An onboard time acquisition method for spacecraft

Quantification of Artifact Reduction With Real-Time Cine Four-Dimensional Computed Tomography Acquisition Methods

PurposeA three-dimensional (3D) printed custom-fit respirator mask has been proposed as a promising solution to alleviate mask-related injuries and supply shortages during COVID-19. However, creating a custom-fit computer-aided design (CAD) model for each mask is currently a manual process and thereby not scalable for a pandemic crisis. This paper aims to develop a novel design process to reduce overall design cost and time, thus enabling the mass customisation of 3D printed respirator masks.Design/methodology/approachFour data acquisition methods were used to collect 3D facial data from five volunteers. Geometric accuracy, equipment cost and acquisition time of each method were evaluated to identify the most suitable acquisition method for a pandemic crisis. Subsequently, a novel three-step design process was developed and scripted to generate respirator mask CAD models for each volunteer. Computational time was evaluated and geometric accuracy of the masks was evaluated via one-sided Hausdorff distance.FindingsRespirator masks were successfully generated from all meshes, taking <2 min/mask for meshes of 50,000∼100,000 vertices and <4 min for meshes of ∼500,000 vertices. The average geometric accuracy of the mask ranged from 0.3 mm to 1.35 mm, depending on the acquisition method. The average geometric accuracy of mesh obtained from different acquisition methods ranged from 0.56 mm to 1.35 mm. A smartphone with a depth sensor was found to be the most appropriate acquisition method.Originality/valueA novel and scalable mass customisation design process was presented, which can automatically generate CAD models of custom-fit respirator masks in a few minutes from a raw 3D facial mesh. Four acquisition methods, including the use of a statistical shape model, a smartphone with a depth sensor, a light stage and a structured light scanner were compared; one method was recommended for use in a pandemic crisis considering equipment cost, acquisition time and geometric accuracy.

To develop, test and evaluate improved 2D and 3D protocols for proton resonance frequency shift magnetic resonance temperature imaging (MRTI) of laser interstitial thermal therapy (LITT). The objective was to develop improved MRTI protocols in terms of temperature measurement precision and volume coverage compared to the 2D MRTI protocol currently used with a commercially available LITT system. Four different 2D protocols and four different 3D protocols were investigated. The 2D protocols used multi-echo readouts to prolong the total MR sampling time and hence the MRTI precision, without prolonging the total acquisition time. The 3D protocols provided volumetric thermometry by acquiring a slab of 12 contiguous slices in the same acquisition time as the 2D protocols. The study only considered readily available pulse sequences (Cartesian 2D and 3D gradient recalled echo and echo planar imaging [EPI]) and methods (partial Fourier and parallel imaging) to ensure wide availability and rapid clinical implementation across vendors and field strengths. In vivo volunteer studies were performed to investigate and compare MRTI precision and image quality. Phantom experiments with LITT heating were performed to investigate and compare MRTI precision and accuracy. Different coil setups were used in the in vivo studies to assess precision differences between using local (such as flex and head coils) and non-local (i.e., body coil) receive coils. Studies were performed at both 1.5 T and 3 T. The improved 2D protocols provide up to a factor of two improvement in the MRTI precision in the same acquisition time, compared to the currently used clinical protocol. The 3D echo planar imaging protocols provide comparable precision as the currently used 2D clinical protocol, but over a substantially larger field of view, without increasing the acquisition time. As expected, local receive coils perform substantially better than the body coil, and 3 T provides better MRTI accuracy and precision than 1.5 T. 3D data can be zero-filled interpolated in all three dimensions (as opposed to just two dimensions for 2D data), reducing partial volume effects and measuring higher maximum temperature rises. With the presented protocols substantially improved MRTI precision (for 2D imaging) or greatly improved field of view coverage (for 3D imaging) can be achieved in the same acquisition time as the currently used protocol. Only widely available pulse sequences and acquisition methods were investigated, which should ensure quick translation to the clinic. Lasers Surg. Med. 51:286-300, 2019. © 2019 Wiley Periodicals, Inc.

