Patent Publication Number: US-2023144756-A1

Title: Multi-sensor interferometry systems and methods

Description:
CROSS REFERENCE TO RELATED APPLICATION 
     This application claims the benefit of U.S. Provisional Application No. 63/278,320, which was filed on Nov. 11, 2021 and is incorporated by reference herein. 
    
    
     TECHNICAL FIELD 
     The present technology relates to systems and methods for providing hemodynamic support to a patient with an intravascular blood pump. In some implementations, the blood pump includes a plurality of optical pressure sensors for measuring a plurality of pressures within the patient’s vascular system. 
     BACKGROUND 
     Intravascular blood pumps may be used to provide hemodynamic support to the heart of a patient (e.g., during a high-risk percutaneous coronary intervention). For example, an intravascular blood pump may be introduced percutaneously into a patient’s blood vessel (e.g., the femoral artery) and guided through the patient’s vascular system in order to support or replace the pumping action in the patient’s heart. An intravascular blood pump may include an inlet area, an outlet area, a cannula, a motor housing, a catheter, and one or more sensors. During operation, an intravascular blood pump may be positioned such that the cannula extends through an opened cardiac valve to enable blood to be pumped through the cardiac valve. For example, blood may be drawn into one or more openings of the inlet area, channeled through the cannula, and expelled through one or more openings of the outlet area by a motor disposed within the motor housing. The one or more sensors may, for example, be used to measure one or more pressures within one or more chambers of the patient’s heart. Such measurements may, for example, be used to monitor the patient and/or assist with the positioning of the blood pump within the patient’s vascular system. Signals from the one or more sensors may be provided to a controller through one or more lines (e.g., optical and/or electrical lines) extending through the blood pump. To improve the portability of these types of systems, there is a need to reduce the size and/or power consumption of the controller and/or the intravascular blood pump. 
     BRIEF SUMMARY 
     Systems and methods for providing hemodynamic support to a patient with an intravascular blood pump are disclosed. In some implementations, a ventricular support system includes a light source, a fiber optic splitter, two or more filters, an intravascular blood pump having two or more sensor heads, and a photodetector. At least some of the light transmitted by the light source is split by the fiber optic splitter such that a portion is transmitted to each of the two or more filters. Each portion of light is filtered by one of the two or more filters and delivered to one of the two or more sensor heads. Light beams reflected from each of the two or more sensor heads are combined by the fiber optic splitter. At least some of the combined light beams are received by the photodetector. By only using a single light source and a single photodetector with the two or more sensor heads, the ventricular support system may have improved portability. 
     One aspect of the present disclosure relates to a ventricular support system that includes a light source, an intravascular blood pump, a first filter, a second filter, a first fiber optic splitter, and a first photodetector. The light source is configured to transmit light. The intravascular blood pump includes a first sensor head and a second sensor head, wherein the first sensor head is positioned distally relative to the second sensor head. The first filter is directly or indirectly coupled to the first sensor head. The first filter permits a first sub-spectrum of the light transmitted by the light source to pass through it. The second filter is directly or indirectly coupled to the second sensor head. The second filter permits a second sub-spectrum of the light transmitted by the light source to pass through it, wherein the first and second sub-spectrums are different. The first fiber optic splitter is directly or indirectly coupled to the first and second filters. The first fiber optic splitter is configured to split at least some of the light transmitted by the light source such that a first portion is transmitted to the first filter and a second portion is transmitted to the second filter. The first fiber optic splitter is also configured to combine a plurality of light beams reflected from the first and second sensor heads. The first photodetector is configured to receive at least some of the combined plurality of light beams reflected from the first and second sensor heads. 
     In some implementations, the first filter is directly coupled to the first sensor, and the second filter is directly coupled to the second sensor. In some implementations, the first fiber optic splitter is (a) coupled to the first filter through a first optical fiber extending through at least a portion of a catheter of the intravascular blood pump, and (b) coupled to the second filter through a second optical fiber extending through at least a portion of the catheter. In some implementations, the first filter is coupled to the first sensor head through a first optical fiber extending through at least a portion of a catheter of the intravascular blood pump, and the second filter is coupled to the second sensor head through a second optical fiber extending through at least a portion of the catheter. In some implementations, the first filter is a short-pass filter, and the second filter is a long pass filter. In some implementations, the first and second filters are band-pass filters. In some implementations, the first and second sub-spectrums overlap. In some implementations, the first and second sub-spectrums do not overlap. 
     In some implementations, the system further includes a beam splitter coupled to the first fiber optic splitter through a first optical fiber extending through at least a portion of a catheter of the intravascular blood pump. In some implementations, each of the first and second sensor heads comprise a cavity and a pressure-sensitive membrane. In some implementations, the cavity and the pressure-sensitive membrane of each of the first and second sensor heads form part of a Fabry-Perot cavity. In some implementations, the system further includes a mirror configured to reflect at least some of the light transmitted by the light source towards the first photodetector, and each of the first and second sensor heads comprises a mirror attached to a bottom surface of the pressure-sensitive membrane that faces the cavity. 
