Patent Publication Number: US-2016220103-A1

Title: Space-optimized visualization catheter having a camera train holder in a catheter with off-centred lumens

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a continuation of U.S. Non-Provisional application Ser. No. 13/728,334, filed Dec. 27, 2012 (now U.S. Pat. No. 9,307,893), which claims the benefit of U.S. Provisional Application No. 61/581,394, filed Dec. 29, 2011. The contents of U.S. Non-Provisional application Ser. No. 13/728,334 (now U.S. Pat. No. 9,307,893) and U.S. Provisional Application No. 61/581,394 are incorporated by reference in their entirety. 
    
    
     TECHNICAL FIELD 
     The present invention relates to medical devices and more specifically, visualization catheters. 
     BACKGROUND 
     Endoscopes are routinely used to provide direct visualization to medical personnel while performing medical procedures. To enable medical personnel to reach smaller portions of the anatomy, medical personnel often use a “baby scope.” Baby scopes are visualization catheters that are configured for disposition through a working channel of an endoscope. However, known baby scopes are difficult to use and the working channel, fluid lumen, and light lumens disposed therein are too small and/or too few in number to efficiently perform many medical procedures. 
     The size of the outer diameter of the baby scope is generally fixed at 3.5 mm. The internal working space available for working channel lumens, fluid lumens, and light lumens are dictated by numerous factors. Such factors, which alone or in combination contribute to a large outer diameter or reduced interior work space, include, but are not limited to, the thickness of the catheter wall, the amount and size of cabling, lighting equipment, working channel lumens disposed therein, the image gathering equipment (such as charge coupled device (“CCD”) technology) utilized to gather an image, as well as the devices necessary to maintain the proper position of each of the devices disposed within the baby scope. In other words, in the case of a CCD-equipped baby scope, the CCD sensor must be held in proper position along with all the cables, power supplies, and other equipment necessary to enable the CCD sensor to capture an image. The extraneous materials necessary to properly position the camera equipment such that it can gather an image utilize valuable space within a baby scope. 
     Present baby scopes suffer from additional drawbacks in addition to their minimal internal working space. These drawbacks include, but are not limited to, poor image quality and ability to capture an image from, for example, the use of bulky camera equipment. 
     BRIEF SUMMARY 
     In a first aspect, a visualization catheter is provided. The visualization catheter includes a catheter having a proximal catheter portion; a distal catheter portion; and a working channel lumen extending through the proximal catheter portion and the distal catheter portion. The catheter also has a cabling lumen extending through the proximal catheter portion and the distal catheter portion and adjacent to the working channel lumen; and a notch disposed into an inner surface of the distal catheter portion. The notch is off-centered from the cabling lumen and connected to the cabling lumen. In addition, the visualization catheter includes a camera train holder that has a proximal camera train holder portion configured to receive a visualization sensor; and a distal camera train holder portion configured to receive a lens stack. The camera train holder is disposed within the notch of the catheter. 
     In a second aspect, a second visualization catheter is provided. The second visualization catheter includes a catheter that has a proximal catheter portion; a distal catheter portion having a taper; a working channel lumen extending through the proximal catheter portion and the distal catheter portion, wherein the working channel exits at a side of the catheter; a cabling lumen extending through the proximal catheter portion and the distal catheter portion and adjacent to the working channel lumen; and a notch disposed into an inner surface of the distal catheter portion. The notch is off-centered from the cabling lumen and connected to the cabling lumen. In addition, the second visualization catheter includes a camera train holder that has a proximal camera train holder portion configured to receive a visualization sensor; and a distal camera train holder portion configured to receive a lens stack. The camera train holder is disposed within the notch of the catheter. 
     In a third aspect, a method of manufacturing a visualization catheter is provided. The method of manufacturing includes extruding a catheter that has a proximal catheter portion; a distal catheter portion; a working channel lumen extending through the proximal catheter portion and the distal catheter portion; and a cabling lumen extending through the proximal catheter portion and the distal catheter portion and adjacent to the working channel lumen. The method also includes removing a notch from an inner surface of the distal catheter portion. The notch is off-centered from the cabling lumen and connected to the cabling lumen. In addition, the method includes providing a camera train holder that has a proximal camera train holder portion configured to receive a visualization sensor, and a distal camera train holder portion configured to receive a lens stack. The method further includes coupling the camera train holder into the notch of the catheter. 
    
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
       The embodiments will be further described in connection with the attached drawing figures. It is intended that the drawings included as a part of this specification be illustrative of the exemplary embodiments and should in no way be considered as a limitation on the scope of the invention. Indeed, the present disclosure specifically contemplates other embodiments not illustrated but intended to be included in the claims. Moreover, it is understood that the figures are not necessarily drawn to scale. 
         FIG. 1A  illustrates a perspective view of a conventional CMOS sensor holder; 
         FIG. 1B  illustrates a rear view of the conventional CMOS sensor holder illustrated in  FIG. 1A ; 
         FIG. 1C  illustrates a schematic front view of a conventional catheter utilizing the conventional holder illustrated in  FIG. 1A ; 
         FIG. 2A  illustrates a perspective view of a first embodiment of a space-optimized visualization catheter; 
         FIG. 2B  illustrates a bottom perspective view of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 3  illustrates a perspective view of a CMOS sensor of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 4  illustrates a cross-sectional perspective view of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 5  illustrates a partially stripped perspective view of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 6  illustrates an exploded perspective view of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 7  illustrates a perspective view of an illustrative camera train holder of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 8  illustrates a front view of the proximal portion of the space-optimized visualization catheter illustrated in  FIG. 2A ; 
         FIG. 9  illustrates a back view of the proximal portion of that which is illustrated in  FIG. 8 ; 
         FIG. 10  illustrates a cross-sectional view along the line A-A illustrated in  FIG. 4 ; 
         FIG. 11  illustrates a cross-sectional view along the line B-B illustrated in  FIG. 4 ; 
         FIG. 12  illustrates a perspective view of a second embodiment of a space-optimized visualization catheter; 
         FIG. 13  illustrates a perspective view of a second embodiment of a camera train holder for use with the space-optimized visualization catheter illustrated in  FIG. 12 ; 
         FIG. 14  illustrates a back view of the camera train holder illustrated in  FIG. 13 ; 
         FIG. 15  illustrates a perspective view of another embodiment of a space-optimized visualization catheter; 
         FIG. 16  illustrates a perspective view of another embodiment of a camera train holder for use with the space-optimized visualization catheter illustrated in  FIG. 15 ; 
         FIG. 16A  illustrates a perspective view of an alternate embodiment of the camera train holder for use with the space-optimized visualization catheter illustrated in  FIG. 15 ; 
         FIG. 17  illustrates a cross-sectional perspective view of the camera train holder illustrated in  FIG. 16 ; 
         FIG. 17A  illustrates a perspective view of a lens stack configured to have two cross-sectional profiles. 
