1
|
Nyman JS, Ketsiri T, Louie EA, Harkins KD, Manhard MK, Gochberg DF, Lee DH, Desai MJ, Maslow J, Tanner SB, Does MD. Toward the use of MRI measurements of bound and pore water in fracture risk assessment. Bone 2023; 176:116863. [PMID: 37527697 PMCID: PMC10528882 DOI: 10.1016/j.bone.2023.116863] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/07/2023] [Revised: 07/26/2023] [Accepted: 07/28/2023] [Indexed: 08/03/2023]
Abstract
The current clinical assessment of fracture risk lacks information about the inherent quality of a person's bone tissue. Working toward an imaging-based approach to quantify both a bone tissue quality marker (tissue hydration as water bound to the matrix) and a bone microstructure marker (porosity as water in pores), we hypothesized that the concentrations of bound water (Cbw) are lower and concentrations of pore water (Cpw) are higher in patients with osteoporosis (OP) than in age- and sex-matched adults without the disease. Using recent developments in ultrashort echo time (UTE) magnetic resonance imaging (MRI), maps of Cbw and Cpw were acquired from the uninjured distal third radius (Study 1) of 20 patients who experienced a fragility fracture of the distal radius (Fx) and 20 healthy controls (Non-Fx) and from the tibia mid-diaphysis (Study 2) of 30 women with clinical OP (low T-scores) and 15 women without OP (normal T-scores). In Study 1, Cbw was significantly lower (p = 0.0018) and Cpw was higher (p = 0.0022) in the Fx than in the Non-Fx group. In forward stepwise, logistic regression models using Bayesian Information Criterion for selecting the best set of predictors (from imaging parameters, age, BMI, and DXA scanner type), the area-under-the-receiver operator characteristics-curve (AUC with 95 % confidence intervals) was 0.73 (0.56, 0.86) for hip aBMD (best predictors without MRI) and 0.86 (0.70, 0.95) for the combination of Cbw and Cpw (best predictors overall). In Study 2, Cbw was significantly lower (p = 0.0005) in women with OP (23.8 ± 4.3 1H mol/L) than in women without OP (29.9 ± 6.4 1H mol/L); Cpw was significantly higher by estimate of 2.9 1H mol/L (p = 0.0298) with clinical OP, but only when accounting for the type of UTE-MRI scan with 3D providing higher values than 2D (p < 0.0001). Lastly, Cbw, but not Cpw, was sensitive to bone forming osteoporosis medications over 12-months. UTE-MRI-derived measurements of bound and pore water concentrations are potential, aBMD-independent predictors of fracture risk.
Collapse
Affiliation(s)
- Jeffry S Nyman
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA; Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Department of Veterans Affairs, Tennessee Valley Healthcare System, 1310 24th Ave. S., Nashville, TN 37212, USA; Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center,1211 Medical Center Dr., Nashville, TN 37212, USA.
| | - Thammathida Ketsiri
- Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Elizabeth A Louie
- Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Kevin D Harkins
- Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Mary Kate Manhard
- Imaging Research Center, Cincinnati Children's Hospital Medical Center, 3333 Burnet Ave, Cincinnati, OH 45229, USA
| | - Daniel F Gochberg
- Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Donald H Lee
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA
| | - Mihir J Desai
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA
| | - Jed Maslow
- Department of Orthopaedic Surgery, Vanderbilt University Medical Center, 1215 21st Ave. S., Suite 4200, Nashville, TN 37232, USA
| | - S Bobo Tanner
- Vanderbilt Center for Bone Biology, Vanderbilt University Medical Center,1211 Medical Center Dr., Nashville, TN 37212, USA; Department of Medicine, Division of Rheumatology, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA
| | - Mark D Does
- Department of Biomedical Engineering, Vanderbilt University, 5824 Stevenson Center, Nashville, TN 37232, USA; Institute of Imaging Science, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Radiology and Radiological Sciences, Vanderbilt University Medical Center, 1161 21st Ave. S., Nashville, TN 37232, USA; Department of Electrical Engineering and Computer Science, Vanderbilt University, 400 24th Ave. S., Nashville, TN 37212, USA.
| |
Collapse
|
2
|
Jang H, Athertya J, Jerban S, Ma Y, Lombardi AF, Chung CB, Chang EY, Du J. Correction of B 0 and linear eddy currents: Impact on morphological and quantitative ultrashort echo time double echo steady state (UTE-DESS) imaging. NMR IN BIOMEDICINE 2023; 36:e4939. [PMID: 36965076 PMCID: PMC10518369 DOI: 10.1002/nbm.4939] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Revised: 03/17/2023] [Accepted: 03/20/2023] [Indexed: 05/10/2023]
Abstract
The purpose of the current study was to investigate the effects of B0 and linear eddy currents on ultrashort echo time double echo steady state (UTE-DESS) imaging and to determine whether eddy current correction (ECC) effectively resolves imaging artifacts caused by eddy currents. 3D UTE-DESS sequences based on either projection radial or spiral cones trajectories were implemented on a 3-T clinical MR scanner. An off-isocentered thin-slice excitation approach was used to measure eddy currents. The measurements were repeated four times using two sets of tested gradient waveforms with opposite polarities and two different slice locations to measure B0 and linear eddy currents simultaneously. Computer simulation was performed to investigate the eddy current effect. Finally, a phantom experiment, an ex vivo experiment with human synovium and ankle samples, and an in vivo experiment with human knee joints, were performed to demonstrate the effects of eddy currents and ECC in UTE-DESS imaging. In a computer simulation, the two echoes (S+ and S-) in UTE-DESS imaging exhibited strong distortion at different orientations in the presence of B0 and linear eddy currents, resulting in both image degradation as well as misalignment of pixel location between the two echoes. The same phenomenon was observed in the phantom, ex vivo, and in vivo experiments, where the presence of eddy currents degraded S+, S-, echo subtraction images, and T2 maps. The implementation of ECC dramatically improved both the image quality and image registration between the S+ and S- echoes. It was concluded that ECC is crucial for reliable morphological and quantitative UTE-DESS imaging.
