Patent Publication Number: US-11638572-B2

Title: Methods and apparatus for performing measurements on an ultrasound image

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit under 35 U.S.C. § 119(e) of U.S. Patent Application Ser. No. 62/750,348, filed Oct. 25, 2018, and entitled “METHODS AND APPARATUS FOR PERFORMING MEASUREMENTS ON AN ULTRASOUND IMAGE”, which is hereby incorporated herein by reference in its entirety. 
    
    
     FIELD 
     Generally, the aspects of the technology described herein relate to ultrasound data collection and analysis. 
     BACKGROUND 
     Ultrasound systems may be used to perform diagnostic imaging and/or treatment sound waves with frequencies that are higher with respect to those audible to humans. Ultrasound imaging may be used to see internal soft tissue body structures, for example to find a source of disease or to exclude any pathology. When pulses of ultrasound are transmitted into tissue (e.g., by using a pulser in an ultrasound imaging device), sound waves are reflected off the tissue, with different tissues reflecting varying degrees of sound. These reflected sound waves may then be recorded and displayed as an ultrasound image to the operator. The strength (amplitude) of the sound signal and the time it takes for the wave to travel through the body provide information used to produce the ultrasound image. Many different types of images can be formed using ultrasound systems, including real-time images. For example, images can be generated that show two-dimensional cross-sections of tissue, blood flow, motion of tissue over time, the location of blood, the presence of specific molecules, the stiffness of tissue, or the anatomy of a three-dimensional region. 
     SUMMARY 
     According to one aspect, a method includes displaying, on a touch-sensitive display screen of a processing device in operative communication with an ultrasound device: an ultrasound image, a movable measurement tool, and an icon that maintains a fixed distance from a portion of the measurement tool, where the icon is configured to modify the measurement tool, and the icon does not overlap the measurement tool. 
     In some embodiments, the measurement tool comprises a line, the icon maintains the fixed distance from an endpoint of the line, and the icon is configured to control a position of the endpoint of the line. In some embodiments, the measurement tool comprises an ellipse, the icon maintains the fixed distance from a vertex of the ellipse, and the icon is configured to control a length of an axis of the ellipse that includes the vertex. In some embodiments, the measurement tool comprises an ellipse, the icon maintains the fixed distance from a vertex of the ellipse, and the icon is configured to control a rotation of the ellipse. 
     According to another aspect, a method includes displaying, on a touch-sensitive display screen of a processing device in operative communication with an ultrasound device: an ultrasound image, a line extending between a first endpoint and a second endpoint, and an icon located a fixed distance from the first endpoint along a direction defined by the line; detecting a dragging movement covering a distance in a horizontal direction and/or a distance in a vertical direction across the touch-sensitive display screen, wherein the dragging movement begins on or within a threshold distance of the icon; displaying the first endpoint at a new location on the touch-sensitive display screen that is removed from the endpoint&#39;s previous location by the distance in the horizontal direction and/or the distance in the vertical direction; displaying the icon at a new location on the touch-sensitive display screen that is removed from the new location of the first endpoint by the fixed distance along the direction defined by the line; and performing a measurement on the ultrasound image based on the line. 
     According to another aspect, a method includes displaying, on a touch-sensitive display screen of a processing device in operative communication with an ultrasound device, an ultrasound image and a line extending between a first endpoint and a second endpoint; detecting a dragging movement covering a distance in a horizontal direction and/or a distance in a vertical direction across the touch-sensitive display screen, wherein the dragging movement begins on or within a threshold distance of the line; displaying the first endpoint and the second endpoint of the line at new locations on the touch-sensitive display screen that are removed from their previous locations by the distance in the horizontal direction and/or the distance in the vertical direction; and performing a measurement on the ultrasound image based on the line. 
     According to another aspect, a method includes displaying, on a touch-sensitive display screen of a processing device in operative communication with an ultrasound device: an ultrasound image; an ellipse having an axis that is either a major axis or a minor axis of the ellipse, wherein the axis extends between a first vertex and a second vertex of the ellipse; and an icon located a fixed distance from the first vertex along a direction defined by the axis; detecting a dragging movement covering a distance along the direction defined by the axis of the ellipse across the touch-sensitive display screen, wherein the dragging movement begins on or within a threshold distance of the icon; displaying the first vertex at a new location on the touch-sensitive display screen that is removed from the first vertex&#39;s previous location by the distance along the direction defined by the axis of the ellipse; displaying the second vertex at a new location on the touch-sensitive display screen that is removed from the second vertex&#39;s previous location by the distance along the direction defined by the axis of the ellipse; displaying the icon at a new location on the touch-sensitive display screen that is removed from the first vertex&#39;s new location by the fixed distance along the direction defined by the axis of the ellipse; and performing a measurement on the ultrasound image based on the ellipse. 
     According to another aspect, a method includes displaying, on a touch-sensitive display screen of a processing device in operative communication with an ultrasound device: an ultrasound image; an ellipse having an axis that is either a major axis or a minor axis of the ellipse, wherein the axis extends between a first vertex and a second vertex of the ellipse; and an icon located a fixed distance from the first vertex along a direction defined by the axis; detecting a dragging movement covering a distance along and/or a distance orthogonal to the direction defined by the axis of the ellipse across the touch-sensitive display screen, wherein the dragging movement begins on or within a threshold distance of the icon; displaying the first vertex and the second vertex at new locations on the touch-sensitive display screen that are rotated from their previous locations based on the distance that is along and/or the distance orthogonal to the direction defined by the axis of the ellipse; displaying the icon at a new location on the touch-sensitive display screen that is removed from the first vertex&#39;s new location by the fixed distance along the direction defined by the axis of the ellipse; and performing a measurement on the ultrasound image based on the ellipse. 
     According to another aspect, a method includes displaying, on a touch-sensitive display screen of a processing device in operative communication with an ultrasound device: an ultrasound image; an ellipse having an axis that is either a major axis or a minor axis of the ellipse, wherein the axis extends between a first vertex and a second vertex of the ellipse; and an icon located a fixed distance from the first vertex along a direction defined by the axis; detecting a dragging movement covering distance in a horizontal direction and/or a distance in a vertical direction across the touch-sensitive display screen, wherein the dragging movement begins in an interior of the ellipse or within a threshold distance of a boundary of the ellipse; displaying the first vertex and the second vertex at new locations on the touch-sensitive display screen that are removed from their previous locations by the distance in the horizontal direction and/or the distance in the vertical direction; and performing a measurement on the ultrasound image based on the ellipse. 
     According to another aspect, a method of operating a processing device configured to display ultrasound images includes displaying an ultrasound image on a display screen of the processing device; displaying a measurement tool overlay on the ultrasound image, the measurement tool overlay comprising a target point; displaying, on the display screen, a touch-sensitive measurement tool control icon corresponding to the target point; and in response to receiving touch input to the display screen, moving the target point and the touch-sensitive measurement tool control icon while maintaining a fixed distance between them. In some embodiments, the touch-sensitive measurement tool control icon does not overlap the measurement tool overlay. 
     Some aspects include at least one non-transitory computer-readable storage medium storing processor-executable instructions that, when executed by at least one processor, cause the at least one processor to perform the above aspects and embodiments. Some aspects include an ultrasound system having a processing device configured to perform the above aspects and embodiments. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects and embodiments of the application will be described with reference to the following figures. It should be appreciated that the figures are not necessarily drawn to scale. Items appearing in multiple figures are indicated by the same reference number in all the figures in which they appear. 
         FIG.  1    illustrates an example graphical user interface (GUI) that may be displayed on a touch-sensitive display screen of a processing device in an ultrasound system, in accordance with certain embodiments described herein. The GUI includes a line for performing a measurement on an ultrasound image; 
         FIG.  2    illustrates another example of the graphical user interface of  FIG.  1   , in accordance with certain embodiments described herein; 
         FIG.  3    illustrates another example of the graphical user interface of  FIG.  1   , in accordance with certain embodiments described herein; 
         FIG.  4    illustrates another example of the graphical user interface of  FIG.  1   , in accordance with certain embodiments described herein; 
         FIG.  5    illustrates another example of the graphical user interface of  FIG.  1   , in accordance with certain embodiments described herein; 
         FIG.  6    illustrates an example graphical user interface that may be displayed on a touch-sensitive display screen of a processing device in an ultrasound system, in accordance with certain embodiments described herein. The GUI includes an ellipse for performing a measurement on an ultrasound image; 
         FIG.  7    illustrates another example of the graphical user interface of  FIG.  6   , in accordance with certain embodiments described herein; 
         FIG.  8    illustrates another example of the graphical user interface of  FIG.  6   , in accordance with certain embodiments described herein; 
         FIG.  9    illustrates another example of the graphical user interface of  FIG.  6   , in accordance with certain embodiments described herein; 
         FIG.  10    illustrates another example of the graphical user interface of  FIG.  6   , in accordance with certain embodiments described herein; 
         FIG.  11    illustrates a method for determining how much to rotate an ellipse based on a dragging movement, in accordance with certain embodiments described herein; 
         FIG.  12    illustrates an example GUI that may be shown when ultrasound data is being collected, in accordance with certain embodiments described herein; 
         FIG.  13    illustrates an example GUI that may be shown upon selection of a freeze option from the GUI of  FIG.  12   , in accordance with certain embodiments described herein; 
         FIG.  14    illustrates an example GUI that may be shown upon selection of a measurement option from  FIG.  1   : 3 , in accordance with certain embodiments described herein; 
         FIG.  15    illustrates an example process for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein; 
         FIG.  16    illustrates an example process for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein; 
         FIG.  17    illustrates an example process for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein; 
         FIG.  18    illustrates an example process for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein; 
         FIG.  19    illustrates an example process for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein; 
         FIG.  20    illustrates a schematic block diagram illustrating aspects of an example ultrasound system upon which various aspects of the technology described herein may be practiced; and 
         FIG.  21    is a schematic block diagram illustrating aspects of another example ultrasound system upon which various aspects of the technology described herein may be practiced. 
