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

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.sup.-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.

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.sup.-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.

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.sup.-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.

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.sup.-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.

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

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 cm.sup.1 ;
• 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 .lambda..sub.1 wherein .lambda..sub.1 =(1/.lambda..sub.0 -v.sub.1).sup.-1 and wherein v.sub.1 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 .lambda..sub.2 wherein .lambda..sub.2 =(1/.lambda..sub.0 -v.sub.2).sup.-1 and wherein v.sub.2 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.

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 cm.sup.1 ;
• 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.

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.

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.

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.

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.