This study investigated the spatial resolution and image quality of the continuous bed motion (CBM) method in a sensitive silicon photomultiplier (SiPM)-based positron emission tomography (PET)/computed tomography (CT) system compared with the traditional step-and-shoot (SS) method. Methods: Siemens Biograph Vision was used in this study. Data acquisition using the SS method was performed for 3 min per bed. In the CBM method, the bed speed ranged from 0.5 to 3.3 mm/s. The acquisition time equivalent to the SS method was 1.1 mm/s for 2-bed ranges and 0.8 mm/s for seven-bed ranges. The spatial resolution was investigated using 18F point sources and evaluated using the full width at half maximum. Image quality was investigated using a National Electrical Manufacturers Association International Electrotechnical Commission body phantom with six spheres 10-, 13-, 17-, 22-, 28-, and 37-mm inner diameters. The radioactivity concentration ratio of the 18F solution in all spheres and the background was approximately 4:1. The detectability of each sphere was visually evaluated on a five-step score. Image quality was physically evaluated using the noise equivalent count rate (NECphantom), contrast percentage of the 10-mm hot sphere (QH,10mm), background variability percentage (N10mm), and contrast-noise ratio (QH,10mm/N10mm). Results: The spatial resolution was not affected by the difference of acquisition methods and bed speeds. The detectability of the 10-mm sphere with a bed speed of 2.2 mm/s or faster was significantly inferior to that of the SS 2-bed method. In evaluating image quality, no significant difference in the contrast percentage was observed among the acquisition methods and speeds in the CBM method. However, the increasing bed speed in the CBM method increased the N10mm and decreased the NECphantom. When comparing the SS 2-bed method with the CBM method at 0.8 mm/s, no significant differences in all parameters were observed. Conclusion: In a SiPM-based PET/CT scanner, the CBM method provides equivalent spatial resolution and image quality in whole body PET images with same acquisition time using the SS method.

Development and evaluation of matrix application techniques for high throughput mass spectrometry imaging of tissues in the clinic

Background: 18F-FDG PET is performed in preset time model. Generally, the longer the acquisition time we set, the better the image quality we get. However, a prolonged acquisition time is associated with a decreased patient throughput and an increased risk of motion artifacts. In order to insure an acceptable image quality as well as a decreased acquisition time, we used list mode acquisition and statistic methods to find out an optimal acquisition time. Methods: Thirty 18F-FDG PET positive intra-abdominal lesions were acquired with list mode acquisition. ROIs were selected manually and SUV(subscript max) and SUV(subscript mean) were obtained. The ratios of SUVs in the lesion and background were calculated. We used Pearson's correlation coefficient, Kendall's tau-b correlation, and Spearman rho correlation to find the correlation between the resulted SUV ratios from different acquisition time of 0.5 to 9 min with what from 10 min. Then we used the paired t-test and nonparametric tests to find the optimal acquisition time. Results: As to the ratios of SUV(subscript max) of the lesions and background, there was significant difference in comparing those from acquisition time of 0.5 to 3 min with those from acquisition time of 10 min. If acquisition time was longer than 3 min, there was no significant difference. Conclusion: In 18F-FDG PET studies, acquisition time less than 3 min should be avoided.

This paper presents a new acquisition method achieving reduction of acquisition time by improving the conventional acquisition method using the code‐orthogonalizing filter. In the acquisition method using the code‐orthogonalization filter, most of the acquisition time is spent on the orthogonalization process. Hence, in the proposed method, estimation of synchronous point candidates is performed several times so that the estimation accuracy is improved and the acquisition time is reduced by decreasing the number of orthogonalizations. After the scheme is explained, a performance evaluation of the proposed method is carried out by computer simulation. © 2004 Wiley Periodicals, Inc. Electron Comm Jpn Pt 3, 87(7): 36–44, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecjc.10148

