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Versteeg E, Liu H, van der Heide O, Fuderer M, van den Berg CAT, Sbrizzi A. High SNR full brain relaxometry at 7T by accelerated MR-STAT. Magn Reson Med 2024; 92:226-235. [PMID: 38326909 DOI: 10.1002/mrm.30052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2023] [Revised: 12/21/2023] [Accepted: 01/26/2024] [Indexed: 02/09/2024]
Abstract
PURPOSE To demonstrate the feasibility and robustness of the Magnetic Resonance Spin TomogrAphy in Time-domain (MR-STAT) framework for fast, high SNR relaxometry at 7T. METHODS To deploy MR-STAT on 7T-systems, we designed optimized flip-angles using the BLAKJac-framework that incorporates the SAR-constraints. Transmit RF-inhomogeneities were mitigated by including a measuredB 1 + $$ {B}_1^{+} $$ -map in the reconstruction. Experiments were performed on a gel-phantom and on five volunteers to explore the robustness of the sequence and its sensitivity toB 1 + $$ {B}_1^{+} $$ inhomogeneities. The SNR-gain at 7T was explored by comparing phantom and in vivo results to MR-STAT at 3T in terms of SNR-efficiency. RESULTS The higher SNR at 7T enabled two-fold acceleration with respect to current 2D MR-STAT protocols at lower field strengths. The resulting scan had whole-brain coverage, with 1 x 1 x 3 mm3 resolution (1.5 mm slice-gap) and was acquired within 3 min including theB 1 + $$ {B}_1^{+} $$ -mapping. AfterB 1 + $$ {B}_1^{+} $$ -correction, the estimated T1 and T2 in a phantom showed a mean relative error of, respectively, 1.7% and 4.4%. In vivo, the estimated T1 and T2 in gray and white matter corresponded to the range of values reported in literature with a variation over the subjects of 1.0%-2.1% (WM-GM) for T1 and 4.3%-5.3% (WM-GM) for T2. We measured a higher SNR-efficiency at 7T (R = 2) than at 3T for both T1 and T2 with, respectively, a 4.1 and 2.3 times increase in SNR-efficiency. CONCLUSION We presented an accelerated version of MR-STAT tailored to high field (7T) MRI using a low-SAR flip-angle train and showed high quality parameter maps with an increased SNR-efficiency compared to MR-STAT at 3T.
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Affiliation(s)
- Edwin Versteeg
- Computational Imaging Group, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Hongyan Liu
- Computational Imaging Group, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Oscar van der Heide
- Computational Imaging Group, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Miha Fuderer
- Computational Imaging Group, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Computational Imaging Group, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alessandro Sbrizzi
- Computational Imaging Group, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
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Versteeg E, Nam KM, Klomp DWJ, Bhogal AA, Siero JCW, Wijnen JP. A silent echo-planar spectroscopic imaging readout with high spectral bandwidth MRSI using an ultrasonic gradient axis. Magn Reson Med 2024; 91:2247-2256. [PMID: 38205917 DOI: 10.1002/mrm.30008] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2023] [Revised: 12/18/2023] [Accepted: 12/21/2023] [Indexed: 01/12/2024]
Abstract
PURPOSE We present a novel silent echo-planar spectroscopic imaging (EPSI) readout, which uses an ultrasonic gradient insert to accelerate MRSI while producing a high spectral bandwidth (20 kHz) and a low sound level. METHODS The ultrasonic gradient insert consisted of a single-axis (z-direction) plug-and-play gradient coil, powered by an audio amplifier, and produced 40 mT/m at 20 kHz. The silent EPSI readout was implemented in a phase-encoded MRSI acquisition. Here, the additional spatial encoding provided by this silent EPSI readout was used to reduce the number of phase-encoding steps. Spectroscopic acquisitions using phase-encoded MRSI, a conventional EPSI-readout, and the silent EPSI readout were performed on a phantom containing metabolites with resonance frequencies in the ppm range of brain metabolites (0-4 ppm). These acquisitions were used to determine sound levels, showcase the high spectral bandwidth of the silent EPSI readout, and determine the SNR efficiency and the scan efficiency. RESULTS The silent EPSI readout featured a 19-dB lower sound level than a conventional EPSI readout while featuring a high spectral bandwidth of 20 kHz without spectral ghosting artifacts. Compared with phase-encoded MRSI, the silent EPSI readout provided a 4.5-fold reduction in scan time. In addition, the scan efficiency of the silent EPSI readout was higher (82.5% vs. 51.5%) than the conventional EPSI readout. CONCLUSIONS We have for the first time demonstrated a silent spectroscopic imaging readout with a high spectral bandwidth and low sound level. This sound reduction provided by the silent readout is expected to have applications in sound-sensitive patient groups, whereas the high spectral bandwidth could benefit ultrahigh-field MR systems.
