DEVICE AND METHOD FOR DETERMINING RESIDUAL BLOOD IN A DIALYSER AND DIALYSIS SYSTEM

Abstract

The present invention relates to a device (1) and a corresponding method for determining residual blood in a dialyzer (2) comprising a holding device (6) configured to accommodate a dialyzer (2), an image capturing device (7) configured to capture at least one image of a dialyzer (2) accommodated by the holding device (6), in particular a filter (4) located in the dialyzer (2), and generate corresponding image data having a plurality of image points, each of which assigned at least one respective intensity value, in particular a color value, and a control device (9) configured to determine residual blood information characterizing the presence and/or content of residual blood in the dialyzer (2) on the basis of a statistical frequency of at least a portion of the intensity values in the at least one image. The invention further relates to a dialysis system having such a device (1).

Claims

1. A device for determining residual blood in a dialyzer comprising a holding device configured to accommodate a dialyzer, an image capturing device configured to capture at least one image of a dialyzer accommodated by the holding device, and generate corresponding image data having a plurality of image points, each of which assigned at least one respective intensity value, and a control device configured to determine residual blood information characterizing the presence and/or content of residual blood in the dialyzer on the basis of a statistical frequency of at least a portion of the intensity values in the at least one image.

2. The device according to claim 1, wherein the image capturing device is configured to capture electromagnetic radiation at two or more different wavelengths and generate intensity values, for each of the wavelengths per each image point, and the control device is configured to determine the residual blood information on the basis of a statistical frequency of the intensity values for one or more of the wavelengths in the at least one image.

3. The device according to claim 1, wherein the control device is configured to determine the residual blood information on the basis of a distribution of the frequency, of the intensity values in the at least one image.

4. The device according to claim 3, wherein the control device is configured to determine the residual blood information on the basis of at least one parameter characterizing a characteristic of the distribution of the frequency of the intensity values in the at least one image.

5. The device according to claim 4, wherein the at least one parameter is given by the expected value of the intensity values and/or the centroid of the distribution of the frequency of the intensity values.

6. The device according to claim 4, wherein the at least one parameter is given by an intensity value (I.sub.max) at which the distribution of the frequency of the intensity values exhibits a maximum.

7. The device according to claim 4, wherein the at least one parameter is given by an intensity value (I.sub.max) at which the distribution of the frequency of the intensity values is divided into two equal areas.

8. The device according to claim 4, wherein the at least one parameter characterizes the width of the distribution of the frequency of the intensity values.

9. The device according to claim 8, wherein the at least one parameter characterizes at least one of the following: the standard deviation of the intensity values from the expected value, the variance of the intensity values, a range between two intensity values (cut-on, cut-off) at which the progression of the distribution of the frequency exceeds and/or reaches a preset threshold, in particular zero.

10. The device according to claim 4, wherein the at least one parameter characterizes the slope of the distribution of the frequency of the intensity values.

11. The device according to claim 4, wherein the at least one parameter characterizes the kurtosis of the distribution of the frequency of the intensity values.

12. A dialysis system comprising the device according to claim 1 and a dialysis device able to be connected to a dialyzer by tubes and configured to conduct blood and dialysate through the dialyzer to cleanse the blood.

13. A method for determining residual blood in a dialyzer comprising the following steps: capturing at least one image of a dialyzer, and generating corresponding image data having a plurality of image points, each of which assigned at least one respective intensity value, and determining residual blood information characterizing the presence and/or content of residual blood in the dialyzer on the basis of a statistical frequency of at least a portion of the intensity values in the at least one image.

14. The method according to claim 13, wherein the residual blood information is further determined in consideration of calibration data obtained by means of a calibration process which comprises the following steps: capturing images of two or more dialyzers, and generating corresponding image data having a plurality of pixels, each of which associated with at least one intensity value, and generating calibration data based on information on the respective different amounts of residual blood contained in the dialyzers and an analysis of the statistical frequency of at least part of the intensity values in the respectively captured images.

