Claims:1. A method (600), comprising:
receiving (602) a plurality of response signals from an organ of a subject, by a plurality of transducer elements of an ultrasound scanner in response to a transmitted beam emitted from the plurality of transducer elements, wherein the plurality of response signals comprises anatomical information corresponding to a location among a plurality of locations in the organ;
estimating (604) a distortion parameter corresponding to the location, based on the plurality of response signals, wherein the distortion parameter comprises at least one of a frequency shift value and a bandwidth value corresponding to the transmitted beam at the location;
generating (606) a modified transmitted beam corresponding to the transmitted beam based on the distortion parameter;
generating (608) a plurality of beamformed outputs corresponding to the plurality of locations based on a respective modified transmitted beam and a respective plurality of response signals; and
generating (610) a diagnostic image corresponding to the organ based on the plurality of beamformed outputs.
2. The method (600) as claimed in 1, further comprising processing the plurality of response signals by a dynamic filter to enhance signal to noise ratio of the plurality of response signals.
3. The method (600) as claimed in 1, wherein generating (606) the modified transmitted beam comprises:
generating a modified transmitted pulse based on the distortion parameter; and
linearly combining a plurality of modified transmitted pulses delayed by a plurality of corresponding time delay values.
4. The method (600) as claimed in 3, wherein generating (606) the modified transmitted pulse comprises generating a pulse based on the frequency shift value and a transducer impulse response.
5. The method (600) as claimed in 3, wherein generating (606) the modified transmitted pulse comprises limiting bandwidth of a transmitted pulse to the bandwidth value.
6. The method (600) as claimed in 1, wherein generating (608) a plurality of beamformed outputs comprises:
generating an echo data model based on the plurality of response signals;
generating a transmit data model based on the modified transmitted beam; and
determining a beamformed output based on the echo data model and the transmit data model.
7. The method (600) as claimed in 6, wherein the echo data model and the transmit data model comprises matrices having dimensions based on a sampling frequency, a transmit delay time and an imaging depth value.
8. The method (600) as claimed in 6, wherein the beamformed output is determined by using a weighted least squares technique.
9. The method (600) as claimed in 1, wherein estimating (604) the distortion parameter comprises performing a correlation between at least one of the plurality of response signals with a reference response signal.
10. The method (600) as claimed in 1, wherein estimating (604) the distortion parameter comprises generating an auto regressive model corresponding to at least one of the plurality of response signals.
11. A system (100), comprising:
a plurality of transducer elements (104) of an ultrasound probe configured to receive a plurality of response signals generated by an organ in a subject in response to a transmitted beam emitted from the plurality of transducer elements (104), wherein the plurality of response signals comprises anatomical information corresponding to a location among a plurality of locations in the organ;
a distortion module (108) communicatively coupled to the plurality of transducer elements (104) and configured to estimate a distortion parameter corresponding to the location, based on the plurality of response signals, wherein the distortion parameter comprises at least one of a frequency shift value and a bandwidth value corresponding to the transmitted beam at the location;
a beam generator (114) communicatively coupled to the distortion module (108) and configured to generate a modified transmitted beam corresponding to the location based on the distortion parameter;
a beamformer (116) communicatively coupled to the beam generator (114) and the plurality of transducer elements (104) and configured to generate a plurality of beamformed outputs corresponding to a plurality of locations of the organ based on a respective modified transmitted beam and a respective plurality of response signals;
an image processor (120) communicatively coupled to the beamformer (116) and configured to:
receive a plurality of beamformed outputs corresponding to the plurality of locations in the organ based on corresponding plurality of modified transmitted beams;
generate a diagnostic image corresponding to the organ based on the plurality of beamformed outputs; and
present the diagnostic image to a medical professional for providing a treatment to the subject.
12. The system (100) as claimed in 11, wherein the image processor (120) is further configured to process the plurality of response signals by a dynamic filter.
13. The system (100) as claimed in 11, wherein the beam generator (114) is configured to:
generate a modified transmitted pulse corresponding to a transmitted pulse based on the distortion parameter; and
combine linearly a plurality of modified transmitted pulses delayed by a plurality of corresponding time delay values.
14. The system (100) as claimed in 13, wherein the beam generator (114) is configured to generate a pulse based on the frequency shift value and a transducer impulse response.