         FIG. 18  illustrates a perspective view of another embodiment of a space-optimized visualization catheter; 
         FIG. 19  illustrates a cross-sectional perspective view of the space-optimized visualization catheter illustrated in  FIG. 18 ; 
         FIG. 20  illustrates a schematic view of the space-optimized visualization catheter illustrated in  FIG. 18 ; 
         FIG. 20A  illustrates a perspective view of an alternate embodiment of a space-optimized visualization catheter; 
         FIG. 20B  illustrates a cross-sectional perspective view of the space-optimized visualization catheter illustrated in  FIG. 20A ; 
         FIG. 21  illustrates a perspective view of another embodiment of a space-optimized visualization catheter; 
         FIG. 22  illustrates a cross-sectional perspective view of the space-optimized visualization catheter illustrated in  FIG. 21 ; 
         FIG. 23  illustrates a front view of the space-optimized visualization catheter illustrated in  FIG. 21 ; 
         FIG. 24  illustrates a perspective view of another embodiment of a space-optimized visualization catheter; 
         FIG. 25  illustrates a perspective view of a camera train holder for use with the space-optimized visualization catheter illustrated in  FIG. 24 ; 
         FIG. 26  illustrates a perspective back-view of the camera train holder illustrated in  FIG. 25 ; 
         FIG. 27  illustrates a perspective view of another embodiment of a space-optimized visualization catheter; 
         FIG. 28  illustrates a schematic view of the space-optimized visualization catheter illustrated in  FIG. 27 ; and 
         FIG. 29  illustrates the space-optimized visualization catheter illustrated in  FIG. 27  in use. 
     
    
    
     DETAILED DESCRIPTION OF PRESENTLY PREFERRED EMBODIMENTS 
     The exemplary embodiments illustrated provide the discovery of methods and apparatuses for visualization catheters that utilize a visualization sensor, including but not limited to, complimentary metal-oxide-semi-conductor (“CMOS”) sensor technology integrated into a CMOS camera train holder system that may be a stand-alone component for use with a visualization catheter, such as a baby endoscope, or may be fabricated/extruded as a part of the catheter itself. Embodiments of apparatuses, methods, and equivalents thereto provide many benefits, including but not limited to, better direct visual feedback to the medical personnel performing the procedure while providing a similarly-sized outer diameter visualization catheter device having more space therein for additional lumens and equipment than present baby scopes or by utilizing a smaller outer diameter visualization catheter. 
     Diseases and conditions contemplated for treatment include, but are not limited to, those involving the gastrointestinal region, esophageal region, duodenum region, biliary region, colonic region, urological region (e.g., kidney, bladder, urethra), ear, nose, and throat (e.g., nasal/sinus) region, bronchial region, as well as any other bodily region or field benefiting from direct visualization of a target site for treatment or diagnosis. 
     The present invention is not limited to those embodiments illustrated herein, but rather, the disclosure includes all equivalents including those of different shapes, sizes, and configurations, including but not limited to, other types of visualization catheters and component parts. The devices and methods may be used in any field benefiting from a visualization catheter or parts used in conjunction with visualization catheters. Additionally, the devices and methods are not limited to being used with human beings; others are contemplated, including but not limited to, animals. 
     Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. In case of conflict, the present document, including definitions, will control. Preferred methods and materials are illustrated below, although apparatuses, methods, and materials similar or equivalent to those illustrated herein may be used in practice or testing. All publications, patent applications, patents and other references mentioned herein are incorporated by reference in their entirety. The materials, methods, and examples disclosed herein are illustrative only and not intended to be limiting. 
     The terms “comprise(s),” “include(s),” “having,” “has,” “can,” “contain(s),” and variants thereof, as used herein, are intended to be open-ended transitional phrases, terms, or words that do not preclude the possibility of additional acts or structures. The present disclosure also contemplates other embodiments “comprising,” “consisting of” and “consisting essentially of,” the embodiments or elements presented herein, whether explicitly set forth or not. 
     The term “proximal,” as used herein, refers to a direction that is generally towards a physician during a medical procedure. 
     The term “distal,” as used herein, refers to a direction that is generally towards a target site within a patient&#39;s anatomy during a medical procedure. 
       FIG. 1A  illustrates a perspective view of conventional CMOS sensor holder CH,  FIG. 1B  illustrates a rear view of conventional CMOS sensor holder CH illustrated in  FIG. 1A , and  FIG. 1C  illustrates a schematic front view of conventional catheter CC utilizing conventional CMOS sensor holder CH illustrated in  FIG. 1A . Referring to  FIGS. 1A-1C , conventional holder CH is 2.6 mm in diameter and is composed of two pieces of stainless steel tubing: inner tubing IT and outer tubing OT. Inner piece of tubing IT is used to secure CMOS sensor CS to a plane that is perpendicular to the optical axis of the telecentric lens stack LS. Outer piece of tubing OT is used to hold lens stack LS and can move parallel to the optical axis to fine tune the depth of field. Even though conventional holder CH illustrated in  FIGS. 1A-1C  is configured to fit the diagonal of the square CMOS image sensor CS, the design does not optimize the space that drives the outer diameter of conventional holder CH and conventional catheter CC. This space is composed of working channel WC, conventional CMOS sensor holder CH, and the three webs of the catheter as illustrated in  FIG. 1C . 
     Referring to  FIG. 1C , outer diameter OD of conventional catheter CC is the sum of D 1 +D 2 +W 1 +W 2 +W 3 , where D 1  is the diameter of conventional holder CH; D 2  is the diameter of working channel WC; and W 1 , W 2 , and W 3  are each conventional catheter CC webbing. if outer diameter OD of conventional catheter CC is fixed and cannot be larger than 3.5 mm, CMOS sensor CS has a fixed size of 1.8 mm×1.8 mm square, and working channel WC must be maximized, then the sensor holder must be configured to be as small as possible and the webs of the devices must be as thin as possible. 
     A more detailed description of the embodiments will now be given with reference to  FIGS. 2A-29 . Throughout the disclosure, like reference numerals and letters refer to like elements. The present disclosure is not limited to the embodiments illustrated; to the contrary, the present disclosure specifically contemplates other embodiments not illustrated but intended to be included in the claims. 
       FIG. 2A  illustrates a perspective view of space-optimized visualization catheter  100 , and  FIG. 2B  illustrates a bottom perspective view of space-optimized visualization catheter  100 . Space-optimized visualization catheter  100  has proximal portion  100   a  and distal portion  100   b . Space-optimized visualization catheter  100  and equivalents thereto overcome the disadvantages with conventional catheter CC and conventional holders CH, such as those illustrated in  FIGS. 1A-1C . 