     In some implementations, the system further includes a third filter directly or indirectly coupled to a third sensor head of the intravascular blood pump, wherein the third filter permits a third sub-spectrum of the light transmitted by the light source to pass through it, and wherein the first, second, and third sub-spectrums are different, wherein the first fiber optic splitter is configured to split at least some of the light transmitted by the light source such that a third portion is transmitted to the third filter, and wherein the first fiber optic splitter is configured to combine a plurality of light beams reflected from the first, second, and third sensor heads. 
     In some implementations, the system further includes a controller communicatively coupled to the light source and the first photodetector. In some implementations, the first photodetector is configured to capture an image of a combined interference pattern formed by the combined plurality of light beams reflected from the first and second sensor heads, and the controller is configured to digitally filter the image to separate the interference patterns created by the first and second sensor heads. 
     In some implementations, the system further includes (a) a second photodetector configured to receive at least some of the combined plurality of light beams reflected from the first and second sensor heads, (b) a third filter directly or indirectly coupled to the first photodetector, wherein the third filter permits the first sub-spectrum of the light transmitted by the light source to pass through it, (c) a fourth filter directly or indirectly coupled to the second photodetector, wherein the fourth filter permits the second sub-spectrum of the light transmitted by the light source to pass through it, and (d) a second fiber optic splitter directly or indirectly coupled to the third and fourth filters, wherein the second fiber optic splitter is configured to split at least some of the combined plurality of light beams reflected from the first and second sensor heads such that a first portion is transmitted to the third filter and a second portion is transmitted to the fourth filter. 
     Another aspect of the present disclosure relates to a method that includes (a) transmitting, from a light source, a first light beam, (b) splitting, with a fiber optic splitter, at least some of the first light beam received by the fiber optic splitter into a second light beam and a third light beam, (c) filtering, with a first filter, at least some of the second light beam received by the first filter, wherein the first filter permits a first sub-spectrum of the second light beam to pass through it, (d) filtering, with a second filter, at least some of the third light beam received by the second filter, wherein the second filter permits a second sub-spectrum of the third light beam to pass through it, and wherein the first and second sub-spectrums are different, (e) reflecting, with a first sensor head of an intravascular blood pump, at least some of the filtered second light beam to produce a first reflected light beam, (f) reflecting, with a second sensor head of the intravascular blood pump, at least some of the filtered third light beam to produce a second reflected light beam, (g) combining, with the fiber optic splitter, the first and second reflected light beams, and (h) receiving, with a photodetector, at least some of the combined first and second reflected light beams. 
     In some implementations, the method further includes deriving a ventricular pressure and an aortic pressure from the at least some of the combined first and second reflected light beams received by the photodetector. In some implementations, each of the first and second sensor heads comprises a cavity and a pressure-sensitive membrane. In some implementations, the cavity and the pressure-sensitive membrane of each of the first and second sensor heads form part of a Fabry-Perot cavity. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG.  1    illustrates a ventricular support system that includes an intravascular blood pump positioned within the heart of a patient. 
         FIG.  2    illustrates aspects of an optical pressure sensor of the intravascular blood pump of  FIG.  1    in greater detail. 
         FIG.  3    illustrates aspects of the intravascular blood pump of  FIG.  1    in greater detail. 
         FIGS.  4 A and  4 B  illustrate aspects of an optical pressure sensor of the intravascular blood pump of  FIG.  1    in greater detail. 
         FIGS.  5 A and  5 B  illustrate aspects of an optical pressure sensor of the intravascular blood pump of  FIG.  1    in greater detail. 
         FIG.  6    illustrates a multi-sensor interferometry system. 
         FIG.  7    illustrates a multi-sensor interferometry system. 
         FIG.  8    illustrates a multi-sensor interferometry system. 
     
    
    
     DETAILED DESCRIPTION 
     Implementations of the present disclosure are described in detail with reference to the drawing figures wherein like reference numerals identify similar or identical elements. It is to be understood that the disclosed implementations are merely examples of the disclosure, which may be embodied in various forms. Well-known functions or constructions are not described in detail to avoid obscuring the present disclosure in unnecessary detail. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present disclosure in virtually any appropriately detailed structure. 
       FIG.  1    illustrates a ventricular support system that includes an intravascular blood pump  50  and a controller  40  (e.g., an Automated Impella Controller® from Abiomed, Inc., Danvers, MA). Blood pump  50  includes a catheter  20 , a motor section  51 , a pump section  52 , a cannula  53 , an inlet area  54 , a soft-flexible tip  55 , an outlet area  56 , and optical sensor heads  30  and  60 . Optical fibers  28 A and  28 B extend through catheter  20 . Controller  40  may transmit and/or receive signals from sensor heads  30  and  60  through optical fibers  28 A and  28 B, respectively. Tip  55  may be configured, for example, as a “pigtail” or in a J-shape to assist with stabilizing blood pump  50  in the heart of a patient. During operation, blood may be drawn into one or more openings of inlet area  54 , channeled through cannula  53 , and expelled through one or more openings of outlet area  56  by a motor (not shown) disposed in motor section  51 . In some implementations, the blood flow inlet and outlet areas may be reversed, such that during operation, blood may be drawn into one or more openings of outlet area  56 , channeled through cannula  53 , and expelled through one or more openings of inlet area  54 . 
