Patent Publication Number: US-2018052963-A1

Title: Ultrasound diagnostic device and ultrasound image display method

Description:
TECHNICAL FIELD 
     The present disclosure relates to an ultrasound diagnostic device, in particular, an ultrasound diagnostic device with use of a virtual keyboard. 
     BACKGROUND 
     An ultrasound diagnostic device forms an ultrasound image based on received signals by transmitting and receiving ultrasound waves to and from a living body. In ultrasound diagnostic devices, a patient ID, comments, and other data may be entered by using a hardware keyboard or a virtual keyboard (software keyboard) displayed on a display. 
     In an ultrasound system disclosed in Patent Literature 1, a keyboard image is displayed on a part of a display screen. 
     CITATION LIST 
     Patent Literature 
     
         
         Patent Literature 1: JP 2010-17558 A 
       
    
     SUMMARY 
     Technical Problem 
     Due to a limited size of a display screen, a virtual keyboard may overlap an ultrasound image depending on the size of the screen, causing an issue that because the ultrasound image is covered by the virtual keyboard, observation of the ultrasound image is disabled. In order to address this issue, the ultrasound image and the virtual keyboard may be reduced in size to be displayed to avoid the overlap of the ultrasound image and the virtual keyboard. However, this may cause another issue that the observation of the ultrasound image and an input operation using the keyboard become inconvenient. 
     An object of the present invention is to allow an input by using a virtual keyboard and an observation of an ultrasound image to be performed properly in an ultrasound diagnostic device. 
     Solution to Problem 
     An ultrasound diagnostic device according to the present disclosure includes a display that displays an ultrasound image formed based on a reception signal obtained by transmitting and receiving ultrasound waves; a display controller that performs control to display a virtual keyboard which can be transparently displayed on a display screen on which the ultrasound image is displayed; and a sensor that senses an input to the virtual keyboard on the display screen. 
     Because the virtual keyboard has transparency, when the virtual keyboard is displayed over an ultrasound image, the ultrasound image can be observed as a background image through the virtual keyboard. In this way, because it is unnecessary to reduce the size of the ultrasound image and the virtual keyboard to avoid an overlapping display of the virtual keyboard and the ultrasound image in a limited display area, it is possible to largely display each display element. Thus, an input operation can be properly performed through the virtual keyboard while properly observing the ultrasound image. It is also possible to avoid selecting and displaying each display element in the display area. 
     It is preferable that a degree of transparency of the virtual keyboard is variable. In this way, the degree of transparency of the virtual keyboard can be changed when necessary, to observe the ultrasound image or input to the virtual keyboard. 
     It is further preferable that the display controller shifts the virtual keyboard in the up direction or the down direction on the display screen in accordance with a shift instruction. For example, the virtual keyboard may be displayed by avoiding a region of interest on the ultrasound image. 
     It is further preferable that the display controller displays a button image on the display to shift the virtual keyboard in the up direction or the down direction. In this way, the display position of the virtual keyboard can be changed by a simple operation. 
     It is further preferable that when the degree of transparency of the virtual keyboard satisfies a predetermined condition, the sensor senses an input within a display area of the virtual keyboard as an input to a background image behind the virtual keyboard. In this way, an error input to the virtual keyboard can be prevented and the input is sensed as a valid input to the background image. 
     It is further preferable that the ultrasound diagnostic device further includes a distance sensor that senses a distance between the display and a user. The display controller changes the degree of transparency of the virtual keyboard in accordance with the sensed distance. In this way, the visibility of the virtual keyboard and the ultrasound image is changed in accordance with a user (observer) state. 
     It is further preferable that the display controller increases the degree of transparency of the virtual keyboard when the distance between the display and the user is larger, compared to the degree of transparency when the distance between the display and the user is smaller. In this way, when the user such as an observer approaches the display, the degree of transparency decreases, enhancing the visibility of the virtual keyboard. Conversely, when the user is farther away from the display, the degree of transparency increases, lowering the visibility of the virtual keyboard but enhancing the visibility of the ultrasound image. 
     It is further preferable that the display controller changes the display position of the virtual keyboard in accordance with the position of a point of interest or region of interest set for the ultrasound image. 
     A method for displaying an ultrasound image according to the present disclosure includes displaying an ultrasound image formed based on a reception signal obtained by transmitting and receiving ultrasound waves and performing control to display a virtual keyboard which can be transparently displayed on a display screen on which the ultrasound image is displayed; and sensing an input operation to the virtual keyboard on the display screen. 
     Advantageous Effects of Invention 
     According to the present disclosure, an input by using a virtual keyboard and an observation of an ultrasound image can be performed properly in an ultrasound diagnostic device. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a conceptual diagram showing a preferable embodiment of an ultrasound diagnostic system according to the present disclosure; 
         FIG. 2  is a perspective diagram of an ultrasound diagnostic system in a separated state; 
         FIG. 3  is a perspective diagram of an ultrasound diagnostic system in a docked state; 
         FIG. 4  is a block diagram of a front-end device; 
         FIG. 5  is a block diagram of a back-end device; 
         FIG. 6  is a table showing communication systems in a docked state and a separated state; 
         FIG. 7  is a block diagram showing a configuration for display control of a touch panel monitor; 
         FIG. 8  is a diagram showing a layered structure of images; 
         FIG. 9  is a diagram showing a first display example of a virtual keyboard; 
         FIG. 10  is a diagram showing a second display example of a virtual keyboard; 
         FIG. 11  is a diagram showing a second display example of a virtual keyboard; 
         FIG. 12  is a diagram showing a second display example of a virtual keyboard; 
         FIG. 13  is a diagram showing a second display example of a virtual keyboard; 
         FIG. 14A  is a diagram showing a third display example of a virtual keyboard; 
         FIG. 14B  is a diagram showing a third display example of a virtual keyboard; 
         FIG. 14C  is a diagram showing a third display example of a virtual keyboard; 
         FIG. 15A  is a diagram showing a fourth display example of a virtual keyboard; 
         FIG. 15B  is a diagram showing a fourth display example of a virtual keyboard; and 
         FIG. 16  is a diagram showing another configuration for display control of a touch panel monitor. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Preferred embodiments of the present disclosure are described below by referring to the drawings. 
