JP4664209B2 - Ultrasonic diagnostic apparatus and ultrasonic imaging program for performing imaging thereof - Google Patents

Description

The present invention relates to an apparatus that captures an ultrasound image as a diagnostic image of a subject, and an ultrasound imaging program that executes the imaging .

  The ultrasonic diagnostic apparatus transmits and receives an ultrasonic beam to and from a subject using an ultrasonic probe, reconstructs an ultrasonic image based on a reception signal output from the ultrasonic probe, and is reconstructed. Display the ultrasonic elephant on the display screen. Here, the ultrasonic beam is formed with a focal point by ultrasonic waves transmitted or received from a plurality of transducers arranged on the ultrasonic probe.

  By the way, the reflected echo generated from the subject is attenuated in the process of propagating through the subject. The image quality of the ultrasonic image affected by the attenuation is deteriorated, for example, a signal as diagnostic information is buried in noise. Therefore, the image quality of an ultrasonic image is improved by setting correction data exponentially as a function of the depth of the subject and correcting the received signal based on the set correction data ( For example, see Patent Document 1).

Japanese Patent Laid-Open No. 4-40945

  However, the image quality of the ultrasonic image displayed by the ultrasonic diagnostic apparatus is affected by factors other than the depth of the subject. Therefore, in the method as disclosed in Patent Document 1 for correcting as a function of the depth of the subject, for example, an ultrasonic image in which a signal as diagnostic information is buried in noise or an ultrasonic image with degraded image contrast is displayed. Problems may still arise and there is room for improvement in improving the image quality of ultrasound images.

An object of the present invention is to realize an ultrasonic diagnostic apparatus more suitable for improving the image quality of an ultrasonic image and an ultrasonic imaging program for executing the imaging .

  The ultrasonic diagnostic apparatus of the present invention outputs an ultrasonic probe that transmits and receives ultrasonic waves to and from a subject, a transmission unit that supplies a drive signal to the ultrasonic probe, and an output from the ultrasonic probe. Receiving means for processing the received signal, and display means for displaying an ultrasonic image based on the received signal output from the receiving means, and the beam shape of the ultrasonic beam transmitted and received by the ultrasonic probe According to the present invention, there is provided means for correcting the reception signal output from the receiving means in accordance with the depth of the specimen.

  That is, at least one of the ultrasonic transmission beam and the ultrasonic reception beam has a beam shape determined by various factors such as the position of the focal point and the number of transducers forming the aperture of the ultrasonic probe. Come. Such an ultrasonic beam is narrowed down from the aperture to the focal point and has a shape that spreads beyond the focal point. Moreover, since attenuation occurs according to the propagation distance, a difference occurs in sound pressure or reflection intensity depending on the depth of each reflection part. For example, since an ultrasonic beam has a different beam cross-sectional area in the depth direction of the subject, the beam intensity is different in the depth direction of the subject. Due to this, the reception signal output from the ultrasonic probe is influenced by both the shape of the ultrasonic beam and the depth of the subject.

  Therefore, by performing correction corresponding to the shape of the ultrasonic beam and the depth of the subject on the reception signal output from the receiving means, the corrected received signal is converted into the shape of the ultrasonic beam and the depth of the subject. This is a signal in which the influence of is reduced. By displaying an ultrasonic image based on such a received signal, the image quality of the ultrasonic image can be improved.

  In short, paying attention to the fact that the shape of the ultrasonic beam differs in the depth direction of the subject, correcting the received signal according to the ultrasonic beam shape and the depth of the subject makes the subject appear more faithfully. Ultrasonic image can be displayed.

  In this case, as the correcting means, dynamic range correction for correcting the dynamic range of the reception signal output from the receiving means based on the dynamic range calculated corresponding to the beam shape of the ultrasonic beam and the depth of the subject. Means can be used. Further, instead of or together with the dynamic range correction means, the signal intensity of the reception signal output from the reception means is calculated based on the beam intensity calculated corresponding to the beam shape of the ultrasonic beam and the depth of the subject. It is possible to use signal intensity correction means for correction.

  The receiving means may have means for converting a received signal output from the ultrasound probe into a digital signal based on a sampling clock. The correction means in this case can correct the received signal output from the conversion means for each of one or more sampling points set in the depth direction of the subject based on the sampling clock.

  Further, the correction means can have a calculation means for calculating correction data. The calculation means includes at least one of the frequency of the drive signal, the wave number of the drive signal, the coordinates of the focal point of the ultrasonic beam, the number of transducers forming the aperture of the ultrasonic probe, and the focus data for forming the ultrasonic beam. Correction data can be calculated based on parameters including the two.

  Further, the correction means can have a calculation means for calculating correction data. The calculation means calculates one correction data corresponding to the beam shape of one ultrasonic beam and the depth of the subject, and while receiving a reception signal corresponding to one ultrasonic beam, Other correction data can be calculated corresponding to the beam shape of another ultrasonic beam different from the ultrasonic beam and the depth of the subject.

  As for the display means, the dynamic range calculated corresponding to the beam shape of the ultrasonic beam can be displayed as a graph as a function of the depth of the subject. Further, the beam intensity calculated corresponding to the beam shape of the ultrasonic beam can be displayed as a graph as a function of the depth of the subject.

An ultrasonic imaging program for executing imaging of the present invention by a computer includes a step of calculating correction data corresponding to a beam shape of an ultrasonic beam formed by an ultrasonic probe and a depth of an object, and an ultrasonic probe. A step of supplying a driving signal to the probe and transmitting an ultrasonic wave from the ultrasonic probe to the subject, and a receiving step of processing a reception signal output from the ultrasonic probe in response to the transmission step And a step of correcting the reception signal output from the reception step based on the correction data, and a step of displaying an ultrasonic image based on the reception signal output from the correction step.

  In this case, in the correction data calculation step, a dynamic range corresponding to the beam shape of the ultrasonic beam and the depth of the subject can be calculated. In the correction step in this case, the dynamic range of the reception signal output from the reception step can be corrected based on the dynamic range calculated in the correction data calculation step.

  In the correction data calculation step, the beam intensity corresponding to the beam shape of the ultrasonic beam and the depth of the subject can be calculated. In the correction process in this case, the signal intensity of the reception signal output from the reception process can be corrected based on the beam intensity calculated in the correction data calculation process.

