Patent Publication Number: US-2011060298-A1

Title: Tissue imaging and extraction systems

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 11/560,742, filed Nov. 16, 2006, which claims the benefit of priority of U.S. Provisional patent application No. 60/737,521 filed Nov. 16, 2005. U.S. patent application Ser. No. 11/560,742 is a continuation-in-part of U.S. patent application Ser. No. 11/259,498 filed Oct. 25, 2005, which claims priority of U.S. Provisional patent application No. 60/649,246 filed Feb. 2, 2005, each of which is incorporated herein by reference in its entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates generally to medical devices used for visualizing and/or closing openings or defects within a body. More particularly, the present invention relates to apparatus and methods for visualizing and/or performing procedures within a patient&#39;s body such as within the heart, which are generally difficult to image because of surrounding opaque bodily fluids such as blood. 
     BACKGROUND OF THE INVENTION 
     Conventional devices for visualizing interior regions of a body lumen are known. For example, ultrasound devices have been used to produce images from within a body in vivo. Ultrasound has been used both with and without contrast agents, which typically enhance ultrasound-derived images. 
     Other conventional methods have utilized catheters or probes having position sensors deployed within the body lumen, such as the interior of a cardiac chamber. These types of positional sensors are typically used to determine the movement of a cardiac tissue surface or the electrical activity within the cardiac tissue. When a sufficient number of points have been sampled by the sensors, a “map” of the cardiac tissue may be generated. 
     Another conventional device utilizes an inflatable balloon which is typically introduced intravascularly in a deflated state and then inflated against the tissue region to be examined. Imaging is typically accomplished by an optical fiber or other apparatus such as electronic chips for viewing the tissue through the membrane(s) of the inflated balloon. Moreover, the balloon must generally be inflated for imaging. Other conventional balloons utilize a cavity or depression formed at a distal end of the inflated balloon. This cavity or depression is pressed against the tissue to be examined and is flushed with a clear fluid to provide a clear pathway through the blood. 
     However, such imaging balloons have many inherent disadvantages. For instance, such balloons generally require that the balloon be inflated to a relatively large size which may undesirably displace surrounding tissue and interfere with fine positioning of the imaging system against the tissue. Moreover, the working area created by such inflatable balloons are generally cramped and limited in size. Furthermore, inflated balloons may be susceptible to pressure changes in the surrounding fluid. For example, if the environment surrounding the inflated balloon undergoes pressure changes, e.g., during systolic and diastolic pressure cycles in a beating heart, the constant pressure change may affect the inflated balloon volume and its positioning to produce unsteady or undesirable conditions for optimal tissue imaging. 
     Accordingly, these types of imaging modalities are generally unable to provide desirable images useful for sufficient diagnosis and therapy of the endoluminal structure, due in part to factors such as dynamic forces generated by the natural movement of the heart. Moreover, anatomic structures within the body can occlude or obstruct the image acquisition process. Also, the presence and movement of opaque bodily fluids such as blood generally make in vivo imaging of tissue regions within the heart difficult. 
     Other external imaging modalities are also conventionally utilized. For example, computed tomography (CT) and magnetic resonance imaging (MRI) are typical modalities which are widely used to obtain images of body lumens such as the interior chambers of the heart. However, such imaging modalities fail to provide real-time imaging for intra-operative therapeutic procedures. Fluoroscopic imaging, for instance, is widely used to identify anatomic landmarks within the heart and other regions of the body. However, fluoroscopy fails to provide an accurate image of the tissue quality or surface and also fails to provide for instrumentation for performing tissue manipulation or other therapeutic procedures upon the visualized tissue regions. In addition, fluoroscopy provides a shadow of the intervening tissue onto a plate or sensor when it may be desirable to view the intraluminal surface of the tissue to diagnose pathologies or to perform some form of therapy on it. 
     Thus, a tissue imaging system which is able to provide real-time in vivo images of tissue regions within body lumens such as the heart through opaque media such as blood and which also provide instruments for therapeutic procedures upon the visualized tissue are desirable. 
     BRIEF SUMMARY OF THE INVENTION 
     A tissue imaging and manipulation apparatus that may be utilized for procedures within a body lumen, such as the heart, in which visualization of the surrounding tissue is made difficult, if not impossible, by medium contained within the lumen such as blood, is described below. Generally, such a tissue imaging and manipulation apparatus comprises an optional delivery catheter or sheath through which a deployment catheter and imaging hood may be advanced for placement against or adjacent to the tissue to be imaged. 
     The deployment catheter may define a fluid delivery lumen therethrough as well as an imaging lumen within which an optical imaging fiber or assembly may be disposed for imaging tissue. When deployed, the imaging hood may be expanded into any number of shapes, e.g., cylindrical, conical as shown, semi-spherical, etc., provided that an open area or field is defined by the imaging hood. The open area is the area within which the tissue region of interest may be imaged. The imaging hood may also define an atraumatic contact lip or edge for placement or abutment against the tissue region of interest. Moreover, the distal end of the deployment catheter or separate manipulatable catheters may be articulated through various controlling mechanisms such as push-pull wires manually or via computer control 
     The deployment catheter may also be stabilized relative to the tissue surface through various methods. For instance, inflatable stabilizing balloons positioned along a length of the catheter may be utilized, or tissue engagement anchors may be passed through or along the deployment catheter for temporary engagement of the underlying tissue. 