Collapse
Affiliation(s)
- Hyungseok Jang
- Department of Radiology, University of California, San Diego, USA
| | - Jiyo Athertya
- Department of Radiology, University of California, San Diego, USA
| | - Saeed Jerban
- Department of Radiology, University of California, San Diego, USA
| | - Yajun Ma
- Department of Radiology, University of California, San Diego, USA
| | | | - Christine B Chung
- Department of Radiology, University of California, San Diego, USA
- Radiology Service, Veterans Affairs San Diego Healthcare System, San Diego, USA
| | - Eric Y Chang
- Department of Radiology, University of California, San Diego, USA
- Radiology Service, Veterans Affairs San Diego Healthcare System, San Diego, USA
| | - Jiang Du
- Department of Radiology, University of California, San Diego, USA
- Radiology Service, Veterans Affairs San Diego Healthcare System, San Diego, USA
- Department of Bioengineering, University of California, San Diego, USA
| |
Collapse
|
3
|
Harkins KD, Ketsiri T, Nyman JS, Does MD. Fast bound and pore water mapping of cortical bone with arbitrary slice oriented two-dimensional ultra-short echo time. Magn Reson Med 2023; 89:767-773. [PMID: 36226656 PMCID: PMC9897494 DOI: 10.1002/mrm.29484] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Revised: 09/07/2022] [Accepted: 09/20/2022] [Indexed: 02/05/2023]
Abstract
PURPOSE Extend fast, two-dimensional (2D) methods of bound and pore water mapping in bone to arbitrary slice orientation. METHODS To correct for slice profile artifacts caused by gradient errors of half pulse 2D ultra-short echo time (UTE), we developed a library of predistorted gradient waveforms that can be used to interpolate optimized gradient waveforms for 2D UTE slice selection. We also developed a method to estimate and correct for a bulk phase difference between the two half pulse excitations used for 2D UTE signal excitation. Bound water images were acquired in three healthy subjects with adiabatic inversion recovery prepared 2D UTE, while pore water images were acquired after short-T2 signals were suppressed with double adiabatic inversion recovery preparation. The repeatability of bound and pore water imaging with 2D UTE was tested by repeating acquisitions after repositioning. RESULTS The library-based interpolation of optimized slice select gradient waveforms combined with the method to estimate bulk phase between two excitations provided compact slice profiles for half pulse excited 2D UTE. Quantitative bound and pore water values were highly repeatable-the pooled SD of bound water across all three subjects was 0.38 mol1 $$ {}^1 $$ H/L, while pooled SD of pore water was 0.30 mol1 $$ {}^1 $$ H/L. CONCLUSION Fast, quantitative, 2D UTE-based bound and pore water images can be acquired at arbitrary oblique orientations after correcting for errors in the slice select gradient waveform and bulk phase shift between the two half acquisitions.
Collapse
Affiliation(s)
- Kevin D Harkins
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Institute of Image Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Thammathida Ketsiri
- Institute of Image Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Jeffry S Nyman
- Institute of Image Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, Tennessee, USA
- Orthopaedic Surgery and Rehabilitation, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Center for Bone Biology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Mark D Does
- Radiology and Radiological Sciences, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Institute of Image Science, Vanderbilt University Medical Center, Nashville, Tennessee, USA
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
- Electrical Engineering, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| |
Collapse
|
4
|
Gudino N, Littin S. Advancements in Gradient System Performance for Clinical and Research MRI. J Magn Reson Imaging 2023; 57:57-70. [PMID: 36073722 DOI: 10.1002/jmri.28421] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2022] [Revised: 08/18/2022] [Accepted: 08/18/2022] [Indexed: 02/03/2023] Open
Abstract
In magnetic resonance imaging (MRI), spatial field gradients are applied along each axis to encode the location of the nuclear spin in the frequency domain. During recent years, the development of new gradient technologies has been focused on the generation of stronger and faster gradient fields for imaging with higher spatial and temporal resolution. This benefits imaging methods, such as brain diffusion and functional MRI, and enables human imaging at ultra-high field MRI. In addition to improving gradient performance, new technologies have been presented to minimize peripheral nerve stimulation and gradient-related acoustic noise, both generated by the rapid switching of strong gradient fields. This review will provide a general background on the gradient system and update on the state-of-the-art gradient technology. EVIDENCE LEVEL: 5 TECHNICAL EFFICACY: Stage 1.
Collapse
Affiliation(s)
- Natalia Gudino
- MRI Engineering Core, Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland, USA
| | - Sebastian Littin
- Medical Physics, Department of Radiology, Faculty of Medicine, University Freiburg, Freiburg, Germany
| |
Collapse
|
5
|
Hennig J, Barghoorn A, Zhang S, Zaitsev M. Single shot spiral
TSE
with annulated segmentation. Magn Reson Med 2022; 88:651-662. [DOI: 10.1002/mrm.29224] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2021] [Revised: 02/11/2022] [Accepted: 02/20/2022] [Indexed: 11/11/2022]
Affiliation(s)
- Juergen Hennig
- University Medical Center FREIBURG, Dept.of Radiology, Medical Physics Freiburg Germany
- Center for Basics in NeuroModulation (NeuroModulBasics) Faculty of Medicine, University of Freiburg Freiburg Germany
| | - Antonia Barghoorn
- University Medical Center FREIBURG, Dept.of Radiology, Medical Physics Freiburg Germany
| | - Shuoyue Zhang
- University Medical Center FREIBURG, Dept.of Radiology, Medical Physics Freiburg Germany
| | - Maxim Zaitsev
- University Medical Center FREIBURG, Dept.of Radiology, Medical Physics Freiburg Germany
| |
Collapse
|
6
|
Harkins KD, Does MD. Efficient gradient waveform measurements with variable-prephasing. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2021; 327:106945. [PMID: 33784601 PMCID: PMC8141008 DOI: 10.1016/j.jmr.2021.106945] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/25/2020] [Revised: 01/21/2021] [Accepted: 02/15/2021] [Indexed: 06/12/2023]
Abstract
Accurate measurement of gradient waveform errors can often improve image quality in sequences with time varying readout and excitation waveforms. Self-encoding or offset-slice sequences are commonly used to measure gradient waveforms. However, the self-encoding method requires a long scan time, while the offset-slice method is often low precision, requiring the thickness of the excited slice to be small compared to the maximal k-space encoded by the test waveform. This work introduces a hybrid these methods, called variable-prephasing. Using a straightforward algebraic model, we demonstrate that variable-prephasing improves the precision of the waveform measurement by allowing acquisition of larger slice thicknesses. Experiments in a phantom were used to validate the theoretical predictions, showing that the precision of variable-prephasing gradient waveform measurements improves with increasing slice thickness.
