Piezoelectric single crystal based one-dimensional phased array for breast tissue imaging

Abstract

Ultrasound is widely used in clinical practice because it is safe, non-invasive, non-ionizing, low-cost, and provides real-time imaging, monitoring, and therapy. However, conventional ultrasound probes are rigid, pressure-required, and operator-dependent. Replacing rigid transducers with conformable ultrasound transducer arrays can allow image acquisition on curved body parts, improve image quality, and enable functions such as long-term monitoring. In this thesis, I propose a conformable ultrasound breast patch (cUSBr-Patch) consisting of a one-dimensional (1D) phased array and a nature-inspired patch design, which offers large-area, deep tissue scanning and multi-angle, repeatable breast imaging while avoiding the drawbacks of conventional ultrasound imaging technologies. I used a Yb/Bi-doped PIN-PMN-PT single crystal as the active element due to its superior piezoelectric properties (d33 = 2,800 pC/N, εr = 7,000, k33 = 0.93). I then fabricated a 1D phased array transducer consisting of 64 elements with an operational frequency of 7.0 MHz. The 1D array exhibits promising acoustic performance with i) a maximum imaging depth of 80 mm, ii) contrast sensitivity of 3 dB, iii) axial/lateral resolutions of 0.25/1.0 mm at 30 mm depth, and iv) a larger field of view than the commercial handheld linear probe at depths of approximately 30 mm or deeper, indicating a potential reliable capability to detect early-stage breast tumors. Beyond this, comprehensive in vitro experimental studies establish that the cUSBr-Patch can provide accurate and reproducible imaging of different phantoms. The clinical trials reveal that the patch exhibits a sufficient contrast resolution (~3 dB) and axial/lateral resolutions of 0.25/1.0 mm at 30 mm depth, allowing the observation of small cysts (~ 0.3 cm) in the breast. This research develops a first-of-its-kind ultrasound technology for breast tissue scanning and imaging which offers a non-invasive method for tracking real-time dynamic changes of soft tissue.