Incoherent retrospective dynamic transmit focusing

Abstract

An ultrasonic diagnostic imaging system produces an image with an extended focal range by transmitting a plurality of beams spaced along an array for multiline reception. The receive multilines of a plurality of transmit beams are spatially aligned and are combined with phase adjustment between the respective receive multilines to prevent undesired phase cancellation. The combined multilines produce the effect of an extended transmit focus so that an image produced using the combined multilines exhibits an extended focal range. To prevent motion artifacts the multiline order is adjustable as a function of image motion.

Description

technical field [0001] The present invention relates to medical diagnostic ultrasound systems, and more particularly, to ultrasound systems that use multiline receive beamformers to expand the focal zone. Background technique [0002] The principle of synthetic focusing, by means of which the ultrasound image is focused at each point in the image field, is the subject of investigation. For example, US Patent 4,604,697 (Luthra et al.) describes a synthetic focusing technique in which ultrasound pulses are emitted sequentially from each element of an ultrasound transducer array. Echo signals received from each transmission are received by all elements of the array and stored. After all signals have been received, focused echoes can be formed at each point in the image field based on knowledge of the position of each transducer element relative to each point in the image and the transit time of the ultrasound signal to and from each point Signal. The appropriate received sig...

AI Technical Summary

Problems solved by technology

A disadvantage is that r.f. signals from the entire image field must be stored for processing

This requires a considerable amount of information storage

The second disadvantage is that a considerable amount of processing is required to select and weight the data for each point in the image, and then combine the appropriately weighted data to compute the image data points

A third disadvantage is that this scheme is only effective for very shallow penetration depths, since the energy emitted by a single transducer element is limited

The downside of this coherent property is that the reflected signals can interfere with each other constructively and destructively, creating mottled patterns called "speckles" that cover the desired tissue image and degrade the image quality. contrast

Since the speckle pattern has no phase or amplitude variation over time, it cannot be suppressed simply by averaging the image signal over time

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