  In the correction data calculation step, correction data corresponding to the beam shape of at least one of the ultrasonic transmission beam and the ultrasonic wave reception beam can be calculated.

  In the reception process, the reception signal output from the ultrasound probe can be converted into a digital signal based on the sampling clock. In the correction step in this case, the reception signal output from the reception step can be corrected for each of one or more sampling points set in the depth direction of the subject based on the sampling clock.

  In the correction data calculation step, the frequency of the drive signal, the wave number of the drive signal, the coordinates of the focal point of the ultrasonic beam, the number of transducers forming the aperture of the ultrasonic probe, and the focus for forming the ultrasonic beam Correction data can be calculated based on a parameter including at least one of the data.

  Further, in the correction data calculation step, a step of calculating one correction data corresponding to the beam shape of one ultrasonic beam and the depth of the subject, and a reception signal corresponding to one ultrasonic beam are received and processed. In the meantime, a step of calculating other correction data corresponding to the beam shape of another ultrasonic beam different from the one ultrasonic beam and the depth of the subject can be included.

  In the display step, the dynamic range calculated corresponding to the beam shape of the ultrasonic beam can be displayed as a graph as a function of the depth of the subject. Also, the beam intensity calculated corresponding to the beam shape of the ultrasonic beam can be displayed as a graph as a function of the depth of the subject.

1 is a block diagram showing a configuration of an ultrasonic diagnostic apparatus according to a first embodiment to which the present invention is applied. 2 is a flowchart showing an overall process of the ultrasonic diagnostic apparatus in FIG. 1. It is a conceptual diagram for demonstrating operation | movement of the dynamic range correction | amendment part of FIG. It is the comparative example imaged with the example of a display of the ultrasonic image imaged with the ultrasonic diagnostic apparatus of FIG. 1, and the apparatus of the reference form. It is a figure explaining that the beam shape of an ultrasonic beam differs in the depth direction. It is a block diagram which shows the structure of the ultrasonic diagnosing device of 2nd Embodiment to which this invention is applied. It is a flowchart which shows the whole process of the ultrasonic diagnosing device of FIG. It is a conceptual diagram for demonstrating operation | movement of the signal strength correction | amendment part of FIG. It is a block diagram which shows the structure of the ultrasonic diagnosing device of 3rd Embodiment to which this invention is applied. It is a flowchart which shows the whole process of the ultrasonic diagnosing device of FIG. It is a conceptual diagram for demonstrating operation | movement of the correction | amendment part of FIG.

(First embodiment)
A first embodiment of an ultrasonic diagnostic apparatus to which the present invention is applied will be described with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the ultrasonic diagnostic apparatus 1 of the present embodiment.

  As shown in FIG. 1, the ultrasound diagnostic apparatus 1 includes an ultrasound probe 10 that transmits and receives ultrasound to and from a subject, and transmission as a transmission unit that supplies a drive signal to the ultrasound probe 10. The circuit 12 and reception means for processing a reception signal output from the ultrasonic probe 10 are configured. The receiving means here includes a receiving circuit 16 that performs processing such as amplification on the received signal output from the ultrasound probe 10, and converts the received signal output from the receiving circuit 16 into a digital signal based on the sampling clock. An analog-to-digital conversion unit 18 (hereinafter referred to as A / D conversion unit 18), and a phasing addition unit as software phasing addition means for performing phasing addition processing on the received signal output from the A / D conversion unit 18 20 and a signal processing unit 22 that performs processing such as detection on the reception signal output from the phasing addition unit 20.

  The ultrasonic diagnostic apparatus 1 according to the present invention is based on the correction data calculated in correlation with the beam shape of the ultrasonic beam transmitted and received by the ultrasonic probe 10 and the depth of the subject, and the signal processing unit 22. A dynamic range correction unit 24 is provided as means for correcting the reception signal output from. The ultrasonic beam in the present embodiment means an ultrasonic transmission beam and an ultrasonic reception beam, but either one may be used.

  The configuration of the ultrasonic diagnostic apparatus 1 will be described in more detail. The ultrasonic probe 10 is formed by arranging a plurality of transducers. Each transducer converts a drive signal supplied from the transmission circuit 12 into an ultrasonic wave and converts a reflected echo generated from the subject into a reception signal. The drive signal here is a pulse signal for ultrasonic transmission.

  The transmission circuit 12 is provided in the transmission / reception unit 26 together with the reception circuit 16. The transmission / reception unit 26 outputs a drive signal output from the transmission circuit 12 to the ultrasonic probe 10 and a transmission / reception separation circuit that outputs a reception signal output from the ultrasonic probe 10 to the reception circuit 16; It has a high voltage changeover switch for selecting a group of transducers that form the transmission aperture or the reception aperture of the ultrasonic probe 10.

  The reception circuit 16 includes a reception amplifier that amplifies the reception signal output from the ultrasonic probe 10. The reception amplifier includes a preamplifier that amplifies the reception signal with a predetermined signal amplification degree, and a gain control amplifier that changes the signal amplification degree according to the attenuation of the reflected echo caused by the depth of the reflection part of the ultrasonic wave. By such processing of the receiving circuit 16, the received signal is amplified to a size sufficient for diagnosis and attenuation in the subject is corrected.

  A focus position determination unit 28 is connected to the transmission / reception unit 26. The focus position determination unit 28 outputs the set coordinates of the focal point of the ultrasonic transmission beam to the transmission / reception unit 26. Note that a keyboard or a mouse for inputting the coordinates of the focal point may be provided in the focus position determination unit 28.

  The A / D converter 18 includes a clock generator that generates a sampling clock. The sampling clock intervals here may be equal intervals or unequal intervals. The phasing addition unit 20 stores a delay amount correction unit 34 for digitally phasing the reception signal output from the A / D conversion unit 18 based on focus data, and focus data provided to the delay amount correction unit 34. The memory 36 and an adder 38 that adds the received signals for each channel output from the delay amount corrector 34 and outputs the added signals to the signal processor 22. Such a phasing addition unit 20 forms an ultrasonic wave reception beam.

