An MRI-Guided Ring High-Intensity Focused Ultrasound System for Noninvasive Breast Ablation

Study on the heating law of thermal effect of HIFU on tissue based on piezoelectric ceramic voltage and vibration frequency

When high-intensity focused ultrasound (HIFU) is used to heat human tissues during surgery, shortening the heating time and increasing the heating rate are crucial for implementing surgery. During operations, the vibration frequencies and voltages that are suitable for piezoelectric ceramics can maximize the heating rate of HIFU. To correctly select the frequency and voltage of piezoelectric ceramics, it is necessary to understand the change law between the frequency and voltage of piezoelectric ceramics and the temperature of the heated tissue. Therefore, this study focuses on the piezoelectric ceramics in the ultrasonic transducer that produces HIFU. By coupling the piezoelectric equation, Helmholtz equation, and biological heat transfer equation of piezoelectric ceramics, the solid mechanical properties of piezoelectric ceramics and the sound field and temperature field produced by its vibration are combined to determine the influence of vibration frequency and voltage on heating time. Results show that the relation between the temperature variation of the tissue, vibration frequency, and voltage of the piezoelectric ceramics can be determined using the Rational Taylor function. The maximum voltage that the piezoelectric ceramics with different frequencies can withstand varies greatly.

Agar-based Phantom for Evaluating Targeting of High-intensity Focused Ultrasound Systems for Breast Ablation

AIM

Phantoms are often utilized for the preclinical evaluation of novel high-intensity focused ultrasound (HIFU) systems, serving as valuable tools for validating efficacy. In the present study, the feasibility of a homogeneous agar-based breast-shaped phantom as a tool for the preclinical evaluation of HIFU systems dedicated to breast cancer was assessed. Specifically, the effect of the increased phantom curvature on temperature increase was examined through sonications executed on two sides having varied curvatures.

MATERIALS AND METHODS

Assessment was performed utilizing a 1.1 MHz focused transducer. Sonications on the two phantom sides were executed at varied acoustical power in both a laboratory setting and inside a 1.5 T magnetic resonance imaging scanner. Sonications were independently performed on two identical phantoms for repeatability purposes.

RESULTS

Temperature changes between 7.1°C-34.3°C and 5.1°C-21.5°C were recorded within the decreased and increased curvature sides, respectively, for acoustical power of 3.75-10 W. High-power sonications created lesions which were approximately symmetrically formed around the focal point at the decreased curvature side, while they were shifted away from the focal point at the increased curvature side.

CONCLUSIONS

The present findings indicate that increased curvature of the breast phantom results in deformed focal shapes and decreased temperatures induced at the focal area, thus suggesting treatment correction requirements in the form of focus control or accurate robotic movement. The developed breast-shaped phantom can be utilized as an evaluation tool of HIFU systems dedicated to breast cancer since it can visually verify the efficacy of any system.

Breast Tomographic Ultrasound: The Spectrum from Current Dense Breast Cancer Screenings to Future Theranostic Treatments

This review provides unique insights to the scientific scope and clinical visions of the inventors and pioneers of the SoftVue breast tomographic ultrasound (BTUS). Their >20-year collaboration produced extensive basic research and technology developments, culminating in SoftVue, which recently received the Food and Drug Administration's approval as an adjunct to breast cancer screening in women with dense breasts. SoftVue's multi-center trial confirmed the diagnostic goals of the tissue characterization and localization of quantitative acoustic tissue differences in 2D and 3D coronal image sequences. SoftVue mass characterizations are also reviewed within the standard cancer risk categories of the Breast Imaging Reporting and Data System. As a quantitative diagnostic modality, SoftVue can also function as a cost-effective platform for artificial intelligence-assisted breast cancer identification. Finally, SoftVue's quantitative acoustic maps facilitate noninvasive temperature monitoring and a unique form of time-reversed, focused US in a single theranostic device that actually focuses acoustic energy better within the highly scattering breast tissues, allowing for localized hyperthermia, drug delivery, and/or ablation. Women also prefer the comfort of SoftVue over mammograms and will continue to seek out less-invasive breast care, from diagnosis to treatment.

