MEDICAL SENSOR AND METHOD FOR CALIBRATION

Abstract

A medical capsule with a sensor device comprising a light emitting element and a light detecting element with the sensor device being adapted to detect the presence or non-presence of blood and/or Biliverdin based on the light absorption properties of blood and Biliverdin. The capsule is provided with a casing forming a gap at its outer surface. The light emitting element alternatively emits violet light of a wavelength of about 380-450 nm, green light of a wavelength of about 530-580 nm, and red light of a wavelength of about 620-750 nm, whereas the light detecting element generates a separate sensor signal associated with measured light intensities I.sub.violet, I.sub.green, and I.sub.red of at least each of the wavelength ranges of the light from the light emitting element. By evaluating a quotient I.sub.red/I.sub.green, false-positive detection of blood can be avoided. The present disclosure also relates to a calibration method for said medical capsule.

Claims

1. A medical capsule being equipped with a sensor device comprising at least one light emitting element and at least one light detecting element, the sensor device is adapted to detect the presence or non-presence of blood and/or bile containing Biliverdin on the basis of light absorption properties of blood and Biliverdin, wherein the medical capsule is provided with a recess or gap at its outer surface between the at least one light emitting and the at least one light detecting elements, wherein: the at least one light emitting element emits violet light, green light, and red light, of different wavelength ranges; and the at least one light detecting element generates a separate sensor signal associated with measured light intensities I.sub.violet, I.sub.green and I.sub.red of at least each of the wavelength ranges of the light from the at least one light emitting element.

2. The medical capsule according to claim 1, wherein the light of the at least one emitting element passes through the gap in which it is absorbed, reflected, and/or transmitted to different degrees depending on the content in the gap between the at least one opposing light emitting element and the at least one light detecting element.

3. The medical capsule according to claim 1, wherein the sensor device differentiates the presence of blood from the presence of bile containing Biliverdin by evaluating a quotient I.sub.red/I.sub.green of the measured intensity of red light I.sub.red divided by the measured intensity of green light I.sub.green transmitted to the at least one light detecting element.

4. A calibration method for the medical capsule according to claim 3, wherein a measurement value HI for a likelihood of presence of blood is defined as $\mathrm{HI}=0,5.Math.\log \left(\frac{I_{red}}{I_{\mathrm{violet}}}\right).Math.C,$ wherein C is a correction factor.

5. The calibration method according to claim 4, wherein the correction factor C is defined as C=1 if the quotient I.sub.red/I.sub.green is above a predetermined threshold T, and C<1 if the quotient I.sub.red/I.sub.green is below the predetermined threshold T.

6. The calibration method according to claim 4, wherein the correction factor C is defined as C=1 if the quotient I.sub.red/I.sub.green is above a predetermined threshold T, and C=I.sub.red/I.sub.green.Math.1/T if the quotient I.sub.red/I.sub.green is below the predetermined threshold T.

7. A calibration method for the medical capsule according to claim 3, wherein a measurement value HI for a likelihood of presence of blood is defined as $\mathrm{HI}=0,5.Math.\log \left(\frac{I_{red}}{I_{\mathrm{violet}}+J_{\mathrm{Biliverdin}}}\right),$ wherein J.sub.Biliverdin is a suppression parameter.

8. The calibration method according to claim 7, wherein the suppression parameter J.sub.Biliverdin is defined as J.sub.Biliverdin=0 if the quotient I.sub.red/I.sub.green is above a predetermined threshold T, and J.sub.Biliverdin>0 if the quotient I.sub.red/I.sub.green is below the predetermined threshold T.

9. The calibration method according to claim 7, wherein the suppression parameter J.sub.Biliverdin is defined as J.sub.Biliverdin=0 if the quotient I.sub.red/I.sub.green is above an empirical evaluated blood-threshold T.sub.Blood, and J.sub.Biliverdin=m.sub.Biliverdin.Math.(T.sub.Blood−I.sub.red/I.sub.green) if the quotient I.sub.red/I.sub.green is below or equal the threshold T.sub.Blood, wherein m.sub.Biliverdin is a linear Biliverdin suppression factor.

10. The medical capsule according to claim 1, wherein the at least one light emitting element emits the violet light, the green light, and the red light in a parallel or an alternating manner.