     Referring to  FIGS. 2A-2B , space-optimized visualization catheter  100  includes outer sheath  104 . Disposed within outer sheath  104  are camera train holder  114 , inner catheter  102 , outer sheath  104 , illumination fibers  106 , flushing voids  108 , working channel  110 , and image capturing surface  112  of lens stack  118 . For illustrative purposes only, outer sheath  104 , illumination fibers  106 , and inner catheter  102  are illustrated truncated and generally would extend proximally to a control handle (not shown) of the device. 
     Space-optimized visualization catheter  100  and equivalents thereto solve and provide solutions to numerous challenges facing known baby scopes. For example, space-optimized visualization catheter  100  and equivalents thereto solve the problem of constraints of space, which arise from the need to limit the overall size (e.g., the outer diameter) of the transverse cross-section of scopes. With the overall cross-section limited, the available space should be judiciously allocated to elements that perform important functions. 
     Space-optimized visualization catheter  100  and equivalents thereto manage and address at least four important scope functions vying for space: image capture, working channel, flushing, and illumination. Generally, the functions of image capture and the working channel together drive the overall diameter of the cross-section thereby leaving the flushing and illumination functions competing for any space that remains. 
     Space-optimized visualization catheter  100  and equivalents thereto also provide a solution to numerous secondary challenges facing known baby scopes. For example, space-optimized visualization catheter  100  and equivalents thereto solve the problems of ease of construction, component cost, optimization of materials for function, sealing of opto-electronic components and connections against moisture and light, ability to properly align the lens system to the sensor image plane, ability to focus images onto the sensor image plane, and ability to direct the light emanating from the illumination system. 
       FIG. 3  illustrates a perspective view of CMOS sensor  116  of space-optimized visualization catheter  100  illustrated in  FIG. 2A . Referring to  FIGS. 2A-3 , disposed within outer sheath  104  is camera train holder  114  which houses CMOS sensor  116  in proper relation to lens stack  118 . CMOS sensor  116  is a visualization sensor and preferably is approximately the shape of a square tile although other shapes and configurations are contemplated. One side of CMOS sensor  116  is configured to receive an image and includes a thickness of transparent glass (cover glass)  117 . The other side of CMOS sensor  116  includes an integrated circuit (IC die)  124  and is configured for electrical connection with raised solder balls  122 . Image plane  126  lies within CMOS sensor  116  at a surface that forms the junction between IC die  124  and cover glass  117 . 
       FIG. 4  illustrates a cross-sectional perspective view of space-optimized visualization catheter  100  illustrated in  FIG. 2A , and  FIG. 5  illustrates a partially stripped perspective view of space-optimized visualization catheter  100  illustrated in  FIG. 2A . Referring to  FIGS. 4-5 , for illustrative purposes only, outer sheath  104 , illumination fibers  106 , and inner catheter  102  are illustrated truncated and generally would extend proximally to a control handle (not shown) of the device. 
     Referring to  FIGS. 2A-5 , lens stack  118  is composed of one or more lens elements, including but not limited to, glass, polymer, or combination thereof. It is contemplated that lens stack  118  may further include one or more coatings, filters, apertures, or combinations thereof. Lens stack  118  is housed within lens holder  120 . Lens holder  120  is preferably a thin-walled cylindrical element configured for holding lens stack  118 . It is preferred that lens holder  120  be made from a stainless steel hypodermic tube, although other materials and configurations are contemplated. Not illustrated is the electrical cabling assembly that would generally extend along the length of space-optimized visualization catheter  100  and connect to solder balls  122  of CMOS sensor  116 . 
     Camera train holder  114  along with lens holder  120  together house and hold lens stack  118  and CMOS sensor  116  so as to orient image plane  126  perpendicular and centered with respect to the central axis of lens stack  118 . Camera train holder  114  along with lens holder  120  together also shield the periphery of CMOS sensor  116  from stray light to reduce or eliminate imaging artifact/noise. Accordingly, any light falling upon the sides of cover glass  117  or IC die  124  are restricted so that only the light passing through lens stack  118  reaches image plane  126 . 
     Camera train holder  114  along with lens holder  120  together also permit the proximal aspect of CMOS sensor  116  comprising solder balls  122  to have electrical connections made thereupon and to be sealed from both light and fluid. This is achieved, for example, by filling the square pocket in camera train holder  114  proximal to CMOS sensor  116  with potting material, such as but not limited to, epoxy or silicone, thereby insulating the electrical cable(s) (not shown) to emerge therefrom. Accordingly, camera train holder  114 , lens stack  118 , and CMOS sensor  116  with electrical cable(s) (not shown) are sealed together forming a moisture-impervious and light-impervious (except through the lenses) camera module that may improve the image capture function. With inner catheter  102  joined thereto, camera train holder  114  also performs the function of providing an integrated working channel  110 . 
     One benefit, among many, of the manner in which lens stack  118  is housed within camera train holder  114  and lens holder  120  is that it permits lens stack  118  to be controllably moved closer to and further from image plane  126  for focusing purposes. After being focused, the position of lens stack  118  and image plane  126  are thereby fixed by using, for example, an adhesive or other material or means. Permitting the distal aspect of lens stack  118  to be sealed to camera train holder  114  prevents fluid encroachment into the interior aspects. 
       FIG. 6  illustrates an exploded perspective view of space-optimized visualization catheter  100  illustrated in  FIG. 2A , and  FIG. 7  illustrates a perspective view of illustrative camera train holder  114  of space-optimized visualization catheter  100  illustrated in  FIG. 2A . Referring to  FIGS. 6-7 , for illustrative purposes only, outer sheath  104 , illumination fibers  106 , and inner catheter  102  are illustrated truncated and generally would extend proximally to a control handle (not shown) of the device. 
     Referring to  FIGS. 2A-7 , atop camera train holder  114  are cylindrical wall features extending upwards to form the distal-most portion of working channel  110  within the overall assembly. These walls do not form a complete cylinder, but are instead truncated so that they do not extend beyond the surface formed by the inner diameter of outer sheath  104 . Thus, the proximal aspect of working channel  110  formed by the walls of camera train holder  114  is configured to receive the distal end of inner catheter  102  such that the inner diameter of inner catheter  102  is contiguous with the inner diameter of working channel  110  formed by the walls. As such, a portion of the diameter of the device equal to the wall section left out is saved. Thus, a single working channel  110  is formed from camera train holder  114  and inner catheter  102  that has a smooth, contiguous inner surface. 
     Inner catheter  102  and equivalents thereto may be affixed to camera train holder  114  by, for example, an adhesive or welding. In the region where inner catheter  102  and camera train holder  114  are joined, inner catheter  102  is co-axial with working channel  110  formed by the wall features of camera train holder  114 . 
