Extravasation detection apparatus and method based on optical sensing

• US 6,487,428 B1
• Filed: 08/31/2000
• Issued: 11/26/2002
• Est. Priority Date: 08/31/2000
• Status: Expired due to Fees

• Current Assignee: Trustees Of The University Of Pennsylvania (University of Pennsylvania)
• Original Assignee: Trustees Of The University Of Pennsylvania (University of Pennsylvania)
• Inventors: Yodh, Arjun G., Culver, Joseph P.
• Primary Examiner(s): Shaver, Kevin
• Assistant Examiner(s): Kremer, Matthew
• Application Number:
  US09/652,757
• Time in Patent Office: 817 Days
• Field of Search: 600/309-310, 600/335, 600/454, 600/473, 600/474, 600/476, 600/475, 604/290, 604/500-512
• US Class Current: 600/310
• CPC Class Codes: A61B 5/0073 by tomography, i.e. reconstruction of 3D images from 2D projections A61B5/0066 takes precedence
• CPC Class Codes: A61B 5/0084 for introduction into the body, e.g. by catheters A61B5/1459 takes precedence

Abstract

Extravasation of a fluid applied to a patient is determined by monitoring light transmitted through the tissue of the patient in proximity to a site at which the fluid is being injected. Light is radiated from a plurality of light sources in an encoded manner into the body part at the site at which the fluid is injected and the light that is reflected, scattered, diffused or otherwise emitted from the body part is detected individually by a plurality of light detectors. Signals representative of the detected light are developed and, prior to injection of the fluid, references are developed against which measurements made during injection of the fluid are compared. New light signals having an improved signal-to-noise ratio are developed from the comparisons of the detected light signals with the associated reference signals. Prior to injection of the fluid into the body part, a model, dependent on the arrangement of the light sources and the light detectors on the support pad is developed for calculating extravasation volume from the new light signals having an is improved signal-to-noise ratio. The new light signals having an improved signal-to-noise ratio are combined according to the model to determine the volume of extravasation and the volume of extravasation is compared with a prescribed level of extravasation.

Claims

1. Extravasation detection apparatus comprising:

a support pad adapted for attachment to a body part of a patient in proximity to a site at which a fluid is to be injected into the patient;

a plurality of light sources, mounted to said support pad, for radiating light into the body part;

means for energizing said light sources in an encoded manner to radiate light into the body part in an encoded manner;

a plurality of light detectors, mounted to said support pad, for;

(a) individually detecting light transmitted from said light sources that is reflected, scattered, diffused or otherwise emitted from the body part, and

(b) individually developing light source/light detector pair signals representative of the light detected individually by said light detectors;

means for developing, prior to injection of the fluid into the body part, a plurality of individual light source/light detector pair baseline signals associated with each light source/light detector pair and against which measurements made during injection of the fluid into the body part are compared;

means for comparing the light source/light detector pair signals with the associated light source/light detector pair baseline signals;

means for developing from the comparisons of the light source/light detector pair signals with the associated light source/light detector pair baseline signals new light source/light detector pair signals having an improved signal-to-noise ratio;

means for developing, prior to injection of the fluid into the body part, a model, dependent on the arrangement of said light sources and said light detectors on said support pad, for calculating extravasation volume from the new light source/light detector pair signals having an improved signal-to-noise ratio;

means for combining, according to the extravasation model, the new light source/light detector signals having an improved signal-to-noise ratio to determine the volume of extravasation; and

means for comparing the volume of extravasation with a prescribed level of extravasation.

2. Extravasation detection apparatus according to claim 1 wherein the extravasation model also is dependent upon tissue optical properties of the body part into which the fluid is injected.

3. Extravasation detection apparatus according to claim 2 wherein the means for developing the extravasation model include:

(a) means for developing, prior to injection of the fluid into the body part, signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio from sources other than the patient,

(b) means for calculating a parameter-dependent extravasation volume from the signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio, and

(c) means for determining the parameters of the parameter-dependent extravasation volume by making, prior to injection of the fluid into the body part, in vivo measurements of known extravasation volumes in the sources other than the patient.

