Abstract:
An apparatus is configured to deliver destructive energy to a stone. The apparatus includes a detector operative to obtain image data from the stone, a generator operating according to one or more producing parameters for producing the destructive energy, and a video processor unit receiving the image data from the detector. The video processor unit is operative to analyze the image data to determine a displacement of the stone relative to a previous location of the stone. A controller linked to the video processor unit and to the generator is operative to vary the one or more producing parameters of the generator responsively to the displacement of the stone. Methods carried out by the apparatus are further provided.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to removal of calculi from the body. More particularly, this invention relates to intracorporeal comminution of urinary calculi. 
         [0003]    2. Description of the Related Art 
         [0004]    Nowadays, lithotripsy for urinary stones can be carried out by extracorporeal shockwave lithotripsy or endoscopically. The latter approach is known as intracorporeal lithotripsy. Intracorporeal lithotripsy may be conducted by flexible or rigid ureteroscopy or percutaneous nephrolithotomy. Intracorporeal lithotripsy is typically accomplished using laser energy. However, other technologies such as ballistic lithotripsy, ultrasonic lithotripsy and electrohydraulic lithotripsy are applied by instrumentation of the urinary tract. 
         [0005]    Current instruments for intracorporeal lithotripsy have several disadvantages: 
         [0006]    There is poor control of the outcome. By trial and error, the urologist must manually adjust the power settings, activate the instrument, and determine that the desired outcome for the case at hand has resulted. This process is usually iterated, thereby prolonging the procedure. In addition, the parameters available for change by the urologist are limited. Moreover, there is frequently no clear relation between the instrument settings and the effect on the calculus being treated. 
         [0007]    Stone migration away from the endoscope, known as retropulsion, is a generally undesirable effect of lithotripsy. Retropulsion creates a need to further adjust or reposition the instrument, which prolongs the procedure and increases its cost. Moreover, in the case of ureteroscopy, migration of the stone up the ureter might result in its entering the renal pelvis, which could necessitate the use of another piece of equipment to complete the procedure, thereby increasing costs and possibly increasing morbidity. 
         [0008]    Fragmentation of the stone is a desirable effect of lithotripsy. However, conventional techniques and instruments provide limited and inefficient control over the size of the stone fragments. Typically, fragments of various sizes break off from the main body of the stone. As a rule of thumb, stone fragments, which are bigger than 2 mm must be treated either by extraction or by further fragmentation. Smaller fragments are desirable, as they may be left in place. Currently, in the case of endoscopy, the urologist can only estimate the stone size by comparing the stone with the laser fiber, which has a known diameter in the image. Such estimates may be inaccurate. 
         [0009]    There is a tradeoff between increasing power settings, which results in more fragmentation but with a greater degree of stone migration. Furthermore, increasing the power tends to produce larger fragments. Therefore, the urologist must make a compromise. 
       SUMMARY OF THE INVENTION 
       [0010]    According to disclosed embodiments of the invention, methods and systems are provided for controlling the power parameters of an intracorporeal lithotripsy device in order to achieve a desired comminution of a calculus without the undesirable effects noted above. 
         [0011]    There is provided according to embodiments of the invention a medical apparatus configured to deliver destructive energy to a stone. The apparatus includes a detector operative to obtain image data from the stone, a generator operating according to one or more producing parameters for producing the destructive energy, a video processor unit receiving the image data from the detector, wherein the video processor unit is operative to analyze the image data to determine a displacement of the stone relative to a previous location of the stone after the device has been actuated. The apparatus includes a controller linked to the video processor unit and to the generator, the controller being operative to vary the one or more producing parameters of the generator responsively to the displacement of the stone. 
         [0012]    According to one aspect of the apparatus, the video processor unit is programmed to issue an alert when the displacement exceeds a displacement threshold. 
         [0013]    According to a further aspect of the apparatus, the video processor unit is programmed to calculate a rate of movement of the stone, and to issue a motion alert when the rate of movement exceeds a velocity threshold. 
         [0014]    According to still another aspect of the apparatus, the video processor unit is operative to determine that a change in a number of fragments of the stone has occurred. 
         [0015]    According to an additional aspect of the apparatus, the device comprises an endoscope, and the destructive energy comprises a laser beam. 
         [0016]    According to another aspect of the apparatus, the destructive energy comprises acoustic energy. 
         [0017]    There is further provided according to embodiments of the invention a method, which is carried out by determining a first location of a stone within the body of a subject, directing destructive energy toward the stone, thereafter determining that a migration of the stone to a second location has occurred. The method is further carried out by establishing new parameters for the energy responsively to a difference between the second location and the first location, and iterating directing destructive energy using the new parameters. 
         [0018]    According to one aspect of the method, directing destructive energy is performed using an endoscope, and the destructive energy is a laser beam. 
         [0019]    According to yet another aspect of the method, directing destructive energy is delivered using an extracorporeal lithotripter, and the destructive energy is acoustic energy. 
