Method for distinguishing between calcified atherosclerotic tissue and fibrous atherosclerotic tissue or normal cardiovascular tissue using Raman spectroscopy

• US 5,293,872 A
• Filed: 04/03/1991
• Issued: 03/15/1994
• Est. Priority Date: 04/03/1991
• Status: Expired due to Term

• Current Assignee: Mediscience Technology Corp. (Sensivida Medical Technologies, Inc.)
• Original Assignee: Mediscience Technology Corp. (Sensivida Medical Technologies, Inc.)
• Inventors: Alfano, Robert R., Liu, Cheng H.
• Primary Examiner(s): Smith, Ruth S.
• Application Number:
  US07/678,637
• Time in Patent Office: 1,077 Days
• Field of Search: 128/395, 128/398, 128/664, 128/665, 606/7, 606/13-16
• US Class Current: 600/475
• CPC Class Codes: A61B 5/0071 by measuring fluorescence emission
• 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 5/0086 using infrared radiation
• CPC Class Codes: A61B 5/7257 using Fourier transforms
• CPC Class Codes: G01N 2021/656 Raman microprobe
• CPC Class Codes: G01N 21/65 Raman scattering

Abstract

A method for distinguishing between calcified atherosclerotic tissue and either fibrous atherosclerotic tissue or normal cardiovascular tissue. The present method is based on the discovery that, when irradiated with a beam of monochromatic infrared light, calcified atherosclerotic human aortic tissue produces a Fourier Transform Raman spectrum which is distinguishable from analagous spectra obtained from fibrous atherosclerotic human aortic tissue and normal human aortic tissue. Some salient differences in the respective Raman spectra are the presence of five Raman bands at Raman shifts of 957, 1071, 1262-1300, 1445, and 1659 cm^-1 (±4 cm^-1 for all shifts) for the calcified tissue as compared to three Raman bands at Raman shifts of 1247-1270, 1453 and 1659 cm^-1 (±4 cm^-1 for all shifts) for the fibrous tissue and three Raman bands at Raman shifts of 1247-1270, 1449 and 1651 cm^-1 (±4 cm^-1 for all shifts) for the normal tissue. In addition, it was discovered that the ratios of intensities for the Raman bands at 1659 and 1453 cm^-1 and at 1254 and 1453 cm^-1 were 0.69 and 0.53, respectively, for the calcified tissue, 1.02 and 0.85, respectively, for the fibrous tissue and 1.2 and 0.83, respectively, for the normal tissue.

Claims

1. A method for distinguishing between calcified atherosclerotic tissue and fibrous atherosclerotic tissue or normal cardiovascular tissue comprising the steps of:

a) irradiating a cardiovascular tissue sample with a beam of monochromatic infrared light;

b) obtaining the infrared Raman spectrum for the cardiovascular tissue sample in the Raman spectral region from 700 to 1900 cm^-1 ; and

c) comparing the infrared Raman spectrum so obtained for the tissue sample with infrared Raman spectra correspondingly obtained from known samples of calcified atherosclerotic tissue and from either fibrous atherosclertoic tissue or normal cardiovascular tissue for the same type of tissue being tested.

2. The method of claim 1 wherein the cardiovascular tissue being tested is human cardiovascular tissue.

3. The method of claim 2 wherein the human cardiovascular tissue is human aortic tissue.

4. A method of determining if a cardiovascular tissue sample is calcified atherosclerotic, on one hand, or fibrous atherosclerotic or normal, on the other hand, comprising the steps of:

a) irradiating the cardiovascular tissue sample with a beam of infrared monochromatic light;

b) measuring the number of Raman bands produced thereby in the Raman spectral region from 700 to 1900 cm^-1 ; and

c) comparing the number of Raman bands measured with the number of Raman bands correspondingly measured from known samples of calcified atherosclerotic tissue and fibrous atherosclerotic tissue or normal cardiovascular tissue for the same type of tissue being tested.

5. The method of claim 4 wherein the tissue being tested is human aortic tissue and wherein the number of Raman bands is five for calcified atherosclerotic and three for fibrous atherosclerotic tissue and normal tissue.

