Raster Scanning Method Research Articles

Efficient boundary-guided scanning for high-resolution X-ray ptychography.

In the realm of X-ray ptychography experiments, a considerable amount of ptychography scans are typically performed within a field of view encompassing the target sample. While it is crucial to obtain overlapping scans in small increments over the region of interest for achieving high-resolution sample reconstruction, a significant number of these scans often redundantly measure the empty background within the wide field of view. To address this inefficiency, an innovative algorithm is proposed that introduces automatic guidance for data acquisition. The algorithm first directs the scan point to actively search for the object of interest within the field of view. Subsequently, it intelligently scans along the perimeter of the sample, strategically acquiring measurements exclusively within the boundary of the region of interest. By employing this approach, a reduction in the number of measurements required to obtain high-resolution reconstruction images is demonstrated, as compared with conventional raster scanning methods. Furthermore, the automatic guidance provided by the algorithm offers the added advantage of saving valuable time during the reconstruction process. Through practical implementation on real experiments, these findings showcase the efficacy of the proposed algorithm in enhancing the efficiency and accuracy of X-ray ptychography experiments. This novel approach holds immense potential for advancing sample analysis and imaging techniques in various scientific disciplines.

Beam delivery characteristics of the Hitachi carbon ion scanning system at Osaka Heavy Ion Medical Accelerator in Kansai (HIMAK).

Using the pencil beam raster scanning method employed at most carbon beam treatment facilities, spots can be moved without interrupting the beam, allowing for the delivery of a dose between spots (move dose). This technique is also known as Dose-Driven-Continuous-Scanning (DDCS). To minimize its impact on HIMAK patient dosimetry, there's an upper limit to the move dose. Spots within a layer are grouped into sets, or "break points," allowing continuous irradiation. The beam is turned off when transitioning between sets or at the end of a treatment layer or spill. The control system beam-off is accomplished by turning off the RF Knockout (RFKO) extraction and after a brief delay the High Speed Steering Magnet (HSST) redirects the beam transport away from isocenter to a beam dump. The influence of the move dose and beam on/off control on the dose distribution and irradiation time was evaluated by measurements never before reported and modelled for Hitachi Carbon DDCS. We conducted fixed-point and scanning irradiation experiments at three different energies, both with and without breakpoints. For fixed-point irradiation, we utilized a 2D array detector and an oscilloscope to measure beam intensity over time. The oscilloscope data enabled us to confirm beam-off and beam-on timing due to breakpoints, as well as the relative timing of the RFKO signal, HSST signal, and dose monitor (DM) signals. From these measurements, we analyzed and modelled the temporal characteristics of the beam intensity. We also developed a model for the spot shape and amplitude at isocenter occurring after the beam-off signal which we called flap dose and its dependence on beam intensity. In the case of scanning irradiation, we measured move doses using the 2D array detector and compared these measurements with our model. We observed that the most dominant time variation of the beam intensity was at 1 kHz and its harmonic frequencies. Our findings revealed that the derived beam intensity cannot reach the preset beam intensity when each spot belongs to different breakpoints. The beam-off time due to breakpoints was approximately 100 ms, while the beam rise time and fall time (tdecay ) were remarkably fast, about 10 ms and 0.2 ms, respectively. Moreover, we measured the time lag (tdelay ) of approximately 0.2 ms between the RFKO and HSST signals. Since tdelay ≈ tdecay at HIMAK then the HSST is activated after the residual beam intensity, resulting in essentially zero flap dose at isocenter from the HSST. Our measurements of the move dose demonstrated excellent agreement with the modelled move dose. We conducted the first move dose measurement for a Hitachi Carbon synchrotron, and our findings, considering beam on/off control details, indicate that Hitachi's carbon synchrotron provides a stable beam at HIMAK. Our work suggests that measuring both move dose and flap dose should be part of the commissioning process and possibly using our model in the Treatment Planning System (TPS) for new facilities with treatment delivery control systems with higher beam intensities and faster beam-off control.