Collapse
Affiliation(s)
- Kevin D Harkins
- Biomedical Engineering, Vanderbilt University, United States; Institute of Imaging Science, Vanderbilt University, United States.
| | - Mark D Does
- Biomedical Engineering, Vanderbilt University, United States; Institute of Imaging Science, Vanderbilt University, United States
| |
Collapse
|
7
|
Kronthaler S, Rahmer J, Börnert P, Makowski MR, Schwaiger BJ, Gersing AS, Karampinos DC. Trajectory correction based on the gradient impulse response function improves high-resolution UTE imaging of the musculoskeletal system. Magn Reson Med 2020; 85:2001-2015. [PMID: 33251655 DOI: 10.1002/mrm.28566] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2020] [Revised: 09/30/2020] [Accepted: 10/02/2020] [Indexed: 12/16/2022]
Abstract
PURPOSE UTE sequences typically acquire data during the ramping up of the gradient fields, which makes UTE imaging prone to eddy current and system delay effects. The purpose of this work was to use a simple gradient impulse response function (GIRF) measurement to estimate the real readout gradient waveform and to demonstrate that precise knowledge of the gradient waveform is important in the context of high-resolution UTE musculoskeletal imaging. METHODS The GIRF was measured using the standard hardware of a 3 Tesla scanner and applied on 3D radial UTE data (TE: 0.14 ms). Experiments were performed on a phantom, in vivo on a healthy knee, and in vivo on patients with spine fractures. UTE images were reconstructed twice, first using the GIRF-corrected gradient waveforms and second using nominal-corrected waveforms, correcting for the low-pass filter characteristic of the gradient chain. RESULTS Images reconstructed with the nominal-corrected gradient waveforms exhibited blurring and showed edge artifacts. The blurring and the edge artifacts were reduced when the GIRF-corrected gradient waveforms were used, as shown in single-UTE phantom scans and in vivo dual-UTE gradient-echo scans in the knee. Further, the importance of the GIRF-based correction was indicated in UTE images of the lumbar spine, where thin bone structures disappeared when the nominal correction was employed. CONCLUSION The presented GIRF-based trajectory correction method using standard scanner hardware can improve the quality of high-resolution UTE musculoskeletal imaging.
Collapse
Affiliation(s)
- Sophia Kronthaler
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
| | | | | | - Marcus R Makowski
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
| | - Benedikt J Schwaiger
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
| | - Alexandra S Gersing
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
| | - Dimitrios C Karampinos
- Department of Diagnostic and Interventional Radiology, Technical University of Munich, Munich, Germany
| |
Collapse
|
8
|
Piredda GF, Hilbert T, Thiran JP, Kober T. Probing myelin content of the human brain with MRI: A review. Magn Reson Med 2020; 85:627-652. [PMID: 32936494 DOI: 10.1002/mrm.28509] [Citation(s) in RCA: 40] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2020] [Revised: 08/12/2020] [Accepted: 08/17/2020] [Indexed: 12/11/2022]
Abstract
Rapid and efficient transmission of electric signals among neurons of vertebrates is ensured by myelin-insulating sheaths surrounding axons. Human cognition, sensation, and motor functions rely on the integrity of these layers, and demyelinating diseases often entail serious cognitive and physical impairments. Magnetic resonance imaging radically transformed the way these disorders are monitored, offering an irreplaceable tool to noninvasively examine the brain structure. Several advanced techniques based on MRI have been developed to provide myelin-specific contrasts and a quantitative estimation of myelin density in vivo. Here, the vast offer of acquisition strategies developed to date for this task is reviewed. Advantages and pitfalls of the different approaches are compared and discussed.
Collapse
Affiliation(s)
- Gian Franco Piredda
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland.,Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Tom Hilbert
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland.,Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Jean-Philippe Thiran
- Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| | - Tobias Kober
- Advanced Clinical Imaging Technology, Siemens Healthcare AG, Lausanne, Switzerland.,Department of Radiology, Lausanne University Hospital and University of Lausanne, Lausanne, Switzerland.,LTS5, École Polytechnique Fédérale de Lausanne, Lausanne, Switzerland
| |
Collapse
|
9
|
Latta P, Starčuk Z, Kojan M, Gruwel MLH, Tomanek B, Trattnig S, Juras V. Simple compensation method for improved half-pulse excitation profile with rephasing gradient. Magn Reson Med 2020; 84:1796-1805. [PMID: 32129544 DOI: 10.1002/mrm.28233] [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: 11/04/2019] [Revised: 01/14/2020] [Accepted: 02/07/2020] [Indexed: 12/21/2022]
Abstract
PURPOSE To improve the slice profile quality obtained by RF half-pulse excitation for 2D-UTE applications. METHODS The overall first-order and zero-order phase errors along the slice-selection direction were obtained with the help of an optimization task to minimize the out-of-slice signal contamination from the calibration 1-dimenisonal (1D) profile data. The time-phase-error evolution was approximated from the k-space readout data, which were acquired primarily for correction of the readout trajectories during data regridding to the rectilinear grids. The correction of the slice profile was achieved by rephasing gradient pulses applied immediately after the end of excitation. The total prescan calibration typically took less than 2 minutes. RESULTS The improved image quality using the proposed calibration method was demonstrated both on phantoms and on ankle images obtained from healthy volunteers. It was demonstrated that calibration can be performed either as a separate water phantom measurement or directly as a prescan procedure. CONCLUSION The slice-profile distortion from the half-pulse excitation could substantially affect the overall fidelity of 2D-UTE images. The presented experiments proved that the image quality could be substantially increased by application of the proposed slice-correction method.