Four dimensional computed tomography (4D CT) has shown to be of value in the diagnosis of motion related wrist joint pathologies. 4D CT can be performed with a variety of acquisition methods. However, the usability of 4D CT is affected by motion and image artifacts associated with the specific acquisition method used. In this literature review we inventorize which acquisition methods exist for 4D-CT imaging at different positions of the human body and what the advantages and disadvantages of each method are. Based on this assessment we formulate recommendations for the 4D CT imaging approach for diagnosing motion related wrist pathologies. We also address future perspectives of image acquisition in 4D CT of the wrist joint. We found that scanning in volumetric mode eliminates irregularity artifacts, while reducing acquisition time per frame reduces blurring artifacts. A reduced acquisition time can be achieved with short gantry rotation times, dual source CT and Reconstruction based on Partial Gantry Rotation (RPGR). However, the effect of RPGR on RPGR-specific artifacts and the effect of different acquisition times on apparent object displacements may be investigated in future research.

A significant number of patients receiving breast-conserving surgery (BCS) for invasive carcinoma and ductal carcinoma in situ (DCIS) may need reoperation following tumor-positive margins from final histopathology tests. All current intraoperative margin assessment modalities have specific limitations. As a first step towards the development of a compact system for intraoperative specimen imaging based on edge illumination x-ray phase contrast, we prove that the system’s dimensions can be reduced without affecting imaging performance.We analysed the variation in noise and contrast to noise ratio (CNR) with decreasing system length using the edge illumination x-ray phase contrast imaging setup. Two-(planar) and three-(computed tomography (CT)) dimensional imaging acquisitions of custom phantoms and a breast tissue specimen were made. Dedicated phase retrieval algorithms were used to separate refraction and absorption signals. A ‘single-shot’ retrieval method was also used, to retrieve thickness map images, due to its simple acquisition procedure and reduced acquisition times. Experimental results were compared to numerical simulations where appropriate.The relative contribution of dark noise signal in integrating detectors is significant for low photon count statistics acquisitions. Under constant exposure factors and magnification, a more compact system provides an increase in CNR. Superior CNR results were obtained for refraction and thickness map images when compared to absorption images. Results indicate that the ‘single-shot’ acquisition method is preferable for a compact CT intraoperative specimen scanner; it allows for shorter acquisition times and its combination of the absorption and refraction signals ultimately leads to a higher contrast. The first CT images of a breast specimen acquired with the compact system provided promising results when compared to those of the longer length system.

There is a trend towards satellite laser communication using advanced laser technology including developing a network based on microsatellite laser communication. But the advantage of small laser beam divergence creates a complex problem for acquisition, pointing and tracking. Microsatellite laser communication networks require research in systems and algorithms for acquisition. The purpose of the acquisition system is to compensate for large pointing errors at the beginning of the process and to achieve the minimal desired errors that will provide the beginning of the tracking and optical communication phase. In this process the requirement is to detect the optical signal with a given probability within a given time. The paper will describe several acquisition methods and compare their probability of acquisition and the acquisition time. These acquisition methods include Stare/Stare Method Scan/Stare Methoth Scan/Scan MethodS Stare/Scan Method. In the process we mainly discuss two kinds of scanning patterns. They are raster scanning and spiral scanning. Furthermore, we will examine influences of satellite vibrations on the acquisition scanning because this is the major difficulty in this process. We will give the integrate stimulation and suggest a correction algorithm.

Accuracy of smartphone-based photogrammetry for full-arch implant position transfer: a controlled in vitro comparison with scan body-based intraoral scanning.

