification of the lens; and 2) tracking properties of the microscope, such as the distance of the digitizer to the tracked object, the number of reference infrared light-emitting diodes (IR-LEDs), and the area circumscribed by these IR-LEDs. Patient measurements showed an overall spatial error of 2.39+/-1.15 mm with a laser-supported adjustment of the focal point of the microscope. Although the associated 95th percentile was at 4.36 mm, such a value is encouraging for further development of microscopically navigable systems. It must be noted that the noninvasive patient-to-image registration was performed on the basis of a computed tomographic image with a slice distance of 2 mm.

Preliminary experience with frameless stereotactic radiotherapy

Purpose: To report initial clinical experience with a novel high-precision stereotactic radiotherapy system. Methods and Materials: Sixty patients ranging in age from 2 to 82 years received a total of 1426 treatments with the University of Florida frameless stereotactic radiotherapy system. Of the total, 39 (65%) were treated with stereotactic radiotherapy (SRT) alone, and 21 (35%) received SRT as a component of radiotherapy. Pathologic diagnoses included meningiomas (15 patients), low-grade astrocytomas (11 patients), germinomas (9 patients), and craniopharyngiomas (5 patients). The technique was used as means of dose escalation in 11 patients (18%) with aggressive tumors. Treatment reproducibility was measured by comparing bite plate positioning registered by infrared light-emitting diodes (IRLEDs) with the stereotactic radiosurgery reference system, and with measurements from each treatment arc for the 1426 daily treatments (5808 positions). We chose 0.3 mm vector translation error and 0.3° rotation about each axis as the maximum tolerated misalignment before treating each arc. Results: With a mean follow-up of 11 months, 3 patients had recurrence of malignant disease. Acute side effects were minimal. Of 11 patients with low grade astrocytomas, 4 (36%) had cerebral edema and increased enhancement on MR scans in the first year, and 2 required steroids. All had resolution and marked tumor involution on follow-up imaging. Bite plate reproducibility was as follows. Translational errors: anterior-posterior, 0.01 ± 0.10; lateral, 0.02 ± 0.07; axial, 0.01 ± 0.10. Rotational errors (degrees): anterior-posterior, 0.00 ± 0.03; lateral, 0.00 ± 0.06; axial, 0.01 ± 0.04. No patient treatment was delivered beyond the maximum tolerated misalignment. Daily treatment was delivered in approximately 15 min per patient. Conclusion: Our initial experience with stereotactic radiotherapy using the infrared camera guidance system was good. Patient selection and treatment strategies are evolving rapidly. Treatment accuracy was the best reported, and the treatment approach was practical.

IRLED-Based Patient Localization for Linac Radiosurgery

Purpose: Currently, precise stereotactic radiosurgery delivery is possible with the Gamma Knife or floor-stand linear accelerator (linac) systems. Couch-mounted linac radiosurgery systems, while less expensive and more flexible than other radiosurgery delivery systems, have not demonstrated a comparable level of precision. This article reports on the development and testing of an optically guided positioning system designed to improve the precision of patient localization in couch-mounted linac radiosurgery systems. Methods and Materials: The optically guided positioning system relies on detection of infrared light-emitting diodes (IRLEDs) attached to a standard target positioner. The IRLEDs are monitored by a commercially available camera system that is interfaced to a personal computer. An IRLED reference is established at the center of stereotactic space, and the computer reports the current position of the IRLEDs relative to this reference position. Using this readout from the computer, the correct stereotactic coordinate can be set directly. Results: Bench testing was performed to compare the accuracy of the optically guided system with that of a floor-stand system, that can be considered an absolute reference. This testing showed that coordinate localization using the IRLED system to track translations agreed with the absolute to within 0.1 ± 0.1 mm. As rotations for noncoplanar couch angles were included, the inaccuracy was increased to 0.2 ± 0.1 mm. Conclusions: IRLED technology improves the accuracy of patient localization relative to the linac isocenter in comparison with conventional couch-mounted systems. Further, the patient’s position can be monitored in real time as the couch is rotated for all treatment angles. Thus, any errors introduced by couch inaccuracies can be detected and corrected.

