Abstract:
A system for vessel embolization, comprising a mapping element measuring dimensions of a target vessel and a computing element computing a volume of a selected portion of the target vessel based on the dimensions of the blood vessel in combination with an embolization material delivery element including a distal end which, when in an operative position, opens into the target vessel to deposit the embolization material into the selected portion of the target vessel.

Description:
BRIEF DESCRIPTION OF THE DRAWINGS  
       [0001]      FIG. 1  is a pictorial representation of a fluoroscopic localization of a blood vessels supplying a tumor;  
         [0002]      FIG. 2  is a schematic representation of a probe mapping a blood vessel, according to the invention;  
         [0003]      FIG. 3  is a diagram showing a mapped inner and outer wall of a blood vessel, according to the invention;  
         [0004]      FIG. 4  is a diagram representing a blood vessel volume calculation according to the invention;  
         [0005]      FIG. 5  is a table showing exemplary types of embolization elements used for embolization of a blood vessel according to the invention;  
         [0006]      FIG. 6  is a schematic diagram showing delivery of embolization elements to a target blood vessel according to the invention;  
         [0007]      FIG. 7  is a pictorial representation of a fluoroscopic evaluation of the embolization of a blood vessel; and  
         [0008]      FIG. 8  is a diagram showing a flow sensing micro catheter according to the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0009]     The present invention may be further understood with reference to the following description and the appended drawings, wherein like elements are referred to with the same reference numerals. The invention relates to methods and systems for treating tissue masses by reducing the flow of blood thereto. More specifically, the invention relates to a method and system for determining the volume of an embolization material for occluding a blood vessel supplying a target tissue mass such as a tumor.  
         [0010]     Embodiments of the present invention determine the volume of a blood vessel or vessels supplying a target tissue mass to allow calculation of an optimum volume of embolization elements to be supplied thereto. The calculated amount of embolization elements is inserted into the vessel to occlude the vessel to necrose the target tissue while minimizing the impact on the surrounding non-targeted tissues. Additional steps according to the invention may be carried out to evaluate the effectiveness of the procedure by, for example, measuring the flow of blood through the occluded vessel after application of the embolization elements. Thus, the calculated amount of embolization elements and/or feedback from the measure of blood flow after the application may be used in selecting a size of embolization elements to be used and in determining when the embolization is completed.  
         [0011]     As shown in  FIG. 1 , the blood vessel or vessels that supply the target tissue mass are first identified. For example, a fluoroscopy screen  100  displays the target tissue mass (e.g., tumor  104 ) and the blood vessels  102  connected thereto. The physician may also use the image on the fluoroscopy screen  100  to determine an appropriate location for the deployment of embolization elements. In addition to fluoroscopy, other conventional methods of identifying and visualizing the target blood vessel supplying the tumor  104 , such as a CT and contrast agent or MRI and contrast agent, may be used.  
         [0012]     After identifying the target blood vessel(s), a visualization and mapping process according to the invention is carried out. The dimensions of the target blood vessel are determined by, for example, locating inner and outer walls at multiple locations along the length of each target vessel. Based on this data, volumes of target portions of each target vessel are calculated.  FIGS. 2 and 4  show an exemplary embodiment of the procedure for mapping a target vessel  102 . In this procedure, a probe  210  having a mapping head  212  is inserted into the target blood vessel  102  and translated along the length of a selected portion thereof. For example, the probe  210  may be a MediGuide visualization device, manufactured by MediGuide.  
         [0013]     The visualization probe  210  is inserted into the lumen  200  of the target blood vessel  102  and advanced along the length of a selected portion of the lumen  200  in the vicinity of the tumor  104 . As would be understood by those skilled in the art, the mapping head  212  is preferably adapted to identify the inner wall  202  and the outer wall  204  of the target blood vessel  102  to determine dimensions of the lumen  200 . The apparatus according to the invention also tracks the location of the mapping head  212  within the blood vessel  102 , so that a profile of the vessel along the longitudinal axis of the lumen  200  can be generated. As would be understood by those skilled in the art, the mapping head  212  may use any of a variety of known mechanisms to visualize and/or map the lumen  200 . For example, ultrasound, CT, MRI, light or electrical energy may be used to measure dimensions of the target blood vessel  102 , as well as other visual methods.  
         [0014]     Embodiments of the invention utilize the dimensional data provided by the mapping head  212  of the probe  210  to compute an inner volume of the blood vessel  102 . As would be understood by those skilled in the art, this volume from the measured data may be carried out using an electronic computer, a mechanical computer, numerical tables or graphs, or may be left for the physician to carry out as desired. In one exemplary embodiment shown in  FIG. 4 , the lumen  200  of the target blood vessel  102  is subdivided into a plurality of discrete sections  250  at each of which the probe  210  determines dimensions of the lumen by localizing the inner and outer walls of the vessel. The discrete sections  250  are located, for example, between a first point  252  distal of the tumor  104  and a second point  254  adjacent to the tumor  104 , defining start/stop points for the volume computation.  
