Plotting of Isodose Curves

Over the last decade, two-photon microscopy (TPM) has been the technique of choice for in vivo noninvasive optical brain imaging for neuroscientific study or intra-vital microendoscopic imaging for clinical diagnosis or surgical guidance because of its intrinsic capability of optical sectioning for imaging deeply below the tissue surface with sub-cellular resolution. However, most of these research activities and clinical applications are constrained by the bulky size of traditional TMP systems. An attractive solution is to develop miniaturized TPMs, but this is challenged by the difficulty of the integration of dynamically scanning optical and mechanical components into a small space. Fortunately, microelectromechanical systems (MEMS) technology, together with other emerging micro-optics techniques, has offered promising opportunities in enabling miniaturized TPMs. In this paper, the latest advancements in both lateral scan and axial scan techniques and the progress of miniaturized TPM imaging will be reviewed in detail. Miniature TPM probes with lateral 2D scanning mechanisms, including electrostatic, electromagnetic, and electrothermal actuation, are reviewed. Miniature TPM probes with axial scanning mechanisms, such as MEMS microlenses, remote-focus, liquid lenses, and deformable MEMS mirrors, are also reviewed.

It is proposed in this paper to use phase only liquid crystal spatial light modulators to realize non-mechanical lateral and axial confocal microscopic laser scanning. With a phase only liquid crystal spatial light modulator used as a scanner to realize laser beam deflection, a confocal microscopic lateral beam scanning system is designed. A zoom illuminating lens is formed by incorporating a liquid crystal spatial light modulator along the confocal illumination light path, and thus the focus of the objective lens is axially shifted to realize the axial non-mechanical scanning. The theoretical analyses indicate that phase only liquid crystal spatial light modulators can be used to realize non-mechanical 3D confocal microscopic laser scanning.

This study aims to improve a way for reducing backscattered radiation in an X-ray room. An iron steel grid, capable to absorb a significant portion of the backscattered radiation, was used. X-ray machine as a source for radiation was directed normally on the phantom, and the backscattered radiation was measured by using ion chamber. The measurements were recorded at various applied voltages (60 kvp to 120 kvp) and the fabricated grid was designed from iron steel constructed of perpendicular parallel strips mounted on a base. The results indicated that the use of iron steel grid was very effective in the reduction of backscattered radiation in an X-ray room up to about 46% by using fabricated iron steel grid.

In this thesis, two inversion-based feedforward control approaches have been developed and implemented to high-speed large-range atomic force microscope (AFM) imaging and nanofabrication, respectively. High-speed large-range AFM imaging and nanofabrication are needed in many areas and have attracted great interests. Challenges, however, must be overcome because in high-speed largerange AFM operation, large positioning error of the AFM probe relative to the sample can be generated due to the adverse effects of the hardware. The nonlinear hysteresis and the vibrational dynamics effects of the piezotube actuator must be addressed during the high-speed lateral scanning of the AFM imaging over large imaging size. In addition, precision positioning of the AFM probe in the vertical direction is even more challenging (than the lateral scanning) because the desired trajectory (i.e., the sample topography profile) is unknown in general, and the probe positioning is also effected by and sensitive to the probe-sample interaction. Finally, in AFM multi-axis nanofabrication, additional positioning errors are induced by the large cross-axis dynamics coupling effect. The large positioning errors generated during high-speed, large-range fabrication will lead to large defects in the fabricated structures or devices. In the thesis, firstly, to compensate for the adverse effects generated during high-speed large-range AFM imaging, an integrated approach is proposed, which combines the enhanced inversion-based iterative control technique (EIIC) for lateral x-y axis scanning with a dual-stage piezoactuator for the vertical z-axis positioning. The main contribution of this integrated approach is the combination of an advanced control algorithm with an advanced hardware platform. This approach is demonstrated in experiments by imaging a large-size (50 μm) calibration sample at high speed (50 Hz scan rate). Then secondly, to achieve high-speed large-range multi-axis AFM nanofabrication, a recently developed model-less inversion-based iterative control technique (MIIC) is utilized to overcome the adverse effects involved in high-speed large-range multi-axis AFM nanofabrication. By using this advanced control technique,

We have developed a novel confocal microscopy system, which can perform both axial and lateral scanning at an ultra high speed. A rotary mirror array (RMA) consists of 36 small mirrors deployed on the surface of a round plate with a small tilting angle and a discrete rotational symmetry. When the RMA rotates at a constant speed, the focal point is scanned inside a sample periodically and linearly. We have demonstrated a scanning rate of 2400 lines per second, which can be readily improved to more than 20000 lines per second. Our scheme can also be used in a fast scanning multi-photon microscope.

