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Le Y, Chen J, Rossman P, Bolster B, Kannengiesser S, Manduca A, Glaser K, Sui Y, Huston J, Yin Z, Ehman RL. Wavelet MRE: Imaging propagating broadband acoustic waves with wavelet-based motion-encoding gradients. Magn Reson Med 2024; 91:1923-1935. [PMID: 38098427 PMCID: PMC10950519 DOI: 10.1002/mrm.29972] [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: 07/10/2023] [Revised: 10/24/2023] [Accepted: 11/26/2023] [Indexed: 03/20/2024]
Abstract
PURPOSE To demonstrate a novel MR elastography (MRE) technique, termed here wavelet MRE. With this technique, broadband motion sensitivity is achievable. Moreover, the true tissue displacement can be reconstructed with a simple inverse transform. METHODS A wavelet MRE sequence was developed with motion-encoding gradients based on Haar wavelets. From the phase images' displacement was estimated using an inverse transform. Simulations were performed using a frequency sweep and a transient as ground-truth motions. A PVC phantom was scanned using wavelet MRE and standard MRE with both transient (one and 10 cycles of 90-Hz motion) and steady-state dual-frequency motion (30 and 60 Hz) for comparison. The technique was tested in a human brain, and motion trajectories were estimated for each voxel. RESULTS In simulation, the displacement information estimated from wavelet MRE closely matched the true motion. In the phantom test, the MRE phase data generated from the displacement information derived from wavelet MRE agreed well with standard MRE data. Testing of wavelet MRE to assess transient motion waveforms in the brain was successful, and the tissue motion observed was consistent with a previous study. CONCLUSION The uniform and broadband frequency response of wavelet MRE makes it a promising method for imaging transient, multifrequency motion, or motion with unknown frequency content. One potential application is measuring the response of brain tissue undergoing low-amplitude, transient vibrations as a model for the study of traumatic brain injury.
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Affiliation(s)
- Yuan Le
- Department of Radiology, Mayo Clinic, Rochester, MN
| | - Jun Chen
- Department of Radiology, Mayo Clinic, Rochester, MN
| | | | - Bradley Bolster
- MR Collaborations, Siemens Medical Solutions USA, Inc., Malvern, PA, USA
| | | | | | - Kevin Glaser
- Department of Radiology, Mayo Clinic, Rochester, MN
| | - Yi Sui
- Department of Radiology, Mayo Clinic, Rochester, MN
| | - John Huston
- Department of Radiology, Mayo Clinic, Rochester, MN
| | - Ziying Yin
- Department of Radiology, Mayo Clinic, Rochester, MN
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Choquet K, Vappou J, Cabras P, Ishak O, Gangi A, Breton E. Magnetic Resonance Acoustic Radiation Force Imaging (MR-ARFI) for the monitoring of High Intensity Focused Ultrasound (HIFU) ablation in anisotropic tissue. MAGMA (NEW YORK, N.Y.) 2023; 36:737-747. [PMID: 36723689 DOI: 10.1007/s10334-023-01062-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2022] [Revised: 01/06/2023] [Accepted: 01/10/2023] [Indexed: 02/02/2023]
Abstract
OBJECTIVE We introduce a non-invasive MR-Acoustic Radiation Force Imaging (ARFI)-based elastography method that provides both the local shear modulus and temperature maps for the monitoring of High Intensity Focused Ultrasound (HIFU) therapy. MATERIALS AND METHODS To take tissue anisotropy into account, the local shear modulus μ is determined in selected radial directions around the focal spot by fitting the phase profiles to a linear viscoelastic model, including tissue-specific mechanical relaxation time τ. MR-ARFI was evaluated on a calibrated phantom, then applied to the monitoring of HIFU in a gel phantom, ex vivo and in vivo porcine muscle tissue, in parallel with MR-thermometry. RESULTS As expected, the shear modulus polar maps reflected the isotropy of phantoms and the anisotropy of muscle. In the HIFU monitoring experiments, both the shear modulus polar map and the thermometry map were updated with every pair of MR-ARFI phase images acquired with opposite MR-ARFI-encoding. The shear modulus was found to decrease (phantom and ex vivo) or increase (in vivo) during heating, before remaining steady during the cooling phase. The mechanical relaxation time, estimated pre- and post-HIFU, was found to vary in muscle tissue. DISCUSSION MR-ARFI allowed for monitoring of viscoelasticity changes around the HIFU focal spot even in anisotropic muscle tissue.
