Optimization of electromagnetic phased-arrays for hyperthermia via magnetic resonance temperature estimation

A technique for the optimization of electromagnetic annular phased arrays (APAs) for therapeutic hyperthermia has been developed and implemented. The controllable inputs are the amplitudes and phases of the driving signals of each element of the array. Magnetic resonance imaging (MRI) is used to estimate noninvasively the temperature distribution based on the temperature dependence of the proton resonance frequency (PRF). A parametric model of the dynamics that couple the control inputs to the resultant temperature elevations is developed based on physical considerations. The unknown parameters of this model are estimated during a pretreatment identification phase and can be continuously updated as new measurement data become available. Based on the parametric model, a controller automatically chooses optimal phases and amplitudes of the driving signals of the APA. An advantage of this approach to optimizing the APA is that no a priori information is required, eliminating the need for patient-specific computational modeling and optimization. Additionally, this approach represents a first step toward employing temperature feedback to make the optimization of the APA robust with respect to modeling errors and physiological changes. The ability of the controller to choose therapeutically beneficial driving amplitudes and phases is demonstrated via simulation. Experimental results are presented which demonstrate the ability of the controller to choose optimal phases for the APA using only information from magnetic resonance thermometry (MRT).     

Source-detector calibration in three-dimensional Bayesian optical diffusion tomography

Optical diffusion tomography is a method for reconstructing three-dimensional optical properties from light that passes through a highly scattering medium. Computing reconstructions from such data requires the solution of a nonlinear inverse problem. The situation is further complicated by the fact that while reconstruction algorithms typically assume exact knowledge of the optical source and detector coupling coefficients, these coupling coefficients are generally not available in practical measurement systems. A new method for estimating these unknown coupling coefficients in the three-dimensional reconstruction process is described. The joint problem of coefficient estimation and three-dimensional reconstruction is formulated in a Bayesian framework, and the resulting estimates are computed by using a variation of iterative coordinate descent optimization that is adapted for this problem. Simulations show that this approach is an accurate and efficient method for simultaneous reconstruction of absorption and diffusion coefficients as well as the coupling coefficients. A simple experimental result validates the approach.     

Steroidogenesis in bovine granulosa cells: the effect of short-term changes in dietary intake

The nutritional status of a cow is a key factor in the regulation of both follicle growth and oocyte quality. In this study, the effect of diets designed to increase circulating insulin and insulin-like growth factor I (IGF-I) concentrations on steroid production by granulosa cells in vitro was examined to analyse the mechanisms through which these changes occur. Hereford x Friesian heifers (n = 24) were offered maintenance or twice maintenance diets during the experimental period (17 days). Circulating concentrations of FSH did not differ between the two dietary groups, whereas insulin and IGF-I concentrations showed significant diet x day of oestrous cycle interactions. Ovaries were collected on day 3 of the first follicle wave after synchronization of oestrus. Granulosa cells were isolated from small (1-4 mm) and medium-sized (4-8 mm) follicles and cultured in the presence of long R3-IGF-I or bFSH or both. After 4 days in culture, granulosa cells isolated from small follicles, but not medium-sized follicles, collected from cattle offered the twice maintenance diet secreted significantly higher (P < 0.05) amounts of oestradiol compared with granulosa cells collected from cattle offered the maintenance diet. The effect was apparent in either the presence or absence of FSH and long R3-IGF-I. This nutritional effect on aromatase activity in granulosa cells was not apparent after day 6 of culture. There was no effect of diet on progesterone production by granulosa cells after 4 or 6 days of culture. These results support the hypothesis that dietary-induced changes in circulating insulin and IGF-I concentrations have a direct effect on the steroidogenic potential of bovine granulosa cells from small follicles. The dietary-induced increases in aromatase activity in small follicles combined with the increased concentration of metabolic hormones are possible mechanisms through which short-term changes in nutrition may affect follicle dynamics.     

Ink‐jet printing: The route to production of full‐color P‐OLED displays

Abstract— Ink‐jet‐printing technology for displays has been making rapid progress and is now nearing production. This paper will go through the developments that have been carried out at CDT, Ltd., to achieve this status. The ink‐jet head and machine development that underpin the capability of the RGB printing process to manufacture P‐OLEDs at high speed with high reliability and with the film‐forming properties to achieve the appropriate device performance will be described. The important contribution made by the availability of flexible metrological tools will be discussed.     

