Statistical mapping in an optoacoustic imaging system

Patent metadata

Field	Value
Publication number	US-9330452-B2
Application number	US-201313793808-A
Country	US
Kind code	B2
Filing date	Mar 11, 2013
Priority date	Mar 9, 2012
Publication date	May 3, 2016
Grant date	May 3, 2016

Abstract

Electromagnetic energy is deposited into a volume, an acoustic return signal from energy deposited in the volume is measured, and a parametric map that estimates values of at least one parameter as spatially represented in the volume is computed. A reference level of a region of interest is determined, and upper and lower color map limits are specified, with at least one of them being determined in relation to the reference level. The parametric map is then rendered in the palette of a color map by mapping the estimated values of the parametric map onto the color map according to the color map limits. Two wavelengths of energy can be applied to the volume, and the parametric map computation can be adapted by applying an implicit or explicit model of, or theoretical basis for, distribution of electromagnetic energy fluence within the volume pertaining to the two wavelengths. The actual electromagnetic energy fluence caused by each wavelength has a propensity, due to variability within the volume, to differ from the modeled or theoretical electromagnetic energy fluence.

First claim

What is claimed is:

1. A method to produce a qualitative image, comprising:
depositing electromagnetic energy into a volume, where a spatial profile of the deposited energy is subject to variability;
measuring acoustic return signals from energy deposited in the volume;
computing a parametric map comprising estimated values of at least one parameter as spatially represented in the volume;
producing a mapping configuration to adjust for effects resulting from at least some of the variability in the spatial profile of the deposited energy by:
i) determining at least one reference level within at least one region of interest of the parametric map, the step of determining at least one reference level comprising using a particular mathematical characteristic of the values of the parametric map within the at least one region of interest; and
ii) specifying an upper color map limit and a lower color map limit, the upper color map limit and the lower color map limit being determined in relation to the at least one reference level, wherein the upper color limit is the reference level plus a first constant times a scalar result of a statistical function applied to the values of the parametric map within the at least one region of interest, and the lower color limit is the reference level minus a second constant times the scalar result of the statistical function applied to the at least one region of interest; and,

rendering the parametric map in the palette of a color map by mapping the estimated values of the parametric map onto the color map according to the upper and lower color map limits of the mapping configuration to produce a rendered parametric map.

2. The method of claim 1 , in which the color map consists of at least one channel and the mapping step comprises mapping numerical values of the parametric map onto each channel of the color map according to interpolating between the upper and lower color map limits.

3. The method of claim 1 , in which the particular mathematical characteristic for determining the reference level is the mean of numerical values of pixels within the region of interest.

4. The method of claim 1 , in which the particular mathematical characteristic for determining the reference level is a statistical function.

5. The method of claim 1 , further comprising a step of masking the rendered map with a transparency.

6. The method of claim 5 , further comprising a step of co-registering the rendered map with an ultrasound image.

7. The method of claim 1 , further comprising a step of defining the at least one region of interest of the parametric map.

8. The method of claim 7 , in which the step of defining at least one region of interest comprises receiving user input specifying the region of interest.

9. The method of claim 8 , in which the step of receiving user input comprises receiving, via a graphical user interface, input defining a top and bottom depth.

10. The method of claim 9 , in which the input defining a top and bottom depth comprises input from the user of a depth and a height.

11. The method of claim 8 , in which the region of interest is a rectangle.

12. The method of claim 1 , in which the particular mathematical characteristic is a fixed constant.

13. The method of claim 1 , in which the reference level is offset by an offset value.

14. The method of claim 13 , in which the offset value is tunable by a user.

15. The method of claim 13 , in which the offset value is fixed.

16. The method of claim 1 , in which the statistical function is a standard deviation.

17. The method of claim 1 , in which a result of the statistical function is used to proportion a relationship of the upper and lower color map limits to the reference level.

18. The method of claim 1 , in which the first constant and the second constant are the same constant.

19. The method of claim 1 , in which the at least one reference level is fixed, and where the computation of the parametric map is pre-calibrated.

20. The method of claim 1 , in which the at least one reference level is fixed, and where the computation of the parametric map is adjusted using fluence-compensation on a per-wavelength basis.

21. The method of claim 5 , in which a transparency map is defined in relation to the reference level.

22. The method of claim 21 , in which the transparency map comprises a single-channel color map reflecting a transparency channel.

23. The method of claim 5 , in which the color map is a single-channel greyscale color map.

24. The method of claim 1 , further comprising a step of displaying the rendered parametric map to a user.

25. The method of claim 1 , in which the region of interest represents a subset of the parametric map.

26. The method of claim 1 , in which the region of interest represents the entire parametric map.

27. The method of claim 1 , where the rendered parametric map is a representation of oxygen saturation of hemoglobin.

28. The method of claim 1 , where the rendered parametric map is a representation of total opto-acoustic return signal intensity.

29. The method of claim 1 , where the rendered parametric map is displayed as a qualitative image without numerical values of the colorized representation being displayed with the image.

30. The method of claim 1 , in which the reference level, the upper color map limit and the lower color map limit are computed as to maximize a measure of contrast in the at least one region of interest.

31. The method of claim 7 , where the at least one region of interest is given by pixels that match a criteria such as the pixel value exceeding a threshold value as to indicate a high level of hemoglobin or other such criteria.

32. An optoacoustic imaging system for producing qualitative images of tissue in a volume of interest using relative contrast, comprising:
a source of electromagnetic energy for depositing energy into a volume;
a data acquisition subsystem for acquiring opto-acoustic return signals;
an electronics subsystem configured to:
produce a parametric map spatially representative of the tissue;
statistically determine a reference level against background material;
use the reference level to assign an upper color map limit and a lower color map limit, wherein the step of using the reference level to assign an upper color map limit comprises setting the upper color map limit to be the color reference level plus a scalar result of a statistical function applied to oxygenation level of blood in a region of interest of the parametric map times a color contrast parameter;
map pixels in an image to color values in a color map based on interpolation between the upper color map limit and the lower color map limit; and,
output the rendered image.

33. The system of claim 32 , wherein the background material comprises tissue.

34. The system of claim 33 , wherein the tissue comprises breast tissue.

35. The system of claim 32 , wherein the background material comprises reference tissue.

36. The system of claim 35 , wherein the reference tissue comprises breast tissue.

37. The system of claim 35 , wherein the reference tissue comprises a tissue phantom.

38. The system of claim 32 , wherein the b

Assignees

• Seno Medical Instr Inc

Inventors

• Zalev Jason
• Clingman Bryan

Classifications

• A61B8/4281

  characterised by sound-transmitting media or devices for coupling the transducer to the tissue · CPC title

• A61B8/5223

  for extracting a diagnostic or physiological parameter from medical diagnostic data (for algorithms to analyse biomedical images G06T7/0012) · CPC title

• A61B5/0035

  adapted for acquisition of images from more than one imaging mode, e.g. combining MRI and optical tomography · CPC title

• A61B5/004

  adapted for image acquisition of a particular organ or body part (A61B5/0082 takes precedence; arrangements for optical scanning A61B5/0062) · CPC title

• A61B5/0091

  for mammography · CPC title