Non-line-of-sight imaging based on Archimedean spiral scanning

Non-line-of-sight imaging can reconstruct objects hidden out of sight, which has drawn great attention in recent years. However, long data acquisition time is required since most of transient non-line-of-sight imaging need multi-point raster scanning of the visible wall. Here, we propose an Archimedean spiral scanning method based on confocal non-line-of-sight imaging, which greatly reduces the data acquisition time. Fewer scanning points are sufficient for imaging owing to accurate extraction of effective information. The Archimedean spiral scanning method is experimentally verified with published data and real scenes, then the curvature regularization algorithm is used to process data to achieve higher quality imaging. In the case of guaranteeing the imaging quality, the number of scanning points is reduced by an order of magnitude with the proposed method compared to traditional multi-point raster scanning method in this experiment. As a comparison, the imaging quality of Archimedean spiral scanning method is higher than those of the circular and confocal non-line-of-sight scanning methods at the same number of scanning points. This scanning method is expected to have a certain remarkable effect for real-time NLOS imaging.

FastGeodis: Fast Generalised Geodesic Distance Transform

The FastGeodis package provides an efficient implementation for computing Geodesic and Euclidean distance transforms (or a mixture of both), targeting efficient utilisation of CPU and GPU hardware. In particular, it implements the paralellisable raster scan method from Criminisi et al. (2009), where elements in a row (2D) or plane (3D) can be computed with parallel threads. This package is able to handle 2D as well as 3D data, where it achieves up to a 20x speedup on a CPU and up to a 74x speedup on a GPU as compared to an existing open-source library (Wang, 2020) that uses a non-parallelisable single-thread CPU implementation. The performance speedups reported here were evaluated using 3D volume data on an Nvidia GeForce Titan X (12 GB) with a 6-Core Intel Xeon E5-1650 CPU. Further in-depth comparison of performance improvements are discussed in the FastGeodis documentation: https://fastgeodis.readthedocs.io

Proton and carbon ion beam treatment with active raster scanning method in 147 patients with skull base chordoma at the Heidelberg Ion Beam Therapy Center—a single-center experience

BackgroundThis study aimed to compare the results of irradiation with protons versus irradiation with carbon ions in a raster scan technique in patients with skull base chordomas and to identify risk factors that may compromise treatment results.MethodsA total of 147 patients (85 men, 62 women) were irradiated with carbon ions (111 patients) or protons (36 patients) with a median dose of 66 Gy (RBE (Relative biological effectiveness); carbon ions) in 4 weeks or 74 Gy (RBE; protons) in 7 weeks at the Heidelberg Ion Beam Therapy Center (HIT) in Heidelberg, Germany. The median follow-up time was 49.3 months. All patients had gross residual disease at the beginning of RT. Compression of the brainstem was present in 38%, contact without compression in 18%, and no contact but less than 3 mm distance in 16%. Local control and overall survival were evaluated using the Kaplan–Meier Method based on scheduled treatment (protons vs. carbon ions) and compared via the log rank test. Subgroup analyses were performed to identify possible prognostic factors.ResultsDuring the follow-up, 41 patients (27.9%) developed a local recurrence. The median follow-up time was 49.3 months (95% CI: 40.8–53.8; reverse Kaplan–Meier median follow-up time 56.3 months, 95% CI: 51.9–60.7). No significant differences between protons and carbon ions were observed regarding LC, OS, or overall toxicity. The 1‑year, 3‑year, and 5‑year LC rates were 97%, 80%, and 61% (protons) and 96%, 80%, and 65% (carbon ions), respectively. The corresponding OS rates were 100%, 92%, and 92% (protons) and 99%, 91%, and 83% (carbon ions). No significant prognostic factors for LC or OS could be determined regarding the whole cohort; however, a significantly improved LC could be observed if the tumor was > 3 mm distant from the brainstem in patients presenting in a primary situation.ConclusionOutcomes of proton and carbon ion treatment of skull base chordomas seem similar regarding tumor control, survival, and toxicity. Close proximity to the brainstem might be a negative prognostic factor, at least in patients presenting in a primary situation.