         [0020]    According to a further aspect of the method, determining a first location and determining that a migration of the stone has occurred includes optical imaging of the stone. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0021]    For a better understanding of the present invention, reference is made to the detailed description of the invention, by way of example, which is to be read in conjunction with the following drawings, wherein like elements are given like reference numerals, and wherein: 
           [0022]      FIG. 1  is a pictorial schematic diagram of a system in accordance with an embodiment of the invention; 
           [0023]      FIG. 2  is a composite drawing illustrating techniques of intracorporeal lithotripsy suitable for use with the system shown in  FIG. 1 , in accordance with alternate embodiments of the invention; 
           [0024]      FIG. 3  is a schematic diagram illustrating the distal end of the endoscope shown in  FIG. 1  in accordance with an embodiment of the invention; 
           [0025]      FIG. 4  is a diagram showing a calculus as viewed through an endoscope in accordance with an embodiment of the invention; 
           [0026]      FIG. 5  is a diagram showing a calculus as viewed through an endoscope in accordance with an embodiment of the invention; 
           [0027]      FIG. 6  is a schematic diagram of an optical image of a calculus in accordance with an embodiment of the invention; 
           [0028]      FIG. 7  is a schematic diagram of an optical image of the calculus shown in  FIG. 6  taken after a lithotriptic energy application, in accordance with an embodiment of the invention; 
           [0029]      FIG. 8  is a detailed pretreatment schematic diagram of a calculus in accordance with an embodiment of the invention; 
           [0030]      FIG. 9  is a detailed posttreatment schematic diagram of a calculus in accordance with an embodiment of the invention; and 
           [0031]      FIG. 10  is a flow chart of a method of intracorporeal lithotripsy, in accordance with an embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0032]    In the following description, numerous specific details are set forth in order to provide a thorough understanding of the various principles of the present invention. It will be apparent to one skilled in the art, however, that not all these details are necessarily always needed for practicing the present invention. In this instance, well-known circuits, control logic, and the details of computer program instructions for conventional algorithms and processes have not been shown in detail in order not to obscure the general concepts unnecessarily. 
         [0033]    Turning now to the drawings, Reference is initially made to  FIG. 1 , which is a pictorial schematic diagram of a system  10 , in accordance with an embodiment of the invention. A conventional endoscope  12  is adapted for intracorporeal lithotripsy. For example, the endoscope  12  can be a ureteroscope or a nephroscope for percutaneous entry to the renal pelvis. The endoscope  12  may be equipped for any form of intracorporeal lithotripsy known in the art, including laser lithotripsy, electrohydraulic lithotripsy, pneumatic lithotripsy, ultrasonic lithotripsy, and combinations thereof. Energy produced by a lithotripsy module  13  is projected through a working channel  15  of the endoscope  12 , which may include an optical probe comprising fiberoptics and an optical lens (not shown) for transmitting light from a source  14  to calculus  24 . The endoscope  12  may include a lens system and semi-conducting imaging array (described below) at distal end  16  for returning reflected light to an image acquisition unit  18 . The source  14  may emit light at one or more wavelengths. 
         [0034]    The image acquisition unit  18  can be realized as the device described in U.S. Pat. No. 8,659,646, which is herein incorporated by reference. 
         [0035]    Reference is now made to  FIG. 2 , which is a composite schematic drawing illustrating techniques of intracorporeal lithotripsy suitable for use with the system  10  ( FIG. 1 ), in accordance with embodiments of the invention. A nephroscope  20  as an endoscope for this procedure enters kidney  22  percutaneously to treat calculus  24  located in renal pelvis  44 . The nephroscope  20  has a hollow channel (not shown) through which an optical fiber  46  can be inserted and placed in proximity with the calculus  24 . Alternatively, a ureteroscope  48  can be passed in a retrograde direction through the urinary tract to approach the calculus  24 . The nephroscope  20  and ureteroscope  48  can incorporate the various intracorporeal lithotripsy technologies noted above. 
         [0036]    Reverting to  FIG. 1 , the image acquisition unit  18  provides image data to a processor  32 . The processor  32  typically comprises a general purpose or embedded computer processor, which is provided with a memory  19 , and programmed with suitable software for carrying out the functions described hereinbelow. Thus, although the processor  32  is shown as comprising a number of separate functional blocks, these blocks are not necessarily separate physical entities, but rather represent different computing tasks or data objects stored in a memory that is accessible to the processor. These tasks may be carried out in software running on a single processor, or on multiple processors. The software may be embodied on any of a variety of known non-transitory media for use with a computer system, such as a diskette, or hard drive, or CD-ROM. The code may be distributed on such media, or may be distributed to the processor  32  from the memory or storage of another computer system (not shown) over a network. Alternatively or additionally, the processor  32  may comprise a digital signal processor or hard-wired logic. 
         [0037]    The processor  32  is programmed to execute image processing routines  34 , and to determine characteristics of the calculus using analysis programs  36 , as described in further detail below. A database  38  of time-varying characteristics of the current calculus accumulated from actuations of the generator may be stored and a statistical model prepared, taking into consideration the parameters described herein. Using these characteristics, the processor  32  calculates optimum power parameters, and transmits control signals to a controller  40  of lithotripsy module  13 , which adjusts the power settings of a generator  42  responsively to one or more energy producing parameters. A monitor  50  may present an image  52  of the calculus being treated. 
         [0000]    
       