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Affiliation(s)
- Karine Choquet
- Université de Strasbourg, CNRS, ICube, UMR 7357, Strasbourg, France.
| | - Jonathan Vappou
- Université de Strasbourg, CNRS, ICube, UMR 7357, Strasbourg, France
| | - Paolo Cabras
- Université de Strasbourg, CNRS, ICube, UMR 7357, Strasbourg, France
- Image Guided Therapy, Pessac, France
| | - Ounay Ishak
- Université de Strasbourg, CNRS, ICube, UMR 7357, Strasbourg, France
| | - Afshin Gangi
- Université de Strasbourg, CNRS, ICube, UMR 7357, Strasbourg, France
- Department of Interventional Imaging, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Elodie Breton
- Université de Strasbourg, CNRS, ICube, UMR 7357, Strasbourg, France.
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Odéen H, Hofstetter LW, Payne AH, Guiraud L, Dumont E, Parker DL. Simultaneous proton resonance frequency T 1 - MR shear wave elastography for MR-guided focused ultrasound multiparametric treatment monitoring. Magn Reson Med 2023; 89:2171-2185. [PMID: 36656135 PMCID: PMC10940047 DOI: 10.1002/mrm.29587] [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: 08/30/2022] [Revised: 12/21/2022] [Accepted: 12/30/2022] [Indexed: 01/20/2023]
Abstract
PURPOSE To develop an efficient MRI pulse sequence to simultaneously measure multiple parameters that have been shown to correlate with tissue nonviability following thermal therapies. METHODS A 3D segmented EPI pulse sequence was used to simultaneously measure proton resonance frequency shift (PRFS) MR thermometry (MRT), T1 relaxation time, and shear wave velocity induced by focused ultrasound (FUS) push pulses. Experiments were performed in tissue mimicking gelatin phantoms and ex vivo bovine liver. Using a carefully designed FUS triggering scheme, a heating duty cycle of approximately 65% was achieved by interleaving FUS ablation pulses with FUS push pulses to induce shear waves in the tissue. RESULTS In phantom studies, temperature increases measured with PRFS MRT and increases in T1 correlated with decreased shear wave velocity, consistent with material softening with increasing temperature. During ablation in ex vivo liver, temperature increase measured with PRFS MRT initially correlated with increasing T1 and decreasing shear wave velocity, and after tissue coagulation with decreasing T1 and increasing shear wave velocity. This is consistent with a previously described hysteresis in T1 versus PRFS curves and increased tissue stiffness with tissue coagulation. CONCLUSION An efficient approach for simultaneous and dynamic measurements of PRSF, T1 , and shear wave velocity during treatment is presented. This approach holds promise for providing co-registered dynamic measures of multiple parameters, which correlates to tissue nonviability during and following thermal therapies, such as FUS.
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Affiliation(s)
- Henrik Odéen
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Lorne W. Hofstetter
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | - Allison H. Payne
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
| | | | | | - Dennis L. Parker
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, USA
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Ishak O, Breton E, Choquet K, Josset A, Cabras P, Vappou J. Monitoring MR-guided high intensity focused ultrasound therapy using transient supersonic shear wave MR-elastography. Phys Med Biol 2023; 68. [PMID: 36595333 DOI: 10.1088/1361-6560/acac5e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2022] [Accepted: 12/16/2022] [Indexed: 12/23/2022]
Abstract
Objective.The aim of the paper is to propose an all-in-one method based on magnetic resonance-supersonic shear wave imaging (MR-SSI) and proton resonance frequency shift (PRFS) to monitor high intensity focused ultrasound (HIFU) thermal ablations.Approach.Mechanical properties have been shown to be related to tissue damage induced by thermal ablations. Monitoring elasticity in addition to temperature changes may help in ensuring the efficacy and the accuracy of HIFU therapies. For this purpose, an MR-SSI method has been developed where the ultrasonic transducer is used for both mechanical wave generation and thermal ablation. Transient quasi-planar shear waves are generated using the acoustic radiation force, and their propagation is monitored in motion-sensitized phase MR images. Using a single-shot gradient-echo echo-planar-imaging sequence, MR images can be acquired at a sufficiently high temporal resolution to provide an update of PRFS thermometry and MR-SSI elastography maps in real time.Main results.The proposed method was first validated on a calibrated elasticity phantom, in which both the possibility to detect inclusions with different stiffness and repeatability were demonstrated. The standard deviation between the 8 performed measurements was 2% on the background of the phantom and 11%, at most, on the inclusions. A second experiment consisted in performing a HIFU heating in a gelatin phantom. The temperature increase was estimated to be 9 °C and the shear modulus was found to decrease from 2.9 to 1.8 kPa, reflecting the gel softening around the HIFU focus, whereas it remained steady in non-heated areas.Significance.The proposed MR-SSI technique allows monitoring HIFU ablations using thermometry and elastography simultaneously, without the need for an additional external mechanical exciter such as those used in MR elastography.
