Fluorescence based flow imaging and measurements

Abstract

Fluorescence based tracking of a light-emitting marker in a bodily fluid stream is conducted by: providing a light-emitting marker into a fluid stream; establishing field of view monitoring by placement of a sensor, such as a high speed camera, at a region of interest; recording image data of light emitted by the marker at the region of interest; determining time characteristics of the light output of the marker traversing the field of view; and calculating flow characteristics based on the time characteristics. Furthermore generating a velocity vector map may be conducted using a cross correlation technique, leading and falling edge considerations, subtraction, and/or thresholding.

What is claimed is: 
     
         1 . A system for fluorescence based tracking of a light-emitting marker in a bodily fluid stream, the system comprising:
 a delivery apparatus configured to provide a light-emitting marker into the bodily fluid stream;   a camera configured to monitor a region of interest traversed by the bodily fluid stream; and   a computing device configured to:
 record motion video data generated by the camera; 
 determine time characteristics of the recorded data; and 
 calculate flow characteristics based on the time characteristics. 
   
     
     
         2 . The system according to  claim 1 , wherein the computing device is further configured to:
 divide the motion video data into kernels;   identify which of the kernels receive some portion of the light-emitting marker using an intensity threshold;   compute, for each identified kernel, an intensity signal data set comprising information of mean light intensity versus time;   perform smoothing on each intensity signal data set; and   calculate a lag time between the intensity signal data sets of neighboring identified kernels using cross-correlation.   
     
     
         3 . The system according to  claim 1 , wherein the computing device is further configured to:
 using a spatial resolution and the lag time, calculate velocity vectors;   sum the velocity vectors of neighboring kernels to create a resultant velocity vector; and   generate a velocity map from the resultant velocity vectors for all kernels.   
     
     
         4 . The system according to  claim 3 , wherein the computing device performs smoothing on each intensity signal data set by time window averaging or by using a filter. 
     
     
         5 . The system according to  claim 3 , wherein the computing device is further configured to:
 for each particular identified kernel, find segments in which a slope of the intensity signal data set rises for a minimum consecutive number of frames or falls for a minimum consecutive number of frames, which segments occur when a leading edge or falling edge of a portion of the light-emitting marker passes through the identified kernel;   search the intensity signal data sets of neighboring identified kernels for a rising or falling segment of similar length; and   calculate a lag time between segments in the particular identified kernel and segments in the neighboring identified kernels.   
     
     
         6 . The system according to  claim 3 , wherein the computing device is further configured to:
 calculate a difference frame by subtracting a frame of the motion video data from a consecutive frame of the motion video data;   apply a threshold to the difference frame to eliminate pixels therein below a specified intensity value;   calculate a pixel size of a remaining blob in the difference frame in a direction of bodily fluid flow;   calculate a size of the remaining blob using the pixel size and a spatial resolution; and   calculate a velocity by using a distance traveled by the remaining blob and a time between frames.   
     
     
         7 . The system according to  claim 3 , wherein the computing device is further configured to:
 create a logical frame in which a respective indicator for each pixel can be set as true or false;   set the indicators of the identified pixels as true;   set the indicators of all other pixels as false;   calculate a difference frame by subtracting a first logical frame from a second logical frame such that the difference frame comprises pixels that reached the specified threshold after a time of the first logical frame;   find length in pixels of the remaining blob in the difference frame in a direction of bodily fluid flow;   convert the length in pixels of the difference frame to physical distance using the spatial resolution; and   calculate velocity by dividing the physical distance by a time between frames.   
     
     
         8 . A method of fluorescence based tracking of a light-emitting marker in a fluid stream, the method comprising:
 monitoring, with a camera, a region of interest traversed by fluid stream into which a light-emitting marker has been introduced;   recording motion video data generated by the sensor;   dividing the motion video data into frames each comprising pixels;   identifying which of the pixels receive some portion of the light-emitting marker using an intensity threshold;   calculating a difference frame by subtracting a frame of the motion video data from a consecutive frame of the motion video data; and   applying a threshold to the difference frame to eliminate pixels therein below a specified intensity value.   
     
     
         9 . The method according to  claim 8 , further comprising:
 calculating a pixel size of a remaining blob in the difference frame in a direction of fluid flow;   calculating a size of the remaining blob using the pixel size and a spatial resolution; and   calculating a velocity by using a distance traveled by the remaining blob and a time between frames.   
     
     
         10 . The method according to  claim 9 , further comprising:
 creating a logical frame in which a respective indicator for each pixel can be set as true or false;   setting the indicators of the identified pixels as true;   setting the indicators of all other pixels as false;   calculating a difference frame by subtracting a first logical frame from a second logical frame such that the difference frame comprises pixels that reached the specified threshold after a time of the first logical frame;   finding length in pixels of a remaining blob in the difference frame in a direction of fluid flow;   converting the length in pixels of the difference frame to physical distance using the spatial resolution; and   calculating velocity by dividing the physical distance by a time between frames.