This paper presents a power-and area-efficient front-end ASIC that is directly integrated with an array of 32 × 32 piezoelectric transducer elements to enable next-generation miniature ultrasound probes for real-time 3-D transesophageal echocardiography. The 6.1 × 6.1 mm 2 ASIC, implemented in a low-voltage 0.18 m CMOS process, effectively reduces the number of cables required in the probe's narrow shaft by means of 96 delay-and-sum beamformers, each of which locally combines the signals received by a sub-array of 3 × 3 elements. These beamformers are based on pipeline-operated analog sample-and-hold stages, and employ a mismatch-scrambling technique to prevent the ripple signal associated with mismatch between these stages from limiting the dynamic range. In addition, an ultra-low-power LNA architecture is proposed to increase the power-efficiency of the receive circuitry. The ASIC has a compact, element-matched layout, and consumes less than 230 mW while receiving. Its functionality has been successfully demonstrated in 3-D imaging experiments.

This paper presents the design, fabrication, and experimental evaluation of a prototype lead zirconium titanate (PZT) matrix transducer with an integrated receive ASIC, as a proof of concept for a miniature three-dimensional (3-D) transesophageal echocardiography (TEE) probe. It consists of an array of 9 ×12 piezoelectric elements mounted on the ASIC via an integration scheme that involves direct electrical connections between a bond-pad array on the ASIC and the transducer elements. The ASIC addresses the critical challenge of reducing cable count, and includes front-end amplifiers with adjustable gains and micro-beamformer circuits that locally process and combine echo signals received by the elements of each 3 ×3 subarray. Thus, an order-of-magnitude reduction in the number of receive channels is achieved. Dedicated circuit techniques are employed to meet the strict space and power constraints of TEE probes. The ASIC has been fabricated in a standard 0.18-μm CMOS process and consumes only 0.44 mW/channel. The prototype has been acoustically characterized in a water tank. The ASIC allows the array to be presteered across ±37° while achieving an overall dynamic range of 77 dB. Both the measured characteristics of the individual transducer elements and the performance of the ASIC are in good agreement with expectations, demonstrating the effectiveness of the proposed techniques.

For several years, the standard in ultrasound imaging has been second-harmonic imaging. A new imaging technique dubbed "super-harmonic imaging" (SHI) was recently proposed. It takes advantage of the higher - third to fifth - harmonics arising from nonlinear propagation or ultrasound-contrast-agent (UCA) response. Next to its better suppression of near-field artifacts, tissue SHI is expected to improve axial and lateral resolutions resulting in clearer images than second-harmonic imaging. When SHI is used in combination with UCAs, a better contrast-to-tissue ratio can be obtained. The use of SHI implies a large dynamic range and requires a sufficiently sensitive array over a frequency range from the transmission frequency up to its fifth harmonic (bandwidth > 130%). In this paper, we present the characteristics and performance of a new interleaved dual frequency array built chiefly for SHI. We report the rationale behind the design choice, frequencies, aperture, and piezomaterials used. The array is efficient both in transmission and reception with well-behaved transfer functions and a combined -6-dB bandwidth of 144%. In addition, there is virtually no contamination of the harmonic components by spurious transducer transmission, due to low element-to-element crosstalk (< 30 dB) and a low transmission efficiency of the odd harmonics (< 46 dB). The interleaved array presented in this article possesses ideal characteristics for SHI and is suitable for other methods like second-harmonic, subharmonic, and second-order ultrasound field (SURF) imaging.

15Purpose: Photoacoustic imaging has proven to be able to detect vascularization-driven optical absorption contrast associated with tumors. In order to detect breast tumors located a few centimeter deep in tissue, a sensitive ultrasound detector is of crucial importance for photoacoustic mammography. Further, because the expected photoacoustic frequency bandwidth (a few MHz to tens of kHz) is inversely proportional to the dimensions of light absorbing structures (0.5 to 10+ 20 mm), proper choices of materials and their geometries and proper considerations in design have to be made to implement optimal photoacoustic detectors. In this study, we design and evaluate a specialized ultrasound detector for photoacoustic mammography.Methods: Based on the required detector sensitivity and its frequency response, a selection of active material and matching layers and their geometries is made leading to a functional detector

This paper presents a power-and area-efficient front-end ASIC that is directly integrated with an array of 32 × 32 piezoelectric transducer elements to enable next-generation miniature ultrasound probes for real-time 3-D transesophageal echocardiography. The 6.1 × 6.1 mm 2 ASIC, implemented in a low-voltage 0.18 m CMOS process, effectively reduces the number of cables required in the probe's narrow shaft by means of 96 delay-and-sum beamformers, each of which locally combines the signals received by a sub-array of 3 × 3 elements. These beamformers are based on pipeline-operated analog sample-and-hold stages, and employ a mismatch-scrambling technique to prevent the ripple signal associated with mismatch between these stages from limiting the dynamic range. In addition, an ultra-low-power LNA architecture is proposed to increase the power-efficiency of the receive circuitry. The ASIC has a compact, element-matched layout, and consumes less than 230 mW while receiving. Its functionality has been successfully demonstrated in 3-D imaging experiments.