Abstract:
A method comprises the step of determining a minimum length of a lesion based on an imaging modality used to capture an image of the lesion and a slice thickness of the image, generating an extent cursor corresponding to the minimum size of the lesion, the extent cursor having a circular shape with a diameter corresponding to the minimum length and displaying the image of the lesion with the extent cursor positioned thereover.

Description:
BACKGROUND 
       [0001]    The treatment of tumors calls for the imaging of a target treatment area prior to and after administration of a treatment. A comparison of the two or more images is then carried out to assess an efficacy of the treatment. Procedures have been standardized to measure tumors in medical images from computed tomography (CT), magnetic resonance imaging (MRI) and positron emission tomography (PET). One such standardized procedure is response evaluation criteria in solid tumors (RECIST), which defines particular measurement criteria for each of the imaging modalities (e.g., PERCIST for PET, etc.) or tumor entities (e.g., Revised Assessment in Neuro-Oncology (RANO) for brain tumors, etc.). Most standardized procedures require a minimum tumor size, known as a measurable lesion, before response criteria (e.g., treatment) can be applied. In order to assess the dimensions of the tumor, a clinician performs a line measurement of the lesion to determine if it meets the minimum size criteria, known in the art as a “measurable lesion”. This adds time and mouse clicks to the workflow and is operator dependent, thereby increasing the possibility of user error. The radiologist also has to determine a slice thickness of the medical image to determine the minimum measurement criteria that applies thereto. 
       SUMMARY 
       [0002]    A system and method for assessing a lesion comprising the steps of determining a minimum length of a lesion based on an imaging modality used to capture an image of the lesion and a slice thickness of the image, generating an extent cursor corresponding to the minimum size of the lesion, the extent cursor having a circular shape with a diameter corresponding to the minimum length and displaying the image of the lesion with the extent cursor positioned thereover. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0003]    Several embodiments of the invention will be described in the following by way of example and with reference to the accompanying drawings in which: 
           [0004]      FIG. 1  depicts a T 2 W-MRI image of a first lesion having an extent cursor and an extent scale provided thereon; 
           [0005]      FIG. 2  depicts a DWI-MRI image of the first lesion having an extent cursor provided thereon; 
           [0006]      FIG. 3  depicts an MRI image of a second lesion having an extent cursor provided thereon; 
           [0007]      FIG. 4  shows a schematic drawing of a system according to an exemplary embodiment; and 
           [0008]      FIG. 5  depicts a flow diagram of an exemplary method. 
       
    
    
