Bulletin of the American Physical Society
APS March Meeting 2022
Volume 67, Number 3
Monday–Friday, March 14–18, 2022; Chicago
Session G10: Frontiers of Magnetic ImagingFocus Recordings Available
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Sponsoring Units: GMED DBIO GMAG Chair: Stephen Russek, NIST Boulder Room: McCormick Place W-181A |
Tuesday, March 15, 2022 11:30AM - 12:06PM |
G10.00001: Life at the Bottom: NMR and MRI at 6.5 mT Invited Speaker: Matthew S Rosen A promising approach to portable MRI is operation at ultra-low magnetic field where cost-effective electromagnets become practical. MRI in the ultra-low field (ULF) regime —when the magnetic field used for signal detection is below 10 mT—is inherently challenging mainly due to intrinsically low Boltzmann polarization. We will discuss signal acquisition approaches and hardware methods to improve attainable SNR in the Johnson-noise-dominated Larmor frequency of 276 kHz (6.5 mT) [1,2]. We will also discuss our work to reduce noise and increase attainable information per unit time using compute-based approaches that leverage low-cost GPU. These include magnetic resonance fingerprinting (MRF) to enable multiple quantitative contrasts at ULF [3], and the use of our neural network deep learning approach, AUTOMAP, to reconstruct highly-undersampled low SNR imaging data [4,5]. In addition, we will discuss several classes of NMR and MRI experiments enabled by operation at low magnetic field, which can outperform what can be done with high-field instruments [6–16]. |
Tuesday, March 15, 2022 12:06PM - 12:18PM |
G10.00002: Imaging Néel Relaxation of Superparamagnetic Nanoparticles using Diamond Magnetic Microscopy Bryan A Richards, Nate Ristoff, Abdelghani Laraoui, Ilja Fescenko, Joshua Damron, Nazanin Mosavian, Janis Smits, Andrey Jarmola, Pauli Kehayias, Maziar Saleh Ziabari, Andrew M Mounce, Dale L Huber, Victor Acosta Widefield diamond magnetic microscopy using nitrogen-vacancy centers is an emerging technique in various fields, including the study of magnetic materials. Superparamagnetic iron-oxide nanoparticles (SPIONs) are of interest for biomedical imaging applications, many of which would benefit from characterizing SPION Néel relaxation times at the single-particle level. Here, we report progress on the use of diamond magnetic microscopy to study the magnetic relaxation dynamics of single SPIONs and characterize their heterogeneity. |
Tuesday, March 15, 2022 12:18PM - 12:30PM Withdrawn |
G10.00003: Developing a Magnetic Resonance Spectroscopy Instrument for use in Consumer Health Gil Travish Metabolomics has evolved over the past 50 years from “you are what you eat” to databases of thousands of metabolites, deterministic pathways and linking to multiple-omics. State of the art labortatory-based instruments including Nuclear Magnetic Resonance (NMR) and Liquid Chromotograph - Mass Spectrometry (LQ-MS) are highly sensitive and able to resolve thousands of metabolites in complex biological solutions such as human blood. Clinically based instruments such as Magnetic Resonance Imaging and Spectroscopy (MRI & MRS) are capable of imaging and identifying tissue composition in vivo. Both lab-based NMR and clinic-based MRS instruments are complex, expensive and require expert operators. There is an opportunity to make a new class of instruments which enables general health tracking through non invasive, in vivo metabolomic measurements. We describe early development efforts of such a device including methods to increase signal to noise using novel filtering techniques, simulations of the device performance and design of the magnet. |
Tuesday, March 15, 2022 12:30PM - 12:42PM |
G10.00004: Magnetic Particle Imaging Using a Single Sided Field Free Line Scanner Alexey A Tonyushkin, Christopher P McDonough, David Newey Magnetic Particle Imaging (MPI) is a novel biomedical imaging modality that images distributions of superparamagnetic iron oxide nanoparticles (SPIONs). Similar to other tracer-based imaging modalities, e.g. PET, and SPECT, the image constitutes hot spots of the distributions of SPIONs targeting a pathology with full signal quantification and no tissue contrast. In a typical MPI scanner the ac magnetic field is used to excite SPIONs, and dc magnetic field is used to create a field free region where the SPIONs response to the ac magnetic field is maximum. To date, MPI has not been translated to the clinic due to the challenges of scaling up the MPI hardware to wide bore. Therefore, we consider an alternative geometry of a single-sided scanner where all hardware is located on one side to accommodate imaging of larger subjects. Furthermore, in our device the gradient of the magnetic field is created by a pair of co-planar elongated coils that produce a field-free line. This topology potentially provides higher sensitivity and more robust image reconstruction by means of filtered back-projection (FBP). In this work we show imaging simulations that make use of the FBP method, which demonstrates the viability of our scanner, and present experimental images of one dimensional phantoms. |
Tuesday, March 15, 2022 12:42PM - 12:54PM |
G10.00005: Non-negative Least Squares using Multi-regularization and a Gaussian Basis, with Application to Magnetic Resonance Relaxometry Richard G Spencer, Chuan Bi, Yvonne M. Ou, Wenshu Qian, Kenneth M Fishbein, Mustapha Bouhrara The discretized Fredholm equation of the first kind (FEFK) is encountered frequently in physics. Major applications include magnetic resonance relaxometry (MRR) and fluorescence decay analysis. Tikhonov regularization is often used to stabilize the ill-posed problem of solving the FEFK from data. However, the choice of regularization parameter, is problematic. Current approaches identify an optimal value of, with the corresponding solution taken as the recovered distribution function (DF). However, we observe that DF’s obtained from nearly indistinguishable signals respond differently to regularization over a range of values, indicating the substantial information content of regularized solutions corresponding to non-optimal. Accordingly, we have developed a multiple regularization (MultiReg) approach to solving the FEFK by incorporating a linear combination of solutions corresponding to a set of values. We demonstrate an on average >30% improved accuracy and precision across a wide range of synthetic target DF, and find a markedly reduced reliance on the selection of an optimal. We show the application of MultiReg to MRR T2 relaxometry data. MultiReg represents a potentially significant advance in regularization of ill-posed inverse problems arising from the FEFK in physics. |
