Effect of Overpressure on Acoustic Emissions and Treated Tissue Histology in ex Vivo Bulk Ultrasound Ablation.

Bulk ultrasound ablation is a thermal therapy approach in which tissue is heated by unfocused or weakly focused sonication (average intensities on the order of 100 W/cm) to achieve coagulative necrosis within a few minutes exposure time. Assessing the role of bubble activity, including acoustic cavitation and tissue vaporization, in bulk ultrasound ablation may help in making bulk ultrasound ablation safer and more effective for clinical applications. Here, two series of ex vivo ablation trials were conducted to investigate the role of bubble activity and tissue vaporization in bulk ultrasound ablation.

Real-Time Volumetric Thermoacoustic Imaging and Thermometry Using a 1.5-D Ultrasound Array.

Noninvasive thermal therapies for the treatment of breast cancer depend on accurate monitoring of tissue temperature to optimize treatment and ensure safety. This work describes a real-time system for 3-D thermoacoustic imaging and thermometry (TAI-TAT) for tracking temperature in tissue samples during heating. The study combines a 2.

Frontiers of cancer imaging and guided therapy using ultrasound, light, and microwaves.

This review describes emerging techniques within the last 5 years that employ ultrasound for detecting and staging malignancy, tracking metastasis, and guiding treatment. Ultrasound elastography quantifies soft tissue elastic properties that change as a tumor grows and proliferates. Hybrid imaging modalities that combine ultrasound with light or microwave energy provide novel contrast for mapping blood oxygen saturation, transport of particles through lymphatic vessels and nodes, and real-time feedback for guiding needle biopsies.

Quantitative Ultrasound for Monitoring High-Intensity Focused Ultrasound Treatment In Vivo.

The success of any minimally invasive treatment procedure can be enhanced significantly if combined with a robust noninvasive imaging modality that can monitor therapy in real time. Quantitative ultrasound (QUS) imaging has been widely investigated for monitoring various treatment responses such as chemotherapy, radiation, and thermal therapy. Previously, we demonstrated the feasibility of using spectral-based QUS parameters to monitor high-intensity focused ultrasound (HIFU) treatment of in situ tumors in euthanized rats [Ultrasonic Imaging 36(4), 239-255, 2014].

Quantitative ultrasound imaging for monitoring in situ high-intensity focused ultrasound exposure.

Quantitative ultrasound (QUS) imaging is hypothesized to map temperature elevations induced in tissue with high spatial and temporal resolution. To test this hypothesis, QUS techniques were examined to monitor high-intensity focused ultrasound (HIFU) exposure of tissue. In situ experiments were conducted on mammary adenocarcinoma tumors grown in rats and lesions were formed using a HIFU system.

In vivo thermal ablation monitoring using ultrasound echo decorrelation imaging.

Previous work indicated that ultrasound echo decorrelation imaging can track and quantify changes in echo signals to predict thermal damage during in vitro radiofrequency ablation (RFA). In the in vivo studies reported here, the feasibility of using echo decorrelation imaging as a treatment monitoring tool was assessed. RFA was performed on normal swine liver (N = 5), and ultrasound ablation using image-ablate arrays was performed on rabbit liver implanted with VX2 tumors (N = 2).

Assessment of high-intensity focused ultrasound treatment of rodent mammary tumors using ultrasound backscatter coefficients.

Fischer 344 rats with subcutaneous mammary adenocarcinoma tumors were exposed to therapeutic ultrasound at one of three exposure levels (335, 360, and 502 W/cm(2) spatial-peak temporal-average intensity). Quantitative ultrasound estimates were generated from ultrasound radio frequency (RF) data from tumors before and after high-intensity focused ultrasound treatment. Treatment outcome was independently assessed by triphenyl tetrazolium chloride (TTC) staining, histological analysis by a pathologist, and thermocouple data.

Amplitude modulated chirp excitation to reduce grating lobes and maintain ultrasound intensity at the focus of an array.

During application of high intensity focused ultrasound (HIFU) with therapy arrays, the existence of grating lobes can cause heating at unintended tissue regions. Therefore, the reduction of grating lobes in therapeutic arrays is an important goal. One way to reduce the grating lobes in therapy arrays is to excite the arrays with broadband signals (defined here as >10% fractional bandwidth).

Treatment of rabbit liver cancer in vivo using miniaturized image-ablate ultrasound arrays.

In the preclinical studies reported here, VX2 cancer within rabbit liver has been treated by bulk ultrasound ablation employing miniaturized image-ablate arrays. Array probes were constructed with 32 elements in a 2.3 × 20 mm(2) aperture, packaged within a 3.