Abstract:
A method, system, and computer program product for providing textual ultrasound probe position information corresponding to an ultrasound image of a target is described. Based on a user&#39;s graphical manipulations of a probe icon relative to a breast icon, a text sequence corresponding to the user&#39;s estimate of the position of an ultrasound probe is automatically generated. User error and fatigue are reduced because manual keying of the probe position text sequence is no longer required, and the resulting outputs are standardized in format and therefore more amenable to archiving and electronic analysis. In one preferred embodiment, the user is permitted to select a snapping mode of operation in which the probe icon is snapped to align with a major direction of a preselected coordinate system, further enhancing ease-of-use and reducing user fatigue.

Description:
FIELD 
     This patent specification relates to medical ultrasound imaging systems. In particular, it relates to an easy-to-use user interface that promotes consistent and reliable recordation of probe position during a breast ultrasound scan. 
     BACKGROUND 
     Ultrasound imaging systems have become increasingly popular for use in medical diagnosis because they are non-invasive, easy to use, capable of real-time operation, and do not subject patients to the dangers of electromagnetic radiation. Instead of electromagnetic radiation, an ultrasound imaging system transmits sound waves of very high frequency (e.g., 1 MHz to 15 MHz) into the patient and processes echoes scattered from structures in the patient&#39;s body to derive and display information relating to these structures. 
     Ultrasound imaging systems have been increasingly used in breast cancer screening, detection, treatment, and research. Most commonly, a breast ultrasound procedure involves the placement of an ultrasound probe over a region of interest of the breast, with the radiologist or other medical professional (hereinafter “user”) simultaneously viewing a real-time ultrasound image output on a computer monitor. The monitor also usually displays relevant text and/or graphical information near the ultrasound image for simultaneous viewing by the user. The user then presses a button to freeze the display, at which time the display may be printed on a printer or stored in digital format for later viewing and analysis. 
     Because much downstream analysis, interpretation, and decisionmaking may be performed based on the printed or stored information, it is crucial to ensure that the text annotation and/or graphical information relevant to the ultrasound image be both correct and properly formatted. As PACS (picture archiving and communication systems) and teleradiology (i.e., the calling up of archived images from remote locations by telephone line or internet connection) continue to increase in importance, the accurate and consistent annotation of ultrasound and other medical images will become increasingly important. Additionally, it is expected that accurate and consistent annotation of ultrasound and other medical images will become increasingly important as historical archives of breast ultrasounds and other medical images are built up over time for statistical analysis or other research purposes. 
     FIG. 1 shows a conventional ultrasound display  100  comprising an ultrasound image  102 , a body marker region  104 , other ultrasound parameters  106 , and a user-typed text string  108 . Body marker region  104  has the important purpose of illustrating to a subsequent viewer the position of the ultrasound probe when the ultrasound image  102  was taken. Body marker region  104  comprises left and right breast icons  110  and  112 , respectively, against which a movable probe icon  114  is manipulated by the user to reflect the current position of the ultrasound probe. Most commonly, a trackball input is used to manipulate the location of probe icon  114  relative to the breast icons, while a probe orientation knob is rotated to manipulate the orientation of the probe icon  114  relative to the breast icons. Other ultrasound parameters  106  is a text display of relevant parameters such as time, date, probe power, frame rate, etc. 
     User-typed text string  108 , shown in FIG. 1 by the characters “ph lesion” (representing the term “phantom lesion”), is input by the user by positioning a freely movable text cursor, using a trackball, to the relevant location on the ultrasound output  100  and then entering the relevant text portion. This is usually done to point out certain aspects of the ultrasound image  102  that may be interesting to a subsequent viewer but that may, or may not, be immediately apparent to the subsequent viewer. 