  The signal processing unit 22 performs functions such as detection, filtering, and logarithmic compression on the reception signal output from the phasing addition unit 20, and an ultrasonic image (for example, B mode) based on the processed reception signal. Image, Doppler image, M-mode image). The image signal output from the signal processing unit 22 is output to the dynamic range correction unit 24. For convenience, the image signal output from the signal processing unit 22 is also referred to as a received signal as appropriate.

  The dynamic range correction unit 24 includes a dynamic range calculation unit 40 and a memory 42. First, the dynamic range calculation unit 40 calculates a dynamic range (hereinafter referred to as a correction dynamic range) as correction data correlated with the beam shape of the ultrasonic beam transmitted and received by the ultrasonic probe 10 and the depth of the subject. It has the function to do. For example, the frequency of the drive signal, the wave number of the drive signal, the coordinates of the focal point of the ultrasonic transmission beam or the ultrasonic reception beam, the size of the aperture of the ultrasonic probe 10, the ultrasonic transmission beam or the reception beam A dynamic range for correction is calculated based on a parameter including at least one of focus data for forming. Here, the size of the aperture is obtained based on the number of transducers forming the transmission aperture or the reception aperture and the size of each transducer. Then, the dynamic range calculation unit 40 arranges the correction dynamic ranges in the dynamic range table. The dynamic range table is a database in which dynamic ranges for correction are arranged corresponding to the depth of the subject (for example, the sampling point or the depth of the focus stage). In other words, the dynamic range table has an ultrasonic beam profile as a function of focus depth. Such a dynamic range table is stored in the memory 42.

  In addition, the dynamic range calculation unit 40 corrects the dynamic range of the reception signal output from the signal processing unit 22 based on the correction dynamic range. For example, the reception signal output from the signal processing unit 22 is corrected for each sampling point set in the depth direction of the subject based on the sampling clock of the A / D conversion unit 18. Here, instead of correcting the received signal for each sampling point, the received signal may be corrected for each focus stage having a plurality of sampling points.

  Such a dynamic range correction unit 24 calculates a first correction dynamic range based on the beam shape of the first ultrasonic beam and the depth of the subject, and a received signal corresponding to the first ultrasonic beam is obtained. During the reception process, the second correction dynamic range can be calculated based on the beam shape of the second ultrasonic beam different from the first ultrasonic beam and the depth of the subject. That is, the dynamic range calculation unit 40 can calculate the correction dynamic range in advance by time division processing. Alternatively, the correction dynamic range corresponding to the preset ultrasonic beam shape can be stored in the dynamic range table 42 in advance.

  In addition, the reception signal after correction output from the dynamic range correction unit 24 is converted into a display signal, and the digital scan converter 30 (hereinafter referred to as DSC 30) for performing luminance matching processing on the reception signal is output from the DSC 30. A display unit 32 for displaying an ultrasonic image based on the received signal on the display screen is provided.

  The basic operation of the ultrasonic diagnostic apparatus 1 configured as described above will be described. First, the ultrasonic probe 10 is brought into contact with the subject. When a drive signal is supplied to the ultrasonic probe 10 from the transmission circuit 12, an ultrasonic wave transmission beam is irradiated from the ultrasonic probe 10 to the subject. A reflection echo generated from the subject is received by the ultrasonic probe 10 and converted into a reception signal. The received signal is amplified by the receiving circuit 16. The amplified received signal is converted into a digital signal by the A / D converter 18. The digitized reception signal is formed as an ultrasonic wave reception beam by the phasing addition unit 20. The ultrasonic reception beam output from the phasing addition unit 20 is output as an image signal by being subjected to predetermined processing by the signal processing unit 22. The dynamic range of the image signal output from the signal processing unit 22 is corrected by the dynamic range correction unit 24. The corrected image signal is displayed as an ultrasonic image on the display unit 32 via the DSC 30.

  Here, the detailed operation of the ultrasonic diagnostic apparatus 1 will be described with reference to FIGS. 2 and 3 focusing on the dynamic range correction unit 24. FIG. FIG. 2 is a flowchart showing the overall processing of the ultrasonic diagnostic apparatus 1 of FIG. FIG. 3 is a conceptual diagram for explaining the operation of the dynamic range correction unit of FIG. Note that FIG. 3 shows the process in one focus stage for convenience, but the process in the other focus stages is the same.

<Compensation Dynamic Range Calculation Step (S100)>
The dynamic range for correction D1 to D6 is calculated by the dynamic range calculator 40. Here, the dynamic ranges for correction D1 to D6 are correction data correlated with the beam shape of the ultrasonic beam formed by the ultrasonic probe 10 and the depth of each of the reflection portions 46-1 to 46-7. As shown in FIG. 3A, since the reflection part 46-1 and the reflection part 46-6 have the same depth, both correspond to the correction dynamic range D1.

  More specifically, the dynamic range calculation unit 40 calculates the correction dynamic ranges D1 to D6 from factors related to the beam shape of the ultrasonic beam. Factors include the frequency of the drive signal supplied from the transmission circuit 12, the wave number of the drive signal, the coordinates of the focal point of the ultrasonic beam, the number of transducers forming the aperture of the ultrasonic probe 10, the phasing method, and the like. Parameter. The phasing method is transmission focus data for delaying the drive signal and reception focus data for phasing the reception signal (for example, focus data stored in the memory 36).

  That is, a general formula for setting the correction dynamic ranges D1 to D6 is expressed as the following formula 1. Thereby, for example, when the transmission / reception focus is shown in Table 1, the dynamic range is set as shown in the table.

要するに、補正用ダイナミックレンジＤ１〜Ｄ６は、超音波ビームが有する固有のダイナミックレンジであり、各反射部位４６−１〜４６−７におけるビーム強度に依存したものである。このような補正用ダイナミックレンジＤ１〜Ｄ６は、サンプリング点又はフォーカス段の深度に対応付けられた後、ダイナミックレンジテーブルとしてメモリ４２に格納される。図３Ｃは、受信信号Ｓ１〜Ｓ６に対応した補正用ダイナミックレンジＤ１〜Ｄ６を示している。なお、補正用ダイナミックレンジＤ１〜Ｄ６については、実測やシミュレーションなどから求めてもよい。

In short, the correction dynamic ranges D1 to D6 are inherent dynamic ranges of the ultrasonic beam and depend on the beam intensity at each of the reflection portions 46-1 to 46-7. Such correction dynamic ranges D1 to D6 are stored in the memory 42 as a dynamic range table after being associated with the sampling point or the depth of the focus stage. FIG. 3C shows correction dynamic ranges D1 to D6 corresponding to the reception signals S1 to S6. The correction dynamic ranges D1 to D6 may be obtained from actual measurement or simulation.