Tuesday, March 15, 2022 12:54PM - 1:30PM |
G10.00006: Magnetic Resonance Imaging of Cancer Turns 45: How It Works, How We Use It Today, and Future Outlook Invited Speaker: David W Jordan Magnetic resonance imaging, which produces images from spatially-resolved nuclear magnetic resonance (NMR) measurements, has been established for in-vivo human use for 45 years. Its first application was the differentiation of cancer from healthy tissue. The NMR properties of living tissue form the basis of established clinical MRI techniques and interpretation. More recent advances have expanded the tools available to clinicians, enabling not only the detection of tumors, but measurement and characterization, enabling more specific diagnoses as well as monitoring of therapeutic response. Additional applications beyond cancer imaging now support diagnosis and treatment of virtually every organ, tissue, and system in the human body. With ubiquitous applications in modern medicine, the future of MRI research emphasizes development of quantitative imaging techniques, improved speed and safety, and increased access for patients to receive MRI scanning. This presentation will review the physical fundamentals of MRI signal and contrast, provide a clinical overview of the techniques used in current radiology practice, and highlight current, ongoing research for the future development of MRI in human health. |
Tuesday, March 15, 2022 1:30PM - 1:42PM |
G10.00007: The physical basis of using MRI for cancer detection Donald C Chang MRI (Magnetic Resonance imaging) is a very important technique in bio-medical physics. The MRI device has become a must-have diagnostic tool in most hospitals and large clinics today. Thus, there is a strong interest to understand how NMR measurements can differentiate cancer cells from normal cells. One key finding in the development of the MRI techniques was that, the contrast of MRI image was found to be based on difference in nuclear relaxation times rather than concentration difference of cellular water. At present, there is still a challenge to understand the mechanisms behind relaxation time changes of water protons during cancer development. In this talk, I will review the history of MRI development and discuss the possible physical mechanism behind the relaxation time changes between normal cells and cancer cells. |
Tuesday, March 15, 2022 1:42PM - 1:54PM |
G10.00008: Highly sensitive and high throughput magnetic resonance thermometry using superparamagnetic nanoparticles Darshan Chalise, David G Cahill Magnetic resonance imaging (MRI) enables non-invasive 3D temperature monitoring during thermal ablation of tumors. While T1 or T2 contrast MRI are relatively insensitive to temperature, techniques with greater temperature sensitivity such as chemical shift or diffusion imaging suffer from motional artifacts and long scan times. We describe an approach for highly sensitive and high throughput MR thermometry that is not susceptible to motional artifacts. We use superparamagnetic iron oxide nanoparticles (SPIONs) to spoil T2 of water protons. Motional narrowing results in proportionality between T2 and the diffusion constant, dependent only on temperature in a specific environment. Our results show, for pure water, the NMR linewidth and T2 follow the same temperature dependence as the self-diffusion constant of water. Thus, a T2 mapping is a diffusion mapping in the presence of SPIONs, and T2 is a thermometer. For pure water, a T2 mapping in a 9.4 T MRI scanner resulted in a temperature resolution of 0.5 K for a scan time of 2 minutes. This indicates a highly sensitive and high throughput MR thermometry technique potentially useful for monitoring of tissues during thermal therapies or for diagnosis. |
Tuesday, March 15, 2022 1:54PM - 2:06PM |
G10.00009: Room temperature hyperpolarization of 13C in diamond at 3.34 T Chandrasekhar Ramanathan, Daphna Shimon Electron and nuclear spins in diamond have long coherence and relaxation times at room temperature, making them a promising platform for applications such as biomedical and molecular imaging, nanoscale magnetic field sensing and diverse quantum technologies. While the optically-active nitrogen-vacancy (NV) defect has received a great deal of attention, the substitutional nitrogen (or P1) center also exhibits long coherence and relaxation times. Here, we use microwave-induced dynamic nuclear polarization (DNP) of the P1 centers to enhance the NMR signals of natural abundance 13C nuclei at 3.34 T at room temperature. We observe a greater than 100-fold enhancement of the 13C NMR signal with W-band (~94 GHz) millimeter-wave excitation. The DNP spectrum (enhancement as a function of millimeter-wave frequency) shows features that broadly correlate with the electron paramagnetic resonance spectrum. The shape of the DNP spectrum indicates that multiple physical mechanisms can give rise to DNP in diamond under these conditions including the Overhauser effect, the solid effect and the cross effect. We also investigate DNP under optical excitation of adjacent NV centers and two-tone microwave excitation. |
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