         
               
             
               
               
               
               
             
           
               
                 TABLE 1 
               
               
                   
               
               
                 Parameters 
               
               
                   
               
             
             
               
                   
               
             
          
           
               
                   
                   
                 Power 
                   
               
               
                   
                   
                 Pulse rate 
                   
               
               
                   
                   
                 Pulse width 
                   
               
               
                   
                   
                 Distance from tip 
                   
               
               
                   
                   
                 Retropulsion 
                   
               
               
                   
                   
                 Stone Size 
                   
               
               
                   
                   
                 Fragment Size 
                   
               
               
                   
                   
                 Stone Composition 
               
               
                   
                   
               
             
          
         
       
     
         [0038]    Table 1 is an exemplary table illustrating parameters that may affect power settings. 
         [0039]    The first three parameters in Table 1 are controllable by the operator or the processor  32 . In some embodiments, the processor  32  may robotically manipulate the endoscope  12  and affect the distance between the tip and the calculus. The last parameter, stone composition, may be known, estimated or entirely unknown, It is clearly not controllable, but may have a significant effect on fragment size. For example, a cysteine or uric acid stone can be expected to respond to a laser pulse differently from a calcium oxalate stone. 
         [0040]    The generator  42  produces the destructive energy to be applied to the calculus  24 , according to the above-noted types of intracorporeal lithotripsy being employed. Thus, the destructive energy may comprise a laser beam. In any case, the energy is transmitted by the lithotripsy module  13  and directed at a calculus that lies beyond the distal end  16 . A series of images of the calculus are acquired by the image acquisition unit  18 , which includes images taken before and after the energy application. 
         [0041]    Reference is now made to  FIG. 3 , which is a schematic diagram illustrating the distal end  16  of endoscope  12  ( FIG. 1 ), in accordance with an embodiment of the invention. The distal end  16  is assumed to be in proximity to calculus  24 . An illuminator  54  is able to radiate visible light, typically white light, under control of the image acquisition unit  18  ( FIG. 1 ). Returning light from an object illuminated by illuminator  54  is focused by a lens system  56  onto a semiconducting imaging array  58 , which is also controlled by the image acquisition unit  18 , and which enables capture of an image of the illuminated object. In the example of  FIG. 3 , a probe  57  traverses working channel  60  and is configured to be able to transmit a laser beam produced by the generator  42  in the lithotripsy module  13  through the optical fiber  46  ( FIG. 1 ) and along a path  62  extending from distal end  64 . The laser beam conveys sufficient energy to break or fracture calculus  24 . 
       Laser Operation. 
       [0042]    The typical laser&#39;s power parameters are the repetition rate (number of laser pulses per second), the energy per pulse and the pulse width. 
