Method and system for examining the interior material of an object, such as a pipeline or a human body, from a surface of the object using ultrasound

A method and system are described for examining the interior material of an object from a surface of an object using ultrasound having a frequency of at least 100 kHz. The method comprises the step of transmitting at least a first ultrasound signal by a first ultrasound transmitter of a first number of ultrasound transmitters to the interior material of the object for forming a first image in order to determine, according for example to the principle of inverse wave field extrapolation, where in the interior material of the object reflections and/or diffractions occur. Reflections and/or diffractions of the first ultrasound signal from the interior material of the object are received using a second number of ultrasound receivers which are acoustically coupled to the surface of the object at positions which are distributed in at least one dimension of the surface of the object. With each of the second number of ultrasound receivers, a receiving signal is generated from the received reflections and/or diffractions of the first ultrasound signal from the interior material of the object, and each of the receiving signals generated by one of the ultrasound receivers is processed separately into a separate dataset. The separate datasets of all the ultrasound receivers are combined to the first image.