<Ultrasonic wave transmission process (S101)>
A drive signal is supplied to the ultrasonic probe 10 to transmit ultrasonic waves from the ultrasonic probe 10 to the subject. For example, a drive signal is supplied from the transmission circuit 12 to the ultrasonic probe 10 brought into contact with the body surface of the subject. A plurality of drive signals are generated corresponding to the number of transducers included in the ultrasound probe 10, and each generated drive signal is delayed using transmission focus data based on the focal position. Yes. The focus position is output from the focus position determination unit 28 to the transmission / reception unit 26 at a predetermined timing.

  On the other hand, among the plurality of transducer groups included in the ultrasound probe 10, a predetermined transducer group is selected by the high-voltage changeover switch, thereby forming a transmission aperture. When a drive signal is supplied to the transducer group having the transmission aperture, an ultrasonic wave is transmitted from each of the supplied transducers. An ultrasonic transmission beam is formed by each transmitted ultrasonic wave. The formed ultrasonic transmission beam has a focal point at a predetermined distance in the transmission direction.

  More specific description will be given with reference to FIG. 3A. The vertical axis in FIG. 3A indicates the depth of the subject, and the horizontal axis indicates the beam scanning address. As shown in FIG. 3A, a plurality of reflection sites 46-1 to 46-7 are scattered on the subject. Each reflection part 46-1 to 46-7 is different in size and acoustic impedance. Further, the reflection portions 46-1 to 46-7 have different depths except for the reflection portion 46-6. The reflection part 46-6 has the same depth as the reflection part 46-1.

  When this process is started, the beam address of the ultrasound probe 10 is initialized to the address A shown in FIG. 3A. Then, an ultrasonic transmission beam is emitted from the ultrasonic probe 10. That is, the ultrasonic transmission beam is sequentially emitted from the address A to the reflection portions 46-1 to 46-7 while changing the address in the scanning direction. FIG. 3A shows a two-dimensional distribution in the depth direction and the scanning direction, but the same applies to a three-dimensional distribution. Further, the focal position of the ultrasonic transmission beam can be changed as appropriate.

<Ultrasonic wave receiving step (S102)>
Corresponding to the ultrasonic wave transmission step (S101), the reception signal output from the ultrasonic probe 10 is processed. For example, reflection echoes generated from the reflection portions 46-1 to 46-7 are received by the ultrasonic probe 10 and converted into reception signals. The converted reception signal is sequentially processed by the reception circuit 16, the A / D conversion unit 18, and the phasing addition unit 20, thereby forming an ultrasonic wave reception beam. The formed ultrasonic wave reception beam has a focal point at a predetermined depth of the subject. Then, the ultrasonic reception beam is processed by the signal processing unit 22 and then output to the dynamic range correction unit 24 as reception signals S1 to S6 as shown in FIG. 3B. Note that the vertical axis in FIG. 3B indicates the depth of the subject, and the horizontal axis indicates the signal intensity. The signal strengths of the reception signals S1 to S6 correspond to, for example, luminance information when an image signal is formed.

  For convenience of explanation, in FIG. 3B, the signal strengths of the reception signals S1 to S6 are shown as projected for each depth. In addition, although the reflection part 46-1 and the reflection part 46-6 have the same depth, the signal intensity of the reception signal corresponding to the reflection part 46-1 is larger, so that the reception signal corresponding to the reflection part 46-1 is changed. The received signal S1.

<Reception Signal Correction Step (S103)>
The reception signals S1 to S6 output from the ultrasonic wave reception step (S102) are corrected based on the correction dynamic range. For example, the received signal S <b> 1 is input to the dynamic range correction unit 24. In response to the input of the received signal S1, the dynamic range calculation unit 40 reads the correction dynamic range D1 from the memory 42. The dynamic range for correction D1 is arranged in the dynamic range table, and is extracted from the dynamic range table corresponding to the depth of the reflection part 46-1. The received signal S1 has its signal intensity corrected by the dynamic range calculator 40 based on the correction dynamic range D1. The same applies to the reflection portions 46-2 to 46-7. The corrected received signals DN1 to DN6 processed in this way are shown in FIG. 3D. In short, by this step, the received signals DN1 to DN6 become signals in consideration of the inherent dynamic range of the ultrasonic beam.

  The correction calculation in this step is performed based on, for example, Equation 2. K in Equation 2 indicates the number of received signals to be corrected. The value of k in this embodiment is 1 to 6, but may be changed as appropriate. α represents a coefficient for correcting the signal intensity attenuated when the reflected echo propagates through the subject.

＜超音波像の表示工程（Ｓ１０４）＞
補正工程（Ｓ１０３）から出力される受信信号ＤＮ１〜ＤＮ６に基づいた超音波像が表示画面に表示される。例えば、受信信号ＤＮ１〜ＤＮ６は、ＤＳＣ３０により表示用の信号に変換されると共に、輝度合わせ処理が施される。ＤＳＣ３０から出力される受信信号ＤＮ１〜ＤＮ６は、超音波像として表示部３２の表示画面に表示される。また、補正用ダイナミックレンジＤ１〜Ｄ６は、反射部位４６−１〜４６−７の深度の関数として超音波像と並べてグラフ表示される。グラフ表示により、補正用ダイナミックレンジＤ１〜Ｄ６が視覚的に把握される。

<Ultrasonic image display step (S104)>
An ultrasonic image based on the reception signals DN1 to DN6 output from the correction step (S103) is displayed on the display screen. For example, the received signals DN1 to DN6 are converted into display signals by the DSC 30 and subjected to luminance matching processing. The reception signals DN1 to DN6 output from the DSC 30 are displayed on the display screen of the display unit 32 as an ultrasonic image. The correction dynamic ranges D1 to D6 are displayed in a graph alongside the ultrasonic image as a function of the depth of the reflection portions 46-1 to 46-7. The correction dynamic ranges D1 to D6 are visually grasped by the graph display.

