System for normalizing spectra

• US 6,839,661 B2
• Filed: 12/15/2000
• Issued: 01/04/2005
• Est. Priority Date: 12/15/2000
• Status: Expired due to Fees

• Current Assignee: Luma Imaging Corp. (SpectraScience, Inc.)
• Original Assignee: MediSpectra, Inc. (SpectraScience, Inc.)
• Inventors: Costa, Peter J., Nordstrom, Robert J., Hui, Kwong
• Primary Examiner(s): NGHIEM, MICHAEL P
• Application Number:
  US09/738,612
• Publication Number:
  US 20020107668A1
• Time in Patent Office: 1,481 Days
• Field of Search: 702/69, 702 75- 77, 702/189, 702/199, 600/473, 600/476, 600/478
• US Class Current: 702/189
• CPC Class Codes: G01N 21/274 Calibration, base line adjustment, drift correction

Abstract

A method and system for normalizing optical spectra using a non-uniform segment normalization. A spectrum is obtained and is represented as a function of wavelength as an amplitude at each of a plurality of wavelengths. At least one segment of the spectrum is selected, each selected segment being bounded by an upper wavelength and a lower wavelength. A normalization factor is computed as the sum of the areas for each of the selected segments. The spectrum is normalized by dividing at least one amplitude of the spectrum by the normalization factor. Segments can be selected with different wavelength ranges, that is, segments can be non-uniform. Test specimens can be categorized based on an analysis of normalized spectra. In particular, the specimen to be tested can be human cervical tissue, and the state of health of the tissue can be determined.

Claims

1. A method of performing spectral analysis, the method comprising:

obtaining an optical spectrum, and

normalizing said optical spectrum by application of non-uniform segment normalization, said normalizing step comprising;

selecting one or more segments from said optical spectrum, each of said segments being bounded by an upper wavelength and a lower wavelength and containing one or more wavelengths, each of said wavelengths having an associated amplitude,

determining an area under a curve associated with each particular segment, wherein each said curve is bounded along a first axis by said upper wavelength and said lower wavelength of said particular segment, and along a second axis by said amplitudes associated with each of said wavelengths included in said particular segment,

summing said areas for each of said segments to determine a normalization factor, and

dividing at least one said associated amplitude for one of said wavelengths included in said segments by said normalization factor.

2. The method of claim 1, wherein a first segment differs in size of wavelength range from that of a second segment, wherein said size of wavelength range is defined as the absolute magnitude of a difference between said upper wavelength and said lower wavelength.

3. The method of claim 1, wherein a first segment is equal in wavelength range to a second segment, wherein said size of wavelength range is defined as the absolute magnitude of a difference between said upper wavelength and said lower wavelength.

4. The method of claim 1, wherein said one or more segments comprises at least first and second non-contiguous segments.

5. The method of claim 1, wherein said one or more segments comprises at least first, second and third segments, and there exists a first span between an upper wavelength of said first segment and a lower wavelength of said second segment, and a second span between an upper wavelength of said second segment and a lower wavelength of said third segment.

6. The method of claim 5, wherein said first and said second spans differ in magnitude.

7. The method of claim 5, wherein said first and said second spans are substantially equal in magnitude.

8. The method of claim 1, further comprising obtaining said spectrum from a specimen of human cervical tissue.

9. The method of claim 1, further comprising determining a disease status of said test specimen by analyzing said optical spectrum subsequent to said normalizing.

10. A system for performing spectral analysis comprising:

a spectrographic device adapted to obtain an optical spectrum from a test specimen,

a processor adapted to normalize said optical spectrum by application of non-uniform segment normalization, and

machine-readable instructions executing on said processor and adapted to;

select one or more segments from said optical spectrum, each of said segments being bounded by an upper wavelength and a lower wavelength, and containing one or more wavelengths, each of said wavelengths having an associated amplitude,

determine an area under a curve associated with each particular one of said segments, wherein each said curve is bounded along a first axis by said upper wavelength and said lower wavelength of said particular segment, and along a second axis by said amplitudes associated with each of said wavelengths included in said particular segment,

sum said areas for each of said segments to determine a normalization factor, and

divide at least one said associated amplitude for one of said wavelengths included in said segments by said normalization factor.

11. The system of claim 10, wherein said machine readable instructions are further adapted to one of select and enable a user to select a first segment different in size of wavelength range from that of a second segment, wherein said size of wavelength range is defined as the absolute magnitude of a difference between said upper wavelength and said lower wavelength.

12. The system of claim 10, wherein said machine readable instructions are further adapted to one of select and enable a user to select a first segment to be substantially equal in size of wavelength range to that of a second segment, wherein said size of wavelength range is defined as the absolute magnitude of a difference between said upper wavelength and said lower wavelength.

13. The system of claim 10, wherein said machine readable instructions are further adapted to one of select and enable a user to select said one or more segments to include at least first and second non-contiguous segments.

14. The system of claim 10, wherein said machine readable instructions are further adapted to one of select and enable a user to select said one or more segments to include at least first, second and third segments, and there exists a first wavelength span between an upper wavelength of said first segment and a lower wavelength of said second segment, and a second wavelength span between an upper wavelength of said second segment and a lower wavelength of said third segment.

15. The system of claim 14, wherein said first and said second spans differ in magnitude.

16. The system of claim 14, wherein said first and said second spans are substantially equal in magnitude.

17. The system of claim 10, wherein said spectrographic device is further adapted to obtain said optical spectrum from a specimen of human cervical tissue.

18. The system of claim 10, wherein said machine readable instructions are further adapted to extract a test parameter from said optical spectrum.

19. The system of claim 10, wherein said machine readable instructions are further adapted to determine a disease status of said test specimen by analyzing said optical spectrum, subsequent to said normalizing.