     In operation, after the imaging hood has been deployed, fluid may be pumped at a positive pressure through the fluid delivery lumen until the fluid fills the open area completely and displaces any blood from within the open area. The fluid may comprise any biocompatible fluid, e.g., saline, water, plasma, Fluorinert™, etc., which is sufficiently transparent to allow for relatively undistorted visualization through the fluid. The fluid may be pumped continuously or intermittently to allow for image capture by an optional processor which may be in communication with the assembly. Moreover, the fluid flow rate may be controlled or metered via any number of actuators which may control the flow rate in a linear or non-linear manner. 
     The imaging hood may be formed into any number of configurations and the imaging assembly may also be utilized with any number of therapeutic tools which may be deployed through the deployment catheter. 
     Moreover, the imaging assembly maybe utilized for additional procedures, such as clearing blood clots, emboli, and other debris which may be present in a body lumen. Additionally, other variations of the assembly may also be used for facilitating trans-septal access across tissue regions as well as for facilitate the maintenance of a patient body fluids during a procedure. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  shows a side view of one variation of a tissue imaging apparatus during deployment from a sheath or delivery catheter. 
         FIG. 1B  shows the deployed tissue imaging apparatus of  FIG. 1A  having an optionally expandable hood or sheath attached to an imaging and/or diagnostic catheter. 
         FIG. 1C  shows an end view of a deployed imaging apparatus. 
         FIGS. 1D to 1F  show the apparatus of  FIGS. 1A to 1C  with an additional lumen, e.g., for passage of a guidewire therethrough. 
         FIGS. 2A and 2B  show one example of a deployed tissue imager positioned against or adjacent to the tissue to be imaged and a flow of fluid, such as saline, displacing blood from within the expandable hood. 
         FIG. 3A  shows an articulatable imaging assembly which may be manipulated via push-pull wires or by computer control. 
         FIGS. 3B and 3C  show steerable instruments, respectively, where an articulatable delivery catheter may be steered within the imaging hood or a distal portion of the deployment catheter itself may be steered. 
         FIGS. 4A to 4C  show side and cross-sectional end views, respectively, of another variation having an off-axis imaging capability. 
         FIG. 5  shows an illustrative view of an example of a tissue imager advanced intravascularly within a heart for imaging tissue regions within an atrial chamber. 
         FIGS. 6A to 6C  illustrate deployment catheters having one or more optional inflatable balloons or anchors for stabilizing the device during a procedure. 
         FIGS. 7A and 7B  illustrate a variation of an anchoring mechanism such as a helical tissue piercing device for temporarily stabilizing the imaging hood relative to a tissue surface. 
         FIG. 7C  shows another variation for anchoring the imaging hood having one or more tubular support members integrated with the imaging hood; each support members may define a lumen therethrough for advancing a helical tissue anchor within. 
         FIG. 8A  shows an illustrative example of one variation of how a tissue imager may be utilized with an imaging device. 
         FIG. 8B  shows a further illustration of a hand-held variation of the fluid delivery and tissue manipulation system. 
         FIGS. 9A to 9C  illustrate an example of capturing several images of the tissue at multiple regions. 
         FIGS. 10A and 10B  show charts illustrating how fluid pressure within the imaging hood may be coordinated with the surrounding blood pressure; the fluid pressure in the imaging hood may be coordinated with the blood pressure or it may be regulated based upon pressure feedback from the blood. 
         FIG. 11A  shows an actuator which may be configured as a foot pedal or foot switch to control fluid infusion rates into the imaging hood. 
         FIG. 11B  illustrates an exemplary graph of various flow rate profiles which may be utilized when infusing the fluid into the imaging hood. 
         FIGS. 12A to 12C  illustrates a variation of the assembly which may be utilized to capture debris which may be errant in surrounding blood. 
         FIG. 13  shows another variation of the assembly positioned within a heart chamber and which may be utilized for biopsy sampling or for debris extraction or removal from a body lumen. 
         FIG. 14  shows a perspective view of another variation of the assembly configured for rapid-exchange of a guidewire. 
         FIGS. 15A to 15D  illustrates a partial cross-sectional view of an assembly utilizing an outer sheath for crossing a region of tissue. 
         FIG. 16  shows another variation of the assembly configured to withdraw diluted blood and to filter the blood for re-infusion back into the patient body. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     A tissue-imaging and manipulation apparatus described below is able to provide real-time images in vivo of tissue regions within a body lumen such as a heart, which is filled with blood flowing dynamically therethrough and is also able to provide intravascular tools and instruments for performing various procedures upon the imaged tissue regions. Such an apparatus may be utilized for many procedures, e.g., facilitating trans-septal access to the left atrium, cannulating the coronary sinus, diagnosis of valve regurgitation/stenosis, valvuloplasty, atrial appendage closure, arrhythmogenic focus ablation, among other procedures. 