         [0043]    Reference is now made to  FIG. 4  and  FIG. 5 , which are diagrams showing calculus  24  in renal pelvis  44  as viewed as an image acquired by semiconductor imaging array  58  ( FIG. 3 ) at the distal end of an endoscope in accordance with an embodiment of the invention. The calculus  24  is seen before lithotriptic energy application, and during or after lithotriptic energy application in  FIG. 4  and  FIG. 5 , respectively, and its contour line  66  indicated. In  FIG. 5  the calculus  24  has been moved deeper into the renal pelvis  44 . Its original contour line  66  is shown as a broken line. A fragment  68  remains and has been displaced beyond the contour line  66 . During the firing of the laser on the stone, the system detects and tracks the stone in the image, and continuously measures the stone&#39;s motion, e.g., retrograde motion and fragmentation using the analysis programs  36  ( FIG. 1 ). In the example of  FIG. 5   i  an arrow indicates movement of the calculus  24 . Such movement may occur when the power applied to the calculus  24  is excessive. In a subsequent energy application, the power should be lowered to increase the likelihood that the calculus will fragment without retrograde motion. It is known that lower energy per pulse and longer pulse width result in less stone retropulsion. It is also known that lower energy per pulse and longer pulse width results in smaller fragments and vice versa. Size measurements of the stone and fragments can be based on the known size of the laser fiber, the spot of the aiming beam e.g., through the fiberoptics of the lithotripsy device or the safety guide wire e.g., projected through the working channel. 
         [0044]    During laser lithotripsy, the fiber tip is typically placed in contact with the stone&#39;s surface or in close proximity to the stone, typically within 1 mm. By calculating the relation between the size of the tip in the image with the size of the stone fragment in the image, based on the absolute size of the tip, the size of the fragment  68  can be calculated. 
         [0045]    Calculation of stone size may also be based on detection of the laser aiming beam. During laser lithotripsy an aiming beam, having a red or green color, is transmitted through the fiber along the path  62  together with an ablating laser beam, which is invisible to the human eye. The visible beam indicates the location of the target. The beam diameter seen on the surface of the stone is determined by the known size of the fiber used. The stone and fragment sizes may be calculated with reference to the beam diameter. Fiber diameters of 200, 270 or 365 μm are suitable. These values are not critical. 
         [0046]    Reference is now made to  FIG. 6 , which is a schematic diagram of an optical image of a calculus  70  typically presented to an operator on monitor  50  ( FIG. 1 ) in accordance with an embodiment of the invention. It will be seen from the discussion below that application of destructive energy by intracorporeal lithotripsy as described above causes the calculus  70  to disintegrate into fragments. 
         [0047]    Reference is now made to  FIG. 7 , which is a schematic diagram of an optical image of calculus  70  taken after an energy application, in accordance with an embodiment of the invention. Disruption of the calculus  70  into fragments is evident. The exterior surfaces of the fragments are delineated by contour lines  72 ,  74 ,  76 . Contour lines  72 ,  74 ,  76  were generated by the processor, and used to track the movements of the fragments. Tracking may be performed well-known methods of image analysis. One suitable technique is disclosed in U.S. Pat. No. 5,697,885, which is herein incorporated by reference. 
         [0048]    The image is only partially seen. Although prior to treatment, the calculus  70  was entirely visualized, now fragment  74  has been displaced and is not entirely within the field of view. While the fragments shown in  FIG. 7  are shown as relatively large with respect to the original mass of the calculus  70  in  FIG. 6  for clarity of presentation, this is not always the case. Indeed, the fragments are typically much smaller than presented in this example. 
         [0049]    Stone fragments movement also can be tracked using algorithms known in the art for the detection of a stone&#39;s contour line, e.g., contour line  66  ( FIG. 4 ) and detecting a change in location of the contours in successive frames. Reference is now made to  FIG. 8  and  FIG. 9 , which are detailed pretreatment and posttreatment schematic diagrams of a calculus  70  similar to  FIG. 6  and  FIG. 7 . These figures illustrate the use of color for motion tracking of the calculus  70 . Hatching patterns in different regions of the calculus  70  delineate regions of different fragments on images of the calculus. One method of motion tracking exploits differences in the stone&#39;s and/or fragments color from its surroundings. For example, region  78  in  FIG. 8  is no longer intact in the fragmented calculus of  FIG. 9 . Rather, portions of region  78  appear as smaller regions  80 ,  82 ,  84  in separate fragments. Detecting color contrast alone or in combination with edge detection algorithms provides sufficient information to determine a change in location of the stone in different frames. 
