Imaging Performance for Two Row–Column Arrays

Abstract

This study evaluates the volumetric imaging performance of two prototyped 62+62 row-column-addressed (RCA) 2-D array transducer probes using three Synthetic Aperture Imaging (SAI) emission sequences and two different beamsformers. The probes are fabricated using capacitive micromachined ultrasonic transducer (CMUT), and piezoelectric transducer (PZT) technology. Both have integrated apodization to reduce ghost echoes and are designed with similar acoustical features i.e., 3 MHz center frequency, λ /2-pitch, and 24.8×24.8 mm 2 active footprint. Raw RF data are obtained using an experimental research ultrasound scanner, SARUS. The SAI sequences are designed for imaging down to 14 cm at a volume rate of 88 Hz. Two beamforming methods: Spatial matched filtering and rowcolumn adapted delay-and-sum are used for beamforming the RF data. The imaging quality is investigated through simulations and phantom measurements. Both probes on average have similar lateral full-width at half-maximum (FWHM) values, but the PZT probe has 20% smaller cystic resolution values and 70% larger contrast-to-noise ratio compared to the CMUT probe. The CMUT probe can penetrate down to 15 cm, and the PZT probe down to 30 cm. The CMUT probe has 17% smaller axial FWHM values. The matched filter focusing shows and improved B-mode image for measurements on a cyst phantom with an improved speckle pattern and better visualization of deeper lying cysts. The results of this study demonstrate the potentials of RCA 2-D arrays against fully addressed 2-D arrays, which are low channel count (e.g. 124 instead of 3,844), low acoustic intensity (MI ≤0.88 and I spta ≤5.5 mW/cm 2 ), and high penetration depth (down to 30 cm), which makes 3-D imaging at high volume rates possible with equipment in the price range of conventional 2-D imaging.

History and Latest Advances in Flow Estimation Technology: From 1-D in 2-D to 3-D in 4-D

“…This again can be used for increasing the center frequency of the probe and thereby resolution. Arrays with only 64+64 elements at 3 MHz have attained a decent volumetric image quality and a penetration down to 30 cm for SA imaging sequences [79].…”

3D Printed Calibration Micro-phantoms for Validation of Super-Resolution Ultrasound Imaging

“…In both experiments, the inter-volume stage movement was 12.5 µm, which emulates a 2 mm/s velocity at a 160 Hz volume rate. The imaging probe was a prototype 62 + 62 elements 3 MHz piezo-electric, row-column addressed (RCA) transducer [11]. The probe was connected to the experimental scanner SARUS [12], a system capable of storing all channel data to be processed offline.…”

3-D Super Resolution Imaging using a 62+62 Elements Row-Column Array

“…Transmissions were conducted using the rows, and data were received on all 62 columns. The virtual line sources emitted cylindrical waves [17] in a sequence with 32 positive emissions and 32 negative emission to make pulse inversion imaging possible. The transmit F-number was -1 using 32 Hanning apodized active elements, with the virtual source placed behind the array.…”

“…The beamformed volumes are processed in Matlab using our 3-D SR processing pipeline consisting of three steps. The first is to beamform the stored RF data from the SARUS scanner using the beamforming strategy described by Rasmussen et al [16,17] implemented in Matlab and running on an Nvidia GeForce GTX 1050 Ti (Nvidia, Santa Clara, CA, USA) GPU [19]. For the flow micro-phantom the second harmonic signal is employed, and a filter matched to the second harmonic is employed on all the received signals.…”