A Review of Imaging Methods to Assess Ultrasound-Mediated Ablation

Ultrasound ablation techniques are minimally invasive alternatives to surgical resection and have rapidly increased in use.The response of tissue to HIFU ablation differs based on the relative contributions of thermal and mechanical effects,which can be varied to achieve optimal ablation parameters for a given tissue type and location.In tumor ablation,similar to surgical resection,it is desirable to include a safety margin of ablated tissue around the entirety of the tumor.A factor in optimizing ablative techniques is minimizing the recurrence rate,which can be due to incomplete ablation of the target tissue.Further,combining focal ablation with immunotherapy is likely to be key for effective treatment of metastatic cancer,and therefore characterizing the impact of ablation on the tumor microenvironment will be important.Thus,visualization and quantification of the extent of ablation is an integral component of ablative procedures.The aim of this review article is to describe the radiological findings after ultrasound ablation across multiple imaging modalities.This review presents readers with a general overview of the current and emerging imaging methods to assess the efficacy of ultrasound ablative treatments.

Highly Integrated Multiplexing and Buffering Electronics for Large Aperture Ultrasonic Arrays

Large aperture ultrasonic arrays can be implemented by tiling together multiple pretested modules of high-density acoustic arrays with closely integrated multiplexing and buffering electronics to form a larger aperture with high yield.These modular arrays can be used to implement large 1.75D array apertures capable of focusing in elevation for uniform slice thickness along the axial direction which can improve image contrast.An important goal for large array tiling is obtaining high yield and sensitivity while reducing extraneous image artifacts.We have been developing tileable acoustic-electric modules for the implementation of large array apertures utilizing Application Specific Integrated Circuits(ASICs)implemented using 0.35μm high voltage(50 V)CMOS.Multiple generations of ASICs have been designed and tested.The ASICs were integrated with high-density transducer arrays for acoustic testing and imaging.The modules were further interfaced to a Verasonics Vantage imaging system and were used to image industry standard ultrasound phantoms.The first-generation modules comprise ASICs with both multiplexing and buffering electronics on-chip and have demonstrated a switching artifact which was visible in the images.A second-generation ASIC design incorporates low switching injection circuits which effectively mitigate the artifacts observed with the first-generation devices.Here,we present the architecture of the two ASIC designs and module types as well imaging results that demonstrate reduction in switching artifacts for the second-generation devices.

Erratum to “Highly Integrated Multiplexing and Buffering Electronics for Large Aperture Ultrasonic Arrays”

In the article titled“Highly Integrated Multiplexing and Buffering Electronics for Large Aperture Ultrasonic Arrays”[1],there was an error in figure 7.The figure should show as per the submitted files.