Purpose: To determine the magnitude of error introduced into treatment delivery due to timing effects between respiratory‐gated delivery and dynamic beam delivery (enhanced dynamic wedge (EDW) and step‐and‐shoot intensity modulated radiation therapy (IMRT)). Method and Materials: EDW and IMRT fields were delivered on a linear accelerator (Trilogy, Varian Medical Systems). Gating of the beam was achieved using a commercial respiratory monitoring system (RPM, Varian Medical Systems), and respiratory motion was simulated using a commercial respiratory motion phantom (RPM phantom, Varian Medical Systems). All fields were delivered with no gating, a 1‐mm gating window, and a 2‐mm gating window.Film and ion chamber measurements were made for both EDW and IMRT fields in a water‐equivalent IMRT QA phantom, which was stationary during all measurements. Film measurements used EDR‐2 film, while ion chamber measurements were made with a 0.04 cc volume pin‐point chamber. Leakage current was subtracted from the ion chamber readings.Wedged fields of 15 and 60 degrees were delivered at a dose rate of 600 MU/min. Results were evaluated for the full IMRT plan and for one of the individual beams, at dose rates of 400 and 600 MU/min. Results: All ion chamber measurements were analyzed as percent difference between the gated (1‐mm or 2‐mm gating window) and non‐gated delivery. All differences were less than 1%. There were no significant differences between 1‐mm and 2‐mm gated delivery. Film results, as analyzed from isodose curves and the gamma metric, showed no substantial differences between gated and non‐gated beam delivery. Conclusion: The use of gated treatment delivery of EDW and step‐and‐shoot IMRT fields does not introduce clinically significant differences into the resulting dose distributions, as quantified by film and ion chamber measurements.

Conical three-electrode d.c. plasma for spectrochemical analysis

Lateral and axial resolution and effective depth scanning range in white Light Confocal Microscope are related to the range of longitudinal chromatic aberration of system. In this article simulation and fabrication of white Light Confocal Microscope with tunable longitudinal chromatic aberration is discussed. The simulation has been done by Zemax optical design software. Generation of longitudinal chromatic aberration has been achieved by using two biconvex lenses with focal length of 30 mm and 40 mm and a 40x microscope objective. The effect of variation of distance between lenses on longitudinal chromatic aberration was studied. In addition the optical properties of microscope such as axial and lateral resolution, numerical aperture, effective depth scanning range and total shift of chromatic aberration in optical axis direction were studied. Using this setup with a broadband source of 480nm to 650nm tunable effective depth scanning range covering 23μm to 68μm was achieved. As a result tunable axial resolution of 48nm to 159nm was obtained. Regarding the scale of the sample we could use the optimum resolution.

Over the past few decades, significant efforts have been made to enhance the imaging speed of optical coherence tomography (OCT) [1]. Notably, the photonic time-stretch (PTS) approach, which leverages chromatic dispersion to transform the time-consuming spectral measurement into high-speed temporal waveform acquisition using a single-pixel photodetector, has achieved megahertz-scale axial scan rates, matching the laser repetition rate [2]. Furthermore, advancements in signal processing techniques have addressed the challenges of managing the large data volumes generated by these high-speed systems [3]. However, lateral scanning still relies on mechanical methods or acousto-optical techniques, which constrain the overall imaging throughput [4].