Sono-activated materials for enhancing focused ultrasound ablation: Design and application in biomedicine

The ablation effect of focused ultrasound (FUS) has played an increasingly important role in the biomedical field over the past decades, and its non-invasive features have great advantages, especially for clinical diseases where surgical treatment is not available or appropriate. Recently, rapid advances in the adjustable morphology, enzyme-mimetic activity, and biostability of sono-activated materials have significantly promoted the medical application of FUS ablation. However, a systematic review of sono-activated materials based on FUS ablation is not yet available. This progress review focuses on the recent design, fundamental principles, and applications of sono-activated materials in the FUS ablation biomedical field. First, the different ablation mechanisms and the key factors affecting ablation are carefully determined. Then, the design of sono-activated materials with high FUS ablation efficiencies is comprehensively discussed. Subsequently, the representative biological applications are summarized in detail. Finally, the primary challenges and future perspectives are also outlined. We believe this timely review will provide key information and insights for further exploration of focused ultrasound ablation and new inspiration for designing future sono-activated materials. STATEMENT OF SIGNIFICANCE: The ablation effect of focused ultrasound (FUS) has played an increasingly important role in the biomedical field over the past decades. However, there are also some challenges of FUS ablation, such as skin burns, tumour recurrence after thermal ablation, and difficulty in controlling cavitation ablation. The rapid advance in adjustable morphology, enzyme-mimetic activity, and biostability of sono-activated materials has significantly promoted the medical application of FUS ablation. However, the systematic review of sono-activated materials based on FUS ablation is not yet available. This progress review focuses on the recent design, fundamental principles, and applications in the FUS ablation biomedical field of sono-activated materials. We believe this timely review will provide key information and insights for further exploration of FUS ablation.

Advanced software for MRgFUS treatment planning

BACKGROUND AND OBJECTIVES

Herein, a user-friendly software platform for 3-dimensional Focused Ultrasound treatment planning based on Magnetic Resonance Imaging (MRI) images is presented.

METHODS

The software directly retrieves and loads MRI images. Various design tools can be used on the MRI images to define the treatment area and the sonication parameters. Based on the treatment plan, the software controls the robotic motion and motion pattern of Magnetic Resonance guided Focused Ultrasound (MRgFUS) robotic systems to execute the treatment procedure. Real-time treatment monitoring is achieved through MRI images and thermometry. The software's functionality and performance were evaluated in both laboratory and MRI environments. Different treatment plans were designed on MRI images and sonications were executed on agar-based phantoms and polymer films.

RESULTS

Magnetic Resonance (MR) thermometry maps were acquired in the agar-based phantoms. An exceptional agreement was observed between the software-planned treatment area and the lesions produced on the polymer films.

CONCLUSIONS

The developed software was successfully integrated with the MRI and robotic system controls for performing accurate treatment planning and real-time monitoring during sonications. The software provides an extremely user-friendly interface, while in the future it could be enhanced by providing dynamic modulation of the ultrasonic parameters during the treatment process.

Injury Prevention Effect of MRI Imaging Technology in Physical Education and Sports Training

In order to solve the problem of observing and analyzing the clinical value of MRI diagnosis in patients with knee sports injury and guiding clinical targeted treatment, the author proposed a sports injury prevention method in sports training teaching based on MRI image observation. This method retrospectively analyzed the imaging data of 101 patients with knee joint MRI examination due to osteoarthritis, sports injury and synovitis in joint surgery, and arthroscopic exclusion of true meniscus tear, MR multisequence and multiplane scans were performed to observe the anatomical features of TGL and MFL images and the occurrence rate of the lateral meniscus "false tear sign," and the χ ² test was used to compare the occurrence rate of "pseudo-tear sign" between genders and sides. Experimental results show that the incidence of TGL on MRI was about 67.3% (68/101), and the incidence of "pseudo-tear sign" in the anterior horn of the lateral meniscus caused by TGL was 2.9% (2/68). The overall appearance rate of MFL on MRI was 91.1% (92/101), the appearance rate of plate anterior ligament (HL) was 13.9% (14/101), and the occurrence rate of "pseudo-tear sign" in the posterior horn of the lateral meniscus caused by HL was 7.1% (1/14). The occurrence rate of the posterior ligament (WL) was 77.2% (78/101), and the incidence of "pseudo-tear sign" in the posterior horn was 20.5% (16/78). According to the shape and course of TGL and MFL on MRI, and the direction and position of the lateral meniscus pseudotear, combined with MRI sagittal plane and coronal plane observation, it can effectively identify the true and false attributes of lateral meniscus anterior and posterior horn tears, thereby reducing unnecessary surgical treatment.