     Proximal to where inner catheter  102  and camera train holder  114  join, a central longitudinal axis of inner catheter  102  is displaced or offset from a central longitudinal axis of work channel  110 . In one example, proximal to the where inner catheter  102  and camera train holder  114  join, the central axis of inner catheter  102  is positioned at a central axis of the entire assembly. In addition, as best illustrated in  FIG. 7 , a distal portion of an outer wall  102   a  of inner catheter  102  includes groove portion  102   b  that provides a transition from an outer surface  102   c  of outer wall  102   a  to a gap or opening  102   d  in the outer wall  102   a . The gap or opening  102   d  extends from a proximal portion of groove portion  102   b  to a distal end of the catheter  102 . In addition, groove portion  102   b  distally extends and transitions to upper surfaces  102   e . Upper surfaces  102   e  is smooth or substantially smooth. In addition, upper surface  102   e  is flush with upper surfaces  114   c  of camera train holder  114 . As shown in  FIGS. 4 and 5 , inner catheter  102  joins with camera train holder  114  so that a distance from upper surfaces  102   e  and  114   c  to a bottom-most portion of camera train holder  114  does not exceed or extend an inner diameter of outer sheath  104 . 
     At a more proximal location, where inner catheter  102  is displaced into a more central position, its walls may be left intact without interfering with the wall of outer sheath  104 . 
     Inner catheter  102  and equivalents thereto may be constructed from any flexible material but are preferably constructed from a low-friction polymer such as polytetrafluoroethylene (“PTFE”) or fluorinated ethylene propylene (“FEP”). Inner catheter  102  and equivalents thereto may also be reinforced over all or a part of the length with a braid and/or coil of metal or other relatively strong/stiff material. 
     The form of outer sheath  104  is that of a cylindrical tube. Outer sheath  104  and equivalents thereto may be made from a variety of materials but are preferably constructed from a flexible polymer reinforced with a braid and/or coil of metal or other relatively strong/stiff material to provide a flexible tube that is capable of making tight bends without collapsing or kinking. 
     The proximal ends of the electrical cable(s) (not shown) to connect with CMOS sensor  116  and inner catheter  102  may be loaded into the distal end of the outer sheath  104  and pulled therethrough to bring camera train holder  114  in close proximity to the distal end of outer sheath  104 . Camera train holder  114  assembles to outer sheath  104  in such a way as to allow camera train holder  114  to form part of the outer cylindrical surface of the assembly where a portion of the lower wall of camera train holder  114  has been removed (as is best illustrated in  FIG. 2B ). 
       FIG. 8  illustrates a front view of the proximal portion of space-optimized visualization catheter  100  illustrated in  FIG. 2A ,  FIG. 9  illustrates a back view of the proximal portion of that which is illustrated in  FIG. 8 ,  FIG. 10  illustrates a cross-sectional view along the line A-A illustrated in  FIG. 4 , and  FIG. 11  illustrates a cross-sectional view along the line B-B illustrated in  FIG. 4 . Referring to  FIGS. 2A-11 , and more particularly,  FIGS. 2B, 7, and 8-11 , one advantage, among many, of space-optimized visualization catheter  100  and equivalents thereto is to gain a reduction in diameter of the device equal to the wall left out. Receiving groove  114   a  has been formed into the lower left and right aspects of camera train holder  114  to receive the edges of outer sheath  104  where the lower wall of outer sheath  104  has been removed. Accordingly, receiving groove  114   a  is configured for coupling to outer sheath  104 . This may facilitate joining with adhesives and/or welding, but other configurations and joining methods may be used. Preferably the method would include laser welding. 
     The assembly comprising the combination of camera train holder  114  joined to outer sheath  104 , in the region of the distal tip, camera train holder  114  only occludes a portion of the space defined by the inner diameter of outer sheath  104 . Accordingly, on either side of camera train holder  114  there is a void formed between the inner surface of outer sheath  104  and the outer surface of camera train holder  114 . This space may be utilized for a variety of purposes. 
     For example, in the embodiment illustrated here, the void formed between the inner surface of outer sheath  104  and the outer surface of camera train holder  114  is utilized to provide both illumination grooves  114   b  and flushing  108  capability. There is ample space to accommodate one or more optical light fibers  106  (or bundles of fibers) for light delivery. Accordingly, as illustrated in this embodiment, four such light fibers  106  are illustrated, although more or less are contemplated. Preferably, light fibers  106  may be adhered to illumination groove  114   b  of camera train holder  114  prior to camera train holder  114  being inserted through and affixed to outer sheath  104  (as illustrated in  FIG. 5 ). However, other orders of assembly are contemplated, and fibers  106  need not necessarily be adhered to the assembly at all. 
     Still referring to  FIGS. 2A-11 , optical fibers  106  are positioned within the areas of the cross-section that most readily accommodate them, such as illumination grooves  114   b , which include shallow radiused features on the lateral and upper aspects of the outer surface of camera train holder  114 , to assist in properly positioning lighting means for lighting a target site, such as optical fibers  106  and to provide surfaces to bond them thereto, using for example, an adhesive. Light fibers  106  project light cones  106   a  therefrom, as illustrated in  FIG. 2A . The remaining space around optical fibers  106  provides a flushing means for fluid flow  108 . Accordingly, fluid may be forced to flow within the interior void  108  of outer sheath  104 , in and around the spaces about optical fibers  106  (as best illustrated in  FIGS. 8-9 ) and the outer surface of camera train holder  114 , and exit out from distal portion  100   b  of space-optimized catheter  100 . In addition, the transverse cross-sectional size of the interior void  108  may vary. For example, the size of interior void  108  is one size where camera train holder  114  does not form part of the interior of space-optimized visualization catheter  100  and another size where camera train holder  114  does form part of the interior of space-optimized visualization catheter  100 . The size of interior void  108  where camera train holder  114  does not form part of the interior is larger than the size of interior void  108  where camera train holder  114  does form part of the interior. 
     One method of assembling space-optimized visualization catheter  100 , includes but is not limited to, providing outer sheath  104 ; providing inner catheter  102 ; providing camera train holder  114 ; coupling a visualization sensor, such as CMOS sensor  116  and lens stack  118  to camera train holder  114 ; coupling inner catheter  102  to a portion of camera train holder  114  thereby forming working channel  110 ; inserting camera train holder  114  and inner catheter  110  into a lumen of outer sheath  104  such that camera train holder  114  forms a boundary of an outer surface of outer sheath  104 . Additionally, cables may be coupled to CMOS sensor  116  before camera train holder  114  and inner catheter  110  are inserted into outer sheath  104 . 
     There are numerous advantages to space-optimized visualization catheter  100  and equivalents thereto. For example, a primary challenge with present baby scopes is to limit the overall size of the transverse cross-section of the device, where the space requirements for the functions of image capture and working channel play an important role. Image quality relates very strongly to resolution (pixel count), which relates very strongly to sensor size. Also, working channel utility relates very strongly to channel size, as that determines which wireguides and other devices may be passed therethrough. Thus, the larger the sensor and working channel may be, the more useful the catheter may be. Nevertheless, the overall size of the catheter is also a limiting factor when, for example, the catheter is to be placed in a narrowly restricted body lumen and/or through a channel within a larger instrument, such as a duodenoscope. Thus, optimization of a design with respect to these factors (sensor size, channel size, overall size) is important. Space-optimized visualization catheter  100  and equivalents thereto address these challenges in significant, discovered ways. 