     As shown in  FIG.  1   , blood pump  50  may be positioned in a patient’s heart. For example, blood pump  50  may be inserted percutaneously via the femoral artery (not shown) into the aorta  11 , across the aortic valve  15 , and into the left ventricle  16 . The aorta  11  includes the descending aorta  12 , the aortic arch  13 , and the ascending aorta  14 . During operation, blood pump  50  may entrain blood from the left ventricle  16  and expel blood into the ascending aorta  14 . As a result, blood pump  50  performs at least some of the work normally done by the patient’s heart. The hemodynamic effects of blood pump  50  may include, for example, an increase in cardiac output, improvement in coronary blood flow resulting in a decrease in left ventricular end-diastolic pressure (LVEDP), pulmonary capillary wedge pressure (PCWP), myocardial workload, and oxygen consumption. In other implementations, blood pump  50  may, for example, be inserted percutaneously via the axillary artery (not shown) into the aorta  11 , across the aortic valve  15 , and into the left ventricle  16 . In other implementations, blood pump  50  may, for example, be inserted directly into the aorta  11 , across the aortic valve  15 , and into the left ventricle  16 . In other implementations, blood pump  50  may be positioned within the right side of the patient’s heart and support right-sided circulation. 
     Controller  40  monitors and controls blood pump  50 . For example, as noted above, controller  40  may transmit and/or receive signals from sensor heads  30  and  60  through optical fibers  28 A and  28 B, respectively. Controller  40  may also transmit and/or receive additional signals. For example, controller  40  may monitor and control the power (e.g., current and/or voltage) provided to the motor (not shown) disposed in motor section  51  through one or more power-supply lines extending through catheter  20  (e.g., power-supply line  59 A of  FIG.  3   ). As another example, controller  40  may monitor and control a pressure and/or flow rate of a purge fluid delivered to the motor (not shown) disposed in motor section  51  through one or more purge-fluid lines extending through catheter  20  (e.g., purge-fluid line  59 B of  FIG.  3   ) to prevent blood from entering the motor. In some implementations, the purge fluid is a dextrose solution (e.g., 5% dextrose in water with  25  or 50 IU/mL of heparin). Data derived by controller  40  from these signals may be displayed on a display  41 . The data derived by controller  40  may be used by a clinician to monitor a patient and/or adjust the positioning of blood pump  50  within the patient. In some implementations, controller  40  is connected to an external power source (e.g., a battery or an electrical outlet of a power grid). In some implementations, controller  130  comprises an internal power source (e.g., a battery). When electrical power is supplied by means of a battery, a patient may be afforded a greater degree of mobility. 
     Signals from optical sensor heads  30  and  60  may be used by controller  40  to measure ventricular pressure and aortic pressure, respectively. Signals from sensor heads  30  and  60  may also be used by controller  40  to measure the flow of blood through blood pump  50  (e.g., by evaluating the difference between the ventricular and aortic pressures), measure contractility (e.g., the inherent ability of the heart muscle to contract), and/or detect bending of tip  55 . In some implementations, sensor heads  30  and  60  may be micro-electro-mechanical systems (MEMS). Sensor heads  30  and  60  may include a pressure-sensitive membrane separated from the tips of the distal ends of optical fibers  28 A and  28 B, respectively, by a cavity (see, e.g., membrane  32  and cavity  33  of  FIG.  2   ). In some implementations, these components may form a Fabry-Perot cavity. In some implementations, the membrane is a glass membrane (e.g., SiO2) or ceramic membrane (e.g., Si 3 N 4 ). In some implementations, the membrane has an additional coating (e.g., a silicone coating) on a surface facing the surroundings. In other implementations, the membrane has no additional coating on its surface facing the surroundings. 
     As shown in  FIG.  1   , sensor heads  30  and  60  are fixed externally on cannula  53  and pump section  52 , respectively. In some implementations, sensor heads  30  and/or  60  are positioned within a depression provided in the external surface of blood pump  50 . The depression may protect sensor heads  30  and/or  60  from colliding with, for example, a sluice valve or a hemostatic valve when blood pump  50  is being introduced into the patient’s vascular system. In some implementations, sensor heads  30  and/or  60  are positioned by a bulge projecting beyond the periphery of blood pump  50 . Much like the depression provided in some implementations, the bulge may protect sensor heads  30  and  60  from colliding with, for example, a sluice valve or a hemostatic valve when blood pump  50  is being introduced into the patient’s vascular system. In some implementations, the bulge has a U-shape or an O-shape. In some implementations, the bulge may be formed by a bead of bonding agent. In some implementations, the bulge may be welded on or soldered onto the external surface of blood pump  50 . In some implementations, the bulge may form an integral part of blood pump  50 . 