     
    
    
     DETAILED DESCRIPTION 
     Conventional ultrasound systems are large, complex, and expensive systems that are typically only purchased by large medical facilities with significant financial resources. Recently, cheaper and less complex ultrasound imaging devices have been introduced. Such imaging devices may include ultrasonic transducers monolithically integrated onto a single semiconductor die to form a monolithic ultrasound device. Aspects of such ultrasound-on-a-chip devices are described in U.S. patent application Ser. No. 15/415,434 titled “UNIVERSAL ULTRASOUND DEVICE AND RELATED APPARATUS AND METHODS,” filed on Jan. 25, 2017 (and assigned to the assignee of the instant application) and published as U.S. Pat. Pub. No. US-2017-0360397-A1, which is incorporated by reference herein in its entirety. Such an ultrasound device may be in operative communication with a processing device, such as a smartphone or a tablet, having a touch-sensitive display screen. The processing device may display ultrasound images generated from ultrasound data collected by the ultrasound device. 
     The inventors have developed technology for assisting a user in performing measurements on an ultrasound image depicted by the touch-sensitive display screen of a processing device. Performing measurements may include modifying the position, orientation, and/or shape of a measurement tool such as a line or ellipse displayed on the ultrasound image to perform calculations of spatial length or spatial area represented by the ultrasound image. The technology includes icons that are displayed a fixed distance from certain portions of a line or an ellipse, and which in some embodiments do not overlap with any portion of the line or ellipse. The icons may be used to modify the measurement tool. For example, to modify the location of an endpoint of a line, a user may perform a dragging movement across the touch-sensitive display screen that begins on an icon located a fixed distance from the endpoint. The processing device may change the location of the endpoint by a distance corresponding to the distance covered by the dragging movement. The processing device may update, based on the dragging movement, the location of the endpoint at a sufficiently high rate such that the endpoint appears to follow the dragging movement as the dragging movement proceeds. In other words, if a user touches his/her finger to the icon and drags his/her finger across the touch-sensitive display screen, the endpoint may appear to follow the user&#39;s finger. Because changing the location of the endpoint may be initiated in this example by the user touching his/her finger to the icon, which may be located a fixed distance away from the endpoint, the endpoint may be removed from the user&#39;s finger by the fixed distance as the user drags his/her finger across the touch-sensitive display screen. Thus, as the user drags his/her finger, the endpoint may be visible to the user, and the user may be able to determine when the endpoint has moved to the desired location and release his/her finger from the touch-sensitive display to cause the endpoint to remain in the desired location. Additionally, as described above, in some embodiments the icon may not overlap with any portion of the line, which may further help the user to determine, as s/he drags his/her finger, when the line has been positioned as desired. 
     It should be appreciated that the embodiments described herein may be implemented in any of numerous ways. Examples of specific implementations are provided below for illustrative purposes only. It should be appreciated that these embodiments and the features/capabilities provided may be used individually, all together, or in any combination of two or more, as aspects of the technology described herein are not limited in this respect. 
     While the description below includes certain methods that a processing device may use to cause a given result to occur, a processing device may implement different methods in order to cause the same result to occur. In particular, code designed to cause the result to occur may implement a different method to cause the result to occur than those described. 
       FIGS.  1 - 9    illustrate example graphical user interfaces that may be displayed on a touch-sensitive display screen of a processing device in an ultrasound system, in accordance with certain embodiments described herein.  FIGS.  1 - 5    illustrate examples GUIs that include a line for performing a measurement on an ultrasound image.  FIGS.  6 - 10    illustrate example GUIs that include an ellipse for performing a measurement on an ultrasound image. The processing device may be in operative communication with an ultrasound device. Ultrasound systems and devices are described in more detail with reference to  FIGS.  20 - 21   . 
       FIG.  1    illustrates an example GUI  100  that includes a line  102 , a first icon  104 , a second icon  106 , a first crosshairs  108 , a second crosshairs  110 , a measurement value indicator  112 , a delete option  114 , and an ultrasound image  120 . 
     The line  102  extends between a first endpoint  116  and a second endpoint  118 . The first crosshairs  108  may help to visually highlight the location of the first endpoint  116  and the second crosshairs  110  may help to visually highlight the location of the second endpoint  118 . The line  102  is superimposed on the ultrasound image  120  and may be used to perform a length measurement on the ultrasound image  120 . In particular, the processing device may perform a calculation of the spatial length represented by the ultrasound image  120  between the first endpoint  116  and the second endpoint  118 . The processing device may receive information from the ultrasound device indicating that the ultrasound image  120  was collected from an area having a certain size. The processing device may use this information to determine the spatial size represented by each pixel and thereby determine the spatial length represented by the line  102 . (Similar methods may be used for measurements of spatial length and area using an ellipse, as described below). The spatial length represented by the ultrasound image  120  between the first endpoint  116  and the second endpoint  118  is depicted by the measurement value indicator  112 . The user may cause the processing device to modify the locations of the first endpoint  116  and/or the second endpoint  118  on the GUI  100 . For example, the user may cause the processing device to modify the locations of the first endpoint  116  and/or the second endpoint  118  to coincide with endpoints of a particular anatomical structure visible in the ultrasound image  120  if the user desires to measure the distance between the endpoints of the anatomical structure. The processing device may update the measurement value indicator  112  based on the new distance between the first endpoint  116  and the second endpoint  118 . The processing device may remove the line  102 , the first icon  104 , and the second icon  106  from the touch-sensitive display in response to a user selection of the delete option  114 . 
     In  FIG.  1   , the first icon  104  and the second icon  106  are circular, although other forms are possible. Additionally, in  FIG.  1   , no portion of the first icon  104  or the second icon  106  overlaps the line  102 . However, in some embodiments, a portion of the first icon  104  or the second icon  106  may overlap the line  102 . 
     The inventors have developed technology for assisting a user in modifying the locations of the first endpoint  116  and/or the second endpoint  118  (and thereby modifying the position and/or orientation of the line  102 ) using a touch-sensitive display screen. The technology includes display of the first icon  104  and the second icon  106 . The first icon  104  is positioned a fixed distance  122  from the first endpoint  116 . The second icon  106  is positioned the fixed distance  122  from the second endpoint  118 . In some embodiments, the fixed distance  122  may be a predetermined distance. In some embodiments, the fixed distance  122  may be a default distance. In some embodiments, the fixed distance  122  may be selected by a user. In some embodiments, an icon being positioned a fixed distance from some feature (e.g., an endpoint of the line  102 ) may mean that the center of the icon is positioned the fixed distance from the feature. In some embodiments, the fixed distance between the first icon  104  and the first endpoint  116  and the fixed distance between the second icon  106  and the second endpoint  118  may not be the same. 
     The processing device may change the location of the first endpoint  116  based on a dragging movement on the touch-sensitive display screen that begins on or within a threshold distance of the first icon  104 . A dragging movement may include, for example, a user touching his/her finger to the touch-sensitive display and dragging his/her finger to a different location on the touch-sensitive display screen. The processing device may change the location of the second endpoint  118  based on a dragging movement on the touch-sensitive display screen that begins on or within a threshold distance of the second icon  106 . In particular, if a drag that begins on or within a threshold distance of the first icon  104  covers a certain distance in the horizontal direction and/or a certain distance in the vertical direction, the processing device may change the location of the first endpoint  116  by that same distance in the horizontal direction and/or distance in the vertical direction. (A drag that covers a certain distance in a certain direction need not mean that the drag actually proceeded along that direction, but rather than the drag had a component along that direction. For example, a drag in an arbitrary direction across a touch-sensitive display screen may have a component along the horizontal direction and a component along the vertical direction of the touch-sensitive display screen). If a drag that begins on or within a threshold distance of the second icon  106  covers a certain distance in the horizontal direction and/or a certain distance in the vertical direction, the processing device may change the location of the second endpoint  118  by that same distance in the horizontal direction and/or distance in the vertical direction. 
