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Triolo E, Khegai O, Ozkaya E, Rossi N, Alipour A, Fleysher L, Balchandani P, Kurt M. Design, Construction, and Implementation of a Magnetic Resonance Elastography Actuator for Research Purposes. Curr Protoc 2022; 2:e379. [PMID: 35286023 PMCID: PMC9517172 DOI: 10.1002/cpz1.379] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Magnetic resonance elastography (MRE) is a technique for determining the mechanical response of soft materials using applied harmonic deformation of the material and a motion-sensitive magnetic resonance imaging sequence. This technique can elucidate significant information about the health and development of human tissue such as liver and brain, and has been used on phantom models (e.g., agar, silicone) to determine their suitability for use as a mechanical surrogate for human tissues in experimental models. The applied harmonic deformation used in MRE is generated by an actuator, transmitted in bursts of a specified duration, and synchronized with the magnetic resonance signal excitation. These actuators are most often a pneumatic design (common for human tissues or phantoms) or a piezoelectric design (common for small animal tissues or phantoms). Here, we describe how to design and assemble both a pneumatic and a piezoelectric MRE actuator for research purposes. For each of these actuator types, we discuss displacement requirements, end-effector options and challenges, electronics and electronic-driving requirements and considerations, and full MRE implementation. We also discuss how to choose the actuator type, size, and power based on the intended material and use. © 2022 Wiley Periodicals LLC. Basic Protocol 1: Design, construction, and implementation of a convertible pneumatic MRE actuator for use with tissues and phantom models Basic Protocol 2: Design, construction, and implementation of a piezoelectric MRE actuator for localized excitation in phantom models.
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Affiliation(s)
- E.R. Triolo
- University of Washington, Dept. of Mechanical Engineering (3900 E Stevens Way NE Seattle, WA 98195)
| | - O. Khegai
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - E. Ozkaya
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - N. Rossi
- Stevens Institute of Technology, Dept. of Mechanical Engineering (1 Castle Point Terrace, Hoboken, NJ 07030)
| | - A. Alipour
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - L. Fleysher
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - P. Balchandani
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
| | - M. Kurt
- University of Washington, Dept. of Mechanical Engineering (3900 E Stevens Way NE Seattle, WA 98195)
- Icahn School of Medicine at Mount Sinai, BioMedical Engineering and Imaging Institute (1470 Madison Ave, New York City, NY 10029)
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Short echo time dual-frequency MR Elastography with Optimal Control RF pulses. Sci Rep 2022; 12:1406. [PMID: 35082303 PMCID: PMC8791955 DOI: 10.1038/s41598-022-05262-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2021] [Accepted: 01/03/2022] [Indexed: 01/05/2023] Open
Abstract
Magnetic Resonance Elastography (MRE) quantifies the mechanical properties of tissues, typically applying motion encoding gradients (MEG). Multifrequency results allow better characterizations of tissues using data usually acquired through sequential monofrequency experiments. High frequencies are difficult to reach due to slew rate limitations and low frequencies induce long TEs, yielding magnitude images with low SNR. We propose a novel strategy to perform simultaneous multifrequency MRE in the absence of MEGs: using RF pulses designed via the Optimal Control (OC) theory. Such pulses control the spatial distribution of the MRI magnetization phase so that the resulting transverse magnetization reproduces the phase pattern of an MRE acquisition. The pulse is applied with a constant gradient during the multifrequency mechanical excitation to simultaneously achieve slice selection and motion encoding. The phase offset sampling strategy can be adapted according to the excitation frequencies to reduce the acquisition time. Phantom experiments were run to compare the classical monofrequency MRE to the OC based dual-frequency MRE method and showed excellent agreement between the reconstructed shear storage modulus G′. Our method could be applied to simultaneously acquire low and high frequency components, which are difficult to encode with the classical MEG MRE strategy.
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Qiu S, He Z, Wang R, Li R, Zhang A, Yan F, Feng Y. An electromagnetic actuator for brain magnetic resonance elastography with high frequency accuracy. NMR IN BIOMEDICINE 2021; 34:e4592. [PMID: 34291510 DOI: 10.1002/nbm.4592] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/21/2021] [Revised: 06/07/2021] [Accepted: 07/06/2021] [Indexed: 06/13/2023]
Abstract
Our goal is to design, test and verify an electromagnetic actuator for brain magnetic resonance elastography (MRE). We proposed a grappler-shaped design that can transmit stable vibrations into the brain. To validate its performance, simulations were carried out to ensure the electromagnetic field generated by the actuator did not interfere with the B0 field. The actuation vibration spectrum was analyzed to verify the actuation accuracy. Phantom and volunteer experiments were carried out to evaluate the performance of the actuator. Simulation of the magnetic field showed that the proposed actuator has a fringe field of less than 3 G in the imaging region. The phantom experiments showed that the proposed actuator did not interfere with the routine imaging sequences. The measured vibration spectra demonstrated that the frequency offset was about one third that of a pneumatic device and the transmission efficiency was three times higher. The shear moduli estimated from brain MRE were consistent with those from the literature. The actuation frequency of the proposed actuator has less frequency offset and off-center frequency components compared with the pneumatic counterpart. The whole actuator weighted only 980 g. The actuator can carry out multifrequency MRE on the brain with high accuracy. It is easy to use, comfortable for the patient and portable.