     Finally, ultrasound display  100  comprises a probe position text sequence  116  placed within the body marker region  104 . In conventional systems, the probe position text sequence  116  is typed in by the user, using the same or similar text input mode that is used to enter the user-typed text string  108 . The probe position text sequence  116  is shown in FIG. 1 as having been only partially input, with a cursor moving to the right as it is typed in by the user. The probe position text sequence  116  is intended to textually communicate the position of the ultrasound probe as graphically expressed by the location and orientation of the probe icon  114 . As used herein, the term “location” refers to the x-y placement of the ultrasound probe/probe icon (and also the z coordinate if applicable). The term “orientation” refers to the direction in which probe icon/ultrasound probe transducer array is pointed. The term “position” refers to the collective location and orientation information. 
     As known in the art, typical examples of probe position text sequence  116  may include: (i) “Left BR, Antiradial, 1:30, 3 cm,” meaning that the probe is over the left breast, is at a radius of 3 cm from the left nipple at an angle of 1:30 (i.e., 45 degrees from vertical using clock coordinates), and has an orientation in the antiradial direction (i.e., is tangent to a circle centered on the left nipple at the 1:30 location); (ii) “Left BR, Radial, 6:00, 5 cm,” meaning that the probe is located over the left breast 5 cm directly below the left nipple and is oriented in the radial direction, (iii), “Right BR, Trans, 10:00, 4 cm,” meaning that the probe is located over the right breast at 4 cm in the 10:00 direction from the right nipple and is oriented in the transverse direction (i.e., parallel to a line between the two breast nipples), (iv) “Right BR, Long, 7:00, 8 cm,” meaning that the probe is over the right breast at 8 cm in the 7:00 direction and is oriented in the longitudinal direction (i.e., parallel to the longitudinal or sagittal axis of the body), and (v) “Left BR, Oblique, 8:00, 3 cm” meaning that the probe is over the left breast at 3 cm in the 3:00 direction, and is not oriented along any standard direction. As known in the art, examples (i) and (ii) above express the orientation of the probe with respect to a radial/antiradial coordinate system, while examples (iii) and (iv) express the orientation of the probe with respect to a transverse/longitudinal coordinate system. In general, the “oblique” designation in example (v) may be used with either the radial/antiradial or transverse/longitudinal coordinate system. 
     One problem that arises with the system of FIG. 1 is that the user is required to alphanumerically key in the probe position text sequence  116  when such text is desired. This process can be cumbersome, can lead to user frustration, and, when many breast ultrasound scans are being recorded, can lead to user fatigue. Sonographers must routinely manipulate the ultrasound probe with one hand and operate the ultrasound system controls and keyboard with the other. The hand that manipulates the probe is often times gloved and/or encumbered by having ultrasound gel on it. With interventional procedures including biopsies and ductography, contamination may occur from blood and/or nipple discharge as well. Conventional annotation mechanics that require any keyboard entries mean that the operator either has to stop, wipe their hands, and then type with both hands, or, use a keyboard designed for two hands with a single hand. Further, unless the operator truly goes to the sink and washes thoroughly and carefully before typing on the keyboard, there is the potential for contamination of the keyboard with pathogens such as fomites. These could be passed on to later patients by the operator. Also, there is the potential for damage of the equipment by moisture from the ultrasound gel deposited on the keyboard and controls. 
     Moreover, any delays incurred while typing in the probe position text sequence  116  can lead to the possibility that the ultrasound probe may have moved slightly in the meantime. Due to frustration, fatigue, or other factors, the user may return to properly adjust the probe icon  114  and the probe position text sequence  116 . This can result in decreased correlation between the ultrasound image and the supporting information the printed or digitally stored copy. 
     Another disadvantage of the system of FIG. 1 is that different users may incorporate different text schemes for entering the probe position text sequence  116 , or the same user may use different text schemes at different times. As a result, different ultrasound output pages from the same laboratory or even the same user may differ in the format of their probe position text sequences. Especially in environments in which such information would be digitally stored, this is disadvantageous because it makes statistics gathering or other off-line automated analysis difficult to achieve across large volumes of ultrasound outputs. Given the potential future usefulness of such information in tracking historical data associated with different patients or populations, it may be important to ensure uniformity in the probe position text sequences of ultrasound output pages. 