15. The device according to claim 1, wherein said holding device is a filter located in the dialyzer.

16. The device of claim 1, wherein said intensity value is a color value.

17. The device of claim 2, wherein said intensity values are two or more color values.

18. The device of claim 3, wherein said distribution of the frequency is a histogram.

19. The method of claim 13, wherein said at least one image of the dialyzer is an image of a filter located in the dialyzer, and the intensity value is a color value.

20. The method of claim 14, wherein said images of two or more dialyzers are images of filters located within the two or more dialyzers containing different amounts of residual blood, and the at least one intensity value is at least one color value.

Description

[0026] Further advantages, features and possible applications of the present invention are yielded by the following description in conjunction with the figures. Shown are:

[0027] FIG. 1 one example of a device for determining residual blood in a dialyzer;

[0028] FIG. 2 a first example of a distribution of the frequency of intensity values in an image of a dialyzer filled with NaCl; and

[0029] FIG. 3 a second example of a distribution of the frequency of intensity values in an image of a dialyzer filled halfway with blood;

[0030] FIG. 4 a third example of a distribution of the frequency of intensity values in an image of a dialyzer filled completely with blood;

[0031] FIG. 5 a graphic representation of one example of calibration data; and

[0032] FIG. 6 a graphic representation to illustrate different parameters for characterizing a distribution of the frequency of intensity values.

[0033] FIG. 1 shows an example of a device 1 for determining residual blood in a dialyzer 2 in a schematic side view. The dialyzer 2 comprises a substantially cylindrical shell 3 of a preferably transparent material such as for instance plastic or glass. On both ends of the shell 3, there are provided end caps 5 at which respective connectors 5a and 5b are located, at which blood and dialysate can be conducted into or respectively out of the interior of the dialyzer 2 when they are connected to corresponding connectors of a dialysis device 10 by (not shown) tubes.

[0034] A filter 4 is located within the dialyzer 2, or shell 3 respectively, which in the depicted example comprises a plurality of only schematically indicated hollow fibers of a semipermeable material. During the dialysis procedure, the blood to be cleansed is conducted inside the hollow fibers while they are flushed from the outside with dialysate.

[0035] In the depicted example, the dialyzer 2 is situatede.g. after finishing a dialysis procedure or after being separated from the dialysis device 10 respectivelyin a holding device comprising two bearing elements 6 having semi-cylindrical recesses in which the dialyzer 2 is in particular rotatably mounted.

[0036] An image capturing device 7, for example a still-frame and/or video camera, is provided in the interior of one of the bearing elements 6, depicted in cross section, which is capable of taking one or more images of a detail of the dialyzer 2 or the filter 4 respectively in the region of the bearing element 6. Preferably, a camera chip serves as the image capturing device 7.

[0037] Preferably, an illumination device 8 is further provided, e.g. one or more light emitting diodes, by means of which the relevant detail of the dialyzer 2 or respectively filter 4 is illuminated at least during the capturing of the image.

[0038] A rotatable mounting of the dialyzer 2 in the bearing elements 6 can provide for multiple images of the dialyzer 2 to be successively taken at different rotational positions. The taking of a panoramic image can in particular be provided for by rotating the dialyzer 2.

[0039] The image capturing device 7 is preferably designed to capture color images and has, for example, three color channels in the red (R), green (G) and blue (B) wavelengths or respectively wavelength ranges.

[0040] Each image of the dialyzer 2 or respecitvely filter 4 taken by the image capturing device 7 has a plurality of image points, so-called pixels, each associated with at least one intensity value, in particular three different color values for the R, G and B color channels.

[0041] The image data generated by the image capturing device 7 is fed to a control device 9 and analyzed there in order for conclusions to be able to be drawn about any residual blood in the filter 4.

[0042] At least part of the color values are thereby analyzed in terms of their frequency, in particular in terms of their frequency distribution, in the respective image and corresponding residual blood information derived therefrom which indicates whether or respectively how much residual blood is present in the filter 4.

