System and method for identifying fluid accumulation in a body part

Abstract

A method for identifying fluid accumulation in a body part, comprising obtaining an actual measurement of the body part by directly or indirectly measuring a first parameter related to the size of the body part of a patient, obtaining an estimated measurement of the first parameter by measuring an alternative predefined parameter of the patient, wherein the first parameter is related to the size of the body part of the patient, wherein the estimated measurement is calculated based on a mathematical relationship between the alternative parameter and the size of the body part; and correlating the actual measurement and the estimated measurement of the body part of the patient to assess any fluid accumulation in the body part.

Description

Technical Field

[0001] The present invention relates to a system and method for identifying fluid accumulation in a body part such as the foot. Background Art

[0002] Edema (or swelling) is an important symptom of many diseases, in which an area of ​​the body retains excess fluid. This is important in many diseases, such as heart failure (over half of hospitalized patients experience peripheral edema, or swelling of the feet) and cancer (lymphedema is often a complication of cancer treatment).

[0003] The most common method of measuring edema is by observing the "pit" where the thumb is pressed on the affected area for a few seconds and then removed, and if edema is present, the pit or "pit" is slowly filled up due to the internal tissue fluid slowly filling up the "pit". The difficulty with this method is that it does not allow for quantitative measurement due to the local nature of the test and the difficulty in grading the pit depth and refilling speed.

[0004] Other commonly used methods are to measure the circumference or volume of the affected area and track this over time. Although these methods provide a quantitative approach, quantifying the effect of edema on a single measurement is challenging unless a baseline is known for that specific patient, especially in the case of obese patients. If the edema is unilateral (common in lymphedema), the measurements of the affected limb can be compared to the contralateral limb (e.g., left foot to right foot), in which case the difference in volume (or circumference) is both quantitative and specific to the edema itself.

[0005] It is an object of the present invention to provide an improved system and method for identifying fluid accumulation in a body part such as the foot, which may be indicative of edema associated with a variety of diseases. Summary of the invention

[0006] To this end, a first aspect of the present invention provides a method of identifying fluid accumulation in a body part of a patient, the method comprising: directly or indirectly measuring a first parameter related to the size of the body part of the patient to obtain an actual measurement value of the body part;

[0007] obtaining an estimated measurement of the first parameter related to the size of the patient's body part by measuring an alternative predefined parameter of the patient, wherein the estimated measurement is calculated based on a mathematical relationship between the alternative parameter and the size of the body part; and

[0008] The actual and estimated measurements of the patient's body part are correlated to assess any fluid accumulation in the body part.

[0009] Preferably, the step of measuring the first parameter comprises directly or indirectly measuring the volume, thickness or circumference of the body part, and more preferably comprises imaging the body part to obtain the volume, thickness or circumference of the body part.

[0010] In a preferred embodiment of the invention, said imaging of the body part comprises: imaging said body part in three dimensions to generate a measurement of said first parameter, preferably associating said three-dimensional data with a three-dimensional model of said body part.

[0011] The method may also include using a mathematical modeling system to extract two sets of measurements substantially simultaneously to provide an actual model based on crowd-derived model parameters and an estimated model, and comparing the models to determine whether the actual model identifies fluid accumulation in the body part. A first deformable model with multiple deformation parameters based on the actual body part may be provided, and compared with a second model (e.g., a second model with multiple deformation parameters) based on predefined parameters and fluid accumulation to obtain a first volume, the second model being based on predefined parameters and representing crowd-derived values ​​without any fluid accumulation or with a known amount of fluid accumulation, thereby being able to well simulate the overall structure of the patient, while estimating the shape of the body part without fluid accumulation, and optionally calculating the difference between the first volume and the estimated volume to assess any fluid accumulation in the patient.

[0012] According to the invention, the step of measuring the first parameter may comprise directly or indirectly measuring the volume of the body part.

[0013] The step of estimating the first parameter may comprise measuring the volume of the body part directly or indirectly by measuring a plurality of other parameters of the body part to calculate the volume of the body part based on these measurements. Preferably, the estimated measurements comprise an estimated volume of the body part based on measuring an alternative predefined parameter related to the volume of the body part, the estimated volume being calculated based on a mathematical relationship between the alternative parameter and the body part. Preferably, the estimated volume is calculated based on one or more measurements selected from the group consisting of the length of the body part, the width of the body part, the weight of the body part, the height of the body part, the density of the body part and the circumference of the body part. The estimated volume may be adjusted based on the patient's overall height, weight and / or bioimpedance.

[0014] The method according to the present invention may include obtaining and processing measurements at intervals over a period of time to track changes in fluid accumulation in the patient. The method may be computer-implemented and may also include assessing and / or communicating the patient's health status and risk based on identifying differences between actual measurements and estimates of body parts.

[0015] Preferably, the body part is a foot.

[0016] According to a second aspect of the present invention, there is provided a system for identifying fluid accumulation in a body part of a patient, the system comprising:

[0017] a measuring instrument for directly or indirectly measuring a first parameter related to the size of a body part of a patient, the measuring instrument providing an actual measurement of the body part;

[0018] a measurement data comparison unit configured to compare an actual measurement value of a body part with an estimated measurement value for a parameter of the body part, wherein the estimated measurement value is based on measuring alternative parameters of a patient and is calculated based on a mathematical relationship between the alternative parameters; and

[0019] The diagnosis unit is configured to determine fluid accumulation in the patient based on the comparison result of the comparison unit.

