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Jizhong Duan, Zhongwen Bao, Yu Liu
Parallel Magnetic Resonance (MR) imaging is a well-established acceleration technique based on the spatial sensitivities of array receivers. Eigenvector-based SPIRiT (ESPIRiT) is a new parallel MR imaging reconstruction method that combines the advantages of the SENSE and GRAPPA methods. It estimates multiple sets of the sensitivity maps from the calibration matrix that is constructed from the auto-calibration data. To improve the quality of the reconstructed image, we introduced the Total Variation (TV) and ℓp pseudo-norm Joint TV (ℓp JTV) regularization terms to the ESPIRiT model for parallel MR imaging reconstruction, which were solved by using the Operator Splitting (OS) method...
January 25, 2019: Magnetic Resonance Imaging
Qingyong Zhu, Wei Wang, Jing Cheng, Xi Peng
PURPOSE: To propose and evaluate a new calibrationless parallel imaging method aimed at further improving the reconstruction accuracy of the accelerated multi-channel MR images. METHOD: We introduce a new calibrationless parallel imaging method. On top of exploiting joint sparsity cross channels of the target image to be reconstructed, it incorporates similar priors on the grey-level intensity and edge orientation, which both come from a high-spatial resolution reference image that can be easily obtained in many clinical MRI scenarios...
December 28, 2018: Magnetic Resonance Imaging
Sebastian Rosenzweig, H Christian M Holme, Martin Uecker
PURPOSE: To develop a simple and robust tool for the estimation of gradient delays from highly undersampled radial k-space data. THEORY: In radial imaging gradient delays induce parallel and orthogonal trajectory shifts, which can be described using an ellipse model. The intersection points of the radial spokes, which can be estimated by spoke-by-spoke comparison of k-space samples, distinctly determine the parameters of the ellipse. Using the proposed method (RING), these parameters can be obtained using a least-squares fit and utilized for the correction of gradient delays...
November 4, 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Zhihua Zhu, Zhihe Chen, Xiaohong Chen, Guo Yu
This study represents an approach to assess the hydrologic effectiveness of low impact development (LID) practices based on the expected runoff process with different objectives and land utilization. The proposed approach is to simulate runoff hydrograph rather than several indices (e.g., runoff initiation, peak flow, and runoff volume) to avoid the uncertainties under a certain rainfall scenario. A rainfall-runoff model of a residential district in China, constructed based on the stormwater management model (SWMM), is auto-calibrated (validated) based on 12 (25) observed rainfall and runoff events using model-independent parameter estimation (PEST)...
October 26, 2018: Journal of Environmental Management
Philipp Kurth, Vanessa Lange, Christian Siegl, Marc Stamminger, Frank Bauer
The quality of every dynamic multi-projection mapping system is limited by the quality of the projector to tracking device calibration. Common problems with poor calibration result in noticeable artifacts for the user, such as ghosting and seams. In this work we introduce a new, fully automated calibration algorithm that is tailored to reduce these artifacts, based on consumer-grade hardware. We achieve this goal by repurposing a structured-light scanning setup. A structured-light scanner can generate 3D geometry based on a known intrinsic and extrinsic calibration of its components (projector and RGB camera)...
November 2018: IEEE Transactions on Visualization and Computer Graphics
S Maur, D Stsepankou, J Hesser
The image quality of dental cone-beam computed tomography (CBCT) is limited by the accuracy of device calibration. Inaccurate calibration introduces errors in the reconstruction process, which may lead to severe artifacts in the reconstructed volume. Patient motion during scan acquisition induces similar effects. This paper introduces a novel auto-calibration approach calculating geometrical projection parameters from unknown patient geometry. We formulate consistency conditions linking the information of consecutive projection images and a regularization technique to prevent overall distortions...
October 29, 2018: Physics in Medicine and Biology
Lin Xu, Qian Zheng, Tao Jiang
Generalized Auto-calibrating Partially Parallel Acquisitions (GRAPPA) has been widely used to reduce imaging time in Magnetic Resonance Imaging. GRAPPA synthesizes missing data by using a linear interpolation of neighboring measured data over all coils, thus accuracy of the interpolation weights fitting to the auto-calibrating signal data is crucial for the GRAPPA reconstruction. Conventional GRAPPA algorithms fitting the interpolation weights with a least squares solution are sensitive to interpolation window size...
