Patent Publication Number: US-11648057-B2

Title: Optical analyzer assembly with safety shutdown system for intravascular lithotripsy device

Description:
RELATED APPLICATION 
     This application is related to and claims priority on U.S. Provisional Patent Application Ser. No. 63/186,391 filed on May 10, 2021, and entitled “OPTICAL ANALYZER ASSEMBLY WITH SAFETY SHUTDOWN SYSTEM FOR INTRAVASCULAR LITHOTRIPSY DEVICE”. To the extent permissible, the contents of U.S. Application Ser. No. 63/186,391 are incorporated in their entirety herein by reference. 
    
    
     BACKGROUND 
     Vascular lesions within vessels in the body can be associated with an increased risk for major adverse events, such as myocardial infarction, embolism, deep vein thrombosis, stroke, and the like. Severe vascular lesions can be difficult to treat and achieve patency for a physician in a clinical setting. 
     Vascular lesions may be treated using interventions such as drug therapy, balloon angioplasty, atherectomy, stent placement, vascular graft bypass, to name a few. Such interventions may not always be ideal or may require subsequent treatment to address the lesion. 
     SUMMARY 
     The present invention is directed toward a catheter system for treating a treatment site within or adjacent to a vessel wall or a heart valve. In various embodiments, the catheter system includes a light source, a balloon, a light guide and an optical analyzer assembly. The light source generates first light energy. The balloon is positionable substantially adjacent to the treatment site. The balloon has a balloon wall that defines a balloon interior that receives a balloon fluid. The light guide is configured to receive the first light energy at a guide proximal end and guide the first light energy in a first direction from the guide proximal end toward a guide distal end that is positioned within the balloon interior. The optical analyzer assembly is configured to optically analyze a second light energy from the light guide that moves in a second direction that is opposite the first direction. The optical analyzer assembly includes a safety shutdown system that is selectively activated to inhibit the first light energy from the light source from being received by the guide proximal end of the light guide. 
     In some embodiments, the catheter system further includes a pulse generator that is coupled to the light source. The pulse generator can be configured to trigger the light source to generate a source beam that is directed toward the light guide. 
     In certain embodiments, the safety shutdown system includes a safety interlock that is selectively activated to block the pulse generator from triggering the generation of the source beam with the light source. 
     In various embodiments, the safety shutdown system includes a shutter that is selectively activated to block the source beam from being directed toward the light guide. 
     In some embodiments, the first light energy induces generation of a plasma within the balloon interior. 
     In certain embodiments, the guide distal end includes a distal light receiver that receives the second light energy from within the balloon interior. The second light energy moves through the light guide in the second direction. 
     In some embodiments, the second light energy that is received by the distal light receiver is emitted from the plasma that is generated in the balloon fluid within the balloon interior. 
     In various embodiments, the second light energy that is received by the distal light receiver is optically analyzed by the optical analyzer assembly. 
     In some embodiments, the optical analyzer assembly is configured to optically determine whether or not plasma generation within the balloon interior has occurred within the balloon interior. 
     In certain embodiments, the optical analyzer assembly is configured to optically detect a failure of the light guide between the guide proximal end and the guide distal end. 
     In some embodiments, the optical analyzer assembly is configured to optically detect potential damage to the light guide at any point along a length of the light guide from the guide proximal end to the guide distal end. 
     In certain embodiments, the optical analyzer assembly includes a beamsplitter and a photodetector, the beamsplitter being configured to receive the second light energy and direct a portion of the second light energy to the photodetector. 
     In some embodiments, the optical analyzer assembly further includes an optical element that is positioned along a beam path between the beamsplitter and the photodetector, the optical element being configured to couple the portion of the second light energy to the photodetector. 
     In certain embodiments, the optical analyzer assembly can further include a second beamsplitter that is positioned along the beam path between the beamsplitter and the photodetector, the second beamsplitter being configured to receive the second light energy and direct at least a portion of the second light energy to the photodetector. 
     In some embodiments, the photodetector generates a signal based at least in part on visible light that is included with the portion of the second light energy. 
     In certain embodiments, the signal from the photodetector is amplified with an amplifier to provide an amplified signal that is directed to control electronics to determine an intensity of the plasma generation within the balloon interior. 
     In some embodiments, the optical analyzer assembly includes a beamsplitter and an imaging device, the beamsplitter being configured to receive the second light energy and direct at least a portion of the second light energy to the imaging device. 
     In certain embodiments, the light source includes a laser. 
     In some embodiments, the light source includes an infrared laser that emits the first light energy in the form of pulses of infrared light. 
     In some embodiments, the light guide includes an optical fiber. 
     The present invention is further directed toward a method for treating a treatment site within or adjacent to a vessel wall or a heart valve, comprising the steps of generating first light energy with a light source; positioning a balloon substantially adjacent to the treatment site, the balloon having a balloon wall that defines a balloon interior, the balloon interior receiving a balloon fluid; receiving the first light energy at a guide proximal end of a light guide; guiding the first light energy in a first direction from the guide proximal end toward a guide distal end that is positioned within the balloon interior; and optically analyzing a second light energy from the light guide that moves in a second direction that is opposite the first direction, the optical analyzer assembly including a safety shutdown system that is selectively activated to inhibit the first light energy from the light source from being received by the guide proximal end of the light guide. 
     This summary is an overview of some of the teachings of the present application and is not intended to be an exclusive or exhaustive treatment of the present subject matter. Further details are found in the detailed description and appended claims. Other aspects will be apparent to persons skilled in the art upon reading and understanding the following detailed description and viewing the drawings that form a part thereof, each of which is not to be taken in a limiting sense. The scope herein is defined by the appended claims and their legal equivalents. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The novel features of this invention, as well as the invention itself, both as to its structure and its operation, will be best understood from the accompanying drawings, taken in conjunction with the accompanying description, in which similar reference characters refer to similar parts, and in which: 
         FIG.  1    is a schematic cross-sectional view of an embodiment of a catheter system in accordance with various embodiments herein, the catheter system including an optical analyzer assembly having features of the present invention; 
         FIG.  2 A  is a simplified schematic view of a portion of an embodiment of the catheter system including an embodiment of the optical analyzer assembly, the optical analyzer assembly being utilized in a first application; 
         FIG.  2 B  is a simplified schematic view of a portion of the catheter system including the optical analyzer assembly of  FIG.  2 A , the optical analyzer assembly being utilized in a second application; 
         FIGS.  3 A- 3 F  are simplified schematic illustrations of operational conditions that may be identified by the optical analyzer assembly during operation of the catheter system of  FIG.  1   ; 
         FIG.  4 A  is a simplified graphical illustration of a representative example of one flash signature that may be identified by the optical analyzer assembly during operation of the catheter system of  FIG.  1   ; 
         FIG.  4 B  is a simplified graphical illustration of a representative example of a second, different flash signature that may be identified by the optical analyzer assembly during operation of the catheter system of  FIG.  1   ; 
         FIG.  5    is a simplified graphical illustration of an example of pulse maximum readings that may be identified by the optical analyzer assembly as pulses of first light energy are sent through a light guide used within the catheter system of  FIG.  1   ; 
         FIG.  6    is a simplified graphical illustration of an example of a number of transitions that may be identified by the optical analyzer assembly within a flash signal generated as pulses of first light energy are sent through a light guide used within the catheter system of  FIG.  1   ; and 
         FIG.  7    is a simplified graphical illustration of an example of how no signal detection conditions can be identified by the optical analyzer assembly as pulses of first light energy are sent through a light guide used within the catheter system of  FIG.  1   . 
     
    
    
     While embodiments of the present invention are susceptible to various modifications and alternative forms, specifics thereof have been shown by way of example and drawings, and are described in detail herein. It is understood, however, that the scope herein is not limited to the particular embodiments described. On the contrary, the intention is to cover modifications, equivalents, and alternatives falling within the spirit and scope herein. 
     DESCRIPTION 
     Treatment of vascular lesions (also sometimes referred to herein as “treatment sites”) can reduce major adverse events or death in affected subjects. As referred to herein, a major adverse event is one that can occur anywhere within the body due to the presence of a vascular lesion. Major adverse events can include, but are not limited to, major adverse cardiac events, major adverse events in the peripheral or central vasculature, major adverse events in the brain, major adverse events in the musculature, or major adverse events in any of the internal organs. 
     As used herein, the terms “intravascular lesion”, “vascular lesion” and “treatment site” are used interchangeably unless otherwise noted. The intravascular lesions and/or the vascular lesions are sometimes referred to herein simply as “lesions”. 
     Those of ordinary skill in the art will realize that the following detailed description of the present invention is illustrative only and is not intended to be in any way limiting. Other embodiments of the present invention will readily suggest themselves to such skilled persons having the benefit of this disclosure. Reference will now be made in detail to implementations of the present invention as illustrated in the accompanying drawings. 
     In the interest of clarity, not all of the routine features of the implementations described herein are shown and described. It will, of course, be appreciated that in the development of any such actual implementation, numerous implementation-specific decisions must be made in order to achieve the developer&#39;s specific goals, such as compliance with application-related and business-related constraints, and that these specific goals will vary from one implementation to another and from one developer to another. Moreover, it is appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking of engineering for those of ordinary skill in the art having the benefit of this disclosure. 
     The catheter systems disclosed herein can include many different forms. Referring now to  FIG.  1   , a schematic cross-sectional view is shown of a catheter system  100  in accordance with various embodiments. The catheter system  100  is suitable for imparting pressure waves to induce fractures in one or more treatment sites within or adjacent a vessel wall of a blood vessel, or on or adjacent to a heart valve, within a body of a patient. In the embodiment illustrated in  FIG.  1   , the catheter system  100  can include one or more of a catheter  102 , a light guide bundle  122  including one or more light guides  122 A, a source manifold  136 , a fluid pump  138 , a system console  123  including one or more of a light source  124 , a power source  125 , a system controller  126 , and a graphic user interface  127  (a “GUI”), a handle assembly  128 , and an optical analyzer assembly  142 . Alternatively, the catheter system  100  can include more components or fewer components than those specifically illustrated and described in relation to  FIG.  1   . 
     It is appreciated that while the catheter system  100  is generally described as including a light guide bundle  122  including one or more light guides  122 A, and a light source  124 , in some alternative embodiments, the catheter system  100  can include an energy guide bundle that includes different types of energy guides, and/or a different type of energy source. 
     In various embodiments, the catheter  102  is configured to move to a treatment site  106  within or adjacent to a vessel wall  108 A of a blood vessel  108  within a body  107  of a patient  109 . The treatment site  106  can include one or more vascular lesions  106 A such as calcified vascular lesions, for example. Additionally, or in the alternative, the treatment site  106  can include vascular lesions  106 A such as fibrous vascular lesions. Still alternatively, in some implementations, the catheter  102  can be used at a treatment site  106  within or adjacent a heart valve within the body  107  of the patient  109 . 
     The catheter  102  can include an inflatable balloon  104  (sometimes referred to herein simply as a “balloon”), a catheter shaft  110  and a guidewire  112 . The balloon  104  can be coupled to the catheter shaft  110 . The balloon  104  can include a balloon proximal end  104 P and a balloon distal end  104 D. The catheter shaft  110  can extend from a proximal portion  114  of the catheter system  100  to a distal portion  116  of the catheter system  100 . The catheter shaft  110  can include a longitudinal axis  144 . The catheter shaft  110  can also include a guidewire lumen  118  which is configured to move over the guidewire  112 . As utilized herein, the guidewire lumen  118  defines a conduit through which the guidewire  112  extends. The catheter shaft  110  can further include an inflation lumen (not shown) and/or various other lumens for various other purposes. In some embodiments, the catheter  102  can have a distal end opening  120  and can accommodate and be tracked over the guidewire  112  as the catheter  102  is moved and positioned at or near the treatment site  106 . In some embodiments, the balloon proximal end  104 P can be coupled to the catheter shaft  110 , and the balloon distal end  104 D can be coupled to the guidewire lumen  118 . 
