Internal Bleeding Detection Apparatus

• US 20100049077A1
• Filed: 12/28/2006
• Published: 02/25/2010
• Est. Priority Date: 12/23/2005
• Status: Active Grant

• Current Assignee: E.I.T. Pty., Ltd.
• Original Assignee: E.I.T. Pty., Ltd.
• Inventors: Duncan, Andrew, Sadleir, Rosalind
• Granted Patent: US 8,768,429 B2
• Time in Patent Office: Days
• US Class Current: 600/547
• CPC Class Codes: A61B 5/0002 Remote monitoring of patients using telemetry, e.g. transmission of vital signals via a communication network A61B5/07 takes precedence; transmission systems for measured values G08C; transmission H04B; transmission of digital information H04L; wireless communication networks H04W
• CPC Class Codes: A61B 5/02042 Determining blood loss or bleeding, e.g. during a surgical procedure
• CPC Class Codes: A61B 5/053 Measuring electrical impedance or conductance of a portion of the body
• CPC Class Codes: A61B 5/0536 Impedance imaging, e.g. by tomography
• CPC Class Codes: A61B 5/0537 Measuring body composition by impedance, e.g. tissue hydration or fat content
• CPC Class Codes: A61B 5/6831 Straps, bands or harnesses

Abstract

Abstract: An EIT system (1) adapted to detect internal bleeding in a body portion, the EIT system (1) comprising a plurality of electrodes (3) adapted in use to extend in a substantially linear orientation across one side only of the body portion and to be applied in electrical contact with the skin of the body portion, a current source adapted to cyclically apply an electric current between one pair of the electrodes (3), a voltage measuring means to measure the voltage across each of the other pairs of the electrodes resulting from the current, a data collection system (2) and a data analysis system (4) to analyse data resulting from the voltages that are measured by the voltage measuring means, wherein the analysis system (4) is configured to obtain quantitative information related to amounts and rates of conductive tissue changes occurring in the body, based on an EIT analysis equivalent to that obtained from data derived from electrodes spaced around the full perimeter of the body portion. Also disclosed is an electrode belt suitable for bioelectrical use and in particular for detection of change of volume of tissue in a body portion.

Claims

1. An EIT system adapted to detect changes in tissue volume in a body portion, the EIT system comprising a plurality of electrodes adapted in use to extend in a substantially linear orientation across one surface only of the body portion and to be applied in electrical contact with the skin of the body portion, a current source adapted to cyclically apply an electric current between one pair of the electrodes, a voltage measuring means to measure the voltage across each of the other pairs of the electrodes resulting from the current, a data collection system and a data analysis system to analyse data resulting from the voltages that are measured by the voltage measuring means, wherein the analysis system is configured to obtain quantitative information related to amounts and rates of conductive tissue changes occurring in the body, based on an EIT analysis equivalent to that obtained from data derived from electrodes spaced around the full perimeter of the body portion.

2. An EIT system as claimed in claim 1 wherein the processing means establishes a model of the body portion under analysis comprising a plurality of elements and wherein a parameter representative of an electric field present in each element resulting from the current is calculated from the voltages that are measured and wherein the values of at least a portion of the parameters that are calculated for the elements are amended to substantially reconstruct values that would be obtained from measurements of voltages around the perimeter of the body portion and wherein the change of value of the parameter in a portion of elements over time is indicative of change in tissue volume within the body portion.

3. An EIT system as claimed in claim 2 wherein the data analysis system implements a series of steps to reconstruct the parameter values of the elements, the steps comprising:

calculate the difference between a reference data set and a measured data set of the voltages as measured to establish a vector;

multiply the data set by a reconstruction matrix to obtain a reconstructed image having a plurality of pixels;

integrate the values of the pixels in the reconstructed image to obtain a value of the parameter; and

monitor change in the value of the parameter over a period of time to provide an indication of change in tissue volume.

4. An EIT system as claimed in claim 1 wherein a detected change in tissue volume is representative of internal bleeding.

