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Selvaganesan K, Wan Y, Ha Y, Wu B, Hancock K, Galiana G, Constable RT. Magnetic resonance imaging using a nonuniform Bo (NuBo) field-cycling magnet. PLoS One 2023; 18:e0287344. [PMID: 37319289 PMCID: PMC10270621 DOI: 10.1371/journal.pone.0287344] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2023] [Accepted: 06/02/2023] [Indexed: 06/17/2023] Open
Abstract
Magnetic resonance imaging (MRI) is a powerful noninvasive diagnostic tool with superior soft tissue contrast. However, access to MRI is limited since current systems depend on homogeneous, high field strength main magnets (B0-fields), with strong switchable gradients which are expensive to install and maintain. In this work we propose a new approach to MRI where imaging is performed in an inhomogeneous field using radiofrequency spatial encoding, thereby eliminating the need for uniform B0-fields and conventional cylindrical gradient coils. The proposed technology uses an innovative data acquisition and reconstruction approach by integrating developments in field cycling, parallel imaging and non-Fourier based algebraic reconstruction. The scanner uses field cycling to image in an inhomogeneous B0-field; in this way magnetization is maximized during the high field polarization phase, and B0 inhomogeneity effects are minimized by using a low field during image acquisition. In addition to presenting the concept, this work provides experimental verification of a long-lived spin echo signal, spatially varying resolution, as well as both simulated and experimental 2D images. Our initial design creates an open MR system that can be installed in a patient examination table for body imaging (e.g., breast or liver) or built into a wall for weighted-spine imaging. The proposed system introduces a new class of inexpensive, open, silent MRIs that could be housed in doctor's offices much like ultrasound is today, making MRI more widely accessible.
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Affiliation(s)
- Kartiga Selvaganesan
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America
| | - Yuqing Wan
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States of America
| | - Yonghyun Ha
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States of America
| | - Baosong Wu
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States of America
| | - Kasey Hancock
- Department of Electrical Engineering, Yale University, New Haven, CT, United States of America
| | - Gigi Galiana
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States of America
| | - R. Todd Constable
- Department of Biomedical Engineering, Yale University, New Haven, CT, United States of America
- Department of Radiology and Biomedical Imaging, Yale School of Medicine, New Haven, CT, United States of America
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2
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Savukov I, Kim YJ, Newman S. High-resolution ultra-low field magnetic resonance imaging with a high-sensitivity sensing coil. JOURNAL OF APPLIED PHYSICS 2022; 132:174503. [PMID: 36339744 PMCID: PMC9633096 DOI: 10.1063/5.0123692] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 10/07/2022] [Indexed: 06/16/2023]
Abstract
We present high-resolution magnetic resonance imaging (MRI) at ultra-low field (ULF) with a proton Larmor frequency of around 120 kHz. The key element is a specially designed high-sensitivity sensing coil in the shape of a solenoid with a few millimeter gap between windings to decrease the proximity effect and, hence, increase the coil's quality ( Q ) factor and sensitivity. External noise is strongly suppressed by enclosing the sensing coil in a copper cylindrical shield, large enough not to negatively affect the coil's Q factor and sensitivity, measured to be 217 and 0.47 fT/Hz1 / 2 , respectively. To enhance small polarization of proton spins at ULF, a strong pulsed 0.1 T prepolarization field is applied, making the signal-to-noise ratio (SNR) of ULF MRI sufficient for high-quality imaging in a short time. We demonstrate ULF MRI of a copper sulfate solution phantom with a resolution of 1 × 1 × 8.5 mm 3 and SNR of 10. The acquisition time is 6.3 min without averaging. The sensing coil size in the current realization can accommodate imaging objects of 9 cm in size, sufficient for hand, and it can be further increased for human head imaging in the future. Since the in-plane resolution of 1 × 1 mm 2 is typical in anatomical medical imaging, this ULF MRI method can be an alternative low-cost, rapid, portable method for anatomical medical imaging of the human body or animals. This ULF MRI method can supplement other MRI methods, especially when such methods are restricted due to high cost, portability requirement, imaging artifacts, and other factors.