     The balloon  104  includes a balloon wall  130  that defines a balloon interior  146 . The balloon  104  can be selectively inflated with a balloon fluid  132  to expand from a deflated state suitable for advancing the catheter  102  through a patient&#39;s vasculature, to an inflated state (as shown in  FIG.  1   ) suitable for anchoring the catheter  102  in position relative to the treatment site  106 . Stated in another manner, when the balloon  104  is in the inflated state, the balloon wall  130  of the balloon  104  is configured to be positioned substantially adjacent to the treatment site  106 . It is appreciated that although  FIG.  1    illustrates the balloon wall  130  of the balloon  104  being shown spaced apart from the treatment site  106  of the blood vessel  108  when in the inflated state, this is done merely for ease of illustration. It is recognized that the balloon wall  130  of the balloon  104  will typically be substantially directly adjacent to and/or abutting the treatment site  106  when the balloon  104  is in the inflated state. 
     The balloon  104  suitable for use in the catheter system  100  includes those that can be passed through the vasculature of a patient  109  when in the deflated state. In some embodiments, the balloon  104  is made from silicone. In other embodiments, the balloon  104  can be made from polydimethylsiloxane (PDMS), polyurethane, polymers such as PEBAX™ material, nylon, or any other suitable material. 
     The balloon  104  can have any suitable diameter (in the inflated state). In various embodiments, the balloon  104  can have a diameter (in the inflated state) ranging from less than one millimeter (mm) up to 25 mm. In some embodiments, the balloon  104  can have a diameter (in the inflated state) ranging from at least 1.5 mm up to 14 mm. In some embodiments, the balloons  104  can have a diameter (in the inflated state) ranging from at least two mm up to five mm. 
     In some embodiments, the balloon  104  can have a length ranging from at least three mm to 300 mm. More particularly, in some embodiments, the balloon  104  can have a length ranging from at least eight mm to 200 mm. It is appreciated that a balloon  104  having a relatively longer length can be positioned adjacent to larger treatment sites  106 , and, thus, may be usable for imparting pressure waves onto and inducing fractures in larger vascular lesions  106 A or multiple vascular lesions  106 A at precise locations within the treatment site  106 . It is further appreciated that a longer balloon  104  can also be positioned adjacent to multiple treatment sites  106  at any one given time. 
     The balloon  104  can be inflated to inflation pressures of between approximately one atmosphere (atm) and 70 atm. In some embodiments, the balloon  104  can be inflated to inflation pressures of from at least 20 atm to 60 atm. In other embodiments, the balloon  104  can be inflated to inflation pressures of from at least six atm to 20 atm. In still other embodiments, the balloon  104  can be inflated to inflation pressures of from at least three atm to 20 atm. In yet other embodiments, the balloon  104  can be inflated to inflation pressures of from at least two atm to ten atm. 
     The balloon  104  can have various shapes, including, but not to be limited to, a conical shape, a square shape, a rectangular shape, a spherical shape, a conical/square shape, a conical/spherical shape, an extended spherical shape, an oval shape, a tapered shape, a bone shape, a stepped diameter shape, an offset shape, or a conical offset shape. In some embodiments, the balloon  104  can include a drug eluting coating or a drug eluting stent structure. The drug eluting coating or drug eluting stent can include one or more therapeutic agents including anti-inflammatory agents, anti-neoplastic agents, anti-angiogenic agents, and the like. 
     The balloon fluid  132  can be a liquid or a gas. Some examples of the balloon fluid  132  suitable for use can include, but are not limited to one or more of water, saline, contrast medium, fluorocarbons, perfluorocarbons, gases, such as carbon dioxide, or any other suitable balloon fluid  132 . In some embodiments, the balloon fluid  132  can be used as a base inflation fluid. In some embodiments, the balloon fluid  132  can include a mixture of saline to contrast medium in a volume ratio of approximately 50:50. In other embodiments, the balloon fluid  132  can include a mixture of saline to contrast medium in a volume ratio of approximately 25:75. In still other embodiments, the balloon fluid  132  can include a mixture of saline to contrast medium in a volume ratio of approximately 75:25. However, it is understood that any suitable ratio of saline to contrast medium can be used. The balloon fluid  132  can be tailored on the basis of composition, viscosity, and the like so that the rate of travel of the pressure waves are appropriately manipulated. In certain embodiments, the balloon fluid  132  suitable for use herein is biocompatible. A volume of balloon fluid  132  can be tailored by the chosen light source  124  and the type of balloon fluid  132  used. 
     In some embodiments, the contrast agents used in the contrast media can include, but are not to be limited to, iodine-based contrast agents, such as ionic or non-ionic iodine-based contrast agents. Some non-limiting examples of ionic iodine-based contrast agents include diatrizoate, metrizoate, iothalamate, and ioxaglate. Some non-limiting examples of non-ionic iodine-based contrast agents include iopamidol, iohexol, ioxilan, iopromide, iodixanol, and ioversol. In other embodiments, non-iodine based contrast agents can be used. Suitable non-iodine containing contrast agents can include gadolinium (III)-based contrast agents. Suitable fluorocarbon and perfluorocarbon agents can include, but are not to be limited to, agents such as perfluorocarbon dodecafluoropentane (DDFP, C5F12). 
     The balloon fluids  132  can include those that include absorptive agents that can selectively absorb light in the ultraviolet region (e.g., at least ten nanometers (nm) to 400 nm), the visible region (e.g., at least 400 nm to 780 nm), or the near-infrared region (e.g., at least 780 nm to 2.5 μm) of the electromagnetic spectrum. Suitable absorptive agents can include those with absorption maxima along the spectrum from at least ten nm to 2.5 μm. Alternatively, the balloon fluid  132  can include absorptive agents that can selectively absorb light in the mid-infrared region (e.g., at least 2.5 μm to 15 μm), or the far-infrared region (e.g., at least 15 μm to one mm) of the electromagnetic spectrum. In various embodiments, the absorptive agent can be those that have an absorption maximum matched with the emission maximum of the laser used in the catheter system  100 . By way of non-limiting examples, various lasers described herein can include neodymium:yttrium-aluminum-garnet (Nd:YAG—emission maximum=1064 nm) lasers, holmium:YAG (Ho:YAG—emission maximum=2.1 μm) lasers, or erbium:YAG (Er:YAG—emission maximum=2.94 μm) lasers. In some embodiments, the absorptive agents can be water soluble. In other embodiments, the absorptive agents are not water soluble. In some embodiments, the absorptive agents used in the balloon fluids  132  can be tailored to match the peak emission of the light source  124 . Various light sources  124  having emission wavelengths of at least ten nanometers to one millimeter are discussed elsewhere herein. 
     The catheter shaft  110  of the catheter  102  can be coupled to the one or more light guides  122 A of the light guide bundle  122  that are in optical communication with the light source  124 . The light guide(s)  122 A can be disposed along the catheter shaft  110  and within the balloon  104 . Each of the light guides  122 A can have a guide distal end  122 D that is at any suitable longitudinal position relative to a length of the balloon  104 . In some embodiments, each light guide  122 A can be an optical fiber and the light source  124  can be a laser. The light source  124  can be in optical communication with the light guides  122 A at the proximal portion  114  of the catheter system  100 . More particularly, the light source  124  can selectively, simultaneously, sequentially and/or alternatively be in optical communication with each of the light guides  122 A in any desired combination, order and/or pattern. 
     In some embodiments, the catheter shaft  110  can be coupled to multiple light guides  122 A such as a first light guide, a second light guide, a third light guide, etc., which can be disposed at any suitable positions about the guidewire lumen  118  and/or the catheter shaft  110 . For example, in certain non-exclusive embodiments, two light guides  122 A can be spaced apart by approximately 180 degrees about the circumference of the guidewire lumen  118  and/or the catheter shaft  110 ; three light guides  122 A can be spaced apart by approximately 120 degrees about the circumference of the guidewire lumen  118  and/or the catheter shaft  110 ; or four light guides  122 A can be spaced apart by approximately 90 degrees about the circumference of the guidewire lumen  118  and/or the catheter shaft  110 . Still alternatively, multiple light guides  122 A need not be uniformly spaced apart from one another about the circumference of the guidewire lumen  118  and/or the catheter shaft  110 . More particularly, the light guides  122 A can be disposed either uniformly or non-uniformly about the guidewire lumen  118  and/or the catheter shaft  110  to achieve the desired effect in the desired locations. 
     The catheter system  100  and/or the light guide bundle  122  can include any number of light guides  122 A in optical communication with the light source  124  at the proximal portion  114 , and with the balloon fluid  132  within the balloon interior  146  of the balloon  104  at the distal portion  116 . For example, in some embodiments, the catheter system  100  and/or the light guide bundle  122  can include from one light guide  122 A to five light guides  122 A. In other embodiments, the catheter system  100  and/or the light guide bundle  122  can include from five light guides  122 A to fifteen light guides  122 A. In yet other embodiments, the catheter system  100  and/or the light guide bundle  122  can include from ten light guides  122 A to thirty light guides  122 A. Alternatively, in still other embodiments, the catheter system  100  and/or the light guide bundle  122  can include greater than 30 light guides  122 A. 
     The light guides  122 A can have any suitable design for purposes of generating plasma and/or pressure waves in the balloon fluid  132  within the balloon interior  146 . In certain embodiments, the light guides  122 A can include an optical fiber or flexible light pipe. The light guides  122 A can be thin and flexible and can allow light signals to be sent with very little loss of strength. The light guides  122 A can include a core surrounded by a cladding about its circumference. In some embodiments, the core can be a cylindrical core or a partially cylindrical core. The core and cladding of the light guides  122 A can be formed from one or more materials, including but not limited to one or more types of glass, silica, or one or more polymers. The light guides  122 A may also include a protective coating, such as a polymer. It is appreciated that the index of refraction of the core will be greater than the index of refraction of the cladding. 
     Each light guide  122 A can guide first light energy along its length from a guide proximal end  122 P toward the guide distal end  122 D having at least one optical window (not shown) that is positioned within the balloon interior  146 . 
     In various embodiments, the guide distal end  122 D can further include and/or incorporate a distal light receiver  122 R that enables second light energy to be moved back into and through the light guide  122 A from the guide distal end  122 D to the guide proximal end  122 P. Stated another way, the first light energy can move in a first direction  121 F along the light guide  122 A that is generally from the guide proximal end  122 P toward the guide distal end  122 D of the light guide  122 A. The second light energy, which in certain situations can comprise at least a portion of the first light energy, can move in a second direction  121 S along the light guide  122 A that is substantially opposite the first direction  121 F, i.e. from the guide distal end  122 D toward the guide proximal end  122 P of the light guide  122 A. Moreover, as described in greater detail herein below, the second light energy emitted from the guide proximal end  122 P after being moved back through the light guide  122 A (in the second direction  121 S) can be separated and then optically detected, interrogated and/or analyzed through use of the optical analyzer assembly  142  in order to determine accurate operational modes, with both non-fault conditions and fault conditions, of the light guides  122 A. 
     The light guides  122 A can assume many configurations about and/or relative to the catheter shaft  110  of the catheter  102 . In some embodiments, the light guides  122 A can run parallel to the longitudinal axis  144  of the catheter shaft  110 . In some embodiments, the light guides  122 A can be physically coupled to the catheter shaft  110 . In other embodiments, the light guides  122 A can be disposed along a length of an outer diameter of the catheter shaft  110 . In yet other embodiments, the light guides  122 A can be disposed within one or more light guide lumens within the catheter shaft  110 . 
     The light guides  122 A can also be disposed at any suitable positions about the circumference of the guidewire lumen  118  and/or the catheter shaft  110 , and the guide distal end  122 D of each of the light guides  122 A can be disposed at any suitable longitudinal position relative to the length of the balloon  104  and/or relative to the length of the guidewire lumen  118  to more effectively and precisely impart pressure waves for purposes of disrupting the vascular lesions  106 A at the treatment site  106 . 
     In certain embodiments, the light guides  122 A can include one or more photoacoustic transducers  154 , where each photoacoustic transducer  154  can be in optical communication with the light guide  122 A within which it is disposed. In some embodiments, the photoacoustic transducers  154  can be in optical communication with the guide distal end  122 D of the light guide  122 A. The photoacoustic transducers  154  can have a shape that corresponds with and/or conforms to the guide distal end  122 D of the light guide  122 A. 
     The photoacoustic transducer  154  is configured to convert first light energy into an acoustic wave at or near the guide distal end  122 D of the light guide  122 A. The direction of the acoustic wave can be tailored by changing an angle of the guide distal end  122 D of the light guide  122 A. 