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Affiliation(s)
- Ounay Ishak
- Université de Strasbourg, CNRS, ICube, UMR7357, Strasbourg, France
| | - Elodie Breton
- Université de Strasbourg, CNRS, ICube, UMR7357, Strasbourg, France
| | - Karine Choquet
- Université de Strasbourg, CNRS, ICube, UMR7357, Strasbourg, France
| | - Anne Josset
- Université de Strasbourg, CNRS, ICube, UMR7357, Strasbourg, France
| | - Paolo Cabras
- Université de Strasbourg, CNRS, ICube, UMR7357, Strasbourg, France.,Image Guided Therapy, Pessac, France
| | - Jonathan Vappou
- Université de Strasbourg, CNRS, ICube, UMR7357, Strasbourg, France
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Mohammadjavadi M, Ash RT, Li N, Gaur P, Kubanek J, Saenz Y, Glover GH, Popelka GR, Norcia AM, Pauly KB. Transcranial ultrasound neuromodulation of the thalamic visual pathway in a large animal model and the dose-response relationship with MR-ARFI. Sci Rep 2022; 12:19588. [PMID: 36379960 PMCID: PMC9666449 DOI: 10.1038/s41598-022-20554-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/12/2022] [Accepted: 09/14/2022] [Indexed: 11/16/2022] Open
Abstract
Neuromodulation of deep brain structures via transcranial ultrasound stimulation (TUS) is a promising, but still elusive approach to non-invasive treatment of brain disorders. The purpose of this study was to confirm that MR-guided TUS of the lateral geniculate nucleus (LGN) can modulate visual evoked potentials (VEPs) in the intact large animal; and to study the impact on cortical brain oscillations. The LGN on one side was identified with T2-weighted MRI in sheep (all male, n = 9). MR acoustic radiation force imaging (MR-ARFI) was used to confirm localization of the targeted area in the brain. Electroencephalographic (EEG) signals were recorded, and the visual evoked potential (VEP) peak-to-peak amplitude (N70 and P100) was calculated for each trial. Time-frequency spectral analysis was performed to elucidate the effect of TUS on cortical brain dynamics. The VEP peak-to-peak amplitude was reversibly suppressed relative to baseline during TUS. Dynamic spectral analysis demonstrated a change in cortical oscillations when TUS is paired with visual sensory input. Sonication-associated microscopic displacements, as measured by MR-ARFI, correlated with the TUS-mediated suppression of visual evoked activity. TUS non-invasively delivered to LGN can neuromodulate visual activity and oscillatory dynamics in large mammalian brains.
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Affiliation(s)
| | - Ryan T Ash
- Department of Psychiatry and Behavioral Sciences, Stanford University, Stanford, CA, USA
| | - Ningrui Li
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Pooja Gaur
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Jan Kubanek
- Department of Biomedical Engineering, The University of Utah, Salt Lake City, Utah, USA
| | - Yamil Saenz
- Department of Radiology, Stanford University, Stanford, CA, USA
| | - Gary H Glover
- Department of Radiology, Stanford University, Stanford, CA, USA
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA
| | - Gerald R Popelka
- Department of Radiology, Stanford University, Stanford, CA, USA
- Department of Otolaryngology, Stanford University, Stanford, CA, USA
| | | | - Kim Butts Pauly
- Department of Radiology, Stanford University, Stanford, CA, USA.
