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iterative model reconstruction

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https://www.readbyqxmd.com/read/28527236/a-weighted-difference-of-l1-and-l2-on%C3%A2-the%C3%A2-gradient-minimization-based-on%C3%A2-alternating-direction-method-for%C3%A2-circular%C3%A2-computed-tomography
#1
Wanli Lu, Lei Li, Ailong Cai, Hanming Zhang, Linyuan Wang, Bin Yan
Iterative reconstruction algorithms for computed tomography (CT) through total variation (TV) regularization can provide accurate and stable reconstruction results. TV minimization is the L1-norm of gradient-magnitude images and can be regarded as a convex relaxation method to replace the L0 norm. In this study, a fast and efficient algorithm, which is named a weighted difference of L1 and L2 (L1 - αL2) on the gradient minimization, was proposed and investigated. The new algorithm provides a better description of sparsity for the optimization-based algorithms than TV minimization algorithms...
May 15, 2017: Journal of X-ray Science and Technology
https://www.readbyqxmd.com/read/28508476/magnetic-resonance-electrical-properties-tomography-for-small-anomalies-using-boundary-conditions-a-simulation-study
#2
Joonsung Lee, Narae Choi, Jin Keun Seo, Dong-Hyun Kim
PURPOSE: Magnetic Resonance Electrical Property Tomography (MREPT) is an emerging imaging modality using measured B1 maps from Magnetic Resonance Imaging (MRI) to measure a distribution of electric conductivity and permittivity of the subject at the Larmor frequency. Conventional MREPT approachesat single transmit channel system using the Helmholtz equation rely on an assumption that conductivity and permittivity of the subject are locally homogeneous. For small tissue structures and tissue boundaries, in which the assumption of locally homogeneous conductivity and permittivity does not hold, the reconstructed conductivity values deviated from the actual values, so called "Boundary Artifacts"...
May 16, 2017: Medical Physics
https://www.readbyqxmd.com/read/28505440/iterative-reconstruction-of-memory-kernels
#3
Gerhard Jung, Martin Hanke, Friederike Schmid
In recent years it has become increasingly popular to construct coarse-grained models with non-Markovian dynamics in order to account for an incomplete separation of time scales. One challenge of a systematic coarse-graining procedure is the extraction of the dynamical properties, namely the memory kernel, from equilibrium all-atom simulations. In this paper we propose an iterative method for memory reconstruction from dynamical correlation functions. Compared to previously proposed non-iterative techniques, it ensures by construction that the target correlation functions of the original fine-grained systems are reproduced accurately by the coarse-grained system, regardless of time step and discretization effects...
May 15, 2017: Journal of Chemical Theory and Computation
https://www.readbyqxmd.com/read/28504935/efficient-three-dimensional-model-based-reconstruction-scheme-for-arbitrary-optoacoustic-acquisition-geometries
#4
Lu Ding, X Luis Dean Ben, Daniel Razansky
Optimal optoacoustic tomographic sampling is often hindered by the frequency-dependent directivity of ultrasound sensors, which can only be accounted for with an accurate three-dimensional (3D) model. Herein, we introduce a 3D modelbased reconstruction method applicable to optoacoustic imaging systems employing detection elements with arbitrary size and shape. The computational complexity and memory requirements are mitigated by introducing an efficient graphics processing unit (GPU)-based implementation of the iterative inversion...
May 12, 2017: IEEE Transactions on Medical Imaging
https://www.readbyqxmd.com/read/28504644/direct-reconstruction-of-parametric-images-for-brain-pet-with-event-by-event-motion-correction-evaluation-in-two-tracers-across-count-levels
#5
Mary Germino, Jean-Dominique Gallezot, Jianhua Yan, Richard Carson
Parametric images for dynamic positron emission tomography (PET) are typically generated by an indirect method, i.e., reconstructing a time series of emission images, then fitting a kinetic model to each voxel time activity curve. Alternatively, "direct reconstruction," incorporates the kinetic model into the reconstruction algorithm itself, directly producing parametric images from projection data. Direct reconstruction has been shown to achieve parametric images with lower standard error than the indirect method...