       FIG.  2    illustrates aspects of sensor head  30  in greater detail. However, the following description of sensor head  30  and its associated components is equally applicable to sensor head  60  and its associated components. As shown in  FIG.  2   , optical fiber  28 A extends through a tube  27 . Sensor head  30  is located at the distal end  34  of tube  27 . In some implementations, one or more additional optical fibers may extend through tube  27 . As shown in  FIG.  1   , tube  27  exits catheter  20  at point  22  and is attached to the external surface of blood pump  50  along motor section  51 , pump section  52 , and cannula  53 . In some implementations, tube  27  may encase all or some of the portion of fiber  28 A that extends through catheter  20 . In some implementations, tube  27  may terminate at or near point  22  (e.g., within 5 cm of point  22 ). In some implementations, tube  27  may be formed from a polymer (e.g., polyurethane) and/or a metal alloy (e.g., nitinol). 
     Sensor head  30  includes a housing  31 , which contains a pressure-sensitive membrane  32  separated from the tip of the distal end of optical fiber  28 A by a cavity  33 . In some implementations, membrane  32  is a glass membrane (e.g., SiO2) or a ceramic membrane (e.g., Si 3 N 4 ). As shown, a top surface of membrane  32  is exposed to the surrounding environment, and a bottom surface of membrane  32  is exposed to cavity  33 . In other implementations, a coating (e.g., a silicone coating) may be disposed on the top surface of membrane  32 . During operation, membrane  32  is deformed in dependence on the size of a pressure acting on sensor head  30 . In some implementations, membrane  32  may be aligned orthogonally to a longitudinal axis of blood pump  50  to reduce the noise generated by the operation of blood pump  50 . 
     In some implementations, the tip of the distal end of optical fiber  28 A, membrane  32 , and cavity  33  may form a Fabry-Perot cavity. In such implementations, a first partially reflective mirror may be disposed on the tip of the distal end of optical fiber  28 A, and a second partially reflective mirror may be attached to the bottom surface membrane  32 . During operation, controller  40  may transmit a light beam to sensor head  30  through optical fiber  28 A. As the light beam interacts with the Fabry-Perot cavity, it is partially and multiply reflected by the first and second partially reflective mirrors to produce a plurality of interfering rays. For example, as the light beam contacts the first partially reflective mirror disposed on the tip of the distal end of optical fiber  28 A, it is partially reflected. Furthermore, the portion of the light signal that travels through the first partially reflective mirror is then partially reflected by the second partially reflective mirror attached to the bottom surface of membrane  32 . The plurality of reflected, interfering rays travel back through optical fiber  28 A and may be received by, for example, a photodetector (e.g., a charge coupled device (CCD) or complementary metal oxide semiconductor (CMOS) image sensor) disposed in controller  40 . As membrane  32  moves in response to the pressure acting on sensor head  30 , the interference pattern formed by the plurality of reflected, interfering rays changes. Controller  40  may, for example, derive pressure measurements (e.g., ventricular pressure and/or aortic pressure) from these changing interference patterns. 
     In other implementations, the Fabry-Perot cavity may be formed differently. For example, a glass substrate may be disposed between the tip of the distal end of optical fiber  28 A and cavity  33 . In such implementations, the distal end of optical fiber  28 A may be attached to the glass substate with an adhesive, and the first partially reflective mirror may instead be disposed on a surface of the glass substrate that faces cavity  33 . In other implementations, sensor head  30  may be incorporated into a different type of interferometer. For example, rather than being incorporated into a Fabry-Perot interferometer, sensor head  30  may be incorporated into a Michelson interferometer or a Mach-Zehnder interferometer. In such implementations, sensor head  30  may, for example, include a single mirror attached to the bottom surface membrane  32 , rather than a pair of partially reflective mirrors, as described above. 
       FIG.  3    illustrates aspects of blood pump  50  in greater detail. As shown, a drive shaft  57  protrudes from motor section  51  into pump section  52 . Drive shaft  57  is coupled to an impeller  58 . During operation, the rotation of drive shaft  57  and impeller  58  by the motor (not shown) disposed in motor section  51  causes blood to flow through blood pump  50 . For example, blood may be drawn into one or more openings of inlet area  54 , channeled through cannula  53 , and expelled through one or more openings of outlet area  56 . Alternatively, by, for example, reversing the direction of rotation of drive shaft  57  and impeller  58 , blood may be drawn into one or more openings of outlet area  56 , channeled through cannula  53 , and expelled through one or more openings of inlet area  54 . 
     In addition to optical fibers  28 A and  28 B, a power-supply line  59 A and a purge-fluid line  59 B extend through catheter  20 . Electric power is provided to the motor (not shown) disposed in motor section  51  through power-supply line  59 A. In some implementations, the electric power may be provided by controller  40 . In some implementations, power-supply line  59 A includes a plurality of electrical lines. A purge fluid (e.g., a dextrose solution) is delivered to the motor (not shown) disposed in motor section  51  through purge-fluid line  59 B. 