15. The system (100) as claimed in 13, wherein the beam generator (114) is configured to limit bandwidth of the transmitted pulse to the bandwidth value.
16. The system (100) as claimed in 11, wherein the beamformer (116) is configured to:
generate an echo data model based on the plurality of response signals;
generate a transmit data model based on the modified transmitted beam; and
determine a beamformed output based on the echo data model and the transmit data model.
17. The system (100) as claimed in 16, wherein the beamformer (116) is configured to generate the echo data model and the transmit data model as matrices having dimensions based on sampling frequency, transmit delay time and depth value.
18. The system (100) as claimed in 16, wherein the beamformer (116) is configured to determine the beamformed output using a weighted least squares technique.
19. The system (100) as claimed in 11, wherein the distortion module (108) is configured to estimate the distortion parameter using a correlation between at least one of the plurality of response signals with a reference response signal.
20. The system (100) as claimed in 11, wherein the distortion module (108) is configured to estimate the distortion parameter based on an auto regressive model corresponding to at least one of the plurality of response signals.
, Description:BACKGROUND
[0001] Embodiments of the present specification relate generally to ultrasound imaging, and more particularly to systems and methods for enhancing the ultrasound imaging of deeper tissues.
[0002] Ultrasound imaging is based on the scattering of acoustic energy by materials such as a tissue region, interacting with ultrasound waves. When an acoustic wave is emitted into an object, such as an anatomical organ, the amplitude of the reflected energy is used to generate ultrasound images, and frequency shifts in the backscattered ultrasound signals provides information relating to moving targets, such as blood. Typically, ultrasound beams having wave frequencies up to 50MHz are used in multiple operating modes with specific objectives. In medical imaging, in an A-mode ultrasound imaging, a single transducer is used to measure echoes as a function of depth to enable therapeutic ultrasound. In a B-mode ultrasound imaging, two-dimensional (2D) images are acquired in an image plane. A 2D image in a plane normal to the B-mode plane is acquired using a C-mode ultrasound imaging. A motion information is acquired in a M-mode ultrasound imaging with the acquisition of A-mode or B-mode images at multiple instants of time. Similarly, the ultrasound scanner may also be operated in a Doppler mode to measure velocity information of blood flow. A pulse inversion mode and a harmonic mode of the ultrasound imaging are used for distortion reduction in the 2D image.
[0003] Conventionally, the scattered acoustic energy is received as electrical signals and a directional signal reception is achieved by beamforming techniques. Time of arrival delays and phase shift delays are compensated by the beamforming techniques. More recently, retrospective transmit beamforming is used to aid directional transmission of ultrasound energy for better image formation. When deeper tissue volumes are examined by the ultrasound scanner, a frequency attenuation of the transmitted ultrasound beam is observed. Conventional beamforming techniques are not able to compensate for the frequency shifts and additional processing techniques are needed for imaging deeper tissues. Additional techniques, such as dynamic filtering, are employed for enhancing signal to noise ratio in the ultrasound image, especially at deeper depths.
[0004] Further, accuracy of medical imaging modality such as ultrasound, is highly dependent on operators, such as sonographers, doctors, medical students, radiology specialists and medical technologists. Successful examination with an ultrasound imaging system involves specific skills on the part of the operator, including good hand-eye coordination, correct localization of a region of interest, accurate interpretation of ultrasound images, correct use of ultrasound system modes among others.
BRIEF DESCRIPTION
[0005] In accordance with one aspect of the invention, a method is presented. The method includes receiving a plurality of response signals from an organ of a subject, by a plurality of transducer elements of an ultrasound scanner in response to a transmitted beam emitted from the plurality of transducer elements. The plurality of response signals comprises anatomical information corresponding to a location among a plurality of locations in the organ. The method further includes estimating a distortion parameter corresponding to the location, based on the plurality of response signals. The distortion parameter comprises at least one of a frequency shift value and a bandwidth value corresponding to the transmitted beam at the location. The method further includes generating a modified transmitted beam corresponding to the transmitted beam based on the distortion parameter. The method also includes generating a plurality of beamformed outputs corresponding to the plurality of locations based on a respective modified transmitted beam and a respective plurality of response signals. Further, the method includes generating a diagnostic image corresponding to the organ based on the plurality of beamformed outputs. The method also includes providing a treatment to the subject based on the diagnostic image.