- Department of Bioengineering, Stanford University, Stanford, CA, USA.
- Department of Electrical Engineering, Stanford University, Stanford, CA, USA.
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Li N, Gaur P, Quah K, Pauly KB. Improving in situ acoustic intensity estimates using MR acoustic radiation force imaging in combination with multifrequency MR elastography. Magn Reson Med 2022; 88:1673-1689. [PMID: 35762849 PMCID: PMC9439407 DOI: 10.1002/mrm.29309] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/12/2022] [Revised: 04/28/2022] [Accepted: 04/30/2022] [Indexed: 11/08/2022]
Abstract
PURPOSE Magnetic resonance acoustic radiation force imaging (MR-ARFI) enables focal spot localization during nonablative transcranial ultrasound therapies. As the acoustic radiation force is proportional to the applied acoustic intensity, measured MR-ARFI displacements could potentially be used to estimate the acoustic intensity at the target. However, variable brain stiffness is an obstacle. The goal of this study was to develop and assess a method to accurately estimate the acoustic intensity at the focus using MR-ARFI displacements in combination with viscoelastic properties obtained with multifrequency MR elastography (MRE). METHODS Phantoms with a range of viscoelastic properties were fabricated, and MR-ARFI displacements were acquired within each phantom using multiple acoustic intensities. Voigt model parameters were estimated for each phantom based on storage and loss moduli measured using multifrequency MRE, and these were used to predict the relationship between acoustic intensity and measured displacement. RESULTS Using assumed viscoelastic properties, MR-ARFI displacements alone could not accurately estimate acoustic intensity across phantoms. For example, acoustic intensities were underestimated in phantoms stiffer than the assumed stiffness and overestimated in phantoms softer than the assumed stiffness. This error was greatly reduced using individualized viscoelasticity measurements obtained from MRE. CONCLUSION We demonstrated that viscoelasticity information from MRE could be used in combination with MR-ARFI displacements to obtain more accurate estimates of acoustic intensity. Additionally, Voigt model viscosity parameters were found to be predictive of the relaxation rate of each phantom's time-varying displacement response, which could be used to optimize patient-specific MR-ARFI pulse sequences.
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Affiliation(s)
- Ningrui Li
- Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Pooja Gaur
- Department of Radiology, Stanford University, Stanford, California, USA
| | - Kristin Quah
- Department of Electrical Engineering, Stanford University, Stanford, California, USA
| | - Kim Butts Pauly
- Department of Radiology, Stanford University, Stanford, California, USA
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Geoghegan R, Ter Haar G, Nightingale K, Marks L, Natarajan S. Methods of monitoring thermal ablation of soft tissue tumors - A comprehensive review. Med Phys 2022; 49:769-791. [PMID: 34965307 DOI: 10.1002/mp.15439] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2020] [Revised: 11/30/2020] [Accepted: 12/15/2021] [Indexed: 11/12/2022] Open
Abstract
Thermal ablation is a form of hyperthermia in which oncologic control can be achieved by briefly inducing elevated temperatures, typically in the range 50-80°C, within a target tissue. Ablation modalities include high intensity focused ultrasound, radiofrequency ablation, microwave ablation, and laser interstitial thermal therapy which are all capable of generating confined zones of tissue destruction, resulting in fewer complications than conventional cancer therapies. Oncologic control is contingent upon achieving predefined coagulation zones; therefore, intraoperative assessment of treatment progress is highly desirable. Consequently, there is a growing interest in the development of ablation monitoring modalities. The first section of this review presents the mechanism of action and common applications of the primary ablation modalities. The following section outlines the state-of-the-art in thermal dosimetry which includes interstitial thermal probes and radiologic imaging. Both the physical mechanism of measurement and clinical or pre-clinical performance are discussed for each ablation modality. Thermal dosimetry must be coupled with a thermal damage model as outlined in Section 4. These models estimate cell death based on temperature-time history and are inherently tissue specific. In the absence of a reliable thermal model, the utility of thermal monitoring is greatly reduced. The final section of this review paper covers technologies that have been developed to directly assess tissue conditions. These approaches include visualization of non-perfused tissue with contrast-enhanced imaging, assessment of tissue mechanical properties using ultrasound and magnetic resonance elastography, and finally interrogation of tissue optical properties with interstitial probes. In summary, monitoring thermal ablation is critical for consistent clinical success and many promising technologies are under development but an optimal solution has yet to achieve widespread adoption.
