ASSESSMENT OF TISSUE OR LESION DEPTH USING TEMPORALLY RESOLVED LIGHT SCATTERING SPECTROSCOPY

• US 20130253330A1
• Filed: 03/12/2013
• Published: 09/26/2013
• Est. Priority Date: 11/17/2004
• Status: Active Grant

• Current Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Original Assignee: Lawrence Livermore National Security LLC (Government of the United States of America)
• Inventors: Demos, Stavros G.
• Granted Patent: US 10,413,188 B2
• Time in Patent Office: Days
• US Class Current: 600/473
• CPC Class Codes: A61B 18/082 Probes or electrodes therefor
• CPC Class Codes: A61B 18/1492 having a flexible, catheter-like structure, e.g. for heart ablation A61B18/1477 takes precedence
• CPC Class Codes: A61B 18/22 the beam being directed along or through a flexible conduit, e.g. an optical fibre; Couplings or hand-pieces therefor
• CPC Class Codes: A61B 18/24 with a catheter A61B18/26, A61B18/28 take precedence
• CPC Class Codes: A61B 2017/00061 spectrum
• CPC Class Codes: A61B 2017/00066 intensity
• CPC Class Codes: A61B 2018/00351 Heart
• CPC Class Codes: A61B 2018/00357 Endocardium
• CPC Class Codes: A61B 2018/0212 using an instrument inserted into a body lumen, e.g. catheter
• CPC Class Codes: A61B 2090/062 penetration depth
• CPC Class Codes: A61B 5/0075 by spectroscopy, i.e. measuring spectra, e.g. Raman spectroscopy, infrared absorption spectroscopy A61B5/0071 takes precedence
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence
• CPC Class Codes: A61B 5/0086 using infrared radiation

Abstract

A method is described to enhance the ability to evaluate the depth of a tissue component or a lesion having optical properties different from a surrounding tissue using time resolved optical methods. This invention may be particularly suitable for the evaluation of lesion depth during RF ablation (irreversible tissue modification/damage) using specially designed devises (catheters) that deliver heat in a localized region for therapeutic reasons. The technique allows for increased ability to evaluate the depth of the ablated lesion or detect the presence of other processes such as micro-bubble formation and coagulation with higher sensitivity compared to that offered by steady state spectroscopy. The method can be used for in-vivo, real-time monitoring during tissue ablation or other procedures where information on the depth of a lesion or tissue is needed. Exemplary uses are found in tissue ablation, tissue thermal damage, lesion and tissue depth assessment in medical applications.

Claims

1. An optical time-resolved method for real-time evaluation of at least one in-vivo cardiac tissue lesion formation parameter, comprising:

producing a lesion in in-vivo cardiac tissue;

simultaneously with the step of producing a lesion, directing a pulse of optical interrogation radiation onto a first tissue site of said in-vivo cardiac tissue to produce induced radiation;

collecting said induced radiation to produce collected radiation having at least one signal temporal profile of intensity versus time;

quantifying a difference between signal data from said at least one signal temporal profile and reference data from at least one reference temporal profile to produce at least one quantification parameter (QP); and

determining, from said QP, at least one instantaneous condition of said in-vivo cardiac tissue.

2. The method of claim 1, further comprising providing an ablation catheter configured for delivering ablation energy to said in-vivo cardiac tissue to produce said lesion, wherein said catheter further incorporates at least one optical conduit adapted for directing said pulse of optical interrogation radiation at a first tissue site of said cardiac tissue and wherein said catheter further incorporates at least one optical conduit adapted for collecting said induced radiation from a second tissue site of said cardiac tissue.

3. The method of claim 1, wherein said lesion is produced by a process selected from the group consisting of (i) applying RF energy to said in-vivo cardiac tissue, (ii) applying a cryogenic energy to said in-vivo cardiac tissue and (iii) applying light energy to said in-vivo cardiac tissue and (iv) applying heat to said in-vivo cardiac tissue.

4. The method of claim 1, wherein said pulse is selected from the group consisting of mono-chromatic light, multiple wavelengths of light and a continuous spectrum of light.

5. The method of claim 4, wherein said pulse comprises a pulse-duration of less than 10 ns.

6. The method of claims 1, wherein said pulse is selected from the group consisting of multiple wavelengths of light and a continuous spectrum of light, the method further comprising separating said at least one signal temporal profile into a number n of spectral bands, wherein each spectral band n of said spectral bands comprises a respective temporal profile T(n).

7. The method of claim 6, wherein said signal data comprises at least one set of discrete data points P{T(n)} for at least one of said each spectral band n.

8. The method of claim 7, wherein one or more of said at least one set of discrete data points P{T(n)} forms a digital representation of one or more of said at least one signal temporal profile, wherein said digital representation provides signal intensity values at specific delay times.

9. The method of claim 7, wherein one or more of said at least one set of discrete data points P{T(n)} forms at least one digital representation of one or more of said at least one signal temporal profile, wherein said at least one digital representation provides signal intensity values at specific delay times, wherein the step of quantifying a difference comprises dividing at least a portion of said at least one digital representation by a predetermined set of discrete data points, wherein said QP comprises at least one set of normalized discrete data points at specific time delays.