Forget the funny glasses [autostereoscopic display systems]

Shutter glasses, polarized glasses, and head-mounted displays (HMDs) have become common technologies for providing the illusion of 3D. Shutter glasses, popularized by StereoGraphics as CrystalEyes, use an LCD shutter over each eye to enable stereo viewing. The shutters are rendered alternately opaque and transparent so that only one eye can see through the glasses at any moment. The glasses are synchronized to the display system presenting the right and left images at the same frequency as the shutters' phase shifts. These systems can work with televisions, computer monitors, or projectors, but require that the display system can generate images at twice the frequency desired for viewing, because each frame must be shown twice (once for each eye). Although they can cause some loss of image brightness and can suffer from crosstalk, shutter glasses work well and permit full-spectrum color. However, especially with low-cost systems, they can cause eyestrain and other discomfort. In addition, the eyewear is bulky and often heavy, which makes using shutter glasses for long periods of time somewhat uncomfortable. Autostereoscopic displays (ASDs) use several technologies to present different images to both of a viewer's eyes. Volumetric display systems (VDSs) create an image with true depth, letting the eyes and brainwork in natural manner. ASD and VDS systems are intended to replace current 3D displays, all of which require the user to wear some sort of filtering system, such as eyeglasses.     

Rotary encoding for intravascular ultrasonic imaging systems

Images produced with an intravascular ultrasound system (IVUS) can be distorted because of uncertainty in the instantaneous angular position of a rotating ultrasonic transducer. A rotary encoder placed in proximity to the transducer is required to detect the problem; however, size constraints make a conventional electromechanical or optomechanical encoder difficult to implement. Measurements that test the feasibility of a software-derived encoder, based of the rate of decorrelation of ultrasonic RF lines with angle, are reported. Provided that the instantaneous angular velocity of the transducer can be measured, adjustments can be made to the pulse rate of the transducer, which would eliminate the image distortion.     

Laboratory facilities and recommendations for the characterization of biological ultraviolet dosimeters

A laboratory facility for characterizing biological dosimeters for the measurement of UV radiation has been built and tested. The facility is based on a solar simulator, stabilized by photofeedback, and monitored by a spectroradiometer, with a versatile filter arrangement. This enables the following characteristics of the dosimeters to be ascertained: spectral response, linearity, and reciprocity; angular acceptance and response; calibration in simulated sunlight. The system has been tested on a variety of dosimeters and has the potential to be used with other radiometers, subject currently to the size of their active surface.     

Variability of Stress in Alumina Corrosion Layers Formed in Thermal-Barrier Coatings

Residual stress distributions have been measured and mapped usingphotoluminescence, piezo spectroscopy in thermally grown alumina oxides(TGO) formed on platinum-aluminide bond coats with thermal-barrier coatings(TBC) of thickness 0, 3, and 200 m. When there is a 3-m TBC or noTBC, the residual stress varies substantially with position and the meanstress is much lower than expected from simple thermoelastic, plane-stressanalysis. This is partly explained by the stress being relaxed by surfaceroughness, but stress mapping indicates that local fracture hasoccurred. The stress in the TGO formed under 200 m TBCs appear muchmore uniform and the mean value is approximately equal to the estimatedthermoelastic plane stress. This could be due to the extra constraintimposed by the TBC. The luminescence line width is much greater forspecimens with 200-m TBC and is too large to be explained by varyingmacroscopic stresses due to interface roughness. The effects of oxidationtime and reactive-element additions to the substrate at the level of30 ppm, on the residual stress, are relatively minor over the rangesexplored in these experiments.     

Monitoring temperature changes in capillary electrophoresis with nanoliter-volume NMR thermometry

Nanoliter-volume proton nuclear magnetic resonance (NMR) spectroscopy is used to monitor the electrolyte temperature during capillary electrophoresis (CE). By measuring the shift in the proton resonance frequency of the water signal, the intracapillary temperature can be recorded noninvasively with subsecond temporal resolution and spatial resolution on the order of 1 mm. Thermal changes of more than 65 degrees C are observed under both equilibrium and nonequilibrium conditions for typical CE separation conditions. Several capillary and buffer combinations are examined with external cooling by both liquid and air convection. Additionally, NMR thermometry allows nonequilibrium temperatures in analyte bands to be monitored during a separation. As one example, a plug of 1 mM NaCl is injected into a capillary filled with 50 mM borate buffer. Upon reaching the NMR detector, the temperature in the NaCl band is more than 20 degrees C higher than the temperature in the surrounding buffer. Such observations have direct applicability to a variety of studies, including experiments which utilize sample stacking and isotachophoresis.     

Video-rate confocal scanning laser microscope for imaging human tissues in vivo

We have built a video-rate confocal scanning laser microscope for reflectance imaging of human skin and oral mucosa in vivo. Design and imaging parameters were determined for optimum resolution and contrast. Mechanical skin-holding fixtures and oral tissue clamps were made for stable objective lens-to-tissue contact such that gross tissue motion relative to the microscope was minimized. Confocal imaging was possible to maximum depths of 350 mum in human skin and 450 mum in oral mucosa, with measured lateral resolution of 0.5-1 mum and axial resolution (section thickness) of 3-5 mum at the 1064-nm wavelength. This resolution is comparable with that of conventional microscopy of excised biopsies (histology). Normal and abnormal tissue morphology and dynamic processes were observed.