Biopsy-implantable chemical sensor

Abstract

There is a dire need for tools that can rapidly detect cancer treatment efficacy. A cancer patient must endure the side effects of chemotherapy and radiotherapy. It will be weeks before a change in the size of the tumor can be observed and the oncologist has the information necessary to determine whether treatment is working. Valuable time is lost searching for the right treatment and the right dose. This thesis presents a sensor that can be implanted inside the body during a biopsy procedure and wirelessly report on the tissue environment. The sensor has direct access and can track metabolic markers, such as pH and oxygen, which have been shown to predict outcome, dose, and response to cancer treatment. These markers cannot be measured anywhere else except directly inside the tissue, and this sensor provides that access. The probe allows for repeat, non-invasive measurement of the same location after the initial biopsy. The sensor consists of a small nuclear magnetic resonance (NMR) probe that has a cavity filled with a contrast agent sensitive to the chemical of interest. An NMR relaxation measurement of the contrast agent reveals the chemical concentration. Wireless NMR measurements are performed with the aid of a reader probe that resides outside of the body. The reader generates the excitation pulses and receives the NMR signal. The sensor and reader have a mutual inductance that enables the wireless measurement. The resonant coupling allows wireless NMR measurements with enhanced signal-to-noise ratio. The field inside the sensor is amplified compared to the surrounding tissue. The amplification localizes the measurement to the sensor and eliminates any signal from the surrounding tissue. The coupled reader-sensor performs standard NMR relaxation measurements. A method is presented to produce the sensors in large numbers, and the sensors are tested in vivo. The probe is designed to be implanted during a routine procedure and would be no more invasive than existing clinical practice. The measurements can track tumor progression and guide therapy before any physical changes can be observed, and the patient can receive the right treatment as soon as possible.