Methods, systems, and devices for tissue characterization and quantification using intravascular ultrasound signals

1. A method of evaluating at least one tissue type in at least one intravascular ultrasound (IVUS) image, the method comprising:

a) providing a tissue classifier comprising a plurality of detector arrays for each of a plurality of tissue types, wherein each detector array comprises a plurality of detectors and each detector comprises a plurality of tissue type-assigned IVUS spectra, wherein a plurality of the tissue type-assigned IVUS spectra of each detector correspond to a tissue type of the detector and a plurality of the tissue type-assigned IVUS spectra correspond to other tissue types;

b) comparing an input IVUS spectrum of a region in the at least one intravascular ultrasound image to the tissue type-assigned IVUS spectra of each of the plurality of detectors for each of the plurality of detector arrays;

c) determining, for each of the plurality of detectors of each of the plurality of detector arrays, whether the input IVUS spectrum corresponds to the tissue type of the detector based on the comparisons of the input IVUS spectrum to the tissue type-assigned IVUS spectra for that detector;

d) for each of the plurality of detector arrays, combining results of the plurality of detectors of the detector array to produce an array result;

e) combining the array results for the plurality of detector arrays to provide a tissue characterization of the region from the plurality of tissue types;

f) repeating b) to e) for each region to be characterized in the at least one intravascular ultrasound image;

g) determining a size of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion; and

h) displaying one or more of the at least one intravascular ultrasound image with an indication of the tissue characterization of one or more regions of the at least one intravascular ultrasound image that is displayed and an indication of the size of at least one of the tissue types in the selected portion of the at least one intravascular ultrasound image that is displayed.

2. The method of claim 1 , wherein determining the size of at least one of the tissue types comprises determining the size of each of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

3. The method of claim 2 , wherein displaying one or more of the at least one intravascular ultrasound image comprises displaying one or more of the at least one intravascular ultrasound image with an indication of the tissue characterization of one or more regions of the at least one intravascular ultrasound image that is displayed and an indication of the size of each of the tissue types in the selected portion of the at least one intravascular ultrasound image that is displayed.

4. The method of claim 1 , wherein determining the size of at least one of the tissue types comprises determining a relative size of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

5. The method of claim 1 , wherein determining the size of at least one of the tissue types comprises determining an absolute area of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

6. The method of claim 1 , wherein step f) is repeating b) to e) for each region to be characterized in a plurality of intravascular ultrasound images; and

wherein determining the size of at least one of the tissue types comprises determining an absolute volume of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

7. The method of claim 1 , further comprising combining the array results for the plurality of detector arrays to provide a confidence level associated with the tissue characterization for each region characterized in the at least one intravascular ultrasound image.

8. The method of claim 7 , further comprising using the confidence levels associated with the tissue characterization for each region characterized in the at least one intravascular ultrasound image to determine a confidence level in the determined size of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image.

9. The method of claim 1 , wherein displaying one or more of the at least one intravascular ultrasound image with an indication of the tissue characterization of one or more regions of the at least one intravascular ultrasound image comprises coloring each characterized region on the at least one intravascular ultrasound image with a color assigned to a tissue type corresponding to the tissue characterization.

10. The method of claim 9 , further comprising reflecting a confidence level associated with the tissue characterization by-varying a display characteristic of the coloring of each characterized region according to the confidence level.

11. The method of claim 10 , wherein the display characteristic is selected from transparency, brightness, hue, color, shade, and texture.

12. A non-transitory computer-readable medium having processor-executable instructions for characterizing tissue, the processor-executable instructions when installed onto a device enable the device to perform actions, comprising:

a) providing a tissue classifier comprising a plurality of detector arrays for each of a plurality of tissue types, wherein each detector array comprises a plurality of detectors and each detector comprises a plurality of tissue type-assigned IVUS spectra, wherein a plurality of the tissue type-assigned IVUS spectra of each detector correspond to a tissue type of the detector and a plurality of the tissue type-assigned IVUS spectra correspond to other tissue types;

b) comparing an input IVUS spectrum of a region in the at least one intravascular ultrasound image to the tissue type-assigned IVUS spectra of each of the plurality of detectors for each of the plurality of detector arrays;

