Projection Reconstruction Method Research Articles

Filtered back projection vs. iterative reconstruction for CBCT: effects on image noise and processing time.

To assess the effect of standard filtered back projection (FBP) and iterative reconstruction (IR) methods on CBCT image noise and processing time (PT), acquired with various acquisition parameters with and without metal artefact reduction (MAR). CBCT scans using the Midmark EIOS unit of a human mandible embedded in soft tissue equivalent material with and without the presence of an implant at mandibular first molar region were acquired at various acquisition settings (milliamperages [4mA-14mA], FOV [5 × 5, 6 × 8, 9 × 10 cm], and resolutions [low, standard, high] and reconstructed using standard FBP and IR, and with and without MAR. The processing time was recorded for each reconstruction. ImageJ was used to analyze specific axial images. Radial transaxial fiducial lines were created relative to the implant site. Standard deviations of the gray density values (image noise) were calculated at fixed distances on the fiducial lines on the buccal and lingual aspects at specific axial levels, and mean values for FBP and IR were compared using paired t-tests. Significance was defined as p < 0.05. The overall mean for image noise (± SD) for FBP was 198.65 ± 55.58 and 99.84 ± 16.28 for IR. IR significantly decreased image noise compared to FBP at all acquisition parameters (p < 0.05). Noise reduction among different scanning protocols ranged between 29.7% (5 × 5 cm FOV) and 58.1% (5mA). IR increased processing time by an average of 35.1 s. IR significantly reduces CBCT image noise compared to standard FBP without substantially increasing processing time.

Tomographic reconstruction with Mantid Imaging

Mantid Imaging has been developed to provide a graphical reconstruction process for users of neutron imaging instruments to eliminate the need to fall back on commercial software. Mantid Imaging builds on algorithms provided by libraries including Astra Toolbox and Tomopy to offer noise reduction, artifact removal, alignment, filtered back projection and iterative reconstruction methods. Extra functionality was added by using algorithms from ALGOTOM for ring removal and from the Core Imaging Library (CIL) for regularised 3D reconstruction.Mantid Imaging 2.4 has recently been released. It is an open source Python GUI, runs under Linux and Windows and can easily be installed on end user systems. Mantid Imaging is aimed at users with no programming background and with little image processing experience. At ISIS Mantid Imaging runs on the ISIS-Data-Analysis-as-a-Service (IDAaaS) platform, which is remotely accessible with any modern web browser and gives users access to sufficient hardware resources to handle large datasets. Extensions of Mantid Imaging for energy-resolved neutron imaging are planned for the future.

ВЫБОР МЕТОДА РЕКОНСТРУКЦИИ ПОЗИТРОННО-ЭМИССИОННЫХ ЭКГ-СИНХРОНИЗОВАННЫХ ИССЛЕДОВАНИЙ И ЕГО ВЛИЯНИЕ НА РАССЧИТАННЫЕ ОБЪЁМНЫЕ ПОКАЗАТЕЛИ ФУНКЦИИ МИОКАРДА ЛЕВОГО ЖЕЛУДОЧКА И ВИЗУАЛЬНОЕ КАЧЕСТВО ИЗОБРАЖЕНИЙ

Ischemic heart disease is one of the leading causes of mortality in the Russian Federation. Timely diagnosis of this condition allows you to determine the optimal treatment tactics. Positron emission tomography with 18-fluorodeoxyglucose is a method for verifying viable cardiac tissue in patients with myocardial infarction. The methods used for the reconstruction of positron emission tomograms can affect the quantitative indicators of the contractile function of the myocardium. Materials and methods. The study retrospectively included 12 patients who underwent PET/CT with 18-fluorodeoxyglucose, the results of which were reconstructed using filtered back projection methods and iterative reconstruction, with ECG synchronization and division of ECG R-R intervals into 8, 10 and 16 frames. The obtained images were evaluated visually by two radiologists, and the quantitative parameters characterizing the contractile function of the left ventricular myocardium were compared in pairs. Results. There were no significant differences in the assessment of quantitative indicators such as end-systolic and diastolic volumes, stroke volume and ejection fraction. However, the iterative reconstruction results show less data scatter than the filtered back projection reconstruction method. In visual analysis, the best quality of reconstructions by iterative methods is noted. Conclusions. Thus, the recommended method for both visual analysis and quantification is iterative reconstruction, regardless of the number of timing windows used. A spread in the number of used reconstructed fragments of the cardiac cycle in the range of 8-16, commonly used in clinical practice, can be recommended.