[0043] The residual blood information can be solely of a qualitative nature, e.g. residual blood present/no residual blood present or else contain quantitative information on the residual blood content, e.g. in the form of a rough indication of the residual blood content (e.g. high, average, low) and/or also even be in the form of numerical values (e.g. weight percent, volume percent, absolute concentration values, information on the so-called streaking of the filter).

[0044] The residual blood information is preferably determined in consideration of at least one parameter characterizing at least one characteristic of the frequency distribution of at least one of the color values. Preferably, predetermined calibration data, in which one or more characteristics of the frequency distribution is/are correlated with the blood content, is thereby additionally factored in. This will be described in greater detail in the following.

[0045] FIG. 2 shows a first example of a distribution of the frequency of intensity values in an RGB image of a dialyzer filled with NaCl. The graphic representation depicted is a so-called histogram in which the absolute frequency in the form of the number of image points (so-called pixel count) in the respectively captured image is plotted over the intensity values or respectively color values occurring in the image in the individual red (R), green (g) and blue (B) color channels.

[0046] FIG. 3 shows a second example of a distribution of the frequency of intensity values in an RGB image of a dialyzer filled halfway with blood. In contrast to the color value distributions in the different channels shown in FIG. 2, the distributions in FIG. 3 are broader. The distributions among the different R, G and B channels also show greater differentiation than in FIG. 2.

[0047] FIG. 4 shows a third example of a distribution of the frequency of intensity values in an image of a dialyzer completely filled with blood. In contrast to the color value distributions in the different channels shown in FIGS. 2 and 3, the distributions in FIG. 4 are more symmetrical and considerably sharper. Furthermore, a clear shift of the so-called centroid of the distributions is discernible in the different R, G and B channels.

[0048] In the context of calibrating the device 1, or the corresponding method respectively, the centroid of the frequency distributions can for example be determined and correlated with the respective blood content. The position of the centroid x.sub.s of a distribution f(x) along the x-axis is defined as follows:

[00001]$x_s=\frac{{}_a^b.Math.x.Math.f\left(x\right).Math.\mathrm{dx}.Math.}{{}_a^b.Math.f\left(x\right).Math.\mathrm{dx}}=\frac{I_1}{I_2}$

[0049] To perform a calculation with discrete intensity values (x-axis) and frequency values (y-axis), the equation is adjusted as follows:

[00002]$x_s=\frac{\underset{i=0}{\overset{255}{.Math.}}.Math..Math.{}_{x_i}^{x_{i+1}}.Math.x.Math.f\left(x\right).Math.\mathrm{dx}}{\underset{i=0}{\overset{255}{.Math.}}.Math..Math.{}_{x_i}^{x_{i+1}}.Math.f\left(x\right).Math.\mathrm{dx}}=\frac{I_1}{I_2}$

[0050] Then obtained is:

[00003]$\mathrm{with}.Math..Math.f\left(x\right).Math..Math.\left\{x{x}_{i}x{x}_{i+1}\right\}=\mathrm{const}=\mathrm{Fw}\left(i\right)$$I_1=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.{\left[\frac{1}{2}.Math.\mathrm{Fw}\left(i\right).Math.x\right]}_{x_i}^{x_{i+1}}=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\frac{1}{2}.Math.\mathrm{Fw}\left(i\right).Math.\left(x_{i+1}^2-x_i^2\right)$$\mathrm{with}.Math..Math.x_{i+1}=x_i+1$$I_1=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\frac{1}{2}.Math.\mathrm{Fw}\left(i\right).Math.\left(x_{i+1}^2-x_i^2\right)=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\frac{1}{2}.Math.\mathrm{Fw}\left(i\right).Math.\left({\left(x_i+1\right)}^2-x_i^2\right)$$I_1=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\frac{1}{2}.Math.\mathrm{Fw}\left(i\right).Math.\left(x_i^2+2.Math.x_i+1-x_i^2\right)$$I_1=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\mathrm{Fw}\left(i\right).Math.\left(x_i+\frac{1}{2}\right)$$I_2=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.{\left[\mathrm{Fw}\left(i\right).Math.x\right]}_{x_i}^{x_{i+1}}=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\mathrm{Fw}\left(i\right).Math.\left(x_i+1-x_i\right)$$I_2=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\mathrm{Fw}\left(i\right)$$x_s=\frac{\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\mathrm{Fw}\left(i\right).Math.\left(x_i+\frac{1}{2}\right)}{\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\mathrm{Fw}\left(i\right)}$