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Affiliation(s)
| | - Young Jin Kim
- MPA-Quantum, Los Alamos National Laboratory, P.O. Box 1663, MS-D454, Los Alamos, New Mexico 87545, USA
| | - Shaun Newman
- MPA-Quantum, Los Alamos National Laboratory, P.O. Box 1663, MS-D454, Los Alamos, New Mexico 87545, USA
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3
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Natukunda F, Twongyirwe TM, Schiff SJ, Obungoloch J. Approaches in cooling of resistive coil-based low-field Magnetic Resonance Imaging (MRI) systems for application in low resource settings. BMC Biomed Eng 2021; 3:3. [PMID: 33579373 PMCID: PMC7881601 DOI: 10.1186/s42490-021-00048-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Accepted: 02/02/2021] [Indexed: 11/10/2022] Open
Abstract
Magnetic Resonance Imaging (MRI), a non-invasive method for the diagnosis of diverse health conditions has experienced growing popularity over other imaging modalities like ultrasound and Computer Tomography. Initially, proof-of-concept and earlier MRI systems were based on resistive and permanent magnet technology. However, superconducting magnets have long held monopoly of the market for MRI systems with their high-field (HF) strength capability, although they present high construction, installation, and siting requirements. Such stringent prerequisites restrict their availability and use in low-middle income countries. Resistive coil-based magnet, albeit low-field (LF) in capacity, represent a plausible boost for the availability and use of MRI systems in resource constrained settings. These systems are characterized by low costs coupled with substantial image quality for diagnosis of some conditions such as hydrocephalus common is such regions. However, the nature of resistive coils causes them to heat up during operation, thus necessitating a dedicated cooling system to improve image quality and enhance system longevity. This paper explores a range of cooling methods as have been applied to resistive magnets, citing their pros and cons and areas for improvement.
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Affiliation(s)
- Faith Natukunda
- Department of Biomedical Engineering, Mbarara University of Science and Technology, Mbarara, Uganda.
| | - Theodora M Twongyirwe
- Department of Mechanical Engineering, Mbarara University of Science and Technology, Mbarara, Uganda
| | - Steven J Schiff
- Centre for Neural Engineering, Departments of Engineering Science and Mechanics, Neurosurgery, and Physics, The Pennsylvania State University, Pennsylvania, USA
| | - Johnes Obungoloch
- Department of Biomedical Engineering, Mbarara University of Science and Technology, Mbarara, Uganda
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4
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Nakagomi M, Kajiwara M, Matsuzaki J, Tanabe K, Hoshiai S, Okamoto Y, Terada Y. Development of a small car-mounted magnetic resonance imaging system for human elbows using a 0.2 T permanent magnet. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 304:1-6. [PMID: 31063952 DOI: 10.1016/j.jmr.2019.04.017] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2019] [Revised: 04/08/2019] [Accepted: 04/27/2019] [Indexed: 05/05/2023]
Abstract
Portable magnetic resonance imaging (MRI) scanners can provide opportunities for mobile operation in many environments including disease screening and primary care suites. Here, we develop a new, compact transportable MRI system for imaging small joints of the extremities using a 0.2 T, 200 kg permanent magnet. The whole system, including the magnet, gradient coils, RF probes, and MRI consoles (80 kg in weight) was installed in a standard-size minivan-style vehicle. The use of the open-geometry magnet enables easy patient positioning within the limited space of the vehicle. We show that our portable MRI system provides clinically relevant images of screening for elbow injuries induced by overuse of overhand throwing. This transportable system is deployable during sport events or in environments with poor access to MRI systems, and could be applicable for mass screening, early diagnosis, and case finding.
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Affiliation(s)
- Mayu Nakagomi
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Michiru Kajiwara
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Jumpei Matsuzaki
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Katsumasa Tanabe
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Sodai Hoshiai
- Institute of Clinical Medicine, Department of Diagnostic and Interventional Radiology, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Yoshikazu Okamoto
- Institute of Clinical Medicine, Department of Diagnostic and Interventional Radiology, University of Tsukuba, Tsukuba, Ibaraki, Japan
| | - Yasuhiko Terada
- Institute of Applied Physics, University of Tsukuba, Tsukuba, Ibaraki, Japan.