     For example, consider the touch-sensitive display screen having an array of pixels, each pixel having a location that is x pixels in the horizontal direction and a location that is y pixels in the vertical location, where x and y are measured from an origin (e.g., a corner of the touch-sensitive display screen). Consider further that the first endpoint is located at e 1   x , e 1   y ). When the user performs a dragging movement on the touch-sensitive display screen that begins at a starting location (d 1   x , d 1   y ) on or within a threshold distance of the first icon  104  and ends at an ending location (d 2   x , d 2   y ), the processing device may change the location of the first endpoint  116  such that the first endpoint  116  is displayed at (e 1   x −(d 2   x −d 1   x ), e 1   y +(d 2   y −d 1   y )). The processing device may similarly change the location of the second endpoint  118  based on a drag that begins at or within a threshold distance of the second icon  106 . Once the processing device has displayed the first endpoint  116  and/or the second endpoint  118  in a new location, the processing device may display the rest of the line  102  between the first endpoint  116  and/or the second endpoint  118 . In some embodiments, the processing device may use the Cartesian equation for a line to determine locations for points along the line that are not endpoints. 
     The processing device may update, based on a dragging movement, the location of the first endpoint  116  at a sufficiently high rate such that the first endpoint  116  appears to follow the dragging movement as the dragging movement proceeds. In other words, if a user touches his/her finger to the first icon  104  and drags his/her finger across the touch-sensitive display screen, the first endpoint  116  may appear to follow the user&#39;s finger. Because changing the location of the first endpoint  116  may be initiated in this example by the user touching his/her finger to the first icon  104 , which may be located a fixed distance away from the first endpoint  116 , the first endpoint  116  may be removed from the user&#39;s finger by the fixed distance as the user drags his/her finger across the touch-sensitive display screen. Thus, as the user drain his/her finger, the first endpoint  116  may be visible to the user, and the user may be able to determine when the first endpoint  116  has moved to the desired location and release his/her finger from the touch-sensitive display to cause the first endpoint  116  to remain in the desired location. The same discussion applies to the second endpoint  118  and the second icon  106 . 
     After a dragging movement that begins at or within a threshold distance of the first icon  104 , the processing device may change the location of the first icon  104  such that the first icon  104  is displayed a fixed distance from the first endpoint  116  along a direction defined by the line  102 . After a dragging movement that begins at or within a threshold distance of the second icon  106 , the processing device may change the location of the second icon  106  such that the second icon  106  is displayed a fixed distance from the second endpoint  118  along a direction defined by the line  102  (i.e., the direction defined by the line  102  after the location of the first endpoint  116  and/or the location of the second endpoint  118  has changed). For example, consider that after the dragging movement, the first endpoint  116  is located at (e 1   x , e 1   y ), the second endpoint  118  is located at (e 2   x , e 2   y ), and the fixed distance is d. The new location (i 1   x , i 1   y ) of the first icon  104  may satisfy the two equations sqrt((i 1   x −e 1   x ){circumflex over ( )}2+(i 1   y −e 1   y ){circumflex over ( )}2)=d and (i 1   y −e 1   y )/(i 1   x −e 1   x )=(e 1   y −e 2   y )/(e 1   x −e 2   x ). It should be noted that there may be two sets of solutions for these two equations, and the solution chosen may be the one where (i 1   y , i 1   x ) does not coincide with the line  102 , meaning that i 1   x  is not between e 1   x  and e 2   x , and i 1   y  is not between e 1   y  and e 2   y . The processing device may similarly change the location of the second icon  106  based on a new position of the second endpoint  118 . 
     In some embodiments, in response to a dragging movement beginning on an icon and covering a distance in the horizontal direction and/or a distance in the vertical direction, the processing device may change the location of the icon by the distance in the horizontal direction and/or the distance in the vertical direction equivalent to the distance in the horizontal direction and/or a distance in the vertical direction covered by the dragging movement, and change the location of the corresponding endpoint to be a fixed distance from the icon&#39;s new position along a direction defined by the line. In some embodiments, in response to a dragging movement beginning on an icon and covering a distance in the horizontal direction and/or a distance in the vertical direction, the processing device may change the location of both the endpoint and the icon by the distance in the horizontal direction and/or the distance in the vertical direction equivalent to the distance in the horizontal direction and/or a distance in the vertical direction covered by the dragging movement. 
     In some embodiments, the processing device may remove the first icon  104  from display during a dragging movement that begins at the first icon  104  and remove the second icon  106  from display during a dragging movement that begins at the second icon  106 . This may help the user to understand that the measurement will be performed based on the line  102  and not based on either the first icon  104  or the second icon  106 . In other words, this may help the user to understand that the line  102  does not extend to the first icon  104  or the second icon  106 . However, in other embodiments, the processing device may continue to display the first icon  104  and the second icon  106  during a dragging movement that begins at the first icon  104  or the second icon  106 , respectively. 
       FIG.  2    illustrates the example graphical user interface (GUI)  100  after a dragging movement beginning on or within a threshold distance of the first icon  104 . Prior to the dragging movement, the GUI  100  may have appeared as shown in  FIG.  1   . The processing device has changed the location of the first endpoint  116  from its location in  FIG.  1   . As described above, the processing device may have changed the location of the first endpoint  116  by a distance in the horizontal direction and/or a distance in the vertical direction equivalent to the distance in the horizontal direction and/or the distance in the vertical direction covered by the dragging movement. The processing device has displayed the rest of the line  102  between the new location of the first endpoint  116  and the previous location of the second endpoint  118 . The processing device has also changed the location of the first icon  104  from its location in  FIG.  1    to be the fixed distance  122  away from the first endpoint  116  along a direction defined by the line  102 . It should be noted that the processing device has changed the measurement value depicted by the measurement value indicator  112  in  FIG.  2    from that shown in  FIG.  1    based on the change in length of the line  102  from  FIG.  1    to  FIG.  2   . 
       FIG.  3    illustrates the example graphical user interface (GUI)  100  after a dragging movement beginning on or within a threshold distance of the second icon  106 . Prior to the dragging movement, the GUI  100  may have appeared as shown in  FIG.  2   . The processing device has changed the location of the second endpoint  118  from its location in  FIG.  1   . As described above, the processing device may have changed the location of the second endpoint  118  by a distance in the horizontal direction and/or a distance in the vertical direction equivalent to the distance in the horizontal direction and/or the distance in the vertical direction covered by the dragging movement. The processing device has displayed the rest of the line  102  between the new location of the second endpoint  118  and the previous location of the first endpoint  116 . The processing device has also changed the location of the second icon  106  from its location in  FIG.  2    to be the fixed distance  122  away from the second endpoint  118  along a direction defined by the line  102 . It should be noted that the processing device has changed the measurement value depicted by the measurement value indicator  112  in  FIG.  3    from that shown in  FIG.  2    based on the change in length of the line  102  from  FIG.  2    to  FIG.  3   . 
     In some embodiments, the processing device may change the position of both the first endpoint  116  and the second endpoint  118  based on a dragging movement that begins on or within a threshold distance of any portion of the line  102 . When the user performs a dragging movement on the touch-sensitive display screen that begins at a starting location (d 1   x , d 1   y ) on or within a threshold distance of the line  102  and ends at an ending location (d 2   x , d 2   y ), the processing device may change the locations of both the first endpoint  116  and the second endpoint  118  by a distance of (d 2   x −d 1   x , d 2   y −d 1   y ). The processing device may also change the locations of the first icon  104  and the second icon  106  such that they are the fixed distance  122  away from the first endpoint  116  and the second endpoint  118 , respectively, along the direction of the line  102 . Once the processing device has displayed the first endpoint  116  and the second endpoint  118  in new locations, the processing device may display the rest of the line  102  between the new locations of the first endpoint  116  and the second endpoint  118 . In some embodiments, the processing device may use the Cartesian equation for a line to determine locations for points along the line  102  between the first endpoint  116  and the second endpoint  118 . In some embodiments, the processing device may change the locations of all displayed points along the line  102  by a distance of (d 2   x −d 1   x , d 2   y −d 1   y ). 
       FIG.  4    illustrates the example graphical user interface (GUI)  100  after a dragging movement beginning on or within a threshold distance of the line  102 . Prior to the dragging movement, the GUI  100  may have appeared as shown in  FIG.  3   . The processing device has changed the location of the line from its location in  FIG.  3   . As described above, the processing device may have changed the location of the first endpoint  116  and the second endpoint  118  by a distance in the horizontal direction and/or a distance in the vertical direction equivalent to the distance in the horizontal direction and/or the distance in the vertical direction covered by the dragging movement. The processing device has displayed the rest of the line  102  between the new locations of the first endpoint  116  and the second endpoint  118 . The processing device has also changed the locations of the first icon  104  and the second icon  106  from their locations in  FIG.  3    to be the fixed distance  122  away from the first endpoint  116  and the second endpoint  116 , respectively, along a direction defined by the line  102 . 