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Affiliation(s)
- Edwin Versteeg
- Center for Image Sciences, Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Kyung Min Nam
- Center for Image Sciences, Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Dennis W J Klomp
- Center for Image Sciences, Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alex A Bhogal
- Center for Image Sciences, Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeroen C W Siero
- Center for Image Sciences, Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
- Spinoza Centre for Neuroimaging, Amsterdam, Netherlands
| | - Jannie P Wijnen
- Center for Image Sciences, Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
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Liu H, van der Heide O, Versteeg E, Froeling M, Fuderer M, Xu F, van den Berg CAT, Sbrizzi A. A three-dimensional Magnetic Resonance Spin Tomography in Time-domain protocol for high-resolution multiparametric quantitative magnetic resonance imaging. NMR Biomed 2024; 37:e5050. [PMID: 37857335 DOI: 10.1002/nbm.5050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/10/2023] [Revised: 08/04/2023] [Accepted: 09/11/2023] [Indexed: 10/21/2023]
Abstract
Magnetic Resonance Spin TomogrAphy in Time-domain (MR-STAT) is a multiparametric quantitative MR framework, which allows for simultaneously acquiring quantitative tissue parameters such as T1, T2, and proton density from one single short scan. A typical two-dimensional (2D) MR-STAT acquisition uses a gradient-spoiled, gradient-echo sequence with a slowly varying RF flip-angle train and Cartesian readouts, and the quantitative tissue maps are reconstructed by an iterative, model-based optimization algorithm. In this work, we design a three-dimensional (3D) MR-STAT framework based on previous 2D work, in order to achieve better image signal-to-noise ratio, higher though-plane resolution, and better tissue characterization. Specifically, we design a 7-min, high-resolution 3D MR-STAT sequence, and the corresponding two-step reconstruction algorithm for the large-scale dataset. To reduce the long acquisition time, Cartesian undersampling strategies such as SENSE are adopted in our transient-state quantitative framework. To reduce the computational burden, a data-splitting scheme is designed for decoupling the 3D reconstruction problem into independent 2D reconstructions. The proposed 3D framework is validated by numerical simulations, phantom experiments, and in vivo experiments. High-quality knee quantitative maps with 0.8 × 0.8 × 1.5 mm3 resolution and bilateral lower leg maps with 1.6 mm isotropic resolution can be acquired using the proposed 7-min acquisition sequence and the 3-min-per-slice decoupled reconstruction algorithm. The proposed 3D MR-STAT framework could have wide clinical applications in the future.
