Direct Fan‐Beam Reconstruction Algorithm via Filtered Backprojection for Differential Phase‐Contrast Computed Tomography

The differential phase contrast CT is emerging as a new technology to improve the contrast sensitivity of the conventional CT. Via system analysis, modeling, and computer simulation, the authors study the noise power spectrum (NPS)--an imaging performance indicator-of the differential phase contrast CT and compare it with that of the conventional CT. The differential phase contrast CT is implemented with x-ray tube and gratings. The x-ray propagation and data acquisition are modeled and simulated with Fourier analysis and Fresnel analysis. To avoid any interference caused by scatter and beam hardening, a monochromatic x-ray source (30 keV) is assumed, which irradiates the object to be imaged by 360 degrees so that no weighting scheme is needed. A 20-fold up-sampling is assumed to simulate x-ray beam's propagation through the gratings Gl and G2 with periods 8 and 4 microm, respectively, while the intergrating distance is 193.6 mm (1/16 of the Tabolt distance). The dimension of the detector cell for data acquisition ranges from 32 x 32 to 128 x 128 microm2, while the field of view in data acquisition is 40.96 x 40.96 mm2. A uniform water phantom with a diameter 37.68 mm is employed to study the NPS, with its complex refraction coefficient n = 1 - delta + ibeta = 1 - 2.5604 x 10(-7) + i1.2353 x 10(-10). The x-ray flux ranges from 10(6) to 10(8) photon/cm2.projection and observes the Poisson distribution, which is consistent with that of micro-CT in preclinical applications. The image matrix of reconstructed water phantom is 1280 x 1280, and a total of 180 regions at 128 x 128 matrix are used for NPS calculation via 2D Fourier Transform in which adequate zero padding is applied to avoid aliasing. The preliminary data show that the differential phase contrast CT manifests its NPS with a l/|k| trait, while the distribution of the conventional CTs NPS observes |k|. This accounts for the significant difference in their noise granularity and the differential phase contrast CTs substantial advantage in noise over the conventional CT, particularly, in the situations where the detector cell size for data acquisition is smaller than 100 microm. The differential phase contrast CT detects the projection of refractive coefficient's derivative and uses the Hilbert filter for image reconstruction, which leads to the radical difference in its NPS and the advantage in noise in comparison to that of the conventional CT.

PurposeTo develop data acquisition and image reconstruction methods to enable high‐resolution 1H MR spectroscopic imaging (MRSI) of the brain, using the recently proposed subspace‐based spectroscopic imaging framework called SPICE (SPectroscopic Imaging by exploiting spatiospectral CorrElation).Theory and MethodsSPICE is characterized by the use of a subspace model for both data acquisition and image reconstruction. For data acquisition, we propose a novel spatiospectral encoding scheme that provides hybrid data sets for determining the subspace structure and for image reconstruction using the subspace model. More specifically, we use a hybrid chemical shift imaging /echo‐planar spectroscopic imaging sequence for two‐dimensional (2D) MRSI and a dual‐density, dual‐speed echo‐planar spectroscopic imaging sequence for three‐dimensional (3D) MRSI. For image reconstruction, we propose a method that can determine the subspace structure and the high‐resolution spatiospectral reconstruction from the hybrid data sets generated by the proposed sequences, incorporating field inhomogeneity correction and edge‐preserving regularization.ResultsPhantom and in vivo brain experiments were performed to evaluate the performance of the proposed method. For 2D MRSI experiments, SPICE is able to produce high‐SNR spatiospectral distributions with an approximately 3 mm nominal in‐plane resolution from a 10‐min acquisition. For 3D MRSI experiments, SPICE is able to achieve an approximately 3 mm in‐plane and 4 mm through‐plane resolution in about 25 min.ConclusionSpecial data acquisition and reconstruction methods have been developed for high‐resolution 1H‐MRSI of the brain using SPICE. Using these methods, SPICE is able to produce spatiospectral distributions of 1H metabolites in the brain with high spatial resolution, while maintaining a good SNR. These capabilities should prove useful for practical applications of SPICE. Magn Reson Med 76:1059–1070, 2016. © 2015 Wiley Periodicals, Inc.

X-ray differential phase-contrast tomographic reconstruction with a phase line integral retrieval filter

Highly constrained back-projection (HYPR) is a data acquisition and reconstruction method that provides very rapid frame update rates and very high spatial resolution for a time series of images while maintaining a good signal-to-noise ratio and high image quality. In this study we used simulations to evaluate the temporal and spatial characteristics of images produced using the HYPR algorithm. The simulations demonstrate that spatial accuracy is well maintained in the images and the temporal changes in signal intensity are represented with high fidelity. The waveforms representing signal intensity as a function of time obtained from regions-of-interest placed in simulated objects track the true curves very well, with variations from the truth occurring only when objects with very different temporal behavior are very close to each other. However, even when objects with different temporal characteristics are touching, their influences on each other are small.

