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Malmberg MA, Odéen H, Hofstetter LW, Hadley JR, Parker DL. Validation of single reference variable flip angle (SR-VFA) dynamic T 1 mapping with T 2 * correction using a novel rotating phantom. Magn Reson Med 2024; 91:1419-1433. [PMID: 38115639 PMCID: PMC10872756 DOI: 10.1002/mrm.29944] [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: 06/27/2023] [Revised: 10/12/2023] [Accepted: 11/09/2023] [Indexed: 12/21/2023]
Abstract
PURPOSE To validate single reference variable flip angle (SR-VFA) dynamic T1 mapping with and without T2 * correction against inversion recovery (IR) T1 measurements. METHODS A custom cylindrical phantom with three concentric compartments was filled with variably doped agar to produce a smooth spatial gradient of the T1 relaxation rate as a function of angle across each compartment. IR T1 , VFA T1 , and B1 + measurements were made on the phantom before rotation, and multi-echo stack-of-radial dynamic images were acquired during rotation via an MRI-compatible motor. B1 + -corrected SR-VFA and SR-VFA-T2 * T1 maps were computed from the sliding window reconstructed images and compared against rotationally registered IR and VFA T1 maps to determine the percentage error. RESULTS Both VFA and SR-VFA-T2 * T1 maps fell within 10% of IR T1 measurements for a low rotational speed, with a mean accuracy of 2.3% ± 2.6% and 2.8% ± 2.6%, respectively. Increasing rotational speed was found to decrease the accuracy due to increasing temporal smoothing over ranges where the T1 change had a nonconstant slope. SR-VFA T1 mapping was found to have similar accuracy as the SR-VFA-T2 * and VFA methods at low TEs (˜<2 ms), whereas accuracy degraded strongly with later TEs. T2 * correction of the SR-VFA T1 maps was found to consistently improve accuracy and precision, especially at later TEs. CONCLUSION SR-VFA-T2 * dynamic T1 mapping was found to be accurate against reference IR T1 measurements within 10% in an agar phantom. Further validation is needed in mixed fat-water phantoms and in vivo.
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Affiliation(s)
- Michael A. Malmberg
- Department of Bioengineering, University of Utah, Salt Lake City, UT, USA
- 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
| | | | - J. Rock Hadley
- Department of Radiology and Imaging Sciences, 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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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] [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: 08/30/2022] [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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Payne A, Merrill R, Minalga E, Hadley JR, Odeen H, Hofstetter LW, Johnson S, Tunon de Lara C, Auriol S, Recco S, Dumont E, Parker DL, Palussiere J. A Breast-Specific MR Guided Focused Ultrasound Platform and Treatment Protocol: First-in-Human Technical Evaluation. IEEE Trans Biomed Eng 2021; 68:893-904. [PMID: 32784128 PMCID: PMC7878578 DOI: 10.1109/tbme.2020.3016206] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
OBJECTIVE This paper presents and evaluates a breast-specific magnetic resonance guided focused ultrasound (MRgFUS) system. A first-in-human evaluation demonstrates the novel hardware, a sophisticated tumor targeting algorithm and a volumetric magnetic resonance imaging (MRI) protocol. METHODS At the time of submission, N = 10 patients with non-palpable T0 stage breast cancer have been treated with the breast MRgFUS system. The described tumor targeting algorithm is evaluated both with a phantom test and in vivo during the breast MRgFUS treatments. Treatments were planned and monitored using volumetric MR-acoustic radiation force imaging (MR-ARFI) and temperature imaging (MRTI). RESULTS Successful technical treatments were achieved in 80 % of the patients. All patients underwent the treatment with no sedation and 60 % of participants had analgesic support. The total MR treatment time ranged from 73 to 114 minutes. Mean error between desired and achieved targeting in a phantom was 2.9 ±1.8 mm while 6.2 ±1.9 mm was achieved in patient studies, assessed either with MRTI or MR-ARFI measurements. MRTI and MR-ARFI were successful in 60 % and 70 % of patients, respectively. CONCLUSION The targeting accuracy allows the accurate placement of the focal spot using electronic steering capabilities of the transducer. The use of both volumetric MRTI and MR-ARFI provides complementary treatment planning and monitoring information during the treatment, allowing the treatment of all breast anatomies, including homogeneously fatty breasts.