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Affiliation(s)
- Hongyan Liu
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Oscar van der Heide
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Edwin Versteeg
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Martijn Froeling
- Department of Radiology, Imaging Division, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Miha Fuderer
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Fei Xu
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cornelis A T van den Berg
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Alessandro Sbrizzi
- Computational Imaging Group for MRI Therapy & Diagnostics, Department of Radiotherapy, University Medical Center Utrecht, Utrecht, The Netherlands
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Jacobs SM, Versteeg E, van der Kolk AG, Visser LNC, Oliveira ÍAF, van Maren E, Klomp DWJ, Siero JCW. Image quality and subject experience of quiet T1-weighted 7-T brain imaging using a silent gradient coil. Eur Radiol Exp 2022; 6:36. [PMID: 36042139 PMCID: PMC9428090 DOI: 10.1186/s41747-022-00293-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2022] [Accepted: 06/16/2022] [Indexed: 11/17/2022] Open
Abstract
Objectives Acoustic noise in magnetic resonance imaging (MRI) negatively impacts patients. We assessed a silent gradient coil switched at 20 kHz combined with a T1-weighted magnetisation prepared rapid gradient-echo (MPRAGE) sequence at 7 T. Methods Five healthy subjects (21–29 years; three females) without previous 7-T MRI experience underwent both a quiet MPRAGE (Q-MPRAGE) and conventional MPRAGE (C-MPRAGE) sequence twice. Image quality was assessed quantitatively, and qualitatively by two neuroradiologists. Sound level was measured objectively and rated subjectively on a 0 to 10 scale by all subjects immediately following each sequence and after the whole examination (delayed). All subjects also reported comfort level, overall experience and willingness to undergo the sequence again. Results Compared to C-MPRAGE, Q-MPRAGE showed higher signal-to-noise ratio (10%; p = 0.012) and lower contrast-to-noise ratio (20%; p < 0.001) as well as acceptable to good image quality. Q-MPRAGE produced 27 dB lower sound level (76 versus 103 dB). Subjects reported lower sound level for Q-MPRAGE both immediate (4.4 ± 1.4 versus 6.4 ± 1.3; p = 0.007) and delayed (4.6 ± 1.4 versus 6.3 ± 1.3; p = 0.005), while they rated comfort level (7.4 ± 1.0 versus 6.1 ± 1.7; p = 0.016) and overall experience (7.6 ± 1.0 versus 6.0 ± 0.9; p = 0.005) higher. Willingness to undergo the sequence again was also higher, however not significantly (8.1 ± 1.0 versus 7.2 ± 1.3; p = 0.066). Conclusion Q-MPRAGE using a silent gradient coil reduced sound level by 27 dB compared to C-MPRAGE at 7 T while featuring acceptable-to-good image quality and a quieter and more pleasant subject experience.
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Affiliation(s)
- Sarah M Jacobs
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, the Netherlands.
| | - Edwin Versteeg
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, the Netherlands.
| | - Anja G van der Kolk
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, the Netherlands.,Department of Medical Imaging, Radboud University Medical Center, Nijmegen, the Netherlands
| | - Leonie N C Visser
- Department of Neurology, Alzheimer Center Amsterdam, Amsterdam Neuroscience, Vrije Universiteit Amsterdam, Amsterdam UMC, Amsterdam, the Netherlands.,Division of Clinical Geriatrics, Department of Neurobiology, Care Sciences and Society, Center for Alzheimer Research, Karolinska Institute, Stockholm, Sweden
| | - Ícaro A F Oliveira
- Spinoza Centre for Neuroimaging Amsterdam, Amsterdam, the Netherlands.,Experimental and Applied Psychology, VU University, Amsterdam, the Netherlands
| | - Emiel van Maren
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Dennis W J Klomp
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, the Netherlands
| | - Jeroen C W Siero
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, the Netherlands.,Spinoza Centre for Neuroimaging Amsterdam, Amsterdam, the Netherlands
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Versteeg E, Klomp DWJ, Siero JCW. Accelerating Brain Imaging Using a Silent Spatial Encoding Axis. Magn Reson Med 2022; 88:1785-1793. [PMID: 35696540 PMCID: PMC9544176 DOI: 10.1002/mrm.29350] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2022] [Revised: 05/18/2022] [Accepted: 05/18/2022] [Indexed: 11/15/2022]