Shortening the delivery time of proton therapy by real-time compensation method with raster scanning

Among the various scanning techniques, spot and raster scanning are the most frequently adopted. Raster scanning turns off the beam only when each isoenergy slice irradiation is completed. This feature intrinsically solves the leakage dose and frequent beam-switching problems encountered during spot scanning. However, to shorten the delivery time of raster scanning, a sophisticated dose control strategy is required to guarantee dose distribution. In this study, a real-time compensation method with raster scanning for synchrotron systems was designed. It is characterized by a small spot-spacing planning strategy and real-time subtraction of the transient number of particles delivered between two planning-spot positions from the planned number of particles of the subsequent raster point. The efficacy of the compensation method was demonstrated by performing accurate raster scanning simulations with an in-house simulation code and accurate final dose evaluations with a commercial treatment planning system. Given the similar dose evaluation criteria under a practical high scanning speed, compared with the spot scanning method, the total delivery time of the compensated raster scanning method was significantly shortened by 53.3% in the case of irradiating a cubical target and by 28.8% in a pelvic case. Therefore, it can be concluded that real-time compensated raster scanning with a fast scanning configuration can significantly shorten the delivery time compared to that of spot scanning. It is important to reduce the pressure on patients caused by prolonged immobilization and to improve patient throughput capacity at particle therapy centers.

Evaluation of Safety for Scanning Carbon-Ion Radiotherapy in Hemodialysis Patients With Prostate Cancer.

Background/AimThe efficacy and safety of carbon-ion radiotherapy (CIRT) for prostate cancer have already been demonstrated. The number of hemodialysis (HD) patients is increasing. Although the toxicity of CIRT in HD patients may be more severe, it has been insufficiently investigated. Therefore, we retrospectively analyzed the safety of CIRT for HD patients with prostate cancer in the present study.Materials and methodsFive HD patients with prostate cancer who underwent CIRT at the Kanagawa Cancer Center during November 2015-2020 were included in this study. CIRT was delivered by the raster scanning method (sCIRT). Adverse events were assessed using the Common Terminology Criteria for Adverse Events version 5.0. The dose-volume histogram (DVH) parameters of the target volume and normal organs were evaluated between initial planning computed tomography (CT) and in-room CT images.ResultsIn the acute phase, Grade 1 genitourinary toxicity was recorded in one patient. In the late phase, Grade 1 genitourinary toxicity was recorded in two patients. No gastrointestinal toxicities were noted during the follow-up period. In-room CT analysis revealed no significant differences among all DVH parameters of the target volume and normal organs when compared with the treatment plan dose.ConclusionsThe safety of sCIRT for prostate cancer in HD patients was investigated in the present study. In-room CT analysis suggested the robustness of the treatment plan. According to the present results, sCIRT for prostate cancer can be safely performed in HD patients.

Optimized Chaotic encrypted image based on continuous raster scan method

As the greatest effective method of protection of multimedia data is image encryption is extensively used in data hiding, security authentication and content protection. Nevertheless, the security and efficiency are still the key issues of image encryption algorithm. However, the existing image encryption techniques face the issues namely poor resistance to plaintext attacks, simple algorithmic structures and small key space. In order to overcome the problem of traditional techniques, a joint image encryption techniques of continuous raster Scan, Henon Chaotic Map and Chebyshev Chaotic Map are developed for providing a security of images. Initially, the continuous raster is used to scramble the pixels of each blocks, where images are partitioning an image into non overlapping blocks and starting point is randomly selected in Henon Chaotic Map to permute the block. To calculate a random matrix, Chebyshev Chaotic Map is used to generate the sequence based on the secret keys. Finally, bitwise XOR operation between the scrambled image and random matrix is conducted to obtain the encrypted image. The proposed method takes very less time for encryption. Simulation results show that the algorithm is efficient and usable for the security of the image encryption system.

A Study on the Large-Area Image Acquisition Using Stage Transfer Synchronization Method in a Low-Energy Microcolumn System

We studied the stage transfer synchronization method to improve the low throughput which is the biggest drawback of the raster scan method when applied to image acquisition in a low energy microcolumn system. Through preliminary experiments, we were able to acquire some sample images and some images of the measured samples by applying the synchronization method to a conventional single-microcolumn system. The image acquired in this preliminary experiment was three times larger than that acquired by the raster scan method in the vertical direction. In this study, we tested two types of the synchronization method: the first method acquires an image by horizontal electron beam scanning followed by a vertical stage transfer, and the second one acquires an image by vertical electron beam scanning followed by a horizontal stage transfer. By applying the vertical stage transfer synchronization method, we could acquire a larger image than that acquired by the conventional raster scan method. The vertical stage transfer synchronization method image was 1.8 times larger in the horizontal direction and 6 times larger in the vertical direction. In addition, a larger image approximately nine times in the horizontal direction and five times in the vertical direction was acquired by applying the horizontal stage transfer synchronization method.

