1
|
Wang H, Liang D, Su S, King KF, Chang Y, Liu X, Zheng H, Ying L. Improved gradient-echo 3D magnetic resonance imaging using compressed sensing and Toeplitz encoding with phase-scrambled RF excitation. Med Phys 2020; 47:1579-1589. [PMID: 31872450 DOI: 10.1002/mp.13987] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 10/28/2019] [Accepted: 12/01/2019] [Indexed: 01/17/2023] Open
Abstract
PURPOSE To develop a novel three-dimensional (3D) hybrid-encoding framework using compressed sensing (CS) and Toeplitz encoding with variable phase-scrambled radio-frequency (RF) excitation, which has the following advantages: low power deposition of RF pulses, reduction of the signal dynamic range, no additional hardware requirement, and signal-to-noise ratio (SNR) improvement. METHODS In light of the actual imaging framework of magnetic resonance imaging (MRI) scanners, we applied specially tailored RF pulses with phase-scrambled RF excitation to implement a 3D hybrid Fourier-Toeplitz encoding method based on 3D gradient-recalled echo pulse (GRASS) sequence. This method exploits Toeplitz encoding along the phase encoding direction, while keeping Fourier encoding along the readout and slice encoding directions. Phantom experiments were conducted to optimize the amplitude of specially tailored RF pulses in the 3D GRASS sequence. In vivo experiments were conducted to validate the feasibility of the proposed method, and simulations were conducted to compare the 3D hybrid-encoding method with Fourier encoding and other non-Fourier encoding methods. RESULTS An optimized low RF amplitude was obtained in the phantom experiments. Using the optimized specially tailored RF pulses, both the watermelon and knee experiments demonstrated that the proposed method was able to preserve more image details than the conventional 3D Fourier-encoded methods at acceleration factors of 3.1 and 2.0. Additionally, SNR was improved because of no additional gradients and 3D volume encoding, when compared with single-slice scanning without 3D encoding. Simulation results demonstrated that the proposed scheme was superior to the conventional Fourier encoding method, and obtained comparative performance with other non-Fourier encoding methods in preserving details. CONCLUSIONS We developed a practical hybrid-encoding method for 3D MRI with specially tailored RF pulses of phase-scrambled RF excitation. The proposed method improves image SNR and detail preservation compared with the conventional Fourier encoding methods. Furthermore, our proposed method exhibits superior performance in terms of detail preservation, compared with the conventional Fourier encoding method.
Collapse
Affiliation(s)
- Haifeng Wang
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China.,Department of Electrical Engineering and Biomedical Engineering, University at Buffalo, The State University of New York (SUNY), Buffalo, NY, USA
| | - Dong Liang
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Shi Su
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Kevin F King
- Global Applied Science Lab, GE Healthcare, Waukesha, WI, USA
| | - Yuchou Chang
- Department of Computer Science and Engineering Technology, University of Houston-Downtown, Houston, TX, USA
| | - Xin Liu
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Hairong Zheng
- Paul C. Lauterbur Research Centre for Biomedical Imaging, Shenzhen Institutes of Advanced Technology, Chinese Academy of Sciences, Shenzhen, Guangdong, China
| | - Leslie Ying
- Department of Electrical Engineering and Biomedical Engineering, University at Buffalo, The State University of New York (SUNY), Buffalo, NY, USA
| |
Collapse
|
2
|
Emetere M, Falade A. Loss Path Influence on the MRI Radio Frequency Pulse Sequence: A Theoretical Evidence. Open Access Maced J Med Sci 2019; 7:2715-2722. [PMID: 31844426 PMCID: PMC6901837 DOI: 10.3889/oamjms.2019.728] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2019] [Revised: 07/23/2019] [Accepted: 07/24/2019] [Indexed: 11/15/2022] Open
Abstract
The RF pulse is initiated from either the loop or loopless MRI antenna. It has shown an increased advancement in recent times. Somehow, the concept has proven successful in the MR imaging procedure. Using the fundamental theories of the MRI concept, mathematical experimentation was carried out analytically to investigate the Loss Path Concept (LPC). The LPC was proposed to be one of the defects responsible for poor/blurred medical imaging of certain parts of the body. The LPC results obtain in this mathematical experimentation was found to be -56 dB and 6.7 dB. Theoretically, the LPC can be resolved mathematically by incorporating the molecular boundaries of the tissues. Practically, LPC can be resolved by introducing a detachable RF strip detector to synchronise-particles across different molecular boundaries and prevent patients from excess exposure to RF radiation.