May 15, 2017: Physics in Medicine and Biology
https://www.readbyqxmd.com/read/28491908/lack-of-agreement-between-radiologists-implications-for-image-based-model-observers
#6
Juhun Lee, Robert M Nishikawa, Ingrid Reiser, Margarita L Zuley, John M Boone
We tested the agreement of radiologists' rankings of different reconstructions of breast computed tomography images based on their diagnostic (classification) performance and on their subjective image quality assessments. We used 102 pathology proven cases (62 malignant, 40 benign), and an iterative image reconstruction (IIR) algorithm to obtain 24 reconstructions per case with different image appearances. Using image feature analysis, we selected 3 IIRs and 1 clinical reconstruction and 50 lesions. The reconstructions produced a range of image quality from smooth/low-noise to sharp/high-noise, which had a range in classifier performance corresponding to AUCs of 0...
April 2017: Journal of Medical Imaging
https://www.readbyqxmd.com/read/28489530/real-time-3d-microwave-monitoring-of-interstitial-thermal-therapy
#7
Guanbo Chen, John Stang, Mark Haynes, Eric Leuthardt, Mahta Moghaddam
We report a method for real-time 3D monitoring of thermal therapy through the use of non-contact microwave imaging. This method is predicated on using microwaves to image changes in the dielectric properties of tissue with changing temperature. Instead of the precomputed linear Born approximation that was used in prior work to speed up the frameto- frame inversions, here we use the nonlinear Distorted Born Iterative Method (DBIM) to solve the electric volume integral equation to image the temperature change...
May 8, 2017: IEEE Transactions on Bio-medical Engineering
https://www.readbyqxmd.com/read/28463542/ultra-low-dose-fetal-ct-with-model-based-iterative-reconstruction-a-prospective-pilot-study
#8
Rumi Imai, Osamu Miyazaki, Tetsuya Horiuchi, Keisuke Asano, Gen Nishimura, Haruhiko Sago, Shunsuke Nosaka
OBJECTIVE: Prenatal diagnosis of skeletal dysplasia by means of 3D skeletal CT examination is highly accurate. However, it carries a risk of fetal exposure to radiation. Model-based iterative reconstruction (MBIR) technology can reduce radiation exposure; however, to our knowledge, the lower limit of an optimal dose is currently unknown. The objectives of this study are to establish ultra-low-dose fetal CT as a method for prenatal diagnosis of skeletal dysplasia and to evaluate the appropriate radiation dose for ultra-low-dose fetal CT...
May 2, 2017: AJR. American Journal of Roentgenology
https://www.readbyqxmd.com/read/28459684/towards-robust-and-accurate-multi-view-and-partially-occluded-face-alignment
#9
Junliang Xing, Zhiheng Niu, Junshi Huang, Weiming Hu, Xi Zhou, Shuicheng Yan
Face alignment acts as an important task in computer vision. Regression-based methods currently dominate the approach to solving this problem, which generally employ a series of mapping functions from the face appearance to iteratively update the face shape hypothesis. One keypoint here is thus how to perform the regression procedure. In this work, we formulate this regression procedure as a sparse coding problem. We learn two relational dictionaries, one for the face appearance and the other one for the face shape, with coupled reconstruction coefficient to capture their underlying relationships...
April 25, 2017: IEEE Transactions on Pattern Analysis and Machine Intelligence
https://www.readbyqxmd.com/read/28456252/edge-preserving-reconstruction-from-sparse-projections-of-limited-angle-computed-tomography-using-%C3%A2-0-regularized-gradient-prior
#10
Wei Yu, Chengxiang Wang, Min Huang
Accurate images reconstructed from limited computed tomography (CT) data are desired when reducing the X-ray radiation exposure imposed on patients. The total variation (TV), known as the l1-norm of the image gradient magnitudes, is popular in CT reconstruction from incomplete projection data. However, as the projection data collected are from a sparse-view of the limited scanning angular range, the results reconstructed by a TV-based method suffer from blocky artifact and gradual changed artifacts near the edges, which in turn make the reconstruction images degraded...
