Ultrasonic imaging apparatus and method of controlling delay

Patent metadata

Field	Value
Publication number	US-9165552-B2
Application number	US-201113520410-A
Country	US
Kind code	B2
Filing date	Feb 22, 2011
Priority date	Feb 23, 2010
Publication date	Oct 20, 2015
Grant date	Oct 20, 2015

Abstract

The present invention enables ultrasonic propagation time values after correction of refraction to be calculated in parallel for each receive channel, by using a recurrence relation in the depth direction. Moreover, accumulation of errors can be avoided by using an accurate propagation time value obtained in advance at a reference depth to correct the propagation time value each time the reference depth is reached. For this error correction, the recurrence relation to calculate the propagation time value can be an approximate expression. For example, the propagation time value can be calculated using the inclination of reference propagation time values between reference depths. In an actual circuit, received signals are sequentially stored in a memory, and a receive beam is formed by calculating an address position corresponding to the propagation time value of the ultrasonic wave, and adding the received signals stored in the calculated addresses.

First claim

The invention claimed is:

1. An ultrasonic imaging apparatus comprising:
an ultrasonic receiver having a plurality of receiving elements for receiving ultrasonic waves reflected or generated in an area of a subject through a medium having a sound velocity different from a sound velocity of the area;
a receive beam former which forms a receive beam signal by performing delay control on received signals of receive channels corresponding to at least a part of said receiving elements of said ultrasonic receiver, according to a propagation time from a focal point position of the receive beam to said receiving element; and
an image processor which generates an image using the receive beam signal, wherein said receive beam former sequentially calculates, for one of the receiving channels, propagation time values for a plurality of focal points by repeating processing for adding a change of propagation time value corresponding to a change amount of depth of focal point to an already calculated propagation time value to determine a propagation time value for a next focal point,
wherein the repeat processing can be independently executed for each of said receive channels, and said receive beam former calculates the propagation time values in parallel for at least a part of said receive channels, and
said receive beam former calculates the change of propagation time value using a recurrence relation and based on the change amount of depth of focal point, a recurrence parameter ξ i =cos θ′ corresponding to the area and a recurrence parameter η i =cos θ corresponding to the medium, where θ′ and θ are refractive angles of ultrasonic wave from the focal point to a receive channel in the area and medium respectively, and the recurrence parameter ξ i and the recurrence parameter η i being determined by the recurrence relation using the change amount of the depth of focal point, the sound velocity in the area and the sound velocity in the medium.

2. The ultrasonic imaging apparatus according to claim 1 , wherein the recurrence relation to determine the recurrence parameters is described in a polynomial of values of the recurrence parameters at adjacent depths of focal point.

3. The ultrasonic imaging apparatus according to claim 1 , wherein the change of propagation time value is determined as a polynomial of the depth of focal point.

4. The ultrasonic imaging apparatus according to claim 1 , wherein said receive beam former stores a reference propagation time value, which is a propagation time value determined in advance for a specific depth of focal point, and
when the depth of focal point reaches the specific depth of focal point in the repeat processing, the propagation time value at this depth of focal point is regarded as the stored reference propagation time value, and a propagation time value at a next depth of focal point is calculated based on this reference propagation time value.

5. The ultrasonic imaging apparatus according to claim 2 , wherein said receive beam former stores a reference propagation time value and reference recurrence parameters, which are a propagation time value and recurrence parameters determined in advance for a specific depth of focal point, and
when the depth of focal point reaches the specific depth of focal point in the repeat processing, the propagation time value and recurrence parameters at this depth of focal point are regarded as the stored reference propagation time value and reference recurrence parameters, and a propagation time value and recurrence parameters at a next depth of focal point are calculated based on the reference propagation time value and reference recurrence parameters.

6. The ultrasonic imaging apparatus according to claim 3 , wherein said receive beam former stores a propagation time value determined in advance for a specific depth of focal point, and coefficients of the polynomial to be used for focal points subsequent to the specific depth of focal point, and
when the depth of focal point reaches the specific depth of focal point in the repeat processing, the propagation time value at this depth of focal point is regarded as a stored reference propagation time value, and the change of propagation time value is determined by the polynomial using the stored coefficients in subsequent processing.

7. The ultrasonic imaging apparatus according to claim 1 , wherein said receive beam former stores propagation time values determined in advance for a plurality of reference focal points, and
when the focal point reaches any of the reference focal points in the repeat processing, the propagation time value at this focal point is regarded as a stored reference propagation time value, and a change of propagation time value in subsequent processing is determined by the reference propagation time value at this depth of focal point and a reference propagation time value at a next depth of focal point.

8. The ultrasonic imaging apparatus according to claim 1 , wherein
said receive beam former includes for each of said receive channels, a memory that stores in a time series received signals sequentially received from a receiving element corresponding to said receive channel, a memory read controller which controls reading from said memory, and a memory address calculation unit which calculates a read address of said memory,
said receive beam signal is formed by adding received signals of each of said receive channels which are read by said memory read controller from said memory according to the read address calculated by said memory address calculation unit, and
said memory address calculation unit calculates read address positions corresponding to the propagation time values which are sequentially calculated for the plurality of focal points to sequentially calculate read addresses corresponding to the plurality of focal points.

9. The ultrasonic imaging apparatus according to claim 8 , wherein said memory address calculation unit calculates a read address in a real number form, and
said receive beam former interpolates two received signals stored in an address corresponding to an integer portion of the calculated read address in the real number form and in a next address thereto, according to a decimal portion of the read address in the real number form, and forms a receive beam signal using the interpolated received signals.

10. The ultrasonic imaging apparatus according to claim 1 , wherein said ultrasonic receiver also serves as an ultrasonic transmitter for transmitting ultrasonic waves to the subject, and
said ultrasonic imaging apparatus forms an image of inside the subject by irradiating the subject with ultrasonic waves and receiving reflected ultrasonic waves that have been reflected in the subject.

11. An ultrasonic imaging apparatus, comprising:
an ultrasonic receiver having a plurality of receiving elements for receiving ultrasonic waves generated in an area of a subject through a medium having a sound velocity different from a sound velocity of the area;
an image reconstruction computing unit which obtains voxel array data evaluating an intensity of an ultrasonic wave generated in each voxel based on an ultrasonic wave received by said ultrasonic receiver; and
an image processor which obtains image data using the voxel array data obtained by said reconstruction computing unit,
wherein said image reconstruction computing unit sequentially calculates, for one of the receiving channels, propagation time values for a plurality of voxels by repeating processing for adding a change of propagation time value corresponding to a change amount of depth of a voxel to an already calculated propagation time value to determine a propagation time value

Assignees

• Oikawa Katsuya
• Yoda Haruo
• Canon Kk

Inventors

• Oikawa Katsuya
• Yoda Haruo

Classifications

• G01S7/52034

  Data rate converters · CPC title

• G10K11/346 Primary

  using phase variation · CPC title

• G01S7/52049

  using correction of medium-induced phase aberration · CPC title