[0006] In accordance with another aspect of the present invention, a system is disclosed. The system includes a plurality of transducer elements of an ultrasound probe configured to receive a plurality of response signals generated by an organ in a subject in response to a transmitted beam emitted from the plurality of transducer elements. The plurality of response signals comprises anatomical information corresponding to a location among a plurality of locations in the organ. The system further includes a distortion module communicatively coupled to the plurality of transducer elements and configured to estimate a distortion parameter corresponding to the location, based on the plurality of response signals. The distortion parameter comprises at least one of a frequency shift value and a bandwidth value corresponding to a transmitted pulse at the location used to generate the transmitted beam. The system further includes a beam generator communicatively coupled to the distortion module and configured to generate a modified transmitted beam corresponding to the location based on the distortion parameter. The system also includes a beamformer communicatively coupled to the beam generator and the plurality of transducer elements and configured to generate a plurality of beamformed outputs corresponding to a plurality of locations of the organ based on a respective modified transmitted beam and a respective plurality of response signals. Further, the system includes an image processor communicatively coupled to the beamformer and configured to receive a plurality of beamformed outputs corresponding to the plurality of locations in the organ based on corresponding plurality of modified transmitted beams. The image processor is further configured to generate a diagnostic image corresponding to the organ based on the plurality of beamformed outputs. The image processor is also configured to present the diagnostic image to a medical professional for providing a treatment to the subject.
DRAWINGS
[0007] These and other features and aspects of embodiments of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
[0008] FIG. 1 is a diagrammatic illustration of an ultrasound system for imaging deeper tissues in accordance with an exemplary embodiment;
[0009] FIG. 2 is a graph illustrating frequency shift characteristics exhibited by deeper tissues in accordance with an exemplary embodiment;
[0010] FIG. 3 is a graph illustrating frequency spectrum of modified transmit beam in accordance with an exemplary embodiment;
[0011] FIG.4 is a schematic flow diagram illustrating a model based transmit beamforming in accordance with an exemplary embodiment;
[0012] FIG. 5A is an ultrasound image 500 obtained from conventional retrospective transmit beamforming in accordance with an exemplary embodiment;
[0013] FIG. 5B is an ultrasound image obtained from model based transmit beamforming disclosed herein in accordance with an exemplary embodiment; and
[0014] FIG. 6 is a flow chart illustrating a method for ultrasound imaging deeper tissues in accordance with an exemplary embodiment.
DETAILED DESCRIPTION
[0015] Embodiments of the present specification relate to systems and methods for ultrasound imaging. More particularly, embodiments of the present specification relate generally to enhancing the ultrasound imaging of deeper tissues in a subject.
[0016] FIG. 1 is a diagrammatic illustration of an ultrasound system 100 for imaging of deeper tissues in a subject, in accordance with an exemplary embodiment. The ultrasound system 100 includes an ultrasound probe 102 having a plurality of transducer elements 104. The ultrasound system further includes a transmitter 108 communicatively coupled to the ultrasound probe 102 and configured to transmit an ultrasound signal referred herein as a transmitted beam 106. In one embodiment, the transmitter 108 may provide transmit beamforming for enhanced image formation from the ultrasound system 100. The plurality of transducer elements 104 transmits an ultrasound signal into a subject 128 to generate a plurality of response signals 110. In one embodiment, the subject 128 is an anatomical organ of the subject under medical examination. Further, the transmitted beam 106 is formed as a sum of a plurality of delayed versions of a transmitted pulse. The plurality of response signals 110 result from the transmitted beam 106 being scattered by the subject 128. Further, the plurality of response signals 110 corresponds to a location in the subject 128 at a penetration depth 130. The term ‘penetration depth’ used herein refers to a distance of tissue from the transducer elements 104 generating the plurality of response signals 110. Amplitudes of the plurality of response signals 110 provides information about tissues in the location. Further, the plurality of response signals 110 includes spatial information (i.e., axial information along the beam direction and lateral information along a penetration depth value) and temporal information at the location of the organ. The plurality of transducer elements 104 is further configured to receive the plurality of response signals 110. The ultrasound system 100 further includes a receiver 112 communicatively coupled to the ultrasound probe 102 and configured to receive the plurality of response signals 110. The plurality of response signals 110 corresponds to a location of the organ in the subject under medical examination. It may be noted that the ultrasound probe 102 is configured to generate a respective plurality of response signals corresponding to a plurality of locations of the organ. The plurality of locations of the organ corresponds to tissues within the organ at a plurality of penetration depth values.