     One variation of a tissue access and imaging apparatus is shown in the detail perspective views of  FIGS. 1A to 1C . As shown in  FIG. 1A , tissue imaging and manipulation assembly  10  may be delivered intravascularly through the patient&#39;s body in a low-profile configuration via a delivery catheter or sheath  14 . In the case of treating tissue, such as the mitral valve located at the outflow tract of the left atrium of the heart, it is generally desirable to enter or access the left atrium while minimizing trauma to the patient. To non-operatively effect such access, one conventional approach involves puncturing the intra-atrial septum from the right atrial chamber to the left atrial chamber in a procedure commonly called a trans-septal procedure or septostomy. For procedures such as percutaneous valve repair and replacement, trans-septal access to the left atrial chamber of the heart may allow for larger devices to be introduced into the venous system than can generally be introduced percutaneously into the arterial system. 
     When the imaging and manipulation assembly  10  is ready to be utilized for imaging tissue, imaging hood  12  may be advanced relative to catheter  14  and deployed from a distal opening of catheter  14 , as shown by the arrow. Upon deployment, imaging hood  12  may be unconstrained to expand or open into a deployed imaging configuration, as shown in  FIG. 1B . Imaging hood  12  may be fabricated from a variety of pliable or conformable biocompatible material including but not limited to, e.g., polymeric, plastic, or woven materials. One example of a woven material is Kevlar® (E. I. du Pont de Nemours, Wilmington, Del.), which is an aramid and which can be made into thin, e.g., less than 0.001 in., materials which maintain enough integrity for such applications described herein. Moreover, the imaging hood  12  may be fabricated from a translucent or opaque material and in a variety of different colors to optimize or attenuate any reflected lighting from surrounding fluids or structures, i.e., anatomical or mechanical structures or instruments. In either case, imaging hood  12  may be fabricated into a uniform structure or a scaffold-supported structure, in which case a scaffold made of a shape memory alloy, such as Nitinol, or a spring steel, or plastic, etc., may be fabricated and covered with the polymeric, plastic, or woven material. 
     Imaging hood  12  may be attached at interface  24  to a deployment catheter  16  which may be translated independently of deployment catheter or sheath  14 . Attachment of interface  24  may be accomplished through any number of conventional methods. Deployment catheter  16  may define a fluid delivery lumen  18  as well as an imaging lumen  20  within which an optical imaging fiber or assembly may be disposed for imaging tissue. When deployed, imaging hood  12  may expand into any number of shapes, e.g., cylindrical, conical as shown, semi-spherical, etc., provided that an open area or field  26  is defined by imaging hood  12 . The open area  26  is the area within which the tissue region of interest may be imaged. Imaging hood  12  may also define an atraumatic contact lip or edge  22  for placement or abutment against the tissue region of interest. Moreover, the diameter of imaging hood  12  at its maximum fully deployed diameter, e.g., at contact lip or edge  22 , is typically greater relative to a diameter of the deployment catheter  16  (although a diameter of contact lip or edge  22  may be made to have a smaller or equal diameter of deployment catheter  16 ). For instance, the contact edge diameter may range anywhere from 1 to 5 times (or even greater, as practicable) a diameter of deployment catheter  16 .  FIG. 1C  shows an end view of the imaging hood  12  in its deployed configuration. Also shown are the contact lip or edge  22  and fluid delivery lumen  18  and imaging lumen  20 . 
     The imaging and manipulation assembly  10  may additionally define a guidewire lumen therethrough, e.g., a concentric or eccentric lumen, as shown in the side and end views, respectively, of  FIGS. 1D to 1F . The deployment catheter  16  may define guidewire lumen  19  for facilitating the passage of the system over or along a guidewire  17 , which may be advanced intravascularly within a body lumen. The deployment catheter  16  may then be advanced over the guidewire  17 , as generally known in the art. 
     In operation, after imaging hood  12  has been deployed, as in  FIG. 1B , and desirably positioned against the tissue region to be imaged along contact edge  22 , the displacing fluid may be pumped at positive pressure through fluid delivery lumen  18  until the fluid fills open area  26  completely and displaces any fluid  28  from within open area  26 . The displacing fluid flow may be laminarized to improve its clearing effect and to help prevent blood from re-entering the imaging hood  12 . Alternatively, fluid flow may be started before the deployment takes place. The displacing fluid, also described herein as imaging fluid, may comprise any biocompatible fluid, e.g., saline, water, plasma, etc., which is sufficiently transparent to allow for relatively undistorted visualization through the fluid. Alternatively or additionally, any number of therapeutic drugs may be suspended within the fluid or may comprise the fluid itself which is pumped into open area  26  and which is subsequently passed into and through the heart and the patient body. 
