Hybrid image-invasive-pressure hemodynamic function assessment

Abstract

There is described a method for calculating a patient-specific hemodynamic parameter. The method comprises measuring at least one pressure measurement in an artery using an intravascular pressure measurement device, and taking at least one medical image of the artery from a medical imaging instrument, the at least one medical image of the artery being synchronous with the at least one pressure measurement. Both the pressure measurement and the medical image are fed to a computing system to calculate a flow from the at least one medical image, to calculate parameters of the artery from at least two artery pressure drops and corresponding flow components, and based on the flow and the parameters of the artery, to calculate a patient-specific hemodynamic parameter or a plurality thereof.

1 . A method executable by a computing system comprising a processor in communication with an intravascular pressure measurement device and with a medical imaging instrument, the method comprising:
 introducing a radiation-absorbing contrast medium in the artery;   taking, with the medical imaging instrument, at least one medical image of the artery during propagation of the radiation-absorbing contrast medium in the artery;   feeding the at least one medical image to the computing system;   measuring, by the computing system, in the at least one medical image, a diameter D of the artery which varies along a length x of the artery;   tracking a propagation of the radiation-absorbing contrast medium in the artery and measuring a time taken for a propagation between a first point L 1  to a second point L 2  in the artery,   calculating, by the processor, a flow from the at least one medical image, by determining a volume of the artery based on a distance between the first point L 1  and the second point L 2  in the artery and based on the diameter D of the artery.   
     
     
         2 . The method of  claim 1 , wherein calculating the flow further comprises dividing the volume of the artery by the time taken for the contrast agent to propagate between the first point L 1  and the second point L 2  in the artery. 
     
     
         3 . The method of  claim 1 , wherein the volume is calculated as: 
       
         
           
             
               
                 V 
                 = 
                 
                   
                     
                       ( 
                       
                         
                           L 
                           2 
                         
                         - 
                         
                           L 
                           1 
                         
                       
                       ) 
                     
                     4 
                   
                   · 
                   
                     
                       ∫ 
                       
                         L 
                         ⁢ 
                         1 
                       
                       
                         L 
                         ⁢ 
                         2 
                       
                     
                     ⁢ 
                     
                       
                         
                           π 
                           ⁡ 
                           
                             ( 
                             
                               D 
                               ⁡ 
                               
                                 ( 
                                 x 
                                 ) 
                               
                             
                             ) 
                           
                         
                         2 
                       
                       ⁢ 
                       d 
                       ⁢ 
                       x 
                     
                   
                 
               
               , 
             
           
         
       
     
     
         4 . The method of  claim 1 , wherein measuring, in the at least one medical image defining a plane, the diameter D of the artery which is perpendicular to the plane of the at least one medical image comprises using densitometry on the radiation-absorbing contrast medium to measure D as a function of x by applying Beer-Lambert's law on a measured intensity in a section of the artery. 
     
     
         5 . The method of  claim 4 , wherein using densitometry on the radiation-absorbing contrast medium comprises determining a depth th of artery perpendicular to the plane of the at least one medical image: 
       
         
           
             
               
                 th 
                 = 
                 
                   
                     
                       ln 
                       ⁡ 
                       
                         ( 
                         
                           I 
                           i 
                         
                         ) 
                       
                     
                     - 
                     
                       ln 
                       ⁡ 
                       
                         ( 
                         
                           I 
                           T 
                         
                         ) 
                       
                     
                   
                   α 
                 
               
               , 
             
           
         
         where I i  is the incident radiation intensity, I T  is the transmitted radiation intensity, and α is a constant that corresponds to the contrast agent absorbing coefficient. 
       
     
     
         6 . A system comprising:
 a computing system in communication with an intravascular pressure measurement device and with a medical imaging instrument, the computing system comprising a memory for storing instructions and data from both the intravascular pressure measurement device and the medical imaging instrument, and a processor which executes the instructions to:
 receive at least one pressure measurement from the intravascular pressure measurement device in an artery; 
 receive at least one aortic pressure from another pressure device; 
 receive at least one medical image of the artery from the medical imaging instrument; 
 calculate a flow from the at least one medical image; 
 calculate parameters of the artery from at least two artery pressure drops and corresponding flow components; and 
 based on the flow and the parameters of the artery, calculate a patient-specific hemodynamic parameter. 
   
     
     
         7 . The system of  claim 6 , wherein the intravascular pressure measurement device is a pressure guidewire. 
     
     
         8 . The system of  claim 6 , further comprising the intravascular pressure measurement device configured to measure the at least one pressure measurement simultaneously with the at least one medical image being acquired in real time. 
     
     
         9 . The system of  claim 6 , wherein each of the at least one pressure measurement has a corresponding synchronous medical image of the artery. 
     
     
         10 . The system of  claim 6 , wherein the processor is further configured to:
 measure, in the at least one medical image, a diameter D of the artery which varies along a length x of the artery;   track a propagation of a radiation-absorbing contrast medium in the artery and measure a time taken for a propagation between a first point L 1  to a second point L 2  in the artery,   wherein calculating the flow comprises dividing a volume V by the time taken for the propagation to calculate a mean blood flow in the artery.   
     
     
         11 . The system of  claim 10 , wherein the volume V is determined as: 
       
         
           
             
               V 
               = 
               
                 
                   
                     ( 
                     
                       
                         L 
                         2 
                       
                       - 
                       
                         L 
                         1 
                       
                     
                     ) 
                   
                   4 
                 
                 · 
                 
                   
                     ∫ 
                     
                       L 
                       ⁢ 
                       1 
                     
                     
                       L 
                       ⁢ 
                       2 
                     
                   
                   ⁢ 
                   
                     
                       
                         π 
                         ⁡ 
                         
                           ( 
                           
                             D 
                             ⁡ 
                             
                               ( 
                               x 
                               ) 
                             
                           
                           ) 
                         
                       
                       2 
                     
                     ⁢ 
                     
                       dx 
                       . 
                     
                   
                 
               
             
           
         
       
     
     
         12 . The system of  claim 10 , wherein the processor, when measuring, in the at least one medical image defining a plane, the diameter D of the artery which is perpendicular to the plane of the at least one medical image is further configured to use densitometry on the radiation-absorbing contrast medium to measure D as a function of x by applying Beer-Lambert's law on a measured intensity in a section of the artery. 
     
     
         13 . The system of  claim 6 , wherein the processor is further configured to:
 calculate the flow associated to a hyperemic condition using the parameters of the artery, wherein calculating the patient-specific hemodynamic parameter is based on a pressure drop and the calculated flow associated to the hyperemic condition, the hyperemic condition being induced using an intracoronary or intravenous injection of a hyperemic agent in the artery.   
     
     
         14 . The system of  claim 6 , wherein the patient-specific hemodynamic parameter comprises a microvascular resistance. 
     
     
         15 . The system of  claim 6 , wherein the patient-specific hemodynamic parameter comprises a coronary flow reserve (CFR). 
     
     
         16 . The system of  claim 6 , wherein the at least one pressure measurement and the at least one medical image are measured in a resting condition, first during a systole period which covers at least a portion of a systole, and second during a diastole period which covers at least a portion of the diastole, and wherein the processor is further configured to calculate parameters of the artery by solving a second-degree equation of the parameters of the artery using the at least two artery pressure drops and corresponding flow components which are respectively measured and calculated in the systole period and in the diastole period.