Abstract
Purpose To characterize the acceleration capabilities of a silent head insert gradient axis that operates at the inaudible frequency of 20 kHz and a maximum gradient amplitude of 40 mT/m without inducing peripheral nerve stimulation. Methods The silent gradient axis' acquisitions feature an oscillating gradient in the phase‐encoding direction that is played out on top of a cartesian readout, similarly as done in Wave‐CAIPI. The additional spatial encoding fills k‐space in readout lanes allowing for the acquisition of fewer phase‐encoding steps without increasing aliasing artifacts. Fully sampled 2D gradient echo datasets were acquired both with and without the silent readout. All scans were retrospectively undersampled (acceleration factors R = 1 to 12) to compare conventional SENSE acceleration and acceleration using the silent gradient. The silent gradient amplitude and the readout bandwidth were varied to investigate the effect on artifacts and g‐factor. Results The silent readout reduced the g‐factor for all acceleration factors when compared to SENSE acceleration. Increasing the silent gradient amplitude from 31.5 mT/m to 40 mT/m at an acceleration factor of 10 yielded a reduction in the average g‐factor (gavg) from 1.3 ± 0.14 (gmax = 1.9) to 1.1 ± 0.09 (gmax = 1.6). Furthermore, reducing the number of cycles increased the readout bandwidth and the g‐factor that reached gavg = 1.5 ± 0.16 for a readout bandwidth of 651 Hz/pixel and an acceleration factor of R = 8. Conclusion A silent gradient axis enables high acceleration factors up to R = 10 while maintaining a g‐factor close to unity (gavg = 1.1 and gmax = 1.6) and can be acquired with clinically relevant readout bandwidths. Click here for author‐reader discussions
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Affiliation(s)
- Edwin Versteeg
- Department of RadiologyUniversity Medical Center Utrecht
UtrechtThe Netherlands
| | - Dennis W. J. Klomp
- Department of RadiologyUniversity Medical Center Utrecht
UtrechtThe Netherlands
| | - Jeroen C. W. Siero
- Department of RadiologyUniversity Medical Center Utrecht
UtrechtThe Netherlands
- Spinoza Center for NeuroimagingAmsterdamNetherlands
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6
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Versteeg E, Klomp DWJ, Siero JCW. A silent gradient axis for soundless spatial encoding to enable fast and quiet brain imaging. Magn Reson Med 2021; 87:1062-1073. [PMID: 34545956 PMCID: PMC9293127 DOI: 10.1002/mrm.29010] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/05/2021] [Revised: 08/17/2021] [Accepted: 08/30/2021] [Indexed: 12/22/2022]
Abstract
Purpose A novel silent imaging method is proposed that combines a gradient insert oscillating at the inaudible frequency 20 kHz with slew rate‐limited gradient waveforms to form a silent gradient axis that enable quiet and fast imaging. Methods The gradient insert consisted of a plug‐and‐play (45 kg) single axis z‐gradient, which operated as an additional fourth gradient axis. This insert was made resonant using capacitors and combined with an audio amplifier to allow for operation at 20 kHz. The gradient field was characterized using field measurements and the physiological effects of operating a gradient field at 20 kHz were explored using peripheral nerve stimulation experiments, tissue heating simulations and sound measurements. The imaging sequence consisted of a modified gradient‐echo sequence which fills k‐space in readout lanes with a width proportional to the oscillating gradient amplitude. The feasibility of the method was demonstrated in‐vivo using 2D and 3D gradient echo (GRE) sequences which were reconstructed using a conjugate‐gradient SENSE reconstruction. Results Field measurements yielded a maximum gradient amplitude and slew rate of 40.8 mT/m and 5178T/m/s at 20 kHz. Physiological effects such as peripheral nerve stimulation and tissue heating were found not to be limiting at this amplitude and slew rate. For a 3D GRE sequence, a maximum sound level of 85 db(A) was measured during scanning. Imaging experiments using the silent gradient axis produced artifact free images while also featuring a 5.3‐fold shorter scan time than a fully sampled acquisition. Conclusion A silent gradient axis provides a novel pathway to fast and quiet brain imaging.
