Crossed-array transducer for real-time 3D imaging

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

Beers

et al. 2017

Abstract-Constructing a double-curved row-columnaddressed (RCA) 2-D array or applying a diverging lens over the flat RCA 2-D array can extend the imaging field-of-view (FOV) to a curvilinear volume without increasing the aperture size, which is necessary for applications such as abdominal and cardiac imaging. Extended FOV and low channel count of double-curved RCA 2-D arrays make 3-D imaging possible with equipment in the price range of conventional 2-D imaging. This study proposes a delay-and-sum beamformation scheme specific to double-curved RCA 2-D arrays and validates its focusing ability based on simulations. A synthetic aperture imaging sequence with single element transmissions is designed for imaging down to 14 cm at a volume rate of 88 Hz. Using a diverging lens with f-number of -1 circumscribing the underlying RCA array, the imaging quality of a double-curved λ/2-pitch 3 MHz 62+62 RCA 2-D array is investigated as a function of depth within a curvilinear FOV of 60°×60°. The simulated double-curved 2-D array exhibits the same full-width-at-halfmaximum values for a point scatterer within its curvilinear FOV at a fixed radial distance compared with a flat 2-D array within its rectilinear FOV. The results of this study demonstrate that the proposed beamforming approach is accurate for achieving correct time-of-flight calculations, and hence avoids geometrical distortions.

Section: B Curved Rca 2-d Arraysmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Curvilinear 3-D Imaging Using Row-Column-Addressed 2-D Arrays With a Diverging Lens: Feasibility Study

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

Beers

et al. 2017

“…This can be seen as using micro-beamforming with a fixed first stage. Another simpler approach to spread the acoustic energy is by using a double curved diverging acoustic lens on top of the RCA array [5]. A concave diverging lens can be designed with a material having a lower speed of sound compared to the human tissue, so that it has higher thickness around the corners and the sides of the array, and less thickness close to center of the array.…”

Section: Curved Rca 2-d Arraysmentioning

confidence: 99%

“…However, manufacturing curved transducer elements is challenging for both capacitive micromachined ultrasonic transducer (CMUT) and piezoelectric transducer (PZT) technologies. Another approach to spread the acoustic energy is by using a double curved diverging acoustic lens on top of the RCA array [5]. Using a lens makes it easier to fabricate curved transducers, as it is not needed to manufacture curved elements, and also making a lens is a well-tested technology.…”

Section: Introductionmentioning

confidence: 99%

3-D imaging using row-column-addressed 2-D arrays with a diverging lens

2016 IEEE International Ultrasonics Symposium (IUS)

Stuart

et al. 2016

Abstract-It has been shown that row-column-addressed (RCA) 2-D arrays can be an inexpensive alternative to fully addressed 2-D arrays. Generally imaging with an RCA 2-D array is limited to its forward-looking volume region. Constructing a double-curved RCA 2-D array or applying a diverging lens over the flat RCA 2-D array, can extend the imaging field-of-view (FOV) to a curvilinear volume without increasing the aperture size, which is necessary for applications such as abdominal and cardiac imaging. Extended FOV and low channel count of doublecurved RCA 2-D arrays make it possible to have 3-D imaging with equipment in the price range of conventional 2-D imaging. This study proposes a delay-and-sum (DAS) beamformation scheme specific to double-curved RCA 2-D arrays and validates its focusing ability based on simulations. A synthetic aperture imaging (SAI) sequence with single element transmissions at a time, is designed for imaging down to 14 cm at a volume rate of 88 Hz. The curvilinear imaging performance of a λ /2-pitch 3 MHz 62+62 RCA 2-D array is investigated as a function of depth, using a diverging lens with f-number of -1. The results of this study demonstrate that the proposed beamforming approach is accurate for achieving correct time-of-flight calculations, and hence avoids geometrical distortions.

“…However, manufacturing double curved transducer elements in two dimensions is challenging for both CMUT and piezoelectric transducer technologies. Another approach to spread the acoustic energy uses a double curved diverging acoustic lens on top of the RCA array [8], [9]. Using a lens makes it easier to fabricate curved arrays, as it is not needed to manufacture curved elements, and also making a lens is a well-tested technology.…”

Section: Introductionmentioning

confidence: 99%

3-D imaging using row-column addressed 2-D arrays with a diverging lens: Phantom study

2017 IEEE International Ultrasonics Symposium (IUS)

Beers

et al. 2017

Abstract-A double-curved diverging lens over a flat rowcolumn-addressed (RCA) 2-D array can extend its inherent rectilinear 3-D imaging field-of-view (FOV) to a curvilinear volume region, which is necessary for applications such as abdominal and cardiac imaging. A concave lens with radius of 12.7 mm was manufactured using RTV664 silicone. The diverging properties of the lens were evaluated based on measurements on several phantoms. The measured 6 dB FOV in contact with a material similar to human soft tissue was less than 15% different from the theoretical predictions, i.e., a curvilinear FOV of 32°×32°. A synthetic aperture imaging sequence with single element transmissions was designed for imaging down to 14 cm at a volume rate of 88 Hz. The performance was evaluated in terms of signal-to-noise ratio (SNR), FOV, and full-widthat-half-maximum (FWHM). The penetration depth in a tissue mimicking phantom with 0.5 dB/(cm MHz) attenuation was 13 cm. The results of this study confirm that the proposed lens approach is an effective method for increasing the FOV, when imaging with RCA 2-D arrays.