[0017] In the illustrated embodiment, the ultrasound system 100 further includes a distortion module 118, a beam generator 114, a receive beamformer 116, a memory module 122, an image processor 120, and a display device 124 for implementing a model based transmit beamforming technique and providing a diagnostic image 140 having a plurality of pixels. The plurality of pixels corresponds to a plurality of locations of the organ of the subject. The diagnostic image 140 is a two-dimensional image (2D image) representative of anatomical details of tissues in a region of interest. The plurality of pixels of the diagnostic image 140 are arranged in axial and lateral directions. The diagnostic image 140 is an enhanced ultrasound image with enhanced axial and lateral resolutions.
[0018] In one embodiment, the distortion module 118 is communicatively coupled to the plurality of transducer elements 104 via the receiver 112 and configured to estimate a distortion parameter 132, based on the plurality of response signals 110. The distortion parameter 132 corresponds to a location of the organ. The distortion parameter 132 comprises at least one of a frequency shift value and a bandwidth value corresponding to a transmitted pulse used to generate the transmitted beam 106 during propagation at the location. The distortion module 118 is configured to estimate the distortion parameter 132 using a correlation between at least one of the plurality of response signals 110 with a reference response signal. In one embodiment, the reference response signal is derived from the transmitted pulse. In another embodiment, the reference response signal is based on the transmitted beam 106. In another embodiment, the distortion module 118 is configured to estimate the distortion parameter 132 using an auto regressive model. It may be noted that the distortion module 118 is configured to generate a plurality of distortion parameters corresponding to the plurality of locations in the subject 128.
[0019] In one embodiment, the beam generator 114 is communicatively coupled to the distortion module 118 and configured to generate the transmitted beam 106. In one embodiment, the beam generator 114 is configured to generate a square wave signal having a required frequency. Further, the beam generator 114 is configure to generate the transmitted beam 106 based on the square wave signal and a transducer impulse response. In one embodiment, the beam generator 114 is further configured to generate a modified transmitted beam based on the distortion parameter. In one embodiment, the modified transmitted beam is generated by compensating the frequency shift value in the transmitted beam 106. In another embodiment, the modified transmitted beam is generated by compensating the bandwidth value in the transmitted beam 106. The modified transmitted beam corresponds to a location of the organ. The beam generator 114 is configured to generate a modified transmitted pulse corresponding to the transmitted pulse 136 based on the distortion parameter 132The beam generator is also configured to shift a central frequency of the modified transmitted pulse based on a frequency shift value. The beam generator is further configured to limit a bandwidth of the modified transmitted pulse to the bandwidth value. Further, the beam generator 114 is configured to combine a plurality of modified transmitted pulses delayed by a plurality of corresponding time delay values to generate a modified transmitted beam 134. In one embodiment, the beam generator 114 is configured to generate a pulse based on the frequency shift value and a transducer impulse response. The transducer impulse response corresponds to transfer function of the transducer element. In one embodiment, the transducer impulse response is obtained from measurements. In an alternate embodiment, the transducer response is specified by an operator and is retrieved from a known memory location. During the scanning procedure, the beam generator 114 is configured to generate a plurality of modified transmitted beams corresponding to the plurality of locations of the organ.
[0020] In one embodiment, the beamformer 116 is communicatively coupled to the beam generator 114 and the plurality of transducer elements 104 via the receiver 112. The beamformer 116 is configured to generate a plurality of beamformed outputs corresponding to the plurality of locations based on respective plurality of response signals and the respective modified transmitted beam. The plurality of beamformed outputs corresponds to a plurality of pixel values in the ultrasound image.