     As seen in the example of  FIGS. 2A and 2B , deployment catheter  16  may be manipulated to position deployed imaging hood  12  against or near the underlying tissue region of interest to be imaged, in this example a portion of annulus A of mitral valve MV within the left atrial chamber. As the surrounding blood  30  flows around imaging hood  12  and within open area  26  defined within imaging hood  12 , as seen in  FIG. 2A , the underlying annulus A is obstructed by the opaque blood  30  and is difficult to view through the imaging lumen  20 . The translucent fluid  28 , such as saline, may then be pumped through fluid delivery lumen  18 , intermittently or continuously, until the blood  30  is at least partially, and preferably completely, displaced from within open area  26  by fluid  28 , as shown in  FIG. 2B . 
     Although contact edge  22  need not directly contact the underlying tissue, it is at least preferably brought into close proximity to the tissue such that the flow of clear fluid  28  from open area  26  may be maintained to inhibit significant backflow of blood  30  back into open area  26 . Contact edge  22  may also be made of a soft elastomeric material such as certain soft grades of silicone or polyurethane, as typically known, to help contact edge  22  conform to an uneven or rough underlying anatomical tissue surface. Once the blood  30  has been displaced from imaging hood  12 , an image may then be viewed of the underlying tissue through the clear fluid  30 . This image may then be recorded or available for real-time viewing for performing a therapeutic procedure. The positive flow of fluid  28  may be maintained continuously to provide for clear viewing of the underlying tissue. Alternatively, the fluid  28  may be pumped temporarily or sporadically only until a clear view of the tissue is available to be imaged and recorded, at which point the fluid flow  28  may cease and blood  30  may be allowed to seep or flow back into imaging hood  12 . This process may be repeated a number of times at the same tissue region or at multiple tissue regions. 
     In desirably positioning the assembly at various regions within the patient body, a number of articulation and manipulation controls may be utilized. For example, as shown in the articulatable imaging assembly  40  in  FIG. 3A , one or more push-pull wires  42  may be routed through deployment catheter  16  for steering the distal end portion of the device in various directions  46  to desirably position the imaging hood  12  adjacent to a region of tissue to be visualized. Depending upon the positioning and the number of push-pull wires  42  utilized, deployment catheter  16  and imaging hood  12  may be articulated into any number of configurations  44 . The push-pull wire or wires  42  may be articulated via their proximal ends from outside the patient body manually utilizing one or more controls. Alternatively, deployment catheter  16  may be articulated by computer control, as further described below. 
     Additionally or alternatively, an articulatable delivery catheter  48 , which may be articulated via one or more push-pull wires and having an imaging lumen and one or more working lumens, may be delivered through the deployment catheter  16  and into imaging hood  12 . With a distal portion of articulatable delivery catheter  48  within imaging hood  12 , the clear displacing fluid may be pumped through delivery catheter  48  or deployment catheter  16  to clear the field within imaging hood  12 . As shown in  FIG. 3B , the articulatable delivery catheter  48  may be articulated within the imaging hood to obtain a better image of tissue adjacent to the imaging hood  12 . Moreover, articulatable delivery catheter  48  may be articulated to direct an instrument or tool passed through the catheter  48 , as described in detail below, to specific areas of tissue imaged through imaging hood  12  without having to reposition deployment catheter  16  and re-clear the imaging field within hood  12 . 
     Alternatively, rather than passing an articulatable delivery catheter  48  through the deployment catheter  16 , a distal portion of the deployment catheter  16  itself may comprise a distal end  49  which is articulatable within imaging hood  12 , as shown in  FIG. 3C . Directed imaging, instrument delivery, etc., may be accomplished directly through one or more lumens within deployment catheter  16  to specific regions of the underlying tissue imaged within imaging hood  12 . 
     Visualization within the imaging hood  12  may be accomplished through an imaging lumen  20  defined through deployment catheter  16 , as described above. In such a configuration, visualization is available in a straight-line manner, i.e., images are generated from the field distally along a longitudinal axis defined by the deployment catheter  16 . Alternatively or additionally, an articulatable imaging assembly having a pivotable support member  50  may be connected to, mounted to, or otherwise passed through deployment catheter  16  to provide for visualization off-axis relative to the longitudinal axis defined by deployment catheter  16 , as shown in  FIG. 4A . Support member  50  may have an imaging element  52 , e.g., a CCD or CMOS imager or optical fiber, attached at its distal end with its proximal end connected to deployment catheter  16  via a pivoting connection  54 . 
     If one or more optical fibers are utilized for imaging, the optical fibers  58  may be passed through deployment catheter  16 , as shown in the cross-section of  FIG. 4B , and routed through the support member  50 . The use of optical fibers  58  may provide for increased diameter sizes of the one or several lumens  56  through deployment catheter  16  for the passage of diagnostic and/or therapeutic tools therethrough. Alternatively, electronic chips, such as a charge coupled device (CCD) or a CMOS imager, which are typically known, may be utilized in place of the optical fibers  58 , in which case the electronic imager may be positioned in the distal portion of the deployment catheter  16  with electric wires being routed proximally through the deployment catheter  16 . Alternatively, the electronic imagers may be wirelessly coupled to a receiver for the wireless transmission of images. Additional optical fibers or light emitting diodes (LEDs) can be used to provide lighting for the image or operative theater, as described below in further detail. Support member  50  may be pivoted via connection  54  such that the member  50  can be positioned in a low-profile configuration within channel or groove  60  defined in a distal portion of catheter  16 , as shown in the cross-section of  FIG. 4C . During intravascular delivery of deployment catheter  16  through the patient body, support member  50  can be positioned within channel or groove  60  with imaging hood  12  also in its low-profile configuration. During visualization, imaging hood  12  may be expanded into its deployed configuration and support member  50  may be deployed into its off-axis configuration for imaging the tissue adjacent to hood  12 , as in  FIG. 4A . Other configurations for support member  50  for off-axis visualization may be utilized, as desired. 
