Simultaneous MR thermometry and acoustic radiation force imaging using interleaved acquisition

Bever, Joshua T. de; Odéen, Henrik; Hofstetter, Lorne W.; Parker, Dennis L.

doi:10.1002/mrm.26827

Cited by 25 publications

(30 citation statements)

References 50 publications

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“…Acoustic radiation force (ARF) displacements were created using a 256element phased-array ultrasound transducer (Imasonic, Besançon, France, and Image Guided Therapy, Bordeaux, France; frequency ¼ 1 MHz, focal spot full width at half maximum ¼ 2 Â 2Â8 mm). ARF displacements were precisely timed with motion encoding gradients (MEG) and were interleaved on the TR level using a method described previously [31]. A focused ultrasound impulse of 58 acoustic watts was supplied for 10 ms to generate the ARF displacement.…”

Section: Phantom Characterization: Mr Propertiesmentioning

confidence: 99%

Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging

Hofstetter

Fausett

Mueller

et al. 2020

International Journal of Hyperthermia

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2020) Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging, 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 Ã 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/(cmÁMHz). Measured T1 ranged from 974-1051 ms. The T2 and T2 Ã 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. ARTICLE HISTORY

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Section: Phantom Characterization: Mr Propertiesmentioning

confidence: 99%

Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging

Hofstetter

Fausett

Mueller

et al. 2020

International Journal of Hyperthermia

Self Cite

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“…36,38,[41][42][43][44][45] Methods to simultaneously measure tissue displacement with MR-ARFI and tissue temperature change using the PRFS method have further been described. 34,36,46,47 Although MR-ARFI has been used previously to interrogate changes in tissue stiffness, these measurements have only been performed for 1 small focal region. To use tissue stiffness changes to determine the treatment endpoint, it will likely be necessary to interrogate a larger volume of tissue, which will be far too time-consuming to perform with existing MR-ARFI techniques.…”

Section: Magnetic Resonance In Medicinementioning

confidence: 99%

“…Multiple 2D or 3D image volumes with the FUS-ON (i.e., Power [P] > 0 W) and a single image volume with the FUS-OFF (i.e., P = 0 W) are interleaved on the TR level. 51 All FUS-ON images use electronic steering to move the FUS focal spot to a separate spatial position. The FUS-ON images accrue phase from both tissue displacement during the MEG, Δ D , and from tissue heating, Δ T , as Δ ON = Δ D +Δ T according to where is the gyromagnetic ratio (in Hz/T), MEG (t) are the time-dependent MEGs (in mT/m), ΔD is the tissue displacement (in m), is the duration of the MEG (in seconds), is the PRFS constant (assumed to be −0.010 ppm/°C throughout this work), B 0 is the main magnetic field strength (in T), and ΔT is the temperature change (in °C).…”

Section: Pulse Sequencementioning

confidence: 99%

“…The FUS-OFF image can further be used to calculate an accurate PRFS temperature map, as it was interleaved with the FUS-ON images. 51 This can be done either by acquiring a baseline image before the start of the mpARFI experiment, or by using referenceless PRFS reconstruction. 52,53 Three different approaches were investigated to improve the efficiency of acquiring the mpARFI data.…”

Section: Magnetic Resonance In Medicinementioning

confidence: 99%

“…Furthermore, it can be postulated that the mpARFI technique can be combined with high duty-cycle FUS to simultaneously ablate tissue and measure temperature and displacement in multiple focal positions, similar to what has previously been described for single-point ablations. 47,51 Three different techniques for improving acquisition efficiency and decrease acquisition time were investigated in this work: (1) partial Fourier imaging, (2) parallel imaging, and (3) sonicating at multiple spatial locations in a single TR, which is the most novel aspect of this work and unique to the mpARFI technique.…”

Section: Magnetic Resonance In Medicinementioning

confidence: 99%

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Multiple‐point magnetic resonance acoustic radiation force imaging

Odéen

Bever

Hofstetter

et al. 2018

Magnetic Resonance in Med

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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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Evaluation of Focal Laser Ablation of Prostate Cancer Using High Spectral and Spatial Resolution Imaging: A Pilot Study

Wang

Fan

Yousuf

et al. 2018

Magnetic Resonance Imaging

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Background Focal laser ablation (FLA) is a minimally invasive thermal ablation, guided by MRI through an optical fiber, to induce coagulative necrosis in cancer. Purpose To evaluate the feasibility of high spectral and spatial resolution imaging using multiecho gradient echo (MEGE) MRI for identification of ablation zones, after FLA of prostate cancers. Study Type Prospective. Population Fourteen patients with biopsy‐confirmed localized prostate cancers. Field Strength/Sequence FLA was performed under monitored conscious sedation with a 1.5T MRI scanner. Axial MEGE images were acquired before and after the last FLA. Pre‐ and postcontrast enhanced T1‐weighted (pT1W) images were acquired to assess the FLA zone as a reference standard. Assessment The normalT2* maps and water resonance peak height (WPH) images were calculated from the MEGE data. Ablation area was outlined using an active contour method. The maximum ablation area and total ablation volume were calculated from normalT2* and WPH images, and compared with the sizes measured from pT1W images. Statistical Tests Nonparametric Kruskal–Wallis tests were performed to determine whether there was significant difference in calculated ablation areas and volumes between normalT2*, WPH, and pT1W images. Results Average normalT2* (38.9 ± 14.1 msec) in the ablation area was significantly shorter (P = 0.03) than the preablation area normalT2* (57.8 ± 25.3 msec). The normalized WPH value over the ablation area (1.3 ± 0.6) was significantly decreased (P = 0.02) more than the preablation area (2.0 ± 0.9). The maximum ablation areas measured by normalT2* (295.7 ± 96.4 mm2), WPH (312.2 ± 63.0 mm2), and pT1W (320.3 ± 82.9 mm2) images were all similar. Furthermore, there was no significant difference (P = 0.31) for measured ablation volumes 3310.5 ± 649.5, 3406.4 ± 684.9, and 3672.5 ± 832.4 mm3 between normalT2*, WPH, and pT1W images, respectively. Data Conclusion normalT2* and WPH images provide acceptable measurements of ablation zones during FLA treatment of prostate cancers without the need for contrast agent injection. This might allow repeated assessment following each heating period so that subsequent ablations can be optimized. Level of Evidence: 2 Technical Efficacy: Stage 5 J. Magn. Reson. Imaging 2019;49:1374–1380.

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Simultaneous MR thermometry and acoustic radiation force imaging using interleaved acquisition

Cited by 25 publications

References 50 publications

Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging

Development and characterization of a tissue mimicking psyllium husk gelatin phantom for ultrasound and magnetic resonance imaging

Multiple‐point magnetic resonance acoustic radiation force imaging

Evaluation of Focal Laser Ablation of Prostate Cancer Using High Spectral and Spatial Resolution Imaging: A Pilot Study

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