METHODS AND APPARATUSES FOR MEDICAL IMAGING

• US 20080051660A1
• Filed: 08/03/2007
• Published: 02/28/2008
• Est. Priority Date: 01/16/2004
• Status: Abandoned Application

• Current Assignee: University of Houston System
• Original Assignee: University of Houston System
• Inventors: O'Malley, Sean, Kakadaris, Ioannis, Naghavi, Morteza
• Application Number:
  US11/833,759
• Publication Number:
  US 20080051660A1
• Time in Patent Office: Days
• US Class Current: 600/454
• CPC Class Codes: A61B 8/06 Measuring blood flow measuring volume flow in general G01F, e.g. G01F1/66, G01F1/72; measuring speed of fluids in general G01P5/00
• CPC Class Codes: A61B 8/0833 involving detecting or locating foreign bodies or organic structures
• CPC Class Codes: A61B 8/12 in body cavities or body tracts, e.g. by using catheters catheters per se A61M25/00
• CPC Class Codes: A61B 8/469 for selection of a region of interest
• CPC Class Codes: A61B 8/481 involving the use of contrast agent, e.g. microbubbles introduced into the bloodstream analysis of echo signal exploiting properties of a contrast enhancer in devices for short-range imaging with acoustic waves G01S7/52039
• CPC Class Codes: A61B 8/488 involving Doppler signals
• CPC Class Codes: A61B 8/543 involving acquisition triggered by a physiological signal
• CPC Class Codes: G01S 15/8979 Combined Doppler and pulse-echo imaging systems
• CPC Class Codes: G01S 7/52066 Time-position or time-motion displays
• CPC Class Codes: G01S 7/52071 Multicolour displays; using colour coding; Optimising colour or information content in displays, e.g. parametric imaging
• CPC Class Codes: G06V 10/431 Frequency domain transformation; Autocorrelation

Abstract

A set of intravascular ultrasound (IVUS) related systems, apparatuses and methods are disclosed. New catheter designs including contrast agent introduction subsystems and/or Doppler subsystems are disclosed. Methods for acquiring and analyzing Doppler data from intravascular ultrasound (IVUS) catheters are disclosed. RF-based detection of blood and/or contrast agents such as micro-bubbles are disclosed. Methods for frame-grating image data analysis permitting frame registration before, during and after a contrasting effect is imposed on a system being imaged are disclosed. Methods for difference imaging for contrast detection are disclosed. Methods for quantification and visualization of IVUS data are disclosed. And methods for IVUS imaging are disclosed.

Claims

1. A catheter apparatus comprising:

a nozzle system having exit holes around its periphery adapted to direct jets of an agent through the holes near, immediately proximate or immediately adjacent a portion of a vessel wall of a vessel to be imaged,

a conduit connecting the nozzle system to an external or internal agent reservoir,

at least one electronic flow controller and/or injector adapted to control a flow of the agent from the reservoir through the conduit to the nozzle system out of the holes, and

a digital or analog processing unit adapted to control the controllers.

2. The apparatus of claim 1, further comprising:

an intravascular ultrasound (IVUS) probe connected to an IVUS imaging unit, and

an IVUS digital or analog processing unit adapted to receive and analyze IVUS data before, during and/or after agent injection.

3. The apparatus of claim 1, further comprising:

at least one Doppler element adapted to collect Doppler data connected to a Doppler imaging unit, and

a Doppler digital or analog processing unit adapted to receive and analyze Doppler data before, during and/or after agent injection.

4. A method comprising the steps of:

positioning a probe adjacent a portion of a vessel, where the probe includes an intravascular ultrasound (IVUS) component and a Doppler component,

transmitting a plurality of imaging pulses from the IVUS component into an region-of-interest (ROI),

receiving echoes from the ROI by the IVUS component,

matching or correlating the echoes to the image pulses to estimate a radial position of the stationary probe in the image,

while maintaining the probe in a stationary orientation, switching to pulsed Doppler component;

detecting Doppler signals evidencing flow within the ROI where a suspected plaque, microvascularization or vasa vasorum site is located.

5. A radio-frequency (RF) detection, analysis and quantification method for IVUS comprising the steps of

obtaining RF-based IVUS data with or without an external contrast agent, and

analyzing the RF-based IVUS data to determine features of the vessel.

6. The method of claim 5, wherein the obtaining step comprises:

positioning an IVUS catheter at a maximally-stenotic point of a suspect plaque; and

recording RF data, while the IVUS catheter held stationary in the vessel.

7. The method of claim 6, wherein blood acts as the contrast agent and data is collected for a number of cardiac cycles.

8. The method of claim 6, wherein the obtaining step further comprises:

introducing a contrast agent, and

recording RF data before, during, and after contrast agent introduction.