     In certain embodiments, the photoacoustic transducers  154  disposed at the guide distal end  122 D of the light guide  122 A can assume the same shape as the guide distal end  122 D of the light guide  122 A. For example, in certain non-exclusive embodiments, the photoacoustic transducer  154  and/or the guide distal end  122 D can have a conical shape, a convex shape, a concave shape, a bulbous shape, a square shape, a stepped shape, a half-circle shape, an ovoid shape, and the like. The light guide  122 A can further include additional photoacoustic transducers  154  disposed along one or more side surfaces of the length of the light guide  122 A. 
     In some embodiments, the light guides  122 A can further include one or more diverting features or “diverters” (not shown in  FIG.  1   ) within the light guide  122 A that are configured to direct light to exit the light guide  122 A toward a side surface which can be located at or near the guide distal end  122 D of the light guide  122 A, and toward the balloon wall  130 . A diverting feature can include any feature of the system that diverts first light energy from the light guide  122 A away from its axial path toward a side surface of the light guide  122 A. The light guides  122 A can each include one or more light windows disposed along the longitudinal or circumferential surfaces of each light guide  122 A and in optical communication with a diverting feature. Stated in another manner, the diverting features can be configured to direct first light energy in the light guide  122 A toward a side surface that is at or near the guide distal end  122 D, where the side surface is in optical communication with a light window. The light windows can include a portion of the light guide  122 A that allows first light energy to exit the light guide  122 A from within the light guide  122 A, such as a portion of the light guide  122 A lacking a cladding material on or about the light guide  122 A. 
     Examples of the diverting features suitable for use include a reflecting element, a refracting element, and a fiber diffuser. The diverting features suitable for focusing first light energy away from the tip of the light guides  122 A can include, but are not to be limited to, those having a convex surface, a gradient-index (GRIN) lens, and a mirror focus lens. Upon contact with the diverting feature, the first light energy is diverted within the light guide  122 A to one or more of a plasma generator  133  and the photoacoustic transducer  154  that is in optical communication with a side surface of the light guide  122 A. As noted, the photoacoustic transducer  154  then converts first light energy into an acoustic wave that extends away from the side surface of the light guide  122 A. 
     The source manifold  136  can be positioned at or near the proximal portion  114  of the catheter system  100 . The source manifold  136  can include one or more proximal end openings that can receive the one or more light guides  122 A of the light guide bundle  122 , the guidewire  112 , and/or an inflation conduit  140  that is coupled in fluid communication with the fluid pump  138 . The catheter system  100  can also include the fluid pump  138  that is configured to inflate the balloon  104  with the balloon fluid  132  as needed. 
     As noted above, in the embodiment illustrated in  FIG.  1   , the system console  123  includes one or more of the light source  124 , the power source  125 , the system controller  126 , and the GUI  127 . Alternatively, the system console  123  can include more components or fewer components than those specifically illustrated in  FIG.  1   . For example, in certain non-exclusive alternative embodiments, the system console  123  can be designed without the GUI  127 . Still alternatively, one or more of the light source  124 , the power source  125 , the system controller  126 , and the GUI  127  can be provided within the catheter system  100  without the specific need for the system console  123 . 
     As illustrated in  FIG.  1   , in certain embodiments, at least a portion of the optical analyzer assembly  142  can also be positioned substantially within the system console  123 . Alternatively, components of the optical analyzer assembly  142  can be positioned in a different manner than what is specifically shown in  FIG.  1   . 
     As shown, the system console  123 , and the components included therewith, is operatively coupled to the catheter  102 , the light guide bundle  122 , and the remainder of the catheter system  100 . For example, in some embodiments, as illustrated in  FIG.  1   , the system console  123  can include a console connection aperture  148  (also sometimes referred to generally as a “socket”) by which the light guide bundle  122  is mechanically coupled to the system console  123 . In such embodiments, the light guide bundle  122  can include a guide coupling housing  150  (also sometimes referred to generally as a “ferrule”) that houses a portion, such as the guide proximal end  122 P, of each of the light guides  122 A. The guide coupling housing  150  is configured to fit and be selectively retained within the console connection aperture  148  to provide the mechanical coupling between the light guide bundle  122  and the system console  123 . 
     The light guide bundle  122  can also include a guide bundler  152  (or “shell”) that brings each of the individual light guides  122 A closer together so that the light guides  122 A and/or the light guide bundle  122  can be in a more compact form as it extends with the catheter  102  into the blood vessel  108  during use of the catheter system  100 . 
     The light source  124  can be selectively and/or alternatively coupled in optical communication with each of the light guides  122 A, such as to the guide proximal end  122 P of each of the light guides  122 A, in the light guide bundle  122 . In particular, the light source  124  is configured to generate first light energy in the form of a source beam  124 A, such as a pulsed source beam, that can be selectively and/or alternatively directed to and received by each of the light guides  122 A in the light guide bundle  122  as an individual guide beam  124 B. Alternatively, the catheter system  100  can include more than one light source  124 . For example, in one non-exclusive alternative embodiment, the catheter system  100  can include a separate light source  124  for each of the light guides  122 A in the light guide bundle  122 . 
     The light source  124  can have any suitable design. In certain embodiments, the light source  124  can be configured to provide sub-millisecond pulses of first light energy from the light source  124  that are focused onto a small spot in order to couple it into the guide proximal end  122 P of the light guide  122 A. Such pulses of first light energy are then directed and/or guided along the light guides  122 A to a location within the balloon interior  146  of the balloon  104 , thereby inducing plasma formation (also sometimes referred to herein as a “plasma flash”) in the balloon fluid  132  within the balloon interior  146  of the balloon  104 , such as via the plasma generator  133  that can be located at or near the guide distal end  122 D of the light guide  122 A. In particular, the light emitted at the guide distal end  122 D of the light guide  122 A is directed toward and energizes the plasma generator  133  to form the plasma within the balloon fluid  132  within the balloon interior  146 . The plasma formation causes rapid bubble formation, and imparts pressure waves upon the treatment site  106 . An exemplary plasma-induced bubble  134  is illustrated in  FIG.  1   . 
     When the plasma initially forms in the balloon fluid  132  within the balloon interior  146 , it emits broad-spectrum electromagnetic radiation. This can be seen as a flash of broad spectrum light detectable by the naked eye. A portion of the light emitted from the plasma bubble  134 , in the form of the second light energy, can be coupled into the distal light receiver  122 R at the guide distal end  122 D of the light guide  122 A and travel back to the guide proximal end  122 P where it can be separated, detected and analyzed through use of the optical analyzer assembly  142 . The intensity and timing of the visible light pulse relative to the plasma generating pulse provides an indication that the plasma generator  133  functioned, its energy output and its functional or operational condition. Visible light flashes may occur in other locations of the light guide  122 A if the light guide  122 A is damaged or broken. Such other visible light flashes will also be coupled into the light guide  122 A and carried back to the guide proximal end  122 P. The intensity and timing of these other light pulses provide an indication of damage to or failure of the light guide  122 A or the plasma generator  133 . In such situations, the optical analyzer assembly  142  can include a safety shutdown system  283  (illustrated in  FIG.  2 A ) that can be selectively activated to shut down operation of the catheter system  100 . 
     In various implementations of the optical analyzer assembly  142 , the optical analyzer assembly  142  can be configured to detect certain functional or operational conditions of the light guide  122 A and/or the plasma generator  133 , as are further illustrated in  FIGS.  3 A- 3 F , such as (i) normal operation conditions; (ii) intermittent gas bubble production conditions; (iii) guide distal end plasma initiation conditions; (iv) housing/target failure conditions; (v) broken light guide (fiber) conditions, such as from broken light guides at the guide distal end; and (vi) chewback conditions, such as from broken light guides along the light guide and at least somewhat spaced apart from the guide distal end. It is appreciated that some identified operation conditions, including normal operation conditions, intermittent gas bubble production conditions, and guide distal end plasma initiation conditions, although they may require further monitoring of the condition of the light guide  122 A and/or the plasma generator  133 , do not require immediate stopping of operation of the catheter system  100  or replacement of the light guide  122 A and/or the plasma generator  133 . However, it is further appreciated that other identified operation conditions, such as housing/target failure conditions, broken light guide (fiber) conditions, and chewback conditions, may and often do require stopping of operation of the catheter system  100  and replacement of the light guide  122 A and/or the plasma generator  133 . 
     The configuration of the plasma generator  133  and/or the distal light receiver  122 R further allows ambient light that originates outside of the catheter  102  to be coupled into the guide distal end  122 D of the light guide  122 A. In one implementation, the optical analyzer assembly  142  monitors for returned ambient light energy that traverses the light guide  122 A from the guide distal end  122 D to the guide proximal end  122 P. If any ambient light energy is present and detected by the optical analyzer assembly  142  in such situations, this is an indication that the catheter  102  is located outside of the body  107  of the patient  109 , and the optical analyzer assembly  142  can be configured to lock out the light source  124  accordingly. In particular, in such situations, the safety shutdown system  283  of the optical analyzer assembly  142  can be selectively activated to shut down operation of the catheter system  100 . 
     In various non-exclusive alternative embodiments, the sub-millisecond pulses of first light energy from the light source  124  can be delivered to the treatment site  106  at a frequency of between approximately one hertz (Hz) and 5000 Hz, between approximately 30 Hz and 1000 Hz, between approximately ten Hz and 100 Hz, or between approximately one Hz and 30 Hz. Alternatively, the sub-millisecond pulses of first light energy can be delivered to the treatment site  106  at a frequency that can be greater than 5000 Hz or less than one Hz, or any other suitable range of frequencies. 
     It is appreciated that although the light source  124  is typically utilized to provide pulses of first light energy, the light source  124  can still be described as providing a single source beam  124 A, i.e. a single pulsed source beam. 
     The light sources  124  suitable for use can include various types of light sources including lasers and lamps. For example, in certain non-exclusive embodiments, the light source  124  can be an infrared laser that emits first light energy in the form of pulses of infrared light. Alternatively, as noted above, the light sources  124 , as referred to herein, can include any suitable type of energy source. 
     Suitable lasers can include short pulse lasers on the sub-millisecond timescale. In some embodiments, the light source  124  can include lasers on the nanosecond (ns) timescale. The lasers can also include short pulse lasers on the picosecond (ps), femtosecond (fs), and microsecond (us) timescales. It is appreciated that there are many combinations of laser wavelengths, pulse widths and energy levels that can be employed to achieve plasma in the balloon fluid  132  of the catheter  102 . In various non-exclusive alternative embodiments, the pulse widths can include those falling within a range including from at least ten ns to 3000 ns, at least 20 ns to 100 ns, or at least one ns to 500 ns. Alternatively, any other suitable pulse width range can be used. 
     Exemplary nanosecond lasers can include those within the UV to IR spectrum, spanning wavelengths of about ten nanometers (nm) to one millimeter (mm). In some embodiments, the light sources  124  suitable for use in the catheter system  100  can include those capable of producing light at wavelengths of from at least 750 nm to 2000 nm. In other embodiments, the light sources  124  can include those capable of producing light at wavelengths of from at least 700 nm to 3000 nm. In still other embodiments, the light sources  124  can include those capable of producing light at wavelengths of from at least 100 nm to ten micrometers (μm). Nanosecond lasers can include those having repetition rates of up to 200 kHz. In some embodiments, the laser can include a Q-switched thulium:yttrium-aluminum-garnet (Tm:YAG) laser. In other embodiments, the laser can include a neodymium:yttrium-aluminum-garnet (Nd:YAG) laser, holmium:yttrium-aluminum-garnet (Ho:YAG) laser, erbium:yttrium-aluminum-garnet (Er:YAG) laser, excimer laser, helium-neon laser, carbon dioxide laser, as well as doped, pulsed, fiber lasers. 
     The catheter system  100  can generate pressure waves having maximum pressures in the range of at least one megapascal (MPa) to 100 MPa. The maximum pressure generated by a particular catheter system  100  will depend on the light source  124 , the absorbing material, the bubble expansion, the propagation medium, the balloon material, and other factors. In various non-exclusive alternative embodiments, the catheter system  100  can generate pressure waves having maximum pressures in the range of at least approximately two MPa to 50 MPa, at least approximately two MPa to 30 MPa, or at least approximately 15 MPa to 25 MPa. 