4. Extravasation detection apparatus according to claim 3 wherein the means for calculating a parameter-dependent extravasation volume from the signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio include:

(a) means for developing a sum signal that is the sum of the magnitudes of the new light source/light detector pair signals having an improved signal-to-noise ratio, and

(b) means for multiplying the sum signal by a correction factor corresponding to an empirically determined parameter to correct for model inaccuracies.

5. Extravasation detection apparatus according to claim 3 wherein the means for calculating a parameter-dependent extravasation volume from the signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio include:

(a) means for selecting separate coefficients for;

(1) positive values of the new light source/light detector pair signals having an improved signal-to-noise ratio, and

(2) negative values of the new light source/light detector pair signals having an improved signal-to-noise ratio,

(b) means for multiplying;

(1) positive new light source/light detector pair signals having an improved signal-to-noise ratio by the positive value coefficients, and

(2) negative new light source/light detector pair signals having an improved signal-to-noise ratio by the negative value coefficients,

(c) means developing a sum signal of the new light source/light detector pair signals having an improved signal-to-noise ratio multiplied by the positive value coefficients and the new light source/light detector pair signals having an improved signal-to-noise ratio multiplied by the negative value coefficients, and

(d) means for multiplying the sum signal by a correction factor corresponding to an empirically determined parameter to correct for model inaccuracies.

6. Extravasation detection apparatus according to claim 3 wherein the tissue optical properties of the body part include absorption and scattering and the means for calculating a parameter-dependent extravasation volume from the signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio include:

(a) means for combining the new light source/light detector pair signals having an improved signal-to-noise ratio into a differential absorption image representative of the change in the spatially variant absorption from baseline,

(b) means for combining the new light source/light detector pair signals having an improved signal-to-noise ratio into a differential scattering image representative of the change in the spatially variant scattering from baseline,

(c) means for developing a sum absorption signal by performing a volume sum of the differential absorption image,

(d) means for developing a sum scattering signal by performing a volume sum of the differential scattering image,

(e) means for multiplying the sum absorption signal by a first correction factor corresponding to an empirically determined parameter to correct for model inaccuracies,

(f) means for multiplying the sum scattering signal by a correction factor corresponding to an empirically determined parameter to correct for model inaccuracies, and

(g) means for adding the result of multiplying the sum absorption signal by a first correction factor corresponding to an empirically determined parameter to correct for model inaccuracies and the result of multiplying the sum scattering signal by a second correction factor corresponding to an empirically determined parameter to correct for model inaccuracies.

7. Extravasation detection apparatus comprising:

a support pad adapted for attachment to a body part of a patient in proximity to a site at which a fluid is to be injected into the patient;

a plurality of light sources, mounted to said support pad, for radiating light into the body part;

means for energizing said light sources in an encoded manner to radiate light into the body part in an encoded manner;

a plurality of light detectors, mounted to said support pad, for;

(a) individually detecting light transmitted from said light sources that is reflected, scattered, diffused, or otherwise emitted from the body part, and

(b) individually developing light source/light detector pair signals representative of the light detected individually by said light detectors;

means for supplying a plurality of individual light source/light detector pair baseline signals associated with each said light source/light detector pairs and developed prior to injection of the fluid into the body part;

means for comparing the light source/light detector pair signals with the associated light source/light detector pair baseline signals;

means for developing, from the comparisons of the light source/light detector pair signals with the associated light source/light detector pair baseline signals, new light source/light detector pair signals having an improved signal-to-noise ratio;

means for supplying a model, dependent on the arrangement of said light sources and said light detectors on said support pad and developed prior to injection of the fluid into the body part for calculating extravasation volume;

means for combining, according to the extravasation model, the new light source/light detector pair signals having an improved signal-to-noise ratio to determine the volume of extravasation; and

means for comparing the determined volume of extravasation with a prescribed level of extravasation.

8. Extravasation detection apparatus according to claim 7 wherein the extravasation model also is dependent upon tissue optical properties of the body part into which the fluid is injected.