       FIG.  5    illustrates the example graphical user interface (GUI)  100  during a dragging movement beginning on or within a threshold distance of the first icon  104 . The GUI  100  in  FIG.  5    is similar to that shown in  FIG.  2   , with the addition of an inset  524 . The inset  524  depicts a magnification of a portion  526  of the ultrasound image  120 . In particular, the inset  524  depicts a portion  526  of the ultrasound image  120  that is proximal to the first endpoint  116 . The inset  524  further depicts the first endpoint  116 , the first crosshairs  108 , and a portion of the line  102  that is within the portion  526  of the ultrasound image  120 . The processing device may display the inset  524  when the user begins a dragging movement and continue to display the inset  524  as the user continues the dragging movement. Because the inset  524  illustrates the magnified portion  526  of the ultrasound image  120  that is proximal to the first endpoint  116 , the user may use the inset  524  to determine how to perform the dragging movement in order to change the location of the first endpoint  116  to the desired location on the ultrasound image  120 , and also to determine when the first endpoint  116  is at the desired location. If the user begins a dragging movement on or within a threshold distance of the second icon  106 , the processing device may display the inset  524  and show a magnified portion (not shown in  FIG.  5   ) of the ultrasound image  120  that is proximal to the second endpoint  118 , and the inset  524  may also depict the second endpoint  118 , the second crosshairs  110 , and a portion of the line  102  that is within the portion of the ultrasound image  120  depicted by the inset  524 . It should be noted that in  FIG.  5   , in contrast to  FIG.  2   , the processing device does not display the first icon  104  during the dragging movement that began on or within a threshold distance of the first icon  104 . However, in some embodiments, the processing may display the first icon  104  during the dragging movement. In some embodiments, the processing device may not display the inset  524  during a dragging movement. 
     It should be understood that in some embodiments, certain portions of the GUI  100  may be absent. For example, the first crosshairs  108 , the second crosshairs  110 , and/or the delete option  114  may be absent. In some embodiments, the measurement value indicator  112  may have a different form than shown and/or be located at a different location on the touch-sensitive display screen. Additionally, while the GUI  100  shows certain other features that are not described herein (e.g., certain buttons or indicators), in some embodiments such features may be absent or different. 
       FIG.  6    illustrates an example graphical user interface (GUI)  600  that includes an ellipse  638 , a first icon  640 , a second icon  662 , a first measurement value indicator  656 , a second measurement value indicator  658 , a delete option  660 , and an ultrasound image  120 . The second icon  662  includes a first arrow  652  and a second arrow  654 . 
     The ellipse  638  includes a center location  664 , a first axis  674 , and a second axis  676 . The first axis  674  extends between two endpoints, namely a first vertex  642  and a second vertex  644  of the ellipse  638 . The second axis  676  extends between two endpoints, namely a third vertex  646  and a fourth vertex  648  of the ellipse  638 . The first axis  674  and the second axis  676  may be equivalent to the major axis and the minor axis of the ellipse, or vice versa. It should be appreciated that the ellipse  638  may be a circle. The ellipse  638  is superimposed on the ultrasound image  120  and may be used by the processing device to perform a measurement on the ultrasound image  120 . In  FIG.  6   , the processing device displays the value of the spatial length represented by the ultrasound image  120  along the circumference of the ellipse  638  with the first measurement value indicator  656  and the processing device displays the value of the spatial area represented by the ultrasound image  120  within the ellipse  638  with the second measurement value indicator  658 . The user may cause the processing device to modify the ellipse (e.g., the position, orientation, and/or shape of the ellipse). For example, the user may cause the processing device to modify the ellipse to coincide with a particular anatomical structure visible in the ultrasound image  120  if the user desires to measure the circumference or area of the anatomical structure as depicted by the ultrasound image  120 . 
     The inventors have developed technology for assisting a user in modifying the position, orientation, and shape of the ellipse  638  using a touch-sensitive display screen. The technology includes display of the first icon  640  and the second icon  662 . The processing device displays the first icon  640  a fixed distance  650  from the first vertex  642 . The processing device displays the second icon  662  the fixed distance  650  from the fourth vertex  648 . In some embodiments, the fixed distance  650  may be a predetermined distance. In some embodiments, the fixed distance  650  may be a default distance. In some embodiments, the fixed distance  650  may be selected by a user. In some embodiments, an icon being positioned a fixed distance from some feature (e.g., a vertex of the ellipse  638 ) may mean that the center of the icon is positioned the fixed distance from the feature. In some embodiments, the fixed distance between the first icon  640  and the first vertex  642  and the fixed distance between the second icon  662  and the third vertex  646  may not be the same. 
     In  FIG.  6   , the first icon  640  and the second icon  662  are circular, although other forms are possible. Additionally, in  FIG.  6   , no portion of the first icon  640  or the second icon  662  overlaps the ellipse  638 . However, in some embodiments, a portion of the first icon  640  or the second icon  662  may overlap the ellipse  638 . 
     The processing device may change the length of the first axis  674  based on a dragging movement on the touch-sensitive display screen that begins on or within a threshold distance of the first icon  640 . In particular, if the drag that begins on or within a threshold distance of the first icon  640  covers a certain distance away from the ellipse  638  along the direction defined by the first axis  674 , the processing device may change the locations of the first vertex  642  and the second vertex  644  by that same distance away from the ellipse along the direction defined by the first axis  674 . In other words, the processing device may expand the first axis  674  of the ellipse  638  by two times the distance along the direction defined by the first axis  674 . If the drag that begins on or within a threshold distance of the first icon  640  covers a certain distance towards from the ellipse  638  along the direction defined by the first axis  674 , the processing device may change the locations of the first vertex  642  and the second vertex  644  by that same distance towards from the ellipse along the direction defined by the first axis  674 . In other words, the processing device may contract the first axis  674  of the ellipse  638  by two times the distance along the direction defined by the first axis  674 . The processing device may similarly change the length of the second axis  676  based on a dragging movement on the touch-sensitive display screen that begins on or within a threshold distance of the second icon  662 . The processing device may display other points along the ellipse  638  based on new lengths of the first axis  674  and/or the second axis  676 . For example, the processing device may determine new locations for other points along the ellipse  638  based on the Cartesian equation for an ellipse  638 . In some embodiments, to display the ellipse  638  based on the Cartesian equation for an ellipse  638 , the processing device may only use the center location  664  of the ellipse, one of the first vertex  642  and the second vertex  644 , and one of the third vertex  646  and the fourth vertex  648 . 
     Consider the touch-sensitive display screen having an array of pixels, each pixel having a location that is x pixels in the horizontal direction and a location that is y pixels in the vertical location, where x and y are measured from an origin (e.g., a corner of the touch-sensitive display screen). For simplicity, assume the first axis  674  of the ellipse  638  is parallel to the vertical direction of the touch-sensitive display and the second axis  676  of the ellipse is parallel to the horizontal direction of the touch-sensitive display. Consider further that the first vertex  642  is located at (v 1   x , v 1   y ), the second vertex  644  is located at (v 2   x , v 2   y ), and the first icon is located at (i 1   x , i 1   y ). When the user performs a dragging movement on the touch-sensitive display screen that begins at a starting location (d 1   x , d 1   y ) on or within a threshold distance of the first icon  640  and ends at an ending location (d 2   x , d 2   y ), the processing device may change the location of the first vertex  642  such that the first vertex  642  is displayed at (v 1   x , v 1   y +(d 2   y −d 1   y )). The processing device may also change the location of the second vertex  644  such that the second vertex  644  is displayed at (v 2   x , v 2   y −(d 2   y −d 1   y )). As described above, the processing device may display other points along the ellipse  638  based on the new locations of the first vertex  642  and the second vertex  644 . 
     The processing device may update, based on a dragging movement, the location of the first vertex  642  at a sufficiently high rate such that the first vertex  642  appears to follow the dragging movement as the dragging movement proceeds. In other words, if a user touches his/her finger to the first icon  640  and drags his/her finger across the touch-sensitive display screen, the first vertex  642  may appear to follow the user&#39;s finger. Because changing the location of the first vertex  642  may be initiated in this example by the user touching his/her finger to the first icon  640 , which may be located a fixed distance away from the first vertex  642 , the first vertex  642  may be removed from the user&#39;s finger by the fixed distance as the user drags his/her finger across the touch-sensitive display screen. Thus, as the user drags his/her finger, the first vertex  642  may be visible to the user, and the user may be able to determine when the first vertex  642  has moved to the desired location and release his/her finger from the touch-sensitive display to cause the first vertex  642  to remain in the desired location. The same discussion applies to the fourth vertex  648  and the second icon  662 . 
