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MR Image Reconstruction

Yanjie Zhu, Yuanyuan Liu, Leslie Ying, Xi Peng, Yi-Xiang J Wang, Jing Yuan, Xin Liu, Dong Liang
Magnetic resonance (MR) parameter mapping is useful for many clinical applications. However, its practical utility is limited by the long scan time. To address this problem, this paper developed a novel image reconstruction method for fast MR parameter mapping. The proposed method (SCOPE) used a low-rank plus sparse model to reconstruct the parameter-weighted images from highly undersampled acquisitions. A signal compensation strategy was introduced to promote low rankness along the parametric direction and thus improve the reconstruction accuracy...
August 17, 2018: Physics in Medicine and Biology
Matteo Maspero, Mark H F Savenije, Anna M Dinkla, Peter R Seevinck, Martijn P W Intven, Ina M Juergenliemk-Schulz, Linda G W Kerkmeijer, Cornelis A T Van den Berg
To enable magnetic resonance (MR)-only radiotherapy and facilitate modelling of radiation attenuation in humans, synthetic-CT (sCT) images need to be generated. Considering the application of MR-guided radiotherapy and online adaptive replanning, sCT generation should occur within minutes. This work aims at assessing whether an existing deep learning network can rapidly generate sCT images to be used for accurate MR-based dose calculations in the entire pelvis.
 A study was conducted on data of 91 patients with prostate (59), rectal (18) and cervical (14) cancer who underwent external beam radiotherapy acquiring both CT and MRI for patients' simulation...
August 15, 2018: Physics in Medicine and Biology
Shekhar S Chandra, Gary Ruben, Jin Jin, Mingyan Li, Andrew Kingston, Imants Svalbe, Stuart Crozier
We propose a sparse imaging methodology called Chaotic Sensing (ChaoS) that enables the use of limited yet deterministic linear measurements through fractal sampling. A novel fractal in the discrete Fourier transform is introduced that always results in the artefacts being turbulent in nature. These chaotic artefacts have characteristics that are image independent, facilitating their removal through dampening (via image denoising) and obtaining the maximum likelihood solution. In contrast with existing methods, such as compressed sensing, the fractal sampling is based on digital periodic lines that form the basis of discrete projected views of the image without requiring additional transform domains...
August 10, 2018: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Efstratios Karavasilis, Foteini Christidi, Georgios Velonakis, Zoi Giavri, Nikolaos L Kelekis, Efstathios P Efstathopoulos, Ioannis Evdokimidis, Georges Dellatolas
BACKGROUND AND PURPOSE: The cerebellum has a pivotal role in regulating human behavior; yet whether this function is mediated only through contralateral cerebro-cerebellar pathways is under-investigated. Thus, we examined feed-backward and feed-forward ipsilateral and contralateral cerebro-cerebellar connections using a detereministic diffusion tensor imaging (DTI) algorithm, the robustness of which was also estimated using phantom DTI data. MATERIALS AND METHODS: Fifty-one healthy controls (22-60 years old; 15 males/36 females) were scanned in a 3 T MRI scanner with a 30-direction DTI sequence...
August 8, 2018: Journal of Neuroradiology. Journal de Neuroradiologie
Gastao Cruz, Torben Schneider, Tom Bruijnen, Andreia S Gaspar, René M Botnar, Claudia Prieto
OBJECT: To develop a novel approach for highly accelerated Magnetic Resonance Fingerprinting (MRF) acquisition. MATERIALS AND METHODS: The proposed method combines parallel imaging, soft-gating and key-hole approaches to highly accelerate MRF acquisition. Slowly varying flip angles (FA), commonly used during MRF acquisition, lead to a smooth change in the signal contrast of consecutive time-point images. This assumption enables sharing of high frequency data between different time-points, similar to what is done in some dynamic MR imaging methods such as key-hole...
2018: PloS One
Chieh Lin, Chih-Chieh Liu, Hsuan-Ming Huang
In this study, we present an image denoising method for diffusion-weighted magnetic resonance imaging (DW-MRI) data. Our aim is to improve the estimation of intravoxel incoherent motion (IVIM) parameters using denoised DW-MRI data. A general-threshold filtering (GTF) reconstruction via total variation minimization has been proposed to improve image quality in few-view computed tomography. Here, we applied the combination of GTF and total difference to image denoising. Voxel-wise IVIM analysis was performed using both real and simulated DW-MRI data...
August 9, 2018: Physics in Medicine and Biology
Xinhui Wang, Bao Yang, Matthew Paul Adams, Xiangzhen Gao, Nicolas A Karakatsanis, Jing Tang
Myocardial perfusion (MP) PET imaging plays an important role in risk assessment and stratification of patients with coronary artery disease. In this work, we developed an anatomy-assisted maximum a posteriori (MAP) reconstruction method incorporating a wavelet-based joint entropy (WJE) prior for MP PET imaging. Using the XCAT phantom, we first simulated three MP PET datasets, one with normal perfusion and the other two with non-transmural and transmural regionally reduced perfusion of the left ventricular myocardium...