[0021] In one embodiment, the beamformer 116 is configured to generate an echo data model based on the plurality of response signals 110. The beamformer is further configured to generate a transmit data model based on the modified transmitted beam134. The beamformer 116 is also configured to determine a beamformed output based on the echo data model and the transmit data model. The beamformer 116 is configured to generate the echo data model and the transmit data model as matrices based on samples of the plurality of response signals and samples of modified transmitted beam 134. The echo data model matrix and the transmit data model matrix have dimensions based on one or more of a sampling frequency, transmit delay time, duration of the modified transmitted beam 134 and depth value. The beamformer 116 is configured to at least in part compensate for a time delay and a phase shift in each of the plurality of response signals. In a non-limiting example, the beamformer 116 is configured to determine the beamformed output using a weighted least squares technique. In one embodiment, the beamformer 116 is further configured to process the plurality of beamformed outputs 138 by a dynamic filter.
[0022] In one embodiment, the image processor 120 is communicatively coupled to the beamformer 116 and configured to receive the plurality of beamformed outputs 138 corresponding to a plurality of locations in the subject 128 based on corresponding plurality of modified transmitted beams. The image processor 120 is further configured to generate the diagnostic image 140 corresponding to the subject 128 based on the plurality of beamformed outputs 138. In one embodiment, the image processor 120 is further configured to process the plurality of beamformed outputs 138 by a dynamic filter.
[0023] In certain embodiments, the image processor 120 includes at least one of a general purpose computer, a graphics processor unit (GPU), a digital signal processor, and a controller. In other embodiments, the image processor 120 includes a customized processor element such as, but not limited to, application specific integrated circuit (ASIC) and field programmable gate array (FPGA). The image processor 120 may receive additional inputs from a user through a keypad or a mouse or any other input device. The image processor 120 may also be configured to provide one or more outputs such as, but not limited to, an audio, visual or tactile sensory signals. In some embodiments, the image processor 120 may perform one or more functions of at least one of the transmitter 108, the receiver 112, the distortion module 118, the beam generator 114 and the receive beamformer 116. The image processor 120 may include more than one processor co-operatively working with each other for performing intended functionalities. The image processor 120 is further configured to store contents into the memory module 122 and retrieve contents from the memory module. In one embodiment, the image processor 120 is configured to initiate and control the functionality of at least one of the transmitter 108, the receiver 112, the distortion module 118, the beam generator 114 and the receive beamformer 116.
[0024] In one embodiment, the memory module 122 is a random access memory (RAM), read only memory (ROM), flash memory or any other type of computer readable memory accessible by at least one of transmitter 108, the receiver 112, the distortion module 118, the beam generator 114 and the receive beamformer 116. In one embodiment, the memory module 122 may be a non-transitory computer readable mediums encoded with a program to instruct the image processor 120 to enable a sequence of steps to perform ultrasound imaging of deeper tissues. The program may further instruct the ultrasound system 100 to generate the diagnostic image 140 during scanning of the subject.
[0025] In one embodiment, the diagnostic image 140 may be a gray scale image with anatomical information of an organ of interest in the subject 128. In another embodiment, the diagnostic image 140 may include color flow image providing motion information of blood flowing within the organ of interest superimposed on the gray scale image. The diagnostic image 140 may be stored in a database with timestamp, patient data and other relevant metadata for future use. In one embodiment, the diagnostic image 140 is automatically processed for deriving at least one of prognosis, diagnosis and a treatment options and a recommended treatment plan. In one embodiment, the diagnostic image 140 140 is provided to a medical professional such as, but not limited to, a doctor, a radiologist or a paramedical personnel for review, treatment and diagnosis of a medical condition.
[0026] FIG. 2 is a graph 200 illustrating frequency shift characteristics exhibited by deeper tissues in accordance with an exemplary embodiment. The graph 200 includes an x-axis 202 representative of depth values from the surface of the subject at which the ultrasound signals are scattered. The graph 200 further includes a y-axis 204 representative of frequency attenuation experienced by the ultrasound signals during propagation through a subject 128. The graph 200 includes a first curve 206 representative of a frequency shift (or attenuation) as a function of depth values. A zero value of attenuation corresponds to a surface of the subject and negative values of attenuation (in kilo hertz) are representative of frequency shift of the scattered signal from the incident frequency of the ultrasound signal. The graph 200 includes a second curve 208 representative of frequency deviation with increasing depth values represented by a monotonously decreasing function.
