Scott Cogan

Reconfigurable arrays for portable ultrasound

A collaborative effort is aimed at the development of reconfigurable array technology. The goal is to enable innovative medical ultrasound imagers ideally suited for portable ultrasound and applications such as remote emergency medicine and combat casualty care. Success depends on developing several technologies, the first of which is capacitive micromachined ultrasound transducers (cMUTs). The monolithic nature of cMUTs facilitates close connection with microelectronics. Thus a second technology under development is a switch matrix application specific integrated circuit (ASIC) that will enable the changing of interconnect between cMUT cells. The reconfigurable array concept arises from this ability to dynamically combine cMUT cells to form ideal apertures for a given imaging target (e.g. annular and phased apertures of various ring widths) and to move these apertures across the reconfigurable array plane [1-4]. Two central hypotheses are being tested: (1) the reconfigurable array can acquire acoustic pulse-echo data in a manner equivalent or superior to today’s 1D piezoceramic arrays (2) reconfigurable array technology will enable highly portable ultrasound platforms. Keywords-reconfigurable; annular; array; cMUT; ASIC; switch matrix; dynamic; phased; real-time

5F-2 Packaging and Design of Reconfigurable Arrays for Volumetric Imaging

Recent advances in capacitive micromachined ultrasound transducers (cMUTs), piezoceramic acoustic stack design, and transducer-to-electronics integration are enabling the fabrication of highly integrated reconfigurable ultrasound arrays. Reconfigurability in this context refers to the ability to reorganize the array elements in any configuration deemed desirable. Attractive configurations are an annular array, which can be translated electronically along a 2D array surface, or a phased array whose element orientation and pitch can be varied to optimize an image [1-6]. Further, annular array configurations make possible 3D-stacked miniaturized systems by reducing channel count, system size, and power consumption. In addition to such benefits, the annular array also provides dynamic axisymmetric focusing for excellent image quality. Several methods of integration have been explored to realize stacked transducer arrays with low channel count. Key components of the design include advanced interconnect such as through silicon vias in cMUTs and z-axis backing stacks, switch matrix application specific integrated circuits (ASICs), and high density multi-layer flex.

4-D ICE: A 2-D Array Transducer With Integrated ASIC in a 10-Fr Catheter for Real-Time 3-D Intracardiac Echocardiography

We developed a 2.5×6.6 mm2 2-D array transducer with integrated transmit/receive application-specific integrated circuit (ASIC) for real-time 3-D intracardiac echocardiography (4-D ICE) applications. The ASIC and transducer design were optimized so that the high-voltage transmit, low-voltage time-gain control and preamp, subaperture beamformer, and digital control circuits for each transducer element all fit within the 0.019-mm2 area of the element. The transducer assembly was deployed in a 10-Fr (3.3-mm diameter) catheter, integrated with a GE Vivid E9 ultrasound imaging system, and evaluated in three preclinical studies. The 2-D image quality and imaging modes were comparable to commercial 2-D ICE catheters. The 4-D field of view was at least 90° × 60° × 8 cm and could be imaged at 30 vol/s, sufficient to visualize cardiac anatomy and other diagnostic and therapy catheters. 4-D ICE should significantly reduce X-ray fluoroscopy use and dose during electrophysiology ablation procedures. 4-D ICE may be able to replace transesophageal echocardiography (TEE), and the associated risks and costs of general anesthesia, for guidance of some structural heart procedures.We developed a 2.5 x 6.6 mm 2D array transducer with integrated transmit/receive ASIC for 4D ICE (real-time 3D IntraCardiac Echocardiography) applications. The ASIC and transducer design were optimized so that the high voltage transmit, low-voltage TGC (time-gain control) and preamp, subaperture beamformer, and digital control circuits for each transducer element all fit within the 0.019 mm2 area of the element. The transducer assembly was deployed in a 10 Fr (3.3 mm diameter) catheter, integrated with a GE Vivid1 E9 ultrasound imaging system, and evaluated in three pre-clinical studies. 2D image quality and imaging modes were comparable to commercial 2D ICE catheters. The 4D field of view was at least 90° x 60° x 8 cm and could be imaged at 30 volumes/sec, sufficient to visualize cardiac anatomy and other diagnostic and therapy catheters. 4D ICE should significantly reduce X-ray fluoroscopy use and dose during electrophysiology (EP) ablation procedures. 4D ICE may be able to replace trans-esophageal echocardiography (TEE), and the associated risks and costs of general anesthesia, for guidance of some structural heart procedures.

2B-1 Solutions for Reconfigurable Arrays in Ultrasound

A reconfigurable array may involve a relatively large 2D array of transducer sub-elements and a layer of electronics which uses switches to connect certain sub-elements together, to a single system channel [Fischer et al., 2005 and Thomenius et al., 2005]. An annular array pattern, consisting of ring-shaped element groups, may be electronically scanned, or stepped, across the surface of such a reconfigurable array. The array could use 20 to 32 system channels and provide image quality comparable to a 128 channel linear array [Hazard et al., 2003 amd Dietz et al., 1979], This paper discusses some of the unique challenges and solutions pertaining to reconfigurable two-dimensional ultrasound arrays. Size constraints of the electronics result in some non-ideal aspects to the switch array; namely, there are constraints on the distribution of system channel access points across the array, and that these switches have a certain on-resistance which introduces non-ideal signal propagation delays. Some solutions will be discussed in this paper which aim to reduce the effect of these non-ideal constraints, and may suggest certain design tradeoffs which can be made in the design of future reconfigurable switch arrays

Reconfigurable mosaic annular arrays

Mosaic annular arrays (MAA) based on reconfigurable array (RA) transducer electronics assemblies are presented as a potential solution for future highly integrated ultrasonic transducer subsystems. Advantages of MAAs include excellent beam quality and depth of field resulting from superior elevational focus compared with 1-D electronically scanned arrays, as well as potentially reduced cost, size, and power consumption resulting from the use of a limited number of beamforming channels for processing a large number of subelements. Specific design tradeoffs for these highly integrated arrays are discussed in terms of array specifications for center frequency, element pitch, and electronic switch-on resistance. Large-area RAs essentially function as RC delay lines. Efficient architectures which take into account RC delay effects are presented. Architectures for integration of the transducer and electronics layers of large-area array implementations are reviewed.