     Finally, another disadvantage of the system of FIG. 1 is that even the purely graphical manipulation of the probe icon  114  may be cumbersome if the user wished the ultrasound probe position to remain in a major direction. For example, if the user is recording two successive ultrasound frames in the antiradial orientation at two different locations, then after the first frame the user must move the trackball until the probe icon is at the second location, and then must carefully re-manipulate the probe orientation knob until the probe icon is oriented in the antiradial direction. This process is unnecessarily cumbersome when it is already known that the probe icon should be in the antiradial direction at the second location. 
     While a completely automatic position sensing system might represent one option for providing an automatic recording of probe position information, including text-based information, it has been found that position sensing equipment can be cumbersome to use in clinical applications. Moreover, the accuracy of such systems can be reduced because the patient&#39;s breast nipples, used as reference points in the probe position display, often move around during the ultrasound procedure. This reduces the usefulness of the position sensor readouts as replacements for the medical professional&#39;s own estimation of probe position. 
     Accordingly, it would be desirable to provide an ultrasound system that is easier to use in terms of the textual recordation of user estimates of ultrasound probe position. 
     It would be further desirable to provide an ultrasound system that is easier to use in terms of orientating a probe icon along major directions while manipulating the probe icon. 
     It would be still further desirable to provide an ultrasound system that promotes uniformity in the formatting of probe position text sequence outputs. 
     It would be even further desirable to provide an ultrasound system for which the user can functionally operate the controls efficiently and ergonomically with one hand. 
     SUMMARY 
     In accordance with a preferred embodiment, a method and system for providing ultrasound probe position information corresponding to an ultrasound image of a target are provided, wherein a text sequence corresponding to a user&#39;s estimate of the position of an ultrasound probe is automatically generated based on the user&#39;s graphical manipulations of a probe icon relative to a breast icon. User inputs are received through a trackball, knob, mouse, or other graphical input device and used to adjust the position of the probe icon relative to the breast icon. The probe position text sequence is automatically generated and continuously updated as the probe icon is manipulated. Because the user is no longer required to manually key in their estimate of the probe position, they may concentrate more easily on accurate placement of the probe icon on the ultrasound display. Moreover, user fatigue associated with repeated keypad entries is avoided. Additionally, probe position text sequences are generated in a common format without unnecessary truncations or misspellings, thereby being more amenable to digital archiving and subsequent computerized access and analysis. 
     In one preferred embodiment, the user is permitted to select a snapping mode of operation in which the probe icon is snapped to align with a major direction of a preselected coordinate system. In one particular preferred embodiment, this snapping mode is automatically associated with the user&#39;s selection of a radial/antiradial coordinate system, for which this snapping mode has been found to be particularly useful and convenient. If the preselected coordinate system is the transverse/longitudinal coordinate system, this snapping mode is not automatically activated, for permitting a large range of oblique orientations to be recorded. 
     In another preferred embodiment, the user is permitted to select a classification mode of operation in which the location of the probe icon is automatically classified into one of a plurality of standardized zones based on its position with respect to a reference point, such as a nipple of the patient&#39;s breast. A text representation of this zone is included in the probe position text sequence. Optionally, the user is permitted to select a manual override mode of operation in which the probe position text sequence may be altered or appended by the user. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 illustrates a prior art ultrasound display output; 
     FIG. 2A illustrates an exterior view of an ultrasound system in accordance with a preferred embodiment; 
     FIG. 2B illustrates a functional block diagram of an ultrasound system in accordance with a preferred embodiment; 
     FIGS. 3A-3D illustrate a body marker portion of an ultrasound display output in accordance with a preferred embodiment; 
     FIG. 4 illustrates steps for recording probe position during a breast ultrasound scan in accordance with a preferred embodiment; and 
     FIG. 5 illustrates an input screen for setting alphanumeric probe position display parameters in accordance with a preferred embodiment. 