[0027] FIG. 3 is a graph 300 illustrating frequency spectrum of a modified transmit beam in accordance with an exemplary embodiment. The graph 300 includes an x-axis 302 representative of frequency and a y-axis 304 is representative of amplitude of the frequency spectrum. The graph 300 includes a first curve 306 representative of a transmitted beam having a center frequency at five megahertz. The graph 300 further includes a second curve 310 representative of response signal corresponding to a specified depth in the subject. The graph includes a third curve 308 representative of a modified transmitted beam having a center frequency at 2.5mega hertz. The third curve 308 is generated based on a distortion parameter derived from the second curve 310. The third curve 308 representative of modified transmitted beam and the second curve 310 representative of response signal are used by the beamformer to generate the beamformed output. It may be noted that the center frequencies of the modified transmitted beam and the response signal overlap at around 2.5mega hertz. The beamformed output is based on the modified transmitted beam and the response signals, both having the same frequency band. The beamformed output having enhanced signal to noise ratio facilitates producing an ultrasound image of enhanced quality.
[0028] FIG.4 is a schematic flow diagram 400 illustrating a model based transmit beamforming in accordance with an exemplary embodiment. The model based transmit beamforming illustrated in the schematic flow diagram 400 is performed for every pixel among the plurality of pixels of an ultrasound image to be generated. The schematic flow diagram 400 includes a block 404 for generating an echo data model based on the plurality of response signals 402 obtained from the plurality of transducer elements.
[0029] In the illustrated embodiment, a distortion parameter is estimated based on the echo data model generated at block 404. The distortion parameter having parameters such as the frequency shift and the bandwidth value, is representative of distortions introduced by deeper tissues. Further, a modified transmitted pulse is generated in block 410 based on the distortion parameter generated in block 408.
[0030] In block 412, a transmit data model is generated based on the modified transmitted pulse. A beamformed output is determined at block 414 using the echo data matrix and the transmit data matrix, based on a model inversion. In one embodiment, the model inversion is implemented using a weighted least squares technique. Alternatively, any technique for solving a set of linear equations may be used to determine the beamformed output at block 414. In one embodiment, the echo data matrix may be determined based on the response signals processed by a dynamic filter. It may be noted that the dynamic filter may be designed based on the distortion parameter.
[0031] Further, at a decision block 418, a verification process is initiated to ensure if the beamformed output is generated for all the pixels of the image. If the beamformed output is available for all the pixels, the processing is terminated at block 422. Alternatively, if the beamformed output is not available for all the pixels, the processing for remaining pixels is continued as indicated by block 420. The processing indicated by blocks 404, 406, 408, 410, 412, 414, 416 is initiated for a new plurality of response signals corresponding to a new pixel.
[0032] FIG. 5A is an ultrasound image 500 obtained from conventional retrospective transmit beamforming in accordance with an exemplary embodiment. The ultrasound image 500 is a 2D image having a length dimension 508 and a width dimension 506, represented in millimeters units. The ultrasound image 500 is representative of a highly attenuating phantom with background attenuation of 1.76dB/cm/MHz. The image corresponds to fundamental mode with center frequency of 5MHz obtained by using a 9L linear probe focusing at a penetration depth of 3centi meters. The phantom includes a first cyst 510 of smaller dimension, having an attenuation of 1.01dB/cm/MHz and a second cyst 512 of relatively larger dimension, having an attenuation of 0.8dB/cm/MHz. The first cyst 510 and the second cyst 512 lack clarity with minimal details. Further, the bottom portion 506 of the image is dark illustrating high attenuation masking a bright stripe.
[0033] FIG. 5B is an ultrasound image 504 formed using methods of the present specification. In particular, the ultrasound image 504 is obtained from model based transmit beamforming disclosed herein in accordance with an exemplary embodiment. The ultrasound image 504 is a 2D image having a length 516 and a width dimensions 514, represented in millimeters units. The parameters used for generating the ultrasound image 504 are same as those used in the generation of the ultrasound image 500. The ultrasound image 504 includes a first smaller cyst 518 and a second bigger cyst 520 with enhanced resolution. The ultrasound image 504 further includes a stripe 518 in the highly attenuating region illustrating enhanced image generation from the model based transformed technique. The axial resolution along the length dimension 516 is significantly improved in the image 504. The model based transmit beamforming is able to compensate the frequency attenuation introduced by tissues at each depth value along the length dimension 516.