         [0050]    In one mode of operation, The system gradually increases the power parameters, the pulse width or both according to a predefined algorithm while continuously tracking actual performance. For example, one order of changing the power parameters is a 10% increase in energy followed by a 10% increase in pulse width in two successive firings. Additionally or alternatively, the operator may vary the distance between the endoscope and the calculus, recognizing that with laser techniques, efficiency drops off rapidly when a distance of about 1 mm is exceeded. Once the system detects a certain amount of retropulsion, it reacts by stabilizing or reducing the power parameters. 
         [0051]    Power parameters in successive frames may be set automatically, with or without confirmation by the operator, and optionally with reference to the model described above to verify that the stone is responding according to the model&#39;s predictions. 
       Non-Laser Intracorporeal Lithotripsy. 
       [0052]    The technique described above can be applied mutatis mutandis, to the other types of intracorporeal lithotripsy noted above, like a basket lithotripsy device or an ultrasonic probe. For example, while stone and fragment size cannot be determined using the laser&#39;s aiming beam, they can be estimated using the known size of the lithotripter probe or image processing by image recognition program. By the detection of stone fragments, the lithotripsy module can vary the destructive energy applied to the stone. Varying the distance from the endoscope to the calculus may be more influential in ballistic techniques than with lasers and can be controlled to some extent by the operator. 
       Operation. 
       [0053]    Reference is now made to  FIG. 10 , which is a flow-chart of a method of intracorporeal lithotripsy, in accordance with an embodiment of the invention. The procedure begins at initial step  86 . A subject is intubated with an endoscope, typically a ureteroscope or a nephroscope as described above and placed into contact with or proximity with a calculus. The endoscope is provided with optical imaging capabilities and an energy delivery system as noted above. Next, at step  88  an initial optical image of the calculus is acquired. 
         [0054]    Next, at step  90  the image is analyzed to establish its contour lines and/or color regions of the calculus. Power parameters of an intracorporeal lithotriptic device are set to initial values, which may vary according to the information obtained from the initial optical image. 
         [0055]    Next, at step  92  the lithotriptic device is activated. Destructive energy is transmitted through the endoscope and applied to the calculus. 
         [0056]    Next, at step  94 , after completion of step  92 , a second optical image of the calculus is acquired. 
         [0057]    Next, at step  96  the second optical image is analyzed to establish the size of the calculus remaining, the number of fragments, and the movement of the calculus and fragment from the position prior to performance of step  92 . 
         [0058]    Next, at decision step  98 , it is determined if the amount of movement of the calculus and its fragments is within a predetermined range, e.g., 1 mm. If the determination is negative, then control proceeds to step  100 . The power parameters of the lithotriptic device are adjusted. Control then returns to step  92  to iterate the activation of the lithotriptic device, using the new power parameters. 
         [0059]    If the determination at decision step  98  is affirmative, then control proceeds to decision step  102 , where it is determined if the lithotripsy procedure is complete. If the determination is negative, then control returns to step  92  to iterate the activation of the lithotriptic device. 
         [0060]    If the determination at decision step  98  is affirmative, then control proceeds to final step  104  and the procedure ends. 
         [0061]    It will be appreciated by persons skilled in the art that the present invention is not limited to what has been particularly shown and described hereinabove. Rather, the scope of the present invention includes both combinations and sub-combinations of the various features described hereinabove, as well as variations and modifications thereof that are not in the prior art, which would occur to persons skilled in the art upon reading the foregoing description.