     After a dragging movement, the processing device may change the location of the first icon  640  such that the first icon  640  is displayed a fixed distance from the first vertex  642  along the direction defined by the first axis  674 . For example, consider that after the dragging movement, the first vertex  642  is located at (v 1   x , v 1   y ), the second vertex  644  is located at (v 2   x , v 2   y ), and the fixed distance is d. The new location (i 1   x , i 1   y ) of the first icon  640  may satisfy the two equations sqrt((i 1   x −v 1   x ){circumflex over ( )}2+(i 1   y −v 1   y ){circumflex over ( )}2)=d and (i 1   y −v 1   y )/(i 1   x −v 1   x )=(v 1   y −v 2   y )/(v 1   x −v 2   x ). It should be noted that there may be two sets of solutions for these two equations, and the solution chosen may be the one where (i 1   y , i 1   x ) is not within the ellipse  630 , meaning that i 1   x  is not between v 1   x  and v 2   x , and i 1   y  is not between v 1   y  and v 2   y.    
     In the simplified example described above, the direction defined by the first axis  674  is along the vertical direction of the touch-sensitive display, but in the general case where the direction defined by the first axis  674  is rotated to an angle relative to the vertical direction of the touch-sensitive display, the expressions above may be modified to account for such rotation. In a similar manner as described above regarding changing the location of the first vertex  642 , the second vertex  644 , and the first icon  640 , the processing device may change the location of the third vertex  646 , the fourth vertex  648 , and the second icon  662  based on a dragging movement that begins on or within a threshold distance of the second icon  662  and covers a certain distance away from/toward the ellipse  638  along the direction defined by the second axis  676 . 
       FIG.  7    illustrates the example graphical user interface (GUI)  600  after a dragging movement beginning on or within a threshold distance of the first icon  640  and covering a distance towards the ellipse  638  along the direction of the first axis  674 . Prior to the dragging movement, the GUI  600  may have appeared as shown in  FIG.  6   . The processing device has changed the locations of the first vertex  642  and the second vertex  644  from their locations in  FIG.  6   . (In other words, the processing device has changed the length of the first axis  674 .) As described above, the processing device may have changed the locations of the first vertex  642  and the second vertex  644  by the distance covered by the dragging movement along the direction defined by the first axis  674 . The processing device has also changed the location of the first icon  640  from its location in  FIG.  6    to be the fixed distance  650  away from the first vertex  674  along a direction defined by the first axis  674 . It should be noted that the processing device has changed the measurement values depicted by the first measurement value indicator  656  and the second measurement value indication  658  from that shown in  FIG.  6    based on the change in length of the first axis  674  from  FIG.  6    to  FIG.  7   . 
       FIG.  8    illustrates the example graphical user interface (GUI)  600  after a dragging movement beginning on or within a threshold distance of the second icon  662  and covering a distance towards the ellipse  638  along the direction of the second axis  676 . Prior to the dragging movement, the GUI  600  may have appeared as shown in  FIG.  7   . The processing device has changed the locations of the third vertex  646  and the fourth vertex  648  from their locations in  FIG.  7   . (In other words, the processing device has changed the length of the second axis  676 .) As described above, the processing device may have changed the locations of the third vertex  646  and the fourth vertex  648  by the distance covered by the dragging movement along the direction defined by the second axis  676 . The processing device has also changed the location of the second icon  662  from its location in  FIG.  7    to be the fixed distance  650  away from the fourth vertex  648  along a direction defined by the second axis  676 . It should be noted that the processing device has changed the measurement values depicted by the first measurement value indicator  656  and the second measurement value indicator  658  from that shown in  FIG.  7    based on the change in length of the second axis  676  from  FIG.  7    to  FIG.  8   . 
     In some embodiments, the processing device may change the position of the ellipse  638  based on a dragging movement that begins in the interior of the ellipse  638 , on the boundary of the ellipse  638 , or within a threshold distance of the boundary of the ellipse  638 . When the user performs a dragging movement on the touch-sensitive display screen that begins at a starting location (d 1   x , d 1   y ) in the interior of the ellipse  638  or within a threshold distance of the boundary of the ellipse  638  and ends at an ending location (d 2   x , d 2   y ), the processing device may change the locations of every point on the ellipse  638 , as well as the first icon  640  and the second icon  662 , by a distance of (d 2   x −d 1   x , d 2   y −d 1   y ). In some embodiments, rather than moving every point on the ellipse  638  by a specific distance, the processing device may change the locations of the center  664  of the ellipse  638 , the first vertex  642 , the second vertex  644 , the third vertex  646 , and the fourth vertex  648  by the specific distance and display the rest of the ellipse  638  based on these new locations using the Cartesian equation for an ellipse  638 . 
       FIG.  9    illustrates the example graphical user interface (GUI)  600  after a dragging movement beginning in the interior of the ellipse  638  or within a threshold distance of the boundary of the ellipse  638 . Prior to the dragging movement, the GUI  600  may have appeared as shown in  FIG.  8   . The processing device has changed the position (but not the orientation or shape) of the ellipse  638  by the distance covered by the dragging movement. The processing device has also changed the location of the first icon  640  from its location in  FIG.  8    to be the fixed distance  650  away from the first vertex  674  along a direction defined by the first axis  674 , and the location of the second icon  662  from its location in  FIG.  8    to be the fixed distance  650  away from the fourth vertex  648  along a direction defined by the second axis  676 . 
     In some embodiments, the processing device may rotate the ellipse  638  based on a dragging movement that begins on or at the second icon  662  and covers a distance along and/or a distance orthogonal to the direction of the second axis  676  of the ellipse  638 .  FIG.  10    illustrates the example graphical user interface (GUI)  600  after a dragging movement beginning on or within a threshold distance of the second icon  662  and covering a distance along and/or a distance orthogonal to the direction of the second axis  676 . Prior to the dragging movement, the GUI  600  may have appeared as shown in  FIG.  9   . As described above, the processing device has rotated the locations of every point of the ellipse  638  based on the drag distance along and/or the drag distance orthogonal to the direction of the second axis  676 . The processing device has also changed the location of the first icon  640  from its location in  FIG.  4    to be the fixed distance  650  away from the first vertex  674  along a direction defined by the first axis  674 , and the location of the second icon  662  from its location in  FIG.  8    to be the fixed distance  650  away from the fourth vertex  648  along a direction defined by the second axis  676 . 
       FIG.  11    illustrates a method for determining how much to rotate the ellipse  638  based on the dragging movement, in accordance with certain embodiments described herein. The left side of  FIG.  11    shows the ellipse  638  before the dragging movement and the right side of  FIG.  11    shows the ellipse  638  after the dragging movement. For simplicity, before the dragging movement, the center location  664  is labeled C, the second vertex  644  is labeled A, and the first vertex  642  is labeled B. After the dragging movement, the center location  664  is labeled C′, the location of the second vertex  644  is labeled A′, the location of the first vertex  642  is labeled B′, and the location of the second icon  662  is labeled D′. The dragging movement begins at the location of the second icon  662  and ends at a location separated from the previous location by a vector V (where V may have components along and/or orthogonal to the second axis  676 ). The processing device may determine the location of C′ to be the same as C, namely, the center location  664  may not change. The processing device may determine the location of A′ to be A+V, in other words, the previous location of the second vertex  644  plus the vector of the dragging movement. The processing device may determine the location of B′ to be C+normal( A′C )*length( BC ). In other words, the new location of the first vertex  642  may be the center location  664  plus a vector that has a length equal to the distance between the center location  664  and the previous location of the first vertex  642 , and a direction that is perpendicular to a vector between the center location  664  and the new location of the second vertex  644 . The processing device may determine new locations for the rest of the points on the ellipse  638  based on the new locations for the first vertex  642  and the second vertex  644 . 
     It should be appreciated from the above description of  FIG.  11    that rotations of the ellipse  638  may be controlled both by components of a drag distance beginning at or within a threshold distance of the second icon  662  (in other words, the components of the vector V) that are along the direction of the second axis  676  and orthogonal to the direction of the second axis  676 . As described above, a dragging movement beginning at or within a threshold distance of the second icon  662  and covering a distance along the direction of the second axis  676  may also control the length of the second axis  676 . Thus, a dragging movement beginning at or within a threshold distance of the second icon  662  and having only a component along the direction of the second axis  676  may only modify the length of the second axis  676 . A dragging movement beginning at or within a threshold distance of the second icon  662  and having components both along and orthogonal to the direction of the second axis  676  may modify both the length of the second axis  676  and the rotation of the ellipse  638 . The description of  FIG.  11    may apply both to the general case of a dragging movement having components both along and orthogonal to the direction of the second axis  676 , as well as the special case of a dragging movement having a component only along the direction of the second axis  676 . In some embodiments, the processing device may use a different method for determining how to rotate an ellipse than the method illustrated by  FIG.  11   . 