         [0015]     According to the embodiments of the invention, the shape, size and volume of the vessel that is to be embolized is calculated based on the data provided by the probe  210  which may be, for example, a probe using MediGuide technology. Alternatively, a computing module may be provided that generates a value or other indication of the vessel&#39;s volume, using input generated by the probe  210 . The computing module may display a 3-D image of the vessel, which would output the vessel volume in mL or CC. The computing module may directly provide to the physician the volume of the vessel, as well as an optimized amount and type of embolization elements for the procedure, based on input including dimensions of the vessel and a size and/or shape of the implants to be used, etc. Those skilled in the art will understand that a volume of the embolization elements to be introduced into the vessel will be different from a volume of a single embolization element multiplied by the number of elements to be provided as a packing efficiency of the elements will vary based on the size and shape of the elements. Thus, the volume calculated will preferably reflect a volume of a plurality of embolization elements packed as they will be in a target vessel.  
         [0016]      FIG. 5  shows a plurality of sample embolization elements which may, for example, be PVA spheres of different sizes which may be selected depending on the size of the target blood vessel(s). According to the invention, the correct size and number of embolization elements is determined based on the volume of the portion of the target blood vessel  102  as determined by the probe  210 . For example, the exemplary embolization system according to the invention may comprise a table listing the dimensions of various embolization elements along with the volumes occupied by various numbers of the embolization elements.  
         [0017]     Alternatively, the table of  FIG. 5  may be included in an electronic module that provides the user with the appropriate size and an optimum number of embolization elements for occluding the target vessel  102 , as derived from the data of the probe  210 . In one exemplary embodiment, the embolization elements may range from small ellipsoids or spheres  300  having a diameter of about 100-300 μm, to large ellipsoids or spheres  302  having a diameter of about 900-1200 μm. These sizes of embolization elements are effective in occluding blood vessels having a lumen size of between about 1.5 Fr to about 4-5 Fr. Those skilled in the art will understand that, if a vessel smaller or larger than this range is to be occluded, embolization elements of larger or smaller size may be employed without using the same method to calculate the number/volume of these elements to be used.  
         [0018]     According to embodiments of the present invention, the appropriate number of embolization elements is injected into the target blood vessel to block the flow of blood therethrough. As shown in  FIG. 6 , an embolization delivery device  310  is advanced to the blood vessel or vessels  102  that feed blood to the tumor  104 , so that the embolization elements  312  can be delivered thereto. For example, the embolization delivery device  310  may be a catheter or other similar device advanced along the vessel  102  until a target area is reached. When the delivery device  310  is in the target area, elements  312  or other embolization elements are introduced into the target vessel  102  by, for example, injecting the elements  312  into the delivery device  310  using a syringe or other injection mechanism. Once delivered, the elements  312  form an occlusion  320  in the blood vessel  102  preventing blood from reaching the ends  314 ,  316  of the vessel to necrose the tumor  104 .  
         [0019]     An evaluation step and system may be employed according to the invention to determine the effectiveness of the occlusion after the embolization elements have been delivered to the target blood vessel. For example, as shown in  FIG. 7 , a fluoroscopy display  400  may be aimed at the tumor  104  and target blood vessel  102  to determine the effectiveness of the occlusion  402 . The shape and dimensions of the blood vessel  102 , and in particular of the occluded region  402  may be evaluated to determine whether a sufficient number of embolization elements has been delivered to the target blood vessel  102 . The tumor  104  may also be evaluated by fluoroscopy to determine whether a reduction in size occurs as a result of the treatment.  
         [0020]     The effectiveness of the procedure according to the invention may also be evaluated with other diagnostic tools. For example, a flow sensing micro-catheter may be used to measure the flow of blood that passes across the occlusion, to determine the effectiveness of the embolization procedure. As shown in  FIG. 8 , the micro catheter  414  comprises a flow sensing element  410  that measures the flow rate of blood passing within the lumen  416  in the direction of the arrows  412 . The flow sensing element  410  may comprise pressure sensors, electrostatic sensors, or other elements that can measure the flow of blood in the lumen  416 . Signals generated by the flow sensing element  410  prior to the treatment of the target tissue mass are used to determine an initial state of the selected physiological condition. Signals generated after an embolic agent is dispensed to treat the tissue mass are used to determine the current state of the physiological condition. The initial and current states are compared to determine whether a desired change has been achieved. The flow sensing micro-catheter is referenced in application Ser. No. 10/739,584 filed Dec. 17, 2003.  
         [0021]     The exemplary embodiments of the present invention provide an objective and efficient method of evaluating the type and amount of embolization material necessary to occlude a blood vessel supplying blood to a tumor. For example, the number and size of embolization elements used to occlude a blood vessel is derived from measurements of the internal dimensions of the blood vessel. The procedures and systems according to the present invention thus dispense with the trial and error approaches in which the physician guesses at the amount of material necessary for the embolization and after some time tests the results to determine if the amount was correct.  
         [0022]     The present invention has been described with reference to specific embodiments, and more specifically to an embolization system using embolization elements such as PVA spheres. However, other embodiments may be devised that are applicable to other embolization materials, without departing from the scope of the invention. Accordingly, various modifications and changes may be made to the embodiments, without departing from the broadest spirit and scope of the present invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative rather than restrictive sense.