Collapse
Affiliation(s)
- Moses Emetere
- Covenant University, Ota, Nigeria
- Department of Mechanical Engineering Science, University of Johannesburg, Johannesburg, South Africa
| | - A Falade
- Covenant University, Ota, Nigeria
| |
Collapse
|
3
|
Shimron E, Webb AG, Azhari H. CORE-PI: Non-iterative convolution-based reconstruction for parallel MRI in the wavelet domain. Med Phys 2018; 46:199-214. [DOI: 10.1002/mp.13260] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2018] [Revised: 09/17/2018] [Accepted: 10/09/2018] [Indexed: 01/08/2023] Open
Affiliation(s)
- Efrat Shimron
- Department of Biomedical Engineering; Technion - Israel Institute of Technology; Haifa 3200003 Israel
| | - Andrew G. Webb
- C.J. Gorter Center for High Field MRI; Department of Radiology; Leiden University Medical Center; Albinusdreef 2 2333 ZA Leiden The Netherlands
| | - Haim Azhari
- Department of Biomedical Engineering; Technion - Israel Institute of Technology; Haifa 3200003 Israel
| |
Collapse
|
4
|
Portakal ZG, Shermer S, Jenkins C, Spezi E, Perrett T, Tuncel N, Phillips J. Design and characterization of tissue-mimicking gel phantoms for diffusion kurtosis imaging. Med Phys 2018; 45:2476-2485. [PMID: 29635795 DOI: 10.1002/mp.12907] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 03/05/2018] [Accepted: 03/05/2018] [Indexed: 12/22/2022] Open
Abstract
PURPOSE The aim of this work was to create tissue-mimicking gel phantoms appropriate for diffusion kurtosis imaging (DKI) for quality assurance, protocol optimization, and sequence development. METHODS A range of agar, agarose, and polyvinyl alcohol phantoms with concentrations ranging from 1.0% to 3.5%, 0.5% to 3.0%, and 10% to 20%, respectively, and up to 3 g of glass microspheres per 100 ml were created. Diffusion coefficients, excess kurtosis values, and relaxation rates were experimentally determined. RESULTS The kurtosis values for the plain gels ranged from 0.05 with 95% confidence interval (CI) of (0.029,0.071) to 0.216(0.185,0.246), well below the kurtosis values reported in the literature for various tissues. The addition of glass microspheres increased the kurtosis of the gels with values up to 0.523(0.465,0.581) observed for gels with the highest concentration of microspheres. Repeat scans of some of the gels after more than 6 months of storage at room temperature indicate changes in the diffusion parameters of less than 10%. The addition of the glass microspheres reduces the apparent diffusion coefficients (ADCs) and increases the longitudinal and transverse relaxation rates, but the values remain comparable to those for plain gels and tissue, with ADCs observed ranging from 818(585,1053) × 10-6 mm2 /s to 2257(2118,2296) × 10-6 mm2 /s, R1 values ranging from 0.34(0.32,0.35) 1/s to 0.51(0.50,0.52) 1/s, and R2 values ranging from 9.69(9.34,10.04) 1/s to 33.07(27.10, 39.04) 1/s. CONCLUSIONS Glass microspheres can be used to effectively modify diffusion properties of gel phantoms and achieve a range of kurtosis values comparable to those reported for a variety of tissues.
