Head phantoms for transcranial focused ultrasound

Eames, Matthew; Farnum, Mercy; Khaled, Mohamad; Elias, W. Jeff; Hananel, Arik; Snell, John; Kassell, Neal F.; Aubry, Jean‐François

doi:10.1118/1.4907959

Cited by 20 publications

(9 citation statements)

References 42 publications

(35 reference statements)

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“…It is worth mentioning here that the transducer used in this proof of concept paper has a low f-number (F/D = 0.91) compared to current transcranial therapy transducers for which F/D is ranging between 0.7 [56] and 0.5 [63][64][65]. Further work needs to be done with a larger aperture transducer in order to assess the potential of the lens-based correction for transcranial thermal ablation with an antenna gain similar to current clinical transcranial ultrasonic neurosurgery devices.…”

Section: Discussionmentioning

confidence: 99%

Steering Capabilities of an Acoustic Lens for Transcranial Therapy: Numerical and Experimental Studies

Maimbourg

Houdouin

Thomas

et al. 2020

IEEE Trans. Biomed. Eng.

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Brain therapy by transcranial focused ultrasound needs to compensate for the delays locally induced by the skull. The patient-specific phase profile is currently generated by a multi-element array with a growing number of elements. We recently introduced a disruptive approach, consisting in using a single element transducer coupled to an acoustic lens of controlled thickness: by adjusting the local thickness of the lens, we were able to induce a phase difference which compensated that of the skull. Nevertheless, such an approach suffers from an apparent limitation: the lens is a priori designed for one specific target. In this paper, we demonstrate the possibility of taking advantage of the isoplanatic angle of the aberrating skull in order to steer the focus by mechanically moving the transducer/acoustic lens pair around its initial focusing position. This study, conducted on three human skull samples, confirms that tilting of the transducer with the lens restores a single focus at 914 kHz for a steering up to 11mm in the transverse direction, and 10mm in the longitudinal direction, around the initial focal region. Acoustic lens, transcranial ultrasound, therapeutic ultrasound

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Section: Discussionmentioning

confidence: 99%

Steering Capabilities of an Acoustic Lens for Transcranial Therapy: Numerical and Experimental Studies

Maimbourg

Houdouin

Thomas

et al. 2020

IEEE Trans. Biomed. Eng.

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“…The efficiency, E, of each sonication was defined as normalE=normalΔnormalTW, where ΔT is the temperature rise and W is the applied energy, so that E is measured in °C / J. Assuming a linear response between power and temperature, then, one would expect E to remain constant for each patient for a fixed sonication duration 17, 18 . The percentage changes in treatment efficiency and focal size between the minimum and maximum acoustic energies were taken to quantify decreases in efficiency and increases in focal size for each patient.…”

Section: Methodsmentioning

confidence: 99%

“…Assuming a linear response between power and temperature, then, one would expect E to remain constant for each patient for a fixed sonication duration. 17,18 The percentage changes in treatment efficiency and focal size between the minimum and maximum acoustic energies were taken to quantify decreases in efficiency and increases in focal size for each patient. Correlations were then assessed between changes in treatment efficiency and the peak temperatures obtained during the treatment, the peak applied acoustic powers, the peak deposited acoustic energy, the peak sonication durations, the total number of sonications, and the changes in focal size.…”

Section: C Correlation Of Efficiency With Other Treatment Parametersmentioning

confidence: 99%

The reduction in treatment efficiency at high acoustic powers during MR‐guided transcranial focused ultrasound thalamotomy for Essential Tremor

et al. 2018

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“…A gel-filled human skull phantom was sonicated by an Insightec ExAblate Neuro 4000 transcranial MRgFUS system (Insightec Ltd, Haifa, Israel) and imaged at 3T using the body coil (MR750, GE Healthcare, Waukeshaw, WI) [29]. 2DFT gradient echo images were collected with 13 ms TE, 28 ms TR, 28 ×28×0.3 cm 3 field of view, 256 ×128 acquisition matrix, and 30° flip angle.…”

Section: Methodsmentioning

confidence: 99%

Spatially-segmented undersampled MRI temperature reconstruction for transcranial MR-guided focused ultrasound

et al. 2017

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BackgroundVolumetric thermometry with fine spatiotemporal resolution is desirable to monitor MR-guided focused ultrasound (MRgFUS) procedures in the brain, but requires some form of accelerated imaging. Accelerated MR temperature imaging methods have been developed that undersample k-space and leverage signal correlations over time to suppress the resulting undersampling artifacts. However, in transcranial MRgFUS treatments, the water bath surrounding the skull creates signal variations that do not follow those correlations, leading to temperature errors in the brain due to signal aliasing.MethodsTo eliminate temperature errors due to the water bath, a spatially-segmented iterative reconstruction method was developed. The method fits a k-space hybrid signal model to reconstruct temperature changes in the brain, and a conventional MR signal model in the water bath. It was evaluated using single-channel 2DFT Cartesian, golden angle radial, and spiral data from gel phantom heating, and in vivo 8-channel 2DFT data from a FUS thalamotomy. Water bath signal intensity in phantom heating images was scaled between 0-100% to investigate its effect on temperature error. Temperature reconstructions of retrospectively undersampled data were performed using the spatially-segmented method, and compared to conventional whole-image k-space hybrid (phantom) and SENSE (in vivo) reconstructions.ResultsAt 100% water bath signal intensity, 3 ×-undersampled spatially-segmented temperature reconstruction error was nearly 5-fold lower than the whole-image k-space hybrid method. Temperature root-mean square error in the hot spot was reduced on average by 27 × (2DFT), 5 × (radial), and 12 × (spiral) using the proposed method. It reduced in vivo error 2 × in the brain for all acceleration factors, and between 2 × and 3 × in the temperature hot spot for 2-4 × undersampling compared to SENSE.ConclusionsSeparate reconstruction of brain and water bath signals enables accelerated MR temperature imaging during MRgFUS procedures with low errors due to undersampling using Cartesian and non-Cartesian trajectories. The spatially-segmented method benefits from multiple coils, and reconstructs temperature with lower error compared to measurements from SENSE-reconstructed images. The acceleration can be applied to increase volumetric coverage and spatiotemporal resolution.

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Head phantoms for transcranial focused ultrasound

Cited by 20 publications

References 42 publications

Steering Capabilities of an Acoustic Lens for Transcranial Therapy: Numerical and Experimental Studies

Steering Capabilities of an Acoustic Lens for Transcranial Therapy: Numerical and Experimental Studies

The reduction in treatment efficiency at high acoustic powers during MR‐guided transcranial focused ultrasound thalamotomy for Essential Tremor

Spatially-segmented undersampled MRI temperature reconstruction for transcranial MR-guided focused ultrasound

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