نتایج جستجو برای: focal spot size
تعداد نتایج: 644850 فیلتر نتایج به سال:
Integral relations to describe the propagation of a TE-wave from an external point source through the two-dimensional medium (plane interface) and the plane-parallel plate are proposed. We discuss three types of waves that contribute to the resulting light field, namely, the propagating waves and the firstand second-type surface waves. The comparison of near-field refractive lenses (SIL, NAIL) ...
Modeling and experimental results of an ultrasonic aperiodic flat lens for use in air are presented. Predictive modeling of the lens is performed using a hybrid genetic-greedy algorithm constrained to a linear structure. The optimized design parameters are used to fabricate a lens. A method combining a fiber-disk arrangement and scanning laser vibrometer measurements is developed to characteriz...
Modern day Stereotactic treatments require high geometric accuracy of the delivered treatment. To achieve the required accuracy the IGRT imaging isocenter needs to closely coincide with the treatment beam isocenter. An influence on this isocenter coincidence and on the spatial positioning of the beam itself is the alignment of the treatment beam focal spot with collimator rotation axis. The pos...
Several ultrasound-based imaging modalities have been proposed for image guidance and monitoring of high-intensity focused ultrasound (HIFU) treatment. However, accurate localization and characterization of the effective region of treatment (focal spot) remain important obstacles in the clinical implementation of HIFU ablation. Harmonic motion imaging for focused ultrasound (HMIFU) is a HIFU mo...
Most cultured cells used for biomedical research are cultured adherently, and the requisite detachment prior to biochemical analysis might induce chemical changes. This is especially crucial if accurate metabolic measurements are desired, given the rapid turnover of metabolites in living organisms. There are only a few methods available for the nontargeted in situ analysis of small adherent cel...
The StereoLithography (SL) process has benefited from many advances in the last four to five years. These include new resins with reduced shrinkage and curl distortion, enhanced software, and improved scanning techniques. One can produce highly accurate parts for most dimensions within a few mils of the design value as shown in numerous accuracy and benchmarking studies. SLA systems use a laser...
PURPOSE Megavoltage photon beams are typically used for therapy because of their skin sparing effect. However, a focused low-energy x-ray beam would also be skin sparing, and would have a higher dose concentration at the focal spot. Such a beam can be produced with polycapillary optics. MCNP5 was used to model dose profiles for a scanned focused beam, using measured beam parameters. The potenti...
A study of high-NA focusing process ultrashort laser pulses in bulk ZnSe has been carried out. It is shown that when Gaussian beam with high-aperture lenses into a transparent medium aberration distortions occur leading to an increase focal spot size. The results experimental studies on ablation front and back surfaces plane-parallel plate 4 mm thickness made by duration 0.3 ps, 1 10 ps wavelen...
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