Collapse
Affiliation(s)
- Ziyafer Gizem Portakal
- Department of Physics, Science and Arts Faculty, Cukurova University, 01330, Adana, Turkey.,Department of Medical Physics, Velindre Cancer Centre, CF14 2TL, Cardiff, UK
| | - Sophie Shermer
- Department of Physics, College of Science, Swansea University, SA2 8PP, Swansea, UK
| | - Christopher Jenkins
- Department of Physics, College of Science, Swansea University, SA2 8PP, Swansea, UK
| | - Emiliano Spezi
- Department of Medical Physics, Velindre Cancer Centre, CF14 2TL, Cardiff, UK.,School of Engineering, Cardiff University, CF24 3AA, Cardiff, UK
| | - Teresa Perrett
- Department of Medical Physics, Velindre Cancer Centre, CF14 2TL, Cardiff, UK
| | - Nina Tuncel
- Department of Physics, Science Faculty, Akdeniz University, 07058, Antalya, Turkey
| | - Jonathan Phillips
- Institute of Life Science, Medical School, Swansea University, Swansea, SA2 8PP, UK
| |
Collapse
|
5
|
Hennel F, Pruessmann KP. MRI with phaseless encoding. Magn Reson Med 2016; 78:1029-1037. [DOI: 10.1002/mrm.26497] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Revised: 09/02/2016] [Accepted: 09/16/2016] [Indexed: 11/12/2022]
Affiliation(s)
- Franciszek Hennel
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Switzerland
| | - Klaas P. Pruessmann
- Institute for Biomedical Engineering; ETH Zurich and University of Zurich; Switzerland
| |
Collapse
|
6
|
Pawar K, Egan G, Zhang J. Multichannel compressive sensing MRI using noiselet encoding. PLoS One 2015; 10:e0126386. [PMID: 25965548 PMCID: PMC4429034 DOI: 10.1371/journal.pone.0126386] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2014] [Accepted: 04/01/2015] [Indexed: 11/29/2022] Open
Abstract
The incoherence between measurement and sparsifying transform matrices and the restricted isometry property (RIP) of measurement matrix are two of the key factors in determining the performance of compressive sensing (CS). In CS-MRI, the randomly under-sampled Fourier matrix is used as the measurement matrix and the wavelet transform is usually used as sparsifying transform matrix. However, the incoherence between the randomly under-sampled Fourier matrix and the wavelet matrix is not optimal, which can deteriorate the performance of CS-MRI. Using the mathematical result that noiselets are maximally incoherent with wavelets, this paper introduces the noiselet unitary bases as the measurement matrix to improve the incoherence and RIP in CS-MRI. Based on an empirical RIP analysis that compares the multichannel noiselet and multichannel Fourier measurement matrices in CS-MRI, we propose a multichannel compressive sensing (MCS) framework to take the advantage of multichannel data acquisition used in MRI scanners. Simulations are presented in the MCS framework to compare the performance of noiselet encoding reconstructions and Fourier encoding reconstructions at different acceleration factors. The comparisons indicate that multichannel noiselet measurement matrix has better RIP than that of its Fourier counterpart, and that noiselet encoded MCS-MRI outperforms Fourier encoded MCS-MRI in preserving image resolution and can achieve higher acceleration factors. To demonstrate the feasibility of the proposed noiselet encoding scheme, a pulse sequences with tailored spatially selective RF excitation pulses was designed and implemented on a 3T scanner to acquire the data in the noiselet domain from a phantom and a human brain. The results indicate that noislet encoding preserves image resolution better than Fouirer encoding.
Collapse
Affiliation(s)
- Kamlesh Pawar
- Department of Electrical and Computer System Engineering, Monash University, Melbourne, Australia
- Indian Institute of Technology Bombay, Mumbai, India
- IITB Monash Research Academy, Mumbai, India
| | - Gary Egan
- Monash Biomedical Imaging, Monash University, Melbourne, Australia
| | - Jingxin Zhang
- Department of Electrical and Computer System Engineering, Monash University, Melbourne, Australia
- School of Software and Electrical Engineering, Swinburne University of Technology, Melbourne, Australia
| |
Collapse
|
7
|
Enhancing the performance of accelerated MRI through preservation of acquisition SNR: An “aliased” k-space approach. Magn Reson Med 2014; 74:150-161. [DOI: 10.1002/mrm.25392] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2014] [Revised: 06/09/2014] [Accepted: 07/10/2014] [Indexed: 11/07/2022]
|
8
|
Zhang YT, Zheng YL, Lin WH, Zhang HY, Zhou XL. Challenges and opportunities in cardiovascular health informatics. IEEE Trans Biomed Eng 2013; 60:633-42. [PMID: 23380853 DOI: 10.1109/tbme.2013.2244892] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Cardiovascular health informatics is a rapidly evolving interdisciplinary field concerning the processing, integration/interpretation, storage, transmission, acquisition, and retrieval of information from cardiovascular systems for the early detection, early prediction, early prevention, early diagnosis, and early treatment of cardiovascular diseases (CVDs). Based on the first author's presentation at the first IEEE Life Sciences Grand Challenges Conference, held on October 4-5, 2012, at the National Academy of Sciences, Washington, DC, USA, this paper, focusing on coronary arteriosclerotic disease, will discuss three significant challenges of cardiovascular health informatics, including: 1) to invent unobtrusive and wearable multiparameter sensors with higher sensitivity for the real-time monitoring of physiological states; 2) to develop fast multimodal imaging technologies with higher resolution for the quantification and better understanding of structure, function, metabolism of cardiovascular systems at the different levels; and 3) to develop novel multiscale information fusion models and strategies with higher accuracy for the personalized predication of the CVDs. At the end of this paper, a summary is given to suggest open discussions on these three and more challenges that face the scientific community in this field in the future.