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5
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Obungoloch J, Harper JR, Consevage S, Savukov IM, Neuberger T, Tadigadapa S, Schiff SJ. Design of a sustainable prepolarizing magnetic resonance imaging system for infant hydrocephalus. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2018; 31:665-676. [PMID: 29644479 DOI: 10.1007/s10334-018-0683-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/03/2017] [Revised: 03/11/2018] [Accepted: 03/15/2018] [Indexed: 10/17/2022]
Abstract
OBJECTIVES The need for affordable and appropriate medical technologies for developing countries continues to rise as challenges such as inadequate energy supply, limited technical expertise, and poor infrastructure persist. Low-field magnetic resonance imaging (LF MRI) is a technology that can be tailored to meet specific imaging needs within such countries. Its low power requirements and the possibility of operating in minimally shielded or unshielded environments make it especially attractive. Although the technology has been widely demonstrated over several decades, it is yet to be shown that it can be diagnostic and improve patient outcomes in clinical applications. We here demonstrate the robustness of prepolarizing MRI (PMRI) technology for assembly and deployment in developing countries for the specific application to infant hydrocephalus. Hydrocephalus treatment planning and management requires only modest spatial resolution, such that the brain can be distinguished from fluid-tissue contrast detail within the brain parenchyma is not essential. MATERIALS AND METHODS We constructed an internally shielded PMRI system based on the Lee-Whiting coil system with a 22-cm diameter of spherical volume. RESULTS In an unshielded room, projection phantom images were acquired at 113 kHz with in-plane resolution of 3 mm × 3 mm, by introducing gradient fields of sufficient magnitude to dominate the 5000 ppm inhomogeneity of the readout field. DISCUSSION The low cost, straightforward assembly, deployment potential, and maintenance requirements demonstrate the suitability of our PMRI system for developing countries. Further improvement in image spatial resolution and contrast of LF MRI will broaden its potential clinical utility beyond hydrocephalus.
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Affiliation(s)
- Johnes Obungoloch
- Center for Neural Engineering, The Pennsylvania State University, University Park, 16802, USA.,Department of Biomedical Engineering, The Pennsylvania State University, University Park, 16802, USA.,Mbarara University of Science and Technology, P.O Box 1410, Mbarara, Uganda
| | - Joshua R Harper
- Center for Neural Engineering, The Pennsylvania State University, University Park, 16802, USA.,Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, 16802, USA
| | - Steven Consevage
- Center for Neural Engineering, The Pennsylvania State University, University Park, 16802, USA.,Department of Physics, The Pennsylvania State University, University Park, 16802, USA
| | | | - Thomas Neuberger
- Department of Biomedical Engineering, The Pennsylvania State University, University Park, 16802, USA.,The Huck Institutes of the Life Sciences, The Pennsylvania State University, University Park, 16802, USA
| | - Srinivas Tadigadapa
- Department of Electrical Engineering, The Pennsylvania State University, University Park, 16802, USA
| | - Steven J Schiff
- Center for Neural Engineering, The Pennsylvania State University, University Park, 16802, USA. .,Department of Biomedical Engineering, The Pennsylvania State University, University Park, 16802, USA. .,Department of Engineering Science and Mechanics, The Pennsylvania State University, University Park, 16802, USA. .,Department of Physics, The Pennsylvania State University, University Park, 16802, USA. .,Department of Neurosurgery, Penn State College of Medicine, Hershey, 17033, USA.
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6
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Lother S, Schiff SJ, Neuberger T, Jakob PM, Fidler F. Design of a mobile, homogeneous, and efficient electromagnet with a large field of view for neonatal low-field MRI. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2016; 29:691-8. [PMID: 26861046 DOI: 10.1007/s10334-016-0525-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/20/2015] [Revised: 12/31/2015] [Accepted: 01/05/2016] [Indexed: 11/28/2022]
Abstract
OBJECTIVE In this work, a prototype of an effective electromagnet with a field-of-view (FoV) of 140 mm for neonatal head imaging is presented. The efficient implementation succeeded by exploiting the use of steel plates as a housing system. We achieved a compromise between large sample volumes, high homogeneity, high B0 field, low power consumption, light weight, simple fabrication, and conserved mobility without the necessity of a dedicated water cooling system. MATERIALS AND METHODS The entire magnetic resonance imaging (MRI) system (electromagnet, gradient system, transmit/receive coil, control system) is introduced and its unique features discussed. Furthermore, simulations using a numerical optimization algorithm for magnet and gradient system are presented. RESULTS Functionality and quality of this low-field scanner operating at 23 mT (generated with 500 W) is illustrated using spin-echo imaging (in-plane resolution 1.6 mm × 1.6 mm, slice thickness 5 mm, and signal-to-noise ratio (SNR) of 23 with a acquisition time of 29 min). B0 field-mapping measurements are presented to characterize the homogeneity of the magnet, and the B0 field limitations of 80 mT of the system are fully discussed. CONCLUSION The cryogen-free system presented here demonstrates that this electromagnet with a ferromagnetic housing can be optimized for MRI with an enhanced and homogeneous magnetic field. It offers an alternative to prepolarized MRI designs in both readout field strength and power use. There are multiple indications for the clinical medical application of such low-field devices.