     (1) Ultrasound Diagnostic System 
       FIG. 1  shows a schematic diagram of an ultrasound diagnostic system according to the present disclosure. An ultrasound diagnostic system  10  is a medical device used at medical facilities such as a hospital, to perform an ultrasound diagnosis to a subject (living body). The ultrasound diagnostic system  10  is configured with, roughly grouped, a front-end (FE) device  12 , a back-end (BE) device  14 , and a probe  16 . The FE device  12  is located near from the living body, whereas the BE device  14  is located far from the living body. The FE device  12  and the BE device  14  are separately-provided portable devices. The FE device  12  and the BE device  14  are operable in a separated state in which these devices are separated, and also operable in a docked state in which these devices are in the combined docked state.  FIG. 1  shows a separated state. 
     The probe  16  is a wave transceiver which transmits and receives ultrasound waves with the probe  16  in contact with a surface of a living body. The probe  16  includes 1D array transducer elements which are arranged in a linear or arch shaped line. The array transducer elements form ultrasound beams which are repeatedly electronically scanned. A beam scan plane is formed in a living body in each electronic scan. As an electronic scanning method, an electronic linear scanning method, an electronic sector scanning method, and other methods are known. In place of the 1D array transducer elements, 2D array transducer elements, which can form a three-dimensional echo data acquisition space, may be used. In the configuration shown in  FIG. 1 , the probe  16  is connected to the 1th device  12  via a cable  28 . The probe  16  may be connected to the FE device  12  through wireless communications. In that case, a wireless probe is used. By connecting two or more probes to the FE device  12 , the probe  16  which is to be actually used may be selected from the connected probes. The probe  16  which is to be inserted into a body cavity may be connected to the FE device  12 . 
     In the separated state shown in  FIG. 1 , the FE device  12  and the BE device  14  are electrically connected to each other through a wireless communication system. In this embodiment, these devices are connected to each other through a first wireless communication system and a second wireless communication system.  FIG. 1  clearly shows a wireless communication path  18  in the first wireless communication system and another wireless communication path  20  in the second wireless communication system. The first wireless communication system is faster than the second wireless communication system. In the present embodiment, the first wireless communication system is used to transmit ultrasound reception data from the FE device  12  to the BE device  14 . In other words, the first wireless communication system is used for data transmission. In the present embodiment, the second wireless communication system is slower and simpler than the first wireless communication system. The second wireless communication system is used to transmit control signals from the BE device  14  to the FE device  12 . In other words, the second wireless communication system is used for control. 
     In the docked state in which the FE device  12  and the BE device  14  are physically connected to each other, the FE device  12  and the BE device  14  are electrically connected through a wired communication system. The wired communication system is significantly faster than the above two wireless communication systems.  FIG. 1  shows a wired communication path  22  between the two devices. A power supply path  26  is used to supply DC electrical power from the FE device  12  to the BE device  14 . The supplied electrical power is used for operating the BE device  14  and for charging a battery in the BE device  14 . 
     Reference numeral  24  represents a DC power supply line from an AC adaptor (AC/DC converter). The AC adaptor is connected to the FE device  12 , if necessary. Because the FE device  12  has a built-in battery, the FE device  12  can operate by using the battery as a power source. The FE device  12  has a box-like shape as described below. The configuration and operations of the FE device  12  are described in detail below. 
     In contrast, the BE device  14  has a tablet-like or plate-like shape in the present embodiment. The BE device  14  basically has a configuration similar to a general tablet computer, except that the BE device  14  is mounted with various dedicated software for ultrasound diagnosis. Such software includes an operation control program, an image process program, and other programs. The BE device  14  includes a display panel  30  with a touch sensor. The display panel  30  functions as a user interface, serving both as an input device and a display. In  FIG. 1 , a B-mode tomographic image  32  is displayed on the display panel  30  as an ultrasound image. A user performs various inputs by using icons displayed on the display panel  30 . It is possible to perform a slide operation and a zoom-in operation on the display panel  30 . 
     The ultrasound diagnostic system  10  can be operated in a usage state selected from a separated state and a docked state, in accordance with a diagnostic application and the preference of a diagnostician. Therefore, a highly-usable ultrasound diagnostic system can be provided. 
     In order to avoid the ultrasound diagnostic system  10  becoming unstable or improper when the state is changed, the ultrasound diagnostic system  10  is controlled to be forced into a freeze state when the state is changed. Specifically, in a transaction process from the separated state to the docked state, an immediately-before-docked state is determined respectively in the FE device  12  and the BE device  14  based on the wave strength and the reception state, which are indicators of the distance between the two devices. Based on this determination, the FE device  12  and the BE device  14  are respectively controlled to switch the operation state to the freeze state. The freeze state of the FE device  12  and the BE device  14  is released after the docked state is achieved and the diagnostician has performed a freeze release operation. In a transition state from the docked state to the separated state, the separated state is detected respectively in the FE device  12  and the BE device  14  by detecting a pulled-out wire or by another method to place the devices in the freeze state. Then, the freeze state of the FE devices FE device  12  and  14  is released after the freeze release operation. 