We have worked on multi-dimensional magnetic resonance imaging (MRI) data acquisition and related image reconstruction methods that aim at reducing the MRI scan time. To achieve this scan-time reduction we have combined the approach of 'increasing the speed' of k-space acquisition with that of 'deliberately omitting' acquisition of k-space trajectories (sparse sampling). Today we have a whole range of (sparse) sampling distributions and related reconstruction methods. In the context of a European Union Training and Mobility of Researchers project we have decided to integrate all methods into one coordinating software system. This system meets the requirements that it is highly structured in an object-oriented manner using the Unified Modeling Language and the Java programming environment, that it uses the client-server approach, that it allows multi-client communication sessions with facilities for sharing data and that it is a true distributed computing system with guaranteed reliability using core activities of the Java Jini package.

Vertical stereographic aerial photographs obtained as photographic plates or, more recently, as digital images represent a primary source of data for desk studies on all engineering projects. New methods of data acquisition from both airborne and spacecraft-based scanners provide unparalleled opportunities to obtain high-resolution data. However, interpretation of the images remains as much an art as a science and is critically dependent on the skill and experience of the interpreter. Relevant experience can be obtained only by the practice of ground-truthing an interpretation that the interpreter has carried out. Although it has rarely been quantified there are important lessons for all engineering projects on the divergence between the interpreted image and the actual ground situation. Some of these are exemplified in a case study undertaken by the authors using large-scale aerial photographs for a landslide hazard investigation in Spain. Based on this investigation it can be assumed that up to 50% of landslide features of engineering geological significance might not have been identified by the aerial photograph interpretation. The alternative is to use the images to divide the landscape into terrain units that allow the landslide potential to be evaluated. It can be demonstrated that this approach is more effective than trying to create a landslide inventory based on aerial photographs alone. Given the potential expansion in the use of large-scale image analysis associated with the recent improvement in data acquisition systems this has implications for the use of images and the training of interpreters.

The rate of development of open government data (OGD) portals has been fast in recent years due to potential benefits of the utilization of OGD. However, scholars have emphasized lack of use as a key problem in the realization of these benefits. Although studies have been carried out to understand decisive factors in OGD utilization from the aspects of either portals or users, they failed to consider the interaction between the two. Therefore, our study carried out an analysis of the interaction between users and OGD portals during users’ data acquisition process from three aspects: data acquisition methods, data quality requirements, and helping functions. We carried out a survey in a Chinese population to collect data for analysis. Results show users’ high acceptance of keyword search as their method for data acquisition through OGD portals but browsing showed higher usage frequency and was a more stable data acquisition behavior. Females show better acceptance of regular recommendations (e.g. RSS) based on their visiting histories than males. Users’ age, education background and occupation affect their demands of different data quality attributes. Our analysis also shows positive relationship between users’ data acquisition habits with their demands of data quality, users’ need of help with their feelings of difficulties in using the portal, and users’ need of help with their demands of data quality. We suggest promoting OGD utilization by offering better helping functions and improving data qualities in future development of OGD portals.

A new marine environmental data acquisition and transmission system that can monitor multiple environment parameters of an ocean fixed-point vertical profile is described. The system collects, archives marine profiling multi-parameter data and transmits them to Surveillance center through satellite communication. It consists of Buoy Electronic and Communication subsystem, Magnetic Coupling Communication subsystem, Underwater Data Acquisition and Storage subsystem. This paper mainly describes the detailed information about the key technologies, including multi-serial port communication technology, method of multi-source data acquisition, underwater inductive coupling data transmission technology and technology of low power consumption design, also information about system’s hardware and software design is given. Marine experiment results show that this system can works well in less than 300m depth, due to the careful low power consumption design, the system can continuously work for more than 90 days, the magnetic coupling data transmission subsystem can reliably transfer data at rate less than 9600bps through Serial RS232.

Data acquisition for automated processing is a central aspect of clinical trials with large numbers of cases because of their extensive demand for manpower. Scientific data can be collected using data forms, which are created in Hypertext Markup Language and published on the Internet. The completed data form can be returned via E-mail or Common Gateway Interface-Script and forwarded into a study database. For the Internet-based data acquisition of a prospective multicenter trial (e.g., on endophthalmitis incidence after cataract extraction), we developed two special HTML forms that can be opened in the ophthalmology department's homepage. A large number of acquired anonymous data has been collected via Internet and automatically transferred into the trial database. The Internet provides a fast and easy avenue for the acquisition of scientific data. This method of data acquisition and data processing will become more common place in multicenter clinical trials.