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Affiliation(s)
- Edwin Versteeg
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Dennis W J Klomp
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Jeroen C W Siero
- Department of Radiology, University Medical Center Utrecht, Utrecht, The Netherlands.,Spinoza Center for Neuroimaging, Amsterdam, Netherlands
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7
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Versteeg E, van der Velden TA, van Leeuwen CC, Borgo M, Huijing ER, Hendriks AD, Hendrikse J, Klomp DWJ, Siero JCW. A plug-and-play, lightweight, single-axis gradient insert design for increasing spatiotemporal resolution in echo planar imaging-based brain imaging. NMR Biomed 2021; 34:e4499. [PMID: 33619838 PMCID: PMC8244051 DOI: 10.1002/nbm.4499] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/06/2019] [Revised: 02/09/2021] [Accepted: 02/11/2021] [Indexed: 05/25/2023]
Abstract
The goal of this study was to introduce and evaluate the performance of a lightweight, high-performance, single-axis (z-axis) gradient insert design primarily intended for high-resolution functional magnetic resonance imaging, and aimed at providing both ease of use and a boost in spatiotemporal resolution. The optimal winding positions of the coil were obtained using a genetic algorithm with a cost function that balanced gradient performance (minimum 0.30 mT/m/A) and field linearity (≥16 cm linear region). These parameters were verified using field distribution measurements by B0 -mapping. The correction of geometrical distortions was performed using theoretical field distribution of the coil. Simulations and measurements were performed to investigate the echo planar imaging echo-spacing reduction due to the improved gradient performance. The resulting coil featured a 16-cm linear region, a weight of 45 kg, an installation time of 15 min, and a maximum gradient strength and slew rate of 200 mT/m and 1300 T/m/s, respectively, when paired with a commercially available gradient amplifier (940 V/630 A). The field distribution measurements matched the theoretically expected field. By utilizing the theoretical field distribution, geometrical distortions were corrected to within 6% of the whole-body gradient reference image in the target region. Compared with a whole-body gradient set, a maximum reduction in echo-spacing of a factor of 2.3 was found, translating to a 344 μs echo-spacing, for a field of view of 192 mm, a receiver bandwidth of 920 kHz and a gradient amplitude of 112 mT/m. We present a lightweight, single-axis gradient insert design that can provide high gradient performance and an increase in spatiotemporal resolution with correctable geometrical distortions while also offering a short installation time of less than 15 min and minimal system modifications.
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Affiliation(s)
- Edwin Versteeg
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | | | | | | | - Erik R. Huijing
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Arjan D. Hendriks
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Jeroen Hendrikse
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Dennis W. J. Klomp
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
| | - Jeroen C. W. Siero
- Department of RadiologyUniversity Medical Center UtrechtUtrechtthe Netherlands
- Spinoza Center for NeuroimagingAmsterdamthe Netherlands
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8
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Branderhorst W, Steensma BR, Beijst C, Huijing ER, Alborahal C, Versteeg E, Weissler B, Schug D, Gebhardt P, Gross-Weege N, Mueller F, Krueger K, Dey T, Radermacher H, Lips O, Lagendijk J, Schulz V, de Jong HWAM, Klomp DWJ. Evaluation of the radiofrequency performance of a wide-bore 1.5 T positron emission tomography/magnetic resonance imaging body coil for radiotherapy planning. Phys Imaging Radiat Oncol 2020; 17:13-19. [PMID: 33898772 PMCID: PMC8057958 DOI: 10.1016/j.phro.2020.12.002] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 11/17/2020] [Accepted: 12/09/2020] [Indexed: 11/13/2022]
Abstract
