A Row-Column-Addressed 2D Probe with an Integrated Compound Diverging Lens

Engholm, Mathias; Havreland, Andreas Spandet; Thomsen, Erik Vilain; Beers, Christopher; Tomov, Borislav Gueorguiev; Jensen, Jørgen Arendt

doi:10.1109/ultsym.2018.8579955

Cited by 6 publications

(4 citation statements)

References 14 publications

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“…It should also be noted that T l depends exponentially on the frequency. This parameter influences the shape of the frequency impulse response and causes a down-shift of the center frequency and a reduction in the bandwidth [16], [21]. The attenuation coefficient is also of the foremost importance for a high-frequency transducer as the signal can be completely damped at these frequencies.…”

Section: Designmentioning

confidence: 99%

Diverging Polymer Acoustic Lens Design for High-Resolution Row–Column Array Ultrasound Transducers

Audoin,

Salari,

Tomov

et al. 2024

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Spherical diverging acoustic lenses mounted on flat 2D Row-Column Addressed (RCA) ultrasound transducers have shown the potential to extend the Field of View (FOV) from a rectilinear to a curvilinear volume region and thereby enable 3D imaging of large organs. Such lenses are usually designed for small aperture low-frequency transducers, which have limited resolution. Moreover, they are made of off-the-shelf pieces of materials, which leaves no room for optimization. We hypothesize that acoustic lenses can be designed to fit highresolution transducers and they can be fabricated in a fast, cost-effective, and flexible manner using a combination of 3D printing and casting or CNC machining techniques. These lenses should increase the FOV of the array while preserving the image quality. In this work, such lenses are made in concave, convex, and compound spherical shapes, and from thermoplastics and thermosetting polymers. Polymethylpentene (TPX), Polystyrene (PS), Polypropylene (PP), Polymethyl methacrylate (PMMA), Polydimethylsiloxane (PDMS) and Room-temperaturevulcanizing silicone (RTV) diverging lenses have been fabricated and mounted on a 128+128 6 MHz RCA transducer. The performances of the lenses have been assessed and compared in terms of FOV, Signal to Noise Ratio (SNR), bandwidth, and potential artefacts. The largest FOV (24.0 • ) is obtained with a 42.64 mm radius PMMA-RTV compound lens, which maintains a decent fractional bandwidth (53%) and SNR at 6 MHz (-9.1 dB amplitude drop compared to the unlensed transducer). The simple PMMA TPX, PS, PP, PDMS and RTV lenses provide a FOV of 12.2 • , 6.3 • , 8.1 • , 11.7 • , 0.6 • and 10.4 • , a fractional bandwidth of 97%, 46%, 103%, 46%, 97%, 53% and 49%, and an amplitude drop of -5.2 dB, -4.4 dB, -2.8 dB, -15.4 dB, -6.0 dB and -1.8 dB respectively. This work demonstrates that thermoplastics are suitable materials for fabricating lowattenuation convex diverging lenses for large-aperture, highfrequency 2D transducers. This is highly desired to achieve highresolution volumetric imaging of large organs.

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Section: Designmentioning

confidence: 99%

Diverging Polymer Acoustic Lens Design for High-Resolution Row–Column Array Ultrasound Transducers

Audoin,

Salari,

Tomov

et al. 2024

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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“…Our group in Denmark has worked extensively with RC arrays for the last ten years within anatomic and functional imaging primarily based on synthetic aperture (SA) sequences. We have also fabricated a range of RC probes including PZT and CMUT based devices [41] and developed fabrication schemes for diverging lenses and probes with integrated lenses [42,43]. The various results and possibilities will be presented below.…”

Section: A History Of Row-column Imagingmentioning

confidence: 99%

Anatomic and Functional Imaging Using Row–Column Arrays

Jensen

Schou

Jorgensen

et al. 2022

IEEE Trans. Ultrason., Ferroelect., Freq. Contr.

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Row-column (RC) arrays have the potential to yield full three-dimensional ultrasound imaging with a greatly reduced number of elements compared to fully populated arrays. They, however, have several challenges due to their special geometry. This review paper summarizes the current literature for RC imaging and demonstrate that full anatomic and functional imaging can attain a high quality using synthetic aperture (SA) sequences and modified delay-and-sum beamforming. Resolution can approach the diffraction limit with an isotropic resolution of half a wavelength with low side-lobe levels, and the field-ofview can be expanded by using convex or lensed RC probes. GPU beamforming allows for 3 orthogonal planes to be beamformed at 30 Hz, providing near real time imaging ideal for positioning the probe and improving the operator's workflow. Functional imaging is also attainable using transverse oscillation and dedicated SA sequence for tensor velocity imaging for revealing the full 3-D velocity vector as a function of spatial position and time for both blood velocity and tissue motion estimation. Using RC arrays with commercial contrast agents can reveal super resolution imaging with isotropic resolution below 20 µm. RC arrays can, thus, yield full 3-D imaging at high resolution, contrast, and volumetric rates for both anatomic and functional imaging with the same number of receive channels as current commercial 1-D arrays.

