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iterative reconstruction

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https://www.readbyqxmd.com/read/28103283/orthogonal-procrustes-analysis-for-dictionary-learning-in-sparse-linear-representation
#1
Giuliano Grossi, Raffaella Lanzarotti, Jianyi Lin
In the sparse representation model, the design of overcomplete dictionaries plays a key role for the effectiveness and applicability in different domains. Recent research has produced several dictionary learning approaches, being proven that dictionaries learnt by data examples significantly outperform structured ones, e.g. wavelet transforms. In this context, learning consists in adapting the dictionary atoms to a set of training signals in order to promote a sparse representation that minimizes the reconstruction error...
2017: PloS One
https://www.readbyqxmd.com/read/28103193/comprehensive-use-of-curvature-for-robust-and-accurate-online-surface-reconstruction
#2
Damien Lefloch, Markus Kluge, Hamed Sarbolandi, Tim Weyrich, Andreas Kolb
Interactive real-time scene acquisition from hand-held depth cameras has recently developed much momentum, enabling applications in ad-hoc object acquisition, augmented reality and other fields. A key challenge to online reconstruction remains error accumulation in the reconstructed camera trajectory, due to drift-inducing instabilities in the range scan alignments of the underlying iterative-closest-point (ICP) algorithm. Various strategies have been proposed to mitigate that drift, including SIFT-based pre-alignment, color-based weighting of ICP pairs, stronger weighting of edge features, and so on...
January 5, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
https://www.readbyqxmd.com/read/28102693/a-phantom-study-for-ground-glass-nodule-detectability-using-chest-digital-tomosynthesis-with-iterative-reconstruction-algorithm-by-ten-observers-association-with-radiation-dose-and-nodular-characteristics
#3
Katsunori Miyata, Yukihiro Nagatani, Mitsuru Ikeda, Masashi Takahashi, Norihisa Nitta, Satoru Matsuo, Shinichi Ohta, Hideji Otani, Ayumi Nitta-Seko, Yoko Murakami, Keiko Tsuchiya, Akitoshi Inoue, Sayaka Misaki, Khishigdorj Erdenee, Tetsuo Kida, Kiyoshi Murata
OBJECTIVES: To compare detectability of simulated ground glass nodules (GGN) on chest digital tomosynthesis (CDT) among 12 images obtained at 6 radiation doses using 2 reconstruction algorithms and analyze its association with nodular size and density. METHODS: Seventy-four simulated GGNs (5, 8 and 10mm in diameter/-630 and -800 HU in density) were placed in a chest phantom in 14 nodular distribution patterns. Twelve sets of coronal images were obtained using CDT at 6 radiation doses: 120kV-10mA/20mA/80mA/160mA, 100kV-80mA and 80kV-320mA with and without iterative reconstruction (IR)...
January 19, 2017: British Journal of Radiology
https://www.readbyqxmd.com/read/28102510/influence-of-dose-reduction-and-iterative-reconstruction-on-ct-calcium-scores-a-multi-manufacturer-dynamic-phantom-study
#4
N R van der Werf, M J Willemink, T P Willems, M J W Greuter, T Leiner
To evaluate the influence of dose reduction in combination with iterative reconstruction (IR) on coronary calcium scores (CCS) in a dynamic phantom on state-of-the-art CT systems from different manufacturers. Calcified inserts in an anthropomorphic chest phantom were translated at 20 mm/s corresponding to heart rates between 60 and 75 bpm. The inserts were scanned five times with routinely used CCS protocols at reference dose and 40 and 80% dose reduction on four high-end CT systems. Filtered back projection (FBP) and increasing levels of IR were applied...
January 19, 2017: International Journal of Cardiovascular Imaging
https://www.readbyqxmd.com/read/28102175/markerless-rat-head-motion-tracking-using-structured-light-for-brain-pet-imaging-of-unrestrained-awake-small-animals
#5
Alan Miranda, Steven Staelens, Sigrid Stroobants, Jeroen Verhaeghe
Preclinical positron emission tomography (PET) imaging in small animals is generally performed under anesthesia to immobilize the animal during scanning. More recently, for rat brain PET studies, methods to perform scans of unrestrained awake rats are being developed in order to avoid the unwanted effects of anesthesia on the brain response. Here, we investigate the use of a projected structure stereo camera to track the motion of the rat head during the PET scan. The motion information is then used to correct the PET data...