     The pressure waves can be imparted upon the treatment site  106  from a distance within a range from at least approximately 0.1 millimeters (mm) to greater than approximately 25 mm extending radially from the light guides  122 A when the catheter  102  is placed at the treatment site  106 . In various non-exclusive alternative embodiments, the pressure waves can be imparted upon the treatment site  106  from a distance within a range from at least approximately ten mm to 20 mm, at least approximately one mm to ten mm, at least approximately 1.5 mm to four mm, or at least approximately 0.1 mm to ten mm extending radially from the light guides  122 A when the catheter  102  is placed at the treatment site  106 . In other embodiments, the pressure waves can be imparted upon the treatment site  106  from another suitable distance that is different than the foregoing ranges. In some embodiments, the pressure waves can be imparted upon the treatment site  106  within a range of at least approximately two MPa to 30 MPa at a distance from at least approximately 0.1 mm to ten mm. In some embodiments, the pressure waves can be imparted upon the treatment site  106  from a range of at least approximately two MPa to 25 MPa at a distance from at least approximately 0.1 mm to ten mm. Still alternatively, other suitable pressure ranges and distances can be used. 
     The power source  125  is electrically coupled to and is configured to provide necessary power to each of the light source  124 , the system controller  126 , the GUI  127 , the handle assembly  128 , and the optical analyzer assembly  142 . The power source  125  can have any suitable design for such purposes. 
     The system controller  126  is electrically coupled to and receives power from the power source  125 . The system controller  126  is coupled to and is configured to control operation of each of the light source  124 , the GUI  127  and the optical analyzer assembly  142 . The system controller  126  can include one or more processors or circuits for purposes of controlling the operation of at least the light source  124 , the GUI  127  and the optical analyzer assembly  142 . For example, the system controller  126  can control the light source  124  for generating pulses of first light energy as desired and/or at any desired firing rate. The system controller  126  can control and/or operate in conjunction with the optical analyzer assembly  142  to effectively provide real-time continuous monitoring of the performance, reliability, safety and proper usage of the catheter system  100 . 
     The system controller  126  can further be configured to control operation of other components of the catheter system  100  such as the positioning of the catheter  102  adjacent to the treatment site  106 , the inflation of the balloon  104  with the balloon fluid  132 , etc. Further, or in the alternative, the catheter system  100  can include one or more additional controllers that can be positioned in any suitable manner for purposes of controlling the various operations of the catheter system  100 . For example, in certain embodiments, an additional controller and/or a portion of the system controller  126  can be positioned and/or incorporated within the handle assembly  128 . 
     The GUI  127  is accessible by the user or operator of the catheter system  100 . The GUI  127  is electrically connected to the system controller  126 . With such design, the GUI  127  can be used by the user or operator to ensure that the catheter system  100  is effectively utilized to impart pressure onto and induce fractures at the treatment site(s)  106 . The GUI  127  can provide the user or operator with information that can be used before, during and after use of the catheter system  100 . In one embodiment, the GUI  127  can provide static visual data and/or information to the user or operator. In addition, or in the alternative, the GUI  127  can provide dynamic visual data and/or information to the user or operator, such as video data or any other data that changes over time during use of the catheter system  100 . In various embodiments, the GUI  127  can include one or more colors, different sizes, varying brightness, etc., that may act as alerts to the user or operator. Additionally, or in the alternative, the GUI  127  can provide audio data or information to the user or operator. The specifics of the GUI  127  can vary depending upon the design requirements of the catheter system  100 , or the specific needs, specifications and/or desires of the user or operator. 
     As shown in  FIG.  1   , the handle assembly  128  can be positioned at or near the proximal portion  114  of the catheter system  100 , and/or near the source manifold  136 . In this embodiment, the handle assembly  128  is coupled to the balloon  104  and is positioned spaced apart from the balloon  104 . Alternatively, the handle assembly  128  can be positioned at another suitable location. 
     The handle assembly  128  is handled and used by the user or operator to operate, position and control the catheter  102 . The design and specific features of the handle assembly  128  can vary to suit the design requirements of the catheter system  100 . In the embodiment illustrated in  FIG.  1   , the handle assembly  128  is separate from, but in electrical and/or fluid communication with one or more of the system controller  126 , the light source  124 , the fluid pump  138 , the GUI  127  and the optical analyzer assembly  142 . In some embodiments, the handle assembly  128  can integrate and/or include at least a portion of the system controller  126  within an interior of the handle assembly  128 . For example, as shown, in certain such embodiments, the handle assembly  128  can include circuitry  156  that can form at least a portion of the system controller  126 . In some embodiments, the circuitry  156  can receive electrical signals or data from the optical analyzer assembly  142 . Further, or in the alternative, the circuitry  156  can transmit such electrical signals or otherwise provide data to the system controller  126 . 
     In one embodiment, the circuitry  156  can include a printed circuit board having one or more integrated circuits, or any other suitable circuitry. In an alternative embodiment, the circuitry  156  can be omitted, or can be included within the system controller  126 , which in various embodiments can be positioned outside of the handle assembly  128 , such as within the system console  123 . It is understood that the handle assembly  128  can include fewer or additional components than those specifically illustrated and described herein. 
     As an overview, and as provided in greater detail herein, the optical analyzer assembly  142  is configured to effectively monitor the performance, reliability, safety and proper usage of the catheter system  100 . During use of the catheter system  100 , when the plasma initially forms in the balloon fluid  132  within the balloon interior  146 , as a result of a pulse of the first light energy being directed into the balloon fluid  132  within the balloon interior  146 , the plasma flash emits broad-spectrum electromagnetic radiation. The plasma flash can be effectively captured in the form of a flash signature (or flash signal) that can include summary parameters such as a pulse maximum value, rise time, width, and start time relative to a reference, as well as including a measure of signal volatility (described as a number of transitions), all of which can provide indications of the condition of the light guide  122 A and/or the plasma generator  133 . 
     At least a portion of the first light energy emitted can reflect off of, or otherwise be received by, the distal light receiver  122 R near the guide distal end  122 D of the light guide  122 A. Such portion of the first light energy can thus travel back through the light guide  122 A as second light energy that moves in the second direction  121 S to the guide proximal end  122 P where it can be separated, detected and analyzed through use of the optical analyzer assembly  142 . The intensity and timing of the visible light pulse relative to the plasma-generating pulse from the light source  124  provides an indication that the plasma generator  133  functioned, its energy output, and its functional condition. It is appreciated that visible light flashes may occur in other locations along the length of the light guide  122 A if the light guide  122 A is damaged or broken. Such additional light flashes will also be coupled into the light guide  122 A and carried back in the second direction  121 S to the guide proximal end  122 P. The intensity and timing of these additional light pulses can indicate a damaged light guide  122 A or plasma generator  133 . 
     By evaluating and/or analyzing the intensity and timing of the visible light pulse relative to the plasma-generating pulse from the light source  124 , the optical analyzer assembly  142  is able to identify operational conditions of the light guide  122 A and/or the plasma generator  133  such as (i) normal operation conditions, where plasma is generated substantially directly adjacent to the plasma generator  133  when the first light energy is directed from the guide distal end  122 D of the light guide  122 A toward the plasma generator  133  and thus impinges on a target surface of the plasma generator  133 ; (ii) intermittent gas bubble production conditions, where gas bubbles formed within the balloon fluid  132  are found between the guide distal end  122 D of the light guide  122 A and the plasma generator  133  that optically impact the directing of the first light energy toward the target surface of the plasma generator  133 ; (iii) guide distal end plasma initiation conditions, where there may be some debris substantially adjacent to the guide distal end  122 D of the light guide  122 A which causes plasma to be generated at such point substantially adjacent to the guide distal end  122 D of the light guide  122 A rather than substantially directly adjacent to the plasma generator  133 ; (iv) housing/target failure conditions, where there is a failure to generate the desired plasma flash in the balloon fluid  132  within the balloon interior  146  due to issues or problems with the light guide  122 A and/or the plasma generator  133 ; (v) broken light guide (fiber) conditions, such as broken light guides  122 A at the guide distal end  122 D, where little or no plasma is generated in the balloon fluid  132  within the balloon interior  146 , and any minimal plasma that may be generated has a lower pulse maximum value due to the first light energy being directed in multiple disparate directions away from the guide distal end  122 D of the light guide  122 A rather than just directly toward the plasma generator  133 ; and (vi) chewback conditions, such as broken light guides  122 A along the length of the light guide  122 A and at least somewhat spaced apart from the guide distal end  122 D, where plasma generation can occur in the balloon fluid  132  within the balloon interior  146  substantially adjacent to where a break may exist along the length of the light guide  122 A. It is appreciated that some of these identified operation conditions, including normal operation conditions, intermittent gas bubble production conditions, and guide distal end plasma initiation conditions, although they may require further monitoring of the condition of the light guide  122 A and/or the plasma generator  133 , do not require immediate stopping of operation of the catheter system  100  or replacement of the light guide  122 A and/or the plasma generator  133 . However, it is further appreciated that other identified operation conditions, such as housing/target failure conditions, broken light guide (fiber) conditions, and chewback conditions, may and often do require stopping of operation of the catheter system  100  and replacement of the light guide  122 A and/or the plasma generator  133 . 
     It is appreciated that the misuse or failure of an energy-driven plasma generator  133  or associated light guide  122 A, such as if the light guide  122 A and/or the catheter system  100  is used outside the body  107  of the patient  109  and/or if the light guide  122 A breaks or is damaged during the use of the catheter system  100 , could lead to patient or operator harm resulting from the leaked energy. Potential harms include tissue burns and retinal damage. As noted above, in some embodiments, the light source  124  is a laser that emits invisible infrared light, making visible detection by the operator impossible. Thus, if the optical analyzer assembly  142  indicates any such misuse or failures to have occurred, the procedure and energy delivery, such as laser energy delivery, must be stopped immediately to mitigate the associated risks to the patient and the operator. Stated in another manner, with the design of the optical analyzer assembly  142  described herein, the present invention detects any noted misuses or failures within the catheter system  100 , such as misuse of the catheter system  100  and/or breaking of, damage to, or failure of the light guide  122 A and/or the plasma generator  133 , and provides an indicator or signal that the system controller  126  can use to lock out the light source  124 . In certain embodiments, the locking out of the light source  124  can be accomplished through use of the safety shutdown system  283 , which in some such embodiments can include one or more of a safety interlock  284  (illustrated in  FIG.  2 A ) and a shutter  286  (illustrated in  FIG.  2 A ), that can be incorporated as part of the optical analyzer assembly  142 . This provides a necessary safety interlock and mitigation for a potentially hazardous condition in which the light source  124  can leak out of any part of the catheter system  100  or light guide  122 A due to misuse or failure. Moreover, the system controller  126  could be used to indicate to the surgeon, such as via the GUI  127 , to halt the procedure and remove the catheter  102  from the patient  109  under treatment. A simple example of potential misuse would be attempting to energize the catheter system  100  when it is outside of the body  107  of the patient  109  and/or away from the intended treatment site  106 . The emitted energy could unintentionally be viewed by the operator resulting in retinal damage. 
     It is further appreciated that the optical analyzer assembly  142  can have any suitable design for purposes of effectively monitoring the safety, performance, reliability and proper usage of the catheter system  100 . Certain non-exclusive examples of potential designs and applications for the optical analyzer assembly  142  are described in detail herein below. 
       FIG.  2 A  is a simplified schematic view of a portion of an embodiment of the catheter system  200  including an embodiment of the optical analyzer assembly  242 . As shown in  FIG.  2 A , the optical analyzer assembly  242  is being utilized in a first application.  FIG.  2 B  is a simplified schematic view of a portion of the catheter system  200  including the optical analyzer assembly  242  of  FIG.  2 A . As shown in  FIG.  2 B , the optical analyzer assembly  242  is being utilized in a second application. 
     The design of the catheter system  200  is substantially similar to the embodiments illustrated and described herein above. It is appreciated that various components of the catheter system  200 , such as are shown in  FIG.  1   , are not illustrated in  FIGS.  2 A and  2 B  for purposes of clarity and ease of illustration. However, it is appreciated that the catheter system  200  will likely include most, if not all, of such components. 