April 2017: Review of Scientific Instruments
https://www.readbyqxmd.com/read/28448422/iterative-reconstruction-designed-for-brain-ct-a-correlative-study-with-filtered-back-projection-for-the-diagnosis-of-acute-ischemic-stroke
#11
Yuji Iyama, Takeshi Nakaura, Seitaro Oda, Masafumi Kidoh, Daisuke Utsunomiya, Morikatsu Yoshida, Hideaki Yuki, Kenichiro Hirata, Yoshinori Funama, Kazunori Harada, Kazuo Awai, Toshinori Hirai, Yasuyuki Yamashita
OBJECTIVES: The objective of this study is to evaluate the usefulness of iterative model reconstruction designed for brain computed tomography (CT) (IMR-Neuro) for the diagnosis of acute ischemic stroke. METHODS: This retrospective study included 20 patients with acute middle cerebral artery infarction who have undergone brain CT and 20 nonstroke patients (control). We reconstructed axial images with filtered back projection (FBP) and IMR-Neuro (slice thickness, 1 and 5 mm)...
April 26, 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28448417/electrocardiography-gated-computed-tomography-of-the-bronchial-arteries-with-iterative-image-reconstruction-clinical-evaluation-and-image-quality
#12
Qiangqiang Gang, Jun Xu, Junling Wang, Peng Hao, Yikai Xu
BACKGROUND: The aim of this study was to apply electrocardiography (ECG)-gated prospective-triggered multidetector row computed tomography angiography with iterative model reconstruction (IMR) to optimize imaging of the bronchial arteries in patients with the chief complaint of hemoptysis. METHODS: This was a prospective observational study. Between August 2015 and June 2016, we enrolled 31 consecutive patients with the chief complaint of hemoptysis who were scheduled to undergo computed tomography of the bronchial artery...
April 26, 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28448403/usefulness-of-a-low-tube-voltage-knowledge-based-iterative-model-reconstruction-algorithm-for-computed-tomography-venography
#13
Yuji Iyama, Takeshi Nakaura, Ayumi Iyama, Masafumi Kidoh, Seitaro Oda, Shinichi Tokuyasu, Yasuyuki Yamashita
OBJECTIVES: The objective of this study was to evaluate the use of 80-kVp scans with knowledge-based iterative model reconstruction (IMR) for computed tomography venography (CTV). METHODS: This prospective study received institutional review board approval; a previous informed consent was obtained from all participants. We enrolled 30 patients with suspected deep venous thrombosis or pulmonary embolism who were to undergo 80-kVp CTV studies. The images were reconstructed with filtered back projection (FBP), hybrid iterative reconstruction (HIR), and IMR...
April 26, 2017: Journal of Computer Assisted Tomography
https://www.readbyqxmd.com/read/28445243/harmonizing-standardized-uptake-value-recovery-between-two-pet-ct-systems-from-different-manufacturers-when-using-resolution-modelling-and-time-of-flight
#14
Ian S Armstrong, Katharine E Thomson, Lisa M Rowley, Daniel R McGowan
PET iterative reconstruction algorithms with resolution modelling (RM) can be used to improve spatial resolution in the images. However, RM has a significant impact on quantification, which raises issues for harmonization across multicentre networks or collaborations. This investigation compared quantification from two modern time-of-flight (TOF) PET/CT systems from different manufacturers with RM with the intention to harmonize recovery. Images of a National Electrical Manufacturers Association image quality phantom with a sphere-to-background concentration ratio of 4 : 1 were acquired on a GE Discovery 710 and a Siemens Biograph mCT and reconstructed with RM and TOF...
April 25, 2017: Nuclear Medicine Communications
https://www.readbyqxmd.com/read/28444799/pixel-wise-estimation-of-noise-statistics-on-iterative-ct-reconstruction-from-a-single-scan
#15
Tonghe Wang, Lei Zhu
PURPOSE: As iterative CT reconstruction continues to advance, the spatial distribution of noise standard deviation (STD) and accurate noise power spectrum (NPS) on the reconstructed CT images become important for method evaluation as well as optimization of algorithm parameters. Using a single CT scan, we propose a practical method for pixel-wise calculation of noise statistics on an iteratively reconstructed CT image, which enables accurate calculation of noise STD for each pixel and NPS...