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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] [What about the content of this article? (0)] [Affiliation(s)] [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] [What about the content of this article? (0)] [Affiliation(s)] [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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Hofstetter LW, Parker DL. Corrections to "The Role of Viscosity in the Impulse Diffraction Field of Elastic Waves Induced by the Acoustic Radiation Force" and "Supersonic Shear Imaging: A New Technique for Soft Tissue Elasticity Mapping". IEEE Trans Ultrason Ferroelectr Freq Control 2020; 67:1492-1494. [PMID: 32070952 PMCID: PMC7819482 DOI: 10.1109/tuffc.2020.2973565] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
This article presents corrections to J. Bercoff et al., "The role of viscosity in the impulse diffraction field of elastic waves induced by the acoustic radiation force," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 51, no. 11, pp. 1523-1536, Nov. 2004, and J. Bercoff et al., "Supersonic shear imaging: A new technique for soft tissue elasticity mapping," IEEE Trans. Ultrason., Ferroelectr., Freq. Control, vol. 51, no. 4, pp. 396-409, Apr. 2004.
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Hofstetter LW, Odéen H, Bolster BD, Mueller A, Christensen DA, Payne A, Parker DL. Efficient shear wave elastography using transient acoustic radiation force excitations and MR displacement encoding. Magn Reson Med 2019; 81:3153-3167. [PMID: 30663806 PMCID: PMC6414262 DOI: 10.1002/mrm.27647] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [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: 06/18/2018] [Revised: 11/21/2018] [Accepted: 12/05/2018] [Indexed: 12/29/2022]
Abstract
PURPOSE To present a novel MR shear wave elastography (MR-SWE) method that efficiently measures the speed of propagating wave packets generated using acoustic radiation force (ARF) impulses. METHODS ARF impulses from a focused ultrasound (FUS) transducer were applied sequentially to a preselected set of positions and motion encoded MRI was used to acquire volumetric images of the propagating shear wavefront emanating from each point. The wavefront position at multiple propagation times was encoded in the MR phase image using a train of motion encoding gradient lobes. Generating a transient propagating wavefront at multiple spatial positions and sampling each at multiple time-points allowed for shear wave speed maps to be efficiently created. MR-SWE was evaluated in tissue mimicking phantoms and ex vivo bovine liver tissue before and after ablation. RESULTS MR-SWE maps, covering an in-plane area of ~5 × 5 cm, were acquired in 12 s for a single slice and 144 s for a volumetric scan. MR-SWE detected inclusions of differing stiffness in a phantom experiment. In bovine liver, mean shear wave speed significantly increased from 1.65 ± 0.18 m/s in normal to 2.52 ± 0.18 m/s in ablated region (n = 581 pixels; P-value < 0.001). CONCLUSION MR-SWE is an elastography technique that enables precise targeting and excitation of the desired tissue of interest. MR-SWE may be particularly well suited for treatment planning and endpoint assessment of MR-guided FUS procedures because the same device used for therapy can be used as an excitation source for tissue stiffness quantification.