       FIG. 5  shows an illustrative cross-sectional view of a heart H having tissue regions of interest being viewed via an imaging assembly  10 . In this example, delivery catheter assembly  70  may be introduced percutaneously into the patient&#39;s vasculature and advanced through the superior vena cava SVC and into the right atrium RA. The delivery catheter or sheath  72  may be articulated through the atrial septum AS and into the left atrium LA for viewing or treating the tissue, e.g., the annulus A, surrounding the mitral valve MV. As shown, deployment catheter  16  and imaging hood  12  may be advanced out of delivery catheter  72  and brought into contact or in proximity to the tissue region of interest. In other examples, delivery catheter assembly  70  may be advanced through the inferior vena cava IVC, if so desired. Moreover, other regions of the heart H, e.g., the right ventricle RV or left ventricle LV, may also be accessed and imaged or treated by imaging assembly  10 . 
     In accessing regions of the heart H or other parts of the body, the delivery catheter or sheath  14  may comprise a conventional intra-vascular catheter or an endoluminal delivery device. Alternatively, robotically-controlled delivery catheters may also be optionally utilized with the imaging assembly described herein, in which case a computer-controller  74  may be used to control the articulation and positioning of the delivery catheter  14 . An example of a robotically-controlled delivery catheter which may be utilized is described in further detail in US Pat. Pub. 2002/0087169 A1 to Brock et al. entitled “Flexible Instrument”, which is incorporated herein by reference in its entirety. Other robotically-controlled delivery catheters manufactured by Hansen Medical, Inc. (Mountain View, Calif.) may also be utilized with the delivery catheter . 14 . 
     To facilitate stabilization of the deployment catheter  16  during a procedure, one or more inflatable balloons or anchors  76  may be positioned along the length of catheter  16 , as shown in  FIG. 6A . For example, when utilizing a trans-septal approach across the atrial septum AS into the left atrium LA, the inflatable balloons  76  may be inflated from a low-profile into their expanded configuration to temporarily anchor or stabilize the catheter  16  position relative to the heart H.  FIG. 6B  shows a first balloon  78  inflated while  FIG. 6C  also shows a second balloon  80  inflated proximal to the first balloon  78 . In such a configuration, the septal wall AS may be wedged or sandwiched between the balloons  78 ,  80  to temporarily stabilize the catheter  16  and imaging hood  12 . A single balloon  78  or both balloons  78 ,  80  may be used. Other alternatives may utilize expandable mesh members, malecots, or any other temporary expandable structure. After a procedure has been accomplished, the balloon assembly  76  may be deflated or re-configured into a low-profile for removal of the deployment catheter  16 . 
     To further stabilize a position of the imaging hood  12  relative to a tissue surface to be imaged, various anchoring mechanisms may be optionally employed for temporarily holding the imaging hood  12  against the tissue. Such anchoring mechanisms may be particularly useful for imaging tissue which is subject to movement, e.g., when imaging tissue within the chambers of a beating heart. A tool delivery catheter  82  having at least one instrument lumen and an optional visualization lumen may be delivered through deployment catheter  16  and into an expanded imaging hood  12 . As the imaging hood  12  is brought into contact against a tissue surface T to be examined, an anchoring mechanisms such as a helical tissue piercing device  84  may be passed through the tool delivery catheter  82 , as shown in  FIG. 7A , and into imaging hood  12 . 
     The helical tissue engaging device  84  may be torqued from its proximal end outside the patient body to temporarily anchor itself into the underlying tissue surface T. Once embedded within the tissue T, the helical tissue engaging device  84  may be pulled proximally relative to deployment catheter  16  while the deployment catheter  16  and imaging hood  12  are pushed distally, as indicated by the arrows in  FIG. 7B , to gently force the contact edge or lip  22  of imaging hood against the tissue T. The positioning of the tissue engaging device  84  may be locked temporarily relative to the deployment catheter  16  to ensure secure positioning of the imaging hood  12  during a diagnostic or therapeutic procedure within the imaging hood  12 . After a procedure, tissue engaging device  84  may be disengaged from the tissue by torquing its proximal end in the opposite direction to remove the anchor form the tissue T and the deployment catheter  16  may be repositioned to another region of tissue where the anchoring process may be repeated or removed from the patient body. The tissue engaging device  84  may also be constructed from other known tissue engaging devices such as vacuum-assisted engagement or grasper-assisted engagement tools, among others. 