Vector scanning subtractive manufacturing technology for laser rapid fabrication.

Herein, a vector scanning subtractive manufacturing technology is proposed to rapidly fabricate smooth micro-optical components, which is based on the vector scanning method and wet etching. Compared with the raster scanning method, the vector scanning method increases processing efficiency by nearly two orders and mitigates a buildup of stress around the laser processed region, avoiding the generation of cracks. The Letter demonstrates the fabrication of three-dimensional (3D) micro-structures with various sizes and morphologies. For example, micro-concave lenses with diameters of 20 µm to 140 µm, heights of 10 µm to 70 µm, and surface roughness of 29 nm are flexibly fabricated on sapphire by vector scanning subtractive manufacturing technology. The results indicate that the technology has broad prospects in the field of monolithic integrated 3D all-solid-state micro-optics.

Determining the suitable CO2 laser based technique for microchannel fabrication on PMMA

CO2 lasers are commonly used in fabricating microchannels on Polymethyl methacrylate (PMMA) substrate. Due to significant lower cost and smaller fabrication time, several microfluidic device manufacturers are already using CO2 laser based processing instead of conventional & time consuming lithographic methods. At least three broadly different strategies can be employed to fabricate microchannels with most of the commercially available low power CO2 lasers i.e. focused cutting, defocused cutting and raster scanning method. These three approaches have been studied in this work as three different fabricating strategies. Further, focused processing method can be employed in two different ways namely single-pass processing and multi-pass processing with their own set of advantages and disadvantages. Similarly, raster scanning method can also be used with a mask as well as without applying mask. Experimental studies have been conducted by fabricating different dimensions of microchannels using these different techniques. Surface quality, cross-sectional profile, microchannel width and heat affected zone have been chosen as parameters for comparing these techniques. Each of these strategies has been discussed in detail. Corresponding analytical models have been outlined for each of these processes. While the single-pass strategy was found to be consuming minimum time, raster scanning method accompanied with masks was observed to be producing microchannel walls with rectangular cross-sections.

Three dimensional microspectroscopic tomography with synchrotron radiation infrared raster scanning method

A microspectroscopic tomography method is performed for a nondestructive three dimentional (3D) imaging. The synchrotron radiation infrared (SRIR) is used as a light source. A MiTeGen loop and a bird feather barb are taken as check samples. Their IR spectral informations are collected by raster scanning procedure with the incompleted projection mappings. Their 3D tomographic reconstructions are obtained by the penalized maximum likelihood algorithm with weighted linear and quadratic penalties (PML-Hybrid algorithm). The computed algorithm reconstructs the MiTeGen loop in the 1638–1572 cm−1 region, which corresponds to the NH bend vibration. Besides, the bird feather barb is measured in the mid-infrared spectral region, and the main characteristic absorption bands include amide A, the lipids, and amide I. Their 3D reconstruction images are obtained from three selected absorption bands. The results show that the 3D tomographic method presents a good signal-to-noise ratio (SNR). The 3D distributions of chemical compositions are obtained for the MiTeGen loop and the bird feather barb by SRIR microspectroscopic tomography.

Development of raster scanning IMRT using a robotic radiosurgery system.

Treatment time with the CyberKnife frameless radiosurgery system is prolonged due to the motion of the robotic arm. We have developed a novel scanning irradiation method to reduce treatment time. We generated treatment plans mimicking eight-field intensity-modulated radiotherapy (IMRT) plans generated for the Novalis radiosurgery system. 2D dose planes were generated with multiple static beam spots collimated by a fixed circular cone. The weights of the uniformly distributed beam spots in each dose plane were optimized using the attraction–repulsion model. The beam spots were converted to the scanning speed to generate the raster scanning plan. To shorten treatment time, we also developed a hybrid scanning method which combines static beams with larger cone sizes and the raster scanning method. Differences between the Novalis and the scanning plan’s dose planes were evaluated with the criterion of a 5% dose difference. The mean passing rates of three cases were > 85% for cone sizes ≤ 12.5 mm. Although the total monitor units (MU) increased for smaller cone sizes in an inverse-square manner, the hybrid scanning method greatly reduced the total MU, while maintaining dose distributions comparable to those with the Novalis plan. The estimated treatment time of the hybrid scanning with a 12.5 mm cone size was on average 22% shorter than that of the sequential plans. This technique will be useful in allowing the CyberKnife with conventional circular cones to achieve excellent dose distribution with a shortened treatment time.