BackgroundThe measurement of computed tomography dose index 100 (CTDI100), which is feasible only through axial scanning, requires that the clinical spiral protocols be replaced with those for axial scanning. The real‐time ionization chamber detects the integral of radiation dose rate profile, enabling the direct verification of the volume CTDI on spiral CT scanning (CTDIvolSpiral).PurposeThis study aimed to develop a direct measurement technique for CTDIvolSpiral and compare its accuracy with that measured using axial scanning (CTDIvolAxial) or that displayed on the console (CTDIvolDisplayed).MethodsA CTDI phantom with a real‐time ionization chamber was placed on the headrest or examination table. CTDI100Axial was measured with following parameters: tube voltage = 120 kV, effective mAs = 100, and rotation time = 1.00 s. The parameters for measuring CTDI100Spiral were set identical to those used for axial scanning, except for rotation times = 0.33, 0.50, and 1.00, pitch = 0.35, 0.50, 0.75, 1.00, 1.25, and 1.50, and the scanning range = 15 cm. CTDI100Spiral was extracted from the integral of radiation dose rate profile. CTDIvolSpiral was subsequently calculated and compared with CTDIvolAxial and CTDIvolDisplayed. Finally, CTDIvolSpiral was measured for 10 clinical protocols and compared with CTDIvolDisplayed.ResultsThe differences between CTDIvolAxial and CTDIvolDisplayed, CTDIvolSpiral and CTDIvolDisplayed, and CTDIvolAxial and CTDIvolSpiral for the head and body phantoms were all < −2.0%. The differences between CTDIvolDisplayed and CTDIvolSpiral for scans on clinical protocols with and without automatic exposure control were < 11.9% and < 10.5%, respectively; these large differences were observed in the dual‐energy twin‐beam protocol. Excluding this protocol yielded differences between the measurements with and without automatic exposure control of < 2.0% and < −3.9%, respectively.ConclusionsThe results showed an excellent agreement between CTDIvolAxial and CTDIvolSpiral, supporting the use of the clinical spiral CT scanning to verify CTDIvolDisplayed using a real‐time ionization chamber.

We demonstrate a remotely located microelectromechanical systems (MEMS) actuator that can translate >400 μm to perform axial beam scanning in a multiphoton microscope. We use a 2-dimensional MEMS mirror for lateral scanning, and collected multiphoton excited fluorescence images in either the horizontal or vertical plane with a field-of-view of either 270 × 270 or 270 × 200 μm2, respectively, at 5 frames per second. Axial resolution varied from 4.5 to 7 μm over the scan range. The compact size of the actuator and scanner allows for use in an endomicroscope to collect images in the vertical plane with >200 μm depth.

We describe a high-speed Fourier domain optical coherence tomography (OCT) using optical de-multiplexers for spectral dispersion of interferograms. The optical de-multiplexer enables to separate 256 narrow spectral bands from a broadband incident light in 25.0 GHz frequency interval centered at 192.2 THz (1559.8 nm) and allows simultaneous detection of all the bands at the speed of DAQ. Using the optical de-multiplexers into a Fourier domain OCT system as spectral analyzers, OCT imaging of 60,000,000 axial scans per second has been achieved. Using a resonant scanner for lateral scan, 16 kHz frame rate, 1400 A-lines per frame, 3 mm depth range, 23 micron meter resolution OCT imaging has been demonstrated.

We present a three-dimensional (3-D) endoscopic optical coherence tomography (OCT) system based on a dual axis microelectromechanical system (MEMS) mirror. The diameter of MEMS mirror was 1.2 mm and both axes were capable of scanning up to 20° (optical) at greater than 1 kHz with excellent linearity. The MEMS mirror was packaged in a machined acrylic endoscopic housing which provided mechanical protection and electrical interconnects as well as optical alignment of the MEMS device to a focusing GRIN lens. The endoscopic MEMS probe was integrated and tested with both a fiber-based time domain (TD) OCT system and Fourier domain (FD) OCT system. Combining the 2-axis lateral scanning of the MEMS device with an axial scan allowed 3-D volume images to be obtained at a rate of 3 frames/s for the TD system and 7 frames/s for the FD system. In the initial investigations, in vivo 3-D OCT images of a human finger as well as images of animal tissue such as healthy rabbit trachea, normal and cancerous regions of hamster cheek pouch tissue were obtained. These images allowed real-time diagnosis of diseased tissue and also clearly delineated important features and tissue structures.

Here we achieved record-high &gt;500 volumes/second two-photon imaging by improving lateral and axial scanning speed via 32-channel multifocal excitation/detection, and a tunable acoustic gradient-index lens, respectively. We developed a deconvolution process to reduce scattering-induced crosstalk in multifocal detection scheme, thus enabling whole brain imaging of Drosophila with millisecond and micrometer spatiotemporal resolution. Potential applications toward brain science include studying millisecond dynamics in a neuronal network, and resolving 3D microfluidics in blood vessels.

In recent years, there have been several advances in the development of high-speed atomic force microscopes (HSAFMs) to obtain images with nanometre vertical and lateral resolution at frame rates in excess of 1 fps. To date, these instruments are lacking in metrology for their lateral scan axes; however, by imaging a series of two-dimensional lateral calibration standards, it has been possible to obtain information about the errors associated with these HSAFM scan axes. Results from initial measurements are presented in this paper and show that the scan speed needs to be taken into account when performing a calibration as it can lead to positioning errors of up to 3%.