Development of a muon tomography application with Micromegas detectors

The application of muon tomography method in small scale, for the imaging of a five-centimeter side lead cube, is being examined in the present work. The representation of the object is being achieved by using the transmission muography technique, in which the “free-sky” muon flux is compared to the muon flux measured within the acceptance of the detector. This comparison yields information about the absorption of the muons as they pass through the object under investigation. Also, a projective reconstruction method called “Back Projection” is tested by being applied on the data, providing information about the location of the object and its dimensions. This project has been carried out within the frame of EKATY programme, which aims to the innovative imaging of the subsurface of archaeological sites and the interior of structural elements of monuments in three and four dimensions.

An Improved Wave Velocity Model for Acoustic Emission Source Localization in Heterogeneous Rock Materials with Unknown Inclusions

The accuracy of locating acoustic emission (AE) source location is closely related to the reasonability of the adopted wave velocity model. However, it is literally hard to obtain an accurate wave velocity model for a heterogeneous rock material due to its inner invisible inclusions and local defects, making the AE source localization very challenging. To obtain a more appropriate wave velocity model for the heterogeneous rock material having unknown inclusions, in this study the projective reconstruction method (PRM) was utilized to determine the wave velocity model. Because the PRM is irrelevant to the continuous assumption, the proposed wave velocity model can well reflect the discontinuous characteristics of the real wave velocity field in rock materials. Then, the proposed wave velocity model was incorporated into an arrival time-based governing equation to locate the AE source. To demonstrate the effectiveness of the proposed method in improving the AE source location accuracy and monitoring the rock failure process, lead-break tests and three-point bending tests were conducted on the composite rock and rock-like specimens, respectively. Results show that the improved wave velocity model obtained by the PRM can significantly improve the accuracy of AE source location in the heterogeneous rock material with unknown inclusions.

IMAGE QUALITY AND POTENTIAL DOSE REDUCTION USING ADVANCED MODELED ITERATIVE RECONSTRUCTION (ADMIRE) IN ABDOMINAL CT - A REVIEW.

Traditional filtered back projection (FBP) reconstruction methods have served the computed tomography (CT) community well for over 40 years. With the increased use of CT during the last decades, efforts to minimise patient exposure, while maintaining sufficient or improved image quality, have led to the development of model-based iterative reconstruction (MBIR) algorithms from several vendors. The usefulness of the advanced modeled iterative reconstruction (ADMIRE) (Siemens Healthineers) MBIR in abdominal CT is reviewed and its noise suppression and/or dose reduction possibilities explored. Quantitative and qualitative methods with phantom and human subjects were used. Assessment of the quality of phantom images will not always correlate positively with those of patient images, particularly at the higher strength of the ADMIRE algorithm. With few exceptions, ADMIRE Strength 3 typically allows for substantial noise reduction compared to FBP and hence to significant (≈30%) patient dose reductions. The size of the dose reductions depends on the diagnostic task.

Application of sigmoidal optimization to reconstruct nuclear medicine image: Comparison with filtered back projection and iterative reconstruction method

High levels for noise and a loss of true signal make the quantitative interpretation of nuclear medicine (NM) images difficult. An application of profile optimization using a sigmoidal function in this study was used to acquire the NM images with high quality. And the images were acquired by using three kinds of reconstruction method using each same sinogram: a standard filtered back-projection (FBP), an iterative reconstruction (IR) technique, and the sigmoidal function profile optimization (SFPO). Comparison of image according to reconstruction method was performed to show a superiority of the SFPO for imaging. The images reconstructed by using the SFPO showed an average of 1.49 times and of 1.17 times better in contrast than the results obtained using the standard FBP and the IR technique, respectively. Higher signal to noise ratios were obtained as an average of 12.30 times and of 3.77 times than results obtained using the standard FBP and the IR technique, respectively. This study confirms that reconstruction with SFPO (vs FBP and vs IR) can lead to better lesion detectability and characterization with noise reduction. It can be developed for future reconstruction technique for the NM imaging.