     Although a helical anchor  84  is shown, this is intended to be illustrative and other types of temporary anchors may be utilized, e.g., hooked or barbed anchors, graspers, etc. Moreover, the tool delivery catheter  82  may be omitted entirely and the anchoring device may be delivered directly through a lumen defined through the deployment catheter  16 . 
     In another variation where the tool delivery catheter  82  may be omitted entirely to temporarily anchor imaging hood  12 ,  FIG. 7C  shows an imaging hood  12  having one or more tubular support members  86 , e.g., four support members  86  as shown, integrated with the imaging hood  12 . The tubular support members  86  may define lumens therethrough each having helical tissue engaging devices  88  positioned within. When an expanded imaging hood  12  is to be temporarily anchored to the tissue, the helical tissue engaging devices  88  may be urged distally to extend from imaging hood  12  and each may be torqued from its proximal end to engage the underlying tissue T. Each of the helical tissue engaging devices  88  may be advanced through the length of deployment catheter  16  or they may be positioned within tubular support members  86  during the delivery and deployment of imaging hood  12 . Once the procedure within imaging hood  12  is finished, each of the tissue engaging devices  88  may be disengaged from the tissue and the imaging hood  12  may be repositioned to another region of tissue or removed from the patient body. 
     An illustrative example is shown in  FIG. 8A  of a tissue imaging assembly connected to a fluid delivery system  90  and to an optional processor  98  and image recorder and/or viewer  100 . The fluid delivery system  90  may generally comprise a pump  92  and an optional valve  94  for controlling the flow rate of the fluid into the system. A fluid reservoir  96 , fluidly connected to pump  92 , may hold the fluid to be pumped through imaging hood  12 . An optional central processing unit or processor  98  may be in electrical communication with fluid delivery system  90  for controlling flow parameters such as the flow rate and/or velocity of the pumped fluid. The processor  98  may also be in electrical communication with an image recorder and/or viewer  100  for directly viewing the images of tissue received from within imaging hood  12 . Imager recorder and/or viewer  100  may also be used not only to record the image but also the location of the viewed tissue region, if so desired. 
     Optionally, processor  98  may also be utilized to coordinate the fluid flow and the image capture. For instance, processor  98  may be programmed to provide for fluid flow from reservoir  96  until the tissue area has been displaced of blood to obtain a clear image. Once the image has been determined to be sufficiently clear, either visually by a practitioner or by computer, an image of the tissue may be captured automatically by recorder  100  and pump  92  may be automatically stopped or slowed by processor  98  to cease the fluid flow into the patient. Other variations for fluid delivery and image capture are, of course, possible and the aforementioned configuration is intended only to be illustrative and not limiting. 
       FIG. 8B  shows a further illustration of a hand-held variation of the fluid delivery and tissue manipulation system  110 . In this variation, system  110  may have a housing or handle assembly  112  which can be held or manipulated by the physician from outside the patient body. The fluid reservoir  114 , shown in this variation as a syringe, can be fluidly coupled to the handle assembly  112  and actuated via a pumping mechanism  116 , e.g., lead screw. Fluid reservoir  114  may be a simple reservoir separated from the handle assembly  112  and fluidly coupled to handle assembly  112  via one or more tubes. The fluid flow rate and other mechanisms may be metered by the electronic controller  118 . 
     Deployment of imaging hood  12  may be actuated by a hood deployment switch  120  located on the handle assembly  112  while dispensation of the fluid from reservoir  114  may be actuated by a fluid deployment switch  122 , which can be electrically coupled to the controller  118 . Controller  118  may also be electrically coupled to a wired or wireless antenna  124  optionally integrated with the handle assembly  112 , as shown in the figure. The wireless antenna  124  can be used to wirelessly transmit images captured from the imaging hood  12  to a receiver, e.g., via Bluetooth® wireless technology (Bluetooth SIG, Inc., Bellevue, Wash.), RF, etc., for viewing on a monitor  128  or for recording for later viewing. 
     Articulation control of the deployment catheter  16 , or a delivery catheter or sheath  14  through which the deployment catheter  16  may be delivered, may be accomplished by computer control, as described above, in which case an additional controller may be utilized with handle assembly  112 . In the case of manual articulation, handle assembly  112  may incorporate one or more articulation controls  126  for manual manipulation of the position of deployment catheter  16 . Handle assembly  112  may also define one or more instrument ports  130  through which a number of intravascular tools may be passed for tissue manipulation and treatment within imaging hood  12 , as described further below. Furthermore, in certain procedures, fluid or debris may be sucked into imaging hood  12  for evacuation from the patient body by optionally fluidly coupling a suction pump  132  to handle assembly  112  or directly to deployment catheter  16 . 
