METHOD AND DEVICE FOR MEASURING THE FLUORESCENCE EMITTED ON THE SURFACE OF A BIOLOGICAL TISSUE

Abstract

The invention relates to a method and device for measuring fluorescence on a surface area of ​​biological tissue using a probe (1). The distance between the surface area of ​​the biological tissue and a fixed point in the probe's coordinate system is determined. This distance is used to calculate the distance between the biological tissue and a fluorescence sensor (10), and to focus this fluorescence sensor (10) on the surface area of ​​the biological tissue. Furthermore, knowing the distance between the fluorescence sensor (10) and the surface area of ​​the biological tissue from which fluorescence is emitted allows for the quantification of this fluorescence.

Description

[069] Results obtained for several observation distances di are reported in the table below: Distances di (mm) Gray level Fi / Fref dref / di2 interpolation error 115 45651 1.89 2.01 6.4% 132 35738 1.48 1.52 3.2% 163 24177 1.00 1.00 0.0% 190 18325 0.76 0.74 2.9% 235 12208 0.50 0.48 4.7% 262 9894 0.41 0.39 5.4% 295 7881 0.33 0.31 6.3%

[070] The values ​​in the table above represent respectively the ratio of the fluorescence intensities and the ratio of the square of the observation distances di, as a function of the observation distance di. By plotting these values ​​on the graph in Figure 7, we see that the curve in follows the same trend as the curve in Fluorescence signal (d;) _ ,, , -----------------------. In addition, 1 error between these two reports is sufficient Fluorescence signal (dref) low, so that we can calculate, with an acceptable error rate (< 10%), the value of the fluorescence intensity using the ratio of the square of the observation distances.

[071] Image Id of Figure 6 corresponds to the fluorescence signal emitters 13 observed with probe 1 at an observation distance of 115mm. Image If of Figure 6 corresponds to the same fluorescence signal emitters 13 observed with probe 1 at an observation distance di equal to 163mm. The image of Figure le corresponds to image Id, produced with an observation distance of 115mm, but corrected as indicated above by taking as reference the fluorescence signal obtained at a reference distance dref equal to 163mm.

[072] By thus correcting the intensity of the detected fluorescence as a function of the observation distance di, it is possible to display in real time a signal whose intensity level is independent of this distance and of the orientation of the probe 1. More generally, this method makes it possible to modulate, on display, the intensity of the detected fluorescence signal as a function of the distance determined between at least the point of the surface area of ​​a biological tissue and the probe 1.

[073] In addition to this real-time display, it is also possible to provide the operator with quantitative information in real time. Knowledge of the fluorescence level of a tissue during an operation can be very useful. For example, this knowledge can be used to assess the perfusion level of a biological tissue.

[074] As indicated above, the device according to the invention can comprise two laser marking sources which make it possible to form a crosshair. It is then possible to detect the fluorescence signal at the center of this cross to obtain a quantitative value of this signal: Fluorescence signal (drep tre^, for a reference distance dre^ and a reference exposure time trep

[075] Thus, from a value of the fluorescence signal detected under particular conditions of use (at a distance dt and during an exposure time tj), it is possible to calculate the value of the intensity of the fluorescence signal Fluorescence signal (d™?, which would have been had in a reference condition (drep tre^: t d2 Fluorescence signal (d™?, = Fluorescence signal (dt, ti) dref

[076] Thus the surgeon has stable quantitative information, whatever the orientation of the probe 1 and the distance which separates the excitation light source 3 from the area of ​​the biological tissue to be observed, and independent of the exposure time.

Claims

Claims 1. Method for measuring fluorescence on a surface area of ​​a biological tissue (9), in which a probe (1) is provided comprising a first optical system (7) comprising a first sensor (10) for detecting fluorescence light emitted on the surface of the biological tissue and a second optical system (8) comprising a second sensor (11) for detecting light in the visible range, the first (10) and second (11) sensors being fixed relative to each other, characterized in that a distance is determined between at least one point (O) of the surface area of ​​the biological tissue (9) and a fixed point in the reference frame of the probe (1), the distance thus determined being used to focus the first optical system (7) on the point (O) of the surface area of ​​the biological tissue (9).