     DETAILED DESCRIPTION 
       [0009]    The exemplary embodiments may be further understood with reference to the following description and appended drawings. The exemplary embodiments propose a system and method for measuring tumors in medical images obtained via CT, MRI, PET, or any other imaging modality known in the art. The exemplary system and method according to the invention provides a method to support a clinician, radiologist or other user in determining if a lesion is measurable (i.e., meets a minimum size criteria) and needs to be further examined or treated. Specifically, the system and method according to the exemplary embodiments provides a mouse cursor over the medical image, the mouse cursor conforming to a minimum dimension of a measurable lesion according to the selected standard (e.g., RECIST, PERCIST, etc.). The minimum extent of the mouse cursor is automatically selected by a computing device based on the type of imaging modality being used, a slice thickness of the image and any other criteria which may be useful including, but not limited to patient-specific data. The mouse cursor is displayed on a screen as one or both of an “extent cursor” displayed as a circular representation enclosing the lesion therein and an “extent scale” displayed as a scale bar of minimum extent length, as will be described in greater detail later on. The radiologist or other user uses the extent cursor or extent scale to quickly and accurately make an assessment of the lesion and diagnose the patient. 
         [0010]    The exemplary embodiment is described in greater detail with respect to  FIGS. 1-4 .  FIG. 1  depicts a first image  100  corresponding to a T 2 -weighted MRI image of a liver lesion  120  captured with a 5 mm. slice thickness. The first image  100  is displayed on a display screen  408  of an exemplary system  400 . A processor  406  of the system  400  automatically displays a first extent cursor  110  that may be moved in the display space represented by the first image  100 . In an exemplary embodiment, the first extent cursor  110  is formed as a circular representation having a diameter conforming to a minimum diameter of a measurable lesion for a T 2 -weighted MRI image captured with a 5 mm. slice thickness. In this example, the measurable lesion must meet or exceed a diameter of 10 mm. Thus, the first extent cursor  110  is formed as a circle having a 10 mm. diameter. The first extent cursor  110  is displayed over the first image  100  in a region containing a lesion of interest  120 . In one exemplary embodiment, the first extent cursor  110  may be automatically displayed in a previously input region of interest (e.g., corresponding to a location of the lesion  120  determined during an earlier imaging procedure). In another embodiment, the first extent cursor  110  may be manually positionable by the radiologist or other user over one or more lesions  120  displayed on the first image  100 . 
         [0011]    The first extent cursor  110  is provided in a predetermined, nonadjustable size. A color, line style and line thickness of the first extent cursor  110  may be selected to aid in viewing thereof over the first image. For example, the first extent cursor  110  may be formed with a solid line or dotted line. A color of the first extent cursor  110  is selected to contrast against a color of the first image  100  and may, for example, be red, blue, white, black or any other suitable color. In one exemplary embodiment, the radiologist or other user may change the color, line style or line thickness of the first extent cursor  110  via a user interface  410 . The first extent cursor  110  may be automatically displayed on the display  408  or, in another embodiment, may be displayed only after prompted via the user interface  410 . Still further, the radiologist may optionally display and remove the first extent cursor  110  via the user interface  410  to, for example, examine the lesion  120 . In such an embodiment, the first extent cursor  110  is displayed on the same region of the first image  100 , regardless of whether the first image  410  is resized, rotated, zoomed, etc. The radiologist may examine dimensions of the lesion  120  relative to the first extent cursor  110  and determine if the lesion  120  is equal to or greater than the minimum size requirement to qualify as a measurable lesion. In the present example, the lesion  120  is sufficient to be measurable. 
         [0012]    In another embodiment, the first image  100  may be provided with an extent scale  140  that is shown on a lower border of the first image  100 . It is noted that although the extent scale  140  is depicted on a lower border of the first image  100 , the extent scale  140  may be provided along any border or anywhere else on the first image  100  without deviating from the scope of the disclosure. In another embodiment, the extent scale  140  may be positioned adjacent to the first lesion  120  to aid in assessing a size thereof. In one embodiment, the extent scale  140  may be locked to a predetermined position on the displayed first image  100 . In another embodiment, the extent scale  140  may be movable by the radiologist or other user to any desired location on the first image  100  and subsequently optionally locked in place. The extent scale  140  may be formed with a length corresponding to the minimum length of the measurable lesion. The extent scale may optionally also include a label (not shown) indicating a length thereof. Line properties of the extent scale  140  may be similar to those described above with respect to the first extent cursor  110  and may also be adjusted by a user via the user interface  410 . The extent scale  140  may further be rotated via the user interface  410  to aid in measurement of the lesion  110 , as those skilled in the art will understand. The first image  100  may be displayed with one or both of the first extent cursor  110  and the extent scale  140  automatically or upon being prompted via the user interface  410 . 
         [0013]      FIG. 2  depicts a second image  200  according to another embodiment, the second image  200  corresponding to a diffusion weighted imaging (DWI) MRI of a liver lesion acquired with a 7 mm. slice thickness. A lesion  220  is highlighted by a second extent cursor  210 , which has a diameter of 14 mm. The second extend cursor  210  clearly has a larger diameter than the lesion  210 , thus indicating that the lesion  210  is not measurable in DWI MRI. 
         [0014]      FIG. 3  depicts a third image  300  according to another embodiment including a brain lesion  320  and a third extent cursor  320 . The third extent cursor  320  is displayed as a white circular representation. 
         [0015]    In another embodiment, the radiologist or other user may scroll through two or more images to assess a change in a lesion over time. In this embodiment, the extent cursor  110 ,  210 ,  310  may remain in position over the lesion  120 ,  220 ,  320  while the user toggles between the plurality of images. The plurality of images may also be displayed side by side on a single display with their respective extent cursors and/or extent scales to aid in a visual comparison thereof. 
         [0016]      FIGS. 4-5  depict the exemplary system  400  and method  500  according to the disclosure. In a first step  502 , an image  100 ,  200 ,  300  is captured and stored on a database  402  of a memory  404 . As those skilled in the art will understand, the capturing step  502  may be optionally omitted and a processor  406  may reference an image  100 ,  200 ,  300  previously stored on the database  402 . In step  504 , the processor  406  determines a minimum extent of a lesion based on the imaging modality used and the slice thickness thereof. The processor  406  may use an algorithm to determine the minimum extent as defined by tumor response standards. Specifically, for RECIST 1.1, the extent of a tumor lesion is determined as follows:
       for CT and MRI: ≧min (10 mm, 2×(slice thickness+slice gap))   for chest x-ray: ≧20 mm   for lymph node assessment: ≧15 mm
 
