High-Resolution Ultrasonic System for Measuring Temperature in Soft Tissue-Mimicking Phantoms Using a FPGA Platform

Abstract

This article describes the design and development of a high-resolution ultrasonic system for measuring temperature in soft tissue-mimicking phantoms using a FPGA module. The system uses a DE0-Nano FPGA development platform, a 2x16 LCD display, an optical encoder, two PVDF ultrasonic transducers, and an External Circuit module. In the experimental implementation, a distance was set between the transducers and an operating temperature range of 35 ºC to 40 ºC with a resolution of 0.1 ºC was selected, considering the initial value of the range as the reference temperature. The difference between flight times with respect to the initial temperature flight time, produces a narrow pulse that is converted into a DC voltage, This DC voltage is proportional to the change in temperature. The system is based on a reconfigurable architecture; this allows the transmission burst and the reception control pulses to be programmable, allowing its adjustment for different operation ranges. The experimentation was carried out in an experimental tank filled with distilled and degassed water with a controlled temperature, one piece of soft tissue-mimicking phantom (2.5x2.5x3.0 cm) and a support structure to assemble the PVDF transducers separated 3.0 cm from each other. The system acquires 100 samples per second, calculates the average temperature with a polynomial fit curve and displays the result with a refresh rate of one second. Due to its design characteristics it is feasible to extend its application to measure temperature in biological soft tissue.