     The BE device  14  may be separately connected to a hospital LAN by a wireless communication system or a wired communication system. Such a communication path is omitted in the drawing. The BE device  14  (or the FE device  12 ) may be separately connected to another dedicated device (such as a remote controller) used for ultrasound diagnosis by a wireless communication system or a wired communication system. 
       FIG. 2  shows a separated state. The FE device  12  may be placed, for example, on a desk. The FE device  12  includes a holder  34  which has an insertion port (slot). The holder  34  has a hinge mechanism such that the holder  34  is pivotable about a horizontal axis. On end of a probe cable is connected to a predetermined side of the FE device  12 . A chamber for accommodating a probe or other elements may be formed inside the FE device  12 . Such a structure is convenient when carrying the ultrasound diagnostic system, and the probe can be protected. In  FIG. 2 , the BE device  14  is separated from the FE device  12 . The BE device  14  may be further separated from the FE device  12  within a wirelessly communicable range. 
       FIG. 3  shows a docked state. A bottom edge portion of the BE device  14  is inserted into the insertion port of the holder  34 . In this inserted state, the FE device  12  and BE device  14  are in wired communication with each other. In other words, the devices are both connected through a wired LAN and a wired power supply line. In the docked state, the angle of the BE device  14  may be arbitrary changed to adjust the orientation. The BE device  14  may be tilted completely to the back surface side (to the upper surface side of the FE device  12 ). 
     (2) Front-End Device 
       FIG. 4  is a block diagram of the FE device  12 . The respective blocks in the drawing are configured with hardware such as processors and electronic circuits. A transmission signal generator circuit  38  supplies two or more transmission signals in parallel to two or more transducer elements in the probe. In response to the supplied signals, transmission beams are generated by the probe. When the two or more transducer elements receive reflected waves from inside a living body, received signals are output from those transducer elements such that the received signals are input to a received signal processing circuit  42  via a probe connection circuit  40 . The received signal processing circuit  42  includes preamplifiers, amplifiers, A/D converters, and other elements. Digital received signals which have been output from the received signal processing circuit  42  are sent to a received beam former  46 . The received beam former  46  applies a phase addition process to the digital received signals and outputs beam data as signals after the phase addition. The beam data are formed with two or more echo data items which correspond to the received beam and are arranged in the depth direction. Received frame data are formed with two or more beam data items which have been obtained in a single electronic scan. 
     A transmit/receive controller  44  controls generation of transmission signals and processing of received signals based on transmit/receive control data which have been sent from the BE device  14 . A beam processor  50  is a circuit which applies various data processing such as a detection process, a log conversion process, a correlation process etc., to respective beam data which are time-sequentially input. A controller  52  controls overall operations of the FE device  12 . Besides such controls, the controller  52  also performs controls for sending, to the BE device  14 , beam data which have been sequentially sent from the beam processor  50  either via cable or wirelessly. In the present embodiment, the controller  52  also functions as a wired communication device. A wireless communication device  54  is a module which communicates in a first wireless communication system. A wireless communication device  56  is another module which communicates in a second wireless communication system. Reference numeral  18  represents a wireless communication path in the first wireless communication system. Reference numeral  20  represents a wireless communication path in the second wireless communication system. Although the paths are both bidrectional communication paths, in the present embodiment, vast received data are transmitted from the FE device  12  to the BE device  14  by using the wireless communication path  18 , whereas control signals are transmitted from the BE device  14  to the FE device  12  by using the wireless communication path  20 . Reference numeral  64  represents a wired communication terminal to which the wired communication path  22  is connected. Reference numeral  66  represents a power supply terminal to which the power supply line  26  is connected. The power supply line  26  supplies DC power from the FE device  12  to the BE device  14  as described above. 
     A battery  60  may be, for example, a lithium ion type battery. The charge and discharge of the battery  60  are controlled by a power supply controller  58 . When the battery is in operation, electrical power from the battery  60  is supplied to each circuit in the FE device  12  via the power supply controller  58 . Reference numeral  62  represents a power supply line when an AC adaptor is connected. When the AC adaptor is connected, external electrical power is supplied to each circuit in the FE device  12  through the operation of the power supply controller  58 . During this process, when the charge amount of the battery  60  is below 100%, the battery  60  is charged by the external electrical power. 
     During an ultrasound diagnosis operation (during transmission and reception), the FE device  12  repeatedly supplies transmission signals to a probe and processes received signals which are subsequently received. The time-sequence beam data which are obtained by these repeated processes are sequentially transmitted to the BE device  14  through wireless communication in the separated state or through wired communication in the docked state. During this process, respective beam data are converted into packets such that respective beam data are transmitted in a so-called packet transmission system. 
     Besides the B mode, various modes are known as operation modes, including a CMF mode, an M mode, and D modes (a PW mode and a CW mode). Transmission/reception processes may be performed for harmonic imaging and elasticity information imaging. In  FIG. 4 , a circuit such as a living body signal input circuit is omitted. 
     (3) Back-End Device 
       FIG. 5  is a block diagram of the BE device  14 . In the drawing, each block indicates hardware such as a processor, a circuit, and a memory. A CPU block  68  includes a CPU  70  and an internal memory  72 . The internal memory  72  serves as a working memory or a cache memory. An external memory  80 , which is connected to the CPU block  68 , stores various types of programs such as an OS, control programs and processing programs. The processing programs include a scan convert processing program. The external memory  80  also serves as a cine memory having a ring buffer configuration. The cine memory may be formed in the internal memory  72 . 
     The CPU block  68  generates display frame data by a scan convert process based on two or more beam data items. The display frame data form an ultrasound image (for example, a tomographic image). The display frame data are sequentially processed to produce video. The CPU block  68  applies, to the beam data or images, various processes to display ultrasound images. Besides these processes, the CPU block  68  controls operations of the BE device  14  and the entire ultrasound diagnostic system. 