  As described above, the ultrasonic wave transmission beam or the ultrasonic wave reception beam is narrowed down from the aperture to the focal point, and has a shape that spreads beyond the focal point. In addition, since attenuation corresponding to the propagation distance occurs, a difference occurs in sound pressure or reflection intensity depending on the depth of each of the reflection portions 46-1 to 46-7. For example, since an ultrasonic beam has a different beam cross-sectional area in the depth direction of the subject, the beam intensity is different in the depth direction of the subject. Due to this, the reception signal output from the signal processing unit 22 is influenced by both the shape of the ultrasonic beam and the depth of the reflection portions 46-1 to 46-7.

  Therefore, the reception signals S1 to S6 output from the signal processing unit 22 are corrected in correlation with the shape of the ultrasonic beam and the depth of the reflection portions 46-1 to 46-7. Thereby, the corrected reception signals DN1 to DN6 are signals in which the influence of the shape of the ultrasonic beam and the depth of the reflection portions 46-1 to 46-7 is reduced. By displaying an ultrasonic image based on such received signals DN1 to DN6, the image quality of the ultrasonic image can be improved.

  FIG. 4A is a display example of an ultrasonic image obtained by phantom imaging by the ultrasonic diagnostic apparatus of this embodiment. FIG. 4B is a display example of an ultrasonic image obtained by phantom imaging with the ultrasonic diagnostic apparatus according to the reference embodiment.

  In the ultrasonic diagnostic apparatus according to the reference embodiment, the dynamic range when displaying the ultrasonic image is set to be constant (for example, 100 dB) regardless of the depth of the reflection part. In general, a reflected echo generated from a reflection part having a shallow depth has a high signal intensity, whereas a reflection echo generated from a reflection part having a deep depth has a low signal intensity due to attenuation in the subject. Therefore, when the display is performed according to the dynamic range of the reception signal corresponding to the shallow reflection part, the contrast of the image corresponding to the deep reflection part may be lowered. In addition, when the display is performed according to the dynamic range of the reception signal corresponding to the deep reflection part, the image corresponding to the shallow reflection part may be saturated in luminance and information may be lost.

  In the case of FIG. 4B, the ultrasonic beam having the widest dynamic range at each depth of the reflection part is used as a reference. In other words, since a dynamic range capable of expressing all the received signals is set, the received signal is displayed wider than the dynamic range originally possessed. As a result, as shown in FIG. 4B, unnecessary components are displayed as noise on the ultrasonic image.

  In this regard, in the present embodiment, the dynamic range of the received signal is set in correlation with the beam shape of the ultrasonic beam. That is, an ultrasonic image faithful to the dynamic range of the ultrasonic beam at each depth of the reflection portions 46-1 to 47-7 is displayed. Therefore, compared with FIG. 4B, the ultrasonic image shown in FIG. 4A has no missing signal as diagnostic information and has reduced unnecessary components that become noise. Such an effect becomes more prominent particularly in a portion where the inherent dynamic range of the ultrasonic beam is narrowed. For example, this is conspicuous in a shallow portion when beam forming is performed using a variable aperture.

  That is, according to the present embodiment, the corrected received signals DN1 to DN6 are weighted with a function corresponding to the inherent dynamic ranges D1 to D6 of the ultrasonic beam. Based on such corrected reception signals DN1 to DN6, a dynamic range for displaying an ultrasonic image is set for each depth. Therefore, the ultrasonic image displayed on the display unit 32 has a reduced noise component and more faithfully represents the difference in acoustic impedance of the reflection portions 46-1 to 46-7.

  In short, the present embodiment is made by paying attention to the fact that the ultrasonic beam shape changes in the depth direction of the subject. That is, the ultrasonic beam shape changes in the depth direction of the subject depending on the focal position of the ultrasonic transmission beam, the size of the transmission aperture, the size of the reception aperture, the phasing method of the ultrasonic reception beam, and the like. . Therefore, the ultrasonic beam intensity (the size of the sound field) varies depending on the depth direction. When the ultrasonic beam shape is different in the depth direction, the dynamic range of the ultrasonic beam is changed accordingly. In this regard, according to the present embodiment, the image quality of the ultrasonic image can be improved by appropriately setting the dynamic range of the image signal in the depth direction of the subject in correlation with the ultrasonic beam.

  Further, the dynamic range of the received signal may have a relatively wide width, for example, exceeding 70 dB. In this regard, according to the present embodiment, the dynamic range when displayed as an ultrasonic image is set for each depth of the reflection region in correlation with the ultrasonic beam shape. As a result, even when the dynamic range of the received signal has a relatively wide width, a minute noise signal becomes apparent in the image, the luminance difference between pixels becomes small, or diagnostic information regarding the reflection site is lost. Can be suppressed.

  Furthermore, it is common that the shape of the ultrasonic beam changes from time to time with changes in the focal position of the ultrasonic beam, the phasing method, and the like. In this regard, according to the present embodiment, the dynamic range table is automatically updated by the dynamic range calculation unit 40 following the change of the ultrasonic beam shape. Therefore, usability and operability of the device are improved.

  Although the present invention has been described with reference to the first embodiment, the present invention is not limited to this. For example, the correction processing shown in FIG. 2 may be executed in beam address units or in frame units. When executed in units of frames, as described with reference to FIG. 3A, when there are a plurality of reflection parts (for example, reflection parts 46-1 and 46-6) at the same depth, the intensity of the received signal is large. It should be based on the direction. Further, the present invention can be applied not only to capturing a B-mode image (tomographic image) but also to capturing a Doppler image or an M-mode image.

  In addition, the received signal input to the dynamic range correction unit 24 is an output signal of the signal processing unit 22, but instead, it may be an intermediate signal of the signal processing unit 22 or an output signal of the phasing addition unit 20. However, the output signal of the A / D converter 18 may be used. In short, the reception signal output from the receiving means may be output to the dynamic range correction unit 24.

