a diagnostic unit it is conceivable to align hf ultrasound probe 20 a and the lf ultrasound probe 30 a automatically according to the position determined by the detection device it is important for the success of the treatment of tumor 5 to adjust a low frequency oscillation that is suitable for triggering resonance phenomena which then initiate cell death in the largest possible number of tumor cells the excitation oscillation appropriate for this varies approximately within a range between 10 and 40 khz since the appropriate excitation oscillation is tumor specific it is possible by a preliminary determination of the optimum frequency or of the optimum frequency range to achieve significantly better treatment success to do this tumor tissue is removed and analyzed in a frequency determination unit this frequency determination unit includes a monocrystalline oscillation probe frequency range 16 to 80 khz which is excited by way of an appropriate generator this monocrystalline oscillation probe is configured two dimensionally in such a manner that there is space for a plurality of recesses on its upper side the tissue sample may be distributed in these recesses an oscilloscope connected to the monocrystalline oscillation probe determines the oscillation frequency of the monocrystalline oscillation probe when excited by the generator.