6. A method of determining if a human aortic tissue sample is calcified atherosclerotic, on the one hand, or fibrous atherosclerotic or normal, on the other hand, comprising the steps of:

a) irradiating the human aortic tissue sample with a beam of infrared monochromatic light;

b) measuring for a Raman band at 957±

4 cm^-1, or for a Raman band at 1071±

4 cm^-1, or for a pair of Raman bands at 957±

4 cm^-1 and 1071±

4 cm^-1 ;

c) whereby the presence of a Raman band at 957±

4 cm^-1, or a Raman band at 1071±

4 cm^-1, or a pair of Raman bands at 957±

4 cm^-1 and 1071±

4 cm^-1, respectively, indicates that the human aortic tissue sample is calcified atherosclerotic and the absence of a Raman band at 957±

4 cm^-1, or at 1071±

4 cm^-1, or at both 957±

4 cm^-1 and 1071±

4 cm^-1 indicates that the human aortic tissue sample is either fibrous atherosclerotic or normal.

7. A method for determining whether a cardiovascular tissue sample is calcified atherosclerotic tissue as compared to fibrous atherosclerotic tissue or normal cardiovascular tissue comprising the steps of:

a) irradiating the cardiovascular tissue sample with a beam of infrared monochromatic light;

b) measuring the intensity of light at a pair of Raman bands in the Raman spectral region from 700 to 1900 cm^-1 which are correspondingly present in the infrared Raman spectra of calcified atherosclerotic tissue and fibrous atherosclerotic tissue or of calcified atherosclerotic tissue and normal cardiovascular tissue for the same type of tissue being tested;

c) calculating the ratio of said intensities; and

d) comparing said ratio to the respective ratios for calcified atherosclerotic tissue and fibrous atherosclerotic tissue or for calcified atherosclerotic tissue and normal cardiovascular tissue for the same type of tissue being tested.

8. The method as claimed in claim 7 further comprising the steps of:

a) irradiating the cardiovascular tissue sample with a beam of fluorescence inducing light;

b) obtaining a fluorescence spectrum for the cardiovascular tissue sample;

c) comparing said fluorescence spectrum with standard fluorescence spectra for fibrous atherosclerotic tissue and calcified atherosclerotic tissue or normal tissue for the same type of tissue being tested.

9. The method as claimed in claim 7 wherein said cardiovascular tissue sample is human aortic tissue.

10. A method for determining whether a human aortic tissue sample is calcified atherosclerotic tissue as compared to fibrous atherosclerotic tissue or normal cardiovascular tissue comprising the steps of:

a) irradiating the cardiovascular tissue sample with a beam of infrared monochromatic light;

b) measuring the intensity of light at 1659 and 1453 cm^-1 ;

c) calculating the ratio of said intensities; and

d) comparing said ratio to the respective ratios for calcified atherosclerotic tissue and fibrous atherosclerotic tissue or for calcified atherosclerotic tissue and normal cardiovascular tissue for the same type of tissue being tested.

11. A method for determining whether a human aortic tissue sample is calcified atherosclerotic tissue as compared to fibrous atherosclerotic tissue or normal cardiovascular tissue comprising the steps of:

a) irradiating the cardiovascular tissue sample with a beam of infrared monochromatic light;

b) measuring the intensity of light at 1254 and 1453 cm^-1 ;

c) calculating the ratio of said intensities; and

d) comparing said ratio to the respective ratios for calcified atherosclerotic tissue and fibrous atherosclerotic tissue or for calcified atherosclerotic tissue and normal cardiovascular tissue for the same type of tissue being tested.

12. A method for determining if a human aortic tissue sample is calcified atherosclerotic as compared to fibrous atherosclerotic or normal, comprising the steps of:

a) irradiating the human aortic tissue sample with a monochromatic beam of infrared light;

b) measuring for the presence of a first Raman band having a peak at 957±

4 cm^-1 and a second Raman band having a peak at 1659±

4 cm^-1 or 1651±

4 cm^-1 ;

c) whereby the presence of said first Raman band and said second Raman band indicates that the human aortic tissue sample is calcified atherosclerotic, and the absence of said first Raman band and the presence of said second Raman band indicates that the human aortic tissue sample is fibrous atherosclerotic or normal.