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Affiliation(s)
- Steffen Lother
- Research Center Magnetic-Resonance-Bavaria (MRB), Am Hubland, 97074, Würzburg, Germany.
| | - Steven J Schiff
- Departments of Engineering Science and Mechanics, Neurosurgery, and Physics, Center of Neural Engineering, Penn State University, University Park, PA, USA
| | - Thomas Neuberger
- High Field MRI Facility, Huck Institutes of the Life Sciences, Penn State University, University Park, PA, USA.,Department of Biomedical Engineering, Penn State University, University Park, PA, USA
| | - Peter M Jakob
- Research Center Magnetic-Resonance-Bavaria (MRB), Am Hubland, 97074, Würzburg, Germany.,Department for Experimental Physics 5 (Biophysics), University of Wuerzburg, Würzburg, Germany
| | - Florian Fidler
- Research Center Magnetic-Resonance-Bavaria (MRB), Am Hubland, 97074, Würzburg, Germany
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7
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Galante A, Sinibaldi R, Conti A, De Luca C, Catallo N, Sebastiani P, Pizzella V, Romani GL, Sotgiu A, Della Penna S. Fast Room Temperature Very Low Field-Magnetic Resonance Imaging System Compatible with MagnetoEncephaloGraphy Environment. PLoS One 2015; 10:e0142701. [PMID: 26630172 PMCID: PMC4668052 DOI: 10.1371/journal.pone.0142701] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2015] [Accepted: 10/26/2015] [Indexed: 11/18/2022] Open
Abstract
In recent years, ultra-low field (ULF)-MRI is being given more and more attention, due to the possibility of integrating ULF-MRI and Magnetoencephalography (MEG) in the same device. Despite the signal-to-noise ratio (SNR) reduction, there are several advantages to operating at ULF, including increased tissue contrast, reduced cost and weight of the scanners, the potential to image patients that are not compatible with clinical scanners, and the opportunity to integrate different imaging modalities. The majority of ULF-MRI systems are based, until now, on magnetic field pulsed techniques for increasing SNR, using SQUID based detectors with Larmor frequencies in the kHz range. Although promising results were recently obtained with such systems, it is an open question whether similar SNR and reduced acquisition time can be achieved with simpler devices. In this work a room-temperature, MEG-compatible very-low field (VLF)-MRI device working in the range of several hundred kHz without sample pre-polarization is presented. This preserves many advantages of ULF-MRI, but for equivalent imaging conditions and SNR we achieve reduced imaging time based on preliminary results using phantoms and ex-vivo rabbits heads.