     As shown in  FIGS.  2 A and  2 B , the catheter system  200  again includes a light source  224  that is configured to generate first light energy in the form of a source beam  224 A, such as a pulsed source beam, that can be selectively and/or alternatively directed to and received by each light guide  222 A (only one light guide is illustrated in  FIGS.  2 A and  2 B ) as an individual guide beam  224 B (illustrated in  FIG.  2 A ). In one non-exclusive embodiment, the light source  224  is an infrared laser source, and the light guide  222 A is a small diameter, multimode optical fiber. In the embodiment illustrated in  FIGS.  2 A and  2 B , a pulse generator  260  is coupled to the light source  224 . The pulse generator  260  is configured to trigger the light source  224 , which, thus, emits an energy pulse as the source beam  224 A. 
     In certain embodiments, as shown in  FIG.  2 A , the source beam  224 A from the light source  224  passes through a first optical element  262 , such as a coupling and/or focusing lens, that is configured to focus the source beam  224 A as the individual guide beam  224 B down onto a guide proximal end  222 P of the light guide  222 A, thereby coupling the individual guide beam  224 B in the form of the pulse of infrared energy (the first light energy) into the light guide  222 A. Subsequently, the individual guide beam  224 B travels along and/or through the light guide  222 A as the first light energy and energizes a plasma generator  233  that is positioned and/or incorporated at or near a guide distal end  222 D of the light guide  222 A. The plasma generator  233  utilizes the pulse of infrared energy to create a localized plasma  234  (such as in the form of a plasma bubble or plasma flash) in the balloon fluid  132  (illustrated in  FIG.  1   ) within the balloon interior  146  (illustrated in  FIG.  1   ) of the balloon  104  (illustrated in  FIG.  1   ). 
     As shown in  FIG.  2 A , upon creation of the plasma  234  in the balloon fluid  132  within the balloon interior  146 , in various embodiments, a pulse of broad-spectrum light energy emitted from the plasma flash  234  in the form of second light energy is coupled back into the guide distal end  222 D of the light guide  222 A via a distal light receiver  222 R. Such pulse of broad-spectrum light energy (second light energy) then travels back along and/or through the light guide  222 A from where it is emitted from the guide proximal end  222 P of the light guide  222 A as the second light energy  224 C. 
     Additionally, or in the alternative, as shown in  FIG.  2 B , in some applications, ambient light  235  near the guide distal end  222 D of the light guide  222 A can be coupled into the guide distal end  222 D of the light guide  222 A via the distal light receiver  222 R. Such ambient light energy (second light energy) then travels along and through the light guide  222 A toward the guide proximal end  222 P of the light guide  222 A, from where it is emitted as the second light energy  224 C (also sometimes referred to as an “ambient energy beam” in this application). 
     As described in detail herein, the optical analyzer assembly  242  is configured to effectively monitor the performance, reliability, safety and proper usage of the catheter system  200  by optically analyzing the second light energy emitted from the guide proximal end  222 P of the light guide  222 A. Stated in another manner, the optical analyzer assembly  242  is configured to effectively monitor the performance, reliability, safety and proper usage of the catheter system  200  by optically analyzing (i) the second light energy  224 C that is generated as a result of the plasma flash  234  created by the plasma generator  233  in the balloon fluid  132  within the balloon interior  146  of the balloon  104 , and/or (ii) the second light energy  224 C that is in the form of an ambient energy beam  235  that is coupled into the guide distal end  222 D of the light guide  222 A via the distal light receiver  222 R. 
     The design of the optical analyzer assembly  242  can be varied to suit the specific requirements of the catheter system  200 . In particular, in the embodiment shown in  FIGS.  2 A and  2 B , the optical analyzer assembly  242  includes one or more of a first beamsplitter  264 , the first optical element  262 , a second optical element  266 , such as an imaging lens in one non-exclusive embodiment, a second beamsplitter  268 , a first filter  270 , a photodetector  272 , an amplifier  274 , control electronics  276 , which can include one or more processors or circuits, a second filter  278 , an imaging device  280 , such as a camera or other suitable imaging device, a device controller  282 , and a safety shutdown system  283 . As shown, the safety shutdown system  283  can include one or more of a safety interlock  284  and a shutter  286 . Alternatively, in other embodiments, the optical analyzer assembly  242  and/or the safety shutdown system  283  can include more components or fewer components than what is specifically illustrated and described herein. Still alternatively, in still other embodiments, the various components of the optical analyzer assembly  242  can be positioned in a different manner than what is specifically illustrated in  FIGS.  2 A and  2 B . 
     As illustrated in the first application shown in  FIG.  2 A , the first beamsplitter  264 , such as a dichroic beamsplitter in one embodiment, is positioned in the optical path of the source beam  224 A between the light source  224  and the guide proximal end  222 P of the light guide  222 A. In certain embodiments, the beamsplitter  264  is configured to pass light for wavelengths longer than those visible to the photodetector  272  to provide the individual guide beam  224 B that is directed toward the guide proximal end  222 P of the light guide  222 A. Such threshold wavelength can be referred to as the cutoff wavelength. The beamsplitter  264  is further configured to reflect all light having a wavelength that is shorter than the cutoff wavelength. As illustrated in this embodiment, the first optical element  262  is positioned between the first beamsplitter  264  and the light guide  222 A and is configured to focus the individual guide beam  224 B down onto the guide proximal end  222 P of the light guide  222 A, thereby coupling the individual guide beam  224 B into the light guide  222 A. 
     The first light energy of the individual guide beam  224 B is guided along the light guide  222 A from the guide proximal end  222 P to the guide distal end  222 D and energizes the plasma generator  233  that is positioned and/or incorporated at or near a guide distal end  222 D of the light guide  222 A. The plasma generator  233  utilizes the pulse of infrared energy to create a localized plasma  234  in the balloon fluid  132  within the balloon interior  146  of the balloon  104 . A pulse of broad-spectrum light energy emitted from the plasma flash  234  as the form of the second light energy is then coupled back into the guide distal end  222 D of the light guide  222 A, and travels back along and/or through the light guide  222 A from where it is emitted from the guide proximal end  222 P of the light guide  222 A as the second light energy  224 C. 
     As illustrated in  FIG.  2 A , the second light energy  224 C emitted from the guide proximal end  222 P of the light guide  222 A is collimated by the first optical element  262  before being directed back toward the first beamsplitter  264 . At least a portion of the second light energy  224 C is then redirected and/or reflected by the first beamsplitter  264  toward the second beamsplitter  268 . The second optical element  266  is positioned in the optical path of the redirected portion of the second light energy  224 C between the first beamsplitter  264  and the second beamsplitter  268 . The optics of the second optical element  266  focus the collimated second light energy  224 C toward the second beamsplitter  268 . The second beamsplitter  268  then redirects and/or reflects a portion of the collimated second light energy  224 C through the first filter  270 , such as a bandpass filter in certain embodiments, and onto the photodetector  272 , thus forming an image of the guide proximal end  222 P of the light guide  222 A onto the photodetector  272 , and thereby coupling the second light energy  224 C emitted from the guide proximal end  222 P of the light guide  222 A onto the photodetector  272 . In certain embodiments, the photodetector  272  can be a photodiode or another suitable type of photodetector. With such design, the visible light emitted from the plasma flash  234  formed at the guide distal end  222 D of the light guide  222 A is collected by the photodetector  272 . 
     In some embodiments, the photodetector  272  generates a signal that is based on the visible light emitted from the plasma formed at the guide distal end  222 D of the light guide  222 A that has been collected by the photodetector  272 . As shown in  FIG.  2 A , the signal from the photodetector  272  is then directed to the amplifier  274  and the control electronics  276 , where detection of and intensity evaluation of the plasma flash  234  are determined. In particular, in certain embodiments, the signal from the photodetector  272  is directed toward the amplifier  274  where the signal from the photodetector  272  is amplified. The amplified signal is thus utilized within the control electronics  276  to determine the intensity of the plasma flash  234  that occurred in the balloon fluid  132  within the balloon interior  146 . 
     In certain embodiments, the pulse from the amplified photodetector signal can be gated using a discriminator (not shown), such as a discriminator circuit, that is triggered by the pulse from the pulse generator  260 . This information can then be used within the control electronics  276  to determine when the plasma flash  234  occurred in the balloon fluid  132  within the balloon interior  146 . More specifically, the control electronics  276  can compare the timing of the original pulse of energy from the light source  224 , as triggered by the pulse generator  260 , with the timing of the amplified photodetector signal, as gated using the discriminator, to determine when the plasma flash  234  occurred in the balloon fluid  132  within the balloon interior  146 . 
     In some embodiments, the control electronics  276  can be included as part of the system controller  126  (illustrated in  FIG.  1   ). Alternatively, the control electronics  276  can be provided independently of the system controller  126  and can be in electrical communication with the system controller  126 . 
     It is appreciated that there are numerous other configurations for the photodetector  272  that is needed to detect and analyze the light pulse returning from the light guide  222 A in the form of the second light energy  224 C. For example, in another embodiment, the photodetector  272  can be a spectrometer that provides intensity and wavelength information about the second light energy  224 C. In such embodiment, this information can be used to generate a spectral (or flash) signature to further identify specific conditions or events in the light guide  222 A and/or the plasma generator  233 . More particularly, the small quantities of material comprising the plasma generator  233  will be vaporized during its regular operation. These will produce a spectral line that would be distinct. It is further appreciated that this approach could also be used to differentiate between a functioning plasma generator  233  and a broken or damaged light guide  222 A. This could also be used to monitor for external light entering the light guide  222 A and/or the catheter system  200  such as room light spectral signatures. 
     Another application of the present invention would monitor the condition of the light guides  222 A for the plasma generators  233 . The light conducted back through the light guides  222 A when the light guides  222 A are first coupled into the catheter system  200  could be monitored to determine that all light guides  222 A are intact. 
     Thus, as described and illustrated in relation to  FIG.  2 A , the first application for the present invention involves direct detection of the light pulse created by the plasma flash  234  in the balloon fluid  132  within the balloon interior  146 . The optical analyzer assembly  242  can be utilized to indicate the intensity of the light pulse, its spectrum, and when it occurs relative to the input pulse from the light source  224 . This can be interpreted as follows: 
     1) The light pulse must occur after a time interval determined by the length of the light guide  222 A and the duration of the input energy pulse from the light source  224 . If the detected light pulse has the correct intensity and occurs within a specific time window, it is an indication that the plasma generator  233  functioned correctly. 
     2) If no light pulse is detected at all, this is an indication of a failure of the plasma generator  233 , the light source  224  and/or the catheter system  200  as a whole. 
     3) If a smaller light pulse is detected that occurs too early relative to the energy pulse from the light source  224 , this would be an indication of a failure of and/or damage to the light guide  222 A. 
     4) If the light pulse is detected as having a different spectrum or missing a spectral line or signature, this could be used to indicate a failure of the catheter system  200 . 
     In the event of any detected failures of the plasma generator  233 , the light source  224 , the light guide  222 A and/or the catheter system  200  as a whole, the control electronics  276  can be configured to send a signal to the safety shutdown system  283  to shutdown operation of the catheter system  200 . More particularly, in this embodiment, the signal from the control electronics  276  to the safety shutdown system  283  can be used to activate the safety interlock  284 , which blocks the signal from the pulse generator  260  to the light source  224 , thus effectively stopping any generation of light pulses from the light source  224 . Additionally, or in the alternative, the signal from the control electronics  276  to the safety shutdown system  283  can be used to activate the shutter  286  which can be closed, thereby blocking any light pulses from the light source  224  that would otherwise be directed toward and coupled into the light guide  222 A. With such safety shutdown system  283 , potential harms to the patient  109  or operator can be effectively inhibited. 
     Referring now to  FIG.  2 B , the second application for the optical analyzer assembly  242  is illustrated and described. In particular, in this second application, the proper usage of the catheter system  200  can be initially monitored prior to any generation of energy pulses by the light source  224 . 
     As shown, the distal light receiver  222 R can be configured to receive any ambient light  235  that may be present in the area of the guide distal end  222 D of the light guide  222 A. In particular, any visible ambient light  235  present in the area of the guide distal end  222 D of the light guide  222 A can be coupled into the guide distal end  222 D of the light guide  222 A via the distal light receiver  222 R as second light energy  224 C, in the form of an ambient energy beam. 