Background and purpose The restricted bore diameter of current simultaneous positron emission tomography/magnetic resonance imaging (PET/MRI) systems can be an impediment to achieving similar patient positioning during PET/MRI planning and radiotherapy. Our goal was to evaluate the B1 transmit (B1+) uniformity, B1+ efficiency, and specific absorption rate (SAR) of a novel radiofrequency (RF) body coil design, in which RF shielded PET detectors were integrated with the specific aim of enabling a wide-bore PET/MRI system. Materials and methods We designed and constructed a wide-bore PET/MRI RF body coil to be integrated with a clinical MRI system. To increase its inner bore diameter, the PET detectors were positioned between the conductors and the RF shield of the RF body coil. Simulations and experiments with phantoms and human volunteers were performed to compare the B1+ uniformity, B1+ efficiency, and SAR between our design and the clinical body coil. Results In the simulations, our design achieved nearly the same B1+ field uniformity as the clinical body coil and an almost identical SAR distribution. The uniformity findings were confirmed by the physical experiments. The B1+ efficiency was 38% lower compared to the clinical body coil. Conclusions To achieve wide-bore PET/MRI, it is possible to integrate shielding for PET detectors between the body coil conductors and the RF shield without compromising MRI performance. Reduced B1+ efficiency may be compensated by adding a second RF amplifier. This finding may facilitate the application of simultaneous whole-body PET/MRI in radiotherapy planning.
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Affiliation(s)
- Woutjan Branderhorst
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bart R Steensma
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Casper Beijst
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Erik R Huijing
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Cezar Alborahal
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Edwin Versteeg
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Bjoern Weissler
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - David Schug
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Pierre Gebhardt
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Nicolas Gross-Weege
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Florian Mueller
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Karl Krueger
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Thomas Dey
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Harald Radermacher
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | | | - Jan Lagendijk
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Volkmar Schulz
- Department of Physics of Molecular Imaging Systems, RWTH Aachen University, Aachen, Germany
| | - Hugo W A M de Jong
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
| | - Dennis W J Klomp
- Department of Radiology and Nuclear Medicine, University Medical Center Utrecht, Utrecht, The Netherlands
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9
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Annink KV, van der Aa NE, Dudink J, Alderliesten T, Groenendaal F, Lequin M, Jansen FE, Rhebergen KS, Luijten P, Hendrikse J, Hoogduin HJM, Huijing ER, Versteeg E, Visser F, Raaijmakers AJE, Wiegers EC, Klomp DWJ, Wijnen JP, Benders MJNL. Introduction of Ultra-High-Field MR Imaging in Infants: Preparations and Feasibility. AJNR Am J Neuroradiol 2020; 41:1532-1537. [PMID: 32732273 DOI: 10.3174/ajnr.a6702] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2019] [Accepted: 05/19/2020] [Indexed: 12/13/2022]
Abstract
BACKGROUND AND PURPOSE Cerebral MR imaging in infants is usually performed with a field strength of up to 3T. In adults, a growing number of studies have shown added diagnostic value of 7T MR imaging. 7T MR imaging might be of additional value in infants with unexplained seizures, for example. The aim of this study was to investigate the feasibility of 7T MR imaging in infants. We provide information about the safety preparations and show the first MR images of infants at 7T. MATERIALS AND METHODS Specific absorption rate levels during 7T were simulated in Sim4life using infant and adult models. A newly developed acoustic hood was used to guarantee hearing protection. Acoustic noise damping of this hood was measured and compared with the 3T Nordell hood and no hood. In this prospective pilot study, clinically stable infants, between term-equivalent age and the corrected age of 3 months, underwent 7T MR imaging immediately after their standard 3T MR imaging. The 7T scan protocols were developed and optimized while scanning this cohort. RESULTS Global and peak specific absorption rate levels in the infant model in the centered position and 50-mm feet direction did not exceed the levels in the adult model. Hearing protection was guaranteed with the new hood. Twelve infants were scanned. No MR imaging-related adverse events occurred. It was feasible to obtain good-quality imaging at 7T for MRA, MRV, SWI, single-shot T2WI, and MR spectroscopy. T1WI had lower quality at 7T. CONCLUSIONS 7T MR imaging is feasible in infants, and good-quality scans could be obtained.