[0034] FIG. 6 is a flow chart illustrating a method 600 for ultrasound imaging of deeper tissues in a subject, in accordance with an exemplary embodiment. At step 602, the method 600 commences by receiving a plurality of response signals generated by the organ of the subject. The plurality of response signals is generated in response to a transmitted beam emitted from the plurality of transducer elements of an ultrasound scanner. In one embodiment, the method further includes processing the plurality of response signals by a dynamic filter for optimal processing and signal to noise improvement.
[0035] At step 604, a distortion parameter corresponding to a location in the organ is estimated based on the plurality of response signals. The distortion parameter comprises at least one of a frequency shift value and a bandwidth value corresponding to a transmitted pulse used to generate the transmitted beam. In one embodiment, the step of estimating the distortion parameter includes performing a correlation between at least one of the plurality of response signals with a reference response signal. In another embodiment, the step of estimating the distortion parameter is implemented using an auto regressive model.
[0036] The method 600 also includes generating a modified transmitted beam based on the distortion parameter as shown in step 606. The step of generating the modified transmitted beam includes generating a modified transmitted pulse based on the distortion parameter. The step of generating the modified transmitted beam further includes linearly combining a plurality of modified transmitted pulses delayed by a plurality of corresponding time delay values. In one embodiment, the modified transmitted pulse is generated by shifting a central frequency of the transmitted pulse by a frequency shift value. In another embodiment, the modified transmitted pulse includes limiting bandwidth of the transmitted pulse to the bandwidth value.
[0037] The method 600 further includes generating a beamformed output corresponding to the location of the organ based on the modified transmitted beam and the plurality of response signals as illustrated in step 608. The step of generating the beamformed output includes generating an echo data model based on the plurality of response signals. The step of generating the beamformed output further includes generating a transmit data model based on the modified transmitted beam. Moreover, the step of generating the beamformed output also includes determining a beamformed output based on the echo data model and the transmit data model. In one embodiment, the echo data model and the transmit data model are matrices having dimensions based on a sampling frequency, a transmit delay time and an imaging depth value. The matrix representative of the transmit data model includes samples from the modified transmitted beam. The matrix representative of the echo data model includes data samples from the plurality of response signals. In one embodiment, the beamformed output is determined using a weighted least squares technique.
[0038] At step 608 a plurality of beamformed outputs corresponding to a plurality of pixels in an image corresponding to the organ are generated based on respective plurality of response signals and a respective modified transmitted beam. The method 600 further includes generating a diagnostic image 140 corresponding to the subject based on the plurality of beamformed outputs as shown in step 610. The diagnostic image 140 includes a plurality of pixels representative of anatomical information corresponding to the plurality of locations in the organ of the subject under medical examination. Optionally, the method includes determining if a treatment plan is required for the subject. Additionally, if a treatment plan is required, the method may include determining a treatment plan for the subject based on the diagnostic image generated at step 610. The diagnostic image may be presented to a medical professional such as, but not limited to, a doctor and a radiologist for providing a treatment to the subject.
[0039] Disclosed embodiments of ultrasound image formation compensates for frequency shift due to propagation depth of the ultrasound signals. Traditional approaches of frequency compensation by estimating the frequency shift on the beamformed data is improvised in the disclosed embodiments by estimating (and compensating) the frequency shift from the plurality of response signals representative scattered ultrasound signals before beamforming. The disclosed frequency estimation technique is robust and facilitates efficient dynamic filtering. Use of modified transmitted beam based on the propagation depth improves axial resolution of the ultrasound image. The technique further helps in enhancing the quality of scanning among subjects who are overweight. Model based beam forming disclosed herein also helps in improvising the resolution of the ultrasound image.
[0040] It is to be understood that not necessarily all such objects or advantages described above may be achieved in accordance with any particular embodiment. Thus, for example, those skilled in the art will recognize that the systems and techniques described herein may be embodied or carried out in a manner that achieves or improves one advantage or group of advantages as taught herein without necessarily achieving other objects or advantages as may be taught or suggested herein.
[0041] While the technology has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the specification is not limited to such disclosed embodiments. Rather, the technology can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the claims. Additionally, while various embodiments of the technology have been described, it is to be understood that aspects of the specification may include only some of the described embodiments. Accordingly, the specification is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.