     The second light energy  224 C travels along and/or through the light guide  222 A from the guide distal end  222 D to the guide proximal end  222 P from where it is emitted from the guide proximal end  222 P of the light guide  222 A. As illustrated in  FIG.  2 B , the second light energy  224 C emitted from the guide proximal end  222 P of the light guide  222 A is collimated by the first optical element  262  before being directed toward the first beam splitter  264 . At least a portion of the second light energy  224 C is then redirected and/or reflected by the first beamsplitter  264  toward the second beamsplitter  268 . The second optical element  266  is positioned in the optical path of the redirected portion of the second light energy  224 C between the first beamsplitter  264  and the second beamsplitter  268 . The optics of the second optical element  266  focus the collimated second light energy  224 C toward the second beamsplitter  268 . The second beamsplitter  268  then transmits at least a portion of the collimated second light energy  224 C through the second filter  278 , such as a short pass filter in certain embodiments, and onto the imaging device  280 , thus forming an image of the guide proximal end  222 P of the light guide  222 A onto the imaging device  280 , and thereby coupling the second light energy  224 C emitted from the guide proximal end  222 P of the light guide  222 A onto the imaging device  280 . Thus, in suitable arrangements, the first optical element  262  and the second optical element  266  can cooperate to create a high-resolution image of the guide proximal end  222 P of the light guide  222 A onto the imaging device  280 . In certain embodiments, the imaging device  280  can be an area sensor such as a CCD or CMOS camera or another suitable type of imaging device. With such design, the visible ambient light  235  collected at the guide distal end  222 D of the light guide  222 A is collected by the imaging device  280 . 
     In some embodiments, the imaging device  280 , under control of the device controller  282 , generates a signal that is based on the visible ambient light  235  collected at the guide distal end  222 D of the light guide  222 A that has been collected by the imaging device  280 . As shown in  FIG.  2 B , the signal from the imaging device  280  is then directed to the control electronics  276 , where detection of any potential ambient light  235  near the guide distal end  222 D of the light guide  222 A is determined. In particular, in certain embodiments, the signal from the imaging device  280  is utilized within the control electronics  276  to determine if any ambient light  235  is present near the guide distal end  222 D of the light guide  222 A. 
     If no ambient light  235  is detected by the optical analyzer assembly  242  as having been collected from the area near the guide distal end  222 D of the light guide  222 A, this is an indication that the catheter system  200  is not being utilized in an improper manner. However, if the optical analyzer assembly  242  detects variation in the light returning from the light guide  222 A, thereby signaling ambient light  235  originating from outside the catheter system  200 , this is an indication that the catheter system  200  is being used in an unintended condition. In such situation, the control electronics  276  can be configured to send a signal to the safety shutdown system  283  to shutdown operation of the catheter system  200 . More particularly, in this embodiment, the signal from the control electronics  276  to the safety shutdown system  283  can be used to activate the safety interlock  284 , which blocks any signal from the pulse generator  260  to the light source  224 , thus effectively stopping any generation of light pulses from the light source  224 . Additionally, or in the alternative, the signal from the control electronics  276  to the safety shutdown system  283  can be used to activate the shutter  286  which can be closed, thereby blocking any light pulses from the light source  224  that would otherwise be directed toward and coupled into the light guide  222 A. With such safety shutdown system  283 , potential harms to the patient  109  or operator can be effectively inhibited. 
     As described in relation to  FIGS.  2 A and  2 B , the optical analyzer assembly  242  utilizes the second beamsplitter  268  and separate filters  270 ,  278  to couple the second light energy  224 C to both the imaging device  280  (an area sensor) and the photodetector  272  (a single element photodetector such as a photodiode). However, it is appreciated that the noted applications for the catheter system  200  and/or the optical analyzer assembly  242  can be implemented in any suitable manner, and can be done in a somewhat different manner that what has been described in detail herein. For example, in one non-exclusive alternative embodiment, the photodetector  272  of the optical analyzer assembly  242  can be used to monitor for ambient light  235  coupled into the guide distal end  222 D of the light guide  222 A, as well as being used to monitor the light pulse created by the plasma flash  234  in the balloon fluid  132  within the balloon interior  146 . In such alternative embodiment, the imaging device  280  would not be used or could be omitted from the catheter system. 
     In summary, the applications of the optical analyzer assembly  242 , as illustrated in  FIGS.  2 A and  2 B , which is configured to monitor nominal operation of the catheter system  200  as well as potential misuse of the catheter system  200 , can include the general steps of: 
     (1) The catheter system starts up from a standby mode; 
     (2) The catheter system continuously monitors usage, via the optical analyzer assembly and/or the imaging device (sometimes referred to as an image sensor subsystem), looking for evidence of ambient light conducted from the guide distal end of the light guide (as evidence of potential improper usage of the system). The optical analyzer assembly and/or the imaging device would monitor the image of the end face of the light guide at a high frame rate looking for non-zero condition or a prescribed variation in signal over time; 
     (3) A pulse generator sends a trigger to the light source (IR laser) to emit an energy pulse. This could be initiated, for example, by an operator pushing an activation button; 
     (4A) The image sensor subsystem detects no light returning from the light guide signaling acceptable use parameters; 
     (4B) The image sensor subsystem detects variation in the light returning from the light guide signaling ambient light originating from outside. This is an indication that the catheter system is being used in an unintended condition and sends a signal to the control electronics; 
     (5A) If step (4A) is met, the control electronics enable usage of the light source through deactivating the safety interlock and/or opening the shutter that otherwise interrupts the source beam. The process then proceeds to step (6); 
     (5B) If step (4B) is met, the control electronics lock out the light source through activation of the safety interlock and/or closing the shutter to stop or interrupt the source beam. The process is then stopped and does not proceed and/or moves back to step (1) after the catheter is repositioned as necessary; 
     (6) The guide beam in the form of first light energy is focused down onto the guide proximal end of the light guide, coupling the pulse of IR energy into it; 
     (7) The pulse of IR energy in the form of the first light energy travels through the light guide and energizes the plasma generator. The plasma generator creates a localized plasma in the balloon fluid within the balloon interior of the balloon; 
     (8) The pulse of broad-spectrum light energy emitted from the plasma in the form of second light energy is coupled back into the guide distal end of the light guide via the distal light receiver, and is conducted back through the light guide to the proximal end; 
     (9) The beamsplitters and optical elements cooperate to form an image of the end face of the light guide on the photodetector; 
     (10) The signal from the photodetector is amplified. This signal can be used to determine the intensity of the plasma event; 
     (11) The pulse from the amplified photodetector is conditioned and this information is used to determine when the plasma event occurred; 
     (12) If no light pulse is detected at all, if a smaller light pulse is detected that occurs too early relative to the energy pulse from the light source, or if the light pulse is detected as having a different spectrum or missing a spectral line or signature, this could be used to indicate a failure of the plasma generator, the light source, the light guide and/or the catheter system as a whole; and 
     (13) If (12) is met, the control electronics lock out the light source through activation of the safety interlock and/or closing the shutter to stop or interrupt the source beam. The process is then stopped and does not proceed. 
     Thus, as noted above, the optical analyzer assembly  242  of the present invention addresses multiple potential issues with the performance, reliability, safety and proper usage of an IVL catheter, in particular one that utilizes an energy source, e.g., a light source such as a laser source, to create a localized plasma which in turn induces a high energy bubble in the balloon fluid  132  within the balloon interior  146  of the balloon  104 . For example, as noted above, issues that are addressed by the present invention include, but are not limited to: 1) optical detection of when the IVL catheter is in position at a treatment site, 2) optical detection of conditions under which the IVL catheter may be misused, 3) optical detection of successful firing of the energy source, such as the laser source, to generate the plasma within the balloon interior, 4) accurate determination of the energy output of the plasma generator, 5) optical detection of a failure of the catheter system to generate the desired plasma within the balloon interior, and 6) optical detection of a failure of the energy guide at any point along the length of the energy guide. 
     The remaining Figures are provided to further illustrate and describe certain features and aspects of the present invention in terms of operation of and analysis by the optical analyzer assembly, and subsequent determination of operational conditions within the catheter system. 
       FIGS.  3 A- 3 F  are simplified schematic illustrations of operational conditions that may be identified by the optical analyzer assembly during operation of the catheter system of  FIG.  1   . More specifically,  FIG.  3 A  is a simplified schematic illustration of a first operational condition  388 A that may be identified by the optical analyzer assembly during operation of the catheter system;  FIG.  3 B  is a simplified schematic illustration of a second operational condition  388 B that may be identified by the optical analyzer assembly during operation of the catheter system;  FIG.  3 C  is a simplified schematic illustration of a third operational condition  388 C that may be identified by the optical analyzer assembly during operation of the catheter system;  FIG.  3 D  is a simplified schematic illustration of a fourth operational condition  388 D that may be identified by the optical analyzer assembly during operation of the catheter system;  FIG.  3 E  is a simplified schematic illustration of a fifth operational condition  388 E that may be identified by the optical analyzer assembly during operation of the catheter system; and  FIG.  3 F  is a simplified schematic illustration of a sixth operational condition  388 F that may be identified by the optical analyzer assembly during operation of the catheter system. 
     As shown in  FIG.  3 A , the light guide  322 A and the plasma generator  333  are illustrated where the first operational condition  388 A is a normal operation condition. In such normal operation condition, plasma  334  and a subsequent acoustic wave (illustrated as a series of arced lines) is generated substantially directly adjacent to the plasma generator  333  when the first light energy  324 B is directed from the guide distal end  322 D of the light guide  322 A toward the plasma generator  333  and thus impinges on a target surface  333 T of the plasma generator  333 . 
     In  FIG.  3 B , the light guide  322 A and the plasma generator  333  are illustrated in the second operational condition  388 B where intermittent gas bubble production conditions exist. In such second operational condition  388 B, gas bubbles  389  (one gas bubble  389  is shown in  FIG.  3 B ) formed within the balloon fluid  132  (illustrated in  FIG.  1   ) are found between the guide distal end  322 D of the light guide  322 A and the plasma generator  333  that optically impact the directing of the first light energy  324 B toward the target surface  333 T of the plasma generator  333 . Thus, little to no plasma (not shown in  FIG.  3 B ) is generated and the resulting flash signature may have a lower pulse maximum value than would be desired in order to most effectively disrupt the vascular lesions  106 A (illustrated in  FIG.  1   ) at the treatment site  106  (illustrated in  FIG.  1   ). Under such conditions, the operator may be able to treat the fluid pump  138  (illustrated in  FIG.  1   ) and/or the inflation conduit  140  (illustrated in  FIG.  1   ) in order to inhibit the creation of such intermittent gas bubbles  389  without the need to shut down operation of the catheter system  100  (illustrated in  FIG.  1   ) and replace the light guide  322 A and/or the plasma generator  333 . 
     In  FIG.  3 C , the light guide  322 A and the plasma generator  333  are illustrated in the third operational condition  388 C where guide distal end plasma initiation conditions exist. In such third operational condition  388 C, there may be some debris substantially adjacent to the guide distal end  322 D of the light guide  322 A which causes plasma  334  and a subsequent acoustic wave (illustrated as a series of arced lines) to be generated at such point substantially adjacent to the guide distal end  322 D of the light guide  322 A rather than substantially directly adjacent to the plasma generator  333 . The resulting flash signature may have a higher pulse maximum value than under nominal conditions. This may also impact the ability of the catheter system  100  (illustrated in  FIG.  1   ) to most effectively disrupt the vascular lesions  106 A (illustrated in  FIG.  1   ) at the treatment site  106  (illustrated in  FIG.  1   ). However, the third operational condition  388 C may be cleared up with subsequent cleaning of such areas within the balloon  104  (illustrated in  FIG.  1   ) without the need to shut down operation of the catheter system  100  and replace the light guide  322 A and/or the plasma generator  333 . 
     In  FIG.  3 D , the light guide  322 A is illustrated in the fourth operational condition  388 D where housing/target failure conditions exist. In such fourth operational condition  388 D, there is a failure to generate the desired plasma flash in the balloon fluid  132  (illustrated in  FIG.  1   ) within the balloon interior  146  (illustrated in  FIG.  1   ) from the first light energy  324 B being directed by the light guide  322 A. Under such condition, the resulting flash signature has a lower pulse maximum value. This provides evidence that there is a failure of the light guide  322 A and/or the plasma generator  333  (illustrated, for example, in  FIG.  3 A ) during the process of trying to generate the desired plasma flash in order to effectively disrupt the vascular lesions  106 A (illustrated in  FIG.  1   ) at the treatment site  106  (illustrated in  FIG.  1   ). Thus, in order to correct or overcome this condition, use of the catheter system  100  (illustrated in  FIG.  1   ) is stopped and the light guide  322 A and/or the plasma generator  333  can be removed and replaced or the catheter system  100  can be discarded as a whole. It is noted that the plasma generator  333  is not illustrated in  FIG.  3 D  to more clearly illustrate the failure of the desired plasma generation. 