January 19, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28099226/computed-tomography-in-cystic-fibrosis-combining-low-dose-techniques-and-iterative-reconstruction
#6
Johannes Kahn, David Kaul, Ulrich Grupp, Georg Böning, Diane Renz, Doris Staab, Vera Schreiter, Florian Streitparth
OBJECTIVE: The aim of the study was to evaluate the impact of iterative reconstruction (IR) and low-kilovolt technique on dose reduction and image quality of chest computed tomography scans obtained in patients with cystic fibrosis (CF). METHODS: A total of 124 CF patients were examined; group A (n = 63) was examined with a dose reduction protocol using IR and group B (n = 61) with a standard protocol using filtered back projection. Further subgroups with tube voltage modulations were established...
January 18, 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28099224/comparison-of-model-based-iterative-reconstruction-adaptive-statistical-iterative-reconstruction-and-filtered-back-projection-for-detecting-hepatic-metastases-on-submillisievert-low-dose-computed-tomography
#7
Jung Hee Son, Seung Ho Kim, Jung-Hee Yoon, Yedaun Lee, Yun-Jung Lim, Seon-Jeong Kim
OBJECTIVE: The aim of the study was to compare the diagnostic performance of model-based iterative reconstruction (MBIR), adaptive statistical iterative reconstruction (ASIR), and filtered back projection (FBP) on submillisievert low-dose computed tomography (LDCT) for detecting hepatic metastases. METHODS: Thirty-eight patients having hepatic metastases underwent abdomen CT. Computed tomography protocol consisted of routine standard-dose portal venous phase scan (120 kVp) and 90-second delayed low-dose scan (80 kVp)...
January 18, 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28095203/avoiding-optimal-mean-%C3%A2-2-1-norm-maximization-based-robust-pca-for-reconstruction
#8
Minnan Luo, Feiping Nie, Xiaojun Chang, Yi Yang, Alexander G Hauptmann, Qinghua Zhang
Robust principal component analysis (PCA) is one of the most important dimension-reduction techniques for handling high-dimensional data with outliers. However, most of the existing robust PCA presupposes that the mean of the data is zero and incorrectly utilizes the average of data as the optimal mean of robust PCA. In fact, this assumption holds only for the squared [Formula: see text]-norm-based traditional PCA. In this letter, we equivalently reformulate the objective of conventional PCA and learn the optimal projection directions by maximizing the sum of projected difference between each pair of instances based on [Formula: see text]-norm...
January 17, 2017: Neural Computation
https://www.readbyqxmd.com/read/28092525/light-field-reconstruction-using-shearlet-transform
#9
Suren Vagharshakyan, Robert Bregovic, Atanas Gotchev
In this article we develop an image based rendering technique based on light field reconstruction from a limited set of perspective views acquired by cameras. Our approach utilizes sparse representation of epipolar-plane images (EPI) in shearlet transform domain. The shearlet transform has been specifically modified to handle the straight lines characteristic for EPI. The devised iterative regularization algorithm based on adaptive thresholding provides high-quality reconstruction results for relatively big disparities between neighboring views...
January 16, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
https://www.readbyqxmd.com/read/28089381/pet-ct-underlying-physics-instrumentation-and-advances
#10
I Torres Espallardo
Since it was first introduced, the main goal of PET/CT has been to provide both PET and CT images with high clinical quality and to present them to radiologists and specialists in nuclear medicine as a fused, perfectly aligned image. The use of fused PET and CT images quickly became routine in clinical practice, showing the great potential of these hybrid scanners. Thanks to this success, manufacturers have gone beyond considering CT as a mere attenuation corrector for PET, concentrating instead on design high performance PET and CT scanners with more interesting features...