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Affiliation(s)
- Lorne W Hofstetter
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
| | - Henrik Odéen
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
| | | | - Alexander Mueller
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
| | - Douglas A Christensen
- Department of Bioengineering, University of Utah, Salt Lake City, Utah
- Department of Electrical and Computer Engineering, University of Utah, Salt Lake City, Utah
| | - Allison Payne
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
| | - Dennis L Parker
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
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Odéen H, de Bever J, Hofstetter LW, Parker DL. Multiple-point magnetic resonance acoustic radiation force imaging. Magn Reson Med 2018; 81:1104-1117. [PMID: 30257059 PMCID: PMC6642829 DOI: 10.1002/mrm.27477] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [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: 03/06/2018] [Revised: 07/09/2018] [Accepted: 07/11/2018] [Indexed: 12/13/2022]
Abstract
PURPOSE To implement and evaluate an efficient multiple-point MR acoustic radiation force imaging pulse sequence that can volumetrically measure tissue displacement and evaluate tissue stiffness using focused ultrasound (FUS) radiation force. METHODS Bipolar motion-encoding gradients were added to a gradient-recalled echo segmented EPI pulse sequence with both 2D and 3D acquisition modes. Multiple FUS-ON images (FUS power > 0 W) were interleaved with a single FUS-OFF image (FUS power = 0 W) on the TR level, enabling simultaneous measurements of volumetric tissue displacement (by complex subtraction of the FUS-OFF image from the FUS-ON images) and proton resonance frequency shift MR thermometry (from the OFF image). Efficiency improvements included partial Fourier acquisition, parallel imaging, and encoding up to 4 different displacement positions into a single image. Experiments were performed in homogenous and dual-stiffness phantoms, and in ex vivo porcine brain. RESULTS In phantoms, 16-point multiple-point magnetic resonance acoustic radiation force imaging maps could be acquired in 5 s to 10 s for a 2D slice, and 60 s for a 3D volume, using parallel imaging and encoding 2 displacement positions/image. In ex vivo porcine brain, 16-point multiple-point magnetic resonance acoustic radiation force imaging maps could be acquired in 20 s for a 3D volume, using partial Fourier and parallel imaging and encoding 4 displacement positions/image. In 1 experiment it was observed that tissue displacement in ex vivo brain decreased by approximately 22% following FUS ablation. CONCLUSION With the described efficiency improvements it is possible to acquire volumetric multiple-point magnetic resonance acoustic radiation force imaging maps, with simultaneous proton resonance frequency shift MR thermometry maps, in clinically acceptable times.
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Affiliation(s)
- Henrik Odéen
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
| | - Joshua de Bever
- Department of Radiology, Stanford University, Palo Alto, California
| | - Lorne W Hofstetter
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
| | - Dennis L Parker
- Department of Radiology and Imaging Sciences, University of Utah, Salt Lake City, Utah
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Hofstetter LW, Yeo DTB, Dixon WT, Marinelli L, Foo TK. Referenced MR thermometry using three-echo phase-based fat water separation method. Magn Reson Imaging 2018; 49:86-93. [PMID: 29409819 DOI: 10.1016/j.mri.2018.01.002] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Revised: 01/25/2018] [Accepted: 01/27/2018] [Indexed: 12/24/2022]
Abstract
A three-point image reconstruction method for internally referenced MR thermometry was developed. The technique exploits the fact that temperature-induced changes in the water resonance frequency are small relative to the chemical shift difference between water and fat signals. This property enabled the use of small angle approximations to derive an analytic phase-based fat-water separation method for MR thermometry. Ethylene glycol and cream cool-down experiments were performed to validate measurement technique. Over a cool-down temperature range of 20 °C, maximum deviation between probe and MR measurement (averaged over 1.3 cm3 region surrounding probe) was 0.6 °C and 1.1 °C for ethylene glycol and cream samples, respectively.
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Affiliation(s)
| | | | - W Thomas Dixon
- Department of Radiology, Emory University, Atlanta, GA, USA.