9. A method for detecting extravasation of a fluid applied to a patient comprising the steps of:

attaching a support pad to a body part of a patient in proximity to a site which a fluid is to be injected into the patient;

radiating, in an encoded manner into the body part at the site at which he fluid is injected into the patient, light from a plurality of light sources mounted to aid support pad;

detecting light transmitted from said light sources that is reflected, scattered, diffused or otherwise emitted from the body part individually by a plurality of light detectors mounted to said support pad;

developing a plurality of light source/light detector pair signals representative of the light detected individually by said light detectors for each of said light sources;

developing, prior to injection of the fluid into the body part, a plurality of individual light source/light detector pair baseline signals associated with each said light source/light detector pairs and against which measurements made during injection of the fluid into the body part are compared;

developing from comparisons of the light source/light detector pair signals with the light source/light detector pair baseline signals new light source/light detector pair signals having an improved signal-to-noise ratio;

developing, prior to injection of the fluid into the body part, an extravasation model, dependent on the arrangement of said light sources and said light detectors on said support pad, for calculating extravasation volume from the new light source/light detector pair signals having an improved signal-to-noise ratio;

combining, according to the extravasation model, the new light source/light detector pair signals having an improved signal-to-noise ratio to determine the volume of extravasation; and

comparing the determined volume of extravasation with a prescribed level of extravasation.

10. A method for detecting extravasation of a fluid applied to a patient according to claim 9 wherein the extravasation model also is dependent upon tissue optical properties of the body part into which the fluid is injected.

11. A method for detecting extravasation of a fluid applied to a patient according to claim 10 wherein the step of developing the extravasation model includes:

(a) developing, prior to injection of the fluid into the body part, signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio from sources other than the patient,

(b) calculating a parameter-dependent extravasation volume from the signals similar to the new light source/light detector pair signals having an improved signal-to-noise ratio, and

(c) determining the parameters of the parameter-dependent extravasation volume by making, prior to injection of the fluid into the body part, in vivo measurements of known extravasation volumes in the sources other than the patient.

12. A method for detecting extravasation of a fluid applied to a patient according to claim 11 wherein the step of developing the new light source/light detector pair signals having an improved signal-to-noise ratio includes:

(a) developing baseline differential light source/light detector pair signals by one of;

(1) the difference between each light source/light detector pair signal and the associated light source/light detector pair baseline signal, and

(2) the log of each light source/light detector pair signal divided by the associated light source/light detector pair baseline signal, and

(b) processing the baseline differential light source/light detector pair signals into the new light source/light detector pair signals having an improved signal-to-noise ratio by at least one of;

(1) multiplying each baseline differential light source/light detector pair signal by the signal-to-noise ratio in the associated light source/light detector pair baseline signal,

(2) removing signal components from each baseline differential light source/light detector pair signal that correlate with other light source/light detector pair signals, and

(3) removing signal components from each baseline differential light source/light detector pair signal that correlate with physiologic functions of the patient.

13. A method for detecting extravasation of a fluid applied to a patient according to claim 12 wherein the step of calculating a parameter-dependent extravasation volume includes:

(a) developing a sum signal that is the sum of the magnitudes of the new light source/light detector pair signals having an improved signal-to-noise ratio, and

(b) multiplying the sum signal by a correction factor corresponding to an empirically determined parameter to correct for model inaccuracies.

14. A method for detecting extravasation of a fluid applied to a patient according to claim 12 wherein the step of calculating a parameter-dependent extravasation model includes:

(a) selecting separate coefficients for;

(1) positive values of the new light source/light detector pair signals having an improved signal-to-noise ratio, and

(2) negative values of the new light source/light detector pair signals having an improved signal-to-noise ratio,

(b) multiplying;

(1) positive new light source/light detector pair signals having an improved signal-to-noise ratio by the positive value coefficients, and

(2) negative new light source/light detector pair signals having an improved signal-to-noise ratio by the negative value coefficients,

(c) developing a sum signal of the new light source/light detector pair signals having an improved signal-to-noise ratio multiplied by the positive value coefficients and the new light source/light detector pair signals having an improved signal-to-noise ratio multiplied by the negative value coefficients, and

(d) multiplying the sum signal by a correction factor corresponding to an empirically determined parameter to correct for model inaccuracies.

