In a recent study published in Science Advances, researchers developed a comfortable ultrasound breast patch (cUSBr-Patch) for breast screening.
Piezoelectric-based ultrasound transducer technology has drawn considerable attention due to its advantages over computed tomography. Breasts present a particular challenge in the context of large-area deep-tissue imaging, given the variability in geometry and deformability between and within individuals at different ages/times.
Automated breast and handheld ultrasonography are the current preferred methods; however, some technical gaps are yet to be overcome for ultrasound to be a reliable breast screening option.
In the present study, researchers developed a wearable cUSBr-Patch allowing for standardized and reproducible image acquisition throughout the breast. The objective was to design a wearable interface between the breast tissue and a one-dimensional (1D) phased array to enable consistent orientation and placement of the array along the breast.
The design comprised a soft, seamless fabric bra as an intermediary layer, a honeycomb patch as the outside layer providing support and guidance to the 1D array, and a tracker attached to the array for handling/rotating the array. Magnets were used to hold the tracker on patch openings and adhere the patch to the bra. Circular holes were made in the bra to ensure direct contact of the array with the skin.
The patch contained six openings where the tracker could be rotated. Further, the tracker can be moved through 15 hexagonal sections. Patch openings were patterned around the corresponding holes in the bra for array placement. The researchers focused on the ternary Pb(In1/2 Nb1/2)O3 -Pb(Mg1/3 Nb2/3)O3-PbTiO3 (PIN-PMN-PT) system to attain high phase transition temperatures and enhanced piezoelectric coefficients.
The rhombohedral-to-tetragonal phase transition (Tr-t) and curie (Tc) temperatures of PIN-PMT-PT crystals were 90°-110°C and 160°-180°C, respectively. Five samples (I to V) were diced from the Yb/Bi-co-doped PIN-PMN-PT crystals. X-ray diffraction revealed a pure perovskite structure and good structural consistency in samples. Remnant polarization increased from sample I to V due to the increase in possible polar directions.
The dielectric permittivity and piez”elec’ric coefficient of sample III were higher than undoped PIN-PMT-PT or PMN-PT crystals. X-ray diffraction revealed a consistent structural form of this sample from 0°C to 100°C. Besides, other parameters supported the viability of sample III, and consequently, it was selected for further analyses. A 1D phased array with 64 elements, a wavelength of 220 μm, and a frequency of 7 MHz was selected.
The element length was 8 mm, the width was 95 μm, and the kerf was 30 μm. The overall thickness of the device after bonding with the backing layer, matching layers, and anisotropic conductive film was less than 3 mm. The array was tested on two ultrasound phantoms to evaluate the acoustic performance and imaging capacity.
First, a planar phantom was used to demonstrate resolution and the field of view. The results revealed a maximum field of view of up to 100 mm width and an imaging depth of around 80 mm. The array separated targets with gaps of 0.25 mm and 1 mm in the axial and lateral directions for resolution targets at 30 mm depth.
Six images obtained with an oral phantom clearly and distinctly depicted large sphere, tube, bean-shaped, cylindrical, cubic, and square-pyramid objects at different locations and depths. The array could sustain a constant surface temperature under 50 volts for 10 minutes, given its thin structure and low working power. The thermal test and phantom data indicated that the array was suitable for tests on human tissue.
Finally, the team recruited a female with breast anomalies. They imaged breasts with the cUSBr-Patch and cross-validated with a commercial system. A 1 cm cyst, roughly of spherical shape, was detected in the left breast, which appeared as circumscribed and hypoechoic than surrounding tissues. Additionally, a smaller 0.3 cm cyst was detected in the right breast.
Using a commercial ultrasound system, a specialist probed the same region(s) and found a smaller cyst in the right breast and a larger cyst in the left breast. This indicated that the patch could detect these lesions with the same field of view as the commercial system.
Moreover, the array could detect the large cyst at the same position with a similar image quality after 30 minutes, highlighting the repeatability of array positioning.
Taken together, the researchers developed a novel ultrasound patch that allowed for non-invasive, real-time, and continuous monitoring of breasts.
The integration of the 1D array with the honeycomb patch and the superior performance of the Yb/Bi-doped PIN-PMN-PT crystal offered high-performance image acquisition with adequate contrast sensitivity, deep image depth, desired resolution, and a larger field of view.