     For example, camera train holder  114  forms part of the outer cylindrical surface of space-optimized visualization catheter  100  together with outer sheath  104 . One advantage of this is that it permits the square pocket that is configured to house CMOS sensor  116  (at best illustrated in  FIGS. 8-11 ) to be moved much closer to the outer cylindrical surface of space-optimized visualization catheter  100 . Accordingly, the material between the outermost edges of the square pocket can be relatively thin if the material utilized is relatively rigid and/or strong. 
     For space-optimized visualization catheter  100  and equivalents thereto, materials for outer sheath  104  construction are typically and ideally relatively soft and flexible in comparison to materials that may be used to fabricate camera train holder  114 , such as metals or high performance polymers for injection molding. Thus, by forming camera train holder  114  from a relatively stronger and/or more rigid material than outer sheath  104 , space may be gained in the cross-section by moving CMOS sensor  116  closer to the outer cylindrical surface of space-optimized visualization catheter  100 . 
     Another advantage, for example, of space-optimized visualization catheter  100  and equivalents thereto is that working channel  110  is formed primarily from a separate inner catheter  102  that is distinct from outer sheath  104 . One advantage, among many, is that such a configuration allows for optimization of materials for the purpose. In other words, the materials from which inner catheter  102  may be manufactured may include a low-friction polymer; other materials are contemplated. Thus, because working channel  110  is not integral to outer sheath  104 , the material from which the assembly may be made is not in conflict with one another. Thus, space-optimized visualization catheter  100  and equivalents thereto does not require a) a compromise in performance of one or both of the functions, or b) a more complex construction, e.g., such as a reinforced flexible outer sheath with an integral second lumen for a working channel that is lined with a thin membrane of low-friction polymer such a construct may be more costly to produce and may also require more space. 
     Another advantage, for example, of space-optimized visualization catheter  100  and equivalents thereto is that distal working channel  110  is formed from cylindrical walls integral to camera train holder  114  that are joined to inner catheter  102 . One advantage, among many, is that such a construction permits the location of working channel  110  within the cross-section to be controlled and optimized for space at a location along the length of space-optimized visualization catheter  100  where it is generally most important, i.e., at the distal end where a camera module (sensor &amp; lens) must also be accommodated. This is primarily enabled via the utilization of relatively stiff and/or strong materials of construction for camera train holder  114 . 
     The distal-most aspect of working channel  110  is configured from the relatively rigid material of camera train holder  114 . This permits the location of working channel  110  to be moved further towards the outside surface of the overall assembly than would be possible otherwise. Specifically, the material of camera train holder  114  is strong/stiff enough to permit forming working channel  110  from walls that do not form a complete cylinder, but instead are truncated so that they do not extend beyond the surface formed by the inner diameter of outer sheath  104 . Second, the relatively rigid material of camera train holder  114  permits the wall between the lumen of working channel  110  and the sensor/lens assembly to be relatively thin, which reduces the size of the overall assembly. 
     Another advantage, for example, of space-optimized visualization catheter  100  and equivalents thereto is that camera train holder  114  includes only minimal features for locating/fixing the positions of illumination fibers  106  within the assembly, which leaves more space for flushing  108 . By contrast, if a catheter with dedicated illumination channels were provided, the walls forming those channels may consume important space. Instead, illumination fibers  106  illustrated are permitted to reside in spaces where they are accommodated and partially positioned by the outer surface of camera train holder  114  on one side/aspect (illumination grooves  114   b ) and outer sheath  104  on another. Beyond that, only minimal features are included to further stabilize the positions. 
     Another advantage, for example, of space-optimized visualization catheter  100  and equivalents thereto is that the distal-most portion of camera train holder  114  includes void  114   b  (such as a notch, groove, or recess) between the walls forming the distal end of working channel  110  and the lower aspect of camera train holder  114  that forms the outer surface of space-optimized visualization catheter  100 . Void  114   b  provides a space into which the distal portion of illumination fibers  106  may be directed in order to better direct the light emanating therefrom to the target site without constructing a separate chamber or lumen to house light fibers  106  (which may add bulk and reduce space). This provides more versatility for optimization of lighting than if the perimeter of camera train holder  114  were constant from the region of CMOS sensor  116  to the distal face of camera train holder  114 . 
     Another advantage, for example, of space-optimized visualization catheter  100  and equivalents thereto is that the capability for flushing is accomplished “in the negative.” In other words, there are no included features intended solely or specifically to guide fluid for flushing, but rather, flushing void  108  is bound by the inner surface of outer sheath  104  and the outer surface of camera train holder  114 . Camera train holder  114  is configured to facilitate sealing of the opto-electric components so that the entire interior of space-optimized visualization catheter  100  may be used for fluid flow  108 . One advantage to this construction is that it maximizes the area in the cross section that is available for fluid flow in the region where that is most restricted, i.e., in the region of the camera module. 
     Also, space-optimized visualization catheter  100  and equivalents thereto utilizes the full area for flow over the majority of length of space-optimized visualization catheter  100 . One advantage, among many, to this construction is that it dramatically reduces the overall resistance to flow. Accordingly, the configuration increases flow, when compared to a multi-lumen extrusion with constant cross-section and lumens dedicated to fluid that arc sized to meet the most demanding locations along the length of the assembly. 
     Increasing flow has clinical benefits, but it also may be an advantage in stabilizing or lowering the temperature of CMOS sensor  116 . A CMOS sensor that operates at temperatures above the temperature for which it was designed may experience increased noise, which may introduce imaging artifact. Thus, in cases where a CMOS sensor that was designed for use at, for example, room temperature, is selected for use in a medical catheter, which operates at body temperature, an increased flow rate may help reduce imaging artifact via cooling. 
       FIG. 12  illustrates a perspective view of a second embodiment of space-optimized visualization catheter  1200 ,  FIG. 13  illustrates a perspective view of a second embodiment of camera train holder  1202  for use with space-optimized visualization catheter  1200 , and  FIG. 14  illustrates a back view of camera train holder  1202 . Referring to  FIGS. 13-14 , camera train holder  1202  holds CMOS sensor  1204  that is square with about 1.8 mm long sides. CMOS sensor  1204  is coupled with lens stack  1206  having about a 1.75 mm diameter. As illustrated in  FIG. 12 , space-optimized visualization catheter  1200  has a 3.5 mm outer diameter and flattened holder lumen  1208 . 