[0051] This equation corresponds to a determination of the centroid from the (absolute) histogram data. It is also possible to determine the centroid x.sub.s from (relative) histogram data:

[00004]$x_s=\underset{i=0}{\overset{255}{.Math.}}.Math..Math.\mathrm{Fw}\left(i\right).Math.h_n\left(i\right)$$h_n=\mathrm{relative}.Math..Math.\mathrm{frequency}.Math.$

[0052] A determination of the centroid is also possible from raw pixel data:

[00005]$x_s=\stackrel{\_}{x}=\frac{1}{i}.Math.\underset{i=0}{\overset{255}{.Math.}}.Math..Math.p\left(i\right)$$p\left(i\right).Math.\text{:}.Math..Math.\mathrm{pixel}.Math..Math.\mathrm{count}.Math..Math.\left\{p0x255\right\}.Math.$

[0053] A correlation can in this way be made between the intensity/color value in the respective centroid on the one hand and the different dialyzer blood fillings on the other from the distributions of the different color values shown as examples in FIGS. 2 to 4.

[0054] The calibration data thereby obtained for a specific dialyzer/filter type is illustrated graphically in FIG. 5. As is apparent from the illustration, the centroid intensity values obtained for the green (G) color channel vary particularly markedly as a function of the respective blood content. The same also applies, although in somewhat less pronounced form, to the blue (B) color channel.

[0055] Therefore, when determining the residual blood in such a dialyzer, preferably the frequency distribution, or the respective centroid, is identified for the green and/or blue and/or red color channel. By comparing the intensity value of the centroid thereby obtained to the calibration data for the green and/or blue and/or red color channel, a conclusion can then be drawn as to the residual blood content in the dialyzer. Using the green color channel is preferential.

[0056] Preferably, the intensity value and blood content value pair respectively obtained in the calibration, as shown in FIG. 5, is linearly interpolated and/or extrapolated so that the residual blood content can also be determined for amounts of blood which are between, below and/or above the amounts of blood considered in the calibration.

[0057] Alternatively or additionally, it is also possible to accordingly determine the respective centroid of the frequency distributions shown in FIGS. 2 to 4 along the y-axis (frequency) and incorporate same into the determination of residual blood. In this case, a correlation between the, in particular absolute, frequency of the intensity values and the blood content is accordingly made in the calibration procedure.

[0058] While the centroid of the distributions along the x-axis represents a measure of the blood content-dependent shift of the frequency distributions of the intensity values, the centroid along the y-axis characterizes their weighting.

[0059] Alternatively or additionally to the centroid or expected value respectively, however, other characteristics of the frequency distributions can also be considered in the residual blood determination / calibration such as, for example, the width, slope and/or kurtosis of the respective distribution, the intensity value or color value at which the frequency distribution exhibits a maximum and/or the intensity values, so-called cut-on/cut-off values, at which the respective distribution passes out of or respectively again reaches the zero line.

[0060] FIG. 6 shows a graphic representation of an image's frequency distribution of intensity values to illustrate different parameters for the characterizing of the distribution characteristics.

[0061] The dashed line drawn at intensity value I.sub.1/2 divides the area formed by the frequency distribution over the x-axis into two equal areas. The intensity value I.sub.1/2 can, alternatively or additionally to the centroid/expected value, likewise be used in the determining of residual blood.

[0062] The two cut-on and cut-off points characterize the intensity and/or frequency values over the course of the frequency distribution at which the intensity exceeds or again reaches the zero value. The corresponding intensity values can, alternatively or additionally to the above-described parameters, likewise be used in the determining of residual blood.

[0063] The same also applies accordingly to the Max point, which characterizes the most frequently occurring intensity value I.sub.max or, respectively, the frequency of said intensity value I.sub.max.