10. The method of claim 7, wherein one or more of said at least one set of discrete data points P{T(n)} forms at least one digital representation of one or more of said at least one signal temporal profile, wherein said at least one digital representation provides signal intensity values at specific delay times, wherein the step of quantifying a difference comprises normalizing at least a portion of said at least one digital representation with a predetermined set of discrete data points, wherein said QP comprises at least one set of normalized discrete data points at specific time delays.

11. The method of claim 9, wherein said predetermined set of discrete data points comprises at least a portion of said reference data.

12. The method of claim 1, wherein said at least one reference temporal profile is obtained from said first tissue site before the step of producing a lesion.

13. The method of claim 1, wherein said at least one reference temporal profile is obtained from a pre-existing database.

14. The method of claim 9, wherein the step of quantifying a difference comprises applying a mathematic formulation between at least two members of a set of data points P(n) for a plurality of said each spectral band n.

15. The method of claim 9, wherein the step of quantifying a difference comprises applying a mathematic formulation between at least two members of a set of data points P(n) for different spectral bands of said each spectral band n.

16. The method of claim 9, wherein the step of quantifying a difference comprises generating fitting parameters for the set of data points P(n) for said each spectral band n.

17. The method of claim 9, wherein the step of quantifying a difference comprises generating fitting parameters to a data set generated via the application of a mathematical formulation between delay-time-corresponding data points of a set of data points P(n) from different spectral bands of said each spectral band n.

18. The method of claim 9, wherein the step of quantifying a difference comprises generating discrete values at one or more specific delay times following the application of a mathematical formulation between data points from different spectral bands at the corresponding specific delay times.

19. The method of claim 1, wherein said instantaneous condition comprises an instantaneous lesion depth at a depth A, the method further comprising:

determining the rate of formation of said lesion (a rate of cardiac tissue ablation) to said depth A; and

extrapolating from said rate the ablation time needed to create a lesion having a depth B that is greater than depth A.

20. The method of claim 1, wherein said instantaneous condition comprises an instantaneous depth at a depth of about 6 mm, the method further comprising:

determining the rate of formation of said lesion (a rate of cardiac tissue ablation) to said depth of about 8 mm; and

extrapolating from said rate the ablation time needed to create a lesion having a depth B that is greater than depth A.

21. The method of claim 19, wherein said instantaneous depth comprises an instantaneous lesion depth and wherein said rate of cardiac tissue ablation comprises a rate of lesion formation and wherein at least one of said instantaneous lesion depth and said rate of lesion formation can be estimated using a substantially linear relationship between cardiac ablation lesion depth and at least one quantification parameter of said collected radiation for lesion depths up to about 8 mm.

22. The method of claim 19, wherein said instantaneous depth comprises an instantaneous lesion depth and wherein said rate of cardiac tissue ablation comprises a rate for lesion formation and wherein at least one of said instantaneous lesion depth and said rate of lesion formation can be estimated using a monotonic relationship between cardiac ablation lesion depth and at least one quantification parameter of said collected radiation for lesion depths up to about 8 mm.

23. The method of claim 1, wherein said quantification parameter monotonically changes as lesion depth changes.

24. The method of claim 1, further comprising detecting the eruption of at least one steam pop by monitoring the temporal evolution of one or more of said at least one quantification parameter at different spectral bands during the step of producing a lesion.

25. The method of claim 1, further comprising determining a rate of tissue ablation by monitoring the change in depth of said lesion per unit time.

26. The method of claim 1, further comprising determining whether coagulum exists at said lesion by monitoring the temporal evolution of one or more of said at least one quantification parameter at different spectral bands during the step of producing a lesion.

27. The method of claim 1, further comprising determining whether charring exists at said lesion by monitoring the temporal evolution of one or more of said at least one quantification parameter at different spectral bands during the step of producing a lesion.

28. The method of claim 1, wherein said interrogation radiation comprises a wavelength within a range from about 600 nm to about 1500 nm.

29. The method of claim 1, wherein said interrogation radiation comprises a wavelength within a range from about 600 nm to about 970 nm.

30. The method of claim 1, further comprising extrapolating an ablation depth of up to about 1.5 cm from a rate of change of one or more of said at least one quantification parameter.

31. The method of claim 1, further comprising determining, from one or more of said at least one quantification parameter, if normal tissue is present, wherein the step of determining if normal tissue is present comprises comparing said QP to a normalized reference temporal profile obtained from a pre-existing database.

32. The method of claim 2, further comprising utilizing said one or more changes of said at least one quantification parameter to determine if there is a non-proper contact of said catheter with normal tissue, wherein the step of utilizing comprises comparing said OQP to a normalized reference temporal profile obtained from a pre-existing database.

33. The method of claim 1, further comprising determining, from one or more of said at least one quantification parameter if abnormal tissue is present, wherein the step of determining if abnormal tissue is present comprises comparing said QP to a normalized reference temporal profile obtained from a pre-existing database.

34. The method of claim 1, further comprising measuring a change of the temporal evolution of one or more of said at least one quantification parameter at one or more spectral band during the-step of producing a lesion, the method further comprising utilizing said change to detect in real time the formation of at least one microbubble in the affected tissue, wherein said microbubble constitutes a precursor to explosive release of gas, also called steam pops.