January 12, 2017: Radiología
https://www.readbyqxmd.com/read/28089191/object-shape-dependency-of-in-plane-resolution-for-iterative-reconstruction-of-computed-tomography
#11
Tadanori Takata, Katsuhiro Ichikawa, Wataru Mitsui, Hiroyuki Hayashi, Kaori Minehiro, Keita Sakuta, Haruka Nunome, Kousuke Matsubara, Hiroki Kawashima, Yukihiro Matsuura, Toshifumi Gabata
The present study aimed to investigate whether the in-plane resolution property of iterative reconstruction (IR) of computed tomography (CT) data is object shape-dependent by testing columnar shapes with diameters of 3, 7, and 10cm (circular edge method) and a cubic shape with 5-cm side lengths (linear edge method). For each shape, objects were constructed of acrylic (contrast in Hounsfield units [ΔHU]=120) as well as a soft tissue equivalent material (ΔHU=50). For each shape, we measured the modulation transfer functions (MTFs) of IR and filtered back projection (FBP) using two multi-slice CT scanners at scan doses of 5 and 10mGy...
January 11, 2017: Physica Medica: PM
https://www.readbyqxmd.com/read/28086901/gpu-accelerated-voxel-driven-forward-projection-for-iterative-reconstruction-of-cone-beam-ct
#12
Yi Du, Gongyi Yu, Xincheng Xiang, Xiangang Wang
BACKGROUND: For cone-beam computed tomography (CBCT), which has been playing an important role in clinical applications, iterative reconstruction algorithms are able to provide advantageous image qualities over the classical FDK. However, the computational speed of iterative reconstruction is a notable issue for CBCT, of which the forward projection calculation is one of the most time-consuming components. METHOD AND RESULTS: In this study, the cone-beam forward projection problem using the voxel-driven model is analysed, and a GPU-based acceleration method for CBCT forward projection is proposed with the method rationale and implementation workflow detailed as well...
January 5, 2017: Biomedical Engineering Online
https://www.readbyqxmd.com/read/28081011/spectrum-reconstruction-method-based-on-the-detector-response-model-calibrated-by-x-ray-fluorescence
#13
Ruizhe Li, Liang Li, Zhiqiang Chen
Accurate estimation of distortion-free spectra is important but difficult in various applications, especially for spectral computed tomography. Two key problems must be solved to reconstruct the incident spectrum. One is the acquisition of the detector energy response. It can be calculated by Monte Carlo simulation, which requires detailed modeling of the detector system and a high computational power. It can also be acquired by establishing a parametric response model and be calibrated using monochromatic x-ray sources, such as synchrotron sources or radioactive isotopes...
February 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28079527/binary-moving-blocker-based-scatter-correction-in-cone-beam-computed-tomography-with-width-truncated-projections-proof-of-concept
#14
Ho Lee, Benjamin Fahimian, Lei Xing
This paper proposes a binary moving-blocker (BMB)-based technique for scatter correction in cone-beam computed tomography (CBCT). In concept, a beam blocker consisting of lead strips, mounted in front of the x-ray tube, moves rapidly in and out of the beam during a single gantry rotation. The projections are acquired in alternating phases of blocked and unblocked cone beams, where the blocked phase results in a stripe pattern in the width direction. To derive the scatter map from the blocked projections, one-dimensional B-Spline interpolation/extrapolation is applied by using the detected information in the shaded regions...
January 12, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28074785/deformable-registration-of-ct-and-cone-beam-ct-with-local-intensity-matching
#15
Seyoun Park, William Plishker, Harry Quon, John Wong, Raj Shekhar, Junghoon Lee
Cone-beam CT (CBCT) is a widely used intra-operative imaging modality in image-guided radiotherapy and surgery. A short scan followed by a filtered-backprojection is typically used for CBCT reconstruction. While data on the mid-plane (plane of source-detector rotation) is complete, off-mid-planes undergo different information deficiency and the computed reconstructions are approximate. This causes different reconstruction artifacts at off-mid-planes depending on slice locations, and therefore impedes accurate registration between CT and CBCT...