c) determining, for each of the plurality of detectors of each of the plurality of detector arrays, whether the input IVUS spectrum corresponds to the tissue type of the detector based on the comparisons of the input IVUS spectrum to the tissue type-assigned IVUS spectra for that detector;

d) for each of the plurality of detector arrays, combining results of the plurality of detectors of the detector array to produce an array result;

e) combining the array results for the plurality of detector arrays to provide a tissue characterization of the region from the plurality of tissue types;

f) repeating b) to e) for each region to be characterized in the at least one intravascular ultrasound image;

g) determining a size of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion; and

h) displaying one or more of the at least one intravascular ultrasound image with an indication of the tissue characterization of one or more regions of the at least one intravascular ultrasound image that is displayed and an indication of the size of at least one of the tissue types in the selected portion of the at least one intravascular ultrasound image that is displayed.

13. The computer-readable medium of claim 12 , wherein the actions further comprise reflecting a confidence level associated with the tissue characterization by selecting a display characteristic of the coloring of the tissue region.

14. The computer-readable medium of claim 12 , wherein determining the size of at least one of the tissue types comprises determining the size of each of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

15. The computer-readable medium of claim 12 , wherein determining the size of at least one of the tissue types comprises determining a relative size of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

16. The computer-readable medium of claim 12 , wherein determining the size of at least one of the tissue types comprises determining an absolute area of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

17. The computer-readable medium of claim 12 , wherein instruction f) is repeating b) to e) for each region to be characterized in a plurality of intravascular ultrasound images; and

wherein determining the size of at least one of the tissue types comprises determining an absolute volume of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

18. A tissue classifier, comprising

a plurality of detector arrays for each of a plurality of tissue types, wherein each detector array comprises a plurality of detectors and each detector comprises a plurality of tissue type-assigned intravascular ultrasound (IVUS) spectra, wherein a plurality of the tissue type-assigned IVUS spectra of each detector correspond to a tissue type of the detector and a plurality of the tissue type-assigned IVUS spectra correspond to other tissue types; and

a processor configured to execute processor-readable instructions that enable actions, including:

a) comparing an input IVUS spectrum of a region in the at least one intravascular ultrasound image to the tissue type-assigned IVUS spectra of each of the plurality of detectors for each of the plurality of detector arrays;

b) determining, for each of the plurality of detectors of each of the plurality of detector arrays, whether the input IVUS spectrum corresponds to the tissue type of the detector based on the comparisons of the input IVUS spectrum to the tissue type-assigned IVUS spectra for that detector;

c) for each of the plurality of detector arrays, combining results of the plurality of detectors of the detector array to produce an array result;

d) combining the array results for the plurality of detector arrays to provide a tissue characterization of the region from the plurality of tissue types;

e) repeating a) to d) for each region to be characterized in the at least one intravascular ultrasound image; and

f) determining a size of at least one of the tissue types in a selected portion of the at least one intravascular ultrasound image using the tissue characterizations of the regions in the selected portion.

19. The tissue classifier of claim 18 , wherein the actions further comprise displaying one or more of the at least one intravascular ultrasound image with an indication of the tissue characterization of one or more regions of the at least one intravascular ultrasound image that is displayed and an indication of the size of at least one of the tissue types in the selected portion of the at least one intravascular ultrasound image that is displayed.

20. An imaging device, comprising:

a catheter configured and arranged for insertion into a patient;

a transducer disposed on the catheter and configured and arranged to produce ultrasound signals and receive backscattered signals;

a processor coupled to the transducer and configured and arranged to receive the backscattered signals from the transducer and to generate from the backscattered signals an image; and

the tissue classifier of claim 18 .

21. The imaging device of claim 20 , wherein the processor coupled to the transducer is also the processor of the tissue classifier.

22. The imaging device of claim 20 , further comprising a display configured and arranged to display the image from the processor coupled to the transducer and to display the tissue characterization of the tissue classifier and the indication of the size of at least one of the tissue types in the selected portion of the at least one intravascular ultrasound image that is displayed.