Estimations of the precision of temperature reconstruction in passive thermoacoustic tomography

Possible characteristics of a passive thermoacoustic tomograph designed for the reconstruction of a two-dimensional distribution of the internal tempe rature of an object from its own thermal acoustic radiation in the megahert z frequency range are estimated by numerical simulation. Two types of Tikho nov's method of regularization, i.e., the global and the local types, are u sed to solve the inverse problem. The local type takes into account the phy sical features of the internal temperature distribution in a human body. It is demonstrated that, if the rms error of a single measurement is equal to 0.1 K, the average total rms error of the temperature reconstruction is [d T(R)] approximate to 0.3 K. The utilization of a local regularization provi des an opportunity to reduce [dT(R)] by 10-15% in many cases. The value of [dT(R)] weakly depends on the error of a single measurement, and its major part (approximate to 90%) is determined not by the precision of the physica l measuring device, but by the algorithms used in the solution of the inver se problem. The error [dT(R)] relatively weakly depends on the number of re adings N-H Of the thermodynamic temperature to be determined in the studied area of the object as well as on the number of measurements N-S > N-H. The maximum spatial resolution necessary for practical medical tasks is about 6 mm, if the size of the area under investigation is approximate to 10 x 10 cm(2), N-H = 225, and the energy absorption coefficient is gamma 0.2 cm(-1 ). This spatial resolution is primarily determined by the thermophysical pr operties of human tissues.