Statistical CT reconstruction using region-aware texture preserving regularization learning from prior normal-dose CT image

In some clinical applications, prior normal-dose CT (NdCT) images are available, and the valuable textures and structure features in them may be used to promote follow-up low-dose CT (LdCT) reconstruction. This study aims to learn texture information from the NdCT images and leverage it for follow-up LdCT image reconstruction to preserve textures and structure features. Specifically, the proposed reconstruction method first learns the texture information from those patches with similar structures in NdCT image, and the similar patches can be clustered by searching context features efficiently from the surroundings of the current patch. Then it utilizes redundant texture information from the similar patches as a priori knowledge to describe specific regions in the LdCT image. The advanced region-aware texture preserving prior is termed as ‘RATP’. The main advantage of the PATP prior is that it can properly learn the texture features from available NdCT images and adaptively characterize the region-specific structures in the LdCT image. The experiments using patient data were performed to evaluate the performance of the proposed method. The proposed RATP method demonstrated superior performance in LdCT imaging compared to the filtered back projection (FBP) and statistical iterative reconstruction (SIR) methods using Gaussian regularization, Huber regularization and the original texture preserving regularization.

Iterative projection reconstruction for fast and efficient image upsampling

With the development of ultra-high-resolution display devices, the visual perception of fine texture details is becoming increasingly important. Traditional image upsampling methods suffer from either loss of high-frequency texture details or very high time cost. In this paper, we propose an iterative projection reconstruction (IPR) method for fast and efficient image upsampling. The proposed method refines high-frequency texture details with an iterative projection process, and utilizes the pre-computed projection matrix to accelerate the example-based image reconstruction. As a result, the proposed method can reproduce fine texture details with low time cost. Experimental results demonstrate that the proposed method outperforms some state-of-the-art methods.

A nitrogen-vacancy spin based molecular structure microscope using multiplexed projection reconstruction

Methods and techniques to measure and image beyond the state-of-the-art have always been influential in propelling basic science and technology. Because current technologies are venturing into nanoscopic and molecular-scale fabrication, atomic-scale measurement techniques are inevitable. One such emerging sensing method uses the spins associated with nitrogen-vacancy (NV) defects in diamond. The uniqueness of this NV sensor is its atomic size and ability to perform precision sensing under ambient conditions conveniently using light and microwaves (MW). These advantages have unique applications in nanoscale sensing and imaging of magnetic fields from nuclear spins in single biomolecules. During the last few years, several encouraging results have emerged towards the realization of an NV spin-based molecular structure microscope. Here, we present a projection-reconstruction method that retrieves the three-dimensional structure of a single molecule from the nuclear spin noise signatures. We validate this method using numerical simulations and reconstruct the structure of a molecular phantom β-cyclodextrin, revealing the characteristic toroidal shape.

TU‐G‐204‐07: A Research Pipeline to Simulate a Wide Range of CT Image Acquisition and Reconstruction Parameters and Assess the Performance of Quantitative Imaging and CAD Systems

Purpose:Quantitative Imaging and CAD tasks performed with CT (e.g. lung nodule detection, assessment of tumor size, etc.) may be sensitive to image acquisition and reconstruction parameters such as dose level, image thickness and reconstruction method (FBP, iterative, etc.). The purpose of this work was to develop a research pipeline for generating CT image series that represent a wide variety of acquisition and reconstruction conditions under which CAD and Quantitative Imaging performance would be evaluated.Methods:With IRB approval, we have collected the raw CT data from hundreds of patients. These raw sinogram files serve as the input to the research pipeline. To simulate a wide range of dose levels, we developed software which adds noise to the sinogram. Multiple reduced‐dose sinograms can be generated for a single patient, and those reduced‐dose sinograms are then fed either to the scanner's reconstruction engine or to our in‐house reconstruction engine; each has conventional filtered back projection (FBP) and iterative reconstruction methods. After generating image series across a range of dose levels and reconstruction methods, we can evaluate the performance of various quantitative imaging or CAD tools in tasks such as automated and semi‐automated lesion segmentation, assessment of lesion size, and measurement of density or texture.Results:We have successfully applied this pipeline across a range of clinical CT applications, including: (1) chest oncology, where the pipeline was used to quantify the effects of dose and reconstruction method on nodule volumetry, and (2) lung cancer screening, where the pipeline is being used to measure the robustness of an automated CAD algorithm with respect to dose.Conclusion:The acquisition/reconstruction pipeline shows promise for investigating and quantifying the effects of dose and reconstruction method on various clinical CT applications.NCI grant U01 CA181156 (Quantitative Imaging Network); Tobacco Related Disease Research Project grant 22RT‐0131.

