Method for measurement of skin histology

• US 6,324,417 B1
• Filed: 05/19/1999
• Issued: 11/27/2001
• Est. Priority Date: 11/19/1996
• Status: Expired due to Fees

• Current Assignee: MedX Health Corporation
• Original Assignee: Optiscan Pty Ltd.
• Inventors: Cotton, Symon DʼOyly
• Primary Examiner(s): Casler, Brian L.
• Application Number:
  US09/314,751
• Time in Patent Office: 923 Days
• Field of Search: 600/473-477, 250/338.1, 250/339.11, 356/448, 382/128
• US Class Current: 600/475
• 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 5/444 Evaluating skin marks, e.g. mole, nevi, tumour, scar

Abstract

A method and apparatus for non-invasively measuring skin structure. Infrared radiation over an area of skin under investigation is measured to give an indication of the variation in papillary dermis thickness over said area, and the skin color coordinates at a plurality of locations over the same area of skin is also measured. The data obtained is used to calculate corrected skin color coordinates over the area corresponding to a predetermined papillary dermis thickness. The corrected skin color coordinates so obtained are compared with a reference color coordinate range for healthy skin of the same predetermined papillary dermis thickness. At an abnormal region, where the corrected skin color coordinates lie outside the reference color coordinate range, the depth of penetration of dermal melanin can be measured.

Claims

1. A method of non-invasively analysing skin structure, comprising the steps of:

(i) measuring radiation having a wavelength within a wave band extending from 600 nm and into infrared from at least one location in an area of skin under investigation so as to give an indication of papillary dermis thickness over said area;

(ii) measuring skin colour co-ordinates at said at least one location in said area of skin;

(iii) using data obtained in measuring steps (i) and (ii) to calculate corrected skin colour co-ordinates over said area which correspond to a predetermined papillary dermis thickness, and;

(iv) comparing the corrected skin colour co-ordinates obtained in step (iii) with a reference colour co-ordinate range for healthy skin of said the same predetermined papillary dermis thickness.

2. A method according to claim 1, comprising the additional steps of;

(v) identifying an abnormal location within said area of skin where the corrected skin colour co-ordinates lie outside the reference colour co-ordinate range;

(vi) calibrating the corrected skin colour co-ordinates of said abnormal location with the corrected skin colour co-ordinates'"'"' of at least one skin location having colour co-ordinates lying within said reference colour co-ordinate range for normal skin, and;

(vii) using the skin colour co-ordinates to assess a degree of abnormality of said abnormal skin location.

3. A method according to claim 2, wherein an independent measurement is made of epidermal melanin level.

4. A method according to claim 3, wherein said independent measurement of epidermal melanin level is by polarized light.

5. A method according to claim 2, wherein said calibration in step (vi) includes estimating epidermal melanin level in said abnormal location by reference to epidermal melanin levels calculated within at least one normal skin location adjacent said abnormal region.

6. A method according to claim 2, wherein said calibration in step (vi) includes measuring epidermal melanin levels at said abnormal location by assessing any deviation at the blue end of the spectrum at said abnormal location from the reference colour co-ordinate range for normal skin.

7. A method according to claim 2, wherein step (i), a single infrared image at a wavelength of greater than about 1100 nm is obtained for each of said locations.

8. A method according to claim 2, wherein in step (i) two images, each at a different wavelength, are obtained for each of said locations, whereby to enable the effect of any epidermal melanin and dermal blood present to be accounted for in the calculation of step (iii).

9. A method according to claim 8, wherein said wavelengths fall within wavelength bands of 800-1000 nm and 600-800 nm respectively.

10. A method according to claim 2, wherein the skin colour coordinates of step (ii) are acquired from an image using different lighting conditions than used to obtain the healthy skin reference colour coordinate range, and a white standard or other correction factor is used to allow calibration of the image with the reference colour coordinate range.

11. A method according to claim 1, wherein an independent measurement is made of epidermal melanin level.

12. A method according to claim 11, wherein said independent measurement of epidermal melanin level is by polarized light.

13. A method according to claim 1, wherein step (i), a single infrared image at a wavelength of greater than about 1100 nm is obtained for each of said locations.

14. A method according to claim 1, wherein in step (i) two images, each at a different wavelength, are obtained for each of said locations, thereby to enable the effect of any epidermal melanin or dermal blood present to be accounted for in the calculation of step (iii).

15. A method according to claim 14, wherein said wavelengths fall within wavelength bands of 800-1000 nm and 600-800 nm respectively.

16. A method according to claim 14, wherein said infrared image(s) is or are obtained using infrared photographic film, or laser(s) or by spectral analysis.

17. A method according to claim 1, wherein the reference colour coordinate range for normal skin at the predetermined papillary dermis thickness referred to in step (iv), is obtained as a curved surface lying within a three-dimensional colour space, with a first bounding axis relating to the amount of melanin within the epidermis and a second bounding axis relating to the amount of blood within the dermis.

18. A method according to claim 17, wherein said three-dimensional colour space is selected from LMS, RG5 and UV G IR colour spaces.

19. A method according to claim 1, wherein the skin colour co-ordinates of step (ii) are acquired from an image using lighting conditions and a calibration set-up which are the same as lighting conditions and a calibration set-up used to produce the healthy skin reference colour co-ordinate range.

20. A method according to claim 1, wherein the skin colour coordinates of step (ii) are acquired from an image using different lighting conditions than used to obtain the healthy skin reference colour coordinate range, and a white standard or other correction factor is used to allow calibration of the image with the reference colour coordinate range.

21. An apparatus for non-invasively analysing skin structure, comprising:

a projector for projecting radiation having a wavelength within a wave band extending from 600 nm and into infrared onto an area of skin under investigation;

measuring means for measuring remitted radiation from at least one location over an area of skin under investigation so as to give an indication of papillary dermis thickness over said area;

skin colour co-ordinate measuring means for measuring skin colour co-ordinates at said at least one location over said area of skin;

calculating means for using data obtained in measuring steps (i) and (ii) to calculate corrected skin colour co-ordinates over said area which correspond to a predetermined papillary dermis thickness, and;

colour comparison means for comparing corrected skin colour co-ordinates obtained in step (iii) with a reference colour co-ordinate range for healthy skin of said predetermined papillary dermis thickness.