11. The medical capsule according to claim 1, wherein the at least one light emitting element emits the violet light of a wavelength of 380-450 nm and/or the green light of a wavelength of 530-580 nm and/or the red light of a wavelength of 620-750 nm

12. The medical capsule according to claim 1, wherein the at least one light emitting element is provided as a plurality of LEDs that emit the light with the respective wavelengths or as a single LED with a plurality of filters, each associated with the wavelength of the respective light.

13. The medical capsule according to claim 1, comprising a casing with a cylindrical outer shape with rounded end portions and edges, a circuit board located inside the casing with a plurality of electronic facilities and the sensor device.

14. The medical capsule according to claim 13, wherein the recess or gap is orientated rectangular to a longitudinal axis of the medical capsule and a width of the recess or gap extends in the direction of the longitudinal axis of the medical capsule.

15. The medical capsule according to claim 13, wherein the at least one light emitting element and the at least one light detecting element is arranged on top of the circuit board.

16. The medical capsule according to claim 1, wherein the at least one light emitting element generates voltage levels as the separate sensor signal associated with the measured light intensity of the violet, green, and red light.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In the following, the disclosure will be described in greater detail by means of the accompanying drawings. The figures are of a schematic nature only and are intended solely for the purpose of understanding the disclosure.

[0033] FIG. 1 is a schematic view of a medical capsule for detection of blood and/or bile containing Biliverdin according to the disclosure.

[0034] FIG. 2 is a diagram showing the transmission spectroscopy for light of different wavelengths in various blood to water ratios.

[0035] FIG. 3 is a diagram showing the transmission spectroscopy for light of different wavelengths in various bile containing Biliverdin to water ratios.

[0036] FIG. 4 is a diagram showing the quotient I.sub.red/I.sub.green over different concentrations of blood and over different concentrations of bile containing Biliverdin.

DETAILED DESCRIPTION OF THE DRAWINGS

[0037] FIG. 1 shows a frontal view of the medical capsule 1 according to the disclosure. It comprises a light transmitting/permeable casing 2, preferably made of a resin material, with a substantially cylindrical outer shape with rounded end portions and edges in order to make the swallowing process easier. A circuit board 4 with a plurality of electronic facilities (not explicitly shown), e.g. a data memory and/or data transmission member, a CPU, and an energy source like a battery, is located inside the casing 2 of the medical capsule 1. The casing 2 has a lengthy recess or gap 5 being orientated substantially rectangular to the longitudinal axis of the medical capsule 1 at its outer surface while the width of the gap 5 extends in the longitudinal direction of the medical capsule 1. A sensor device 6 comprising at least one light emitting element 8 and at least one light detecting element 9 is located on top of the circuit board 4 in view of FIG. 1. The light emitting element 8 and the light detecting element 9 are arranged in such a way that each element 8, 9 is located on one side of the gap 5 in the casing 2 respectively while also facing each other. The light emitting element 8 emits (preferably monochromatic) light in visual violet (about 415 nm), green (about 570 nm), and red (about 700 nm) range, (respectively) through the gap 5 along the longitudinal direction of the medical capsule 1 which is then being detected by the light detecting element 9 located on the other side of the gap 5, when seen in the width direction of the gap 5 opposite to the light emitting element 8.

[0038] FIG. 2 shows a diagram of the transmission spectroscopy for the light of different wavelengths received by the light detection element 9 for various blood to water ratios. A percentage value of a transmission value through a blood solution compared to a transmission value through clear water, with the percentage value being 100% for a transmission in clear water, is described by the ordinate axis while the abscissa shows different wavelengths for light ranging from 350 nm to 800 nm. Additional vertical lines in the diagram emphasize the characteristic wavelengths for the visual violet (415 nm), green (570 nm), and red (700 nm) light preferably emitted by the light emitting element 8. The diagram of FIG. 2 shows three graphs for blood solutions with three specific blood to water ratios, namely 0.1% (dashed-dotted line), 1% (dashed line), and 5% (solid line). A solution containing blood absorbs a larger amount of violet light with a wavelength in the range of 380 nm to 450 nm which results in a lower transmission value of said light, and therefore, a lower measured intensity I.sub.violet detected by the light detecting element 9. Even for a blood solution with a low blood to water ratio of 0.1%, a significant absorption of violet light is noticeable. The minimum of the dash-dotted line in FIG. 2 shows that the maximal absorption of light occurs at the characteristic wavelength of 415 nm for violet light, which represents a transmission percentage of around 27%. By increasing the wavelength, the transmission percentage increases to a value of around 95% until reaching the wavelength range of green light (530 nm-580 nm) where the transmission percentage drops twice to around 85%. By further increasing the wavelength, the transmission percentage jumps to substantially 100% and stays at this level for the wavelengths 600 nm and higher, meaning almost no red light with a wavelength in the range 620 nm to 750 nm is getting absorbed by the blood solution with a blood to water ratio of 0.1%.