     The first arrow  652  and the second arrow  654  may serve to indicate to a user that the second icon  662  (as opposed to the first icon  640 ) can be used to rotate the ellipse  638 . In some embodiments, the positioning of the first arrow  652  and the second arrow  654  may change as the shape of the ellipse  638  changes so that the arrows approximate the curvature of the ellipse  638 . 
     It should be understood that in some embodiments, certain portions of the GUI  600  may be absent. For example, the second arrow  654 , the first arrow  652 , the first measurement value indicator  656 , the second measurement value indicator  658 , and/or the delete option  660  may be absent. In some embodiments, the first measurement value indicator  656  and/or the second measurement value indicator  658  may have different forms than shown and/or be located at a different locations on the touch-sensitive display screen. Additionally, while the GUI  600  shows certain other features that are not described herein (e.g., certain buttons or indicators), in some embodiments such features may be absent or different. 
     While the above description has described that a processing device may perform certain calculations using pixels, in some embodiments the processing device may perform calculations using points. It should be noted that certain calculations described herein may produce fractional pixel results. In some embodiments, fractional pixel results may be rounded to a whole pixel. In some embodiments, the processing device may use antialiasing to interpret pixel values for a fractional pixel result (e.g., to interpret pixel values for pixels ( 1 ,  1 ) and ( 2 ,  1 ) when a calculation indicates that something should be displayed at pixel ( 1 . 5 ,  1 )). As described above, the processing device may change the location of one feature of a measurement tool (e.g., a line or an ellipse) based on a dragging movement that begins on or within a threshold distance of a certain feature. In some embodiments, the distance may be measured in pixels (e.g., 30 pixels). While the above description has described a touch-sensitive display screen, in some embodiments the screen may not be touch-sensitive display screen, and a click and drag of a cursor (e.g., using a mouse) may be the equivalent of a dragging movement. 
       FIG.  12    illustrates an example GUI  1200  that may be shown when ultrasound data is being collected, in accordance with certain embodiments described herein. The GUI  1200  depicts the most recent ultrasound image  120  collected by the processing device from the ultrasound device. As further ultrasound images  120  are collected, the processing device may continuously update the GUI  1200  to depict the most recent ultrasound image  120  collected. The GUI  1200  further includes a freeze option  1226 . 
       FIG.  13    illustrates an example GUI  1300  that may be shown upon selection of the freeze option  1226 , in accordance with certain embodiments described herein. The GUI  1300  depicts the most recent ultrasound image  120  collected by the processing device from the ultrasound device when the freeze option  1226  was selected. In other words, the processing device freezes the most recent ultrasound  120  on the GUI  1300 , and the processing device may not update the GUI  1300  with ultrasound images  120  that are collected subsequently. In the GUI  1300 , the freeze option  1226  can have a different color or pattern, which may indicate that the GUI  1300  is currently showing a frozen ultrasound image  120 . Additionally, the GUI  1300  depicts a measurement option  1328 . 
       FIG.  14    illustrates an example GUI  1400  that may be shown upon selection of the measurement option  1328 , in accordance with certain embodiments described herein. The GUI  1400  can depict the freeze option  1226  having a different color or pattern as explained with respect to  FIG.  13   , as well as a label option  1430 , an ellipse measurement option  1432 , a line measurement option  1434 , and a menu close option  1436 . Upon selection of the label option  1430 , the processing device may display a GUI enabling a user to place labels on the ultrasound image  130 . Upon selection of the ellipse measurement option  1432 , the processing device may display the GUI  600 , with the ellipse  638 , the first icon  640 , and the second icon  662  shown in default positions. Upon selection of the line measurement option  1434 , the processing device may display the GUI  100 , with the line  102 , the first icon  104 , and the second icon  106  shown in default positions. Upon selection of the menu close option  1436 , the processing device may display the GUI  1300  (i.e., remove from display the label option  1430 , the ellipse measurement option  1432 , and the line measurement option  1434 ). 
       FIGS.  15 - 19    illustrate example processes for performing measurements on an ultrasound image, in accordance with certain embodiments described herein. The processes may be performed by a processing device in an ultrasound system. The processing device may be, for example, a mobile phone, tablet, or laptop in operative communication with an ultrasound probe. The ultrasound probe and the processing device may communicate over a wired communication link (e.g., over Ethernet, a Universal Serial Bus (USB) cable or a Lightning cable) or over a wireless communication link (e.g., over a BLUETOOTH, WiFi, or ZIGBEE wireless communication link). 
       FIG.  15    illustrates an example process  1500  for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein. Further description of the process  1500  may be found with reference to  FIGS.  1 - 5   . 
     In act  1502 , the processing device displays, on a touch-sensitive display screen, (1) an ultrasound image, (2) a line extending between a first endpoint and a second endpoint and (3) an icon located a fixed distance from the first endpoint along a direction defined by the line. The process  1500  proceeds from act  1502  to act  1504 . 
     In act  1504 , the processing device detects a dragging movement covering a distance in the horizontal direction and/or a distance in the vertical direction across the touch-sensitive display screen, where the dragging movement begins on or within a threshold distance of the icon. The process  1500  proceeds from act  1504  to act  1506 . 
     In act  1506 , the processing device displays the first endpoint at a new location on the touch-sensitive display screen that is removed from the endpoint&#39;s previous location by the distance in the horizontal direction and/or the distance in the vertical direction covered by the dragging movement. The process  1500  proceeds from act  1506  to act  1508 . 
     In act  1508 , the processing device displays the icon at a new location on the touch-sensitive display screen that is removed from the new location of the first endpoint by the fixed distance along the direction defined by the line. The process  1500  proceeds from act  1508  to act  1510 . 
     In act  1510 , the processing device performs a measurement on the ultrasound image based on the line. For example, the processing device may perform a calculation of the spatial length represented by the ultrasound image between the first endpoint and the second endpoint of the line. In some embodiments, the processing device may display the result of the measurement. 
     In some embodiments, certain acts of the process  1500  may be absent. For example, in some embodiments, act  1510  may be absent. In some embodiments, acts  1504 - 1510  may be absent. In some embodiments, acts  1504 - 1508  may be absent. In some embodiments, other combinations of acts may be absent. 
       FIG.  16    illustrates an example process  1600  for performing measurements on an ultrasound image based on a line, in accordance with certain embodiments described herein. Further description of the process  1600  may be found with reference to  FIG.  4   . 
     In act  1602 , the processing device displays, on a touch-sensitive display screen, (1) an ultrasound image and (2) a line extending between a first endpoint and a second endpoint. The process  1600  proceeds from act  1602  to act  1604 . 
     In act  1604 , the processing device detects a dragging movement covering a distance in the horizontal direction and/or a distance in the vertical direction across the touch-sensitive display screen, where the dragging movement begins on or within a threshold distance of the line. The process  1600  proceeds from act  1604  to act  1606 . 
     In act  1606 , the processing device displays both the first endpoint and the second endpoint of the line at new locations on the touch-sensitive display screen that are removed from their previous locations by the distance in the horizontal direction and/or the distance in the vertical direction. The process  1600  proceeds from act  1606  to act  1608 . 
     In act  1608 , the processing device performs a measurement on the ultrasound image based on the line. For example, the processing device may perform a calculation of the spatial length represented by the ultrasound image between the first endpoint and the second endpoint of the line. In some embodiments, the processing device may display the result of the measurement. 
     In some embodiments, certain acts of the process  1600  may be absent. For example, in some embodiments, act  1608  may be absent. In some embodiments, acts  1604 - 1608  may be absent. In some embodiments, acts  1604 - 1606  may be absent. In some embodiments, other combinations of acts may be absent. 
       FIG.  17    illustrates an example process  1700  for performing measurements on an ultrasound image based on an ellipse, in accordance with certain embodiments described herein. Further description of the process  1700  may be found with reference to  FIGS.  6 - 8   . 
     In act  1702 , the processing device displays, on a touch-sensitive display screen, (1) an ultrasound image, (2) an ellipse having an axis that is either the major or minor axis of the ellipse, where the axis extends between a first vertex and a second vertex; and (3) an icon located a fixed distance from the first vertex along a direction defined by the axis. The process  1700  proceeds from act  1702  to act  1704 . 
     In act  1704 , the processing device detects a dragging movement covering a distance along the direction defined by the axis of the ellipse across the touch-sensitive display screen, where the dragging movement begins on or within a threshold distance of the icon. The process  1700  proceeds from act  1704  to act  1706 . 
     In act  1706 , the processing device displays the first vertex at a new location on the touch-sensitive display screen that is removed from the first vertex&#39;s previous location by the distance along the direction defined by the axis of the ellipse covered by the dragging movement. The process  1700  proceeds from act  1706  to act  1708 . 