13. A method for determining if a human aortic tissue sample is calcified atherosclerotic as compared to fibrous atherosclerotic or normal, comprising the steps of:

a) irradiating the human aortic tissue sample with a monochromatic beam of infrared light;

b) measuring the intensity of Raman scattered light at a Raman shift of about 957 cm^-1 and at a Raman shift of about 1659 cm^-1 ;

c) calculating the ratio of intensities for the Raman scattered light at a Raman shift of about 957 cm^-1 and at a Raman shift of about 1659 cm^-1 ;

d) comparing said ratio to the respective ratios for calcified atherosclerotic human aortic tissue and for fibrous atherosclerotic human aortic tissue or normal human aortic tissue.

14. A system for determining if a cardiovascular tissue sample is calcified atherosclerotic as compared to fibrous atherosclerotic or normal, comprising:

a) means for producing an infrared monochromatic beam of light having a wavelength 0;

b) means for directing said infrared monochromatic beam to the cardiovascular tissue sample;

c) means for collecting the Raman scattered light from the cardiovascular tissue sample in the Roman spectrum region from 700 to 1900 cm¹ ;

d) a pair of narrow band filter optically coupled to said collecting means, the first of said narrow band filter being selective for the Raman scattered light at a wavelength λ

₁ wherein λ

₁ =(1/λ

₀ -v₁)^-1 and wherein v₁ is the wavenumber of a Raman shift common to the Raman spectra for calcified atherosclerotic tissue and fibrous atherosclerotic tissue or normal tissue for the same type of tissue being tested, the second of said narrow band filter being selective for the Raman scattered light at a wavelength λ

₂ wherein λ

₂ =(1/λ

₀ -v₂)^-1 and wherein v₂ is the wavenumber of a Raman shift particular to the Raman spectrum for calcified atherosclerotic tissue;

e) a pair of photodetectors, the first of said photodetectors being optically coupled to the output of said first narrow band filter means for converting the Raman scattered light incident thereon into a first electrical signal and the second of said photodetectors being optically coupled to the output of said second narrow band filter means for converting the Raman scattered light incident thereon into a second electrical signal;

f) means coupled to the outputs of said photodetectors for determining, based on said electrical signals, whether the cardiovascular tissue sample is calcified atherosclerotic as compared to fibrous atherosclerotic or normal; and

g) means for displaying the results of said determination.

15. A system for determining if a cardiovascular tissue sample is calcified atherosclerotic tissue as compared to fibrous atherosclerotic tissue or normal cardiovascular tissue, the system comprising:

a) means for producing an imaging light;

b) means for producing a beam of monochromatic infrared light;

c) an endoscope comprising in a first channel means for transmitting said imaging light to the cardiovascular tissue sample and for collecting an image of the cardiovascular tissue sample and in a second channel means for transmitting said beam of monochromatic infrared light to the cardiovascular tissue sample and for collecting the Raman scattered light from the cardiovascular tissue sample in the Raman spectrum region from 700 to 1900 cm¹ ;

d) means, coupled to said image collection means, for displaying said image of the cardiovascular tissue sample;

e) means, coupled to said Raman scattered light collection means, for producing a Raman spectrum for the cardiovascular tissue sample;

f) means for comparing said Raman spectrum to standard Raman spectra for calcified atherosclerotic tissue and for either fibrous atherosclerotic tissue or normal cardiovascular tissue for the same type of cardiovascular tissue being tested; and

g) means for displaying the results of the comparison.

16. A system for determining if a cardiovascular tissue sample is calcified atherosclerotic tissue as compared to fibrous atherosclerotic tissue or normal cardiovascular tissue, the system comprising:

a) means for producing an imaging light;

b) means for producing a beam of monochromatic infrared light;

c) and endoscope comprising in a first channel means for transmitting said imaging light to the cardiovascular tissue sample and for collecting an image of the cardiovascular tissue sample and in a second channel means for transmitting said beam of monochromatic infrared light to the cardiovascular tissue sample and for collecting the Raman scattered light from the cardiovascular tissue sample in the Raman spectral region from 700 to 1900 cm;

d) means, coupled to said image collection means, for displaying said image of the cardiovascular tissue sample;

e) means, coupled to said Raman scattered light collection means, for producing a Raman spectrum for the cardiovascular tissue sample;

f) means for calculating the ratio of intensities of light at two Raman bands common to the infrared Raman spectra for calcified atherosclerotic tissue and fibrous atherosclerotic tissue or normal cardiovascular tissue for the same type of tissue being tested;

g) means for comparing said ratio to the respective ratios for calcified atherosclerotic tissue and for either fibrous atherosclerotic tissue or normal cardiovascular tissue for the same type of cardiovascular tissue being tested; and

h) means for displaying the results of the comparison.

