Ultrasonic imaging by radial scan of trapezoidal sector

Claim 2

The ultrasonic diagnostic imaging system of Claim 1, wherein said ultrasonic beams are transmitted at respective angles ϑ n , where n indicates the position of an ultrasonic beam along the transducer array, and the transmitted angle of each ultrasonic beam ϑ n differs from the adjacent beams ϑ n+1 and ϑ n-1 by an angular increment delta theta.

Claim 3

The ultrasonic diagnostic imaging system of Claim 2, wherein a centrally located axis to the transducer array is positioned at an angle of ninety degrees with respect to said linear transducer array, the ultrasonic beam on one side of said centrally located axis is transmitted at an angle of ninety degrees plus delta theta, and the ultrasonic beam on the other side of said centrally located axis is transmitted at an angle of ninety degrees minus delta theta.

Claim 4

The ultrasonic diagnostic imaging system of any one of Claims 1 to 3, wherein said actuating means includes means for actuating a predetermined number of transducer elements which comprise the transmit aperture for transmitting a focused ultrasonic beam, said predetermined number being relatively lesser when the focal point of said transmitted beam is relatively close to said transducer elements, and relatively greater when the focal point of said transmitted beam is relatively far from said transducer elements.

Claim 5

The ultrasonic diagnostic imaging system of Claim 4, wherein said predetermined number is determined by the number of transducer elements which satisfy a given sensitivity criterion at a given focal point.

Claim 6

The ultrasonic diagnostic imaging system of any one of Claims 1 to 5, further comprising means for receiving and focusing echo signal components from said beam direction angles, including means for dynamically varying receive focusing from the near field through the far field.

Claim 7

The ultrasonic diagnostic imaging system of Claim 6, further comprising means for varying the receive aperture during reception of echo signal components from a given beam direction, said receive aperture comprising relatively few transducer elements during reception of echo signal components from said near field and a relatively greater number of transducer elements during reception of echo signal components from said far field.

Claim 8

The ultrasonic diagnostic imaging system of Claim 7, wherein said receive aperture is varied in correspondence with the number of transducer elements which satisfy a given sensitivity criterion at a given point along said beam direction.

Claim 9

An ultrasonic diagnostic imaging system, for scanning and displaying an image sector in the form of a trapezoidal image area by means of a linear array of transducer elements in which the smallest side of the trapezoid is adjacent the transducer array and the angular sides of the trapezoid are outwardly angled from lateral points of the array which are displaced from the center of the array, comprising: means for actuating different groups of transducer elements of said array so as to steer transmitted ultrasonic beams in different angular directions with respect to said array by actuating individual elements of each group at sequentially different times; means for selecting the number of elements in each group in correspondence with a selected focal point of a transmitted ultrasonic beam, wherein the number of elements is relatively lesser for relatively near field focal points and is relatively greater for relatively far field focal points; means for receiving and focusing echo signal components received from said angular beam directions by passing echo signal components received by individual transducer elements through delay lines of respectively different delays corresponding to the direction of a particular beam and a given receive focal point; means for dynamically varying said receive focal point as echo signal components are received from the near field through the far field; means for combining said delayed and dynamically focused echo signal components to form a coherent echo signal; and means for dynamically varying the number of transducer elements from which echo signal components are combined from a relatively few elements in the near field to a relatively greater number in the far field by including echo signal components from elements laterally disposed from the beam center as echo signal components are received from increasing depths of field.

Claim 10

The ultrasonic diagnostic imaging system of Claim 9, wherein said means for selecting the number of elements in each group comprises means for sequentially actuating those transducer elements which satisfy a predetermined sensitivity criterion with respect to a given point along the angular direction of a transmitted ultrasonic beam.

Claim 11

The ultrasonic imaging system of Claim 9 or Claim 10, wherein said delay lines comprise digital shift registers through which echo signal components are shifted by a clock signal of a predetermined frequency.

Claim 12

The ultrasonic diagnostic imaging system of claim 11, wherein said means for dynamically varying said receive focal point comprises means for varying said frequency of clock signals of delay lines associated with transducer elements laterally disposed from said beam center from a relatively high frequency during reception of echo signal components from the near field to a relatively lower frequency during reception of echo signal components from the far field.

Claim 13

The ultrasonic diagnostic imaging system of Claim 12, wherein said relatively lower frequency is in the range of 10 to 25 MHz.

Claim 14

The ultrasonic diagnostic imaging system of any one of Claims 11 to 13, wherein said means for dynamically varying the number of transducer elements from which echo signal components are combined comprises means for inhibiting the times at which echo signal components from laterally disposed transducer elements are provided by said delay lines to said combining means.

Claim 15

The ultrasonic diagnostic imaging system of Claim 14, wherein echo signal components from the laterally disposed transducer elements are inhibited from transmission to said combining means by said inhibiting means for up to 340 microseconds of the initial period of echo reception.