     In act  1708 , the processing device displays the second vertex at a new location on the touch-sensitive display screen that is removed from the second vertex&#39;s previous location by the distance along the direction defined by the axis of the ellipse covered by the dragging movement. The process  1700  proceeds from act  1708  to act  1710 . 
     In act  1710 , the processing device displays the icon at a new location on the touch-sensitive display screen that is removed from the first vertex&#39;s new location by the fixed distance along the direction defined by the axis of the ellipse. The process  1700  proceeds from act  1710  to act  1712 . 
     In act  1712 , the processing device performs a measurement on the ultrasound image based on the ellipse. For example, the processing device may perform a calculation of the spatial length represented by the ultrasound image along the circumference of the ellipse or a calculation of the spatial area represented by the ultrasound image within the ellipse. In some embodiments, the processing device may display the result of the measurement. 
     In some embodiments, certain acts of the process  1700  may be absent. For example, in some embodiments, act  1712  may be absent. In some embodiments, acts  1704 - 1712  may be absent. In some embodiments, acts  1704 - 1710  may be absent. In some embodiments, other combinations of acts may be absent. 
       FIG.  18    illustrates an example process  1800  for performing measurements on an ultrasound image based on an ellipse, in accordance with certain embodiments described herein. Further description of the process  1800  may be found with reference to  FIGS.  10 - 11   . 
     In act  1802 , the processing device displays, on a touch-sensitive display screen, (1) an ultrasound image, (2) an ellipse having an axis that is either the major or minor axis of the ellipse, where the axis extends between a first vertex and a second vertex; and (3) an icon located a fixed distance from the first vertex along a direction defined by the axis. The process  1800  proceeds from act  1802  to act  1804 . 
     In act  1804 , the processing device detects a dragging movement covering a distance along and/or a distance orthogonal to the direction defined by the axis of the ellipse across the touch-sensitive display screen, where the dragging movement begins on or within a threshold distance of the icon. The process  1800  proceeds from act  1804  to act  1806 . 
     In act  1806 , the processing device displays the first vertex and the second vertex at new locations on the touch-sensitive display screen that are rotated from their previous locations based on the distance along and/or the distance orthogonal to the direction defined by the axis of the ellipse that is covered by the dragging movement. The process  1800  proceeds from act  1806  to act  1808 . 
     In act  1808 , the processing device displays the icon at a new location on the touch-sensitive display screen that is removed from the first vertex&#39;s new location by the fixed distance along the direction defined by the axis of the ellipse. The process  1800  proceeds from act  1808  to act  1810 . 
     In act  1810 , the processing device performs a measurement on the ultrasound image based on the ellipse. For example, the processing device may perform a calculation of the spatial length represented by the ultrasound image along the circumference of the ellipse or a calculation of the spatial area represented by the ultrasound image within the ellipse. In some embodiments, the processing device may display the result of the measurement. 
     in some embodiments, certain acts of the process  1800  may be absent. For example, in some embodiments, act  1810  may be absent. In some embodiments, acts  1804 - 1810  may be absent. In some embodiments, acts  1804 - 1808  may be absent. In some embodiments, other combinations of acts may be absent. 
       FIG.  19    illustrates an example process  1900  for performing measurements on an ultrasound image based on an ellipse, in accordance with certain embodiments described herein. Further description of the process  1900  may be found with reference to  FIG.  9   . 
     In act  1902 , the processing device displays, on a touch-sensitive display screen, (1) an ultrasound image, (2) an ellipse having an axis that is either the major or minor axis of the ellipse, wherein the axis extends between a first vertex and a second vertex; and (3) an icon located a fixed distance from the first vertex along a direction defined by the axis. The process  1900  proceeds from act  1902  to act  1904 . 
     In act  1904 , the processing device detects a dragging movement covering distance in the horizontal direction and; or a distance in the vertical direction across the touch-sensitive display screen, where the dragging movement begins in the interior of the ellipse or within a threshold distance of the boundary of the ellipse. The process  1900  proceeds from act  1904  to act  1906 . 
     In act  1906 , the processing device displays the first vertex and the second vertex at new locations on the touch-sensitive display screen that are removed from their previous locations by the distance in the horizontal direction and/or the distance in the vertical direction covered by the dragging movement. The process  1900  proceeds from act  1906  to act  1908 . 
     In act  1908 , the processing device performs a measurement performed on the ultrasound image based on the ellipse. For example, the processing device may perform a calculation of the spatial length represented by the ultrasound image along the circumference of the ellipse or a calculation of the spatial area represented by the ultrasound image within the ellipse. In some embodiments, the processing device may display the result of the measurement. 
     In some embodiments, certain acts of the process  1900  may be absent. For example, in some embodiments, act  1910  may be absent. In some embodiments, acts  1904 - 1910  may be absent. In some embodiments, acts  1904 - 1908  may be absent. In some embodiments, other combinations of acts may be absent. 
     The above description has described that a user may modify measurement tools (e.g., a line or an ellipse) through dragging movements that begin on or within a threshold distance of an icon that is located a fixed distance from a portion of the measurement tool. In some embodiments, one or more of the icons described above may be absent, and a user may modify measurement tools through dragging movements that begin on or within a threshold distance of a region of the touch-sensitive display screen that is located the fixed distance from the portion of the measurement tool, even though the region does not contain an icon. 
     The above description has described modifying measurement tools (e.g., a line or an ellipse) based on a distance in the horizontal and/or vertical direction covered by a dragging movement. In some embodiments, the processing device may modify measurement tools based on taps. In particular, a user may tap an icon and then another location on the touch-sensitive display screen. The processing device may then modify the measurement tool based on the distance in the horizontal and/or vertical direction between the two tapped locations. 
     Various inventive concepts may be embodied as one or more processes, of which examples have been provided. The acts performed as part of each process may be ordered in any suitable way. Thus, embodiments may be constructed in which acts are performed in an order different than illustrated, which may include performing some acts simultaneously, even though shown as sequential acts in illustrative embodiments. Further, one or more of the processes may be combined and/or omitted, and one or more of the processes may include additional steps. 
       FIG.  20    illustrates a schematic block diagram illustrating aspects of an example ultrasound system  2000  upon which various aspects of the technology described herein may be practiced. For example, one or more components of the ultrasound system  2000  may perform any of the processes described herein. As shown, the ultrasound system  2000  includes processing circuitry  2001 , input/output devices  2003 , ultrasound circuitry  2005 , and memory circuitry  2007 . 
     The ultrasound circuitry  2005  may be configured to generate ultrasound data that may be employed to generate an ultrasound image. The ultrasound circuitry  2005  may include one or more ultrasonic transducers monolithically integrated onto a single semiconductor die. The ultrasonic transducers may include, for example, one or more capacitive micromachined ultrasonic transducers (CMUTs), one or more CMOS ultrasonic transducers (CUTs), one or more piezoelectric micromachined ultrasonic transducers (PMUTs), and/or one or more other suitable ultrasonic transducer cells. In some embodiments, the ultrasonic transducers may be formed the same chip as other electronic components in the ultrasound circuitry  2005  (e.g., transmit circuitry, receive circuitry, control circuitry, power management circuitry, and processing circuitry) to form a monolithic ultrasound imaging device. 
     The processing circuitry  2001  may be configured to perform any of the functionality described herein. The processing circuitry  2001  may include one or more processors (e.g., computer hardware processors). To perform one or more functions, the processing circuitry  2001  may execute one or more processor-executable instructions stored in the memory circuitry  2007 . The memory circuitry  2007  may be used for storing programs and data during operation of the ultrasound system  2000 . The memory circuitry  2007  may include one or more storage devices such as non-transitory computer-readable storage media. The processing circuitry  2001  may control writing data to and reading data from the memory circuitry  2007  in any suitable manner. 
     In some embodiments, the processing circuitry  2001  may include specially-programmed and/or special-purpose hardware such as an application-specific integrated circuit (ASIC). For example, the processing circuitry  2001  may include one or more graphics processing units (GPUs) and/or one or more tensor processing units (TPUs). TPUs may be ASICs specifically designed for machine learning (e.g., deep learning). The TPUs may be employed to, for example, accelerate the inference phase of a neural network. 
     The input/output (I/O) devices  2003  may be configured to facilitate communication with other systems and/or an operator. Example I/O devices  2003  that may facilitate communication with an operator include: a keyboard, a mouse, a trackball, a microphone, a touch-sensitive display screen, a printing device, a display screen, a speaker, and a vibration device. Example I/O devices  2003  that may facilitate communication with other systems include wired and/or wireless communication circuitry such as BLUETOOTH, ZIGBEE, Ethernet, WiFi, and/or USB communication circuitry. 
