PARENT SESSION
1:30 PM to 3:30 PM
Saturday, April 20, 2002
Poster Session 1 Noninvasive Treatment Monitoring and Treatment Planning
Room: Nevada 1-2

(MP01-7) A novel ultrasonic method for non-invasive temperature monitoring during microwave thermotherapy.

Novak, Petr^*,1,3, Pousek, Lubomir¹, Schreib, Petr¹, Vrba, Jan¹, Zuna, Ivan², ¹ Centre for Biomedical Engineering, Prague, Czech Republic³ Department of Radiation Oncology, Mallinckrodt Institute of Radiology, St. Louis, MO² German Cancer Research Center in Heidelberg, Heidelberg, Germany

ABSTRACT-
At present invasive thermometer probes are clinically used for a temperature measuring during the microwave thermotherapy (MT). The use of invasive thermometric methods entails problems concerning a low spatial resolution and a patient's burden. In this paper a development of a novel method of the noninvasive temperature monitoring is described. The method is based on an ultrasonic B-mode image processing. Over 100 in-vivo microwave thermotherapy experiments with prostate tumors were performed. The temperature range was 37-44°C for all of the experiments. During the MT treatment series of ultrasound B-mode images were obtained. Texture parameters were evaluated from the ultrasound images. These parameters were correlated with the invasively measured temperature during the MT session. The mean grey scale level was the most correlated parameter r = 0.96±0.05. Consequently a theoretical temperature model for texture parameter interpretation was proposed. A presented system is based on the temperature model and provides an automatic acquisition of B-mode images from standard medical ultrasound machine, image processing and interpretation, and visualization of estimated two-dimensional temperature map of the scanned tissue area. The system was tested in-vivo and confronted with an invasive measurement. The outcomes of both methods are in a good agreement, with respect to a low spatial resolution of the invasive measurement. The noninvasive system provides temperature maps in the real time (spatial resolution 2 mm and temperature resolution 1°C). The developed method for noninvasive temperature estimation during microwave thermotherapy was extended to a three-dimensional (3D) volume monitoring method and implemented into the presented system. A 3D monitoring system is able to estimate the temperature changes during therapy in the whole volume of the heated tissue. The 3D temperature maps show a significant link to the normalized SAR distribution of a microwave applicator.

KEYWORDS: temperature monitoring, noninvasive, hyperthermia