     A touch panel monitor (display panel)  78  serves as an input device and a display device. Specifically, the touch panel monitor  78  includes a liquid crystal display and a touch sensor to serve as a user interface. The touch panel monitor  78  displays images, including ultrasound images. A virtual keyboard (software keyboard) and various types of buttons (icons) for operations are also displayed. 
     A wireless communication device  74  is a module for wireless communications in the first wireless communication system. The wireless communication path for such communications is shown by reference numeral  18 . Another wireless communication device  76  is a module for wireless communications in the second wireless communication system. The wireless communication path for such communications is shown by reference numeral  20 . The CPU block  68  is also provided with a function for wired communications so as to communicate in accordance with a wired communication system. In a docked state, a wired communication line is connected to a wired communication terminal  92 . A power supply line  26  is connected to a power supply terminal  94 . 
     The CPU block  68  includes two or more sensors  84  to  90  connected thereto via an interface (I/F) circuit  82 . The sensors may include an illumination sensor, a proximity sensor, a temperature sensor, and a distance sensor. A module such as a GPS may be connected. The I/F circuit  82  serves as a sensor controller. 
     A battery  102  is a lithium ceramic type battery. The charge and discharge of the battery are controlled by a power supply controller  100 . The power supply controller  100  supplies electrical power from the battery  102  to the respective circuits in the BE device  14  when the battery is in operation. When the battery is not in operation, the power supply controller  100  supplies the electrical power from the FE device  12  or an AC adaptor to the respective circuits in the BE device  14 . Reference numeral  104  represents a power supply line via the AC adaptor. 
     The BE device  14  generates ultrasound images by sequentially processing the beam data fed from the FE device  12  while controlling the FE device  12  so as to display the generated ultrasound images on the touch panel monitor  78 . During this process, a graphic image used for operation is also displayed together with the ultrasound images. In a usual real-time operation, the BE device  14  and the FE device  12  are electrically connected to each other by a cable or wirelessly. The devices are synchronized while the ultrasound diagnostic operation is continuously performed. In a freeze state, operations of a transmission signal generation circuit and a reception signal generation circuit are stopped, and operations of a boost circuit in the power supply controller  100  are also stopped. In the BE device  14 , the display turns to a still-image display at the time of freezing to maintain the displayed image. The BE device  14  may be configured to be connectable with an external display. 
     (4) Communication Systems 
       FIG. 6  shows, in an organized manner, communication systems used in a docked state  118  and a separated state  120 . Reference numeral  110  represents a first wireless communication system, whereas reference numeral  112  represents a second wireless communication system. Reference numeral  114  represents a wired communication system. Reference numeral  116  represents descriptions of the wireless communication systems. In the docked state  118 , wired communication is selected such that the first wireless communication device and the second wireless communication device in the FE device  12  and the BE device  14  are placed in an operation stopped state. This can achieve energy saving. Conversely, in the separated state  120 , wireless communications are selected such that the first wireless communication device and the second wireless communication device are operated in the FE device  12  and the BE device  14 . During this process, the wired communication system is placed in an operation stopped state. It should be noted that the first wireless communication system  110  is faster than the second wireless communication system  112 . Conversely, the second wireless communication system  112  is slower than the first wireless communication system  110 , but the second wireless communication system  112  is simpler, less costly, and consumes less power. As the wired communication system, a TCP/IP protocol on Ethernet (registered trademark) is available. As the first wired communication system and the second wired communication system, IEEE 802.11 and IEEE 802.15.1 are respectively available. These communication systems are listed merely as examples. Other communication systems may be used. In either case, it is desirable to use a secured communication system. 
     In the present embodiment, the wireless communication device in the second wireless communication system  112  is provided with a function to automatically change the transmission power in accordance with a reception strength (in other words, distance). Specifically, when the FE device  12  is placed in the vicinity of the BE device  14 , control is automatically performed to reduce the transmission power of both of the devices. Therefore, it is possible to determine that the devices are placed in the vicinity of each other based on the set transmission power. Alternatively, it is also possible to determine that the two devices are placed in the vicinity of each other based on other factors such as the reception strength and reception error rate. Further, a proximity sensor may be used. In the above configuration, the BE device  14  itself serves as the ultrasound diagnostic device. A system in which the FE device  12  and the BE device  14  are combined also serves as the ultrasound diagnostic device. 
     (5) Virtual Keyboard 
     The BE device  14  is provided with a function to display a virtual keyboard. This function is described below. In the present embodiment, the virtual keyboard (software keyboard) is displayed on the touch panel monitor  78 , when necessary. The virtual keyboard is a keyboard which accepts an input from a user on the touch panel monitor  78 . 
       FIG. 7  shows a configuration of display control of a touch panel monitor. A display controller  130  displays ultrasound images, various buttons (icons) for operations, a virtual trackpad, a virtual keyboard, and others on the touch panel monitor  78 . For example, the display controller  130  displays the virtual keyboard in a display area where an ultrasound image is displayed on the touch panel monitor  78 . The data of this virtual keyboard are stored in advance in an internal memory  72  in a CPU block  68 , or in the external memory  80 . 
     The virtual keyboard according to the present embodiment is an image which can be transparently displayed with a variable degree of transparency. The degree of transparency is a variable value within a range from 0% to 100%. This degree of transparency may be set by a user or automatically. When the degree of transparency is set to “0%”, the display controller  130  displays the virtual keyboard in a completely-opaque state on the touch panel monitor  78 . In this case, it is impossible to view a background image through the virtual keyboard. Conversely, when the degree of transparency is set to “100%”, the virtual keyboard becomes completely transparent. In this case, it is impossible to view the virtual keyboard. A degree of transparency closer to “0%” makes the degree of transparency of the virtual keyboard closer to opaque, whereas a degree of transparency closer to “100%” makes the degree of transparency of the virtual keyboard closer to complete transparency. How the background image appears varies in accordance with the degree of transparency. 