SU-E-I-30: Effect of Automatic Tube Voltage Selection and Reconstruction Method On CT Dose Reduction

Purpose: To study the effect of automatic tube voltage selection and reconstruction method on CT dose reduction. Methods: A retrospective study was conducted to gather data from 126 CT exams among 80 patients from 3 different CT scanners. Data on scan parameters was collected and categorized for 3 different patient sizes: small, medium and large. For each patient group, exams using manual selection of tube voltage and automatic selection of tube voltage were compared for dose reduction. The influence of reconstruction method and automatic or manual tube voltage selection was also studied. Results: Dose reduction was observed in all patient size categories with the largest dose reduction of 55% seen in the medium sized patients and 35% reduction in the small and large patients. The patients who underwent both a manual and automatic tube voltage selection for their CT study also showed similar dose reduction. Use of iterative reconstruction method and automatic tube voltage selection also showed a 30% dose reduction when compared with manual tube voltage selection and filtered back projection reconstruction method. Dose reduction of up to 45% was observed for both automatic and manual tube voltage selection irrespective of which reconstruction method was used. Conclusion: Using automatic tube voltage selection and iterative reconstruction demonstrated significant dose reduction compared to manual tube voltage selection and filtered back reconstruction method. Between the different generation CT scanners used in this study, the scanner with the most advanced technology demonstrated the most significant dose reduction.

A Constrained Variable Projection Reconstruction Method for Photoacoustic Computed Tomography Without Accurate Knowledge of Transducer Responses.

Photoacoustic computed tomography (PACT) is an emerging computed imaging modality that exploits optical contrast and ultrasonic detection principles to form images of the absorbed optical energy density within tissue. When the imaging system employs conventional piezoelectric ultrasonic transducers, the ideal photoacoustic (PA) signals are degraded by the transducers' acousto-electric impulse responses (EIRs) during the measurement process. If unaccounted for, this can degrade the accuracy of the reconstructed image. In principle, the effect of the EIRs on the measured PA signals can be ameliorated via deconvolution; images can be reconstructed subsequently by application of a reconstruction method that assumes an idealized EIR. Alternatively, the effect of the EIR can be incorporated into an imaging model and implicitly compensated for during reconstruction. In either case, the efficacy of the correction can be limited by errors in the assumed EIRs. In this work, a joint optimization approach to PACT image reconstruction is proposed for mitigating errors in reconstructed images that are caused by use of an inaccurate EIR. The method exploits the bi-linear nature of the imaging model and seeks to refine the measured EIR during the process of reconstructing the sought-after absorbed optical energy density. Computer-simulation and experimental studies are conducted to investigate the numerical properties of the method and demonstrate its value for mitigating image distortions and enhancing the visibility of fine structures.

A projective reconstruction method of underground or hidden structures using atmospheric muon absorption data

Muon absorption radiography is an imaging technique based on the analysis of the attenuation of the cosmic-ray muon flux after traversing an object under examination. While this technique is now reaching maturity in the field of volcanology for the imaging of the innermost parts of the volcanic cones, its applicability to other fields of research has not yet been proved. In this paper we present a study concerning the application of the muon absorption radiography technique to the field of archaeology, and we propose a method for the search of underground cavities and structures hidden a few metres deep in the soil (patent [1]). An original geometric treatment of the reconstructed muon tracks, based on the comparison of the measured flux with a reference simulated flux, and the preliminary results of specific simulations are discussed in details.

Rotating Slice Scanning Mode for Traveling Wave MPI

Since the introduction of magnetic particle imaging in 2005, several different types of scanner were presented. One of them is the traveling wave magnetic particle imaging (TWMPI) scanner. It uses for imaging a dynamic linear gradient array for a dynamic generation of a strong gradient and field free point. An unresolved issue of the TWMPI approach so far is the non-isotropic spatial resolution. As an alternative in this paper, a rotating slice scanning mode for TWMPI is presented to overcome this issue. This approach rotates the scanning-slices around the scanner axis and uses a projection reconstruction method to get a 3-D volume with a high isotropic resolution.

Limited-angle reverse helical cone-beam CT for pipeline with low rank decomposition

In this paper, tomographic imaging of pipeline in service by cone-beam computed tomography (CBCT) is studied. With the developed scanning strategy and image model, the quality of reconstructed image is improved. First, a limited-angle reverse helical scanning strategy based on C-arm computed tomography (C-arm CT) is developed for the projection data acquisition of pipeline in service. Then, an image model which considering the resemblance among slices of pipeline is developed. Finally, split Bregman method based algorithm is implemented in solving the model aforementioned. Preliminary results of simulation experiments show that the projection data acquisition strategy and reconstruction method are efficient and feasible, and our method is superior to Feldkamp–Davis–Kress (FDK) algorithm and simultaneous algebraic reconstruction technique (SART).

