Method and apparatus for investigating histology of epithelial tissue

• US 20060089553A1
• Filed: 07/21/2003
• Published: 04/27/2006
• Est. Priority Date: 07/19/2002
• Status: Abandoned Application

• Current Assignee: Astron Clinica Ltd. (Boston Scientific Corporation)
• Original Assignee: Astron Clinica Ltd. (Boston Scientific Corporation)
• Inventors: Cotton, Symon D'Oyly
• Application Number:
  US10/521,639
• Publication Number:
  US 20060089553A1
• Time in Patent Office: Days
• US Class Current: 600/473
• CPC Class Codes: A61B 5/0059 using light, e.g. diagnosis by transillumination, diascopy, fluorescence A61B5/0093, A61B5/1455, A61B5/02416 and A61B5/0261 take precedence
• CPC Class Codes: A61B 5/14546 for measuring analytes not otherwise provided for, e.g. ions, cytochromes
• CPC Class Codes: A61B 5/443 Evaluating skin constituents, e.g. elastin, melanin, water
• CPC Class Codes: A61B 5/444 Evaluating skin marks, e.g. mole, nevi, tumour, scar
• CPC Class Codes: A61B 5/445 Evaluating skin irritation or skin trauma, e.g. rash, eczema, wound, bed sore
• CPC Class Codes: G01N 21/314 with comparison of measurements at specific and non-specific wavelengths dual wavelength spectrometry G01J3/427
• CPC Class Codes: G01N 21/359 using near infrared light

Abstract

A method for monitoring the presence of selected chromophores in a sample of epithelial tissue, independent of the amount of a predetermined chromophore, the method comprising: illuminating an area of tissue by projecting light from a light source of at least two different wavelengths λ₁, λ₂; receiving light remitted by the illuminated area of tissue at a photoreceptor; analysing the received light to identify and measure the proportion of light of each wavelength remitted from the tissue I_r (λ); calculating the ratio of light at each wavelength returned from the tissue R_t, (λ), and then calculating Z=Formula (I); where 1 is chosen such that Z is independent of the amount of predetermined chromophore. Typically 1 is calculated such that Z=Formula (II); where j and k are such that 2j α(λ₁)=2kj α(λ₂)=1 where α(λ₁) and α(λ₂) are the absorbtion coefficients for the predetermined chromophore at each wavelength.

Claims

1. A method for monitoring the presence of selected chromophores in a sample of epithelial tissue, independent of the amount of a predetermined chromophore, the method comprising:

illuminating an area of tissue by projecting light from a light source of at least two different wavelengths λ

₁, λ

₂;

receiving light remitted by the illuminated area of tissue at a photoreceptor;

analysing the received light to obtain a measurement R_t(λ

) for each wavelength and then calculating;

$Z=\frac{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_1\right)}{{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_2\right)}^l}$

where l is chosen such that Z is independent of the amount of predetermined chromophore.

2. A method according to claim 1, in which R_t(λ

) is calculated by analysing the received light to identify and measure the proportion of light of each wavelength remitted from the tissue I_r(λ

); and

calculating the ratio of light at each wavelength returned from the tissue R_t(λ

).

3. A method according to claim 1, in which l is calculated such that

$Z=\frac{{R_t}^{}}{}$

( c , h , λ

1 ) j R t ⁡

( c , h , λ

2 ) jk = R t ⁡

( λ

1 ) j R t ⁡

( λ

2 ) jk = R t ⁡

( λ

1 ) R t ⁡

( λ

2 ) l

where j and k are such that;

2jα

(λ

₁)=2kjα

(λ

₂)=1 where α

(λ

₁) and α

(λ

₂) are the absorbtion coefficients for the predetermined chromophore at each wavelength.