     A sensor  132  is a touch sensor for sensing a touch operation (input) on the touch panel monitor  78 . As a sensing system of the touch panel monitor  78 , a well-known system can be applied. As a typical system, a capacitive system or a resistive film system may be used. The sensor  132  senses operations such as a drag operation in which a touch position is moved on the touch panel monitor  78  and a release operation in which the touch is detached from the touch panel monitor  78 . For example, the sensor  132  senses operations such as a touch operation and a drag operation on a virtual trackpad. The sensor  132  further senses touch operations on the various buttons. When the virtual keyboard is displayed on the touch panel monitor  78 , the sensor  132  senses touch operations on the virtual keyboard. The sensor  132  senses touch operations to respective elements on the virtual keyboard to accept input of text and instructions. 
     The display controller  130  and the sensor  132  may be provided as functions of, for example, the CPU block  68  in the BE device  14 . 
       FIG. 8  shows an example of a layer structure of images displayed on the touch panel monitor  78 . A layer structure  200  includes two or more overlapping layers (hierarchy). A layer  210  includes a virtual keyboard  212 . A layer  220  includes a button group  222  (icon group) for operation. A layer  230  includes an ultrasound image  232  (image such as a B-mode tomographic image). As an example, the layer  210  is the front layer, the layer  220  is the middle layer, and the layer  230  is the back layer. This arrangement is, of-course, only an example. The layers may be arranged in any other order. 
     For example, when a display instruction for the ultrasound image  232  is provided while no display instruction for the virtual keyboard  212  and the button group  222  is provided, the display controller  130  displays the layer  230  on the touch panel monitor  78 . In this way, the ultrasound image  232  is displayed on the touch panel monitor  78 . When a display instruction for the virtual keyboard  212  is provided in this state, the display controller  130  displays the layer  210  over the layer  230  on the touch panel monitor  78 . The ultrasound image  232  becomes a background image of the virtual keyboard  212 . When the display position of the ultrasound image  232  and the display position of the virtual keyboard  212  are overlapped, the images are displayed such that the virtual keyboard  212  overlaps the ultrasound image  232  at the overlapping portion. The display controller  130  sets the degree of transparency of the layer  210  as designated. In this way, the degree of transparency of the virtual keyboard  212  is set such that the degree of transparency changes how the ultrasound image  232  appears in the area overlapped with the virtual keyboard  212 . When the degree of transparency is set to “0%”, it is impossible to view the ultrasound image  232  in the overlapping portion. When the degree of transparency is set to “100%”, the virtual keyboard  212  becomes completely transparent such that it becomes possible to view the ultrasound image  232  while the virtual keyboard  212  is invisible. When the degree of transparency is set to a value between 0 and 100%, how the overlapping portion appears changes in accordance with the set value. 
     When display instructions for the ultrasound image  232  and the button group  222  are provided while no display instruction for the virtual keyboard  212  is provided, the display controller  130  displays the layer  220  over the layer  230  on the touch panel monitor  78 . In this way, the ultrasound image  232  and the button group  222  are displayed. When the display position of the ultrasound image  232  and the display position of the button group  222  are overlapped, the images are displayed such that the button group  222  overlaps the ultrasound image  232  at the overlapping portion. 
     When display instructions for the ultrasound image  232 , the virtual keyboard  212 , and the button group  222  are provided, the display controller  130  displays the layer  220  over the layer  230 , and the layer  210  over the layer  220  on the touch panel monitor  78 . 
     It should be noted that the layer structure  200  shown in  FIG. 8  is merely an example. One or more layers other than the layers  210  to  230  may be included in the layer structure  200 . 
     The virtual keyboard is described in detail below. 
     First Display Example 
     Referring to  FIG. 9 , the first display example of a virtual keyboard is described.  FIG. 9  shows a display area of the touch panel monitor  78  when inputting a patient ID. When inputting a patient ID, the display controller  130  displays a patient ID input field  140 , a patient name input field  142 , a patient birthday input field  144 , a gender selection field, and the like. When an input field is designated by a user (for example, by a touch operation) in this state, the display controller  130  displays the virtual keyboard  212  on the touch panel monitor  78 . In this way, an input of the patient ID or the like using the virtual keyboard  212  becomes possible. For example, the display controller  130  displays the virtual keyboard  212  in an area avoiding the display position of the input fields  140  to  144 . In the example shown in  FIG. 9 , because the input fields  140  to  144  are displayed in the upper portion in the display area, the virtual keyboard  212  is displayed in the lower portion in the display area. When the input fields  140  to  144  are displayed in the lower portion in the display area, the virtual keyboard  212  may be displayed in the upper portion in the display area. Because no image overlaps the virtual keyboard  212  when inputting the patient ID, the display controller  130  sets the degree of transparency of the virtual keyboard  212  to “0%”. In this way, the virtual keyboard  212  is displayed in a completely opaque state. The display controller  130  may, of course, display the virtual keyboard  212  at any position in accordance with an instruction from the user and sets the degree of transparency of the virtual keyboard  212  to a value designated by the user. 
     Second Display Example 
     Referring to  FIGS. 10 to 13 , the second display example of the virtual keyboard is described.  FIG. 10  shows a display area of the touch panel monitor  78  during an ultrasound diagnosis. During the ultrasound diagnosis, the display area of the touch panel monitor  78  includes display areas  78 A and  78 B. 
