A method for determining, in real time, the probability that target biological tissue is opposite an ultrasonic transducer, the method including: transmitting, via an ultrasonic transducer, an ultrasonic signal into biological tissue; the ultrasonic transducer receiving the transmitted ultrasonic signal which has been backscattered by the biological tissue; calculating at least two instantaneous parameters of the backscattered ultrasonic signal; calculating a predictive value of the presence of an acoustic signature of target biological tissue, the predictive value being calculated via a statistical law using the at least two calculated instantaneous parameters; estimating the probability that the target biological tissue is opposite the ultrasonic transducer, the estimation depending on the calculated predictive value and/or on at least one strength condition based on at least one of the two calculated instantaneous parameters.