  The dynamic range of the transmission / reception system circuit of the ultrasonic diagnostic apparatus 1 is desirably wider than the inherent dynamic range of the ultrasonic beam transmitted and received by the ultrasonic probe 10.

<Supplementary information on ultrasonic beam shape>
A supplementary description will be given of an example in which the beam shape of the ultrasonic beam is different in the depth direction of the subject. FIG. 5A is a conceptual diagram of a plurality of sampling points T1 to TP (P: a natural number of 2 or more) set in the depth direction of the subject. FIG. 5B is a diagram illustrating a beam shape of a reception beam formed at each of the focus stages A to D. FIG. 5C is a diagram showing a beam shape of the ultrasonic transmission beam.

  As shown in FIG. 5A, a plurality of sampling points T1 to TP are set in the depth direction of the subject. The intervals between the sampling points T1 to TP are set to be equal to the sampling clock interval of the A / D conversion unit 18. The plurality of sampling points T1 to TP are divided into focus stages A to D, for example, every four points. For example, the sampling points T1 to T4 belong to the focus stage A. Note that the number of sampling points belonging to one focus stage is appropriately determined within a range that does not interfere with diagnosis.

  Common focus data is set for each of the focus stages A to D. The set focus data is stored in the memory 36. The focus data for reception is a delay amount or a minute delay amount for phasing each reception signal output from each transducer of the ultrasonic probe 10, and is switched for each focus stage A to D. The focus data stored in the memory 36 is read according to the control command. Based on the read focus data, the received signal output from the A / D converter 18 is delayed and phased by the phasing adder 20. Thereby, ultrasonic receiving beams corresponding to the respective sampling points T1 to TP are formed. In short, so-called dynamic focus is performed. Dynamic focusing is a method of focusing a beam in a relatively wide range in the depth direction by having several focal points from a shallow part to a deep part.

  As the focus data here, independent focus data is set for each of the focus stages A to D within a range that does not affect the diagnosis. Thereby, the total number of focus data can be reduced and the storage area of the memory 36 can be used more effectively than when setting every sampling point T1 to TP.

  As described above, because the focus data is different for each of the focus stages A to D, the beam shape (beam profile) of the ultrasonic reception beam is different in the depth direction of the subject. For example, FIG. 5B shows, in order from the top, the received beam shape corresponding to the sampling point T1 belonging to the focus stage A, the received beam shape corresponding to the sampling point T5 belonging to the focus stage B, and the sampling point T belonging to the focus stage C. The received beam shape corresponding to (P-8) and the received beam shape corresponding to the sampling point T (P-4) belonging to the focus stage D are shown. As can be seen from FIG. 5B, the ultrasonic wave reception beam has a different beam shape in the depth direction of the subject.

  In addition, since the depth is slightly different between a plurality of sampling points (for example, sampling points T1 to T4) belonging to the same focus stage (for example, focus stage A), the beam of the ultrasonic reception beam at each sampling point. The shape is also slightly different.

  Further, the beam shape of the ultrasonic receiving beam varies in the depth direction even when the variable aperture is performed. The variable aperture is a method of automatically decreasing the aperture width as it becomes shallower. With the variable aperture, it is possible to suppress the spread of reflected echoes generated from sampling points (for example, sampling points T1 and T2) close to the ultrasound probe 10. When such a variable aperture is used, the size of the aperture for receiving the reflected echo, that is, the number of elements of the vibrator forming the receive aperture is changed. Therefore, the beam shape of the ultrasonic reception beam differs in the depth direction.

  Furthermore, the beam shape of the ultrasonic transmission beam is different in the depth direction. For example, as shown in FIG. 5C, the ultrasonic transmission beam is formed by reducing the focal point to one point. In other words, the ultrasonic transmission beam is narrowed down from the ultrasonic probe 10 to the focal point 41, and has a shape that expands after exceeding the focal point. When the frame rate is not required, an ultrasonic transmission beam having a focus set for each of the focus stages A to D may be formed independently and transmitted multiple times.

  As described above, the beam shape of the ultrasonic wave transmission beam or the ultrasonic wave reception beam differs in the depth direction of the subject. Therefore, due to the ultrasonic beam intensity being different in the depth direction, the inherent dynamic range of the ultrasonic beam is also different in the depth direction. For example, the intrinsic dynamic range of the ultrasonic beam becomes wide at a depth where the ultrasonic beam intensity is large. The intrinsic dynamic range becomes narrow at the depth where the ultrasonic beam intensity is small. In order to reduce the influence of the shape of the ultrasonic beam and the depth of the subject, the present embodiment is based on the dynamic range calculated in correlation with the beam shape of the ultrasonic beam and the depth of the subject. The dynamic range of the received signal output from the processing unit 22 is corrected.

(Second Embodiment)
A second embodiment of an ultrasonic diagnostic apparatus to which the present invention is applied will be described with reference to FIGS. This embodiment is different from the first embodiment in that the reception signal output from the signal processing unit 22 is corrected based on the beam intensity calculated in correlation with the beam shape of the ultrasonic beam and the depth of the subject. . Accordingly, portions corresponding to those of the first embodiment are denoted by the same reference numerals, and the differences will be mainly described.

  FIG. 6 is a block diagram showing a configuration of the ultrasonic diagnostic apparatus 2 of the present embodiment. As shown in FIG. 2, the ultrasonic diagnostic apparatus 2 includes a signal intensity correction unit 50 instead of the dynamic range correction unit 24 of the first embodiment (for example, FIG. 1). The signal intensity correction unit 50 receives from the signal processing unit 22 based on the ultrasonic beam calculated in correlation with the beam shape of the ultrasonic beam transmitted and received by the ultrasonic probe 10 and the depth of the subject. Correct the signal strength of the signal. For example, the signal strength correction unit 50 includes a signal strength calculation unit 52 and a memory 54. The signal intensity calculation unit 52 calculates beam intensity as correction data correlated with the beam shape of the ultrasonic beam and the depth of the subject (hereinafter referred to as correction beam intensity as appropriate), and outputs a signal based on the correction beam intensity. The signal strength of the reception signal output from the processing unit 22 is corrected. The memory 54 stores a beam intensity table in which correction beam intensities are arranged as a function of the depth of the subject (for example, the sampling point or the depth of the focus stage).

