Design of an automated temperature mapping system for ultrasound or microwave hyperthermia

An automated temperature mapping system was designed to accomplish the following goals: remote control mapping; a maximum position error of 0.5 mm; mapping simultaneously on several channels; real-time screen display on a dedicated computer; to be inexpensive; and have a simple patient interface and set up. A four channel, microstepper system was fabricated for less than $1000 and controlled by an IBM-AT computer. The system utilizes direct drive of Luxtron fibre-optic probes fed through thin flexible Teflon^® tubing which allows for patient movement. The driving and control software were written in the programming language "C". Mapping parameters for each independent channel include start and stop positions and map increment. The software permits the user to automatically find the maximum temperature along a track in three passes of 2.0, 1.0 and 0.5 mm steps. The latter two passes take five or seven readings centred about the maximum of the previous pass. A high resolution monitor plots the temperatures in real time, overlaying the previous map in a new colour. A screen dump was written to drive a colour printer with the plot information. The computer evaluates each plot to safeguard against any shift in the maximum location. Visualization of orthogonal pullbacks provides rapid feedback and aids in the repositioning of superficial hyperthermia transducers. The time saved over the previous manual mapping methods easily justifies the additional set up time.