Collapse
Affiliation(s)
- Peter Latta
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Zenon Starčuk
- Institute of Scientific Instruments of the Czech Academy of Sciences, Brno, Czech Republic
| | - Martin Kojan
- Central European Institute of Technology, Masaryk University, Brno, Czech Republic
| | - Marco L H Gruwel
- Biological Resources Imaging Laboratory, Mark Wainwright Analytical Centre, Lowy Cancer Research Centre, University of New South Wales, Sydney, NSW, Australia
| | - Boguslaw Tomanek
- Department of Oncology, Division of Medical Physics, University of Alberta, Edmonton, AB, Canada
| | - Siegfried Trattnig
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria
| | - Vladimir Juras
- High-Field MR Centre, Department of Biomedical Imaging and Image-Guided Therapy, Medical University of Vienna, Vienna, Austria
| |
Collapse
|
10
|
Weiger M, Pruessmann KP. Short-T 2 MRI: Principles and recent advances. PROGRESS IN NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY 2019; 114-115:237-270. [PMID: 31779882 DOI: 10.1016/j.pnmrs.2019.07.001] [Citation(s) in RCA: 37] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/04/2019] [Revised: 07/14/2019] [Accepted: 07/26/2019] [Indexed: 06/10/2023]
Abstract
Among current modalities of biomedical and diagnostic imaging, MRI stands out by virtue of its versatile contrast obtained without ionizing radiation. However, in various cases, e.g., water protons in tissues such as bone, tendon, and lung, MRI performance is limited by the rapid decay of resonance signals associated with short transverse relaxation times T2 or T2*. Efforts to address this shortcoming have led to a variety of specialized short-T2 techniques. Recent progress in this field expands the choice of methods and prompts fresh considerations with regard to instrumentation, data acquisition, and signal processing. In this review, the current status of short-T2 MRI is surveyed. In an attempt to structure the growing range of techniques, the presentation highlights overarching concepts and basic methodological options. The most frequently used approaches are described in detail, including acquisition strategies, image reconstruction, hardware requirements, means of introducing contrast, sources of artifacts, limitations, and applications.
Collapse
Affiliation(s)
- Markus Weiger
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland.
| | - Klaas P Pruessmann
- Institute for Biomedical Engineering, ETH Zurich and University of Zurich, Zurich, Switzerland
| |
Collapse
|
11
|
Aigner CS, Rund A, Abo Seada S, Price AN, Hajnal JV, Malik SJ, Kunisch K, Stollberger R. Time optimal control-based RF pulse design under gradient imperfections. Magn Reson Med 2019; 83:561-574. [PMID: 31441536 PMCID: PMC6899978 DOI: 10.1002/mrm.27955] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2019] [Revised: 07/25/2019] [Accepted: 07/29/2019] [Indexed: 12/15/2022]
Abstract
Purpose This study incorporates a gradient system imperfection model into an optimal control framework for radio frequency (RF) pulse design. Theory and Methods The joint design of minimum‐time RF and slice selective gradient shapes is posed as an optimal control problem. Hardware limitations such as maximal amplitudes for RF and slice selective gradient or its slew rate are included as hard constraints to assure practical applicability of the optimized waveforms. In order to guarantee the performance of the optimized waveform with possible gradient system disturbances such as limited system bandwidth and eddy currents, a measured gradient impulse response function (GIRF) for a specific system is integrated into the optimization. Results The method generates optimized RF and pre‐distorted slice selective gradient shapes for refocusing that are able to fully compensate the modeled imperfections of the gradient system under investigation. The results nearly regenerate the optimal results of an idealized gradient system. The numerical Bloch simulations are validated by phantom and in‐vivo experiments on 2 3T scanners. Conclusions The presented design approach demonstrates the successful correction of gradient system imperfections within an optimal control framework for RF pulse design.
Collapse
Affiliation(s)
- Christoph S Aigner
- Institute of Medical Engineering, Graz University of Technology, Graz, Austria
| | - Armin Rund
- Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria
| | - Samy Abo Seada
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Anthony N Price
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Joseph V Hajnal
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Shaihan J Malik
- School of Biomedical Engineering and Imaging Sciences, King's College London, London, United Kingdom
| | - Karl Kunisch
- Institute for Mathematics and Scientific Computing, University of Graz, Graz, Austria.,Johann Radon Institute for Computational and Applied Mathematics (RICAM), Austrian Academy of Sciences, Linz, Austria.,BioTechMed-Graz, Graz, Austria
| | - Rudolf Stollberger
- Institute of Medical Engineering, Graz University of Technology, Graz, Austria.,BioTechMed-Graz, Graz, Austria
| |
Collapse
|
12
|
Williams SN, Nielsen JF, Fessler JA, Noll DC. Design of spectral-spatial phase prewinding pulses and their use in small-tip fast recovery steady-state imaging. Magn Reson Med 2018; 79:1377-1386. [PMID: 28671320 PMCID: PMC5752636 DOI: 10.1002/mrm.26794] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2017] [Revised: 05/24/2017] [Accepted: 05/24/2017] [Indexed: 11/10/2022]
Abstract
PURPOSE Spectrally selective "prewinding" radiofrequency pulses can counteract B0 inhomogeneity in steady-state sequences, but can only prephase a limited range of off-resonance. We propose spectral-spatial small-tip angle prewinding pulses that increase the off-resonance bandwidth that can be successfully prephased by incorporating spatially tailored excitation patterns. THEORY AND METHODS We present a feasibility study to compare spectral and spectral-spatial prewinding pulses. These pulses add a prephasing term to the target magnetization pattern that aims to recover an assigned off-resonance bandwidth at the echo time. For spectral-spatial pulses, the design bandwidth is centered at the off-resonance frequency for each spatial location in a field map. We use these pulses in the small-tip fast recovery steady-state sequence, which is similar to balanced steady-state free precession. We investigate improvement of spectral-spatial pulses over spectral pulses using simulations and small-tip fast recovery scans of a gel phantom and human brain. RESULTS In simulation, spectral-spatial pulses yielded lower normalized root mean squared excitation error than spectral pulses. For both experiments, the spectral-spatial pulse images are also qualitatively better (more uniform, less signal loss) than the spectral pulse images. CONCLUSION Spectral-spatial prewinding pulses can prephase over a larger range of off-resonance than their purely spectral counterparts. Magn Reson Med 79:1377-1386, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Sydney N Williams