  FIG. 7 is a flowchart showing the overall processing of the ultrasonic diagnostic apparatus 2 of FIG. FIG. 8 is a conceptual diagram for explaining the operation of the signal intensity correction unit 50 of FIG. As shown in FIG. 7, the present embodiment includes a correction beam intensity calculation step S200 instead of the correction dynamic range calculation step S100 of the first embodiment, and replaces the received signal correction step S103. , A received signal correction step S203 is provided. Therefore, the correction beam intensity calculation step S200 and the received signal correction step S203 will be mainly described.

<Correction Beam Intensity Calculation Step (S200)>
Correction beam intensities A1 to A4 are calculated by the signal intensity calculator 52. The correction beam intensities A1 to A4 are correction data correlated with the beam shape of the ultrasonic beam formed by the ultrasonic probe 10 and the depths of the reflection portions 46-1 to 46-7. For example, as shown in FIG. 8C, the beam intensity A1 corresponds to the beam intensity at the focal position of the ultrasonic beam. The beam intensity A2 corresponds to the reflection portions 46-4 and 46-5. The beam intensity A3 corresponds to the reflection portions 46-2 and 46-7. The beam intensity A4 corresponds to the reflection portions 46-1, 46-3, and 46-6.

  For example, the signal intensity calculation unit 52 calculates correction beam intensities A1 to A4 from factors related to the beam shape of the ultrasonic beam. The factors here are the frequency of the drive signal supplied from the transmission circuit 12, the wave number of the drive signal, the coordinates of the focal point of the ultrasonic beam, the number of transducers forming the aperture of the ultrasonic probe 10, Parameters such as phase method. The phasing method is determined by transmission focus data for delaying the drive signal and reception focus data for phasing the reception signal (for example, focus data stored in the memory 36). In short, the correction beam intensities A1 to A4 are signal intensities inherent to the ultrasonic beam. The correction beam intensities A1 to A4 are stored in the memory 54 as a beam intensity table after being associated with the sampling point or the depth of the focus stage.

  Regarding the calculation process in this step, for example, the correction beam intensity is calculated based on the beam shape of the first ultrasonic beam and the depth of the subject, and the reception signal corresponding to the first ultrasonic beam is received and processed. In the meantime, the correction beam intensity may be calculated in advance based on the beam shape of the second ultrasonic beam different from the first ultrasonic beam and the depth of the subject. Further, the correction beam intensities A1 to A4 may be obtained from actual measurement or simulation.

<Received Signal Correction Step (S203)>
The reception signals S1 to S6 output from the ultrasonic wave reception step (S102) are corrected based on the correction beam intensities A1 to A4. For example, when the received signals S 1 to S 6 are input to the signal intensity correction unit 50, the correction beam intensities A 1 to A 4 are read from the memory 54 by the signal intensity calculation unit 52. Of the correction beam intensities A1 to A4, the correction beam intensity A1 is set as the reference intensity. Note that the reference correction beam intensity may be changed as appropriate.

  Next, for example, when correcting the signal intensity of the received signal S1, a relative ratio (for example, A1 / A4) between the correction beam intensity A1 as the reference intensity and the correction beam intensity A4 is obtained. The obtained relative ratio corresponds to the amplitude ratio between the beam amplitude at the focal position of the ultrasonic beam and the beam amplitude at the depth of the reflection portion 46-1. Such a relative ratio is set as a correction coefficient.

  Then, as shown in FIG. 8D, the signal strength of the reception signal S1 is corrected by multiplying the signal strength of the reception signal S1 by a correction coefficient (A1 / A4). Similar processing is performed on the received signals S2 to S6. In short, the reception signals S1 to S6 are corrected as reception signals B1 to B6 by this process. The corrected received signals B1 to B6 are signals that take into account the inherent beam intensity of the ultrasonic beam.

  In general, an ultrasonic image is obtained by imaging the difference in acoustic impedance of reflection parts (for example, reflection parts 46-1 to 46-7) scattered in the depth direction of a subject. Therefore, if the ultrasonic beam has a uniform beam intensity (sound field) in the depth direction, the difference in acoustic impedance of each reflection portion is displayed as it is in the ultrasonic image. However, as described in the first embodiment, the beam intensity of the ultrasonic beam differs in the depth direction in correlation with the beam shape. As a result, the displayed ultrasonic image includes an error due to the intensity distribution in the depth direction of the transmitted beam.

  In this regard, according to the present embodiment, the corrected received signals B1 to B6 are signals whose signal intensity is corrected based on the intensity distribution in the depth direction of the ultrasonic beam. That is, the reception signals B1 to B6 after correction are equivalent to the reception signals when the beam intensity distribution in the depth direction of the ultrasonic beam is uniform.

  Therefore, by displaying the ultrasonic image based on the corrected received signals B1 to B6, the difference in acoustic impedance of the reflection portions 46-1 to 46-7 can be more faithfully displayed in the ultrasonic image. For example, the reflective part that should be displayed brightly is not displayed slightly dark, or the reflective part that should be displayed dark is not displayed slightly brighter. Can be displayed.

(Third embodiment)
A third embodiment of an ultrasonic diagnostic apparatus to which the present invention is applied will be described with reference to FIGS. In this embodiment, the received signal output from the signal processing unit 22 is corrected in the second embodiment as the first stage correction, and then corrected in the first embodiment as the second stage correction. , Different from the first and second embodiments. Accordingly, portions corresponding to those in the first and second embodiments are denoted by the same reference numerals, and description will be made focusing on the differences.

  FIG. 9 is a block diagram showing a configuration of the ultrasonic diagnostic apparatus 3 of the present embodiment. As shown in FIG. 9, the ultrasonic diagnostic apparatus 3 includes a dynamic range calculation unit 40 according to the first embodiment (for example, FIG. 1), a signal intensity calculation unit 52 according to the second embodiment (for example, FIG. 2), And a correction unit 56 including a memory 58. The memory 58 here stores a dynamic range table for correction and a beam intensity table for correction.