     The display area  78 A is an examination screen area, in which an ultrasound image  232  (for example, a B-mode tomographic image) is displayed. When a display instruction for the virtual keyboard  212  is provided, the virtual keyboard  212  is displayed in the display area  78 A. The virtual keyboard  212  is, for example, a so-called full keyboard provided with function keys and a numeric keypad. Of course, a keyboard without the function keys and numeric keypad may also be used for the virtual keyboard  212 . Further, the virtual keyboard  212  may include any keys dedicated for the ultrasound diagnosis. For example, up/down or diagonal arrow keys may be included in the virtual keyboard  212 . 
     The display area  78 B is an operation area (command area), in which a button group  240  (icon group) for inputting various commands and a virtual trackpad  242  are displayed. The button group  240  includes buttons such as a mode set button to set an ultrasound diagnosis mode, a freeze button to freeze the ultrasound image, a store button to store the ultrasound image, a gain adjustment button, and a comment input button to input comments. When a user performs a touch operation to any of the buttons, the touch operation is sensed by the sensor  132  (touch sensor) and a process corresponding to the button is performed. The virtual trackpad  242  enables, on a screen, operations similar to those of a trackpad (touchpad). By performing a drag operation on the virtual trackpad  242 , a pointer  246  displayed in the display area  78 A can be moved in the drag direction for the distance corresponding to the drag amount. Of course, the pointer  246  may be directly moved by performing the drag operation directly on the pointer  246 . A button group  244  is displayed around the virtual trackpad  242 . The button group  244  includes buttons corresponding to an “Enter key”, a “Cancel” key, and a “Select” key. 
     In the present embodiment, the virtual keyboard  212  is displayed in the display area  78 A, not in the display area  78 B, to avoid interference with the button group  240  displayed in the display area  78 B. 
     For example, when a user designates (for example, by a touch operation) the comment input field, the display controller  130  displays the virtual keyboard  212  in the display area  78 A of the touch panel monitor  78 . In this way, comments can be input through the virtual keyboard  212 . A hide button  214  is provided for the virtual keyboard  212 . When the user performs a touch operation on the hide button  214 , the display controller  130  hides the virtual keyboard  212 . Alternatively, the display controller  130  may hide the virtual keyboard  212  when a touch operation is performed in an area other than the virtual keyboard  212 . 
     In a default state, the virtual keyboard  212  is displayed, for example, in a lower area in the display area  78 A. The virtual keyboard  212  has a vertical length (length in the height direction) of, for example, less than half the vertical length of the display area  78 A. The virtual keyboard  212  is provided with an up/down shift button  216  for shifting the virtual keyboard  212  in the up or down direction (in the height direction). When the user performs a touch operation on the up/down shift button  216  with the virtual keyboard  212  being displayed in the lower area, the display controller  130  moves the virtual keyboard  212  in the up direction to display the virtual keyboard  212  in the upper area. Of course, the virtual keyboard  212  may be displayed in the upper area by default. 
     The virtual keyboard  212  is displayed in front of the ultrasound image  232  such that the virtual keyboard  212  partially overlaps with the ultrasound image  232 . The degree of transparency of the virtual keyboard  212  is set in accordance with a user instruction within a range from 0 to 100%. For example, the display controller  130  displays a transparency degree setting bar (not shown) for setting the degree of transparency from 0 to 100% on the touch panel monitor  78 . When the user designates the degree of transparency by a touch operation on the transparency degree setting bar, the display controller  130  sets the degree of transparency of the virtual keyboard  212  to the value designated by the user. In the example shown in  FIG. 10 , because the degree of transparency of the virtual keyboard  212  is set to “0%”, the virtual keyboard  212  is displayed in a completely opaque state. In this state, the user cannot view the overlapping portion of the ultrasound image  232  through the virtual keyboard  212 . 
     At the same time, an input to the virtual keyboard  212  becomes effective. For example, when a user performs a touch operation on the virtual keyboard  212 , the touch operation is sensed by the sensor  132  (touch sensor) such that texts and instructions are input. 
       FIG. 11  shows the virtual keyboard  212  which is displayed in a semitransparent state. For example, when the degree of transparency is set to a value between 0 to 100% (excluding 0 and 100%), the virtual keyboard  212  is displayed in a semitransparent state in accordance with the set degree of transparency. In such a state, the user can view the overlapping portion of the ultrasound image  232  through the virtual keyboard  212 . The portion indicated by a dashed-line arrow  232   a  in  FIG. 11  is the overlapping portion of the ultrasound image  232  and the virtual keyboard  212 . In this portion, because the ultrasound image  232  can be seen through the virtual keyboard  212 , the user can observe the portion. At the same time, an input to the virtual keyboard  212  becomes effective. For example, when a user performs a touch operation on the virtual keyboard  212 , the touch operation is sensed by the sensor  132  (touch sensor) such that text and instructions are input. In this way, the ultrasound image  232  can be sufficiently observed while a text input is possible through the virtual keyboard  212 . 
       FIGS. 12 and 13  shows the virtual keyboard  212  which is shown in the upper area. In the example shown in  FIG. 12 , because the degree of transparency of the virtual keyboard  212  is set to “0%”, the virtual keyboard  212  is displayed in a completely opaque state. In this state, the user cannot observe the overlapping portion of the ultrasound image  232  through the virtual keyboard  212 . 
     In the example shown in  FIG. 13 , the virtual keyboard  212  is displayed in a semitransparent state. In this state, the user can observe the overlapping portion of the ultrasound image  232  through the virtual keyboard  212 . The portion indicated by a dashed-line arrow  232   b  in  FIG. 13  is the overlapping portion of the ultrasound image  232  and the virtual keyboard  212 . In this portion, because the ultrasound image  232  can be viewed through the virtual keyboard  212 , the user can observe the portion. In this way, the ultrasound image  232  can be properly observed while a text input is possible through the virtual keyboard  212 . 