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Jon-Fredrik Nielsen
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Jeffrey A Fessler
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| | - Douglas C Noll
- Department of Biomedical Engineering, University of Michigan, Ann Arbor, Michigan, USA
| |
Collapse
|
13
|
Çavuşoğlu M, Mooiweer R, Pruessmann KP, Malik SJ. VERSE-guided parallel RF excitations using dynamic field correction. NMR IN BIOMEDICINE 2017; 30:e3697. [PMID: 28211968 PMCID: PMC5484370 DOI: 10.1002/nbm.3697] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/05/2016] [Revised: 11/24/2016] [Accepted: 12/29/2016] [Indexed: 06/06/2023]
Abstract
In parallel RF pulse design, peak RF magnitudes and specific absorption rate levels are critical concerns in the hardware and safety limits. The variable rate selective excitation (VERSE) method is an efficient technique to limit the peak RF power by applying a local-only RF and gradient waveform reshaping while retaining the on-resonance profile. The accuracy of the excitation performed by the VERSEd RF and gradient waveforms strictly depends on the performance of the employed hardware. Any deviation from the nominal gradient fields as a result of frequency dependent system imperfections violates the VERSE condition similarly to off-resonance effects, leading to significant excitation errors and the RF pulse not converging to the targeted peak RF power. Moreover, for iterative VERSE-guided RF pulse design (i.e. reVERSE), the k-space trajectory actually changes at every iteration, which is assumed to be constant. In this work, we show both theoretically and experimentally the effect of gradient system imperfections on iteratively VERSEd parallel RF excitations. In order to improve the excitation accuracy besides limiting the RF power below certain thresholds, we propose to integrate gradient field monitoring or gradient impulse response function (GIRF) estimations of the actual gradient fields into the RF pulse design problem. A third-order dynamic field camera comprising a set of NMR field sensors and GIRFs was used to measure or estimate the actual gradient waveforms that are involved in the VERSE algorithm respectively. The deviating and variable k-space is counteracted at each iteration of the VERSE-guided iterative RF pulse design. The proposed approaches are demonstrated for accelerated multiple-channel spatially selective RF pulses, and highly improved experimental performance was achieved at both 3 T and 7 T.
Collapse
Affiliation(s)
- Mustafa Çavuşoğlu
- Institute for Biomedical EngineeringUniversity and ETH ZürichZürichSwitzerland
| | - Ronald Mooiweer
- Division of Imaging Sciences and Biomedical Engineering, King's College LondonSt. Thomas' HospitalLondonUK
- Center for Image SciencesUniversity Medical Center UtrechtUtrechtThe Netherlands
| | - Klaas P. Pruessmann
- Institute for Biomedical EngineeringUniversity and ETH ZürichZürichSwitzerland
| | - Shaihan J. Malik
- Division of Imaging Sciences and Biomedical Engineering, King's College LondonSt. Thomas' HospitalLondonUK
| |
Collapse
|
14
|
Çavuşoğlu M, Dietrich BE, Brunner DO, Weiger M, Pruessmann KP. Correction of parallel transmission using concurrent RF and gradient field monitoring. MAGNETIC RESONANCE MATERIALS IN PHYSICS BIOLOGY AND MEDICINE 2017; 30:473-488. [DOI: 10.1007/s10334-017-0620-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2016] [Revised: 03/27/2017] [Accepted: 04/10/2017] [Indexed: 10/19/2022]
|
15
|
Lankford CL, Does MD. Propagation of error from parameter constraints in quantitative MRI: Example application of multiple spin echo T 2 mapping. Magn Reson Med 2017; 79:673-682. [PMID: 28426147 DOI: 10.1002/mrm.26713] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2016] [Revised: 03/21/2017] [Accepted: 03/23/2017] [Indexed: 12/20/2022]
Abstract
PURPOSE Quantitative MRI may require correcting for nuisance parameters which can or must be constrained to independently measured or assumed values. The noise and/or bias in these constraints propagate to fitted parameters. For example, the case of refocusing pulse flip angle constraint in multiple spin echo T2 mapping is explored. METHODS An analytical expression for the mean-squared error of a parameter of interest was derived as a function of the accuracy and precision of an independent estimate of a nuisance parameter. The expression was validated by simulations and then used to evaluate the effects of flip angle (θ) constraint on the accuracy and precision of T⁁2 for a variety of multi-echo T2 mapping protocols. RESULTS Constraining θ improved T⁁2 precision when the θ-map signal-to-noise ratio was greater than approximately one-half that of the first spin echo image. For many practical scenarios, constrained fitting was calculated to reduce not just the variance but the full mean-squared error of T⁁2, for bias in θ⁁≲6%. CONCLUSION The analytical expression derived in this work can be applied to inform experimental design in quantitative MRI. The example application to T2 mapping provided specific cases, depending on θ⁁ accuracy and precision, in which θ⁁ measurement and constraint would be beneficial to T⁁2 variance or mean-squared error. Magn Reson Med 79:673-682, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Christopher L Lankford
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
| | - Mark D Does
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
16
|
Ma J, Wismans C, Cao Z, Klomp DWJ, Wijnen JP, Grissom WA. Tailored spiral in-out spectral-spatial water suppression pulses for magnetic resonance spectroscopic imaging. Magn Reson Med 2017; 79:31-40. [PMID: 28370494 DOI: 10.1002/mrm.26683] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2016] [Revised: 02/02/2017] [Accepted: 02/28/2017] [Indexed: 11/10/2022]
