Ultrasound blood flow/tissue imaging system

A crossbar switch adapted for use in an ultrasound imaging system for receiving a plurality of ultrasound beams through N adjacent transducer elements, said crossbar switch comprising:

• transducer element selector means outputting a plurality of transducer element enable signals designating the transducer elements forming said beam;
• and
• N switching circuits, each of which has a plurality of inputs connected to one of said transducer elements and all transducer elements spaced multiples of N transducer elements from said transducer element, respectively, each of said switching circuits connecting the transducer element designated by said transducer element selector means to an output port, whereby all of said transducer elements may be processed in N channels.

A system for processing signals corresponding to reflected ultrasound received through a plurality of adjacent ultrasound transducer elements, comprising multiplexer means for summing the outputs of transducer elements positioned equidistant from a transducer element at the approximate center of said plurality of adjacent transducer elements, whereby said multiplexer means reduces by approximately fifty percent the number of channels required to process said ultrasound signals from said transducer elements.

In a delay line comprising a plurality of inductors connected in series, a plurality of varactors connected between the junction between adjacent inductors, and a control input line connected to said varactors to control the capacitance of said varactors and hence the delay of said delay line, the improvement comprising impedance control means for continuously varying the input and output impedance of said delay line as a function of said control signal so that the input and output impedance varies in accordance with the impedance of said delay line as the impedance of said delay line varies with the capacitance of said varactors.

A delay line comprising a plurality of inductors connected in series, a plurality of varactors connected between the junction between adjacent inductors, and a control input line, said varactors being arranged in alternating polarities, with varactors connected in one polarity connected to a first control input line and varactors connected in the other polarity connected to a second control input line.

In an ultrasound imaging system generating blood flow velocity data from a beam of ultrasound returns taken from different sample site depths through an ultrasound transducer having a plurality of transducer elements, said beam being centered about at least one transducer element, a dynamic aperture system comprising:

• a plurality of variable gain circuits receiving respective signals from said transducer elements, each of said variable gain circuits generating an output bearing a ratio to the input that is determined by a respective gain control signal;
• and
• gain control means generating said gain control signals, said gain control means increasing the ratio between their output and input for signals from transducer elements further away from the center of each ultrasound beam as ultrasound returns from deeper sample sites are processed, whereby the aperture of said transducer becomes larger for sample sites of increasing depth.

In an ultrasound imaging system generating successive sets of data, each corresponding to a plurality of ultrasound return samples taken from the same sample site, said return samples having a frequency spectrum of f.sub.d, f.sub.d .+-.f.sub.r, f.sub.d .+-.2f.sub.r, f.sub.d +3f.sub.r . . . f.sub.d .+-.Mf.sub.r, where f.sub.r is the repetition frequency of said ultrasound transmissions and M is an integer greater than 1, a flow processor comprising N band-pass filters, each having respective pass bands centered at f.sub.o, f.sub.o .+-.f.sub.r, f.sub.o .+-.2f.sub.r, f.sub.o .+-.3f.sub.r . . . f.sub.o Mf.sub.r, where f.sub.o =(f.sub.r /N)P and P=0, 1, 3 . . . N-1, whereby the magnitude of the output of each band-pass filter is indicative of the velocity of moving sound scatterers at said sample site.

In an ultrasound transducer adapted for use with an ultrasound imaging system transmitting and receiving a plurality of ultrasound signals from respective transducer elements arranged in a linear array, said ultrasound signals being coupled through a coupling wedge comprising a hollow, wedge-shaped body defining a cavity filled with a coupling fluid, said wedge-shaped body having a first wall in contact with said transducer elements, a second wall positioned at an angle with respect to said first wall and adapted to contact the skin of a patient in order to position said transducer elements at a fixed predetermined angle with respect to the skin of said patient, and a third wall extending between said first and second walls to form a triangle with said first and second walls, the improvement comprising a sound-absorbing material lining the inner surface of said third wall to absorb ultrasound signals reflected from said second wall back into said coupling fluid.

In an ultrasound transducer adapted for use with an ultrasound imaging system transmitting and receiving a plurality of ultrasound signals from respective transducer elements arranged in a linear array, said ultrasound signals being coupled through a coupling wedge comprising a hollow, wedge-shaped body defining a cavity filled with a coupling fluid, said wedge-shaped body having a first wall in contact with said transducer elements, a second wall positioned at an angle with respect to said first wall and adapted to contact the skin of a patient in order to position said transducer elements at a fixed predetermined angle with respect to the skin of said patient, a third wall extending between said first and second walls to form a triangle with said first and second walls, and two opposed, generally parallel, triangularly shaped side walls enclosing the volume between said first, second and third walls, the improvement comprising a configuration for said coupling wedge wherein said third wall is angled toward one of said side walls so that any ultrasound reflected from said third wall is reflected toward one of said side walls rather than toward said first or second walls.