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10
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de Bever JT, Odéen H, Hofstetter LW, Parker DL. Simultaneous MR thermometry and acoustic radiation force imaging using interleaved acquisition. Magn Reson Med 2017; 79:1515-1524. [PMID: 28795419 DOI: 10.1002/mrm.26827] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2017] [Revised: 05/15/2017] [Accepted: 06/15/2017] [Indexed: 12/25/2022]
Abstract
PURPOSE A novel and practical method for simultaneously performing MR acoustic radiation force imaging (ARFI) and proton resonance frequency (PRF)-shift thermometry has been developed and tested. This could be an important tool for evaluating the success of MR-guided focused ultrasound procedures for which MR-thermometry measures temperature and thermal dose and MR-ARFI detects changes in tissue mechanical properties. METHODS MR imaging was performed using a gradient recalled echo segmented echo-planar imaging pulse sequence with bipolar motion encoding gradients (MEG). Images with ultrasound pulses (ON) and without ultrasound pulses (OFF) during the MEG were interleaved at the repetition time (TR) level. ARFI displacements were calculated by complex subtraction of ON-OFF images, and PRF temperature maps were calculated by baseline subtraction. Evaluations in tissue-mimicking phantoms and ex vivo porcine brain tissue were performed. Constrained reconstruction improved the temporal resolution of dynamic measurements. RESULTS Simultaneous maps of displacement and temperature were acquired in 2D and 3D while keeping tissue heating < 1°C. Accuracy of the temperature maps was comparable to the standard PRF sequence. Using constrained reconstruction and subsampled k-space (R = 4.33), 3D simultaneous temperature and displacement maps can be acquired every 4.7 s. CONCLUSION This new sequence acquires simultaneous temperature and displacement maps with minimal tissue heating, and can be applied dynamically for monitoring tissue mechanical properties during ablation procedures. Magn Reson Med 79:1515-1524, 2018. © 2017 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
- Joshua T de Bever
- School of Computing, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA.,Department of Radiology, Stanford University, Stanford, California, USA
| | - Henrik Odéen
- Department of Radiology and Imaging Sciences, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
| | - Lorne W Hofstetter
- Department of Radiology and Imaging Sciences, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
| | - Dennis L Parker
- Department of Radiology and Imaging Sciences, Utah Center for Advanced Imaging Research, University of Utah, Salt Lake City, Utah, USA
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Hofstetter LW, Morrell G, Kaggie J, Kim D, Carlston K, Lee VS. T2* Measurement bias due to concomitant gradient fields. Magn Reson Med 2016; 77:1562-1572. [PMID: 27186845 DOI: 10.1002/mrm.26240] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Revised: 03/16/2016] [Accepted: 03/18/2016] [Indexed: 12/12/2022]
Abstract
PURPOSE To demonstrate that concomitant magnetic fields can cause significant spatially dependent biases in T2* relaxometry measurements with implications for clinical applications such as BOLD and dynamic susceptibility contrast-enhanced MRI. THEORY AND METHODS After developing a theoretical framework for intravoxel dephasing and signal loss from concomitant magnetic fields, this framework and the effect of concomitant fields on T2* are validated with phantom experiments and numerical simulation. In lower leg and renal T2* mapping, we quantify measurement bias for imaging protocols with high gradient amplitude multiecho readouts, comparable to those used in clinical applications. RESULTS Concordance between phantom experiment and numerical simulation validate the theoretical framework. Changes in T2* measured in the lower leg and kidney varied by up to 15% and 35%, respectively, as a result of concomitant gradient effects when compared with the control measurements. CONCLUSION Concomitant magnetic fields produced by imaging gradient coils can cause clinically significant T2* mapping errors when high amplitude, long duration gradient waveforms are used. While we have shown that measurement biases can be quite large, modification of imaging parameters can potentially reduce concomitant field-induced measurement errors to acceptable levels. Magn Reson Med 77:1562-1572, 2017. © 2016 International Society for Magnetic Resonance in Medicine.