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Affiliation(s)
- Suhao Qiu
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Zhao He
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Runke Wang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Ruokun Li
- Department of Radiology, Ruijin Hospital, Shanghai, China
| | - Aili Zhang
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
| | - Fuhua Yan
- Department of Radiology, Ruijin Hospital, Shanghai, China
| | - Yuan Feng
- School of Biomedical Engineering, Shanghai Jiao Tong University, Shanghai, China
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Bauer DF, Adlung A, Brumer I, Golla AK, Russ T, Oelschlegel E, Tollens F, Clausen S, Aumüller P, Schad LR, Nörenberg D, Zöllner FG. An anthropomorphic pelvis phantom for MR-guided prostate interventions. Magn Reson Med 2021; 87:1605-1612. [PMID: 34652819 DOI: 10.1002/mrm.29043] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2021] [Revised: 09/01/2021] [Accepted: 09/22/2021] [Indexed: 01/02/2023]
Abstract
PURPOSE To design and manufacture a pelvis phantom for magnetic resonance (MR)-guided prostate interventions, such as MRGB (MR-guided biopsy) or brachytherapy seed placement. METHODS The phantom was designed to mimic the human pelvis incorporating bones, bladder, prostate with four lesions, urethra, arteries, veins, and six lymph nodes embedded in ballistic gelatin. A hollow rectum enables transrectal access to the prostate. To demonstrate the feasibility of the phantom for minimal invasive MRI-guided interventions, a targeted inbore MRGB was performed. The needle probe was rectally inserted and guided using an MRI-compatible remote controlled manipulator (RCM). RESULTS The presented pelvis phantom has realistic imaging properties for MR imaging (MRI), computed tomography (CT) and ultrasound (US). In the targeted inbore MRGB, a prostate lesion was successfully hit with an accuracy of 3.5 mm. The experiment demonstrates that the limited size of the rectum represents a realistic impairment for needle placements. CONCLUSION The phantom provides a valuable platform for evaluating the performance of MRGB systems. Interventionalists can use the phantom to learn how to deal with challenging situations, without risking harm to patients.
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Affiliation(s)
- Dominik F Bauer
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Anne Adlung
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Irène Brumer
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Alena-Kathrin Golla
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Tom Russ
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Eva Oelschlegel
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Fabian Tollens
- Department of Radiology and Nuclear Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
| | - Sven Clausen
- Department of Radiation Oncology, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
| | - Philipp Aumüller
- Department of Radiation Oncology, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
| | - Lothar R Schad
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
| | - Dominik Nörenberg
- Department of Radiology and Nuclear Medicine, University Medical Center Mannheim, Heidelberg University, Mannheim, Germany
| | - Frank G Zöllner
- Computer Assisted Clinical Medicine, Medical Faculty Mannheim, Mannheim Institute for Intelligent Systems in Medicine, Heidelberg University, Mannheim, Germany
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Hagiwara A, Fujita S, Ohno Y, Aoki S. Variability and Standardization of Quantitative Imaging: Monoparametric to Multiparametric Quantification, Radiomics, and Artificial Intelligence. Invest Radiol 2020; 55:601-616. [PMID: 32209816 PMCID: PMC7413678 DOI: 10.1097/rli.0000000000000666] [Citation(s) in RCA: 73] [Impact Index Per Article: 18.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2020] [Accepted: 01/28/2020] [Indexed: 12/19/2022]
Abstract
Radiological images have been assessed qualitatively in most clinical settings by the expert eyes of radiologists and other clinicians. On the other hand, quantification of radiological images has the potential to detect early disease that may be difficult to detect with human eyes, complement or replace biopsy, and provide clear differentiation of disease stage. Further, objective assessment by quantification is a prerequisite of personalized/precision medicine. This review article aims to summarize and discuss how the variability of quantitative values derived from radiological images are induced by a number of factors and how these variabilities are mitigated and standardization of the quantitative values are achieved. We discuss the variabilities of specific biomarkers derived from magnetic resonance imaging and computed tomography, and focus on diffusion-weighted imaging, relaxometry, lung density evaluation, and computer-aided computed tomography volumetry. We also review the sources of variability and current efforts of standardization of the rapidly evolving techniques, which include radiomics and artificial intelligence.
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Affiliation(s)
- Akifumi Hagiwara
- From the Department of Radiology, Juntendo University School of Medicine, Tokyo
| | | | - Yoshiharu Ohno
- Department of Radiology, Fujita Health University School of Medicine, Toyoake, Aichi, Japan
| | - Shigeki Aoki
- From the Department of Radiology, Juntendo University School of Medicine, Tokyo
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Runge JH, Hoelzl SH, Sudakova J, Dokumaci AS, Nelissen JL, Guenthner C, Lee J, Troelstra M, Fovargue D, Stoker J, Nederveen AJ, Nordsletten D, Sinkus R. A novel magnetic resonance elastography transducer concept based on a rotational eccentric mass: preliminary experiences with the gravitational transducer. ACTA ACUST UNITED AC 2019; 64:045007. [DOI: 10.1088/1361-6560/aaf9f8] [Citation(s) in RCA: 15] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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