     As shown in  FIG.  3   , sensor head  30  is positioned distally relative to sensor head  60 , which is positioned more proximally. More specifically, sensor head  30  is attached to an external surface of cannula  53  by inlet area  54 . As explained above, optical fiber  28 A extends through tube  27 , and sensor head  30  is located at the distal end of tube  27 . Furthermore, sensor head  60  is attached to an external surface of pump section  52  by outlet area  56 . Optical fiber  28 B extends through a tube  21 , which is attached to the external surface of blood pump  50  along to motor section  51  and pump section  52 . Sensor head  60  is located at the distal end of tube  21 . Tube  21  may be structured in much the same way as tube  27 . For example, in some implementations, one or more additional optical fibers may extend through tube  21 . As another example, in some implementations, tube  21  may encase all or some of the portion of fiber  28 B that extends through catheter  20 . As yet another example, in some implementations, tube  21  may be formed from a polymer (e.g., polyurethane) and/or a metal alloy (e.g., nitinol). Bulges or protuberances  35  and  65  are provided by sensor heads  30  and  60 , respectively, to protect sensor heads  30  and  60  from colliding with, for example, a sluice valve or a hemostatic valve when blood pump  50  is being introduced into a patient’s vascular system. Additionally, as explained below, sensor heads  30  and  60  may be positioned within depressions in cannula  53  and pump section  52 , respectively, to further protect them. 
     In other implementations, sensor heads  30  and/or  60  may be positioned at different locations. For example, sensor head  30  may be attached to an external surface of tip  55 . In such implementations, tube  27  may be attached to the external surface of blood pump  50  along motor section  51 , pump section  52 , and/or cannula  53 . As another example, sensor head  60  may be attached to an external surface of motor section  51 . In such implementations, tube  21  may only be attached to the external surface of blood pump  50  along motor section  51 , and not pump section  52 . As yet another example, sensor heads  30  and/or  60  may be attached to an external surface of catheter  20 . In such implementations, tubes  21  and/or  27  may be removed from blood pump  50 . In other implementations, sensor heads  30  and/or  60  may be attached to an internal surface of blood pump  50 . For example, sensor head  30  may be attached to an internal surface of cannula  53 . As another example, sensor head  60  may be attached to an internal surface of pump section  52 . Similarly, in other implementations, all or some of tubes  21  and/or  27  may be attached to an internal surface of blood pump  50 . 
       FIGS.  4 A and  4 B  provide cross-sectional and top-down views, respectively, of detail A of  FIG.  3   . As shown, sensor head  60  is positioned in a depression  66  provided on an external surface of pump section  52 . Furthermore, depression  66  is partially surrounded by a U-shaped bulge  65 . In other implementations, bulge  65  may be replaced with an O-shaped bulge. In some implementations, bulge  65  may be formed by a bead of bonding agent. In some implementations, bulge  65  may be welded on or soldered onto the external surface of pump section  52 . In some implementations, bulge  65  may form an integral part of pump section  52 . 
       FIGS.  5 A and  5 B  provide cross-sectional and top-down views, respectively, of detail B of  FIG.  3   . As shown, sensor head  30  is positioned in a depression  36  provided on an external surface of cannula  53 . Furthermore, depression  36  is positioned adjacent to a point-shaped bulge  35 . In other implementations, bulge  35  may be replaced with a U-shaped bulge or an O-shaped bulge. In some implementations, bulge  35  may be formed by a bead of bonding agent. In some implementations, bulge  35  may be welded on or soldered onto the external surface of cannula  53 . In some implementations, bulge  35  may form an integral part of cannula  53 . 
     Various modifications can be made to the ventricular support system of  FIGS.  1  through  5 ( b )  and one or more of its components. For example, the system can be modified to accommodate a variety of different intravascular blood pumps, such as the Impella 2.5®, Impella 5.0®, Impella 5.5®, Impella LD®, Impella RP®, and Impella CP® catheters from Abiomed, Inc., Danvers, MA. As another example, optical sensor heads  30  and/or  60  may be replaced with electrical pressure sensors (e.g., strain-gauge sensors). As yet another example, one or more sensors (e.g., optical and/or electrical sensors) may be added to blood pump  50 . In such implementations, the one or more additional sensors may be used to measure, for example, the pressure within a patient’s femoral artery (e.g., when blood pump  50  is inserted percutaneously via the femoral artery) or axillary artery (e.g., when blood pump  50  is inserted percutaneously via the axillary artery). As yet another example, one or more components of the ventricular support system of  FIGS.  1  through  5 ( b )  may be separated or combined. For example, display  41  may be incorporated into another device in communication with controller  40  (e.g., wirelessly or through one or more electrical lines). As another example, the portions of optical fibers  28 A and  28 B extending through catheter  20  may be combined into a single optical fiber. 