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Affiliation(s)
| | - Glen Morrell
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA
| | - Joshua Kaggie
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA.,Department of Radiology, University of Cambridge, Cambridge, United Kingdom
| | - Daniel Kim
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA.,Department of Radiology, Northwestern University Feinberg School of Medicine, Chicago, Illinois, USA
| | - Kristi Carlston
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA
| | - Vivian S Lee
- Department of Radiology, University of Utah, Salt Lake City, Utah, USA
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Tarasek MR, Pellicer R, Hofstetter LW, Numan WCM, Bakker JF, Kotek G, Togni P, Verhaart RF, Fiveland EW, Houston GC, van Rhoon GC, Paulides MM, Yeo DTB. Validation of MR thermometry: method for temperature probe sensor registration accuracy in head and neck phantoms. Int J Hyperthermia 2015; 30:142-9. [PMID: 24571177 DOI: 10.3109/02656736.2014.887794] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
PURPOSE Magnetic resonance thermometry (MRT) is an attractive means to non-invasively monitor in vivo temperature during head and neck hyperthermia treatments because it can provide multi-dimensional temperature information with high spatial resolution over large regions of interest. However, validation of MRT measurements in a head and neck clinical set-up is crucial to ensure the temperature maps are accurate. Here we demonstrate a unique approach for temperature probe sensor localisation in head and neck hyperthermia test phantoms. METHODS We characterise the proton resonance frequency shift temperature coefficient and validate MRT measurements in an oil-gel phantom by applying a combination of MR imaging and 3D spline fitting for accurate probe localisation. We also investigate how uncertainties in both the probe localisation and the proton resonance frequency shift (PRFS) thermal coefficient affect the registration of fibre-optic reference temperature probe and MRT readings. RESULTS The method provides a two-fold advantage of sensor localisation and PRFS thermal coefficient calibration. We provide experimental data for two distinct head and neck phantoms showing the significance of this method as it mitigates temperature probe localisation errors and thereby increases accuracy of MRT validation results. CONCLUSIONS The techniques presented here may be used to simplify calibration experiments that use an interstitial heating device, or any heating method that provides rapid and spatially localised heat distributions. Overall, the experimental verification of the data registration and PRFS thermal coefficient calibration technique provides a useful benchmarking method to maximise MRT accuracy in any similar context.
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Affiliation(s)
- Matthew R Tarasek
- GE Global Research, Diagnostics and Biomedical Technologies, One Research Circle , Niskayuna, New York , USA
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Numan WC, Hofstetter LW, Kotek G, Bakker JF, Fiveland EW, Houston GC, Kudielka G, Yeo DT, Paulides MM. Exploration of MR-guided head and neck hyperthermia by phantom testing of a modified prototype applicator for use with proton resonance frequency shift thermometry. Int J Hyperthermia 2014; 30:184-91. [DOI: 10.3109/02656736.2014.910615] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Paulides MM, Bakker JF, Hofstetter LW, Numan WCM, Pellicer R, Fiveland EW, Tarasek M, Houston GC, van Rhoon GC, Yeo DTB, Kotek G. Laboratory prototype for experimental validation of MR-guided radiofrequency head and neck hyperthermia. Phys Med Biol 2014; 59:2139-54. [DOI: 10.1088/0031-9155/59/9/2139] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Hofstetter LW, Yeo DTB, Dixon WT, Kempf JG, Davis CE, Foo TK. Fat-referenced MR thermometry in the breast and prostate using IDEAL. J Magn Reson Imaging 2012; 36:722-32. [PMID: 22581513 DOI: 10.1002/jmri.23692] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2011] [Accepted: 04/02/2012] [Indexed: 11/05/2022] Open
Abstract
PURPOSE To demonstrate a three-echo fat-referenced MR thermometry technique that estimates and corrects for time-varying phase disturbances in heterogeneous tissues. MATERIALS AND METHODS Fat protons do not exhibit a temperature-dependent frequency shift. Fat-referenced thermometry methods exploit this insensitivity and use the signal from fat to measure and correct for magnetic field disturbances. In this study, we present a fat-referenced method that uses interpolation of the fat signal to correct for phase disturbances in fat free regions. Phantom and ex vivo tissue cool-down experiments were performed to evaluate the accuracy of this method in the absence of motion. Non-heated in vivo imaging of the breast and prostate was performed to demonstrate measurement robustness in the presence of systemic and motion-induced field disturbances. Measurement accuracy of the method was compared to conventional proton resonance frequency shift MR thermometry. RESULTS In the ex vivo porcine tissue experiment, maximum measurement error of the fat-referenced method was reduced 42% from 3.3 to 1.9°C when compared to conventional MR thermometry. In the breasts, measurement errors were reduced by up to 70% from 6.4 to 1.9°C. CONCLUSION Ex vivo and in vivo results show that the proposed method reduces measurement errors in the heterogeneous tissue experiments when compared to conventional MR thermometry.
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