The acquisition time performance of a two-user spread-spectrum multiple-access system is examined. The acquisition is accomplished using conventional (single-user) correlating/energy-detecting acquisition methods. The intent of the analysis is to determine how much performance penalty is incurred because of the presence of the multiple-user interference. The analysis indicates that for good spreading codes the performance degradation is not severe when the user's amplitudes are all similar. However, in the presence of significant near/far power differences, the acquisition time increases dramatically. This suggests the need for acquisition methods which explicitly account for the presence of multiple users. >

The purpose of this study was to compare the proposed rapid NT-MRCP protocol and the conventional NT-MRCP protocol with respect to image quality as well as the acquisition time. Between January 2019 and May 2019, a total number of 67 consecutive patients with suspected pancreaticobiliary diseases were included in this prospective study and underwent 3D rapid MRCP and 3D conventional MRCP sequences. Both acquisition protocols were set from the same navigator-triggered 3D SPACE sequence. The acquisition time was recorded. Two blinded radiologists performed qualitative analyses with respect to overall image quality, motion artifacts, and CBD visibility using a four-point scale. Quantitative evaluation included the contrast, signal-noise ratio (SNR), and contrast-noise ratio (CNR) between the common bile duct (CBD) and periductal tissues. A paired t test was used to assess differences in the qualitative and quantitative evaluations between the two acquisition methods. All MRCP studies were completed successfully. The mean acquisition time of rapid NT-MRCP (96.64 ± 30.55s) was significantly lower than that of the conventional NT-MRCP (271.42 ± 61.63s; p < 0.001).The contrast ratio, SNR, and CNR of the CBD were significantly higher for conventional NT-MRCP than with rapid NT-MRCP images (0.95 ± 0.02 vs. 0.93 ± 0.03, p < 0.001; 10.36 ± 4.63 vs. 8.90 ± 4.71, p = 0.011; 14.01 ± 6.02 vs. 12.22 ± 6.36, p = 0.020, respectively). The rapid MRCP depicted the overall image quality, artifacts, CBD visibility, right and left hepatic duct, segment 2 branch, main pancreatic duct, and cystic duct significantly better compared with conventional MRCP (p < 0.05). There were no statistically significant differences between the two methods regarding visibility of anterior, posterior, and segment 3 branches (p > 0.05). In conclusion, the proposed rapid MRCP protocol yielded significantly higher overall image quality and better visualization of the pancreaticobiliary tree with a significantly reduced imaging time without deterioration of image quality compared with the conventional MRCP at 3T.

Many single-pixel imaging techniques have been developed in recent years. Though the methods of image acquisition vary considerably, the methods share unifying features that make general analysis possible. Furthermore, the methods developed thus far are based on intuitive processes that enable simple and physically-motivated reconstruction algorithms, however, this approach may not leverage the full potential of single-pixel imaging. We present a general theoretical framework of single-pixel imaging based on frame theory, which enables general, mathematically rigorous analysis. We apply our theoretical framework to existing single-pixel imaging techniques, as well as provide a foundation for developing more-advanced methods of image acquisition and reconstruction. The proposed frame theoretic framework for single-pixel imaging results in improved noise robustness, decrease in acquisition time, and can take advantage of special properties of the specimen under study. By building on this framework, new methods of imaging with a single element detector can be developed to realize the full potential associated with single-pixel imaging.

The essentially infinite storage space offered by Cloud Computing is quickly becoming a problem for forensics investigators in regards to evidence acquisition, forensic imaging and extended time for data analysis. It is apparent that the amount of stored data will at some point become impossible to practically image for the forensic investigators to complete a full investigation. In this paper, we address these issues by determining the relationship between acquisition times on the different storage capacities, using remote acquisition to obtain data from virtual machines in the cloud. A hypothetical case study is used to investigate the importance of using a partial and full approach for acquisition of data from the cloud and to determine how each approach affects the duration and accuracy of the forensics investigation and outcome. Our results indicate that the relation between the time taken for image acquisition and different storage volumes is not linear, owing to several factors affecting remote acquisition, especially over the Internet. Performing the acquisition using cloud resources showed a considerable reduction in time when compared to the conventional imaging method. For a 30GB storage volume, the least time was recorded for the snapshot functionality of the cloud and dd command. The time using this method is reduced by almost 77 percent. FTK Remote Agent proved to be most efficient showing an almost 12 percent reduction in time over other methods of acquisition. Furthermore, the timelines produced with the help of the case study, showed that the hybrid approach should be preferred to complete approach for performing acquisition from the cloud, especially in time critical scenarios.