    
    
     DETAILED DESCRIPTION 
     FIG. 2A illustrates an exterior view of an ultrasound system  200  in accordance with a preferred embodiment, the ultrasound system  200  being amenable for recording probe positions during breast ultrasound scans in accordance with a preferred embodiment. In one preferred embodiment, the ultrasound system  200  is similar to an ultrasound system currently named the USI-2000™ available from U-Systems, Inc. of San Jose, Calif. It is to be appreciated, however, that many ultrasound system architectures may be readily adapted for use in accordance with the preferred embodiments. 
     Ultrasound system  200  comprises a chassis  202  for housing ultrasound processing hardware, an ultrasound probe  204 , a monitor  206 , and a user interface platform  208 . User interface platform  208  comprises a keyboard  210 , a trackball  212 , a series of rotatable knobs including a probe orientation knob  214 , and a plurality of user buttons or keys including a body marker key  216  and a set key  218 . 
     FIG. 2B illustrates a functional block diagram of an ultrasound system  250  that generally corresponds to the ultrasound system  200  of FIG.  2 A. Ultrasound system  250  comprises a transducer  252 , a transmit beamformer  254 , a receive beamformer  256 , a demodulator  258 , a packetizer  260 , a digital signal processing (DSP) subsystem  262 , a system controller  264 , a protocol interface  266 , a host computer  268 , a user interface  270 , and a display  272 . Although many ultrasound system architectures may be readily adapted for use in accordance with the preferred embodiments, ultrasound system  250  is preferably similar to the those described in the commonly assigned U.S. Ser. No. 09/224,635, filed Dec. 31, 1998, and U.S. Ser. No. 09/449,095 filed Nov. 24, 1999, which are incorporated herein by reference, or to the USI-2000™ system, supra. 
     Transducer  252  comprises an array of transducer elements that transmits focused acoustic signals into a target responsive to signals generated by the transmit beamformer  254 . Responsive to control signals and parameters received from system controller  264 , transmit beamformer  254  generates signals that are converted into acoustic interrogation signals by transducer  252  and introduced into the target. Transducer  252  also receives acoustic echoes from the target and converts them into signals for forwarding to receive beamformer  256 . Receive beamformer  256  receives the signals and converts them into a single-channel RF signal. Demodulator  258  receives the single-channel RF signal and generates component frames therefrom, which are then packetized by packetizer  260  and fed to DSP subsystem  262 . DSP subsystem  262  performs any of a variety of image processing algorithms on the packetized component frames (e.g., filtering, image compounding, segmentation, etc.) in accordance with the flexible, programmable architecture of the ultrasound system  250 . The output image data is transferred to protocol interface  266 , but may optionally be further processed by system controller  264 . The compound output image frames are then transferred to host computer  268  which performs scan conversion on the signals for transmission to user interface  270  and ultimate display by display  272 . 
     In one preferred embodiment, the host processor  268  and user interface  270  comprise off-the-shelf Intel-based hardware running a Windows NT operating system, and execute instructions compiled from one or more programs written in the C++ programming language to achieve the functions described herein. However, it is to be appreciated that probe position detection and recording in accordance with the preferred embodiments may be implemented on any of a variety of computing platforms. Indeed, in one preferred embodiment, probe position detection and recording may even be implemented on a computer system separate from the ultrasound system  250 , provided that the user may simultaneously view their respective outputs, and provided that hardcopy or digital storage outputs of the separate systems may be properly associated with each other. Given the present disclosure, a person skilled in the art will be readily able to implement a computer program or group of programs for achieving the functionalities described herein. 
     FIGS. 3A-3D show a body marker region  300  of an ultrasound display in accordance with a preferred embodiment. Body marker region  300  comprises a right breast icon  302 , a left breast icon  304 , a probe icon  306 , and a probe position text sequence  308 . In accordance with a preferred embodiment, probe position text sequence  308  is automatically and continuously generated and displayed based on the position of the probe icon  306 . Probe icon  306 , in turn, is manipulated by the user through trackball  212  and probe orientation knob  214  according to the user&#39;s estimate of the position of the actual ultrasound probe, which the user is usually holding in their other hand. Probe position text sequence  308  is generated using conventional geometrical principles together with a scaling factor that scales distances on the body marker region  300  to actual physical distances on the patient&#39;s body. Usually, a fixed approximation that the breast nipples are separated by about 30 cm will suffice for computing the scaling factor, although this distance may be user-settable. 
