Corrections for pulse reverberations and phasefront aberrations in ultrasound imaging

A method for corrections of Class I and Class II pulse reverberations in the received signal along each image beam direction in ultrasound imaging, where the ultrasound beams on transmit and or receive are formed with an ultrasound transducer array that has a two-dimensional distribution of elements, and

• the array elements on transmit and receive being grouped into sub-apertures according to known methods, where on transmit the same signal is transmitted on each sub-aperture element with individual delay and possibly amplitude corrections so that sub-aperture transmit beams are formed, and on receive the signals from the individual elements after delay and possibly amplitude corrections are summed into receive sub-aperture signals so that sub-aperture receive beams are formed, the dimensions of the sub-apertures being less than the spatial correlation length of the pulse reverberation wave fronts at the array,
• and where in a 1st transmit event, the transducer elements are driven with a 1st set of transmit pulses for direction steering and focusing of the beam in said image beam direction, and
• a set of 1st sub-aperture receive signals are recorded from this 1st transmit event with a set of 1st sub-aperture receive beams being directed in the mirror direction to said image beam direction around the normal to each sub-aperture,
• an initial interval of each of the 1st sub aperture receive signals is filtered in corresponding reverberation correction filters to generate a set of reverberation correction transmit signals corresponding to each sub-aperture, where each of said reverberation correction transmit signals are transmitted at the corresponding sub-aperture in a 2nd transmit event.

A method for corrections of Class II or Class III pulse reverberations in the received beam signal in ultrasound imaging for an image range interval around a receive focus rf along each image beam direction, where the ultrasound beams on transmit and or receive are formed with an ultrasound transducer array that has a two-dimensional distribution of elements, and for each image beam direction,

• A:
• transmitting into the tissue a 1st pulsed transmit beam with focus at rt along the image beam direction,
• forming a 1st receive beam signal from the array element signals received from said 1st transmit beam, the 1st receive beam being focused at rf along the image beam direction, to form a basis to estimate a reverberation corrected image signal for said image range interval around rf, and
• forming a 2nd receive beam signal from the array element signals received from said 1st transmitted beam with a 2nd receive beam spatial response, and
• B:
• transmitting a 2nd pulsed transmit beam with a 2nd transmit beam spatial response, and
• forming a 3rd receive beam signal from the array element signals received from said 2nd transmit beam with a 3rd receive beam spatial response,
• C:
• forming a 4th signal by filtering said 2nd receive beam signal with said 3rd receive beam signal with further filtering with a reflection coefficient filter to form an estimate of pulse reverberations in said 1st receive beam signal in said image range interval around rf, so that
• reverberation corrections of said 1st receive beam signal is obtained by subtracting said 4th signal from said 1st receive beam signal to form a reverberation corrected beam signal of the ultrasound image in said image range interval around rf along said image beam direction.

A method for corrections of Class III pulse reverberations in the received element or sub-aperture signals in ultrasound imaging for an image range interval around rf along each image beam direction, where the ultrasound beams on transmit and or receive are formed with an ultrasound transducer array that has a two-dimensional distribution of elements, and for each image beam direction,

• A:
• transmitting a 1st pulsed transmit beam into the tissue with focus at rt along the image beam direction, and
• recording 1st receive element or sub-aperture signal received from said 1st transmit beam, the 1st receive subapertures being directed along the image beam direction, to form a basis to estimate a reverberation corrected element or sub-aperture signal for said image range interval around rf, and
• forming a 2nd receive beam signal from the array element signals received from said 1st transmit beam, the 2nd receive beam spatial response having in said image range interval convex spherical phase fronts centered around the array center, and B:—transmitting a 2nd pulsed transmit beam into the tissue, said 2nd beam having a focus as the mirror point of rf around the array reflecting face, and
• B:
• recording 3rd receive element or sub-aperture signals received from said 2nd transmit beam, the 3rd receive sub-apertures being directed along said image beam direction, and
• C:
• forming a 4th element or sub-aperture signals by filtering said 2nd receive beam signal with said 3rd receive elements or sub-aperture signals with further filtering with a reflection coefficient filter to form an estimate of Class III pulse reverberations in said 1st receive element or sub-aperture signals in said image range interval around rf, so that
• reverberation corrections of said 1st receive element or sub-aperture signals are obtained by subtracting said 4th element or sub-aperture signals from said 1st receive element or sub-aperture signals to form reverberation corrected receive element or sub-aperture signals of the ultrasound image in said image range interval around rf along said image beam direction.