5. An EIT system as claimed in claim 4 wherein the parameter is defined as Resistivity Index calculated in accordance with one of:

6. An EIT system as claimed in claim 5 wherein the data analysis system further implements the steps of:

using empirical sensitivity calibration to provide an estimate of the parameter in terms of blood volume;

dividing the estimated blood volume by time interval between reference and measured data sets to provide an estimate of the rate of bleeding;

applying a spatial filter to produce a resistivity index that is independent of bleeding location within imaged region

applying a temporal filter that reduces the effect on the resistivity index of shape and conductivity changes resulting from the subject'"'"'s breathing cycle.

determining an alarm category depending on the rate of bleeding that has been calculated;

7. An EIT system as claimed in claim 1 wherein the data analysis system applies a digital filter to the data to provide temporal filtering of the data to thereby remove or at least minimise the effect of breathing on the EIT analysis.

8. An EIT system as claimed in claim 1 wherein the electrodes are provided in a belt adapted to be lain across an anterior surface of the body portion and having a length such that the ends to not extend fully around said body portion, the electrodes being spaced along the length of the belt.

9. An EIT system as claimed in claim 8 wherein the electrodes are substantially equally spaced from each adjacent electrode.

10. An EIT system as claimed in claim 1 wherein each electrode comprises a contact face adapted to contact the skin of the body portion wherein the contact face is of elongate form having an elongate axis oriented substantially transverse to the linear spacing of the electrodes.

11. An EIT system as claimed in claim 1 wherein the current source, voltage measuring means and data collection system are associated with an on-patient module adapted to be carried by the body having the body portion, wherein the data analysis system is provided by a remote processor and wherein data communication is provided between the on-patient module and the remote processor.

12. An EIT system as claimed in claim 11 wherein the data communication is by wireless communication.

13. An EIT system as claimed in claim 11 wherein the on-patient data module comprises processing circuitry and a telemetry transceiver that will allow data to be transferred to and from the processor.

14. An EIT system as claimed in claim 13 wherein the processing circuitry selects the pair of electrodes to which a current is applied and the pair of electrodes across which voltage is measured at any point in time.

15. A method for detecting changes in tissue volume using an EIT system, the method comprising the steps of:

applying a current between a pair of electrodes spaced at the surface of a body portion;

measuring, at predetermined intervals, and at a multiplicity of locations in a plane through the body portion, the voltage between pairs of electrodes at the surface of the body portion resulting from the applied current to provide a set of voltage measurements, wherein the electrodes extend in a substantially linear orientation across one side only of the body portion;

determining the changes of the voltage measurement between consecutive sets of voltage measurements;

generating a reconstructed image of the body portion;

determining a resistivity index of the tissue within the body portion from the reconstructed image;

deriving a volume of tissue from the determined resistivity index;

determining the rate of change of tissue volume between consecutive sets of voltage measurements.

16. A method for detecting changes in tissue volume as claimed in claim 15 wherein the method includes the further step of initiating an alarm where the rate of change of tissue volume is above a predetermined value.

17. A method for detecting changes in tissue volume as claimed in claim 15 wherein the resistivity index is calculated by generating a vector indicative of the changes in voltage measurements between consecutive sets of voltage measurements;

and multiplying the vector by a reconstruction matrix, the resultant matrix being the reconstructed image.

18. A method for detecting changes in tissue volume as claimed in claim 15 wherein the resistivity index is calculated by integrating pixel values from the reconstructed image.

19. An electrode belt adapted for use with an EIT system, the belt comprising a plurality of electrodes spaced along the elongate length of the belt and having contact faces adapted to make electrical connection with the skin of a body portion under examination wherein the belt is adapted to provide engagement of the electrodes on one side only of the body portion.

20. An electrode belt as claimed in claim 19 wherein the contact faces are of elongate form, the elongate length of the contact faces being oriented transversely to the elongate length of the belt.