       FIG.  6    illustrates a multi-sensor interferometry system  101 . As shown, system  101  includes a controller  110 , a light source  120 , a beam splitter  130 , a fiber optic splitter  140 , filters  152  and  154 , sensor heads  162  and  164 , and a photodetector  170 . However, system  101  may also include additional components, such as one or more collimating lenses and/or one or more focusing lenses. Controller  110  may include one or more processors, one or more application specific integrated circuits (ASICs), and/or other similar components. Controller  110  may also include a memory medium, such as a hard-drive, memory card, ROM, RAM, DVD, CD-ROM, write-capable, and/or read-only memory, that is capable of storing information. Light source  120  may include one or more incandescent lamps, one or more fluorescent lamps, one or more light-emitting diodes (LEDs), and/or one or more lasers. Light source  120  may, for example, produce white light (e.g., a distribution of wavelengths between approximately 400 nm and 700 nm) or one or more specific colors of light within the visible light spectrum (e.g., a combination of blue light and red light). Beam splitter  130  may, for example, be a plate beam splitter (e.g., a half-silvered mirror) or a cube beam splitter (e.g., a pair of triangular glass prisms that are glued together). Fiber optic splitter  140  may, for example, be a Fused Biconical Taper (FBT) splitter or a Planar Lightwave Circuit (PLC) splitter. Filters  152  and  154  may be short-pass filters, long-pass filters, or band-pass filters. Filters  152  and  154  may, for example, be absorptive filters (e.g., colored glass) or dichroic filters (e.g., coated glass). Sensor heads  162  and  164  may, for example, be structured much like sensor heads  30  and  60 . Photodetector  170  may, for example, be a Charge Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS) image sensor. 
     The components of system  101  may be directly or indirectly coupled together. For example, light source  120  and beam splitter  130  may be directly coupled together. Alternatively, light source  120  and beam splitter  130  may, for example, be coupled together through one or more optical fibers and/or one or more other optically transparent components. As another example, beam splitter  130  and fiber optic splitter  140  may be directly coupled together. Alternatively, beam splitter  130  and fiber optic splitter  140  may, for example, be coupled together through one or more optical fibers and/or one or more other optically transparent components. As yet another example, fiber optic splitter  140  and filters  152  and  154  may be directly coupled together. Alternatively, fiber optic splitter  140  and filters  152  and  154  may, for example, be coupled together through one or more optical fibers and/or one or more other optically transparent components. As yet another example, filters  152  and  154  may be directly coupled to sensor heads  162  and  164 , respectively. Alternatively, filters  152  and  154  and sensor heads  162  and  164  may, for example, be coupled together through one or more optical fibers and/or one or more other optically transparent components. As yet another example, beam splitter  130  and photodetector  170  may be directly coupled together. Alternatively, beam splitter  130  and photodetector  170  may, for example, be coupled together through one or more optical fibers and/or one or more other optically transparent components. 
     The components of system  101  may form a Fabry-Perot interferometer. For example, each of sensor heads  162  and  164  may include a Fabry-Perot cavity having a pressure-sensitive membrane and a pair of partially reflective mirrors. During operation, controller  110  may control light source  120  to transmit a light beam (see arrow A) towards beam splitter  130 . The light beam may be partially reflected by beam splitter  130 . The portion of the light beam that passes through beam splitter  130  (see arrow B) may travel towards fiber optic splitter  140  and be split into two separate light beams (see arrows C and D) by fiber optic splitter  140 . One of those light beams may travel through filter  152  towards sensor head  162  (see arrow E), and the other light beam may travel through filter  154  towards sensor head  164  (see arrow F). As the two light beams interact with the Fabry-Perot cavities of sensor heads  162  and  164 , respectively, they may each be partially and multiply reflected by the pair of partially reflective mirrors to produce a plurality of interfering rays (see arrows G and H). The plurality of reflected, interfering rays may travel through filters  152  and  154  towards fiber optic splitter  140  (see arrows I and J) and be combined by fiber optic splitter  140  (see arrow K). The combined rays may travel towards beam splitter  130  and be partially reflected by beam splitter  130 . The portion of the combined rays that is reflected by beam splitter  130  (see arrow L) may be received by photodetector  170 . As the membranes of sensor heads  162  and  164  move, for example, in response to pressures acting on sensor heads  162  and  164 , the interference pattern formed by the combined rays changes. Collectively, controller  110  and/or photodetector  170  may, for example, derive pressure measurements (e.g., ventricular pressure and/or aortic pressure) from these changing interference patterns. 
     Advantageously, system  101  only includes a single light source (i.e., light source  120 ) for transmitting a light beam to the sensor heads (i.e., sensor heads  162  and  164 ), and a single photodetector (i.e., photodetector  170 ) for receiving the plurality of interfering rays reflected from the sensor heads. Conventional ventricular support systems typically include separate interferometry systems for each sensor head. For example, a conventional implementation of the ventricular support system of  FIGS.  1  through  5 ( b )  would include two light sources and two photodetectors. However, by using the multi-sensor interferometry system of  FIG.  6   , only one light source and one photodetector is necessary. Moreover, by using the multi-sensor interferometry system of  FIG.  6   , only a single set of lenses (e.g., one or more collimating lenses and/or one or more focusing lenses) is necessary. As a result, system  101  can be used to improve the portability of the ventricular support system of  FIGS.  1  through  5 ( b ) . 