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Affiliation(s)
- K V Annink
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
| | - N E van der Aa
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
| | - J Dudink
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
| | - T Alderliesten
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
| | - F Groenendaal
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
| | - M Lequin
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - F E Jansen
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
| | - K S Rhebergen
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - P Luijten
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - J Hendrikse
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - H J M Hoogduin
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - E R Huijing
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - E Versteeg
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - F Visser
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - A J E Raaijmakers
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - E C Wiegers
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - D W J Klomp
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - J P Wijnen
- the Departments of Radiology (M.L., P.L., J.H., H.J.M.H., E.R.H., E.V., F.V., A.J.E.R., E.C.W., D.W.J.K., J.P.W.), and Otorhinolaryngology and Head and Neck Surgery (K.S.R.), University Medical Center Utrecht, University Utrecht, Utrecht, the Netherlands
| | - M J N L Benders
- From the Departments of Neonatology (K.V.A., N.E.v.d.A., J.D., T.A., F.G., M.J.N.L.B.), and Paediatric Neurology (F.E.J.), University Medical Center Utrecht Brain Center
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Abstract
We studied the effect of convergent clustering of ampullary electroreceptor organs on stimulus transduction and transmission in the catfish Icalurus melas by electrophysiologically recording primary afferent activity of single ampullae (singlets) and pairs (doublets) innervated by the same afferent. Doublets were twice as sensitive as singlets, and showed sharper tuning around the best frequency. The slope of the phase curve in the doublets was slightly steeper than in the singlets. The spontaneous activity and scatter in interspike interval were not correlated with clustering. The implications of these findings for signal averaging in sensory neurons and their relevance for behaviour are discussed.
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Peters RC, Versteeg E, Bretschneider F, Brans RJ, Went A. Caffeine reduces the efficacy of electroreceptor cell synapses: an electrophysiological single-unit in vivo study. Neuroscience 1997; 78:1229-38. [PMID: 9174089 DOI: 10.1016/s0306-4522(96)00701-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Ampullary electroreceptor organs of catfish, Ictalurus melas, were exposed apically to caffeine solutions at concentrations of 0, 5, 7.5, 10, and 15 mM. Recording sinusoidally-modulated activity of single-unit afferents reveals a dose-dependent decrease in mean afferent activity and sensitivity. A rebound effect of average activity occurs after caffeine is washed out. After 25 min exposure to 15 mM caffeine the peak of the gain curve shifts from 8 Hz to 4 Hz. The corresponding phase characteristic shows an increased phase lag with a maximum shift of 35 degrees at 20 Hz. The latency between stimulus and response increases from 12 to 19 ms; the recovery time after onset of the pulse decreases with 60 ms. The most probable explanation for the recorded effects is that caffeine reduces the availability of intracellular Ca2+ by blocking of the inositol triphosphate receptors in the endoplasmic reticulum. This in turn would affect many intracellular properties and processes. The unavailability of Ca2+ could reduce the synaptic efficacy and increase latency by suppressing fusion of synaptic vesicles with the presynaptic membrane and by depressing vesicle transport. The change in frequency response corresponds in part to reduction of the apical membrane surface area of the receptor cells, and in part to the increased latency. Accumulation of glutamate-containing vesicles could account for the higher mean activity and modulation amplitude in the lower frequency range after caffeine is washed out. Caffeine might act postsynaptically by inducing hyperpolarization of the terminals of the primary afferents.
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Affiliation(s)
- R C Peters
- Utrecht University, Comparative Physiology, The Netherlands
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