     Still referring to  FIGS. 12-14 , camera train holder  1202  is about 2.6 mm in the horizontal direction and about 2.25 mm in the vertical direction. Accordingly, camera train holder  1202  includes an inner surface comprising a circular cross-sectional profile and an outer surface comprising a semi-circular cross-sectional profile such that it includes flattened surface  1210 . When compared to conventional holder CH (illustrated in  FIGS. 1A-1C ) which is 2.6 mm in diameter, camera train holder  1202  has created about 0.35 mm of space in the vertical direction. Thus, the about 0.35 mm space created by flattening top  1210  of camera train holder  1202  is added to working channel  1212 . 
     Alternatively, working channel  1212  could also fit about two 0.5 mm diameter light fibers (not shown) that may be glued or otherwise adhered to the sides of non-round working channel  1212 . The utilization of a non-circular cross-sectional profile of camera train holder  1202 , such as one having, for example, a semi-circular cross-sectional profile, permits a space-optimized means for holding CMOS sensor  1204  and lens stack  1206 . 
     Camera train holder  1202  and space-optimized visualization catheter  1200  may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
       FIG. 15  illustrates a perspective view of another embodiment of space-optimized visualization catheter  1500 ,  FIG. 16  illustrates a perspective view of another embodiment of camera train holder  1600  for use with space-optimized visualization catheter  1500 , and  FIG. 17  illustrates a cross-sectional perspective view of camera train holder  1600 . Illustrative camera train holder  1600  is configured for affixation to distal end  1500   b  of space-optimized visualization catheter  1500 . The camera train holder  1600  may be affixed to distal end  1500   b  in various ways and/or using various methods, such as welding (e.g., butt welding), reflowing, and/or using one or more mandrels. An illustration of camera train holder  1600  affixed to distal end  1500   b  is shown in  FIG. 17 . 
     Referring to  FIGS. 16 and 17 , camera train holder  1600  includes channels  1602  for a light (such as four light fibers having a diameter of 0.5 mm diameter lumens on each side of lens stack  1606 ), working channel port  1604  (such as one configured to have a diameter of about 1 mm), large flush channel  1608 , recess (not shown) for holding CMOS sensor  1612  (having dimensions of about 1.8 mm×1.8 mm), and lens stack recess  1610  for holding the components of lens stack  1606 . Camera train holder  1600  utilizes round lens  1606  that has been flanked so that it fits within the footprint of CMOS sensor  1612 . The flanking of lens stack  1606  optimizes the optical performance of lens stack  1606  and allows for more light to be focused on CMOS sensor  1612 . Other configurations are contemplated. 
     Camera train holder  1600  is joined to space-optimized visualization catheter  1500  in a fashion where the web above lens stack  1606  overlaps the bottom web of working channel  1502  of space-optimized visualization catheter  1500 . This overlapping allows for a larger working channel  1502  and allows for flushing around working channel  1502 . In addition, as shown in  FIG. 17 , working channel port  1604  is aligned or substantially aligned with working channel  1502 . Another advantage, among many, is that camera train holder  1600  allows the corner of CMOS sensor  1612  to come as close as reasonably possible (about 0.005″) to the outside wall of space-optimized visualization catheter  1500 . 
     Thus, camera train holder  1600  reduces the overall footprint by the thickness of the webs located at the top and bottom of lens stack  1606  and thus, allows for a larger working channel  1502  or smaller diameter catheter. The lens stack  1606  maximizes the optical performance while being within the footprint of CMOS sensor  1612  and therefore, it does not limit size of working channel  1604  or increase the diameter of space-optimized visualization catheter  1500 . The lens stack  1606  shown in  FIG. 17  has a circular cross-sectional profile. In an alternative lens stack configuration, the lens stack  1606  has a square cross-sectional profile.  FIG. 17A  shows a second alternative lens stack configuration of lens stack  1606 A. Lens stack  1606 A has two portions, a first portion  1650  having a square cross-sectional profile and a second portion  1652  having a circular cross-sectional profile. In one example of the second alternative configuration, as shown in  FIG. 17A , the first portion  1650  having the square cross-sectional profile conforms or substantially conforms to the cross-sectional profile of lens stack recess  1610 . 
       FIG. 16A  illustrates a perspective view of an alternate embodiment of camera train holder  1700  for use with space-optimized visualization catheter  1500 . In the alternative embodiment, camera train holder  1700  is an insert that is inserted into catheter  1500 , such as from distal end  1500   b . Inside the catheter, camera train holder insert  1700  is bonded or secured to the inner surface of catheter  1500 . Camera train holder insert  1700  includes lens stack recess  1710  similar to lens stack recess  1610  of camera train holder  1600 . Camera train holder insert  1700  also includes channels  1702  and large flush channel  1708 . Unlike channels  1602  and large flush channel  1608 , channels  1702  and large flush channel  1708  are formed in part by an inner surface of catheter  1500 . 
     An upper portion  1720  of camera train holder insert  1700  overlaps or occupies an area that is the same as an area occupied by working channel  1502 . So that camera train insert  1700  fits into catheter  1500 , a distal portion of a wall of working channel  1502  that extends a longitudinal length of the camera train insert  1700  is removed. In one configuration, as shown in  FIG. 16A , all or substantially all of the distal portion of the wall of working channel  1502  is removed. In an alternative configuration, a bottom portion (e.g., only a portion of the wall that is necessary for camera train insert  1700  to fit inside catheter  1500 ) is removed. The portion of the wall of working channel  1502  that remains helps guide insert  1700  into and/or secure insert  1700  within catheter  1500 . In the alternative configuration, a top surface of upper portion  1720  meets or contacts a bottom surface of the wall of working channel  1502 . The top surface forms part of working channel  1502  for the longitudinal length of the insert  1700 . In alternative configurations, the insert  1700  does not overlap or occupy an area occupied by working channel  1502 , in which case no portion of working channel  1502  is removed. 
     Various configurations similar to camera train holder  1600  or camera train holder  1700 , or combinations thereof, are possible. For example, working channel port  1604  of camera train holder  1600  may be included in camera train holder insert  1700  and may meet and/or be aligned with working channel  1502 , which has been recessed as previously described. 
     Space-optimized visualization catheter  1500  and camera train holders  1600 ,  1700  may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
     Considering conventional catheter CC and conventional holder CH illustrated in  FIGS. 1A-1C  compared to the improved embodiments illustrated in  FIGS. 12-17  (assuming all walls are at least 0.005″ thick and the outer diameter of the catheter is fixed at 3.5 mm) the working channel is effected in size in the following manner: conventional catheter CC and conventional holder CH (illustrated in  FIGS. 1A-1C ) provide a maximum working channel size of 0.52 mm, while space-optimized visualization catheter  1200  and camera train holder  1202  (illustrated in  FIGS. 12-14 ) provide a maximum working channel size of about 0.86 mm (a 65% increase in diameter from conventional catheter CC and conventional holder CH), and space-optimized visualization catheter  1500  and camera train holder  1600  (illustrated in  FIGS. 15, 16, and 17 ) provide a maximum working channel size of about 0.98 mm (an 88% increase in diameter from conventional catheter CC and conventional holder CH). 