Golay-Encoded Ultrasound Monitoring of Simultaneous High-Intensity Focused Ultrasound Treatment: A Phantom Study

Ultrasound (US) imaging has high potential in monitoring high-intensity focused US (HIFU) treatment due to its superior temporal resolution. However, US monitoring is often hindered by strong HIFU interference, which overwhelms the echoes received by the imaging array. In this study, a method of Golay-encoded US monitoring is proposed to visualize the imaged object for simultaneous HIFU treatment. It effectively removes HIFU interference patterns in real-time B-mode imaging and improves the metrics of image quality, such as peak signal-to-noise ratio (PSNR), structural similarity (SSIM), and contrast ratio (CR). Compared to the pulse-inversion sequence, the N -bit Golay sequence can boost the echo magnitude of US monitoring by another N times and, thus, exhibits higher robustness. Simulations show that a sinusoidal HIFU waveform can be fully eliminated using Golay decoding when the bit duration of the N -bit Golay sequence ( N is the power of 4) coincides with either odd (Case I) or even (Case II) integer multiples of the HIFU quarter period. Experimental results also show that the Golay decoding with Case II can increase the PSNR of US monitoring images by more than 30 dB for both pulse- and continuous-wave HIFU transmissions. The SSIM index also effectively improves to about unity, indicating that the B-mode image with HIFU transmission is visually indistinguishable from that acquired without HIFU transmission. Though Case I is inferior to Case II in the elimination of even-order HIFU harmonic, they together enable a more flexible selection of imaging frequencies to meet the required image resolution and penetration for Golay-encoded US monitoring.

Multi-Task/Single-Task Joint Learning of Ultrasound BI-RADS Features

Breast cancer is one of the most common cancers among women in the world. The breast imaging reporting and data system (BI-RADS) features effectively improve the accuracy and sensitivity of breast tumors. Based on the description of signs in BI-RADS, a quantitative scoring scheme is proposed based on ultrasound (US) data. This scheme includes feature extraction of high-level semantic, that is, an intermediate step interpreting the subsequent diagnosis. However, the scheme requires doctors to score the features of breast data, which is labor-intensive. To reduce the burden of doctors, we design a multi-task learning (MTL) framework, which can directly output the scores of different BI-RADS features from the raw US images. The MTL framework consists of a shared network that learns global features and K soft attention networks for different BI-RADS features. Thus, it enables the network not only to learn the potential correlation among different BI-RADS features, but also learn the unique specificity of each feature, which can assist each other and jointly improve the scoring accuracy. In addition, we group different BI-RADS features according to the correlation among tasks and build a multi-task/single-task joint framework. Experimental results on the US breast tumor dataset collected from 1859 patients with 4458 US images show that the proposed BI-RADS feature scoring framework achieves an average scoring accuracy of 84.91% for 11 BI-RADS features on the test dataset, which is helpful for the subsequent diagnosis of breast tumors.

Innovative use of magnetic resonance imaging-guided focused ultrasound surgery for non-invasive breast cancer: a report of two cases

Objective

This report describes the first clinical experience with magnetic resonance imaging-guided focused ultrasound surgery (MRgFUS) using the ExAblate 2100 system for non-invasive breast cancer.

Methods

Two women with non-invasive breast cancer underwent MRgFUS treatment. One week after the MRgFUS treatment, US-guided vacuum-assisted biopsy was performed for the ablated lesions at the same time as breast-conserving surgery.

Results

The patients experienced good cosmetic outcomes and did not experience any severe adverse events, such as skin burns. Pathological examination of the surgical specimens revealed a few degenerated intraductal lesions around the breast biopsy markers.

Conclusion

Performing MRgFUS with the new ExAblate 2100 system appears to be safe and feasible. The histopathological results revealed that adequate ultrasound energy in the appropriate location can induce tumor necrosis.