[0039] Similar transmission/absorption characteristics of light can be noticed for the curves representing blood solutions with a blood to water ratio of 1% and 5%. Both curves are shifted in negative y-direction by increasing the ratio of blood to water if compared to the course of the dashed-dotted line described above. A solution with a blood to water ratio of 1% (dashed line) shows a transmission percentage of substantially 0% for violet light and a transmission percentage of around 35% for green light in the characteristic wavelength ranges of 415 nm and 570 nm, respectively, while approximately 95% of red light is being transmitted through said blood solution. A solution with a blood to water ratio of 5% (solid line) shows a transmission percentage of substantially 0% for violet light and 0%-5% for green light in the wavelength ranges of 415 nm and 570 nm, respectively, while approximately 80% of red light is being transmitted. In other words, only 20% of red light but around 95% of green light is being absorbed by the blood solution with a blood to water ratio of 5%.

[0040] FIG. 3 shows a similar diagram of the transmission spectroscopy for the light of different wavelengths received by the light detection element 9 for various bile to water ratios, in which Biliverdin is present. Corresponding to the transmission spectroscopy for blood solutions of FIG. 2, a percentage value of a transmission value through a bile solution compared to a transmission value through clear water, with the percentage value being 100% for a transmission in clear water, is described by the ordinate axis while the abscissa shows different wavelengths for light ranging from 350 nm to 800 nm. The diagram of FIG. 3 shows three graphs for bile solutions, which contain Biliverdin, with three specific bile to water ratios, namely 6.25% (dashed-dotted line), 25% (dashed line), and 100% (solid line). All three graphs for the Biliverdin containing bile solutions show a noticeable decline in the transmission percentage for violet light with a wavelength ranging from 380 nm to 450 nm. A minimum of the light transmission percentage is around 10%, around 57%, and around 87% for the above mentioned bile solutions with bile to water ratios of 100%, 25%, and 6.25%, respectively. The higher the bile to water ratio, the more light is being absorbed. When the wavelength increases, i.e. by leaving the wavelength range of violet light, the light transmission percentage increases and the respective graphs start to flatten at a wavelength of around 525 nm for all three bile solutions. The graphs of FIG. 3 show that the majority of green light as well as red light is not being absorbed by a solution with bile containing Biliverdin, contrary to solutions containing blood. Pure bile with Biliverdin, represented by the solid line, transmits around 90% of green light and around 95% of red light, while the solutions with diluted bile containing Biliverdin absorb substantially no green and red light at all.

[0041] FIG. 4 shows a logarithmic diagram portraying the value of the measured intensity of red light divided by the measured intensity of green light I.sub.red/I.sub.green over a concentration of blood and over a concentration of bile containing Biliverdin. It is assumed that the measured intensity signals for red light and green light are essentially equal when no absorption takes place in the measurement gap 5 of the medical capsule 1, therefore, the quotient I.sub.red/I.sub.green is essentially 1 if the measurement gap 5 of the medical capsule 1 is empty. Due to the low absorption of green light by bile containing Biliverdin, the quotient I.sub.red/I.sub.green remains constantly low (around 1, up to about 2) over all concentrations of bile containing Biliverdin (see the line indicated by black squares in FIG. 4). On the other hand, the quotient I.sub.red/I.sub.green rises significantly with the presence of blood with an increasing concentration of blood (see the line indicated by white circles).

[0042] As the transmission and/or the absorption value of light in the range of visible green light are significantly different for bile containing Biliverdin and for blood, the above discussed value I.sub.red/I.sub.green of the measured intensity of red light divided by the measured intensity of green light is a reliable means to exploit these characteristics as differentiation features between Biliverdin and blood in order to differentiate the presence of blood from the presence of bile containing Biliverdin and thereby avoiding the risk of false-positively detecting blood.