For brain tumors (RANO criteria), two perpendicular diameters of the minimum extent have to be present. However, the minimum extent itself is determined with the same criteria as noted above with respect to RECIST. It is noted that although the present embodiment has been described with respect to a predetermined algorithm defining requirements of the measurable lesion, any other standards may be used without deviating from the scope of the disclosure. In one example, a radiologist or other user may manually enter, via the user interface  410 , the minimum length of the lesion. In particular, the user may override the automatically determined extent if necessary. Furthermore, details of the image  100 ,  200 ,  300  including imaging modality and slice thickness may be derived from the image data (e.g., via DICOM tags) itself or may also be manually entered by the user.
       
 
         [0020]    In step  506 , the processor  406  generates one or both of the extent cursor  110 ,  210 ,  310  and the extent scale  140 . In step  508 , the processor  406  displays the image  100 ,  200 ,  300  with the corresponding extent cursor  110 ,  210 ,  310  and/or extent scale  140  on a display  408 . A radiologist or other user may manipulate, scroll through or otherwise edit any of the images  100 ,  200 ,  300  via the user interface  410  which may include any of a keyboard, mouse and/or a touch display on the display  408 . The user may also change the display to view a different image other than the image  100 ,  200 ,  300  for which the extent cursor  110  was formulated. To enforce RECIST guidelines, additional consistency checks and warnings may optionally be imposed as in optional step  510 . Specifically, the minimum extent of the lesion is defined in the acquired 2D imaging plane. Therefore, the extent cursor  110 ,  210 ,  310  and extent scale  140  are only shown for in-plane viewing. In step  510 , the processor  406  determines if other views (e.g., reformatted views) are currently being displayed on the display  408 . If so, the method moves to step  512  wherein the extent cursor  110 ,  210 ,  310  is removed from the display and a warning is displayed to the user indicating that the extent cursor  110  is not applicable to the image currently being viewed. 
         [0021]    The exemplary system and method disclosed herein may be employed with several commercial software products (e.g., Philips IntelliSpace—Tumor Tracking, Mint Lesion, etc.) 
         [0022]    Although the invention has been described with two-dimensional imaging, any other image analysis technique may be used without deviating from the scope of the invention. For example, the image analysis may include 3-dimensional imaging wherein the extent cursor may comprise a sphere positioned in the 3-dimensional representation. 
         [0023]    It will be appreciated by those skilled in the art that various modifications and alterations of the invention can be made without departing from the broad scope of the appended claims. Some of these have been discussed above and others will be apparent to those skilled in the art.