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“…The first 2D array using CMUTs based on the row-column addressing scheme had 32+32 elements fabricated using wafer fusion bonding, where the cavities and membranes were both made with silicon nitride. Since then several row-column CMUTs have been designed and fabricated with a variety of different methods, such as sacrificial release [37], [38] using a TOBE array architecture, adhesive wafer bonding [39], [40], fusion bonding [16], [41]- [44] and anodic bonding [45]- [47]. Some of these arrays have been integrated in hand-held probes, presented in [16] as a 62+62 RCA 2D CMUT probe together with a corresponding PZT probe for comparison, and in [44] where two 92+92 RCA 2D CMUT probes with and without integrated diverging lenses are presented.…”

Section: B Capacitive Micromachined Ultrasonic Transducersmentioning

confidence: 99%

“…Since then several row-column CMUTs have been designed and fabricated with a variety of different methods, such as sacrificial release [37], [38] using a TOBE array architecture, adhesive wafer bonding [39], [40], fusion bonding [16], [41]- [44] and anodic bonding [45]- [47]. Some of these arrays have been integrated in hand-held probes, presented in [16] as a 62+62 RCA 2D CMUT probe together with a corresponding PZT probe for comparison, and in [44] where two 92+92 RCA 2D CMUT probes with and without integrated diverging lenses are presented. These probes showed the potential for using CMUTs for RCA arrays and demonstrated that such probes can attain similar performances as a PZT probe made using the same dimensions.…”

Section: B Capacitive Micromachined Ultrasonic Transducersmentioning

confidence: 99%

A Hand-Held 190+190 Row–Column Addressed CMUT Probe for Volumetric Imaging

Grass

Engholm

Havreland

et al. 2022

IEEE Open J. Ultrason., Ferroelect., Freq. Contr.

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This paper presents the design, fabrication, and characterization of a 190+190 row-column addressed (RCA) capacitive micromachined ultrasonic transducer (CMUT) array integrated in a custom hand-held probe handle. The array has a designed 4.5 MHz center frequency in immersion and a pitch of 95 µm which corresponds to ≈ λ/4. The array has a 2.14 × 2.14 cm 2 footprint including an integrated apodization scheme to reduce ghost echoes when performing ultrasound imaging. The array was fabricated using a combination of fusion and anodic bonding, and a deposit, remove, etch, multistep (DREM) etch to reduce substrate coupling and improve electrode conductivity. The transducer array was wire-bonded to a rigid-flex printed circuit board (PCB), encapsulated in room temperature vulcanizing (RTV) silicone polymer, electromagnetic interference (EMI) shielded, and mounted in a 3D-milled PPSU probe handle. The probe was characterized using the SARUS experimental scanner and 3D volumetric imaging was demonstrated on scatter and wire phantoms. The imaging depth was derived from tissue mimicking phantom measurements (0.5 dB MHz −1 cm −1 attenuation) by estimating the SNR at varying depths. For a synthetic aperture imaging sequence with 96+96 emissions the imaging depth was 3.6 cm. The center frequency measured from the impulse response spectra in transmit and pulse-echo was 6.0 ± 0.9 MHz and 5.3 ± 0.4 MHz, and the corresponding relative bandwidths were 62.8 ± 4.5 % and 86.2 ± 10.4 %. The fabrication process showed clear improvement in relative receive sensitivity and transmit pressure uniformity compared to earlier silicon-on-insulator (SOI) based designs. However, at the same time it presented yield problems resulting in only around 55 % elements with a good response.

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A Row-Column-Addressed 2D Probe with an Integrated Compound Diverging Lens

Cited by 6 publications

References 14 publications

Diverging Polymer Acoustic Lens Design for High-Resolution Row–Column Array Ultrasound Transducers

Diverging Polymer Acoustic Lens Design for High-Resolution Row–Column Array Ultrasound Transducers

Anatomic and Functional Imaging Using Row–Column Arrays

A Hand-Held 190+190 Row–Column Addressed CMUT Probe for Volumetric Imaging

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