The university of Florida frameless high-precision stereotactic radiotherapy system

To develop and test a system for high precision fractionated stereotactic radiotherapy that separates immobilization and localization devices. Patient localization is achieved through detection and digital registration of an independent bite plate system. The bite plate is made and linked to a set of six infrared light emitting diodes (IRLEDs). These IRLEDs are detected by an infrared camera system that identifies the position of each IRLED within 0.1 to 0.15 mm. Calibration of the camera system defines isocenter and translational X, Y, and Z axes of the stereotactic radiosurgery subsystem and thereby digitally defines the virtual treatment room space in a computer linked to the camera system. Positions of the bite plate's IRLEDs are processed digitally using a computer algorithm so that positional differences between an actual bite plate position and a desired position can be resolved within 0.1 mm of translation (X, Y, and Z distance) and 0.1 degree of rotation. Furthermore, bite plate misalignment can be displayed digitally in real time with translational (x, y, and z) and rotational (roll, pitch, and yaw) parameters for an actual bite plate position. Immobilization is achieved by a custom head mold and thermal plastic mask linked by hook-and-loop fastener tape. The head holder system permits rotational and translational movements for daily treatment positioning based on the bite plate localization system. Initial testing of the localization system was performed on 20 patients treated with radiosurgery. The system was used to treat 11 patients with fractionated stereotactic radiotherapy. Assessment of bite plate localization in radiosurgery patients revealed that the patient's bite plate could be positioned and repositioned within 0.5 +/- 0.3 mm (standard deviation). After adjustments, the first 11 patients were treated with the bite plate repositioning error reduced to 0.2 +/- 0.1 mm. High precision stereotactic radiotherapy can be delivered using separate localization and immobilization systems. Treatment setup and delivery can be accomplished in 15 min or less. Advantages compared with standard systems require further study.

Cross-modality matches of finger span and line length.

Perceived finger span--the perceived spatial separation between the tip of the thumb and the tip of the index finger--was measured by using cross-modal matching to line length. In the first experiment, subjects adjusted finger span to match the length of line segments presented on a video monitor, and conversely, with both hands. Subjects also made estimates of finger span in physical units ("dead reckoning"). Finger spans were measured by using infrared LEDs mounted on the tip of the thumb and the finger tip, so the hand made no contact with any object during the experiment. Unlike in previous studies, the results suggest that perceived finger span is proportional to line length and slightly shorter than the actual span, provided that corrections are made for regression bias. The effect of finger contact was assessed in a second experiment by matching line length both to free span and to spans constrained by the pinching of blocks in the same session. The matching function when subjects were pinching blocks was accelerating, consistent with previous reports. In contrast, matched line length was a decelerating function of free span. The exponent of the free span matching function in the second experiment was slightly smaller than in the first experiment, probably due to uncorrected matching biases in the second experiment.

ＬＥＤ灯台を用いた移動ロボット用位置姿勢検出システム

A sensor system to measure position and the orientation of a mobile robot has been developed. The system measures the robot's position and orientation every 40 msec with an accuracy of 10 mm, in range of 1.5m radius. In this system two or more infra-red LED marks are placed on the ceiling, and a 2D PSD sensor on the mobile robot faces toward them. The PSD senses relative position of a spot light from the mark, and the position and orientation of the PSD are calculated from the relative po-sition of the marks. Since pitching or rolling of the camera affects the 2D measurement, 3D measurement is incorporated. 3D position and orientation are calculated geometrically, using 3 marks. The emission of LED mark is controlled from the robot by sending infra-red light to the marks. Furthermore, lock-in amplifier is used to improve accuracy.

Er-Implanted Porous Silicon: a Novel Material for Si-Based Infrared LEDs

ABSTRACTWe have demonstrated a strong, room-temperature, 1.54 μm emission from erbium-implanted at 190 keV into red-emitting porous silicon. Luminescence data showed that the intensity of infrared (IR) emission from Er implanted porous Si annealed at ≤ 650°C, was a few orders of magnitude stronger than Er implanted quartz produced under identical conditions, and was almost comparable to IR emission from In0.53Ga0.47As material which is used for commercial IR light-emitting diodes (LEDs).The strong IR emission (much higher than Er in quartz) and the weak temperature dependency of Er in porous Si, which is similar to Er3+ in wide-bandgap semiconductors, suggests that Er is not in SiO2 or Si with bulk properties but, may be confined in Si light-emitting nanostructures. Porous Si is a good substrate for rare earth elements because: 1) a high concentration of optically active Er3+ can be obtained by implanting at about 200 keV, 2) porous Si and bulk Si are transparent to 1.54 μm emission therefore, device fabrication is simplified, and 3) although the external quantum efficiency of visible light from porous Si is compromised because of self-absorption, it can be used to pump Er3+.

An integrated procedure to assess knee-joint kinematics and kinetics during gait using an optoelectric system and standardized X-rays

This paper describes a 3-D gait analysis system, which combines optoelectric motion tracking and a standardized X-ray procedure, to calculate the net knee-joint forces and moments of a normal subject group during walking. The optoelectric system collects kinematic data from infra-red LED markers placed at selected skin surface locations and projecting probes attached to the lower limb. A standardized X-ray procedure is used to move surface markers into their designated bony landmarks based on individual bone structure, which reduces the error caused by uncertainty of skin-surface marker locations. Based on moved-in marker information, different joint coordinate systems are proposed for kinematic and kinetic analysis of the knee joint. Normalized data of knee angles, net reaction forces and net moments from 35 young, normal subjects are presented.