Development of Bio-Impedance microprobes for Integration with a Smart Biopsy tool

Biopsy is a standard practice in the diagnosis and treatment of many cancers. Despite its integral role in cancer diagnosis, in some instances, the biopsy tool facilitates metastasis by transferring cancerous cells attached to its exterior into the healthy tissue or the blood circulation during its retraction from the tumor. These few cancer cells can then serve as seeds for the malignant tumor to grow in the healthy tissue. Cauterization using extreme heat or cold can destroy cells in the region and minimize the chance of seeding but this can be an inexact process that increases damage to otherwise healthy tissue and prolongs healing time following a biopsy procedure.

In our laboratory, we have developed the concept of a new smart biopsy tool that can reduce the chance of cancer cell dissemination during a biopsy. This tool improves on the conventional biopsy needle by introducing an impedance sensor on the biopsy tool which is housed in a sliding sheath. Due to the significant difference in the electrical conductivity of the tumor and the healthy tissue, the sensor is able to distinguish between the two and locate the exact tumor interface. The protective sheath placed around the instrumented biopsy tool and above the interface isolates the healthy tissue and prevents or at least minimizes the transfer of tumor cells. Delivering an RF dose through the sheath can kill any malignant cells that might be lurking around the interface.

This thesis, in particular, will concentrate on the development of the design, fabrication and calibration of the impedance sensor and its integration with the biopsy tool. The impedance sensor essentially consists of conductive electrodes sandwiched between insulating layers. They are built on thin-film polymer, Polyimide, using conventional microfabrication techniques. These sensors are further calibrated to estimate the cell constant. Once calibrated, these probes are used to measure the conductivity of porcine tissues, and in-house prepared agar phantoms.