A Miniaturized Multidirectional Stacking Ultrasound Transducer for Endo-Bronchoscopy Lung Nodule Ablation

Lung cancer is the leading cause of cancer death worldwide with estimated over 230,000 being diagnosed in USA annually. Due to the poor 5-year survival rate (18.6%) for lung cancer, it is vital for the early-stage lung cancer diagnosis and therapy with curative intervention, which can dramatically reduce the mortality. Ultrasound ablation has been reported as a promising technique taking the advantages of acoustic impedance differences between the nodule tissue and normal lung tissue and the ability to focus acoustic energy with ultrasound array for focused high power and precise focal zone control. Yet, endoscopic ultrasound transducers still face the challenge of insufficient power output due to dimension constraints. Thus, in this work, we developed a miniaturized, multidirectional ultrasound transducer with an overall dimension of 2.2 × 2.2 × 6.0 mm³ for fitting in modern bronchoscopy procedures to target peripheral pulmonary lesions. Meanwhile, with a two-layer stack design, the multi-directional transducer was more efficient in generating high power with a small form factor design that is capable of inducing temperature rise to over 65 °C in 3 min for tissue ablations. For the in-vitro test, a temperature sensitive color-changing material has been demonstrated for mimicking the nodule with surrounding inflated bovine lung tissues. The ablated lesion size was first estimated with a thermal camera and then demonstrated with the color variation area. With a lesion size of 7.3 × 4.2 × 3.1 mm³ in vitro at a depth of 4 mm, the potential of the device for lung nodule treatment was validated.