Abstract
PURPOSE To develop short water suppression sequences for 7 T magnetic resonance spectroscopic imaging, with mitigation of subject-specific transmit RF field ( B1+) inhomogeneity. METHODS Patient-tailored spiral in-out spectral-spatial saturation pulses were designed for a three-pulse WET water suppression sequence. The pulses' identical spatial subpulses were designed using patient-specific B1+ maps and a spiral in-out excitation k-space trajectory. The subpulse train was weighted by a spectral envelope that was root-flipped to minimize peak RF demand. The pulses were validated in in vivo experiments that acquired high resolution magnetic resonance spectroscopic imaging data, using a crusher coil for fast lipid suppression. Residual water signals and MR spectra were compared between the proposed tailored sequence and a conventional WET sequence. RESULTS Replacing conventional spectrally-selective pulses with tailored spiral in-out spectral-spatial pulses reduced mean water residual from 5.88 to 2.52% (57% improvement). Pulse design time was less then 0.4 s. The pulses' specific absorption rate were compatible with magnetic resonance spectroscopic imaging TRs under 300 ms, which enabled spectra of fine in plane spatial resolution (5 mm) with good quality to be measured in 7.5 min. CONCLUSION Tailored spiral in-out spectral-spatial water suppression enables efficient high resolution magnetic resonance spectroscopic imaging in the brain. Magn Reson Med 79:31-40, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Jun Ma
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Carrie Wismans
- Department of Radiology, University Medical Centre Utrecht, Utrecht, the Netherlands
| | - Zhipeng Cao
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Dennis W J Klomp
- Department of Radiology, University Medical Centre Utrecht, Utrecht, the Netherlands
| | - Jannie P Wijnen
- Department of Radiology, University Medical Centre Utrecht, Utrecht, the Netherlands
| | - William A Grissom
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
17
|
Manhard MK, Nyman JS, Does MD. Advances in imaging approaches to fracture risk evaluation. Transl Res 2017; 181:1-14. [PMID: 27816505 PMCID: PMC5357194 DOI: 10.1016/j.trsl.2016.09.006] [Citation(s) in RCA: 48] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/15/2016] [Revised: 09/19/2016] [Accepted: 09/27/2016] [Indexed: 01/23/2023]
Abstract
Fragility fractures are a growing problem worldwide, and current methods for diagnosing osteoporosis do not always identify individuals who require treatment to prevent a fracture and may misidentify those not a risk. Traditionally, fracture risk is assessed using dual-energy X-ray absorptiometry, which provides measurements of areal bone mineral density at sites prone to fracture. Recent advances in imaging show promise in adding new information that could improve the prediction of fracture risk in the clinic. As reviewed herein, advances in quantitative computed tomography (QCT) predict hip and vertebral body strength; high-resolution HR-peripheral QCT (HR-pQCT) and micromagnetic resonance imaging assess the microarchitecture of trabecular bone; quantitative ultrasound measures the modulus or tissue stiffness of cortical bone; and quantitative ultrashort echo-time MRI methods quantify the concentrations of bound water and pore water in cortical bone, which reflect a variety of mechanical properties of bone. Each of these technologies provides unique characteristics of bone and may improve fracture risk diagnoses and reduce prevalence of fractures by helping to guide treatment decisions.
Collapse
Affiliation(s)
- Mary Kate Manhard
- Biomedical Engineering, Vanderbilt University, Nashville, TN; Vanderbilt University Institute of Imaging Science, Nashville, TN
| | - Jeffry S Nyman
- Biomedical Engineering, Vanderbilt University, Nashville, TN; Vanderbilt University Institute of Imaging Science, Nashville, TN; Orthopaedic Surgery and Rehabilitation, Vanderbilt University, Nashville, TN; Tennessee Valley Healthcare System, Department of Veterans Affairs, Nashville, TN; Center for Bone Biology, Vanderbilt University Medical Center, Nashville, TN
| | - Mark D Does
- Biomedical Engineering, Vanderbilt University, Nashville, TN; Vanderbilt University Institute of Imaging Science, Nashville, TN; Radiology and Radiological Sciences, Vanderbilt University, Nashville, TN; Electrical Engineering, Vanderbilt University, Nashville, TN.
| |
Collapse
|
18
|
Krafft AJ, Loeffler RB, Song R, Tipirneni-Sajja A, McCarville MB, Robson MD, Hankins JS, Hillenbrand CM. Quantitative ultrashort echo time imaging for assessment of massive iron overload at 1.5 and 3 Tesla. Magn Reson Med 2017; 78:1839-1851. [PMID: 28090666 DOI: 10.1002/mrm.26592] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2016] [Revised: 11/30/2016] [Accepted: 12/01/2016] [Indexed: 01/12/2023]
Abstract
PURPOSE Hepatic iron content (HIC) quantification via transverse relaxation rate (R2*)-MRI using multi-gradient echo (mGRE) imaging is compromised toward high HIC or at higher fields due to the rapid signal decay. Our study aims at presenting an optimized 2D ultrashort echo time (UTE) sequence for R2* quantification to overcome these limitations. METHODS Two-dimensional UTE imaging was realized via half-pulse excitation and radial center-out sampling. The sequence includes chemically selective saturation pulses to reduce streaking artifacts from subcutaneous fat, and spatial saturation (sSAT) bands to suppress out-of-slice signals. The sequence employs interleaved multi-echo readout trains to achieve dense temporal sampling of rapid signal decays. Evaluation was done at 1.5 Tesla (T) and 3T in phantoms, and clinical applicability was demonstrated in five patients with biopsy-confirmed massively high HIC levels (>25 mg Fe/g dry weight liver tissue). RESULTS In phantoms, the sSAT pulses were found to remove out-of-slice contamination, and R2* results were in excellent agreement to reference mGRE R2* results (slope of linear regression: 1.02/1.00 for 1.5/3T). UTE-based R2* quantification in patients with massive iron overload proved successful at both field strengths and was consistent with biopsy HIC values. CONCLUSION The UTE sequence provides a means to measure R2* in patients with massive iron overload, both at 1.5T and 3T. Magn Reson Med 78:1839-1851, 2017. © 2017 Wiley Periodicals, Inc.