April 26, 2017: Medical Physics
https://www.readbyqxmd.com/read/28437900/model-and-reconstruction-of-a-k-edge-contrast-agent-distribution-with-an-x-ray-photon-counting-detector
#16
Bo Meng, Wenxiang Cong, Yan Xi, Bruno De Man, Jian Yang, Ge Wang
Contrast-enhanced computed tomography (CECT) helps enhance the visibility for tumor imaging. When a high-Z contrast agent interacts with X-rays across its K-edge, X-ray photoelectric absorption would experience a sudden increment, resulting in a significant difference of the X-ray transmission intensity between the left and right energy windows of the K-edge. Using photon-counting detectors, the X-ray intensity data in the left and right windows of the K-edge can be measured simultaneously. The differential information of the two kinds of intensity data reflects the contrast-agent concentration distribution...
April 17, 2017: Optics Express
https://www.readbyqxmd.com/read/28437735/detective-quantum-efficiency-dqe-in-pet-scanners-a-simulation-study
#17
George E Karpetas, Christos M Michail, George P Fountos, Nektarios I Kalyvas, Ioannis G Valais, Ioannis S Kandarakis, George S Panayiotakis
The aim of the present study is to introduce the detective quantum efficiency (DQE) for the image quality assessment of positron emission tomography (PET) scanners. For this purpose, a thin layer chromatography (TLC) plane source was simulated using a previously validated, scanner and source geometry, Monte Carlo (MC) model. The model was developed with the Geant4 application for tomographic emission (GATE) MC package and reconstructed images obtained with the software for tomographic image reconstruction (STIR), with cluster computing...
April 12, 2017: Applied Radiation and Isotopes
https://www.readbyqxmd.com/read/28432820/the-impact-of-small-motion-on-the-visualization-of-coronary-vessels-and-lesions-in-cardiac-ct-a-simulation-study
#18
Francisco Contijoch, J Webster Stayman, Elliot R McVeigh
PURPOSE: Coronary x-ray computed tomography angiography (CCTA) is used to non-invasively assess coronary artery geometry and has, combined with computational modeling, demonstrated the potential to identify physiologically significant lesions. These measurements require robust and accurate coronary imaging and delineation of vessels in the presence of small motion. This simulation study characterizes the impact of small, uncorrected vessel drifts during data acquisition on the assessment of vessel intensity, diameter, and shape...
April 22, 2017: Medical Physics
https://www.readbyqxmd.com/read/28429371/design-of-a-short-non-uniform-acquisition-protocol-for-quantitative-analysis-in-dynamic-cardiac-spect-imaging-a-retrospective-123-i-mibg-animal-study
#19
Yunlong Zan, Yong Long, Kewei Chen, Biao Li, Qiu Huang, Grant T Gullberg
PURPOSE: Our previous works have found that quantitative analysis of (123) I-MIBG kinetics in the heart with dynamic single-photon emission computed tomography (SPECT) offers the potential to quantify the innervation integrity at an early stage of left ventricular hypertrophy. However, conventional protocols involving a long acquisition time for dynamic imaging reduce the animal survival rate and thus make longitudinal analysis difficult. The goal of this work was to develop a procedure to reduce the total acquisition time by selecting non-uniform acquisition times for projection views while maintaining the accuracy and precision of estimated physiologic parameters...
April 21, 2017: Medical Physics
https://www.readbyqxmd.com/read/28417170/reduced-dose-ct-with-model-based-iterative-reconstruction-compared-to-standard-dose-ct-of-the-chest-abdomen-and-pelvis-in-oncology-patients-intra-individual-comparison-study-on-image-quality-and-lesion-conspicuity
#20
Linda Nayeli Morimoto, Aya Kamaya, Isabelle Boulay-Coletta, Dominik Fleischmann, Lior Molvin, Lu Tian, George Fisher, Jia Wang, Jürgen K Willmann
PURPOSE: To compare image quality and lesion conspicuity of reduced dose (RD) CT with model-based iterative reconstruction (MBIR) compared to standard dose (SD) CT in patients undergoing oncological follow-up imaging. METHODS: Forty-four cancer patients who had a staging SD CT within 12 months were prospectively included to undergo a weight-based RD CT with MBIR. Radiation dose was recorded and tissue attenuation and image noise of four tissue types were measured...
April 17, 2017: Abdominal Radiology
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