     In  FIG.  3 E , the light guide  322 A is illustrated in the fifth operational condition  388 E where broken light guide (fiber) conditions exist. In such fifth operational condition  388 E, little to no plasma (not shown in  FIG.  3 E ) is generated in the balloon fluid  132  (illustrated in  FIG.  1   ) within the balloon interior  146  (illustrated in  FIG.  1   ), and any minimal plasma that is generated would typically have a lower pulse maximum value due to the first light energy  324 B being directed in multiple disparate directions away from the guide distal end  322 D of the light guide  322 A rather than just directly toward the plasma generator  333  (illustrated, for example, in  FIG.  3 A ). It is appreciated that this failure mode can happen anywhere along the length of the catheter, and not just within the balloon. When such fifth operational condition  388 E is determined to exist, operation of the catheter system  100  (illustrated in  FIG.  1   ) should be stopped. 
     In  FIG.  3 F , the light guide  322 A and the plasma generator  333  are illustrated in the sixth operational condition  388 F where chewback conditions exist, such as broken light guides  322 A along the length of the light guide  322 A and at least somewhat spaced apart from the guide distal end  322 D. In such sixth operational condition  388 F, plasma  334  (illustrated as a series of arced lines) generation can occur in the balloon fluid  132  (illustrated in  FIG.  1   ) within the balloon interior  146  (illustrated in  FIG.  1   ) substantially adjacent to where a break may exist along the length of the light guide  322 A. Under such conditions, the resulting flash signature is typically very jagged, increasing and decreasing in magnitude very quickly over time. When such sixth operational condition  388 F is determined to exist, any plasma  334  generated is much less likely to be directed in an appropriate manner so as to effectively disrupt the vascular lesions  106 A (illustrated in  FIG.  1   ) at the treatment site  106  (illustrated in  FIG.  1   ). Thus, operation of the catheter system  100  (illustrated in  FIG.  1   ) should be stopped. 
     As provided herein, much of the analysis undertaken through use of the optical analyzer assembly involves the capturing of an image of a flash signal (or flash signature) that stems from plasma generation in the balloon fluid within the balloon interior, and the subsequent analysis of the flash signal (or flash signature) as a means to determine the operational condition of the catheter system. It is appreciated that the flash signal (or flash signature) can take any specific form and there are infinite possibilities for all the details incorporated within the flash signal (or flash signature).  FIGS.  4 A and  4 B  provide simplified graphical illustrations of just two potential examples of what the flash signal (or flash signature) may look like as captured through use of the optical analyzer assembly. 
       FIG.  4 A  is a simplified graphical illustration of a representative example of a first flash signature  490 A that may be identified by the optical analyzer assembly  242  (illustrated, for example, in  FIG.  2 A ) during operation of the catheter system  100  of  FIG.  1   , in terms of flash intensity (Y-axis) versus time (X-axis). More particularly, the first flash signature  490 A would be identified by the optical analyzer assembly  242  during the generation of a plasma flash  334  (illustrated in  FIG.  3 A ) from a single pulse of first light energy  324 B (illustrated in  FIG.  3 A ) from the light source  124  (illustrated in  FIG.  1   ) through the light guide  322 A (illustrated in  FIG.  3 A ). As illustrated, the first flash signature  490 A has a single peak  491 A and two transitions  492 A. In analyzing the peaks in any given flash signature, the largest or highest peak can also be referred to as the “pulse maximum intensity” value or simply the “pulse maximum”. In  FIG.  4 A , the first flash signature  490 A only has the single peak  491 A, so that single peak  491 A would also be referred to as the pulse maximum intensity value, or the “pulse maximum”. 
       FIG.  4 B  is a simplified graphical illustration of a representative example of a second flash signature  490 B that may be identified by the optical analyzer assembly  242  (illustrated, for example, in  FIG.  2 A ) during operation of the catheter system  100  of  FIG.  1   , in terms of flash intensity (Y-axis) versus time (X-axis). More particularly, the second flash signature  490 B would be identified by the optical analyzer assembly  242  during the generation of a plasma flash  334  (illustrated in  FIG.  3 A ) from a single pulse of first light energy  324 B (illustrated in  FIG.  3 A ) from the light source  124  (illustrated in  FIG.  1   ) through the light guide  322 A (illustrated in  FIG.  3 A ). As illustrated, the second flash signature  490 B has three peaks  491 B and six transitions  492 B. Again, in analyzing the peaks in any given flash signature, the highest peak can also be referred to as the “pulse maximum intensity” value or simply the “pulse maximum”. In  FIG.  4 B , the second flash signature  490 B has three peaks  491 B, with the first peak  491 B being the largest or highest, and thus would also be referred to as the pulse maximum intensity value, or the “pulse maximum”. 
     As referred to herein, a “transition” is defined generally as a change in direction of the slope of the flash signature as shown in the graphical illustration. As shown in  FIGS.  4 A and  4 B , both signals have a transition as the signal quickly climbs from the X-axis. Both signals also have another transition as the signal drops down from the pulse maximum.  FIG.  4 B  has more transitions or volatility in the signal after this point. The exact number of transitions measured in each signal is dependent on the tuning of various parameters. One parameter defines the slope change magnitude required to classify something as a transition and the other is a hysteresis parameter to avoid counting transitions on noise in the signature. 
       FIG.  5    is a simplified graphical illustration  593  of an example of pulse maximum intensity readings that may be identified by the optical analyzer assembly from the plasma flashes generated as pulses of first light energy are sent through a light guide used within the catheter system of  FIG.  1   . As shown, the pulse maximum intensity reading (in arbitrary units) from the plasma flashes generated for each pulse of first light energy being guided through the light guide is shown along the Y-axis, and the pulse number for the specific light guide is shown along the X-axis. Stated in another manner, the Y-axis relates to the maximum value that is found in the flash signature (or flash signal) that is detected by the optical analyzer assembly for any given pulse of first light energy that is sent through the given light guide. 
       FIG.  5    illustrates both a minimum pulse maximum intensity threshold  594  and a maximum pulse maximum intensity threshold  595  that can be used by the system controller to help define the operational condition of the light guide and/or the plasma generator. 
     The minimum pulse maximum intensity threshold  594  can be used by the system controller to determine if the operational condition of the light guide is one of intermittent gas bubble production conditions; housing/target failure conditions; and/or broken light guide (fiber) conditions. In any of such operational conditions, the pulse maximum intensity will have a low value that provides an indication that the plasma flash, if any, may not be sufficient to effectively disrupt the vascular lesions at the treatment site. 
     It is appreciated that a pulse maximum intensity value of at or very near zero would be an indication of any of the conditions described in the previous paragraph, where little or no plasma flash has occurred. Because of this ambiguity in the potential failure mode, the history of all pulses on each fiber can be tracked to distinguish among such conditions, instead of responding to a single instance of no signal detection conditions. As discussed further below, the pulse maximum intensity value would not necessarily have to be zero to indicate such failure conditions because it is always possible that at least some extraneous light may be captured by the distal light receiver and sent back as second light energy from the guide distal end toward the guide proximal end. 
     In one non-exclusive embodiment, the minimum pulse maximum intensity threshold  594  can be approximately 100 units, such that any registered pulse maximum intensity value at or below 100 units can indicate such undesired operational conditions for the light guide. Alternatively, in other embodiments, the minimum pulse maximum intensity threshold  594  can be approximately 50 units, 75 units, 125 units, 150 units, 175 units, 200 units, or another suitable minimum pulse maximum intensity threshold value. 
     As further described below in relation to  FIG.  7   , it is appreciated that to avoid any potential false positive readings for no signal detection conditions, it may be desired to require a certain number of pulses of first light energy to have a pulse maximum intensity value below a no signal detection pulse maximum intensity threshold value, such as 50 units in one non-exclusive embodiment, within a certain range or number of pulses of first light energy, in order for a true positive identification of such no signal detection conditions. 
     The maximum pulse maximum intensity threshold  595  can be used by the system controller to determine if the operational condition of the light guide is guide distal end plasma initiation conditions. Under such conditions, the pulse maximum intensity of the plasma flash as the second light energy is sent back through the light guide to be optically analyzed by optical analyzer assembly may be higher than under normal operating conditions because the plasma flash is often larger and occurs substantially directly adjacent to the guide distal end of the light guide. Simply stated, under such conditions, more second light energy would be received by the distal light receiver and thus sent back through the light guide in the second direction because such light energy is generated and/or reflected substantially directly adjacent to the guide distal end and thus the distal light receiver. 
     In one non-exclusive embodiment, the maximum pulse maximum intensity threshold  595  can be approximately 1000 units, such that any registered pulse maximum intensity value at or above 1000 units can indicate such an undesired operational condition for the light guide. Alternatively, in other embodiments, the maximum pulse maximum intensity threshold  595  can be approximately 900 units, 925 units, 950 units, 975 units, 1025 units, 1050 units, 1075 units, 1100 units, 1125 units, 1150 units, or another suitable maximum pulse maximum intensity threshold value. 
       FIG.  5    further illustrates typical pulse maximum intensity values for the plasma flash when the light guide is operating under normal operating conditions, i.e. a normal pulse maximum intensity range  596 . In one non-exclusive embodiment, normal operating conditions can be determined if the normal pulse maximum intensity range  596  is between approximately 300 units and 800 units. Alternatively, the normal pulse maximum intensity range  596  for an indication of normal operating conditions can vary from the noted range, so long as such normal pulse maximum intensity range  596  does not overlap or go beyond the minimum pulse maximum intensity threshold  594  (i.e. below such minimum pulse maximum intensity threshold  594 ) or beyond the maximum pulse maximum intensity threshold  595  (i.e. above such maximum pulse maximum intensity threshold  595 ). For example, in certain non-exclusive alternative embodiments, the normal pulse maximum intensity range  596  for the plasma flash can be between approximately 200 units and 900 units; between approximately 250 units and 850 units, between approximately 350 units and 900 units, between approximately 300 units and 850 units, or some other range of suitable pulse maximum intensity values. 
       FIG.  6    is a simplified graphical illustration  693  of an example of a number of transitions that may be identified by the optical analyzer assembly within a flash signal generated as pulses of first light energy are sent through a light guide used within the catheter system of  FIG.  1   . As shown, the number of transitions identified in the flash signature (or flash signal) for the light guide for any given pulse of first light energy is shown along the Y-axis, and the pulse number for the specific light guide is shown along the X-axis.  FIG.  6    provides an indication that the light guide may be suffering from chewback when the number of transitions within the plasma signature for any given pulse of first light energy is above a certain transition threshold  697 . In one embodiment, as shown, the transition threshold  697  for identifying the light guide as suffering from chewback can be six transitions. Alternatively, in other embodiments, the transition threshold  697  for identifying the light guide as suffering from chewback can be four transitions, five transitions, seven transitions, eight transitions, nine transitions, ten transitions, or another suitable number of transitions. 
     It is appreciated that to avoid any potential false positive readings for identifying chewback conditions, it may be desired to require a certain number of pulses of first light energy to have the number of transitions be at or above the transition threshold  697  in order for a true positive identification of chewback conditions. For example, in one non-exclusive embodiment, it may be required to find at least three pulses of first light energy where the number of transitions is at or above the transition threshold to positively identify chewback conditions. Alternatively, in other embodiments, it may be required to find only one or at least two, four, five, six, or some other suitable number of pulses of first light energy where the number of transitions is at or above the transition threshold to positively identify chewback conditions. 
       FIG.  7    is a simplified graphical illustration  793  of an example of how no signal detection conditions can be identified by the optical analyzer assembly as pulses of first light energy are sent through a light guide used within the catheter system of  FIG.  1   . Similar to  FIG.  5   , the pulse maximum intensity reading (in arbitrary units) from the plasma flashes generates for each pulse of first light energy being guided through the light guide is shown along the Y-axis, and the pulse number for the specific light guide is shown along the X-axis. Stated in another manner, the Y-axis relates to the highest peak that is found in the flash signature (or flash signal) that is detected by the optical analyzer assembly for any given pulse of first light energy that is sent through the given light guide. 