     When the user performs a touch operation on the up/down shift button  216  with the virtual keyboard  212  being displayed in the upper area, the display controller  130  moves the virtual keyboard  212  in the down direction to display the virtual keyboard  212  in the lower area. 
     For example, the virtual keyboard  212  can be shifted in the upper or lower direction to avoid the overlapping of the virtual keyboard  212  over the region of interest in the ultrasound image  232 . In this way, the region of interest can be directly observed, not through the virtual keyboard  212 . As described above, in the present embodiment, the vertical length of the virtual keyboard  212  is less than half the vertical length of the display area  78 A. Thus, because no overlapping portion exists between the upwardly-shifted virtual keyboard  212  and the downwardly-shifted virtual keyboard  212 , the region of interest can be directly observed, not through the virtual keyboard  212 , by shifting the virtual keyboard  212  in either direction. 
     Alternatively, the display controller  130  may display the virtual keyboard  212  in an intermediate area between the upper area and the lower area, or at any position in the vertical direction (height direction). 
     As described above, in the present embodiment, the display of the virtual keyboard  212  is limited to within the display area  78 A, and the movement of the virtual keyboard  212  is limited to the vertical direction. Of course, the virtual keyboard  212  may be configured to be moveable in the horizontal direction or a diagonal direction. For example, when the display area  78 A has a sufficiently large size, the virtual keyboard  212  may be configured to be moveable in any direction. It should be noted that a reduced or enlarged display of the virtual keyboard  212  may also be enabled. 
     As described above, in the present embodiment, the transparently-displayable virtual keyboard  212  is displayed. The transparency of the virtual keyboard  212  enables observation of the ultrasound image  232  through the virtual keyboard  212  when the virtual keyboard  212  is overlappingly displayed over the ultrasound image  232 . In this way, in a limited display area  78 A, reduction in the display size of the ultrasound image  232  and the virtual keyboard  212  in order to prevent the overlapping display of the ultrasound image  232  and the virtual keyboard  212  can be avoided, enabling display sizes to be made large. Thus, the ultrasound image  232  can be properly observed in a an enlarged state and the input operation can be properly performed by using the virtual keyboard  212  that is displayed enlarged. It becomes unnecessary to select and display the elements to be included in the virtual keyboard  212 . This is convenient because the virtual keyboard  212  corresponding to, for example, a full keyboard can be used. 
     Third Display Example 
     Referring to  FIGS. 14A, 14B, and 14C , the third display example of the virtual keyboard is described. In the third display example, in accordance with the degree of transparency, the sensor  132  (touch sensor) may not sense an input on the virtual keyboard, recognizing the input as an invalid input. Instead, the sensor  132  senses an input on the background image of the virtual keyboard as a valid input. 
     It is assumed here that the layer structure  200  shown in  FIG. 8  is applied. Specifically, it is assumed that the layer  220  including the button group  222  is disposed behind the layer  210  including the virtual keyboard  212 . Because the display position of the button group  222  and the display position of the virtual keyboard  212  are overlapped, when the layers  210  and  220  are overlappingly displayed, the virtual keyboard  212  is displayed over the button group  222 . 
       FIG. 14A  shows the virtual keyboard  212  in “0%” degree of transparency. This virtual keyboard  212  is displayed in the lower area in the display area  78 A. Although an ultrasound image is not displayed, for the sake of convenience of description, an ultrasound image is displayed in the display area  78 A as shown in  FIG. 10 . Because the degree of transparency is set to “0%”, the virtual keyboard  212  is displayed in a completely opaque state. Thus, the button group  222  behind the virtual keyboard  212  cannot be viewed. In this state, the sensor  132  (touch sensor) senses a touch operation on the virtual keyboard  212  as a valid key input to the virtual keyboard  212 . Thus, an input by using the virtual keyboard  212  is performed. 
     By increasing the degree of transparency of the virtual keyboard  212 , it becomes possible to view the button group  222  on the background through the virtual keyboard  212 . When the degree of the virtual keyboard  212  is set between “0%” and “100%” (excluding 0% and 100%), the virtual keyboard  212  and the button group  222  are displayed together and the button group  222  can be viewed through the virtual keyboard  212 . In this state, the sensor  132  senses a touch operation to the virtual keyboard  212  as a valid key input to the virtual keyboard  212 . In this way, an input using the virtual keyboard  212  is performed. In other words, the sensor  132  senses the touch operation to the overlapping portion of the virtual keyboard  212  and the button group  222  not as a valid input to the button group  222  but as a valid input to the virtual keyboard  212  which is displayed in front. 
     As the degree of the transparency of the virtual keyboard  212  is increased further to be set at 100% (maximum degree of transparency), the virtual keyboard  212  becomes completely transparent. In this case, as shown in  FIG. 14C , the virtual keyboard is not visible (for the sake of convenience of description,  FIG. 14C  shows the virtual keyboard  212  by a broken line). In the overlapping portion, the button group  222  alone is displayed as a background image. In this case, the sensor  132  does not sense a touch operation in the area in which the virtual keyboard  212  is disposed as a valid key input to the virtual keyboard  212 , but senses the input as a valid input to the button group  222  on the background. In this way, an input to the button group  222  is sensed as a valid input, even when the layer  210  including the virtual keyboard  212  is disposed in front of the layer  220  including the button group  222 . 