     FIGS. 3A-3D represent a sequence of configurations of the body marker region  300  as the user changes the location of the probe icon  306  from its location in FIG. 3A to its location in FIG. 3D, with the user having chosen a radial/antiradial mode of operation. In this mode of operation, the probe icon  306  is automatically snapped to the closer of the radial or antiradial direction prior to display and prior to computation of the probe position text sequence  308 . If the location remains fixed while the user turns the probe orientation knob  214  continuously, the probe icon  306  will remain fixed in its orientation (radial or antiradial) as the probe orientation knob  214  subtends a small arc around its current position. However, when a threshold arc is reached, the probe icon  306  will snap ninety degrees to align with the next major direction (antiradial or radial, respectively). 
     In the example of FIGS. 3A-3D, the probe icon  306  begins in a radial orientation at 2:00 in FIG. 3A, and the user moves the trackball to the right and slightly up such that the probe icon remains generally along the 2:00 direction with respect to the nipple of the right breast icon  302 . As the probe icon  306  moves, the probe position text sequence  308  continuously changes (see FIGS. 3B and 3C) to reflect its current position. In accordance with a preferred embodiment, the text sequence portion corresponding to the angular location only changes by preselected increments, e.g. in ½ hour or 1 hour increments. This is in recognition that the precision of the user&#39;s estimation of the angular location of the ultrasound probe will usually not be finer than these amounts. Thus, while the angular location of the probe icon  306  with respect to the nipple of the right breast icon  302  may wander somewhat from the precise 2:00 direction, the text will still read 2:00. 
     In the example of FIGS. 3A-3D, the orientation of the probe icon  306  remains snapped to the radial direction. If the initial orientation of the probe icon  306  were in the antiradial direction, the antiradial orientation would remain regardless of probe icon location, the probe icon  306  rotating on its own so that it faces the nipple of the right breast icon. The probe icon  306  will continue to do so until the user turns the probe orientation knob  214  by an amount sufficient to snap the probe icon  306  to the radial direction. This feature has been found to particularly enhance ease-of-use of the system by reducing the required manipulation of the probe orientation knob when the user wishes the ultrasound probe to remain aligned with a major (radial/antiradial) direction. 
     In contrast, where the transverse/longitudinal mode is selected, the probe orientation will remain fixed with respect to the output display screen unless probe orientation knob  214  is turned. Different amounts, increments, and directions of snapping may of course be implemented without departing from the scope of the preferred embodiments. 
     FIGS. 3C-3D show the crossover of the probe icon  306  from the right breast to the left breast. In accordance with a preferred embodiment, ultrasound system  200  automatically detects which breast icon nipple is nearer to the probe icon  306 , and uses that nipple as the reference point for generating the probe position text sequence  308 . As the probe icon  306  changes over to the left breast coordinate system, it is automatically rotated and snapped to its new radial orientation (from 2:00 to 10:00). 
     FIG. 4 illustrates steps taken in a method for recording probe position during breast ultrasound scans in accordance with a preferred embodiment. At step  402 , the user presses the body marker key  216  to enter into the auto text mode. At this point, the probe position text sequence will begin to continuously appear in an updated fashion in the body marker region. At step  404 , ultrasound system  200  receives location control and orientation control inputs using the graphical inputs described supra. If the user has selected the radial/antiradial mode in a setup screen described infra, the probe icon will be snapped to the nearest radial or antiradial orientation (steps  406  and  408 ). At steps  410  and  412 , the probe icon is displayed along with the automatically-computed probe position text sequence. At step  414 , if a set command is not received, further graphical user inputs are received at step  404 . If a set command is received at step  414 , step  416  is executed in which the probe icon and probe position text sequence are frozen, and the auto text mode is exited at step  418 . At this point, the user may invoke a print command or other output command to cause the screen ensemble to be printed on a printer or digitally stored. In one preferred embodiment, the user may be given the option, before or after exiting the auto text mode, of altering or appending the probe position text sequence. 
