Frequency considerations for deep ablation with high‐intensity focused ultrasound: A simulation study

Ellens, Nicholas; Hynynen, Kullervo

doi:10.1118/1.4927060

Cited by 16 publications

(12 citation statements)

References 86 publications

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“…Indeed, a more robust alternative to the random array design is to use ultrasound field simulations to optimize the element distribution to maximize array performance [91, 87, 92], for example, by minimizing grating/side lobes or maximizing the allowable steering range. Computer simulations [93] can also provide useful insights related to optimal array driving frequencies for specific applications [21, 94, 95]. …”

Section: Ultrasound Phased Arraysmentioning

confidence: 99%

Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

Hynynen¹,

Jones²

2016

Phys. Med. Biol.

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104

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Focused ultrasound offers a non-invasive way of depositing acoustic energy deep into the body, which can be harnessed for a broad spectrum of therapeutic purposes, including tissue ablation, the targeting of therapeutic agents, and stem cell delivery. Phased array transducers enable electronic control over the beam geometry and direction, and can be tailored to provide optimal energy deposition patterns for a given therapeutic application. Their use in combination with modern medical imaging for therapy guidance allows precise targeting, online monitoring, and post-treatment evaluation of the ultrasound-mediated bioeffects. In the past there have been some technical obstacles hindering the construction of large aperture, high-power, densely-populated phased arrays and, as a result, they have not been fully exploited for therapy delivery to date. However, recent research has made the construction of such arrays feasible, and it is expected that their continued development will both greatly improve the safety and efficacy of existing ultrasound therapies as well as enable treatments that are not currently possible with existing technology. This review will summarize the basic principles, current statures, and future potential of image-guided ultrasound phased arrays for therapy.

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Section: Ultrasound Phased Arraysmentioning

confidence: 99%

Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

Hynynen¹,

Jones²

2016

Phys. Med. Biol.

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104

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“…Of the 3 HIFU transducer designs tested, the flat (catheter 1) and cylindrical segment or “sector” (catheter 3) transducers penetrated deeper than the transducer with the 360° radial pattern (catheter 2), if only because the latter had a higher driving frequency (Table ) and, hence, a higher attenuation in tissue . Nevertheless, the catheter 2 transducer preserved a ring of tissue and was more efficient at ablating a circular lesion for creating an ablation margin around the vessel, for example (Figure A).…”

Section: Discussionmentioning

confidence: 99%

“…H, Masson's trichrome-stained histology of the lesion (black arrow) in tissue. 45 Nevertheless, the catheter 2 transducer preserved a ring of tissue and was more efficient at ablating a circular lesion for creating an ablation margin around the vessel, for example ( Figure 2A). Gluing or mechanically attaching the HIFU and IV-MRI antenna would certainly provide more robust mounting options than the taping used for catheter 1 and 2 implicated in the failure noted for Figure 5C.…”

Section: Discussionmentioning

confidence: 99%

High‐resolution intravascular MRI‐guided perivascular ultrasound ablation

Liu

Ellens

Williams

et al. 2019

Magnetic Resonance in Med

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Purpose To develop and test in animal studies ex vivo and in vivo, an intravascular (IV) MRI‐guided high‐intensity focused ultrasound (HIFU) ablation method for targeting perivascular pathology with minimal injury to the vessel wall. Methods IV‐MRI antennas were combined with 2‐ to 4‐mm diameter water‐cooled IV‐ultrasound ablation catheters for IV‐MRI on a 3T clinical MRI scanner. A software interface was developed for monitoring thermal dose with real‐time MRI thermometry, and an MRI‐guided ablation protocol developed by repeat testing on muscle and liver tissue ex vivo. MRI thermal dose was measured as cumulative equivalent minutes at 43°C (CEM43). The IV‐MRI IV‐HIFU protocol was then tested by targeting perivascular ablations from the inferior vena cava of 2 pigs in vivo. Thermal dose and lesions were compared by gross and histological examination. Results Ex vivo experiments yielded a 6‐min ablation protocol with the IV‐ultrasound catheter coolant at 3‐4°C, a 30 mL/min flow rate, and 7 W ablation power. In 8 experiments, 5‐ to 10‐mm thick thermal lesions of area 0.5‐2 cm2 were produced that spared 1‐ to 2‐mm margins of tissue abutting the catheters. The radial depths, areas, and preserved margins of ablation lesions measured from gross histology were highly correlated (r ≥ 0.79) with those measured from the CEM43 = 340 necrosis threshold determined by MRI thermometry. The psoas muscle was successfully targeted in the 2 live pigs, with the resulting ablations controlled under IV‐MRI guidance. Conclusion IV‐MRI‐guided, IV‐HIFU has potential as a precision treatment option that could preserve critical blood vessel wall during ablation of nonresectable perivascular tumors or other pathologies.

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“…High intensity focused ultrasound (HIFU) is a non-invasive modality for conducting high temperature thermal therapy [ 1 , 2 ]. HIFU has the capability to induce biological effects deep into the body by delivering acoustic energy at a distance from the source, and to kill the cancer cells in treatment region [ 3 ].…”

Section: Introductionmentioning

confidence: 99%

Identification of Denatured Biological Tissues Based on Time-Frequency Entropy and Refined Composite Multi-Scale Weighted Permutation Entropy during HIFU Treatment

Liu

Qian

2019

Entropy

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Identification of denatured biological tissue is crucial to high intensity focused ultrasound (HIFU) treatment. It is not easy for intercepting ultrasonic scattered echo signals from HIFU treatment region. Therefore, this paper employed time-frequency entropy based on generalized S-transform (GST) to intercept ultrasonic echo signals. First, the time-frequency spectra of ultrasonic echo signal is obtained by GST, which is concentrated around the real instantaneous frequency of the signal. Then the time-frequency entropy is calculated based on time-frequency spectra. The experimental results indicate that the time-frequency entropy of ultrasonic echo signal will be abnormally high when ultrasonic signal travels across the boundary between normal region and treatment region in tissues. Ultrasonic scattered echo signals from treatment region can be intercepted by time-frequency entropy. In addition, the refined composite multi-scale weighted permutation entropy (RCMWPE) is proposed to evaluate the complexity of nonlinear time series. Comparing with multi-scale permutation entropy (MPE) and multi-scale weighted permutation entropy (MWPE), RCMWPE not only measures complexity of signal including amplitude information, but also improves the stability and reliability of multi-scale entropy. The RCMWPE and MPE are applied to 300 cases of actual ultrasonic scattered echo signals (including 150 cases in normal status and 150 cases in denatured status). It is found that the RCMWPE and MPE values of denatured tissues are higher than those of the normal tissues. Both RCMWPE and MPE can be used to distinguish normal tissues and denatured tissues. However, there are fewer feature points in the overlap region between RCMWPE of denatured tissues and normal tissues compared with MPE. The intra-class distance and the inter-class distance of RCMWPE are less and greater respectively than MPE. The difference between denatured tissues and normal tissues is more obvious when RCMWPE is used as the characteristic parameter. The results of this study will be helpful to guide doctors to obtain more accurate assessment of treatment effect during HIFU treatment.

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Frequency considerations for deep ablation with high‐intensity focused ultrasound: A simulation study

Cited by 16 publications

References 86 publications

Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

Image-guided ultrasound phased arrays are a disruptive technology for non-invasive therapy

High‐resolution intravascular MRI‐guided perivascular ultrasound ablation

Identification of Denatured Biological Tissues Based on Time-Frequency Entropy and Refined Composite Multi-Scale Weighted Permutation Entropy during HIFU Treatment

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