A Bulk PZT Microsensor for In-Situ Tissue Contrast Detection During Fine Needle Aspiration Biopsy of Thyroid Nodules

This paper describes a piezoelectric sensor integrated into a cavity at the tip of a biopsy needle intended for fine needle aspiration (FNA) of thyroid nodules. Located on a steel diaphragm of 300 µ m radius and 23 µ m average thickness, it is intended to aid in tissue differentiation, providing information that is complementary to any imaging method that may be used concurrently. The sensor is fabricated from bulk lead zirconate titanate (PZT) using a customized process. Micro electro-discharge machining is used to form a steel tool that is subsequently used for batch-mode ultrasonic machining of bulk PZT ceramic. The resulting sensor is 50 µ m thick and 200 µ m in diameter. Devices were tested in materials that mimic the texture of human tissue in the training of physicians, and were separately tested with porcine fat and muscle tissue. The magnitude and frequency of a resonant peak shows tissue-specific characteristics as the needle is inserted into tissue. For example, in the porcine tissue sample, the magnitude and peak frequency respectively change from ≈2118 Ω and ≈163 MHz to ≈562 Ω and ≈150 MHz as the needle moves from fat to muscle tissue.