New results from the DANSS experiment

We present new results of the DANSS experiment on the searches for sterile neutrinos. They are based on more than 2 million of inverse beta decay events collected at 10.7 m, 11.7 m and 12.7 m from the reactor core of the 3.1 GW Kalinin Nuclear Power Plant in Russia. This data sample is 2.4 times larger than the data sample in the previous DANSS publication. The search for the sterile neutrinos is performed using the ratio of [Formula: see text] spectra at two distances. This method is very robust against systematic uncertainties in the [Formula: see text] spectrum and the detector efficiency. We do not see any statistically significant sign for the [Formula: see text] oscillations. This allows us to exclude further a large and interesting part of the sterile neutrino parameter space. A Gaussian CL[Formula: see text] method was used to obtain exclusion areas. This method is more conservative than a Raster Scan method.

Decentralized Multi-agent information-theoretic control for target estimation and localization: finding gas leaks

This article presents a new decentralized multi-agent information-theoretic (DeMAIT) control algorithm for mobile sensors (agents). The algorithm leverages Bayesian estimation and information-theoretic motion planning for efficient and effective estimation and localization of a target, such as a chemical gas leak. The algorithm consists of: (1) a non-parametric Bayesian estimator, (2) an information-theoretic trajectory planner that generates “informative trajectories” for agents to follow, and (3) a controller and collision avoidance algorithm to ensure that each agent follows its trajectory as closely as possible in a safe manner. Advances include the use of a new information-gain metric and its analytical gradient, which do not depend on an infinite series like prior information metrics. Dynamic programming and multi-threading techniques are applied to efficiently compute the mutual information to minimize measurement uncertainty. The estimation and motion planning processes also take into account the dynamics of the sensors and agents. Extensive simulations are conducted to compare the performance between the DeMAIT algorithm to a traditional raster-scanning method and a clustering method with coordination. The main hypothesis that the DeMAIT algorithm outperforms the other two methods is validated, specifically where the average localization success rate for the DeMAIT algorithm is (a) higher and (b) more robust to changes in the source location, robot team size, and search area size than the raster-scanning and clustering methods. Finally, outdoor field experiments are conducted using a team of custom-built aerial robots equipped with gas concentration sensors to demonstrate efficacy of the DeMAIT algorithm to estimate and find the source of a propane gas leak.

Hyperspectral terahertz imaging with electro-optic dual combs and a FET-based detector

In this paper, a terahertz hyperspectral imaging architecture based on an electro-optic terahertz dual-comb source is presented and demonstrated. In contrast to single frequency sources, this multi-heterodyne system allows for the characterization of the whole spectral response of the sample in parallel for all the frequency points along the spectral range of the system. This hence provides rapid, highly consistent results and minimizes measurement artifacts. The terahertz illumination signal can be tailored (in spectral coverage and resolution) with high flexibility to meet the requirements of any particular application or experimental scenario while maximizing the signal-to-noise ratio of the measurement. Besides this, the system provides absolute frequency accuracy and a very high coherence that allows for direct signal detection without inter-comb synchronization mechanisms, adaptive acquisition, or post-processing. Using a field-effect transistor-based terahertz resonant 300 GHz detector and the raster-scanning method we demonstrate the two-dimensional hyperspectral imaging of samples of different kinds to illustrate the remarkable capabilities of this innovative architecture. A proof-of-concept demonstration has been performed in which tree leaves and a complex plastic fragment have been analyzed in the 300 GHz range with a frequency resolution of 10 GHz.