Dense Spray Patternation using Optical Tomography

Optical tomography was used to measure the pattern of spray cross-section. The maximum-likelihood estimation (MLE) algorithm was used to reconstruct the spray cross-section from the measured transmission rate of the spray. A swirl-type injector was used to form an optically dense spray, and the test was carried out in a high-pressure chamber, to control the pressure condition of the test site. Before the experiment, the reliability of the MLE-based reconstruction algorithm was verified, by comparing it with a conventional filtered back projection reconstruction (FBP) method. The MLE algorithm showed superior reconstruction of the image. In the spray patternation experiment, the results of the optical tomography and optical line patternator, which uses Mie scattering signal information, were compared. While measuring the cross-section of optically dense spray, the intensity of the scattering signal had attenuated to an uncorrectable level, which led to incorrect spray pattern measurement by the optical line patternator. However, reliable results were obtained by optical tomography, under the same condition. Finally, the pattern of the optically dense spray was measured at various chamber pressures, of up to 3 MPa. As the chamber pressure increased, the hollow cone-shaped swirl spray shrank, and the attenuation coefficient value of the inner region increased.

Structural Determination of Ordered Porous Solids by Electron Crystallography

Knowing the structure of porous materials is essential for understanding their properties and exploiting them for applications. Electron crystallography has two main advantages compared to X‐ray diffraction for structure determination. Crystals too small or too complicated to be studied by X‐ray diffraction can be studied by electron crystallography. The crystallographic structure factor phase information, which is lost in X‐ray diffraction, can be obtained from high‐resolution transmission electron microscopy (HRTEM) images. Here, different electron microscopic techniques and their applications for structure determination of porous materials are reviewed. The recently developed automated diffraction tomography (ADT), the rotation electron diffraction (RED), and the through‐focus structure projection reconstruction (QFcous) methods make the structure determination by electron crystallography more feasible for non‐TEM experts and as efficient as that by X‐ray diffraction. How the various electron crystallographic methods are chosen are demonstrated and these methods used for solving different structural problems in porous materials. The benefits of combining electron crystallography and X‐ray diffraction for studying complex zeolite structures are also shown. A large number of examples are given to demonstrate the use of various electron crystallographic techniques for structure determination of zeolites, metal‐organic frameworks and ordered mesoporous materials. These electron crystallographic methods are general and can also be used for structural studies of other functional materials.

Application of Ultra-Low Field HTS-SQUID NMR/MRI to Contaminant Detection in Food

We constructed an ultra-low field nuclear magnetic resonance (NMR)/magnetic resonance imaging (MRI) system utilizing a high-temperature superconductor (HTS) SQUID and permanent magnet for application of contaminant detection in food and drink. In order to compensate shortage of signal-to-noise ratio of the HTS-SQUID-based system, a pair permanent magnet of 1.1 T was employed for prepolarization field. It was combined with a sample transfer apparatus, which transferred a water sample with contaminant in a 10-ml glass bottle from the magnet to under the SQUID magnetometer within 0.5 s. Feasibility of contaminant detection in drink was demonstrated using the system by measuring NMR and 1-D MRI of water samples including contaminants of stainless steel, aluminum, and polymer. 2-D MRI measurement of a sample with partitioned water by silicone bulk was demonstrated employing the filtered back projection reconstruction method.

Projective Electrical Impedance Reconstruction with Two Measurements

This paper presents a projective reconstruction method of electrical impedance distribution using two boundary measurements of current-voltage data. The proposed method has a major advantage over existing electrical impedance tomography systems: relatively high resolution impedance image in a near-surface region underneath the voltage-sensing probe that is placed on a skin surface. We attach two pairs of electrodes on the border of the probe in such a way that each pair of electrodes generates electrical current flowing underneath the voltage-sensing probe and two currents flow across each other. A careful analysis of the measured data with respect to local perturbation of admittivity leads to the projective reconstruction method and its rationale. Numerical simulations show that the proposed method successfully reconstructs high resolution image of local perturbation of admittivity, due to object position changes or admittivity value changes or the both, in a near-surface region underneath the probe.