Hyperthermia treatment requires two procedures. One procedure is to heat tissues up to a suitable therapeutic condition. The other way is to monitor the tissue temperature under treatment. Monitoing the temperature, especially in a noninvasive manner, is more difficult than the heating procedure. In this paper, some methods of noninvasive temperature measurements are introduced and their underlying difficulties are discussed. It is concluded that the most promising method is the temperature measurment method which uses temperature coefficient of sound propagation speed. In addition the maximum accuracy of this method was found to be around 0.2°C
Although ultrasonics diagnostic techniques have a great advantage of the nonivasive and realtime application for measuring the viscoelastic properties of the tissue, the accuracy of the brain image has been lower than that of MRI and XCT. The ultrasonic technique, therefore, have been used for only the intraoperative use and biopsy. The recent TCD, however, opened not only the transcranial blood flow measurement, but also the future of the transcranial color flow imaging (TC-CFI) in neurological and neurosurgical fields. Especially, the image of cerebral vasculature given by TC-CFI would have great value in the diagnoses of cerebral vascular diseases (CVD) . From the viewpoint of biomedical engineering, the future aspect of ultrasonic diagnostic application can be summarized by the following three items. (1) Ultrasonics frequency : It is very important to find a suitable ultrasonic frequency and the techniques for improving the ultrasonics refraction and the absorption at the skull It is essential to a maintain high sensitivity for low blood flow velocity. (2) TC-CFI : What cerebral vasculature can be imaged by the TC-CFI? That is, can we capture small branches of main arteries and veins near the Willis circle? The region of capturable vasculature has not yet been clarified by the TC-CFI technique. The improvement of Doppler signal sensitivity would develop the wide area in the brain, which would be an indispensable diagnostic technique. (3) Three dimensional (3D) image of cerebral circulation : TC-CFI has the possibility to reconstruct the 3-D image, which has a great advantage for the noninvasive diagnoses of various CVD such as the aneurysm in curved vessel structure.