August 8, 2018: Physics in Medicine and Biology
Sabine Meier, Joerg Seeburger, Michael A Borger
Mitral valve (MV) insufficiency, classified as primary and secondary mitral regurgitation (MR), is a common cause of morbidity and mortality. In industrialized countries, degenerative forms are the predominant cause of MR; however, an increasing number of patients present with secondary MR (Iung et al. EHJ 24:1231-1243, 2003). During the last decades, MV surgery experienced substantial advancements. Alain Carpentier pioneered the field of reconstructive valve surgery in the beginning of the 1970s and, since then, a plethora of innovations have led to today's landscape of MV surgery...
August 7, 2018: Current Treatment Options in Cardiovascular Medicine
Chen Qin, Joseph V Hajnal, Daniel Rueckert, Jo Schlemper, Jose Caballero, Anthony N Price
Accelerating the data acquisition of dynamic magnetic resonance imaging (MRI) leads to a challenging ill-posed inverse problem, which has received great interest from both the signal processing and machine learning communities over the last decades. The key ingredient to the problem is how to exploit the temporal correlations of the MR sequence to resolve aliasing artefacts. Traditionally, such observation led to a formulation of an optimisation problem, which was solved using iterative algorithms. Recently, however, deep learning based-approaches have gained significant popularity due to their ability to solve general inverse problems...
August 6, 2018: IEEE Transactions on Medical Imaging
Hiroaki Shimamoto, Tomomi Tsujimoto, Naoya Kakimoto, Minami Majima, Yuri Iwamoto, Yurie Senda, Shumei Murakami
PURPOSE: To compare a fat-suppressed T2-weighted periodically rotated overlapping parallel lines with enhanced reconstruction (T2W-PROPELLER) sequence with a fat-suppressed T2-weighted fast spin-echo (T2W-FSE) sequence in the oral and maxillofacial regions for the evaluation of the presence of motion artifacts caused by mandibular movements. METHODS: Fifty-six healthy adult volunteers were examined in a closed mouth position and then with three different rhythmical mandibular movements throughout MR scanning: open-close movement (movement 1), lateral movement (movement 2) and open-close and lateral movement (movement 3)...
August 2, 2018: Magnetic Resonance Imaging
Yan Tianfang, Xu Liang, Wei Yukui, Lin Qingtang, Jiao Liqun, Xu Geng
OBJECTIVES: To prospectively evaluate the diagnostic value of 3.0 T magnetic resonance three dimensional sampling perfection with application-optimized contrast using different flip angle evolution (3D-SPACE) in the detection of sinus wall invasion and sinus patency in para-sinus meningiomas. METHODS: In this study twenty-eight patients with suspected meningiomas adjacent to venous sinus underwent conventional MR imaging, CE-MRV and 3D-SPACE scans. We collected patient charts and surgical reports for demographics, histology and neurological performance pre- and postoperatively...
August 2, 2018: World Neurosurgery
Zhaolin Chen, Sharna D Jamadar, Shenpeng Li, Francesco Sforazzini, Jakub Baran, Nicholas Ferris, Nadim Jon Shah, Gary F Egan
Simultaneous Magnetic Resonance Imaging (MRI) and Positron Emission Tomography (PET) scanning is a recent major development in biomedical imaging. The full integration of the PET detector ring and electronics within the MR system has been a technologically challenging design to develop but provides capacity for simultaneous imaging and the potential for new diagnostic and research capability. This article reviews state-of-the-art MR-PET hardware and software, and discusses future developments focusing on neuroimaging methodologies for MR-PET scanning...
August 4, 2018: Human Brain Mapping
Edwin E G W Ter Voert, Urs J Muehlematter, Gaspar Delso, Daniele A Pizzuto, Julian Müller, Hannes W Nagel, Irene A Burger
BACKGROUND: In contrast to ordered subset expectation maximization (OSEM), block sequential regularized expectation maximization (BSREM) positron emission tomography (PET) reconstruction algorithms can run until full convergence while controlling image quality and noise. Recent studies with BSREM and 18 F-FDG PET reported higher signal-to-noise ratios and higher standardized uptake values (SUV). In this study, we investigate the optimal regularization parameter (β) for clinical 68 Ga-PSMA PET/MR reconstructions in the pelvic region applying time-of-flight (TOF) BSREM in comparison to TOF OSEM...
July 27, 2018: EJNMMI Research
Tessa van de Lindt, Jan-Jakob Sonke, Marlies Nowee, Edwin Jansen, Vivian van Pelt, Uulke van der Heide, Martin Fast
PURPOSE: Novel hybrid MR-LINAC devices provide MRI's superior soft-tissue contrast in the treatment room and thus have the potential to increase accuracy of liver stereotactic body radiation therapy (SBRT). Requirements for daily position verification using 4-dimensional MRI include tumor visibility and short acquisition-reconstruction time (preferably <5 min). The proposed method provides fast acquisition-reconstruction time and the flexibility to vary T1- and T2-weighting, using standard imaging sequences for straightforward implementation on an MR-LINAC...