Femtosecond Laser-Induced Damage Characterization of Multilayer Dielectric Coatings

The laser-induced damage threshold (LIDT) of optical components is one of the major constraints in developing high-power ultrafast laser systems. Multi-layer dielectric (MLD) coatings-based optical components are key parts of high-power laser systems because of their high damage resistance. Therefore, understanding and characterizing the laser-induced damage of MLD coatings are of paramount importance for developing ultrahigh-intensity laser systems. In this article, we overview the possible femtosecond laser damage mechanisms through damage morphologies in various MLD optical coatings tested in our facility. To evaluate the major contributions to the coating failure, different LIDT test methods (R-on-1, ISO S-on-1 and Raster Scan) were carried out for a high reflective hybrid Ta2O5/HfO2/SiO2 MLD mirror coating at a pulse duration of 37 fs. Different LIDT test methods were compared due to the fact that each test method exposes the different underlying damage mechanisms. For instance, the ISO S-on-1 test at a higher number of laser pulses can bring out the fatigue effects, whereas the Raster Scan method can reveal the non-uniform defect clusters in the optical coating. The measured LIDT values on the sample surface for the tested coating in three test methods are 1.1 J/cm2 (R-on-1), 0.9 J/cm2 (100k-on-1) and 0.6 J/cm2 (Raster Scan) at an angle of incidence of 45 deg. The presented results reveal that the performance of the tested sample is limited by coating defects rather than fatigue effects. Hence, the Raster Scan method is found to be most accurate for the tested coating in evaluating the damage threshold for practical applications. Importantly, this study demonstrates that the testing of different LIDT test protocols is necessary in femtosecond regime to assess the key mechanisms to the coating failure.

A diamond guard ring microdosimeter for ion beam therapy.

A single crystal chemical vapor deposition diamond-based microdosimeter prototype featuring an array of micro-sensitive volumes (μSVs) and surrounded by a so-called guard ring (GR) electrode has been fabricated using various microfabrication techniques available at Diamond Sensors Laboratory of CEA, Saclay. The GR microdosimeter was irradiated by a raster scanning method with 2 MeV proton microbeams. The charge transport properties of the GR sensor were determined with sub-micron spatial resolution by measuring the charge collection efficiency (CCE), the μSV geometry, and the pulse-height spectra. The response of the microdosimeter showed a well-defined and homogeneously active μSV. Appropriate biasing of the μSV structures led toward a full CCE for protons with lineal energies of ∼46 keV/μm. This shows the GR microdosimeter's great potential for applications in microdosimetry in clinical beam conditions.

Iso-material contour representation for process planning of heterogeneous object model

Abstract Additive manufacturing is emerging as the preferred process for making heterogeneous objects. Planning the deposition of material is more complex for heterogeneous objects as the material variation has to be tracked along the path. This paper proposes an iso-material contour representation to generate the process plan for additive manufacturing given a smooth representation of heterogeneous object model. These contours represent the iso-material paths for deposition. As these paths shift along the direction of the gradation of material distribution, the deposition respects the gradient of the designed material distribution unlike iso-oriented paths generated by a raster scan method. Since the paths have the same material composition, material frequent change in the material composition is avoided, which, in turn, avoids the uneven deposition caused by the frequent start and stop of deposition while the material is being changed along the paths generated by the traditional raster scan. Associativity between the contours and the corresponding designed material feature is maintained, and therefore, changes in material composition are automatically propagated to the process plan.

A high-speed atomic force microscopy with super resolution based on path planning scanning

An atomic force microscopy generally adopts a raster scanning method to obtain the image of the sample morphology. However, the raster method takes too much time on the base part without focusing enough on the object, thereby restricting the scanning speed of an AFM. To solve this problem, this paper proposes a novel path planning based scanning method to achieve high-speed scanning with super resolution for AFMs. Specifically speaking, a fast scanning process is first carried out to generate a low-resolution image with less time, then a convolutional neural network is designed to construct a super-resolution image based on the fast scanning image. Afterwards, an advanced detection algorithm is proposed to achieve the accurate object detection and localization. Furthermore, an improved ant colony optimization algorithm is proposed to realize the path planning for scanning the objects with high quality, whose imaging result is then matched with the previous super-resolution image to construct the entire sample image, thus achieving fast scanning with super resolution. Experimental and application results demonstrate the good performance of the proposed scanning method.