     FIG. 5 shows an auto text setup screen  500  in accordance with a preferred embodiment, comprising an activation toggle  502 , a coordinate system selection column  504 , an angular location precision selection column  506 , and a set button  508 . Auto text setup screen  500  conveniently allows the user, using a conventional personal-computer-like display with a mouse icon  501 , to enable/disable the auto text feature, and to pre-select the desired settings among coordinate system options and angular location precision options described supra. 
     In an optional preferred embodiment, the user is permitted to select a classification mode of operation in which the location of the probe icon is automatically classified into one of a plurality of standardized zones based on its position with respect to the reference point, such as a nipple of the patient&#39;s breast. A text representation of the zone is then included in the probe position text sequence. By way of example and not by way of limitation, some users prefer the annotation of Zone 1, 2, and 3 to represent successive concentric rings having widths of one-third of the radius of the breast, with Zone 1 being nearest the nipple and zone three being farthest from the nipple. A typical probe position text might read “Left BR, Antiradial, 8:00, 6 cm, Zone 2” or simply “Left BR, Antiradial, 8:00, Zone 2.” 
     In another optional preferred embodiment, the zone classification may also include depth information. Most commonly, this depth information would apply to a particular lesion or other important feature appearing in the ultrasound image. For example, a depth classification A, B, or C may be added to represent the anterior third, middle third, or posterior third of the region between the skin surface of the patient&#39;s breast and the pectoral muscle underneath the patient&#39;s breast. Several different methods may be used to generate this data point. In a first example, ultrasound system settings corresponding to a focus depth may be imported to compute the depth classification, it being assumed that the user will cause the lesion to be placed at the focus depth. In a second example, the user would manipulate two cursor marks superimposed on the ultrasound image itself, one at the center of the lesion and the other at the surface of the pectoral muscle. The ultrasound system would then automatically compute the proper depth classification. In a third example, a vertical profile icon having a top marker representing the skin surface and a bottom marker representing the pectoral muscle may be displayed adjacent to the breast body marker supra. The user may then place a cursor at the appropriate place between the top and bottom markers of the vertical profile icon, whereby the ultrasound system may then automatically compute a depth classification A, B, or C. The second and third examples recognize the fact that the depth of the pectoral muscle differs from patient to patient depending on their breasts size and other factors. By way of example, in this embodiment, a typical probe position text sequence might read “Left BR, Antiradial, 8:00, 6 cm, Zone 2B” or simply “Left BR, Antiradial, 8:00, Zone 2B”. 
     Advantageously, a system according to the preferred embodiments makes accurate and fast annotation possible with one hand. Among other benefits, this allows the operator to keep their gloved, scanning hand away from the ultrasound machine once the patient demographics have been entered and the examination has begun. This minimizes the potential for contamination of the ultrasound unit and the spread of pathogens from patient to patient. In additional to cleanliness benefits, both ergonomics and biomechanical efficiency are improved. Because there is less typing involved overall, the likelihood of biomechanical injury that can result from repetitive keyboard entry (e.g., carpal tunnel syndrome) is reduced. 
     Whereas many alterations and modifications of the present invention will no doubt become apparent to a person of ordinary skill in the art after having read the foregoing description, it is to be understood that the particular embodiments shown and described by way of illustration are in no way intended to be considered limiting. For example, while presented supra in the context of breast ultrasound scans, the preferred methods for recording ultrasound probe position are readily adaptable to other ultrasound applications, including pre-natal ultrasound applications, other medical ultrasound applications, non-medical ultrasound applications (e.g., for manufacturing quality control, etc.), and other medical imaging applications. Additionally, the features and advantages of the preferred embodiments are readily adaptable for wider use with PACS and teleradiology systems, supra, where images acquired elsewhere are to be further annotated on a remote workstation using a keyboard, perhaps at the time of interpretation. Therefore, reference to the details of the preferred embodiments are not intended to limit their scope, which is limited only by the scope of the claims set forth below.