October 10, 2018: Scientific Reports
Jingyuan Lyu, Ukash Nakarmi, Dong Liang, Jinhua Sheng, Leslie Ying
The conventional calibration-based parallel imaging method assumes a linear relationship between the acquired multi-channel k-space data and the unacquired missing data, where the linear coefficients are estimated using some auto-calibration data. In this work, we first analyze the model errors in the conventional calibration-based methods and demonstrate the nonlinear relationship. Then a much more general nonlinear framework is proposed for auto-calibrated parallel imaging. In this framework, kernel tricks are employed to represent the general nonlinear relationship between acquired and unacquired k-space data without increasing the computational complexity...
August 7, 2018: IEEE Transactions on Medical Imaging
XueJun Jin, Jinwoo Jung, Seong Young Ko, Eunpyo Choi, Jong-Oh Park, Chang-Sei Kim
A cable-driven parallel robot has benefits of wide workspace, high payload, and high dynamic response owing to its light cable actuator utilization. For wide workspace applications, in particular, the body frame becomes large to cover the wide workspace that causes robot kinematic errors resulting from geometric uncertainty. However, appropriate sensors as well as inexpensive and easy calibration methods to measure the actual robot kinematic parameters are not currently available. Hence, we present a calibration sensor device and an auto-calibration methodology for the over-constrained cable-driven parallel robots using one-dimension laser distance sensors attached to the robot end-effector, to overcome the robot geometric uncertainty and to implement precise robot control...
July 23, 2018: Sensors
Dixys L Hernández-Rojas, Tiago M Fernández-Caramés, Paula Fraga-Lamas, Carlos J Escudero
This article presents a Virtual Transducer Electronic Data Sheet (VTEDS)-based framework for the development of intelligent sensor nodes with plug-and-play capabilities in order to contribute to the evolution of the Internet of Things (IoT) toward the Web of Things (WoT). It makes use of new lightweight protocols that allow sensors to self-describe, auto-calibrate, and auto-register. Such protocols enable the development of novel IoT solutions while guaranteeing low latency, low power consumption, and the required Quality of Service (QoS)...
June 27, 2018: Sensors
Hossam A Shaltout, Sung W Lee, Catherine L Tegeler, Joshua R Hirsch, Sean L Simpson, Lee Gerdes, Charles H Tegeler
Background: Heart rate variability (HRV) is an indicator of dynamic adaptability of the autonomic nervous system. Few interventions target upstream, cerebral cortex components of the heart-brain system for autonomic management. We report changes in HRV and baroreflex sensitivity (BRS), associated with use of a noninvasive, closed-loop, allostatic, computer-guided, acoustic stimulation neurotechnology. Methods: Over 5 years, 220 subjects with heterogeneous neurological, cardiovascular, and psychophysiological conditions consecutively enrolled in a naturalistic, single-arm study exploring clinical effects associated with use of the neurotechnology...
2018: Frontiers in Public Health
Timothy McGrath, Richard Fineman, Leia Stirling
Inertial measurement units (IMUs) have been demonstrated to reliably measure human joint angles—an essential quantity in the study of biomechanics. However, most previous literature proposed IMU-based joint angle measurement systems that required manual alignment or prescribed calibration motions. This paper presents a simple, physically-intuitive method for IMU-based measurement of the knee flexion/extension angle in gait without requiring alignment or discrete calibration, based on computationally-efficient and easy-to-implement Principle Component Analysis (PCA)...
June 8, 2018: Sensors
Carlos Cambra, Sandra Sendra, Jaime Lloret, Raquel Lacuesta
Improving the sustainability in agriculture is nowadays an important challenge. The automation of irrigation processes via low-cost sensors can to spread technological advances in a sector very influenced by economical costs. This article presents an auto-calibrated pH sensor able to detect and adjust the imbalances in the pH levels of the nutrient solution used in hydroponic agriculture. The sensor is composed by a pH probe and a set of micropumps that sequentially pour the different liquid solutions to maintain the sensor calibration and the water samples from the channels that contain the nutrient solution...
April 25, 2018: Sensors
Grégoire Weil, Cyrus Motamed, Alexandre Eghiaian, Xavier Monnet, Stéphanie Suria
OBJECTIVE: To compare cardiac index (CI) between Proaqt/PulsioFlex® and oesophageal Doppler (OD) and the ability of the PulsioFlex® to track CI changes induced by fluid challenge and secondly to assess the impact of the time interval between two auto-calibrations of PulsioFlex® on the accuracy of the measured CI. METHODS: In a single hospital, 49 intermediate-risk oncologic abdominal surgery patients were included in an observational study. We measured the cardiac Index (CI) provided by OD and by the Proaqt/PulsioFlex® before and after internal calibration, which were performed randomly at specific intervals after the initial one (30, 60, 90 and 120min)...
