A system for determining a mechanical property of a tissue of a subject, the system comprising: an ultrasound transmitter which drives a transducer array such that an ultrasonic beam is produced which is directed substantially perpendicular to the front surface of the transducer array, such that a shear wave propagates through the tissue; an ultrasound receiver configured to - receive analog echo signals produced by the transducer array as the shear wave propagates through the subject in response to ultrasonic energy reflected back from the tissue to the transducer array; and - produce digitized beam samples from the analog echo signals wherein the digitized beam samples are indicative of a magnitude and a phase of the analog echo signals; wherein the receiver further comprises a processor, wherein the processor is configured to - receive the digitized beam samples representing the shear wave propagation inside the tissue as a function of time and space; and - calculate a mechanical property of the tissue based on the received beam samples; wherein the calculation of the mechanical property comprises: performing a two-dimensional Fourier transformation of the shear wave as a function of time and space into the temporal frequency and spatial frequency domain to form a k-space representation of the shear wave; analyzing the k-space representation of the shear wave to estimate an attenuation of the shear wave as it propagates through the tissue, wherein the analyzing comprises identifying the full width at half maximum, FWHM, of a peak of a magnitude profile of the k-space representation; and calculating the mechanical property using the estimated attenuation of the shear wave as it propagates through the tissue. an ultrasound transmitter which drives a transducer array such that an ultrasonic beam is produced which is directed substantially perpendicular to the front surface of the transducer array, such that a shear wave propagates through the tissue; an ultrasound receiver configured to - receive analog echo signals produced by the transducer array as the shear wave propagates through the subject in response to ultrasonic energy reflected back from the tissue to the transducer array; and - produce digitized beam samples from the analog echo signals wherein the digitized beam samples are indicative of a magnitude and a phase of the analog echo signals; - receive analog echo signals produced by the transducer array as the shear wave propagates through the subject in response to ultrasonic energy reflected back from the tissue to the transducer array; and - produce digitized beam samples from the analog echo signals wherein the digitized beam samples are indicative of a magnitude and a phase of the analog echo signals; wherein the receiver further comprises a processor, wherein the processor is configured to - receive the digitized beam samples representing the shear wave propagation inside the tissue as a function of time and space; and - calculate a mechanical property of the tissue based on the received beam samples; - receive the digitized beam samples representing the shear wave propagation inside the tissue as a function of time and space; and - calculate a mechanical property of the tissue based on the received beam samples; wherein the calculation of the mechanical property comprises: performing a two-dimensional Fourier transformation of the shear wave as a function of time and space into the temporal frequency and spatial frequency domain to form a k-space representation of the shear wave; analyzing the k-space representation of the shear wave to estimate an attenuation of the shear wave as it propagates through the tissue, wherein the analyzing comprises identifying the full width at half maximum, FWHM, of a peak of a magnitude profile of the k-space representation; and calculating the mechanical property using the estimated attenuation of the shear wave as it propagates through the tissue. performing a two-dimensional Fourier transformation of the shear wave as a function of time and space into the temporal frequency and spatial frequency domain to form a k-space representation of the shear wave; analyzing the k-space representation of the shear wave to estimate an attenuation of the shear wave as it propagates through the tissue, wherein the analyzing comprises identifying the full width at half maximum, FWHM, of a peak of a magnitude profile of the k-space representation; and calculating the mechanical property using the estimated attenuation of the shear wave as it propagates through the tissue.