The helical scan X-ray CT is useful for high speed acquisition of three dimensional image data. In image reconstruction from helical scan data, a set of sequential data is used and the data are interpolated to produce projection data which reconstruct an image of a given cross section. This interpolation sometimes causes artifacts in the reconstructed image. We propose a new data acquisition method which minimizes the effect of scanning slice position in the axial direction. The proposed method inclines an X-ray detector array in the direction of rotation. The tilted angle is defined as arctan(/spl theta/L/2R/spl pi/tan/spl theta/), where L is the moving distance of a table per rotation and R is the radius of rotation of the X-ray source. The angle /spl theta/ is the orthogonal projection of the half of a fan angle onto the parallel beam projection plane. Simulation results showed that our method eliminated the low frequency distortion and improved the spatial resolution in the axial direction.

To investigate feasibility of applying deep learning image reconstruction (DLIR) algorithm in a low-kilovolt enhanced scan of the upper abdomen. A total of 64 patients (BMI<28) are selected for the enhanced upper abdomen scan and divided evenly into two groups. The tube voltages in Group A are 100kV in arterial phase and 80kV in venous phase, while tube voltages are 120kV during two phases in Group B. Image reconstruction algorithms used in Group A include the filtered back projection (FBP) algorithm, the adaptive statistical iterative reconstruction-Veo (ASIR-V 40% and 80%) algorithm, and the DLIR algorithm (DL-L, DL-M, DL-H). Image reconstruction algorithm used in Group B is ASIR-V40%. The different reconstruction algorithm images are used to measure the common hepatic artery, liver, renal cortex, erector spinae, and subcutaneous adipose in the arterial phase and the average CT value and standard deviation of the portal vein, liver, spleen, erector spinae, and subcutaneous adipose in the portal phase. The signal-to-noise ratio (SNR) is calculated, and the images are also scored subjectively. In Group A, noise in the aorta, liver, portal vein (the portal phase), spleen (the portal phase), renal cortex, retroperitoneal adipose, and muscle is significantly lower in both the DL-H and ASIR-V80% images, and the SNR is significantly higher than those in the remaining groups (P<0.05). The SNR of each tissue and organ in Group B is not significantly different from that in DL-M, DL-L, and ASIR-V40% in Group A (P>0.05). The subjective image quality scores in the DL-H and B groups are higher than those in the other groups, and the FBP group has significantly lower image quality than the remaining groups (P<0.05). For upper abdominal low-kilovolt enhanced scan data, the DLIR-H gear yields a more satisfactory image quality than the FBP and ASIR-V.

The spiral scan X-ray CT is useful for high speed acquisition of three dimensional image data. In image reconstruction of spiral scan data, a set of sequential data is used and the data are interpolated to produce projection data which reconstruct an image of a given cross section. This interpolation sometimes causes artifacts in the reconstructed image. We propose a new data acquisition method which minimizes the effect of the scanning slice position in the axial direction. The proposed method inclines an X-ray detector array in the direction of rotation. The tilted angle is defined as arctan(/spl theta/L/2R/spl pi/ tan /spl theta/), where L is the distance a table moves per rotation and R is the radius of rotation of the X-ray source. The angle B is the orthogonal projection of the half of a fan angle onto the parallel beam projection plane. Simulation results showed that our method eliminates the low frequency distortion and improves the spatial resolution in the axial direction.

Towards an automated image-based estimation of building age as input for Building Energy Modeling (BEM)

This paper overviews various methods of data acquisition from GEM detectors. Presented are currently working systems in tokamaks. The data acquisition methods are divided into two parts. First part, devoted to analog signal processing , describes different approaches for signals acquisition, i.e. pulse amplifying and shaping, ASIC use, delay lines. Digital data acquisition part describes presently used high speed interfaces and system standards. Described are also different approaches for data handling, i.e. online analysis, data reduction, system topologies.

This paper outlines the three main field bus type standards: FOUNDATION Fieldbus; WorldFIP; and the CAN bus, each of which have great advantages over traditional instrumentation networking technology. The paper shows, using their specification, how they improve traditional control and data acquisition methods. By analysing the main fieldbus types the paper shows how they are more robust, how they can be used to distribute data around the control system (rather than centralise it in traditional systems), provided increased diagnostic information, are easy to implement, fault confinement, and move simple control operations from the main controller to the local environment. This will help to segment industrial plants into zones which can control themselves. The main control will then be responsibility of high-level control, and interzone communications. The paper concludes by discussing how fieldbusses will answer many of the problems of previous control and data acquisition systems