     As described above, fluid may be pumped continuously into imaging hood  12  to provide for clear viewing of the underlying tissue. Alternatively, fluid may be pumped temporarily or sporadically only until a clear view of the tissue is available to be imaged and recorded, at which point the fluid flow may cease and the blood may be allowed to seep or flow back into imaging hood  12 .  FIGS. 9A to 9C  illustrate an example of capturing several images of the tissue at multiple regions. Deployment catheter  16  may be desirably positioned and imaging hood  12  deployed and brought into position against a region of tissue to be imaged, in this example the tissue surrounding a mitral valve MV within the left atrium of a patient&#39;s heart. The imaging hood  12  may be optionally anchored to the tissue, as described above, and then cleared by pumping the imaging fluid into the hood  12 . Once sufficiently clear, the tissue may be visualized and the image captured by control electronics  118 . The first captured image  140  may be stored and/or transmitted wirelessly  124  to a monitor  128  for viewing by the physician, as shown in  FIG. 9A . 
     The deployment catheter  16  may be then repositioned to an adjacent portion of mitral valve MV, as shown in  FIG. 9B , where the process may be repeated to capture a second image  142  for viewing and/or recording. The deployment catheter  16  may again be repositioned to another region of tissue, as shown in  FIG. 9C , where a third image  144  may be captured for viewing and/or recording. This procedure may be repeated as many times as necessary for capturing a comprehensive image of the tissue surrounding mitral valve MV, or any other tissue region. When the deployment catheter  16  and imaging hood  12  is repositioned from tissue region to tissue region, the pump may be stopped during positioning and blood or surrounding fluid may be allowed to enter within imaging hood  12  until the tissue is to be imaged, where the imaging hood  12  may be cleared, as above. 
     As mentioned above, when the imaging hood  12  is cleared by pumping the imaging fluid within for clearing the blood or other bodily fluid, the fluid may be pumped continuously to maintain the imaging fluid within the hood  12  at a positive pressure or it may be pumped under computer control for slowing or stopping the fluid flow into the hood  12  upon detection of various parameters or until a clear image of the underlying tissue is obtained. The control electronics  118  may also be programmed to coordinate the fluid flow into the imaging hood  12  with various physical parameters to maintain a clear image within imaging hood  12 . 
     One example is shown in  FIG. 10A  which shows a chart  150  illustrating how fluid pressure within the imaging hood  12  may be coordinated with the surrounding blood pressure. Chart  150  shows the cyclical blood pressure  156  alternating between diastolic pressure  152  and systolic pressure  154  over time T due to the beating motion of the patient heart. The fluid pressure of the imaging fluid, indicated by plot  160 , within imaging hood  12  may be automatically timed to correspond to the blood pressure changes  160  such that an increased pressure is maintained within imaging hood  12  which is consistently above the blood pressure  156  by a slight increase ΔP, as illustrated by the pressure difference at the peak systolic pressure  158 . This pressure difference, ΔP, may be maintained within imaging hood  12  over the pressure variance of the surrounding blood pressure to maintain a positive imaging fluid pressure within imaging hood  12  to maintain a clear view of the underlying tissue. One benefit of maintaining a constant ΔP is a constant flow and maintenance of a clear field. 
       FIG. 10B  shows a chart  162  illustrating another variation for maintaining a clear view of the underlying tissue where one or more sensors within the imaging hood  12 , as described in further detail below, may be configured to sense pressure changes within the imaging hood  12  and to correspondingly increase the imaging fluid pressure within imaging hood  12 . This may result in a time delay, ΔT, as illustrated by the shifted fluid pressure  160  relative to the cycling blood pressure  156 , although the time delay ΔT may be negligible in maintaining the clear image of the underlying tissue. Predictive software algorithms can also be used to substantially eliminate this time delay by predicting when the next pressure wave peak will arrive and by increasing the pressure ahead of the pressure wave&#39;s arrival by an amount of time equal to the aforementioned time delay to essentially cancel the time delay out. 
     The variations in fluid pressure within imaging hood  12  may be accomplished in part due to the nature of imaging hood  12 . An inflatable balloon, which is conventionally utilized for imaging tissue, may be affected by the surrounding blood pressure changes. On the other hand, an imaging hood  12  retains a constant volume therewithin and is structurally unaffected by the surrounding blood pressure changes, thus allowing for pressure increases therewithin. The material that hood  12  is made from may also contribute to the manner in which the pressure is modulated within this hood  12 . A stiffer hood material, such as high durometer polyurethane or Nylon, may facilitate the maintaining of an open hood when deployed. On the other hand, a relatively lower durometer or softer material, such as a low durometer PVC or polyurethane, may collapse from the surrounding fluid pressure and may not adequately maintain a deployed or expanded hood. 
     With respect to variations in fluid pressure within imaging hood  12 , pressure and/or flow rate of the purging fluid injected into hood  12  may be controlled by the user manually or automatically. For instance, the user may simply actuate a control such that the fluid injects into hood  12  at a pre-set flow rate, which may be linear or non-linear. In other variations, the user may control the flow rate by controlling the degree of actuation. As illustrated in  FIG. 11  A, user  170  may depress actuator  172 , in this variation configured as a foot pedal or foot switch which may be depressed anywhere from an initial position A to a fully depressed position B. Depending upon the controller connected to actuator  172 , the user  170  may depress the switch some distance d to increase flow rate. As mentioned, the flow rate may be pre-set to inject the fluid along a linear rate  180  or any variation of non-linear rates  182   184 , e.g., exponential, logarithmic, etc., as shown in the exemplary plot in  FIG. 11B . 