Collapse
Affiliation(s)
- Axel J Krafft
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA.,Department of Radiology, Medical Physics, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Ralf B Loeffler
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Ruitian Song
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Aaryani Tipirneni-Sajja
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - M Beth McCarville
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Matthew D Robson
- OCMR, Radcliffe Department of Medicine, University of Oxford, Oxford, United Kingdom
| | - Jane S Hankins
- Department of Hematology, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| | - Claudia M Hillenbrand
- Department of Diagnostic Imaging, St. Jude Children's Research Hospital, Memphis, Tennessee, USA
| |
Collapse
|
19
|
Manhard MK, Harkins KD, Gochberg DF, Nyman JS, Does MD. 30-Second bound and pore water concentration mapping of cortical bone using 2D UTE with optimized half-pulses. Magn Reson Med 2017; 77:945-950. [PMID: 28090655 DOI: 10.1002/mrm.26605] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 11/18/2016] [Accepted: 12/21/2016] [Indexed: 11/09/2022]
Abstract
PURPOSE MRI of cortical bone has the potential to offer new information about fracture risk. Current methods are typically performed with 3D acquisitions, which suffer from long scan times and are generally limited to extremities. This work proposes using 2D UTE with half pulses for quantitatively mapping bound and pore water in cortical bone. METHODS Half-pulse 2D UTE methods were implemented on a 3T Philips Achieva scanner using an optimized slice-select gradient waveform, with preparation pulses to selectively image bound or pore water. The 2D methods were quantitatively compared with previously implemented 3D methods in the tibia in five volunteers. RESULTS The mean difference between bound and pore water concentration acquired from 3D and 2D sequences was 0.6 and 0.9 mol 1 H/Lbone (3 and 12%, respectively). While 2D pore water methods tended to slightly overestimate concentrations relative to 3D methods, differences were less than scan-rescan uncertainty and expected differences between healthy and fracture-prone bones. CONCLUSION Quantitative bound and pore water concentration mapping in cortical bone can be accelerated by 2 orders of magnitude using 2D protocols with optimized half-pulse excitation. Magn Reson Med 77:945-950, 2017. © 2017 International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Mary Kate Manhard
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
| | - Kevin D Harkins
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA
| | - Daniel F Gochberg
- Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee, USA
| | - Jeffry S Nyman
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Department of Veterans Affairs, Tennessee Valley Healthcare System, Nashville, Tennessee, USA.,Orthopaedic Surgery and Rehabilitation, Vanderbilt University, Nashville, Tennessee, USA.,Center for Bone Biology, Vanderbilt University Medical Center, Nashville, Tennessee, USA
| | - Mark D Does
- Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Vanderbilt University Institute of Imaging Science, Nashville, Tennessee, USA.,Radiology and Radiological Sciences, Vanderbilt University, Nashville, Tennessee, USA.,Electrical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|
20
|
Padormo F, Beqiri A, Hajnal JV, Malik SJ. Parallel transmission for ultrahigh-field imaging. NMR IN BIOMEDICINE 2016; 29:1145-61. [PMID: 25989904 PMCID: PMC4995736 DOI: 10.1002/nbm.3313] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/29/2014] [Revised: 03/27/2015] [Accepted: 03/29/2015] [Indexed: 05/24/2023]
Abstract
The development of MRI systems operating at or above 7 T has provided researchers with a new window into the human body, yielding improved imaging speed, resolution and signal-to-noise ratio. In order to fully realise the potential of ultrahigh-field MRI, a range of technical hurdles must be overcome. The non-uniformity of the transmit field is one of such issues, as it leads to non-uniform images with spatially varying contrast. Parallel transmission (i.e. the use of multiple independent transmission channels) provides previously unavailable degrees of freedom that allow full spatial and temporal control of the radiofrequency (RF) fields. This review discusses the many ways in which these degrees of freedom can be used, ranging from making more uniform transmit fields to the design of subject-tailored RF pulses for both uniform excitation and spatial selection, and also the control of the specific absorption rate. © 2015 The Authors. NMR in Biomedicine published by John Wiley & Sons Ltd.
Collapse
Affiliation(s)
- Francesco Padormo
- Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St Thomas' Hospital, London, UK
| | - Arian Beqiri
- Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St Thomas' Hospital, London, UK
| | - Joseph V Hajnal
- Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St Thomas' Hospital, London, UK
- Centre for the Developing Brain, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St Thomas' Hospital, London, UK
| | - Shaihan J Malik
- Department of Biomedical Engineering, Division of Imaging Sciences and Biomedical Engineering, King's College London, King's Health Partners, St Thomas' Hospital, London, UK
| |
Collapse
|
21
|
Malik SJ, Hajnal JV. Phase relaxed localized excitation pulses for inner volume fast spin echo imaging. Magn Reson Med 2016; 76:848-61. [PMID: 26451691 PMCID: PMC4988531 DOI: 10.1002/mrm.25996] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2015] [Revised: 08/20/2015] [Accepted: 08/30/2015] [Indexed: 11/25/2022]
Abstract
PURPOSE To design multidimensional spatially selective radiofrequency (RF) pulses for inner volume imaging (IVI) with three-dimensional (3D) fast spin echo (FSE) sequences. Enhanced background suppression is achieved by exploiting particular signal properties of FSE sequences. THEORY AND METHODS The CPMG condition dictates that echo amplitudes will rapidly decrease if a 90° phase difference between excitation and refocusing pulses is not present, and refocusing flip angles are not precisely 180°. This mechanism is proposed as a means for generating additional background suppression for spatially selective excitation, by biasing residual excitation errors toward violating the CPMG condition. 3D RF pulses were designed using this method with a 3D spherical spiral trajectory, under-sampled by factor 5.6 for an eight-channel PTx system, at 3 Tesla. RESULTS 3D-FSE IVI with pulse durations of approximately 12 ms was demonstrated in phantoms and for T2 -weighted brain imaging in vivo. Good image quality was obtained, with mean background suppression factors of 103 and 82 ± 6 in phantoms and in vivo, respectively. CONCLUSION Inner Volume Imaging with 3D-FSE has been demonstrated in vivo with tailored 3D-RF pulses. The proposed design methods are also applicable to 2D pulses. Magn Reson Med 76:848-861, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.
