Time gain compensation for ultrasonic medical imaging systems

Claim 2

An ultrasonic imaging method including time gain compensation (TGC) to correct received ultrasonic echoes for attenuation due to distance traversed by ultrasonic signals and echoes, said method for use with ultrasonic imaging system having transmitting and receiving means for transmitting the ultrasonic signals and receiving means for transmitting the ultrasonic signals and receiving the ultrasonic echoes, said receiving means having gain varying means, said method comprising determining attenuation characteristics of a body being examined, said determining step comprising the steps of: (a) transmitting beams of ultrasonic signals into said body, the direction of transmittal being a depth direction; (b) receiving echoes back from the interior of the body; (c) locating the source of the echoes; (d) amplifying the received echoes; (e) measuring the intensity of the amplified received echoes; (f) converting the measured intensity into pixel values according to the echo source location whereby the location of the pixel value in the image corresponds to the echoe source location in the body being examined; (g) selecting pixels along ultrasonic beams extending in the depth direction; (h) dividing said scanned depth into a plurality of segments; (i) using rows of the selected pixels to obtain average pixel values per segment in the depth direction; (j) said average pixel values providing intensity versus depth values for use in determining an intensity versus depth function extending along the scanned depth of the body; (k) fitting an intensity versus depth function curve over each of said plurality segments; (l) the slopes of said curves being the determined attenuation characteristics of the body; and the step of using the determined attenuation to vary the gain of the receiving means.

Claim 3

The method of claim 1 wherein said step of fitting curves to the function at each of said segments comprises using a least squares method.

Claim 4

The method of claim 2 including the step of determining attenuation characteristics of the body from a straight line fitted to each of the segments in a continuous curve.

Claim 5

The method of claim 3 wherein any discontinuities at the junction of the straight lines fitted to each of the segments are averaged to provide a continuous curve of straight lines with no discontinuities.

Claim 6

The method of claim 1 wherein the attenuation value obtained for each of the segments is used to obtain gain factors for the amplifier for these segments by finding the complement of the attenuation value.

Claim 7

The method of claim 5 wherein said gain factor is multiplied by a damping factor prior to using the gain factor to vary the gain of the receiver.

Claim 8

The method of claim 6, wherein said gain factor multiplied by the damping factor is added to the gain factor of a stored gain curve used to control the gain of the receiver.

Claim 9

The method of claim 7 including the step of comparing said attenuation values to a threshold, and using the gain curve values only when said attenuation values are more than the threshold.

Claim 10

The method of claim 6 and comparing the gain factor to a threshold to determine whether to use the gain factor in controlling the gain of the amplifier.

Claim 11

An ultrasonic imaging method including time gain compensation (TGC) to correct received ultrasonic echoes for attenuation due to distance traversed by ultrasonic signals and echoes, said method for use with ultrasonic imaging systems having transmitting and receiving means for transmitting the ultrasonic signals and receiving the ultrasonic echoes, said receiving means having gain varying means, said method comprising determining attenuation characteristics of a body being examined, said determining step comprising the steps of: (a) transmitting beams of ultrasonic signals into said body, the direction of transmittal being a depth direction; (b) receiving echoes back from the interior of the body; (c) locating the source of the echoes; (d) amplifying the received echoes; (e) measuring the intensity of the amplified received echoes; (f) converting the measured intensity into pixel values according to the echo source location whereby the location of the pixel value in the image corresponds to the echo source location in the body being examined; (g) selecting pixels along ultrasonic beams extending in the depth direction; (h) dividing said scanned depth into a plurality of segments; (i) using rows of the selected pixels to obtain average pixel values per segment in the depth direction; (j) said average pixel values providing intensity versus depth values for use in determining an intensity versus depth function extending along the scanned depth of the body; (k) fitting an intensity versus depth function line over each of said plurality of segments; (l) the slope of each of said lines being one of the determined attenuation characteristics; providing a predetermined gain function to control the amplification of the received echoes to provide echoes having intensities independent of the distance between the transducer and the source of the echo; and automatically varying the gain function as a function of the determined attenuation characteristics.

Claim 12

An ultrasonic imaging method including time gain compensation (TGC) to correct received ultrasonic echoes for attenuation due to distance traversed by ultrasonic signals and echoes, said method for use with ultrasonic imaging systems having transmitting and receiving means for transmitting the ultrasonic signals and receiving the ultrasonic echoes, said receiving means having gain varying means, said method comprising determining attenuation characteristics of a body being examined, said determining step comprising the steps of: (a) transmitting beams of ultrasonic signals into said body, the direction of transmittal being a depth direction; (b) receiving echoes back from the interior of the body; (c) locating the source of the echoes; (d) amplifying the received echoes; (e) measuring the intensity of the amplified received echoes; (f) converting the measured intensity into pixel values according to the echo source location whereby the location of the pixel value in the image corresponds to the echo source location in the body being examined; (g) selecting pixels along ultrasonic beams extending in the depth direction; (h) dividing said scanned depth into a plurality of segments; (i) using rows of the selected pixels to obtain average pixel values per segment in the depth direction; (j) said average pixel values providing intensity versus depth values for use in determining an intensity versus depth function extending along the scanned depth of the body; (k) fitting an intensity versus depth function line over each of said plurality of segments; (l) the slope of each of said lines being one of the determined attenuation characteristics; providing a predetermined gain function to control the amplification of the received echoes to provide echoes having intensities independent of the distance between the transducer and the source of the echo; and automatically varying the gain function as a function of the determined attenuation characteristics.

Claim 13

The method of claim 10 including the further step of using the complement of the slopes of the lines to vary the predetermined gain function.

Claim 14

The method of claim 11 including the step of: damping the complement of the slope prior to using said complement to vary said predetermined gain function.