9. The method of claim 5, wherein the obtaining step comprises:

positioning an IVUS catheter at a maximally-stenotic point of a suspect plaque; and

recording RF data as the catheter is being pulled back.

10. The method of claim 9, wherein the obtaining step further comprises:

introducing a contrast agent, and

recording RF data before, during, and after contrast agent introduction as the catheter is being pulled back.

11. A method implemented on a computer for detecting and analysis RF IVUS blood/saline/contrast agent data comprising the steps of:

training an algorithm to produce a optimal feature classifier including the steps of;

obtaining RF IVUS data including a plurality of frames from an appropriate region of interest (ROI) of a vessel, where the ROI evidences the presence of blood, saline and/or contrast agent,

computing a number of features of the ROI,

computing which features result in a best classification for a given classifier,

selecting the given classifier, and

optimizing parameters of the given classifier to produce the optimal feature classifier, and

deploying the algorithm including the steps of;

using the optimal feature classifier to classify the RF IVUS data.

12. A method for frame gating comprising the steps of:

obtaining a sequence of frames representing a time period from a first time t₁ to a second time t₂;

selecting a frame similarity or dissimilarity metric,

generating a frame dissimilarity matrix,

generating a frame-similarity space by applying the metric to the dissimilarity matrix,

generating clusters in the space using a clustering function, and

selecting a particular frame ensemble from the resulting clusters.

13. A method for pullback frame gating comprising the steps of:

obtaining a pullback sequence of frames representing a time period from a first time t₁ to a second time t₂;

selecting a frame similarity or dissimilarity metric,

generating a dissimilarity matrix,

obtaining an initial estimate of a heartrate over the entire recording,

tracing a path along an off-diagonal valley which represents a cardiac cycle length locally at each frame,

applying zn x-shaped filter to find frame pairs associated with both high similarity and low motion,

finding a single-phase associated pair that is at a maximally-stable point in the cardiac cycle, and

using this point for tracing the filtered dissimilarity matrix upward and downward to collect the frames for the gated sequence.

14. A difference imaging-based detection method comprising the steps of:

positioning a catheter at a maximally-stenotic point of a suspect plaque or a region of interest (ROI);

imaging the ROI for a first period of time, generally on the order of 30 seconds, while holding the catheter steadily in place;

injecting a bolus dose of a contrast agent or contrast effect intra-coronarily, proximate the imaging catheter;

imaging the ROI for a second period of time, generally on the order of 30 seconds, again while holding the catheter steadily in place;

image-based frame gating the data to decimate a number of frames in the sequence of image frame collected in steps 2 and 4, providing a stabilized gated sequence with fewer frames than the original;

outlining an inner and outer contours of the ROI in the first frame of the gated sequence, performed either by an operator or an outlining routine;

propagating these contours to the remaining frames in the sequence, in order to provide a segmentation of each frame;

extracting a region between the contours into a rectangular raster in each frame, providing a stabilized space in which inter-frame comparisons of the ROI are to be performed;

averaging a pre-injection ROI images to obtain a pre-injection baseline of the non-contrast ROI;

subtracting the averaged baseline ROI pixel-wise from the pre- and post-injection ROI images to detect differences between the baseline appearance and the pre- and post-contrast appearance, where the pre-injection frames will rarely exhibit any changes as the pre-injection baseline is derived from them; and

mapping the difference-imaged ROIs back into the original IVUS space for visualization and quantification of the changes which occurred due to contrast perfusion.

15. A method comprising the steps of:

performing an intravascular ultrasound (IVUS) pullback analysis of a vessel,

performing optionally pullback frame gating, analyzing each frame in the original or gated sequence for detection and qualification of VV

dividing each image into four (4) quadrants constructing a map of the VV densities in each quadrant, and

visualizing the VV densities associated with the pullback sequence of IVUS images.

16. A clinical method comprising the steps of:

positioning an IVUS imaging catheter in a vessel,

after positioning, pulling back the catheter until a region-of-interest (ROI) segment of the vessel and a reference segment of the vessel are identified.

after identifying the ROI segment and reference segment, re-positioning the catheter adjacent the ROI segment,

collecting ROI images at a first frame collection rate for a first period of time,

repositioning the catheter adjacent the reference segment,

collecting reference images at a second frame collection rate for a second period of time, introducing a contrast agent,

a collecting contrast reference images at a third frame collection rate for a third period of time,

re-positioning the catheter adjacent the ROI segment,

collecting contrast ROI images at a fourth frame collection rate for a fourth period of time,

optionally while collecting images, exciting the contrast agent transthoracically during all or some of the third and/or fourth image collection period,

administering adenosine,

collecting adenosine ROI images at a fifth frame collection rate for a fifth period of time,

removing the catheter is then removed, and

analyzing the images to assess the presence of plaques and/or vasa vasorum (VV) within the ROI segment.