     The above-noted advantages are achieved, at least in part, by dividing the spectrum of light produced by light source  120  into two different sub-spectrums that are provided to sensor heads  162  and  164 . As explained above, a portion of the light beam produced by light source  120  travels through beam splitter  130  (see arrow B). Fiber optic splitter  140  divides that light beam into two separate light beams (see arrows C and D). In some implementations, fiber optic splitter  140  may be configured to provide approximately equal splitter ratios. In other implementations, fiber optic splitter  140  may be configured to provide unequal splitter ratios. Filters  152  and  154  filter the two light beams produced by fiber optic splitter  140 . Furthermore, filters  152  and  154  permit different spectrums of light to pass through. For example, filter  152  may be a short-pass filter that permits wavelengths of light below a predetermined threshold (e.g., a value between 500 nm and 600 nm) to pass through, and filter  154  may be a long-pass filter that permits wavelengths of light above a predetermined threshold (e.g., a value between 500 nm and 600 nm) to pass through. As another example, filters  152  and  154  may be band-pass filters. For example, filter  152  may permit blue light to pass through, and filter  154  may permit red light to pass through. In some implementations, filters  152  and  154  may permit different overlapping spectrums of light to pass through. In other implementations, filters  152  and  154  may permit different non-overlapping spectrums of light to pass through. 
     As explained above, photodetector  170  receives a combination of the plurality of interfering rays reflected from sensor heads  162  and  164  (see arrow L). Controller  110  and/or photodetector  170  may digitally process the combined rays to separate the interference patterns created by sensor heads  162  and  164 . For example, photodetector  170  may capture an image of the combined interference patterns, and controller  110  may digitally filter that image to separate the interference patterns created by sensor heads  162  and  164 . For example, if filter  152  is a band-pass filter configured to permit blue light to pass through and if each pixel of the image has red, green, and blue values, controller  110  may set the red and green values of each pixel to zero to obtain the interference pattern created by sensor head  162 . Similarly, if filter  154  is a band-pass filter configured to permit red light to pass through and if each pixel of the image has red, green, and blue values, controller  110  may set the green and blue values of each pixel to zero to obtain the interference pattern created by sensor head  164 . 
     When combined with the ventricular support system of  FIGS.  1  through  5 ( b ) , the components of system  101  may be positioned at a variety of different locations. For example, in some implementations, controller  40  of  FIG.  1    may include controller  110 , light source  120 , beam splitter  130 , fiber optic splitter  140 , filters  152  and  154 , and photodetector  170 , and blood pump  50  of  FIG.  1    may include sensor heads  162  and  164  (e.g., as sensor heads  30  and  60 ). In such implementations, the proximal ends of optical fibers  28 A and  28 B may be coupled to filters  152  and  154 , respectively. As another example, in some implementations, controller  40  of  FIG.  1    may include controller  110 , light source  120 , beam splitter  130 , and photodetector  170 , and blood pump  50  of  FIG.  1    may include fiber optic splitter  140 , filters  152  and  154 , and sensor heads  162  and  164 . In such implementations, a single optical fiber may extend through all or some of catheter  20 . A distal end of the single optical fiber may be attached to fiber optic splitter  140 . In such implementations, fiber optic splitter  140  and filters  152  and  154  may be positioned within the distal end of catheter  20  near point  22  (e.g., within 5 cm of point  22 ). Alternatively, fiber optic splitter  140  and filters  152  and  154  may be positioned on an internal or external surface of motor section  51 , pump section  52 , cannula  53 , and/or tip  55 . As yet another example, in some implementations, one or more separate devices (not shown), at least one of which is communicatively coupled to controller  40  of  FIG.  1   , may include controller  110 , light source  120 , beam splitter  130 , fiber optic splitter  140 , filters  152  and  154 , and photodetector  170 , and blood pump  50  of  FIG.  1    may include sensor heads  162  and  164  (e.g., as sensor heads  30  and  60 ). 
     Various modifications can be made to system  101 . For example, system  101  may include one or more additional sensor heads and corresponding filters. Furthermore, in such implementations, fiber optic splitter  140  may divide the portion of the light beam produced by light source  120  that travels through beam splitter  130  (see arrow B) into three or more separate light beams (rather than just two light beams). In such implementations, the corresponding filters may permit different overlapping or non-overlapping spectrums of light to pass through. For example, a first band-pass filter may be configured to permit blue light to pass through, a second band-pass filter may be configured to permit green light to pass through, and a third band-pass filter may be configured to permit red light to pass through. As more sensor heads are added to system  101  in this manner, the potential benefits (e.g., reduced size and/or power consumption) of incorporating system  101  into a ventricular support system increase. 
     As another example, in some implementations, photodetector  170  may be replaced by a fiber optic splitter, two or more filters, and two or more separate photodetectors. For example, as shown in  FIG.  7   , a multi-sensor interferometry system  102  includes controller  110 , light source  120 , beam splitter  130 , fiber optic splitter  140 , filters  152  and  154 , and sensor heads  166  and  168 , as described above in relation to system  101  of  FIG.  6   . However, photodetector  170  has been replaced with fiber optic splitter  171 , filters  173  and  174 , and photodetectors  175  and  176 . Fiber optic splitter  171  may, for example, be an FBT splitter or a PLC splitter. Filters  173  and  174  may be short-pass filters, long-pass filters, or band-pass filters. Filters  152  and  154  may, for example, be absorptive filters (e.g., colored glass) or dichroic filters (e.g., coated glass). Photodetectors  175  and  176  may, for example, be monochrome CCD or CMOS image sensors. 