May 19, 2018: International Journal of Radiation Oncology, Biology, Physics
Eduardo Coello, Ralph Noeske, Brian L Burns, Jeremy W Gordon, Angela Jakary, Bjoern Menze, Axel Haase, Peder E Z Larson, Yan Li, Rolf F Schulte
MR spectroscopic imaging (MRSI) at ultra-high field (≥7 T) benefits from improved sensitivity that allows the detection of low-concentration metabolites in the brain. However, optimized acquisition techniques are required to overcome inherent limitations of MRSI at ultra-high field. This work describes an optimized method for fast high-resolution 1 H-MRSI of the brain at 7 T. The proposed acquisition sequence combines precise volume localization using semi-localization by adiabatic selective refocusing, fast spatial encoding using high-bandwidth symmetric echo-planar spectroscopic imaging (EPSI), and robust water suppression with variable power and optimized relaxation delays...
July 27, 2018: NMR in Biomedicine
Morteza Mardani, Enhao Gong, Joseph Y Cheng, Shreyas S Vasanawala, Greg Zaharchuk, Lei Xing, John M Pauly
Undersampled magnetic resonance image (MRI) reconstruction is typically an ill-posed linear inverse task. The time and resource intensive computations require trade offs between accuracy and speed. In addition, state-of-the-art compressed sensing (CS) analytics are not cognizant of the image diagnostic quality. To address these challenges, we propose a novel CS framework that uses generative adversarial networks (GAN) to model the (low-dimensional) manifold of high-quality MR images. Leveraging a mixture of least-squares (LS) GANs and pixel-wise ℓ1/ℓ2 cost, a deep residual network with skip connections is trained as the generator that learns to remove the aliasing artifacts by projecting onto the image manifold...
July 23, 2018: IEEE Transactions on Medical Imaging
Lukas Filli, Andrea B Rosskopf, Reto Sutter, Sandro F Fucentese, Christian W A Pfirrmann
Purpose To determine the diagnostic performance of MRI for helping to predict posterolateral knee instability in patients with acute anterior cruciate ligament (ACL) tear. Materials and Methods This retrospective cohort study was performed in a consecutive series of 162 patients (mean age, 32.8 years ± 10.0 [standard deviation]; 95 men [mean age, 31.0 years ± 9.6] and 67 women [mean age, 35.4 years ± 10.0]) who underwent ACL reconstruction with (n = 19) or without (n = 143) concomitant posterolateral corner (PLC) reconstruction between June 2014 and February 2017...
July 24, 2018: Radiology
Carole Lazarus, Pierre Weiss, Alexandre Vignaud, Philippe Ciuciu
Magnetic Resonance Imaging (MRI) is one of the most dynamic and safe imaging modalities used in clinical routine today. Yet, one major limitation to this technique resides in its long acquisition times. Over the last decade, Compressed Sensing (CS) has been increasingly used to address this issue and offers to shorten MR scans by reconstructing images from undersampled Fourier data. Nevertheless, a quantitative guide on the degree of acceleration applicable to a given acquisition scenario is still lacking today, leading in practice to a trial-and-error approach in the selection of the appropriate undersampling factor...
July 21, 2018: Magnetic Resonance Imaging
Ana M Franceschi, Valentino Abballe, Roy A Raad, Aaron Nelson, Kimberly Jackson, James Babb, Thomas Vahle, Matthias Fenchel, Yiqiang Zhan, Gerardo Hermosillo Valadez, Timothy M Shepherd, Kent P Friedman
Fluorodeoxyglucose (FDG) positron emission tomography-magnetic resonance (PET/MR) is useful for the evaluation of cognitively-impaired patients. This study aims to assess two different attenuation correction (AC) methods (Dixon-MR and atlas-based) versus index-standard computed tomography (CT) AC for the visual interpretation of regional hypometabolism in patients with cognitive impairment. Two board-certified nuclear medicine physicians blindly scored brain region FDG hypometabolism as normal versus hypometabolic using two-dimensional (2D) and 3D FDG PET/MR images generated by MIM software...
July 2018: World Journal of Nuclear Medicine
Walter Jentzen, Jinda Phaosricharoen, Benedikt Gomez, Philipp Hetkamp, Vanessa Stebner, Ina Binse, Sonja Kinner, Ken Herrmann, Amir Sabet, James Nagarajah
BACKGROUND: In patients with differentiated thyroid cancer (DTC), serial 124 I PET/CT imaging is, for instance, used to assess the absorbed (radiation) dose to lesions. Frequently, the lesions are located in the neck and they are close to or surrounded by different tissue types. In contrast to PET/CT, MR-based attenuation correction in PET/MR may be therefore challenging in the neck region. The aim of this retrospective study was to assess the quantitative performance of 124 I PET/MRI of neck lesions by comparing the MR-based and CT-based 124 I activity concentrations (ACs)...
July 19, 2018: EJNMMI Physics
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