     As illustrated,  FIG.  7    shows a zero threshold  798  (or no signal detection threshold), and a window zero count  799  (or a no signal detection range). For purposes of effectively establishing a condition of no signal detection (and/or to avoid improperly identifying such a condition), in various embodiments, it may be required to find a certain number of pulses (or zero pulse count) within the window zero count  799  (a given number or range of preceding pulses) that have a pulse maximum intensity value below the zero threshold  798 . Stated in another manner, if the number of pulses within the previous window zero count  799  of pulses of first light energy through a given light guide that have a pulse maximum intensity value of less than the zero threshold  798  meets or exceeds the zero pulse count, then the system effectively identifies a no signal detection condition. 
     It is appreciated that all of the zero threshold  798 , the window zero count  799 , and the zero pulse count can be varied in the process of endeavoring to positively identify the no signal detection condition. For example, in one non-exclusive embodiment, the zero threshold  798  can be established where the pulse maximum intensity value for a given pulse of first light energy through the light guide is not greater than 50 units. Alternatively, in other embodiments, the zero threshold  798  can be established where the pulse maximum intensity value is no greater than 10 units, 15 units, 20 units, 25 units, 30 units, 35 units, 40 units, 45 units, 55 units, 60 units, 65 units, 70 units, 75 units, or some other suitable number of units. 
     In one non-exclusive embodiment, the window zero count  799  can refer to a range of 20 pulses over which the defined zero pulse count of pulses of first light energy being sent through the given light guide must have a reading at or below the zero threshold  798  to effectively identify a no signal detection condition. Alternatively, in other embodiments, the window zero count  799  can refer to a range of 15 pulses, 16 pulses, 17 pulses, 18 pulses, 19 pulses, 21 pulses, 22 pulses, 23 pulses, 24 pulses, 25 pulses, 26 pulses, 27 pulses, 28 pulses, 29 pulses, 30 pulses, 31 pulses, 32 pulses, 33 pulses, 34 pulses, 35 pulses, 36 pulses, 37 pulses, 38 pulses, 39 pulses, 40 pulses, or another suitable number of pulses over which the defined zero pulse count of pulses of first light energy being sent through the given light guide must have a reading at or below the zero threshold  798  to effectively identify a no signal detection condition. As utilized herein, the window zero count  799  is specifically the number of previous pulses to look at on a given light guide when determining the no signal detection condition instead of considering the entire history of the light guide. 
     In one non-exclusive embodiment, the defined zero pulse count can be 11 pulses of first light energy being sent through the given light guide that have a reading at or below the zero threshold  798  within the window zero count  799  range to effectively identify a no signal detection condition. Alternatively, the defined zero pulse count can be 5, 6, 7, 8, 9, 10, 12, 13, 14, 15, 16, 17, 18, 19, 20, or some other suitable number of pulses of first light energy being sent through the given light guide that have a reading at or below the zero threshold  798  within the window zero count  799  range to effectively identify a no signal detection condition. 
     In one specific, non-exclusive embodiment, if the zero threshold is 50 units, the window zero count is 20 pulses, and the defined zero pulse count is 11 pulses; then to effectively determine a no signal detection condition, one must find at least 11 pulses of first light energy through the given light guide within the preceding 20 pulses which have a pulse maximum intensity value of less than the zero threshold of 50 units. 
     It is appreciated that the present invention could be used to monitor the location and condition of any device using an optical light source and light guide for energy transmission. One alternative example is nephrolithotomy using laser lithotripsy. In particular, the beamsplitter and optics comprising this invention could be incorporated into a lithotripsy laser system. This would allow continuous monitoring of light in the form of second light energy returning from the guide distal end of the lithotripsy light guide. When the light guide is inserted through the nephroscope into the kidney, the ambient lighting conditions are controlled by the nephroscope illumination. The characteristic and spectrum of the light detected could be used to determine if the light guide is positioned correctly inside the kidney and it is safe to fire the light source. One means of accomplishing this would be using a signal source with specific wavelength characteristics in the scope illumination. For example, an included narrow band source with high intensity that would not be present in external ambient lighting. This could be detected using a bandpass filter ahead of the photodetector. The light source would be locked out until that optical signal was detected, preventing firing the light source and emitting hazardous laser radiation outside of the patient. 
     In summary, the catheter systems and related methods disclosed herein are configured to monitor the safety, performance, reliability and proper usage of an intravascular lithotripsy (IVL) catheter. In various embodiments, the catheter systems of the present invention utilize an energy source, e.g., a light source such as a laser source or another suitable energy source, which provides energy that is guided by an energy guide, such as a light guide, to create a localized plasma in a balloon fluid within a balloon interior of an inflatable balloon of the catheter. As such, the energy guide can sometimes be referred to as, or can be said to incorporate a “plasma generator” at or near a guide distal end of the energy guide that is positioned within the balloon interior. This localized plasma generates pressure waves that impart pressure onto and induce fractures at a treatment site within or adjacent to a blood vessel or a heart valve within a body of a patient. As used herein, the treatment site can include a vascular lesion such as a calcified vascular lesion or a fibrous vascular lesion, typically found in a blood vessel and/or a heart valve. 
     In particular, in various embodiments, the catheter systems can include a catheter configured to advance to the treatment site within or adjacent a blood vessel or heart valve within the body of the patient. The catheter includes a catheter shaft, and a balloon that is coupled and/or secured to the catheter shaft. The balloon can include a balloon wall that defines the balloon interior and can be configured to receive the balloon fluid within the balloon interior to expand from a deflated state suitable for advancing the catheter through a patient&#39;s vasculature, to an inflated state suitable for anchoring the catheter in position relative to the treatment site. The catheter systems also include one or more energy guides disposed along the catheter shaft and within the balloon. Each energy guide can be configured for generating pressure waves within the balloon for disrupting the vascular lesions. 
     The catheter systems utilize energy from an energy source, such as first light energy from a light source, to generate the plasma, such as via the plasma generator, within the balloon fluid at or near a guide distal end of the energy guide disposed in the balloon located at the treatment site. The plasma formation can initiate one or more pressure waves and can initiate the rapid formation of one or more bubbles that can rapidly expand to a maximum size and then dissipate through a cavitation event that can launch pressure waves upon collapse. The rapid expansion of the plasma-induced bubbles can generate one or more pressure waves within the balloon fluid retained within the balloon and thereby impart pressure waves upon the treatment site. In some embodiments, the energy source can be configured to provide sub-millisecond pulses of energy from the energy source to initiate plasma formation in the balloon fluid within the balloon to cause rapid bubble formation and to impart pressure waves upon the balloon wall at the treatment site. Thus, the pressure waves can transfer mechanical energy through an incompressible balloon fluid to the treatment site to impart a fracture force on the treatment site. 
     As described in detail herein, the catheter systems of the present invention include an optical analyzer assembly that is configured to provide real-time continuous monitoring of the energy emitted from the guide distal end of the energy guide into the balloon interior, which can be used to detect that a plasma event has occurred and to monitor for nominal operation of the catheter system. The optical analyzer assembly is further configured to monitor ambient energy received into the guide distal end of the energy guide, which can be used as a monitor for proper usage and positioning of the catheter system. For example, monitoring of the ambient energy conducted from the distal end of the energy guide starting at the plasma generator can be used to detect the state and condition of the overall device as a monitor for nominal and safe operation. Similarly, measuring variations in the intensity of the conducted energy over a time interval provides an indication of the location of the distal end and plasma generator itself. When located inside of a human body, the ambient energy conducted through the energy guide will be minimal. It would be expected this would be zero, and any baseline minimally variable. Conversely, the energy conducted when the device is located outside the human body will be nonzero and highly variable. This information can be used to determine the location of the distal end of the energy guide. This in turn could be used to assess the condition of the energy guide and determine if the device is performing nominally. 
     The optical analyzer assembly can also be utilized to measure the intensity of the energy emitted from the energy guide in order to provide an accurate measurement of the energy output of the plasma generator that is incorporated as part of and/or used in conjunction with the energy guide. More specifically, the measurement of the energy output of the plasma generator can be used in conjunction with the known energy input from the energy source to determine the conversion efficiency. Such metric can also be used to assess the condition of the plasma generator and energy guide and determine if the catheter system is performing normally, as well as the number of operation cycles remaining. 
     In particular, in various embodiments, the present invention comprises a means of sampling second light energy returned from the plasma generator and/or from the balloon interior back through the energy guide. It is appreciated that energy can travel in both, opposing directions along the length of the energy guide. Thus, it is possible to detect energy originating at the guide distal end of the energy guide, or at any other position along the length of the energy guide, at a guide proximal end of the energy guide. Such second light energy that is transmitted back through the energy guide will thus be separated and detected and/or analyzed via the optical analyzer assembly to effectively monitor the safety, performance, reliability and proper usage of the catheter system. 
     It is appreciated that the continuous monitoring of the energy emitted from the plasma generator, and the measuring of the intensity of the emitted energy, through use of the present invention, addresses multiple potential issues with the safety, performance, reliability and proper usage of an IVL catheter, in particular one that utilizes an energy source to create a localized plasma which in turn produces a high energy bubble inside a balloon catheter. Specific issues this invention addresses include: 1) optical detection of when the IVL catheter is in position at a treatment site, 2) optical detection of conditions under which the IVL catheter may be misused, 3) optical detection of successful firing of the energy source, such as the laser source, to generate the plasma within the balloon interior, 4) accurate determination of the energy output of the plasma generator, 5) optical detection of a failure of the catheter system to generate the desired plasma within the balloon interior, and 6) optical detection of a failure of the energy guide at any point along the length of the energy guide. 
     It is further appreciated that when improper usage or failure of the catheter system is detected and/or if a failure of the energy guide is detected at any point along the length of the energy guide, the optical analyzer assembly can be configured to automatically stop operation of the catheter system. Thus, in various embodiments, the catheter system and/or the optical analyzer assembly can incorporate and/or include a safety shutdown system that can be selectively activated when warranted to automatically stop operation of the catheter system. In some such embodiments, the safety shutdown system can include one or more of a safety interlock, a shutter and/or other suitable safety shutdown mechanisms that can be incorporated into the optical analyzer assembly. With such design, the optical analyzer assembly is uniquely configured to inhibit dangerous conditions for the patient and the operator of the catheter system. 
     It should be noted that, as used in this specification and the appended claims, the singular forms “a,” “an,” and “the” include plural referents unless the content and/or context clearly dictates otherwise. It should also be noted that the term “or” is generally employed in its sense including “and/or” unless the content or context clearly dictates otherwise. 
     It should also be noted that, as used in this specification and the appended claims, the phrase “configured” describes a system, apparatus, or other structure that is constructed or configured to perform a particular task or adopt a particular configuration. The phrase “configured” can be used interchangeably with other similar phrases such as arranged and configured, constructed and arranged, constructed, manufactured and arranged, and the like. 
     The headings used herein are provided for consistency with suggestions under 37 CFR 1.77 or otherwise to provide organizational cues. These headings shall not be viewed to limit or characterize the invention(s) set out in any claims that may issue from this disclosure. As an example, a description of a technology in the “Background” is not an admission that technology is prior art to any invention(s) in this disclosure. Neither is the “Summary” or “Abstract” to be considered as a characterization of the invention(s) set forth in issued claims. 
     The embodiments described herein are not intended to be exhaustive or to limit the invention to the precise forms disclosed in the detailed description provided herein. Rather, the embodiments are chosen and described so that others skilled in the art can appreciate and understand the principles and practices. As such, aspects have been described with reference to various specific and preferred embodiments and techniques. However, it should be understood that many variations and modifications may be made while remaining within the spirit and scope herein. 
     It is understood that although a number of different embodiments of the catheter systems have been illustrated and described herein, one or more features of any one embodiment can be combined with one or more features of one or more of the other embodiments, provided that such combination satisfies the intent of the present invention. 
     While a number of exemplary aspects and embodiments of the catheter systems have been discussed above, those of skill in the art will recognize certain modifications, permutations, additions and sub-combinations thereof. It is therefore intended that the following appended claims and claims hereafter introduced are interpreted to include all such modifications, permutations, additions and sub-combinations as are within their true spirit and scope, and no limitations are intended to the details of construction or design herein shown.