Piezoelectric-based ultrasound transducer technology has emerged as a promising alternative to computed tomography, garnering significant attention for its advantages in various medical imaging applications. In particular, breasts present a unique challenge in large-area deep-tissue imaging due to their variable geometry and deformability between individuals and at different stages of development.
The current preferred methods for breast imaging include automated breast and handheld ultrasonography. However, there are still some technical gaps that need to be addressed to make ultrasound a reliable breast screening option. To address these challenges, a group of researchers embarked on a study to develop a wearable Continuous Ultrasonic Breast (cUSBr) patch that could facilitate standardized and reproducible image acquisition throughout the breast. The study published in Science Advances.
The primary objective of the cUSBr-Patch was to create a wearable interface between the breast tissue and a one-dimensional (1D) phased array to ensure consistent orientation and placement of the array along the breast. The design of the cUSBr-Patch consisted of several components, including a soft and seamless fabric bra serving as an intermediary layer, a honeycomb patch providing support and guidance to the 1D array, and a tracker attached to the array for handling and rotating it.
The patch was held in place by magnets, which adhered to the bra, and circular holes were created in the bra to enable direct contact of the array with the skin. The patch featured six openings, allowing the tracker to be rotated and moved through 15 hexagonal sections. The positioning of the openings in the patch corresponded to the holes in the bra, ensuring accurate placement of the array.
The 1D array had an element length of 8 mm, a width of 95 μm, and a kerf of 30 μm. The overall thickness of the device, including bonding with the backing layer, matching layers, and anisotropic conductive film, was less than 3 mm.
To evaluate the performance of the cUSBr-Patch, the researchers conducted tests on two ultrasound phantoms. The first test involved a planar phantom to assess resolution and field of view. The results demonstrated a maximum field of view of up to 100 mm width and an imaging depth of approximately 80 mm. The array successfully distinguished targets with gaps of 0.25 mm and 1 mm in the axial and lateral directions at a depth of 30 mm.
The second test involved an oral phantom, where the array produced clear and distinct images of various objects, such as large spheres, tubes, bean-shaped structures, cylinders, cubes, and square pyramids, located at different depths. The array’s thin structure and low working power allowed it to maintain a constant surface temperature under 50 volts for 10 minutes, making it suitable for tests on human tissue.
To further assess the capabilities of the cUSBr-Patch, the researchers recruited a female subject with breast anomalies. The breasts were imaged using the patch and the results were cross validated with a commercial ultrasound system. The cUSBr-Patch successfully detected a 1 cm cyst in the left breast, appearing as circumscribed and hypoechoic compared to the surrounding tissues. Additionally, a smaller 0.3 cm cyst was detected in the right breast.
A specialist using the commercial ultrasound system probed the same regions and confirmed the presence of the cysts. This indicated that the cUSBr-Patch could detect the lesions with the same field of view as the commercial system. Moreover, the array could detect the large cyst at the same position with similar image quality even after 30 minutes, highlighting the repeatability of array positioning. Overall, the researchers successfully developed a novel ultrasound patch, the cUSBr-Patch, which offered non-invasive, real-time, and continuous monitoring of breasts.
The integration of the 1D array with the honeycomb patch, coupled with the superior performance of the Yb/Bi-doped PIN-PMN-PT crystal, allowed for high-performance image acquisition with adequate contrast sensitivity, deep image depth, desired resolution, and a larger field of view. This breakthrough has the potential to revolutionize breast imaging, making it a promising tool for breast cancer screening and diagnosis.