February 7, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28070242/computed-tomography-and-patient-risk-facts-perceptions-and-uncertainties
#16
REVIEW
Stephen P Power, Fiachra Moloney, Maria Twomey, Karl James, Owen J O'Connor, Michael M Maher
Since its introduction in the 1970s, computed tomography (CT) has revolutionized diagnostic decision-making. One of the major concerns associated with the widespread use of CT is the associated increased radiation exposure incurred by patients. The link between ionizing radiation and the subsequent development of neoplasia has been largely based on extrapolating data from studies of survivors of the atomic bombs dropped in Japan in 1945 and on assessments of the increased relative risk of neoplasia in those occupationally exposed to radiation within the nuclear industry...
December 28, 2016: World Journal of Radiology
https://www.readbyqxmd.com/read/28066840/task-based-design-of-fluence-field-modulation-in-ct-for-model-based-iterative-reconstruction
#17
Grace J Gang, Jeffrey H Siewerdsen, J Webster Stayman
A task-driven imaging framework for prospective fluence field modulation (FFM) is developed in this paper. The design approach uses a system model that includes a parameterized FFM acquisition and model-based iterative reconstruction (MBIR) for image formation. Using prior anatomical knowledge (e.g. from a low-dose 3D scout image), accurate predictions of spatial resolution and noise as a function of FFM are integrated into a task-based objective function. Specifically, detectability index (d'), a common metric for task-based image quality assessment, is computed for a specific formulation of the imaging task...
July 2016: Conference Proceedings of International Conference on Image Formation in X-Ray Computed Tomography
https://www.readbyqxmd.com/read/28066030/sparse-exponential-family-principal-component-analysis
#18
Meng Lu, Jianhua Z Huang, Xiaoning Qian
We propose a Sparse exponential family Principal Component Analysis (SePCA) method suitable for any type of data following exponential family distributions, to achieve simultaneous dimension reduction and variable selection for better interpretation of the results. Because of the generality of exponential family distributions, the method can be applied to a wide range of applications, in particular when analyzing high dimensional next-generation sequencing data and genetic mutation data in genomics. The use of sparsity-inducing penalty helps produce sparse principal component loading vectors such that the principal components can focus on informative variables...
December 2016: Pattern Recognition
https://www.readbyqxmd.com/read/28065694/real-time-cardiac-magnetic-resonance-cine-imaging-with-sparse-sampling-and-iterative-reconstruction-for-left-ventricular-measures-comparison-with-gold-standard-segmented-steady-state-free-precession
#19
Gabriel C Camargo, Fernanda Erthal, Leticia Sabioni, Filipe Penna, Ralph Strecker, Michaela Schmidt, Michael O Zenge, Ronaldo de S L Lima, Ilan Gottlieb
BACKGROUND: Segmented cine imaging with a steady-state free-precession sequence (Cine-SSFP) is currently the gold standard technique for measuring ventricular volumes and mass, but due to multi breath-hold (BH) requirements, it is prone to misalignment of consecutive slices, time consuming and dependent on respiratory capacity. Real-time cine avoids those limitations, but poor spatial and temporal resolution of conventional sequences has prevented its routine application. We sought to examine the accuracy and feasibility of a newly developed real-time sequence with aggressive under-sampling of k-space using sparse sampling and iterative reconstruction (Cine-RT)...
January 6, 2017: Magnetic Resonance Imaging
https://www.readbyqxmd.com/read/28065638/iterative-metal-artefact-reduction-in-ct-can-dedicated-algorithms-improve-image-quality-after-spinal-instrumentation
#20
J Aissa, C Thomas, L M Sawicki, J Caspers, P Kröpil, G Antoch, J Boos
AIM: To investigate the value of dedicated computed tomography (CT) iterative metal artefact reduction (iMAR) algorithms in patients after spinal instrumentation. MATERIALS AND METHODS: Post-surgical spinal CT images of 24 patients performed between March 2015 and July 2016 were retrospectively included. Images were reconstructed with standard weighted filtered back projection (WFBP) and with two dedicated iMAR algorithms (iMAR-Algo1, adjusted to spinal instrumentations and iMAR-Algo2, adjusted to large metallic hip implants) using a medium smooth kernel (B30f) and a sharp kernel (B70f)...
January 5, 2017: Clinical Radiology
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