Optical coherence tomography and pressure based systems and methods

Abstract

In part, the invention relates to methods, apparatus, and systems suitable for determining a fractional flow reserve (FFR) and variations of modifications thereof One embodiment relates to a method and apparatus for obtaining a corrected FFR in a vessel having a stenosis. In one aspect, the invention relates to an apparatus for measuring corrected FFR of a vessel having a stenosis. In one embodiment, the apparatus includes a probe comprising an optical coherence tomography assembly and a pressure assembly; and a processor in communication with the optical coherence tomography assembly and the pressure assembly. In one embodiment, the pressure assembly measures values of pressure in predetermined locations the vessel and communicates them to the processor. In one embodiment, a dual guidewire is used to reduce the interference in the pressure measurement.

1 . A data collection system comprising:
 a pressure assembly configured to measure pressure at one or more predetermined locations in a vessel, and   an optical coherence tomography assembly configured to measure a geometry of the vessel at one or more of the predetermined locations within the vessel.   
     
     
         2 . The system of  claim 1  further comprising a probe, wherein the optical coherence tomography assembly is disposed in the probe. 
     
     
         3 . The system of  claim 2  wherein the optical coherence tomography assembly comprises an optical fiber, wherein the probe further comprises
 a first torque wire having a first diameter and defining a first lumen and 
 a second torque wire having a second diameter and defining a second lumen, 
 wherein the first and second torque wires are joined, and 
 wherein the optical fiber passes through the first lumen and the second lumen. 
 
     
     
         4 . The system of  claim 1  further comprising a probe, wherein the optical coherence tomography assembly is disposed in the probe, the optical coherence tomography assembly comprises
 an optical fiber configured to transmit light of a first wavelength band and a second wavelength band; and 
 a beam director adjacent to and coaxial with the optical fiber, the beam director configured to reflect light of the first wavelength band, wherein the pressure assembly comprises 
 an optical pressure transducer, coaxial with the beam director and the optical fiber, and positioned distal to the beam director, the optical pressure transducer configured to modulate light of the second wavelength band. 
 
     
     
         5 . The system of  claim 2  further comprising a processor in communication with the optical coherence tomography assembly and the pressure assembly, the processor configured to execute a program to calculate a corrected fractional flow reserve for the vessel in response to the geometry at one or more of the predetermined locations within the vessel and the pressure measured at one or more predetermined locations in the vessel. 
     
     
         6 . The system of  claim 5  wherein the processor is configured to execute the program to correct an initial fractional flow reserve using hydrodynamic equations and the geometry of the vessel measured with the optical coherence tomography assembly. 
     
     
         7 . The system of  claim 5  wherein the processor is configured to execute the program to output a myocardial damage index as a ratio of a measured pressure drop to an expected pressure drop. 
     
     
         8 . The system of  claim 2  further comprising a purge assembly comprising a fluid restricting device and a purge fluid supply, the fluid restricting device in fluid communication with a purge port defined by a wall of the probe. 
     
     
         9 . The system of  claim 8  wherein the fluid restricting device is adjustable and comprises a biasing element and a slidable member defining a hole, the hole positioned to received purge fluid from the purge fluid supply and the biasing element configured to apply a biasing force upon the slidable member. 
     
     
         10 . The system of  claim 4  wherein an air filled cavity is defined between the pressure transducer and the beam director. 
     
     
         11 . The system of  claim 2  further comprising:
 a wall of the probe; and 
 a lumen defined by the wall, 
 wherein the optical coherence tomography assembly comprises a rotatable optical fiber disposed within the lumen and wherein the pressure assembly comprises a pressure transducer disposed within a pocket disposed in the wall. 
 
     
     
         12 . The system of  claim 11  wherein the pressure transducer is separated from the lumen by a gel positioned within the pocket. 
     
     
         13 . The system of  claim 2  further comprising
 a fluid supply configured to deliver a purge solution; 
 a check valve in fluid communication with the fluid supply; 
 a fluid flow control device in fluid communication with the check valve; and 
 a fluid delivery channel configured to transport the purge solution to a purge port defined by a wall of the probe. 
 
     
     
         14 . The system of  claim 13  wherein the fluid control device is selected from the group consisting of a restriction, an adjustable restriction, an expandable tube, and an expandable tube disposed in an expansion limiter. 
     
     
         15 . The system of  claim 3  wherein the length of the first diameter is about ten times the length of the second diameter. 
     
     
         16 . The system of  claim 3  wherein the first torque wire abuts the second torque wire and the first and the second torque wires are located within and held together by a tube heat shrunk around the first and second torque wires. 
     
     
         17 . The system of  claim 2  wherein the probe comprises a catheter having a wall defining a lumen, and a purge port and further comprising
 a fluid supply; and 
 a three way valve having a first port in communication with the lumen, a second port in communication with the fluid supply and a third port in communication with the pressure assembly, wherein the pressure assembly is a pressure transducer, wherein when in the first position the valve connects the fluid supply with the lumen, and wherein when in the second position the valve connects the lumen and the pressure transducer. 
 
     
     
         18 . A processor-based method of determining one or more parameters of a vessel based on measured optical data and measured pressure data comprising:
 measuring a pressure value at one or more predetermined locations in the vessel using a pressure assembly;   determining a geometric boundary of the vessel at the one or more predetermined locations using an optical coherence tomography assembly; and   determining, using a processor, a fractional flow reserve of the vessel in response to the geometric boundary measured at the one or more predetermined locations within the vessel and the measured pressure value at the one or more predetermined locations in the vessel.   
     
     
         19 . The method of  claim 18  wherein the step of determining the geometric boundary of the vessel comprises the step of estimating a portion of the geometric boundary of the vessel hidden from optical coherence tomography by a guidewire. 
     
     
         20 . The method of  claim 18  further comprising the step of iteratively obtaining the fractional flow reserve such that one or more corrections are made to reduce errors associated with using the pressure measuring assembly and the optical coherence tomography assembly in the vessel. 
     
     
         21 . The method of  claim 18  further comprising the step of determining an initial fractional flow reserve by dividing a first pressure measured distal to a stenosis by a second pressure measured in an ostium. 
     
     
         22 . The method of  claim 21  wherein the processor further determines the fractional flow reserve by correcting the initial fractional flow reserve using three dimensional hydrodynamic equations and the geometric boundary of the vessel measured with the optical coherence tomography assembly. 
     
     
         23 . The method of  claim 18  wherein the step of determining, using a processor, a fractional flow reserve further comprises
 determining, using a processor, a first fractional flow reserve in the vessel; 
 correcting, using the processor, errors introduced by a first probe obstructing the vessel to determine a first corrected fractional flow reserve; 
 determining, using the processor, a second fractional flow reserve in the vessel; 
 correcting, using the processor, errors introduced by an obstruction in the vessel to determine a second corrected fractional flow reserve; and 
 comparing the first corrected fractional flow reserve and the second corrected fractional flow reserve. 
 
     
     
         24 . The method of  claim 23  wherein the obstruction is the first probe, a second probe, a stenosis or a stent. 
     
     
         25 . The method of  claim 23  further comprising the step of outputting a damage index in response to the step of comparing. 
     
     
         26 . The method of  claim 23  wherein the pressure assembly and the optical coherence tomography assembly are disposed in the first probe. 
     
     
         27 . The method of  claim 18  wherein the pressure assembly is a pressure transducer in fluid communication with a purge port of a catheter disposed in the vessel and wherein the pressure value is measured at a predetermined location near the purge port.