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Affiliation(s)
- Angelo Galante
- MESVA, Department of Life, Health & Environmental Sciences, L'Aquila University, Via Vetoio 10, Coppito, L'Aquila 67100, Italy
- Laboratori Nazionali del Gran Sasso, Istituto Nazionale di Fisica Nucleare, S.S. 17 bis km 18910, Assergi, L'Aquila 67010, Italy
- * E-mail:
| | - Raffaele Sinibaldi
- Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio" University, Chieti 66100, Italy
| | - Allegra Conti
- Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio" University, Chieti 66100, Italy
| | - Cinzia De Luca
- Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio" University, Chieti 66100, Italy
| | - Nadia Catallo
- MESVA, Department of Life, Health & Environmental Sciences, L'Aquila University, Via Vetoio 10, Coppito, L'Aquila 67100, Italy
| | - Piero Sebastiani
- ITA S.r.l., Zona Industriale di Pile, SS17, Località Boschetto, L'Aquila 67100, Italy
| | - Vittorio Pizzella
- Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio" University, Chieti 66100, Italy
- Institute of Advanced Biomedical Technologies, G. D'Annunzio" University, Chieti 66100, Italy
| | - Gian Luca Romani
- Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio" University, Chieti 66100, Italy
- Institute of Advanced Biomedical Technologies, G. D'Annunzio" University, Chieti 66100, Italy
| | - Antonello Sotgiu
- ITA S.r.l., Zona Industriale di Pile, SS17, Località Boschetto, L'Aquila 67100, Italy
| | - Stefania Della Penna
- Department of Neuroscience, Imaging and Clinical Sciences, G. D'Annunzio" University, Chieti 66100, Italy
- Institute of Advanced Biomedical Technologies, G. D'Annunzio" University, Chieti 66100, Italy
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8
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Sarracanie M, LaPierre CD, Salameh N, Waddington DEJ, Witzel T, Rosen MS. Low-Cost High-Performance MRI. Sci Rep 2015; 5:15177. [PMID: 26469756 PMCID: PMC4606787 DOI: 10.1038/srep15177] [Citation(s) in RCA: 139] [Impact Index Per Article: 15.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Accepted: 09/18/2015] [Indexed: 11/09/2022] Open
Abstract
Magnetic Resonance Imaging (MRI) is unparalleled in its ability to visualize anatomical structure and function non-invasively with high spatial and temporal resolution. Yet to overcome the low sensitivity inherent in inductive detection of weakly polarized nuclear spins, the vast majority of clinical MRI scanners employ superconducting magnets producing very high magnetic fields. Commonly found at 1.5-3 tesla (T), these powerful magnets are massive and have very strict infrastructure demands that preclude operation in many environments. MRI scanners are costly to purchase, site, and maintain, with the purchase price approaching $1 M per tesla (T) of magnetic field. We present here a remarkably simple, non-cryogenic approach to high-performance human MRI at ultra-low magnetic field, whereby modern under-sampling strategies are combined with fully-refocused dynamic spin control using steady-state free precession techniques. At 6.5 mT (more than 450 times lower than clinical MRI scanners) we demonstrate (2.5 × 3.5 × 8.5) mm(3) imaging resolution in the living human brain using a simple, open-geometry electromagnet, with 3D image acquisition over the entire brain in 6 minutes. We contend that these practical ultra-low magnetic field implementations of MRI (<10 mT) will complement traditional MRI, providing clinically relevant images and setting new standards for affordable (<$50,000) and robust portable devices.
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Affiliation(s)
- Mathieu Sarracanie
- MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.,Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA
| | - Cristen D LaPierre
- MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.,Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA
| | - Najat Salameh
- MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.,Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.,Institute of Physics of Biological Systems, Ecole Polytechnique Fédérale de Lausanne, CH-1015 Lausanne, Switzerland
| | - David E J Waddington
- MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.,Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.,School of Physics, University of Sydney, Physics Rd, Sydney NSW 2006, Australia
| | - Thomas Witzel
- MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA
| | - Matthew S Rosen
- MGH/A.A. Martinos Center for Biomedical Imaging, 149 13th St, Suite 2301, Charlestown MA 02129, USA.,Department of Physics, Harvard University, 17 Oxford St, Cambridge, MA 02138, USA.,Harvard Medical School, 25 Shattuck St, Boston, MA 02115, USA
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9
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Ruangchaithaweesuk S, Chintamsetti V, Yao L, Tsai TW, Xu S. High-resolution optically-detected magnetic resonance imaging in an ambient magnetic field. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 233:1-6. [PMID: 23708206 DOI: 10.1016/j.jmr.2013.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 04/23/2013] [Accepted: 05/02/2013] [Indexed: 06/02/2023]
Abstract
Magnetic resonance imaging (MRI) in an ultralow magnetic field usually has poor spatial resolution compared to its high-field counterpart. The concomitant field effect and low signal level are among the major causes that limit the spatial resolution. Here, we report a novel imaging method, a zoom-in scheme, to achieve a reasonably high spatial resolution of 0.6 mm x 0.6mm without suffering the concomitant field effect. This method involves multiple steps of spatial encoding with gradually increased spatial resolution but reduced field-of-view. This method takes advantage of the mobility of ultralow-field MRI and the large physical size of the ambient magnetic field. We also demonstrate the use of a unique gradient solenoid to improve the efficiency of optical detection with an atomic magnetometer. The enhanced filling factor improved the signal level and consequently facilitated an improved spatial resolution.