15. A method for detecting extravasation of a fluid applied to a patient according to claim 12 wherein:

(a) the tissue optical properties of the body part include absorption and scattering, and

(b) the step of calculating a parameter-dependent extravasation model includes;

(1) combining the new light source/light detector pair signals having an improved signal-to-noise ratio into a differential absorption image representative of the change in the spatially variant absorption from baseline,

(2) combining the new light source/light detector pair signals having an improved signal-to-noise ratio into a differential scattering image representative of the change in the spatially variant scattering from baseline,

(3) developing a sum absorption signal by performing a volume sum of the differential absorption image,

(4) developing a sum scattering signal by performing a volume sum of the differential scattering image,

(5) multiplying the sum absorption signal by a first correction factor corresponding to an empirically determined parameter to correct for model inaccuracies,

(6) multiplying the sum scattering signal by a second correction factor corresponding to an empirically determined parameter to correct for model inaccuracies, and

(7) adding the result of multiplying the sum absorption signal by a first correction factor corresponding to an empirically determined parameter to correct for model inaccuracies and the result of multiplying the sum scattering signal by a second correction factor corresponding to an empirically determined parameter to correct for model inaccuracies.

16. Extravasation detection apparatus comprising:

a support pad adapted for attachment to a body part of a patient in proximity to a site at which a fluid is to be injected into the patient;

at least one light source, mounted to said support pad, for radiating light into the body part;

means for energizing said light source in an encoded manner to radiate light into the body part in an encoded manner;

a plurality of light detectors, mounted to said support pad, for;

(a) individually detecting light transmitted from said light source that is reflected, scattered, diffused or otherwise emitted from the body part, and

(b) individually developing light source/light detector pair signals representative of the light detected individually by said light detectors;

means for developing, prior to injection of the fluid into the body part, a plurality of individual light source/light detector pair baseline signals associated with each light source/light detector pair and against which measurements made during injection of the fluid into the body part are compared;

means for comparing the light source/light detector pair signals with the associated light source/light detector pair baseline signals;

means for developing from the comparisons of the light source/light detector pair signals with the associated light source/light detector pair baseline signals new light source/light detector pair signals having an improved signal-to-noise ratio;

means for developing, prior to injection of the fluid into the body part, a model, dependent on the arrangement of said light source and said light detectors on said support pad, for calculating extravasation volume from the new light source/light detector pair signals having an improved signal-to-noise ratio;

means for combining, according to the extravasation model, the new light source/light detector signals having an improved signal-to-noise ratio to determine the volume of extravasation; and

means for comparing the volume of extravasation with a prescribed level of extravasation.

17. Extravasation detection apparatus comprising:

a support pad adapted for attachment to a body part of a patient in proximity to a site at which a fluid is to be injected into the patient;

a plurality of light sources, mounted to said support pad, for radiating light into the body part;

means for energizing said light sources in an encoded manner to radiate light into the body part in an encoded manner;

at least one light detector, mounted to said support pad, for;

(a) individually detecting light transmitted from said light sources that is reflected, scattered, diffused or otherwise emitted from the body part, and

(b) individually developing light source/light detector pair signals representative of the light detected individually by said light detector;

means for developing, prior to injection of the fluid into the body part, a plurality of individual light source/light detector pair baseline signals associated with each light source/light detector pair and against which measurements made during injection of the fluid into the body part are compared;

means for comparing the light source/light detector pair signals with the associated light source/light detector pair baseline signals;

means for developing from the comparisons of the light source/light detector pair signals with the associated light source/light detector pair baseline signals new light source/light detector pair signals having an improved signal-to-noise ratio;

means for developing, prior to injection of the fluid into the body part, a model, dependent on the arrangement of said light sources and said light detector on said support pad, for calculating extravasation volume from the new light source/light detector pair signals having an improved signal-to-noise ratio;

means for combining, according to the extravasation model, the new light source/light detector signals having an improved signal-to-noise ratio to determine the volume of extravasation; and

means for comparing the volume of extravasation with a prescribed level of extravasation.