     It should be appreciated that the ultrasound system  2000  may be implemented using any number of devices. For example, the components of the ultrasound system  2000  may be integrated into a single device. In another example, the ultrasound circuitry  2005  may be integrated into an ultrasound imaging device that is communicatively coupled with a processing device that includes the processing circuitry  2001 , the input/output devices  2003 , and the memory circuitry  2007 . 
       FIG.  21    is a schematic block diagram illustrating aspects of another example ultrasound system  2100  upon which various aspects of the technology described herein may be practiced. For example, one or more components of the ultrasound system  2100  may perform any of the processes described herein. As shown, the ultrasound system  2100  includes an ultrasound imaging device  2114  in wired and/or wireless communication with a processing device  2102 . The processing device  2102  includes an audio output device  2104 , an imaging device  2106 , a display screen  2108 , a processor  2110 , a memory  2112 , and a vibration device  2109 . The processing device  2102  may communicate with one or more external devices over a network  2116 . For example, the processing device  2102  may communicate with one or more workstations  2120 , servers  2118 , and/or databases  2122 . 
     The ultrasound imaging device  2114  may be configured to generate ultrasound data that may be employed to generate an ultrasound image. The ultrasound imaging device  2114  may be constructed in any of a variety of ways. In some embodiments, the ultrasound imaging device  2114  includes a transmitter that transmits a signal to a transmit beamformer which in turn drives transducer elements within a transducer array to emit pulsed ultrasonic signals into a structure, such as a patient. The pulsed ultrasonic signals may be back-scattered from structures in the body, such as blood cells or muscular tissue, to produce echoes that return to the transducer elements. These echoes may then be converted into electrical signals by the transducer elements and the electrical signals are received by a receiver. The electrical signals representing the received echoes are sent to a receive beamformer that outputs ultrasound data. 
     The processing device  2102  may be configured to process the ultrasound data from the ultrasound imaging device  2114  to generate ultrasound images for display on the display screen  2108 . The processing may be performed by, for example, the processor  2110 . The processor  2110  may also be adapted to control the acquisition of ultrasound data with the ultrasound imaging device  2114 . The ultrasound data may be processed in real-time during a scanning session as the echo signals are received. In some embodiments, the displayed ultrasound image may be updated a rate of at least 5 Hz, at least 10 Hz, at least 20 Hz, at a rate between 5 and 60 Hz, at a rate of more than 20 Hz. For example, ultrasound data may be acquired even as images are being generated based on previously acquired data and while a live ultrasound image is being displayed. As additional ultrasound data is acquired, additional frames or images generated from more-recently acquired ultrasound data are sequentially displayed. Additionally, or alternatively, the ultrasound data may be stored temporarily in a buffer during a scanning session and processed in less than real-time. 
     Additionally (or alternatively), the processing device  2102  may be configured to perform any of the processes described herein (e.g., using the processor  2110 ). For example, the processing device  2102  may be configured to automatically determine an anatomical feature being imaged and automatically select, based on the anatomical feature being imaged, an ultrasound imaging preset corresponding to the anatomical feature. As shown, the processing device  2102  may include one or more elements that may be used during the performance of such processes. For example, the processing device  2102  may include one or more processors  2110  (e.g., computer hardware processors) and one or more articles of manufacture that include non-transitory computer-readable storage media such as the memory  2112 . The processor  2110  may control writing data to and reading data from the memory  2112  in any suitable manner. To perform any of the functionality described herein, the processor  2110  may execute one or more processor-executable instructions stored in one or more non-transitory computer-readable storage media (e.g., the memory  2112 ), which may serve as non-transitory computer-readable storage media storing processor-executable instructions for execution by the processor  2110 . 
     In some embodiments, the processing device  2102  may include one or more input and/or output devices such as the audio output device  2104 , the imaging device  2106 , the display screen  2108 , and the vibration device  2109 . The audio output device  2104  may be a device that is configured to emit audible sound such as a speaker. The imaging device  2106  may be configured to detect light (e.g., visible light) to form an image such as a camera. The display screen  2108  may be configured to display images and/or videos such as a liquid crystal display (LCD), a plasma display, and/or an organic light emitting diode (OLED) display. The display screen  2018  may be a touch-sensitive display screen. The vibration device  2109  may be configured to vibrate one or more components of the processing device  2102  to provide tactile feedback. These input and/or output devices may be communicatively coupled to the processor  2110  and/or under the control of the processor  2110 . The processor  2110  may control these devices in accordance with a process being executed by the process  2110  (such as the processes shown in  FIGS.  15 - 19   ). Similarly, the processor  2110  may control the audio output device  2104  to issue audible instructions and/or control the vibration device  2109  to change an intensity of tactile feedback (e.g., vibration) to issue tactile instructions. Additionally (or alternatively), the processor  2110  may control the imaging device  2106  to capture non-acoustic images of the ultrasound imaging device  2114  being used on a subject to provide an operator of the ultrasound imaging device  2114  an augmented reality interface. 
     It should be appreciated that the processing device  2102  may be implemented in any of a variety of ways. For example, the processing device  2102  may be implemented as a handheld device such as a mobile smartphone or a tablet. Thereby, an operator of the ultrasound imaging device  2114  may be able to operate the ultrasound imaging device  2114  with one hand and hold the processing device  2102  with another hand. In other examples, the processing device  2102  may be implemented as a portable device that is not a handheld device such as a laptop. In yet other examples, the processing device  2102  may be implemented as a stationary device such as a desktop computer. 
     In some embodiments, the processing device  2102  may communicate with one or more external devices via the network  2116 . The processing device  2102  may be connected to the network  2116  over a wired connection (e.g., via an Ethernet cable) and/or a wireless connection (e.g., over a WiFi network). As shown in  FIG.  21   , these external devices may include servers  2118 , workstations  2120 , and/or databases  2122 . The processing device  2102  may communicate with these devices to, for example, off-load computationally intensive tasks. For example, the processing device  2102  may send an ultrasound image over the network  2116  to the server  2118  for analysis (e.g., to identify an anatomical feature in the ultrasound) and receive the results of the analysis from the server  2118 . Additionally (or alternatively), the processing device  2102  may communicate with these devices to access information that is not available locally and/or update a central information repository. For example, the processing device  2102  may access the medical records of a subject being imaged with the ultrasound imaging device  2114  from a file stored in the database  2122 . In this example, the processing device  2102  may also provide one or more captured ultrasound images of the subject to the database  2122  to add to the medical record of the subject. For further description of ultrasound imaging devices and systems, see U.S. Patent Application Publication No. US20170360397A1 titled “UNIVERSAL ULTRASOUND DEVICE AND RELATED APPARATUS AND METHODS.” 
     Various aspects of the present disclosure may be used alone, in combination, or in a variety of arrangements not specifically discussed in the embodiments described in the foregoing and is therefore not limited in its application to the details and arrangement of components set forth in the foregoing description or illustrated in the drawings. For example, aspects described in one embodiment stay be combined in any manner with aspects described in other embodiments. 
     The indefinite articles “a” and “an,” as used herein in the specification and in the claims, unless clearly indicated to the contrary, should be understood to mean “at least one.” 
     The phrase “and/or,” as used herein in the specification and in the claims, should be understood to mean “either or both” of the elements so conjoined, i.e., elements that are conjunctively present in some cases and disjunctively present in other cases. Multiple elements listed with “and/or” should be construed in the same fashion, i.e., “one or more” of the elements so conjoined. Other elements may optionally be present other than the elements specifically identified by the “and/or” clause, whether related or unrelated to those elements specifically identified. 
     As used herein in the specification and in the claims, the phrase “at least one,” in reference to a list of one or more elements, should be understood to mean at least one element selected from any one or more of the elements in the list of elements, but not necessarily including at least one of each and every element specifically listed within the list of elements and not excluding any combinations of elements in the list of elements. This definition also allows that elements may optionally be present other than the elements specifically identified within the list of elements to which the phrase “at least one” refers, whether related or unrelated to those elements specifically identified. 
     Use of ordinal terms such as “first,” “second,” “third,” etc., in the claims to modify a claim element does not by itself connote any priority, precedence, or order of one claim element over another or the temporal order in which acts of a method are performed, but are used merely as labels to distinguish one claim element having a certain name from another element having a same name (but for use of the ordinal term) to distinguish the claim elements. 
     The terms “approximately” and “about” may be used to mean within ±20% of a target value in some embodiments, within ±10% of a target value in some embodiments, within ±5% of a target value in some embodiments, and yet within ±2% of a target value in some embodiments. The terms “approximately” and “about” may include the target value. 
     Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having,” “containing,” “involving,” and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. 
     Having described above several aspects of at least one embodiment, it is to be appreciated various alterations, modifications, and improvements will readily occur to those skilled in the art. Such alterations, modifications, and improvements are intended to be object of this disclosure. Accordingly, the foregoing description and drawings are by way of example only.