Thermal imaging method and apparatus

Claim 1

A method of measuring blood perfusion in human or animal skin, comprising the steps of: (a) applying a cooling means to an area of skin; (b) removing the cooling means from the area of skin; (c) using an infra-red detector to obtain a first set of thermographic data TD 1 corresponding to skin temperature at a plurality of points on the area of skin at time t 1 ; (d) repeating step (c) at least once to obtain a total of n sets of thermographic data TD 1 to TD n corresponding to times t 1 to t n , where n is at least 2; (e) calculating the coefficients of an exponential fit equation for the variation with time of the thermographic data TD 1 to TD n at each of the plurality of points; and (f) displaying the coefficients of the exponential fit equation in graphical form.

Claim 3

A method according to Claims 1 or 2, wherein n is at least 4, preferably at least 10.

Claim 4

A method according to any preceding Claim, wherein the coefficients of the exponential fit equation are displayed using colour mapping.

Claim 5

A method according to any preceding Claim, wherein the cooling means is a cold object which is placed on the skin.

Claim 6

A method according to any preceding Claim, wherein the method further includes the step of placing a reference object on the area of skin so that the thermographic data TD n is obtained at the same points on the area of skin at each successive repeat of step (c).

Claim 8

A method of processing and displaying data relating to blood perfusion in human or animal skin, comprising the steps of: (a) generating a series of n thermographic image matrices IM 1 to IM n corresponding to times t 1 to t n , each thermographic image matrix comprising temperature data relating to a plurality of points on an area of skin; (b) creating a filter matrix corresponding to a region of interest selected from the area of skin; (c) applying the filter matrix to each thermographic image matrix IM 1 to IM n to obtain an cropped thermographic image matrix IMCR 1 to IMCR n having the value zero for points outside the region of interest; (d) constructing an array AR m for each point m in the region of interest, the array containing temperature data T m at that point corresponding to times t 1 to t n ; (e) for each array AR m performing a regression analysis to calculate the coefficients of the exponential components of the best fit equation T m = T min + Ae at + Be bt + Ce ct where A, a, B, b, C, c are coefficients and T min is the minimum temperature data in each array; (f) constructing a coefficient matrix (Z A , Z a etc.) having as elements a parameter derived from the coefficients (A, a etc.) calculated in step (e) for each point m in the region of interest; and (g) displaying the coefficient matrix as an image.

Claim 11

A method according to any one of Claims 8 to 10, wherein the coefficients of the exponential components are calculated using a curve stripping technique.

Claim 12

A method according to any one of Claims 8 to 11, wherein the minimum temperature data T min in each array is subtracted from each temperature data in the array before calculation of the coefficients.

Claim 13

A method according to any one of Claims 8 to 12, wherein the data corresponding to a first interval of time after cooling is discarded before calculating coefficients.

Claim 15

An apparatus for measuring blood perfusion in human or animal skin, comprising: (a) an infra-red detecting means adapted to obtain periodically a set of thermographic data (TD 1 to TD n ) corresponding to skin temperature at a plurality of points on an area of skin; (b) data storage means adapted to store each set of thermographic data (TD 1 to TD n ); (c) computational means for calculating the coefficients of an exponential fit equation for the variation with time of the thermographic data (TD 1 to TD n ) at each of the plurality of points; and (d) image display means adapted to display the coefficients of the exponential fit equation in graphical form.