  Such a correction unit 56 correlates correction data (for example, correction beam intensities A1 to A4, correction dynamic range, etc.) in correlation with the beam shape of the ultrasonic beam transmitted and received by the ultrasonic probe 10 and the depth of the subject. D1 to D6) are calculated, and the received signal output from the signal processing unit 22 is corrected based on the calculated correction data and output to the DSC 30.

  FIG. 10 is a flowchart showing the overall processing of the ultrasonic diagnostic apparatus 3 of FIG. FIG. 11 is a conceptual diagram for explaining the operation of the correction unit 56 of FIG. As shown in FIG. 10, the correction data calculation process of the present embodiment includes the correction dynamic range calculation process S100 of the first embodiment (eg, FIG. 2) and the correction of the second embodiment (eg, FIG. 7). A beam intensity calculating step S200 is provided. For example, in the correction data calculation step, the correction dynamic ranges D1 to D6 are calculated and stored in the memory 58 as dynamic range tables, and the correction beam intensities A1 to A4 are calculated and stored in the memory 58 as signal intensity tables.

  The step of correcting the received signal includes a received signal correcting step S203 of the second embodiment and a received signal correcting step S103 of the first embodiment. For example, as shown in FIG. 11, the received signals S1 to S6 output from the signal processing unit 22 are subjected to the first stage correction using the corrected beam intensities A1 to A4, so that the received signals B1 to B6 are converted into the received signals B1 to B6. Become. Thereafter, the received signals B1 to B6 become the received signals DN1 to DN6 after the second stage correction by performing the second stage correction using the corrected dynamic ranges D1 to D6.

  In other words, the received signals S1 to S6 output from the signal processing unit 22 are subjected to the first-stage and second-stage corrections correlated with the shape of the ultrasonic beam and the depth of the subject, thereby correcting the received signals. DN1 to DN6 are signals in which the influence of the shape of the ultrasonic beam and the depth of the subject is further reduced. By displaying such an ultrasonic image based on the received signals DN1 to DN6, the image quality of the ultrasonic image can be further improved.

  The present invention has been described with reference to the first to third embodiments. In short, as a means for correcting the reception signal output from the signal processing unit 22, a dynamic range correction unit 24, a signal intensity correction unit 50, and a correction unit. At least one of 56 may be provided.

  The present invention can be implemented in various other forms without departing from the spirit or main features thereof. Therefore, the above-mentioned embodiment is only a mere illustration in all points, and is not interpreted limitedly. The scope of the present invention includes modifications and changes belonging to the equivalent range.

Claims (9)

An ultrasonic probe that transmits and receives ultrasonic waves to and from the subject, a transmission unit that supplies a drive signal to the ultrasonic probe, and a reception that processes a reception signal output from the ultrasonic probe And an ultrasonic diagnostic apparatus comprising display means for displaying an ultrasonic image based on the reception signal output from the reception means,
Wherein in response to an ultrasonic probe in beam shape and the subject depth of the ultrasound beam is transmitted and received, have a correcting means for correcting the reception signal outputted from said receiving means,
The correction means has calculation means for calculating correction data for correcting the received signal,
The calculation means calculates one correction data corresponding to the beam shape of one ultrasonic beam and the depth of the subject, and a reception signal corresponding to the one ultrasonic beam is received and processed. In the meantime, another correction data corresponding to the beam shape of the other ultrasonic beam different from the one ultrasonic beam and the depth of the subject is calculated .   The ultrasonic diagnostic apparatus according to claim 1, wherein the correction unit is output from the reception unit based on a dynamic range calculated corresponding to a beam shape of the ultrasonic beam and a depth of the subject. An ultrasonic diagnostic apparatus comprising dynamic range correction means for correcting a dynamic range of a received signal.   The ultrasonic diagnostic apparatus according to claim 1, wherein the correction unit is output from the reception unit based on a beam intensity calculated corresponding to a beam shape of the ultrasonic beam and a depth of the subject. An ultrasonic diagnostic apparatus comprising signal intensity correction means for correcting the signal intensity of a received signal. The ultrasonic diagnostic apparatus according to claim 1, wherein the correction means, the correction data is calculated corresponding to at least one of the beam shape of the ultrasonic transmission beam or ultrasonic receiving beam by said calculating means, the correction An ultrasonic diagnostic apparatus, wherein the received signal is corrected based on data. The ultrasonic diagnostic apparatus according to claim 1, wherein the reception unit includes a unit that converts a reception signal output from the ultrasonic probe into a digital signal based on a sampling clock,
The correction means, the correction data is calculated for each one or more sampling points set in the depth direction of the subject on the basis of the sampling clock by said calculating means, the said reception signal outputted from said receiving means An ultrasonic diagnostic apparatus that performs correction based on correction data . The ultrasonic diagnostic apparatus according to claim 1, before Symbol calculating means, the frequency of the drive signal, the wave number of the drive signal, the focus coordinates of the ultrasonic beam, to form the aperture of the ultrasonic probe An ultrasonic diagnostic apparatus, wherein the correction data is calculated based on a parameter including at least one of the number of transducers and focus data for forming the ultrasonic beam.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the display means displays a dynamic range calculated corresponding to a beam shape of the ultrasonic beam as a function of a depth of the subject. Ultrasound diagnostic device.   2. The ultrasonic diagnostic apparatus according to claim 1, wherein the display means displays a graph of the beam intensity calculated corresponding to the beam shape of the ultrasonic beam as a function of the depth of the subject. Ultrasound diagnostic device. Calculating correction data corresponding to the beam shape of the ultrasonic beam formed by the ultrasonic probe and the depth of the subject;
Supplying a driving signal to the ultrasonic probe to transmit ultrasonic waves from the ultrasonic probe to the subject;
A reception step of processing a reception signal output from the ultrasonic probe in response to the transmission step;
Correcting the reception signal output from the reception step based on the correction data;
Displaying an ultrasonic image based on the received signal output from the correction step ,
The step of calculating the correction data includes the step of calculating the correction data corresponding to the beam shape of the ultrasonic beam and the depth of the subject, and the reception corresponding to the ultrasonic beam. A step of calculating other correction data corresponding to a beam shape of another ultrasonic beam different from the one ultrasonic beam and a depth of the subject while a signal is received and processed; An ultrasonic imaging program causing a computer to execute each of the steps .

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