     As shown in  FIG. 8 , the layer  210  including the virtual keyboard  212  is disposed in front of the layer  220  including the button group  222 . Thus, without invalidating the input to the virtual keyboard  212 , a touch operation to the button group  222  would be sensed as a valid key input to the virtual keyboard  212  even when the virtual keyboard  212  is completely transparent and the button group  222  alone is displayed in the overlapping portion. When the virtual keyboard  212  is invisible while the button group  222  is visible, it can be assumed, based on a reasonable assumption of the user&#39;s intention, that a touch operation to the button group  222  (overlapping portion) is intended to an input operation to the button group  222 . If the touch operation to the button group  222  were sensed as a valid input to the virtual keyboard  212 , an erroneous input to the keyboard would be caused. In contrast, according to the third display example, the touch operation to the button group  222  is sensed not as a key input to the virtual keyboard  212  but as a valid input to the button group  222 . In this way, an erroneous input to the keyboard can be prevented and a proper input to the button group  222  is enabled. 
     Further, even with the degree of transparency of the virtual keyboard  212  set to a value other than “100%”, the sensor  132  may sense the touch operation not as a valid key input to the virtual keyboard  212  but as a valid input to the button group  222  when the degree of transparency of the virtual keyboard  212  is equal to or higher than a reference value. The reference value is, for example, a predetermined value and can be varied by a user. 
     Fourth Display Example 
     Referring to  FIGS. 15A and 15B , the fourth display example of a virtual keyboard is described. In the fourth display example, the display position of the virtual keyboard is changed depending on the position of a point of interest which is set for an ultrasound image (for example, a sample volume used in a Doppler measurement) and the position of a region of interest (ROI). 
     When a user provides instructions to set a region of interest, the display controller  130  displays a region of interest  234  on the ultrasound image  232 , for example, as shown in  FIG. 15A . The display position, shape, and size of the region of interest  234  are designated by, for example, a user. In the example shown in  FIG. 15A , the region of interest  234  is displayed in the upper area in the display area  78 A. In this case, the display controller  130  displays the virtual keyboard  212  in the lower area in the display area  78 A. When the region of interest  234  is displayed in the lower area in the display area  78 A in accordance with instructions from the user, the display controller  130  displays the virtual keyboard  212  in the upper area in the display area  78 A. As such, the vertical position of the virtual keyboard  212  is selected in accordance with the vertical position (in the height direction) of the region of interest  234 . In a case where a sample volume is set on the ultrasound image  232 , the vertical position of the virtual keyboard  212  is selected in accordance with the vertical position of the sample volume. 
     In accordance with the fourth display example, the virtual keyboard  212  is displayed by automatically avoiding the display position of the region of interest or the sample volume. In this way, the region of interest and the sample volume become more visible for the user, and the settings of these elements are facilitated. 
     It should be noted that the display controller  130  may display the virtual keyboard  212  in an intermediate area between the upper area and the lower area by avoiding the display position of the region of interest and the sample volume, or at any position in the vertical direction (height direction). 
     Other Configuration Examples for Display Control 
     Referring to  FIG. 16 , another configuration for display control of a touch panel monitor is described. In this example, a distance sensor  134  is used. The distance sensor  134  is disposed, for example, in the vicinity of the touch panel monitor  78  of the BE device  14  for sensing the distance between the touch panel monitor  78  and the user (observer). The sensed values are output to the display controller  130 . For the distance sensor  134 , a sensor such as an optical sensor, an ultrasound sensor, and a magnetic sensor, may be used. 
     The display controller  130  changes the degree of transparency of the virtual keyboard  212  in accordance with the sensed value (the distance between the touch panel monitor  78  and the user) from the distance sensor  134 . For example, the display controller  130  sets a lower degree of transparency of the virtual keyboard  212  for a shorter distance between the virtual keyboard  212  and the user. In this way, the visibility of the virtual keyboard  212  can be enhanced. Conversely, the display controller  130  sets a higher degree of transparency of the virtual keyboard  212  for a longer distance between the touch panel monitor  78  and the user. In this way, the visibility of the ultrasound image can be enhanced. Specifically, the degree of transparency decreases the closer the user is to the touch panel monitor  78 , whereas the degree of transparency increases the farther away the user is from the touch panel monitor  78 . For example, the display controller  130  may change the degree of transparency of the virtual keyboard  212  stepwise in accordance with the distance between the touch panel monitor  78  and the user (for example, the degrees of transparency are divided into two or more groups and switched stepwise). Alternatively, the display controller  130  may set the degree of transparency of the virtual keyboard  212  to a first degree of transparency when the distance between the touch panel monitor  78  and the user is equal to or below a predetermined value, and set the degree of transparency to a second degree of transparency, which is larger than the first degree of transparency, when the distance is above the predetermined value. In accordance with the distance, two degrees of transparency can be switched in this manner, or three or more degrees of transparency can be switched stepwise. 
     As described above, display control depending on user (observer) status becomes possible by changing the degree of transparency of the virtual keyboard  212  in accordance with the distance between the touch panel monitor  78  and the user. In other words, because the user status is assumed in accordance with the distance between the touch panel monitor  78  and the user, the display control depending on the user status becomes possible. 
     In yet another example, when an error message such as battery low is displayed, the display controller  130  may place a higher priority to display the error message than the virtual keyboard  212 . In this case, even when the virtual keyboard  212  is displayed on the touch panel monitor  78 , the display controller  130  displays the error message in front of the virtual keyboard  212 . When the display position of the virtual keyboard  212  and the display position of the error message are overlapped, the error message is displayed over the virtual keyboard  212 . Further, unless an operation to hide the error message is performed, the sensor  132  may not sense the touch operation to the virtual keyboard  212  as a valid key input. 
     REFERENCE NUMERALS 
       10  ultrasound diagnostic system,  12  FE device,  14  BE device,  78  touch panel monitor,  130  display controller,  132  sensor,  134  distance sensor,  212  virtual keyboard,  222  button group, and  232  ultrasound image.