       FIG. 18  illustrates a perspective view of another embodiment of space-optimized visualization catheter  1800 ,  FIG. 19  illustrates a cross-sectional perspective view of space-optimized visualization catheter  1800 , and  FIG. 20  illustrates a schematic view of space-optimized visualization catheter  1800 . Referring to  FIGS. 18-20 , space-optimized catheter  1800  preferably comprises an extruded catheter body  1804  which is modified by means of a secondary operation to receive camera train holder  1802 . Catheter body  1804  is extruded with working channel  1806 , two light lumens  1808 , four fluid lumens  1810 , and cabling lumen  1814 , although other configurations are contemplated. 
     Camera train holder  1802  is preferably a square holder having ultra-thin walls that are about 0.003″ thick, although other configurations are contemplated. Camera train holder  1802  is joined to catheter body  1804  such that the placement of lumens of catheter body  1804  are configured to maximize the diameter of working channel  1806  for the entire length of space-optimized visualization catheter  1800  with the exception being the most distal tip. For example, catheter body  1804  is composed of cabling lumen  1814  having a diameter of about 1.8 mm and working channel lumen  1806  having a diameter of about 1.2 mm. The three webs that lie along a line connecting lumens are about 0.005″ thick. 
     The secondary operation removes square notch  1804   a  which is slightly larger (in order to accommodate camera train holder  1802 ) than the 1.8 mm×1.8 mm square CMOS sensor  1812 . Square notch  1804   a  is off-center of cabling lumen  1814 . CMOS sensor  1812 , lens stack  1816 , and sensor cabling (not shown) are loaded into camera train holder  1802 . Camera train holder  1802  is then back-loaded into square notch  1804   a  of catheter body  1804  so that cabling (not shown) is fed through cabling lumen  1814 . Due to the off-centering of square notch  1804   a , the cabling (not shown) is directed down between the transition between camera train holder  1802  and catheter body  1804 . This slight off-centering of cabling lumen  1814  opens up space so that the diameter of working channel  1806  may be maximized. Thus, the smaller the cabling diameter, the larger working channel  1806  may be configured. In this embodiment, for example, cabling is assumed to have a diameter of just less than 1.8 mm, and working channel  1806  is maximized to be 1.2 mm for the entire length of catheter body  1804  with the exception of the last 7.5 mm where working channel  1806  is about 0.96 mm in diameter. The off-centering of cabling lumen  1814  with respect to camera train holder  1802  maximizes the diameter of working channel  1806  for the vast majority of the length of space-optimized catheter  1800 . 
     Space-optimized visualization catheter  1800  and equivalents thereto may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
       FIG. 20A  illustrates a perspective view of an alternate embodiment of space-optimized visualization catheter  2100 , and  FIG. 20B  illustrates a cross-sectional perspective view of the same. Referring to  FIGS. 20A-20B , catheter  2000  is similar to catheter  1800  (illustrated in  FIGS. 18-20 ), and camera train holder  2002  is similar to camera train holder  1802  (illustrated in  FIGS. 18-20 ) in terms of construction, method of use, and assembly. Space-optimized catheter  2000  preferably comprises an extruded catheter body  2004  which is modified by means of a secondary operation to receive camera train holder  2002 —similar to the means illustrated in conjunction with space-optimized visualization catheter  1800 . 
     Catheter body  2004  is extruded with working channel  2006 , two light lumens  2008 , two fluid lumens  2010 , and cabling lumen  2014 , although other configurations are contemplated. Camera train holder  2002  is preferably a square holder having ultra-thin walls that are about 0.003″ thick, although other configurations are contemplated. Camera train holder  2002  is joined to catheter body  2004  such that the placement of lumens of catheter body  2004  are configured to maximize the diameter of working channel  2006  for the entire length of space-optimized visualization catheter  2000  with the exception being the most distal tip. 
     The secondary operation removes square notch  2004   a  which is slightly larger (in order to accommodate camera train holder  2002 ) than the 1.8 mm×1.8 mm square CMOS sensor  2012 . Square notch  2004   a  is off-center of cabling lumen  2014 . CMOS sensor  2012 , lens stack  2016 , and sensor cabling (not shown) are loaded into camera train holder  2002 . Camera train holder  2002  is then back-loaded into square notch  2004   a  of catheter body  2004  so that cabling (not shown) is fed through cabling lumen  2014 . Due to the off-centering of square notch  2004   a , the cabling (not shown) is directed down between the transition between camera train holder  2002  and catheter body  2004 . This slight off-centering of cabling lumen  2014  opens up space so that the diameter of working channel  2006  may be maximized. Thus, the smaller the cabling diameter, the larger working channel  2006  may be configured. 
     Space-optimized visualization catheter  2000  and equivalents thereto may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
       FIG. 21  illustrates a perspective view of another embodiment of a space-optimized visualization catheter  2100 ,  FIG. 22  illustrates a cross-sectional perspective view of space-optimized visualization catheter  2100 , and  FIG. 20  illustrates a front view of space-optimized visualization catheter  2100 . Referring to  FIGS. 21-23 , space-optimized catheter  2100  is constructed in a manner similar to space-optimized catheter  1800  (illustrated in  FIGS. 18-20 ), wherein cabling lumen  2102  is off-center and the cable (not shown) is disposed down from CMOS sensor  2104  into cabling lumen  2102 . Catheter body  2108  also includes light lumens  2112 . 
     CMOS sensor  2104 , lens stack  2114 , and sensor cabling (not shown) are loaded into camera train holder  2110 . Camera train holder  2110  is then back-loaded into the square notch  2108   a  of catheter body  2108  so that cabling (not shown) is fed through cabling lumen  2102 . 
     Space-optimized visualization catheter  2100  includes working channel  2106  that exits at the side of catheter body  1208  so that working channel  2106  having a maximized diameter may be fully utilized. The size of working channel  2106  is primarily dependent on the size of the cabling (not shown) attached to CMOS sensor  2104 . For example, the cabling for this particular embodiment is about 1.4 mm in diameter and therefore cabling lumen  2102  is oversized to have a diameter of about 1.5 mm to accept the smaller cable. With cabling lumen  2102  having a diameter of about 1.5 mm and catheter body  1208  having an outer diameter of about 3.5 mm as a constraint, working channel  1206  may be maximized to a diameter of about 1.6 mm. With side port  1206   a  of working channel  1206  that exits at 10 mm or less from the distal tip, the configuration allows full utilization of the entirety of the 1.6 mm diameter working channel  1206  for an endoscopic accessory. This 1.6 mm diameter working channel  1206  is at least 60% larger than any lumen that exits at the distal tip when utilizing a typical 1.8 mm×1.8 mm CMOS sensor. Another advantage, among many, of this configuration is that distal tip of catheter body  2108  is tapered and therefore it should be easier to gain access to an orifice due to a smaller diameter tip. The off-centering of cabling lumen  2102  with respect to camera train holder  2110  maximizes the diameter of working channel  2106  for the vast majority of the length of space-optimized visualization catheter  2100 . The side exiting  2106   a  working channel  2106  when used in conjunction with camera train holder  2110  maximizes the diameter of working channel  2106  and therefore allows for larger accessories. 