2. Method according to claim 1, in which a fluorescence signal detected by the first sensor (10) is modulated as a function of the distance determined between at least the point of the surface area of ​​the biological tissue and the fixed point in the reference frame of the probe (1).

3. Method according to one of the preceding claims, in which a light mark detectable by the second sensor (11) is projected onto the area of ​​the surface of the biological tissue (9), the position of the image of this mark on the second sensor (11) being used to determine the distance between at least one point of the area on the surface of the biological tissue (9) and the fixed point in the reference frame of the probe (1).

4. Method according to the preceding claim, in which the light mark is placed on the optical axis (A) of the first optical system (7).

5. Method according to one of the preceding claims, in which an excitation light source (3) is provided, the intensity of which is controlled as a function of the distance between at least one point of the surface area of ​​the biological tissue (9) and the fixed point in the reference frame of the probe (1).

6. Device for measuring fluorescence on an area on the surface of a biological tissue (9), this device comprising a probe (1) comprising a first optical system (7) with a first sensor (10) for detecting fluorescence light emitted on the surface of the biological tissue (9) and a second optical system (8) with a second sensor (11) for detecting light in the visible range, the first (10) and second (11) sensors being fixed relative to each other, characterized in that it comprises means for determining the distance between at least one point (O) of the area on the surface of the biological tissue (9) and a fixed point in the frame of reference of the probe (1), and means for focusing the first optical system (7) on this point (O) of the area on the surface of the biological tissue (9), using the determined distance between at least one point (O) of the area on the surface of the biological tissue and the fixed point in the frame of reference of the probe (1).

7. Device according to the preceding claim, in which the sensors (10, 11) have different detection surfaces.

8. Device according to claim 7, wherein the detection surface of the first sensor (10) is at least twice as large as that of the second sensor (11).

9. Device according to claim 8, wherein the first sensor (10) has a dimension greater than 1 inch and the second sensor (11) has a dimension less than 7 / 10 mm (½ inch).

10. Device according to one of claims 6 to 9, in which the first (7) and second (8) optical systems have respective optical axes (A, B) located in the same plane (P).

11. Device according to one of claims 6 to 10, comprising at least one marking light source (5 or 6) emitting in the visible range and adapted to project, onto the area of ​​the surface of the biological tissue (9), a light mark detectable by the second sensor (11) and not by the first (10).

12. Device according to claim 11, in which the marking light source (5 or 6) is fixed relative to the first (10) and second (11) sensors.

13. Device according to claim 11 or 12, comprising two marking light sources (5, 6), each consisting of a laser emitter and being adapted to emit an essentially flat light beam, at a wavelength detectable by the second sensor (11) and not by the first sensor (10), one of the beams passing through the first (A) and second (B) optical axes and being essentially perpendicular to the other, the intersection of the two beams projected onto the surface area of ​​the biological tissue (9) forming a cross centered on the optical axis (A) of the first optical system (7).

14. Device according to one of claims 11 to 13, in which the optical axis (A) of the first optical system (7) passes through the light mark.

15. Device according to claim 14, in which the distance between at least one point (M) of the surface area of ​​the biological tissue (9) and the fixed point in the frame of reference of the probe, used by the focusing means of the first optical system (7), is determined by taking into account the displacement (e) of the optical mark (M) on the image collected by the second sensor (11), as a function of the displacement of the probe (1) relative to the surface area of ​​the biological tissue (9).

16. Device according to one of claims 6 to 15, comprising at least one excitation light source (3) fixed relative to the first (10) and second (11) sensors.

17. Device according to one of claims 6 to 16, in which the means for determining the distance between at least one point (O) of the surface area of ​​the biological tissue (9) and a fixed point in the reference frame of the probe (1) are distinct from an image analysis method.

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