Patent ID: 6108572
Filing Date: 2000-08-22
Classification: A61B,G01P,G01S

Abstract:
A method for imaging matter in a scan plane, comprising the steps of:transmitting wave energy focused at a first transmit focal position along a scan line and having a first fundamental frequency during each of N transmit firings, wherein N.gtoreq.2 and said wave energy of said N transmit firings is phase encoded across firings;transducing wave energy transmitted in each of said N transmit firings and returned from matter to form N sets of receive signals;beamforming each of said N sets of receive signals to form N receive vectors in succession, each receive vector comprising data acquired along said scan line;filtering said N receive vectors across firings to form a near-field receive vector in which first fundamental signal components of said N receive vectors are high pass filtered or substantially suppressed and (sub)harmonic signal components of said N receive vectors are substantially all-passed;transmitting wave energy focused at a second transmit focal position along said scan line and having a second fundamental frequency during an (N+1)-th transmit firing, wherein said second transmit focal position has a depth greater than the depth of said first transmit focal position;transducing wave energy transmitted in said (N+1)-th transmit firing and returned from matter to form an (N+1)-th set of receive signals;beamforming said (N+1)-th set of receive signals to form an (N+1)-th receive vector comprising data acquired along said scan line;filtering said (N+1)-th receive vector to form a far-field receive vector in which a second fundamental signal component of said (N+1)-th receive vector is substantially suppressed and a (sub)harmonic signal component of said (N+1)-th receive vector is substantially all-passed;combining said near- and far-field receive vectors to form a composite receive vector; anddisplaying an image which is a function of said composite receive vector.