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10
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Savukov I, Karaulanov T, Wurden CJV, Schultz L. Non-cryogenic ultra-low field MRI of wrist-forearm area. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 233:103-106. [PMID: 23796804 PMCID: PMC3753084 DOI: 10.1016/j.jmr.2013.05.012] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2012] [Revised: 05/02/2013] [Accepted: 05/29/2013] [Indexed: 05/30/2023]
Abstract
Ultra-low field (ULF) MRI as an alternative to high field MRI can find some niche applications where high field is a liability. Previously we demonstrated hand images with a non-cryogenic ULF MRI system, but such a system was restrictive to the size of the imaging objects. We have modified the previous setup to increase the imaging volume and demonstrate the image of human hand near the wrist area. One goal for the demonstration is the evaluation of quality of larger bone structure to project image quality to other parts of extremities, such as elbows, shoulders, and knees. We found that after 12 min of acquisition, the image quality was quite satisfactory. To achieve this image quality, several problems were solved that appeared in the new system. The increase in the imaging volume size led to an increase in transient time and various measures were taken to reduce this time. We also explored a method of overcoming the artifacts and image quality reduction arising from field drifts present in the system due to heating of the coils. We believe that our results can be useful for evaluation of diagnostic capability of non-cryogenic ULF MRI of extremities and other parts of the body. The system can be also applied to image animals and tissues.
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Affiliation(s)
- I Savukov
- Los Alamos National Laboratory, Applied Modern Physics Group, MS D454, Los Alamos, NM 87545, United States.
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11
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Savukov I, Karaulanov T. Anatomical MRI with an atomic magnetometer. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2013; 231:39-45. [PMID: 23567881 DOI: 10.1016/j.jmr.2013.02.020] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2012] [Revised: 02/11/2013] [Accepted: 02/14/2013] [Indexed: 06/02/2023]
Abstract
Ultra-low field (ULF) MRI is a promising method for inexpensive medical imaging with various additional advantages over conventional instruments such as low weight, low power, portability, absence of artifacts from metals, and high contrast. Anatomical ULF MRI has been successfully implemented with SQUIDs, but SQUIDs have the drawback of a cryogen requirement. Atomic magnetometers have sensitivity comparable to SQUIDs and can be in principle used for ULF MRI to replace SQUIDs. Unfortunately some problems exist due to the sensitivity of atomic magnetometers to a magnetic field and gradients. At low frequency, noise is also substantial and a shielded room is needed for improving sensitivity. In this paper, we show that at 85 kHz, the atomic magnetometer can be used to obtain anatomical images. This is the first demonstration of any use of atomic magnetometers for anatomical MRI. The demonstrated resolution is 1.1 mm×1.4 mm in about 6 min of acquisition with SNR of 10. Some applications of the method are discussed. We discuss several measures to increase the sensitivity to reach a resolution 1 mm×1 mm.
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Affiliation(s)
- I Savukov
- Los Alamos National Laboratory, Los Alamos, NM 87545, USA.
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12
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Ruangchaithaweesuk S, Yu DS, Garcia NC, Yao L, Xu S. Applications of optically detected MRI for enhanced contrast and penetration in metal. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2012; 223:20-24. [PMID: 22954614 DOI: 10.1016/j.jmr.2012.07.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Revised: 07/06/2012] [Accepted: 07/07/2012] [Indexed: 06/01/2023]
Abstract
We report quantitative measurements using optically detected magnetic resonance imaging (MRI) for enhanced pH contrast and flow inside porous metals. Using a gadolinium chelate as the pH contrast agent, we show the response is 0.6s(-1) mM(-1) per pH unit at the ambient magnetic field for the pH range 6-8.5. A stopped flow scheme was used to directly measure T(1) relaxation time to determine the relaxivity. Flow profiles and images were obtained for a series of porous metals with different average pore sizes. The signal amplitudes and spatial distributions were compared. A clogged region in one of the samples was revealed using optically detected MRI but not optical imaging or scanning electron microscopy. These applications will significantly broaden the impact of optically detected MRI in chemical imaging and materials research.
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13
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