April 18, 2018: Anaesthesia, Critical Care & Pain Medicine
Nicolas Moser, Jesus Rodriguez-Manzano, Tor Sverre Lande, Pantelis Georgiou
This paper presents a novel CMOS-based system-on-chip with a 78 56 ion-sensitive field-effect transistor array using in-pixel quantization and compensation of sensor nonidealities. The pixel integrates sensing circuitry and memory cells to encode the ion concentration in time and store a calibration value per pixel. Temperature sensing pixels spread throughout the array allow temperature monitoring during the reaction. We describe the integration of the array as part of a lab-on-chip cartridge that plugs into a motherboard for power management, biasing, data acquisition, and temperature regulation...
April 2018: IEEE Transactions on Biomedical Circuits and Systems
Wenwen Jiang, Peder E Z Larson, Michael Lustig
PURPOSE: To correct gradient timing delays in non-Cartesian MRI while simultaneously recovering corruption-free auto-calibration data for parallel imaging, without additional calibration scans. METHODS: The calibration matrix constructed from multi-channel k-space data should be inherently low-rank. This property is used to construct reconstruction kernels or sensitivity maps. Delays between the gradient hardware across different axes and RF receive chain, which are relatively benign in Cartesian MRI (excluding EPI), lead to trajectory deviations and hence data inconsistencies for non-Cartesian trajectories...
November 2018: Magnetic Resonance in Medicine: Official Journal of the Society of Magnetic Resonance in Medicine
Catherine L Tegeler, Lee Gerdes, Hossam A Shaltout, Jared F Cook, Sean L Simpson, Sung W Lee, Charles H Tegeler
BACKGROUND: Military-related post-traumatic stress (PTS) is associated with numerous symptom clusters and diminished autonomic cardiovascular regulation. High-resolution, relational, resonance-based, electroencephalic mirroring (HIRREM®) is a noninvasive, closed-loop, allostatic, acoustic stimulation neurotechnology that produces real-time translation of dominant brain frequencies into audible tones of variable pitch and timing to support the auto-calibration of neural oscillations. We report clinical, autonomic, and functional effects after the use of HIRREM® for symptoms of military-related PTS...
December 22, 2017: Military Medical Research
Seyed Mohsen Seyed Moosavi, Bijan Moaveni, Behzad Moshiri, Mohammad Reza Arvan
The present study designed skewed redundant accelerometers for a Measurement While Drilling (MWD) tool and executed auto-calibration, fault diagnosis and isolation of accelerometers in this tool. The optimal structure includes four accelerometers was selected and designed precisely in accordance with the physical shape of the existing MWD tool. A new four-accelerometer structure was designed, implemented and installed on the current system, replacing the conventional orthogonal structure. Auto-calibration operation of skewed redundant accelerometers and all combinations of three accelerometers have been done...
February 27, 2018: Sensors
Jeremy W Gordon, Rie B Hansen, Peter J Shin, Yesu Feng, Daniel B Vigneron, Peder E Z Larson
With the translation of metabolic MRI with hyperpolarized 13 C agents into the clinic, imaging approaches will require large volumetric FOVs to support clinical applications. Parallel imaging techniques will be crucial to increasing volumetric scan coverage while minimizing RF requirements and temporal resolution. Calibrationless parallel imaging approaches are well-suited for this application because they eliminate the need to acquire coil profile maps or auto-calibration data. In this work, we explored the utility of a calibrationless parallel imaging method (SAKE) and corresponding sampling strategies to accelerate and undersample hyperpolarized 13 C data using 3D blipped EPI acquisitions and multichannel receive coils, and demonstrated its application in a human study of [1-13 C]pyruvate metabolism...
April 2018: Journal of Magnetic Resonance
Sebastian Roth, Henrik Fox, Uwe Fuchs, Uwe Schulz, Angelika Costard-Jäckle, Jan F Gummert, Dieter Horstkotte, Olaf Oldenburg, Thomas Bitter
BACKGROUND: Determination of cardiac output (CO) is essential in diagnosis and management of heart failure (HF). The gold standard to obtain CO is invasive assessment via thermodilution (TD). Noninvasive pulse contour analysis (NPCA) is supposed as a new method of CO determination. However, a validation of this method in HF is pending and performed in the present study. METHODS: Patients with chronic-stable HF and reduced left ventricular ejection fraction (LVEF ≤ 45%; HF-REF) underwent right heart catheterization including TD...
May 2018: Clinical Research in Cardiology: Official Journal of the German Cardiac Society
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