4. A method according to claims claim 1, in which the predetermined chromophore is melanin.

5. A method according to claim 1, in which the predetermined chromophore is haemoglobin.

6. A method according to claim 1, in which the epithelial tissue is skin.

7. A method according to claim 1, in which the wavelengths λ

₁, λ

₂ are chosen such that a change in collagen level causes a relatively small change in the absorbtion of λ

₁, and a relatively large change in the absorbtion of λ

₂.

8. A method according to claim 7, in which the difference between the two wavelengths λ

₁, λ

₂ is at least 200 nm.

9. A method according to claim 8, in which the wavelengths are substantially 700 nm and 940 nm respectively.

10. A method of forming an image of an area of epithelial tissue independent of the amount of a predetermined chromophore in the tissue, locations, formed by obtaining Z for a plurality of locations within the area, Z being obtained by illuminating an area of tissue by projecting light from a light source of at least two different wavelengths λ

₁, λ

₂;

receiving light remitted by the illuminated area of tissue at a photoreceptor;

analysing the received light to analysing the received light to obtain a measurement R_t(λ

) for each wavelength and then calculating;

$Z=\frac{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_1\right)}{{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_2\right)}^l}$

where l is chosen such that Z is independent of the amount of predetermined chromophore; and

mapping the amounts Z at positions indicative of the location within the area of the measurement.

11. A method according to claim 10, in which R_t(λ

) is calculated by analysing the received light to identify and measure the proportion of light of each wavelength remitted from the tissue I_r(λ

); and

calculating the ratio of light at each wavelength returned from the tissue R_t(λ

).

12. A method according to claim 10, in which l is calculated such that

$Z=\frac{{R_d}^{}}{}$

( c , h , λ

1 ) j R d ⁡

( c , h , λ

2 ) jk = R t ⁡

( λ

1 ) j R t ⁡

( λ

2 ) jk = R t ⁡

( λ

1 ) R t ⁡

( λ

1 ) l

where j and k are such that 2jα

(λ

₁)=2kjα

(λ

₂)=1 where α

(λ

₁) and α

(λ

₂) are the absorbtion coefficients for the predetermined chromophore at each wavelength.

13. A method according to claim 10, in which the at least two sets of calculations

$Z=\frac{R_t}{}$

( λ

1 ) R t ⁡

( λ

2 ) l

are carried out, a first calculation with l, such that Z is independent of the amount of a first predetermined chromophore, and a second calculation with l₂ such that Z is independent of the amount of a second predetermined chromophore.

14. A method according to claim 10 in which the light source used to illuminate the tissue, is of at least three wavelengths, λ

₁,λ

₂,λ

₃ and at least three pairs of calculations of Z are made, namely

$Z=\frac{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_1\right)}{{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_2\right)}^{\mathrm{l1}}},Z=\frac{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_2\right)}{{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_3\right)}^{\mathrm{l2}}},Z=\frac{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_1\right)}{{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_3\right)}^{\mathrm{l3}}}$

where l₁ l₂ l₃ are each chosen such that Z is independent of the amount of the predetermined chromophore for the respective pair of wavelengths.

15. Apparatus for monitoring the presence of selected chromophores in a sample of epithelial tissue, independent of the amount of a predetermined chromophore comprising a light source for illuminating tissue with light of at least two different wavelengths λ

₁, λ

₂.

a photoreceptor for receiving images remitted by the illuminated area of tissue at a photoreceptor; and

microprocessor means for analysing the received light to identify and measure the proportion of light of each wavelength remitted from the tissue I_r(λ

);

calculating the ratio of light at each wavelength returned from the tissue R_t(λ

), and then calculating;

$Z=\frac{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_1\right)}{{R_t<br><br>\left({\mathrm{\lambda <br><br>}}_2\right)}^l}$

where l is chosen such that Z is independent of the amount of predetermined chromophore.

16. Apparatus according to claim 15, also comprising image creation means for receiving a plurality of values of Z, each for a specified location on the tissue, and providing a mapped image representing the value of Z at the plurality of locations on the tissue.