     Aside from controlling the fluid purging rate, hood  12  may be configured in other variations to effect alternative procedures. For instance,  FIGS. 12A to 12C  illustrates one variation where hood  12  may be configured to have a pullwire  192  passed around the circumference or lip  194  of the hood  12  to aid in capturing debris, such as emboli, tissue, etc., which may be errant in the surrounding blood. Pullwire  192  may be passed through catheter  16  and through an incompressible lumened structure such as coiled body  190  and around the hood  12 , as shown in  FIG. 12A . With hood  12  deployed, errant debris  198  may be visualized, as above, and captured within opening  196  of hood  12 , as shown in  FIG. 12B . With debris  198  disposed within hood  12 , pullwire  192  may be actuated and pulled proximally to collapse the circumference or lip  194  of the hood  12  to securely trap debris  198  within, as shown in  FIG. 12C . Deployment catheter  16  and hood  12  may then be withdrawn from the body to safely remove debris  198 . 
     In another variation, deployment catheter  16  and hood  12  may also be utilized to visualize debris  204 , such as blood clots, etc., utilizing the fluid displacement described herein, in various regions of the body, such as the chambers of the heart like the left ventricle LV, as shown in  FIG. 13 . The apex AP of the heart is also illustrated for reference. In this variation, hood  12  may be used to purge the opaque blood from the region to visualize debris  204  which may be lodged within the chamber. Once directly visualized, an instrument such as a biopsy instrument or thrombectomy-type catheter  200  having an opening  202  may be advanced into proximity to or directly against the debris  204  where it may be actuated to begin extraction and removal of the debris. 
     To facilitate use of the devices for any of the procedures described herein, hood  12  may be integrated with one or more angled projections  214  extending distally from hood  12 , as shown in  FIG. 14 . Once hood  12  is contacted against a tissue region, projections  214  may be engaged into the tissue by rotating catheter shaft  16  to temporarily secure the hood  12  against the tissue surface. Disengagement may be accomplished by simply rotating catheter shaft  16  in the opposite direction. 
     Catheter shaft  16  may also additionally incorporate a guidewire exchange lumen  212  defined along catheter  16  proximally of hood  12 . Lumen  212  may allow for the rapid exchange of devices, including the catheter  16  and hood  12 , during an interventional procedure when utilized with guidewire  210 . 
     In yet another variation for utilizing the deployment catheter  16  and imaging hood  12 , the catheter  16  may be used to facilitate the crossing of tissue regions, e.g., through an atrial-septal defect (ASD) or patent foramen ovale (PFO) or through an artificially-created opening or fistula, for accessing other body lumens. As illustrated in  FIGS. 15A to 15D , deployment catheter  16  and hood  12  may be articulated to identify a region of tissue, such as the atrial-septal wall AS having a septal defect such as PFO  220 . Once identified, an optional outer catheter sheath  222  may be advanced distally over deployment catheter  16  and hood  12  to retract the hood  12  into its low-profile configuration, as shown in  FIG. 15B . Then, utilizing an optional guidewire or by simply urging the sheath  222  and deployment catheter  16  distally through the opening  220 , as shown in  FIG. 15C , the deployment catheter  16  and imaging hood  12  may be penetrated to access the opposite body lumen. Once the distal opening of sheath  222  is cleared of opening  220 , deployment catheter  16  and imaging hood  12  may be projected from sheath  222  to allow the imaging hood  12  to redeploy into its expanded configuration, as shown in  FIG. 15D . 
     When imaging through hood  12 , saline may be infused into the hood  12  to purge the blood and allow for direct visualization of the underlying tissue, as described above. In certain procedures requiring extended periods of time, another variation of the visualization device may be utilized to prevent excessive amounts of saline from being infused into a patient body. One variation is illustrated in  FIG. 16 , which shows imaging hood  12  disposed upon the end of a deployment catheter  230  configured to draw blood which may be infused with excessive amounts of saline into entry ports  232  defined along catheter shaft  230 . The drawn blood may be passed proximally through catheter  230  through lumen  236 , which may be fluidly coupled to a pump  242 , such as a peristaltic pump, located in filtering assembly  240 . The withdrawn diluted blood may be passed through filter  244 , where excess water or saline may be extracted via aquaphoresis. The filtered blood may then be pumped back through catheter  230  via lumen  238  and out through one or more exit ports  234 , where the blood may be re-infused back into the patient body to maintain the fluid balance of the patient. 
     The applications of the disclosed invention discussed above are not limited to certain treatments or regions of the body, but may include any number of other treatments and areas of the body. Modification of the above-described methods and devices for carrying out the invention, and variations of aspects of the invention that are obvious to those of skill in the arts are intended to be within the scope of this disclosure. Moreover, various combinations of aspects between examples are also contemplated and are considered to be within the scope of this disclosure as well.