17. A method for determining if a cardiovascular tissue sample is calcified atherosclerotic, fibrous atherosclerotic, or normal, comprising the steps of:

a) irradiating the cardiovascular tissue sample with a monochromatic beam of infrared light;

b) irradiating the cardiovascular tissue sample with a monochromatic beam of fluorescence inducing light;

c) obtaining the infrared Raman spectrum for the cardiovascular tissue sample;

d) obtaining the fluorescence spectrum for the cardiovascular tissue sample;

e) comparing said infrared Raman spectrum with standard infrared Raman spectra for calcified atherosclerotic tissue and for either fibrous atherosclerotic tissue or normal tissue for the same type of tissue being tested; and

f) comparing said fluorescence spectrum for the cardiovascular tissue sample with standard fluorescence spectra for fibrous atherosclerotic tissue and for either calcified atherosclerotic tissue or normal tissue for the same type of tissue being tested.

18. The method as claimed in claim 17 further comprising the step of ablating the cardiovascular tissue sample if it is found to be atherosclerotic.

19. A system for determining if a cardiovascular tissue sample is calcified atherosclerotic, fibrous atherosclerotic, or normal, comprising:

a) means for producing a monochromatic beam of infrared light;

b) means for producing a monochromatic beam of fluorescence inducing light;

c) means for directing said monochromatic beam of infrared light to the cardiovascular tissue sample and for collecting Raman scattered light from the cardiovascular tissue sample;

d) means for directing said monochromatic beam of fluorescence inducing light to the cardiovascular tissue sample and for collecting fluorescent light from the cardiovascular tissue sample;

e) means, coupled to said Raman scattered light collecting means, for producing a Raman spectrum for the cardiovascular tissue sample;

f) means, coupled to said fluorescence collecting means, for producing a fluorescence spectrum for the cardiovascular tissue sample;

g) means for comparing said Raman spectrum for the cardiovascular tissue sample to standard Raman spectra for calcified atherosclerotic tissue and for fibrous atherosclerotic tissue or normal tissue for the same type of tissue being tested; and

h) means for comparing said fluorescence spectrum for the cardiovascular tissue sample to standard fluorescence spectra for fibrous atherosclerotic tissue and for calcified atherosclerotic tissue or normal tissue for the same type of tissue being tested.

20. The system as claimed in claim 19 further comprising means for ablating the cardiovascular tissue sample if it is found to be atherosclerotic.

21. A system for determining if a cardiovascular tissue sample is calcified atherosclerotic, fibrous atherosclerotic or normal, comprising:

a) means for producing an imaging light;

b) means for producing a monochromatic beam of infrared light;

c) means for producing a monochromatic beam of fluorescence inducing light;

d) an endoscope comprising in a first channel means for directing said imaging light at the cardiovascular tissue sample and for collecting an image of the cardiovascular tissue sample and in a second channel means for directing said monochromatic beam of infrared light and said monochromatic beam of fluorescence inducing light at the cardiovascular tissue and for collecting the Raman scattered light and the fluorescence from the cardiovascular tissue;

e) means, coupled to said collection means in said first channel, for displaying said image of the cardiovascular tissue sample;

f) means, coupled to said collection means in said second channel, for producing a Raman spectrum for the cardiovascular tissue sample;

g) means for comparing said Raman spectrum for the cardiovascular tissue sample with standard Raman spectra for calcified atherosclerotic tissue and fibrous atherosclerotic tissue or normal tissue for the same type of tissue being tested;

h) means for displaying the results of said Raman comparison;

i) means, coupled to said collection means in said second channel, for producing a fluorescence spectrum for the cardiovascular tissue sample;

j) means for comparing said fluorescence spectrum for the cardiovascular tissue sample with standard fluorescence spectra for fibrous atherosclerotic tissue and calcified atherosclerotic tissue or normal tissue for the same type of tissue being tested; and

k) means for displaying the results of said fluorescence comparison.

22. The system as claimed in claim 21 further comprising means for ablating the cardiovascular tissue sample if it is found to be atherosclerotic.