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Affiliation(s)
- Rory Geoghegan
- Department of Urology, University of California Los Angeles, Los Angeles, California, USA
| | - Gail Ter Haar
- Department of Physics, Institute of Cancer Research, University of London, Sutton, UK
| | - Kathryn Nightingale
- Department of Biomedical Engineering, Duke University, Durham, North Carolina, USA
| | - Leonard Marks
- Department of Urology, University of California Los Angeles, Los Angeles, California, USA
| | - Shyam Natarajan
- Departments of Urology & Bioengineering, University of California Los Angeles, Los Angeles, California, USA
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Hofstetter LW, Odéen H, Bolster BD, Christensen DA, Payne A, Parker DL. Magnetic resonance shear wave elastography using transient acoustic radiation force excitations and sinusoidal displacement encoding. Phys Med Biol 2021; 66. [PMID: 33352538 DOI: 10.1088/1361-6560/abd5ce] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2020] [Accepted: 12/22/2020] [Indexed: 12/31/2022]
Abstract
A magnetic resonance (MR) shear wave elastography technique that uses transient acoustic radiation force impulses from a focused ultrasound (FUS) transducer and a sinusoidal-shaped MR displacement encoding strategy is presented. Using this encoding strategy, an analytic expression for calculating the shear wave speed in a heterogeneous medium was derived. Green's function-based simulations were used to evaluate the feasibility of calculating shear wave speed maps using the analytic expression. Accuracy of simulation technique was confirmed experimentally in a homogeneous gelatin phantom. The elastography measurement was compared to harmonic MR elastography in a homogeneous phantom experiment and the measured shear wave speed values differed by less than 14%. This new transient elastography approach was able to map the position and shape of inclusions sized from 8.5 to 14 mm in an inclusion phantom experiment. These preliminary results demonstrate the feasibility of using a straightforward analytic expression to generate shear wave speed maps from MR images where sinusoidal-shaped motion encoding gradients are used to encode the displacement-time history of a transiently propagating wave-packet. This new measurement technique may be particularly well suited for performing elastography before, during, and after MR-guided FUS therapies since the same device used for therapy is also used as an excitation source for elastography.
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Affiliation(s)
- Lorne W Hofstetter
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Henrik Odéen
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Bradley D Bolster
- Siemens Medical Solutions USA, Inc., Salt Lake City, Utah, United States of America
| | - Douglas A Christensen
- Department of Bioengineering, University of Utah, Salt Lake City, Utah, United States of America.,Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah, United States of America
| | - Allison Payne
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, United States of America
| | - Dennis L Parker
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah, United States of America
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Hofstetter LW, Fausett L, Mueller A, Odéen H, Payne A, Christensen DA, Parker DL. Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging. Int J Hyperthermia 2020; 37:283-290. [PMID: 32204632 DOI: 10.1080/02656736.2020.1739345] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
Abstract
Purpose: To develop and characterize a tissue-mimicking phantom that enables the direct comparison of magnetic resonance (MR) and ultrasound (US) imaging techniques useful for monitoring high-intensity focused ultrasound (HIFU) treatments. With no additions, gelatin phantoms produce little if any scattering required for US imaging. This study characterizes the MR and US image characteristics as a function of psyllium husk concentration, which was added to increase US scattering.Methods: Gelatin phantoms were constructed with varying concentrations of psyllium husk. The effects of psyllium husk concentration on US B-mode and MR imaging were evaluated at nine different concentrations. T1, T2, and T2* MR maps were acquired. Acoustic properties (attenuation and speed of sound) were measured at frequencies of 0.6, 1.0, 1.8, and 3.0 MHz using a through-transmission technique. Phantom elastic properties were evaluated for both time and temperature dependence.Results: Ultrasound image echogenicity increased with increasing psyllium husk concentration while quality of gradient-recalled echo MR images decreased with increasing concentration. For all phantoms, the measured speed of sound ranged between 1567-1569 m/s and the attenuation ranged between 0.42-0.44 dB/(cm·MHz). Measured T1 ranged from 974-1051 ms. The T2 and T2* values ranged from 97-108 ms and 48-88 ms, respectively, with both showing a decreasing trend with increased psyllium husk concentration. Phantom stiffness, measured using US shear-wave speed measurements, increased with age and decreased with increasing temperature.Conclusions: The presented dual-use tissue-mimicking phantom is easy to manufacture and can be used to compare and evaluate US-guided and MR-guided HIFU imaging protocols.