Collapse
Affiliation(s)
- Yuan-Ting Zhang
- Joint Research Centre for Biomedical Engineering, Department of Electronic Engineering, The Chinese University of Hong Kong, Hong Kong.
| | | | | | | | | |
Collapse
|
9
|
Small field of view imaging using wavelet encoding with 2 dimensional RF pulses and gradient echo: phantom results. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2009; 23:45-52. [PMID: 20024667 DOI: 10.1007/s10334-009-0193-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/09/2009] [Revised: 12/01/2009] [Accepted: 12/03/2009] [Indexed: 10/20/2022]
Abstract
OBJECT The objective of this work is to propose an imaging sequence based upon the wavelet encoding approach to provide MRI images free from folding artifacts, in the small field of view (FOV) regime, such as dynamic magnetic resonance imaging (MRI) studies. MATERIALS AND METHODS The method consists of using a 2D spatially selective RF excitation pulse inserted into a gradient- echo pulse sequence to excite spins within a determined plane where wavelet encoding is achieved in one direction and slice selection is performed in the second direction. Wavelet encoding allows for spatially localized excitation and consequently restricts the spins excited within a reduced FOV. It consists of varying, according to a predetermined scheme, the width and position of the profile of the so-called fast RF pulse of the 2D RF excitation pulse, to obey wavelet encoding translation and dilation conditions. This sequence is implemented on a 3 Tesla whole body Siemens scanner. RESULTS Compared to Fourier encoding, the proposed technique tested on phantoms with different shapes and structures, is able to provide gradient-echo reduced FOV images free from aliased signals. CONCLUSION Wavelet encoding is suitable for small FOV imaging in dynamic MRI studies.
Collapse
|
10
|
Kyriakos WE, Hoge WS, Mitsouras D. Generalized encoding through the use of selective excitation in accelerated parallel MRI. NMR IN BIOMEDICINE 2006; 19:379-92. [PMID: 16705639 DOI: 10.1002/nbm.1047] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
Selective RF excitation is employed in magnetic resonance imaging (MRI) to achieve a variety of effects, such as slice selection. More elaborate transverse magnetization patterns can be realized via tailored RF excitation pulses, useful for example to image any specific region geometry within the field of view, or, to acquire non-Fourier encoded samples of the underlying magnetization distribution. In this manuscript, we review prior work on the combination of selective RF excitation with parallel MRI acquisition techniques. This combination can be used both to advantageously manipulate the numerical conditioning of the reconstruction problem, as well as to compact the information content of the acquired data so as to improve the achievable acceleration rate. With the latter application it is possible to also consider the acceleration provided by parallel imaging alone as a compaction of information content, which in certain cases can be used to reduce the length of the selective excitations. The main contribution of this review is to show how the combination of selective excitation with parallel imaging provides the latter an added flexibility that can be used to either enhance image quality, increase imaging speed, or both.
Collapse
Affiliation(s)
- Walid E Kyriakos
- Department of Radiology, Children's Hospital and Harvard Medical School, Boston, MA, USA.
| | | | | |
Collapse
|