     During operation, fiber optic splitter  171  receives a combination of the plurality of interfering rays reflected from sensor heads  162  and  164  (see arrow L) and divides them into two separate light beams (see arrows M and N). In some implementations, fiber optic splitter  171  may be configured to provide approximately equal splitter ratios. In other implementations, fiber optic splitter  171  may be configured to provide unequal splitter ratios. Filters  173  and  174  filter the two light beams produced by fiber optic splitter  171 . Furthermore, filters  173  and  174  permit different spectrums of light to pass through. For example, filter  173  may be a short-pass filter that permits wavelengths of light below a predetermined threshold (e.g., a value between 500 nm and 600 nm) to pass through, and filter  174  may be a long-pass filter that permits wavelengths of light above a predetermined threshold (e.g., a value between 500 nm and 600 nm) to pass through. As another example, filters  173  and  174  may be band-pass filters. For example, filter  173  may permit blue light to pass through, and filter  174  may permit red light to pass through. In some implementations, filters  173  and  174  may permit different overlapping spectrums of light to pass through. In other implementations, filters  173  and  174  may permit different non-overlapping spectrums of light to pass through. Photodetectors  175  and  176  receive the filtered light beams produced by filters  173  and  174 , respectively (see arrows O and P). 
     Advantageously, in relation to system  101 , the configuration of system  102  may reduce some of the signal processing performed by controller  110 . For example, in system  102 , controller does not need to digitally process an image to obtain the separate the interference patterns created by sensor heads  162  and  164 . Instead, controller  110  may, for example, receive an image of the interference pattern created by sensor head  162  from photodetector  175  and separately receive an image of the interference pattern created by sensor head  164  from photodetector  176 . Furthermore, in some implementations, these images may have a higher resolution than the images described above in relation to  FIG.  6   . However, the additional components of system  102  may increase the cost, size and/or power consumption of system  102  in relation to system  101 . 
     In some implementations, systems  101  and/or  102  may be modified to form a different type of interferometer, such as a Michelson interferometer or a Mach-Zehnder interferometer. For example, as shown in  FIG.  8   , a multi-sensor interferometry system  103  includes controller  110 , light source  120 , beam splitter  130 , fiber optic splitter  140 , filters  152  and  154 , and photodetector  170 , as described above in relation to system  101  of  FIG.  6   . However, system  103  also includes a mirror  180  to form a Michelson interferometer. Furthermore, sensor heads  162  and  164  have been replaced with sensor heads  166  and  168 , respectively. Sensor heads  166  and  168  may, for example, be structured much like sensor heads  30  and  60 . However, sensor heads  166  and  168  may include a single mirror attached to the bottom surface of a membrane, rather than a pair of partially reflective mirrors, as described above in relation to sensor heads  162  and  164 . 
     During operation, controller  110  may control light source  120  to transmit a light beam (see arrow A) towards beam splitter  130 . The light beam may be partially reflected by beam splitter  130 . The portion of the light beam that is reflected by beam splitter  130  (see arrow Q) may travel towards mirror  180  and be reflected by mirror  180  back towards beam splitter  130  (see arrow R). A portion of the light beam reflected by mirror  180  may pass through beam splitter  130  and travel towards photodetector  170  (see arrow S). As explained above in relation to  FIG.  6   , the portion of the light beam produced by light source  120  that travels through beam splitter  130  (see arrow B) may travel towards fiber optic splitter  140  and be split into two separate light beams (see arrows C and D). After passing through filters  152  and  154 , those light beams may be reflected by the mirrors of sensor heads  166  and  168  back towards filters  152  and  154  (see arrows G and H). The reflected signals may be combined by fiber optic splitter  140  (see arrow K), partially reflected by beam splitter  130  (see arrow L), and received by photodetector  170 . 
     Collectively, controller  110  and/or photodetector  170  may digitally process the light beams received by photodetector  170  in much the same way described above in relation to  FIG.  6   . However, in the implementation of  FIG.  8   , photodetector  170  receives a reference light beam reflected by mirror  180  (see arrow S) and a combination of the light beams reflected by the mirrors of sensor heads  166  and  168  (see arrow L). Together, these light beams form a combined interference pattern. As the membranes of sensor heads  166  and  168  move, for example, in response to pressures acting on sensor heads  166  and  168 , the interference pattern changes. Collectively, controller  110  and/or photodetector  170  may, for example, derive pressure measurements (e.g., ventricular pressure and/or aortic pressure) from these changing interference patterns. 
     From the foregoing and with reference to the various figure drawings, those skilled in the art will appreciate that certain modifications can also be made to the present disclosure without departing from the scope of the same. While several implementations of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as exemplifications of particular implementations. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.