21. An electrode belt as claimed in claim 20 wherein the contact faces are substantially rectangular with a length in the range of 75 mm to 100 mm and a width in the range of 5 to 25 mm.

22. An electrode belt as claimed in claim 19 wherein the belt is flexible to enable the belt to conform to the profile of the body portion upon which it is placed to facilitate contact of each electrode with the body portion.

23. An electrode belt as claimed in claim 19 wherein the body portion is the abdomen and the ends of belt are formed with a curvature to facilitate contact of electrode in the vicinity of the sides of the abdomen when in use.

24. An electrode belt as claimed in claim 19 wherein at least some of the electrodes are provided with an adhesive surround to facilitate secure engagement of the electrode with the skin.

25. An electrode belt adapted for use in bioelectrical measurements, wherein the belt is of elongate form having at least four electrodes spaced along the elongate length of the belt, the belt comprising a plurality of layers wherein the belt is constructed to provide active shielding.

26. An electrode belt as claimed at claim 25 wherein the belt comprises a core and shielding components, arranged in a multi-layer structure to provide the active shielding.

27. An electrode belt as claimed at claim 26 wherein one of the outer layers comprises a plurality of apertures spaced along the length of the layers to thereby expose an underlying conducting layer and thereby define a corresponding plurality of electrodes.

28. An electrode belt as claimed at claim 27 wherein each electrode has a conductive track connecting each electrode with a termination.

29. An electrode belt as claimed at claim 25 wherein the belt is manufactured by a process similar to that used for printed circuit board manufacture.

30. An electrode belt where as claimed at claim 25 wherein the apertures are elongate and the elongate axes of the apertures are oriented transverse to the elongate direction of the belt.

31. An electrode belt as claimed at claim 25 wherein the belt is adapted for use with EIT measurements.

32. An apparatus for detecting changes in tissue volume and its rate of change by EIT analysis comprising:

first processing means;

second processing means; and

electrode means adapted to apply a predetermined current between a pair of electrodes spaced at the surface of a body portion, under control of the first and second processing means and also adapted to measure in a plane through the body portion, the voltage between pairs of electrodes at the surface of the body portion resulting from the applied current to provide a set of voltage measurements, wherein the electrodes extend in a substantially linear orientation across one side only of the body portion;

the first processing means being operable to receive the set of measured voltages and to provide the set of voltage measurements to the second processing means, the first processing means being further operable to receive set of voltage measurements at predetermined intervals and to provide these sets to the second processing means, the second processing means being operable to determine the changes of the voltage measurement between consecutive sets of voltage measurements;

to provide a reconstructed image of the body portion;

to determine the resistivity index of the tissue from the reconstructed image;

to derive a volume of tissue from the determined resistivity index; and

to determine the rate of change of tissue volume between consecutive sets of voltage measurements.

33. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the first processing means is further operable to measure voltage noise levels.

34. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the second processing means is further operable to initiate an alarm where the rate of change of tissue volume is above a predetermined value.

35. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the second processing means is operable to determine the resistivity index by calculating a vector indicative of changes in voltage measurements between consecutive sets of voltage measurements;

multiplying the vector by a reconstruction matrix, the resultant matrix being the reconstructed image.

36. An apparatus for detecting changes in tissue volume as claimed in claim 35 wherein the resistivity index is generated by integrating the pixels or voxels in the reconstructed image.

37. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the electrode means comprises a belt including a multiplicity of substantially equidistantly spaced electrodes, whereby current can be applied to any pair of the multiplicity of electrodes, and the voltage measured from one or more pairs of the multiplicity of electrodes.

38. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the first processing means is operable to apply current to all pairs of electrodes on the belt, and to take voltage measurements from all possible pairs of electrodes, for each current electrode pair.

39. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the second processing means is provided remote from the first processing means.

40. An apparatus for detecting changes in tissue volume as claimed in claim 32 wherein the current is sequentially applied to all pairs of electrodes on the belt, and voltage measurements are measured from all possible pairs of electrodes, for each current electrode pair.