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Affiliation(s)
- Lorne W Hofstetter
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
| | - Lewis Fausett
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
| | - Alexander Mueller
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
| | - Henrik Odéen
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
| | - Allison Payne
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
| | - Douglas A Christensen
- Department of Bioengineering, University of Utah, Salt Lake City, UT, USA.,Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, UT, USA
| | - Dennis L Parker
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, UT, USA
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Kim K, Breton E, Gangi A, Vappou J. Simultaneous fat-referenced proton resonance frequency shift thermometry and MR elastography for the monitoring of thermal ablations. Magn Reson Med 2019; 84:339-347. [PMID: 31823418 DOI: 10.1002/mrm.28130] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2019] [Revised: 11/21/2019] [Accepted: 11/24/2019] [Indexed: 12/18/2022]
Abstract
PURPOSE Simultaneous fat-referenced proton resonance frequency shift (FRPRFS) thermometry combined with MR elastography (MRE) is proposed, to continuously monitor thermal ablations for all types of soft tissues, including fat-containing tissues. Fat-referenced proton resonance frequency shift thermometry makes it possible to measure temperature even in the water fraction of fat-containing tissues while enabling local field-drift correction. Magnetic resonance elastography allows measuring the mechanical properties of tissues that are related to tissue structural damage. METHODS A gradient-echo MR sequence framework was proposed that combines the need for multiple TE acquisitions for the water-fat separation of FRPRFS, and the need for multiple MRE phase offsets for elastogram reconstructions. Feasibility was first assessed in a fat-containing gelatin phantom undergoing moderate heating by a hot water circulation system. Subsequently, high intensity focused ultrasound heating was conducted in porcine muscle tissue ex vivo (N = 4; 2 samples, 2 locations/sample). RESULTS Both FRPRFS temperature maps and elastograms were updated every 4.1 seconds. In the gelatin phantom, FRPRFS was in good agreement with optical fiber thermometry (average difference 1.2 ± 1°C). In ex vivo high-intensity focused ultrasound experiments on muscle tissue, the shear modulus was found to decrease significantly by 34.3% ± 7.7% (experiment 1, sample 1), 17.9% ± 10.0% (experiment 2, sample 1), 55.1% ± 8.7% (experiment 3, sample 2), and 34.7% ± 8.4% (experiment 4, sample 2) as a result of temperature increase (ΔT = 22.5°C ± 4.2°C, 14.0°C ± 2.8°C, 14.7°C ± 3.7°C, and 14.5°C ± 3.0°C, respectively). CONCLUSION This study demonstrated the feasibility of monitoring thermal ablations with FRPRFS thermometry together with MRE, even in fat-containing tissues. The acquisition time is similar to non-FRPRFS thermometry combined with MRE.
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Affiliation(s)
- Kisoo Kim
- ICube - UMR7357, Université de Strasbourg, CNRS, Strasbourg, France
| | - Elodie Breton
- ICube - UMR7357, Université de Strasbourg, CNRS, Strasbourg, France
| | - Afshin Gangi
- ICube - UMR7357, Université de Strasbourg, CNRS, Strasbourg, France.,Department of Interventional Imaging, Hôpitaux Universitaires de Strasbourg, Strasbourg, France
| | - Jonathan Vappou
- ICube - UMR7357, Université de Strasbourg, CNRS, Strasbourg, France
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