Collapse
Affiliation(s)
- Shaihan J. Malik
- Biomedical Engineering Department, Division of Imaging Sciences, King's College LondonSt. Thomas' HospitalLondonUnited Kingdom
| | - Joseph V. Hajnal
- Biomedical Engineering Department, Division of Imaging Sciences, King's College LondonSt. Thomas' HospitalLondonUnited Kingdom
| |
Collapse
|
22
|
Manhard MK, Horch RA, Gochberg DF, Nyman JS, Does MD. In Vivo Quantitative MR Imaging of Bound and Pore Water in Cortical Bone. Radiology 2015; 277:221-9. [PMID: 26020434 DOI: 10.1148/radiol.2015140336] [Citation(s) in RCA: 48] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
PURPOSE To translate and evaluate an in vivo magnetic resonance (MR) imaging protocol for quantitative mapping of collagen-bound and pore water concentrations in cortical bone that involves relaxation-selective ultrashort echo time (UTE) methods. MATERIALS AND METHODS All HIPAA-compliant studies were performed with institutional review board approval and written informed consent. UTE imaging sequences were implemented on a clinical 3.0-T MR imaging unit and were used for in vivo imaging of bound and pore water in cortical bone. Images of the lower leg and wrist were acquired in five volunteers each (lower leg: two men and three women aged 24, 24, 49, 30, and 26 years; wrist: two men and three women aged 31, 23, 25, 24, and 26 years) to generate bound and pore water concentration maps of the tibia and radius. Each volunteer was imaged three times, and the standard error of the measurements at the region-of-interest (ROI) level was computed as the standard deviation across studies, pooled across volunteers and ROIs. RESULTS Quantitative bound and pore water maps in the tibia and radius, acquired in 8-14 minutes, had per-voxel signal-to-noise ratios of 18 (bound water) and 14 (pore water) and inter-study standard errors of approximately 2 mol (1)H per liter of bone at the ROI level. CONCLUSION The results of this study demonstrate the feasibility of quantitatively mapping bound and pore water in vivo in human cortical bone with practical human MR imaging constraints.
Collapse
Affiliation(s)
- Mary Kate Manhard
- From the Departments of Biomedical Engineering (M.K.H., M.D.D.), Radiology (R.A.H., D.F.G.), and Orthopedic Surgery and Rehabilitation (J.S.N.), Vanderbilt University, 1161 21st Ave S, AA-1105 MCN, Nashville, TN 37232-2310
| | - R Adam Horch
- From the Departments of Biomedical Engineering (M.K.H., M.D.D.), Radiology (R.A.H., D.F.G.), and Orthopedic Surgery and Rehabilitation (J.S.N.), Vanderbilt University, 1161 21st Ave S, AA-1105 MCN, Nashville, TN 37232-2310
| | - Daniel F Gochberg
- From the Departments of Biomedical Engineering (M.K.H., M.D.D.), Radiology (R.A.H., D.F.G.), and Orthopedic Surgery and Rehabilitation (J.S.N.), Vanderbilt University, 1161 21st Ave S, AA-1105 MCN, Nashville, TN 37232-2310
| | - Jeffry S Nyman
- From the Departments of Biomedical Engineering (M.K.H., M.D.D.), Radiology (R.A.H., D.F.G.), and Orthopedic Surgery and Rehabilitation (J.S.N.), Vanderbilt University, 1161 21st Ave S, AA-1105 MCN, Nashville, TN 37232-2310
| | - Mark D Does
- From the Departments of Biomedical Engineering (M.K.H., M.D.D.), Radiology (R.A.H., D.F.G.), and Orthopedic Surgery and Rehabilitation (J.S.N.), Vanderbilt University, 1161 21st Ave S, AA-1105 MCN, Nashville, TN 37232-2310
| |
Collapse
|
23
|
Sharma A, Bammer R, Stenger VA, Grissom WA. Low peak power multiband spokes pulses for B1 (+) inhomogeneity-compensated simultaneous multislice excitation in high field MRI. Magn Reson Med 2014; 74:747-55. [PMID: 25203620 DOI: 10.1002/mrm.25455] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2014] [Revised: 08/20/2014] [Accepted: 08/21/2014] [Indexed: 11/11/2022]
Abstract
PURPOSE To design low peak and integrated power simultaneous multislice excitation radiofrequency pulses with transmit field inhomogeneity compensation in high field MRI. THEORY AND METHODS The "interleaved greedy and local optimization" algorithm for small-tip-angle spokes pulses is extended to design multiband (MB) spokes pulses that simultaneously excite multiple slices, with independent spokes weight optimization for each slice. The peak power of the pulses is controlled using a slice phase optimization technique. Simulations were performed at 7T to compare the peak power of optimized MB spokes pulses to unoptimized pulses, and to compare the proposed slice-independent spokes weight optimization to a joint approach. In vivo experiments were performed at 7T to validate the pulse's function and compare them to conventional MB pulses. RESULTS Simulations showed that the peak power-minimized pulses had lower peak power than unregularized and integrated power-regularized pulses, and that the slice-independent spokes weight optimization consistently produced lower flip angle inhomogeneity and lower peak and integrated power pulses. In the brain imaging experiments, the MB spokes pulses showed significant improvement in excitation flip angle and subsequently signal homogeneity compared to conventional MB pulses. CONCLUSION The proposed MB spokes pulses improve flip angle homogeneity in simultaneous multislice acquisitions at ultrahigh field, with minimal increase in integrated and peak radiofrequency power.
Collapse
Affiliation(s)
- Anuj Sharma
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA
| | - Roland Bammer
- Department of Radiology, Stanford University, Stanford, California, USA
| | - V Andrew Stenger
- Department of Medicine, University of Hawaii, Honolulu, Hawaii, USA
| | - William A Grissom
- Vanderbilt University Institute of Imaging Science, Vanderbilt University, Nashville, Tennessee, USA.,Department of Biomedical Engineering, Vanderbilt University, Nashville, Tennessee, USA.,Department of Radiology, Vanderbilt University, Nashville, Tennessee, USA
| |
Collapse
|