     Space-optimized visualization catheter  2100  and equivalents thereto may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
       FIG. 24  illustrates a perspective view of another embodiment of space-optimized visualization catheter  2400 ,  FIG. 25  illustrates a perspective view of camera train holder  2402  for use with space-optimized visualization catheter  2400 , and  FIG. 26  illustrates a perspective back-view of camera train holder  2402 . Referring to  FIGS. 24-26 , catheter  2400  is similar to catheter  1500  (illustrated in  FIG. 15 ), and camera train holder  2402  is similar to camera train holder  1600  (illustrated in  FIGS. 16 and 17 ) in terms of construction, method of use, and assembly. Camera train holder  2402  is configured for affixation to distal end  2400   b  of space-optimized visualization catheter  2402 . Camera train holder  2402  includes channels  2404  for a light, working channel port  2406 , flush channel  2408 , recess (not shown) for holding CMOS sensor  2410  (having dimensions of about 1.8 mm×1.8 mm), and lens stack recess  2412  for holding the components of lens stack  2414 . Camera train holder  2402  utilizes round lens  2414  that has been flanked so that it fits within the footprint of CMOS sensor  2410 . The flanking of lens stack  2414  optimizes the optical performance of lens stack  2414  and allows for more light to be focused on CMOS sensor  2410 . Camera train holder  2402  is joined to space-optimized visualization catheter  2400  such that camera train holder  2402  is a separate component part insertable into space-optimized visualization catheter  2400  as with camera train holder  1600  (illustrated in  FIGS. 16 and 17 ). 
     Space-optimized visualization catheter  2400  and equivalents thereto may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
       FIG. 27  illustrates a perspective view of another embodiment of space-optimized visualization catheter  2700 ,  FIG. 28  illustrates a schematic view of space-optimized visualization catheter  2700 , and  FIG. 29  illustrates space-optimized visualization catheter  2700  in use. Referring to  FIGS. 27-29 , space-optimized visualization catheter  2700  has a non-circular cross-sectional profile. Space-optimized visualization catheter  2700  is similar to other space-optimized visualization catheter embodiments illustrated herein and equivalents thereto in terms of construction and assembly. Space-optimized visualization catheter  2700  includes working channel  2702 , two light lumens  2704 , two flushing lumens  2706 , and camera train holder  2708  configured for holding lens stack  2710  and CMOS sensor (not shown). Camera train holder  2708  is similar to other camera train holders illustrated herein and equivalents thereto. 
     Space-optimized visualization catheter  2700  is configured for use with duodenoscope  2800  equipped with a side-exiting accessory elevator  2802 . Elevator  2802  of duodenoscope  2800  limits the size of a circular catheter to less than 3.5 mm. However, accessory channel  2804  of duodenoscope  2800  has a diameter of 4.2 mm. Thus, by using accessory channel&#39;s elevator  2802 , there is a loss of 0.7 mm from the space available in accessory channel  2804  versus that available at the accessory channel&#39;s elevator site  2802 . Presently, manufacturers would attempt to reduce the overall size of a round catheter to less than 3.5 mm to fit through elevator site  2802 . However, space-optimized visualization catheter  2700  optimizes space by having a non-circular, oblong, cross-sectional profile. Thus, space-optimized visualization catheter  2700  may be limited to 3.5 mm on one side and up to 4.2 mm on the orthogonal side. Accordingly, a larger device is able to be utilized through accessory channel&#39;s elevator  2402 . 
     For example, a 1.5 mm and 1.7 mm forceps and basket may be directed through working channel lumen  2702  of space-optimized visualization catheter  2700  due to the increase in the size of working channel lumen  2702 . For example, using a 1.8 mm×1.8 mm CMOS sensor  2410 , if the embodiment illustrated in  FIGS. 27-28  were to have a circular cross-sectional profile (as opposed to being having an oblong cross-sectional profile), the working channel lumen would be limited to 1 mm. However, because space-optimized visualization catheter  2700  has an oblong cross-sectional profile, a 1.75 mm working channel lumen  2702  is achieved. As such, a diameter of working channel lumen  2702  of space-optimized visualization catheter  2700  is increased by 75% compared to typical catheters for disposal through accessory channel  2804  of duodenoscope  2800 . 
     Space-optimized visualization catheter  2700  and equivalents thereto may be constructed efficiently by common materials and methods of construction, including but not limited to, micro-molding, machining, and using numerous materials, including but not limited to, those illustrated in conjunction with other embodiments. 
     Space-optimized visualization catheters illustrated herein and equivalents thereto may further comprise one or more rigid portions and one or more portions more flexible than the one or more rigid portions. For example, a rigid portion of a space-optimized visualization catheter may include a portion of an outer sheath configured for receiving a camera train holder. The one or more flexible portions may be configured to aid in steering. For example, the one or more flexible portions may comprise one or more vertebrae modules. Alternatively, the one or more flexible portions may comprise ribs. Alternatively, the one or more flexible portions may comprise grooves or cuts made into the same material as that of the one or more rigid portions. Alternatively, space-optimized visualization catheters illustrated herein and equivalents thereto may be configured with a first rigid portion for accepting a camera train holder, a second portion configured for flexibility and steering ease, and a third portion configured similar to a standard flexible catheter. Alternatively, space-optimized visualization catheters illustrated herein and equivalents thereto may be configured with a soft portion and a rigid portion, wherein the interiors of each section change throughout the device to aid with steering or to achieve other benefits. 
     From the foregoing, the discovery of methods and apparatuses of space-optimized visualization catheters provides numerous benefits to the medical field. It can be seen that the embodiments illustrated and equivalents thereto as well as the methods of manufacturer may utilize machines or other resources, such as human beings, thereby reducing the time, labor, and resources required to manufacturer the embodiments. Indeed, the discovery is not limited to the embodiments illustrated herein, and the principles and methods illustrated herein can be applied and configured to any catheter and equivalents. 
     Those of skill in the art will appreciate that embodiments not expressly illustrated herein may be practiced within the scope of the present discovery, including that features illustrated herein for different embodiments may be combined with each other and/or with currently-known or future-developed technologies while remaining within the scope of the claims presented here. It is therefore intended that the foregoing detailed description be regarded as illustrative rather than limiting. It is understood that the following claims, including all equivalents, are intended to define the spirit and scope of this discovery. Furthermore, the advantages illustrated above are not necessarily the only advantages of the discovery, and it is not necessarily expected that all of the illustrated advantages will be achieved with every embodiment of the discovery.