[0020] Preferably, the surveying instrument comprises a depth sensing camera device.The depth sensing camera device may comprise at least one emitter and one detector array, or at least two detector arrays. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a graph showing the volume of the foot relative to the length of the foot for patients with edema and patients without edema.

[0022] Figure 2 A foot model created from 3D imaging of the foot without edema-specific morphology (left side of the image) and with edema-specific morphology for the patient (right side of the image). DETAILED DESCRIPTION

[0023] In the course of evaluating the clinical validity of a 3D limb volume measurement system described in the inventors' co-pending application (GB2542114B), the inventors surprisingly discovered that a single measurement of fluid accumulation indicative of limb oedema could be significantly quantitatively obtained by the difference between two volumes.

[0024] The first volume is the volume most directly observed from the target patient body part (e.g., by 3D imaging or water displacement, or the volume of a cylinder estimated from multiple circumference measurements, or any other method known in the art). The second volume is calculated based on a mathematical relationship between certain measured parameters of the patient (e.g., patient height, weight, and bone length) and produces an estimate of the volume of the target body part, wherein the mathematical relationship provides an estimate that is relevant to a more general patient population, ideally without edema but with sufficient variation in confounding factors, such as changes in body fat.

[0025] A simple example of a first volume measurement is to measure the volume (in milliliters) of the patient's foot up to a height of 20 cm from the ground by the displacement of water when the patient stands in a bucket filled with water. This provides an accurate (although unmanageable) measurement of the total volume of the foot.

[0026] A simple example of a secondary volume measurement is to relate the volume of the foot (up to a height of 20 cm) to the length of the foot (measured from the tip of the big toe to the heel), where the volume estimate (in milliliters) is 60 times the foot length (in centimeters).

[0027] The difference between these two measurements (i.e., the first volume minus the second) yields a number that effectively categorizes patients in the heart failure population into those who are found by clinicians to have pitting edema during an outpatient visit and those who do not. By this measure, more than 80% of patients who were clinically assessed as having pitting edema had a positive volume difference, whereas more than 80% of patients who were clinically assessed as not having pitting edema or who were healthy volunteers had a negative volume difference by this measure. Moreover, the size of this difference correlates well with the patient's subjective clinical grading of the degree of edema.

[0028] Figure 1 A graph separating foot length and foot volume according to clinician-assessed edema status is shown.

[0029] Naturally, a relationship based solely on foot length will be subject to error due to body fat percentage. More complex models, including for example patient height, weight or bioimpedance such as body fat as a confounder, will naturally correlate better with the presence of edema.

[0030] An alternative, preferred approach is to extract both sets of volumes at once using a single mathematical modeling system. For example, when using a 3D camera system, it is often possible to fit a deformable model to the observed 3D points collected from the camera. The purpose is often to allow certain model parameters (e.g., bone joint angles and lengths) to be adjusted to minimize the difference between points on the surface of the virtual model and the observed 3D points. Such models often also contain parameters that adjust the shape of the model, often referred to as "morphs" in the 3D rendering community, for example, these parameters might change the volume of flesh around a virtual skeleton and allow the flesh volume to be scaled to a range of values.

[0031] When such a model was built and tested on the same group of heart failure patients, some of these "deformations" were found to correlate much more strongly with subjective clinical grading of edema than others. For example, the study found that volume changes around the ankle, which essentially flattens the ankle, correlated more strongly with clinical grading of edema than did the patient's BMI.

[0032] For certain patients, Figure 2 Such a 3D foot model is shown, on the left, without certain "deformations" of edema applied, and on the right, with these deformations applied.

[0033] In the right model, the extra mass around the ankle bone is particularly evident. In addition, many patients in the heart failure trial were also monitored while receiving diuretics, which are intended to reduce fluid accumulation and thus edema. Therefore, it is possible to observe which "deformities" in a particular patient are associated with changes in foot volume over time, suggesting a direct relationship to fluid accumulation indicative of edema.

[0034] Thus, a method for edema estimation is made possible whereby the observed 3D foot data is modelled using a deformable model and all deformation parameters are allowed to vary freely to provide a first volume. A second volume is then calculated by resetting the values ​​of those morphologies found to be associated with edema to population averages. This enables the overall structure of the foot of that particular patient to be well modelled while estimating the edema-free shape of the foot. It was found that in patients treated with diuretics, the difference between the two volumes calculated by this technique was particularly sensitive to changes in edema over time and also correlated well with subjective clinical assessments of edema.

[0035] Obviously, the difference between the two volumes can be further processed to provide a variety of useful metrics. For example, by expressing the difference in the percentage of patients who do or do not have edema as determined by the clinician, which percentage shows greater than or less than various threshold volume differences, the probability that a patient with a specific volume difference would be assessed by the clinician as having edema can be estimated. This is useful for risk scoring and risk stratification of patients, especially when combined with other clinical metrics that are also probabilistic in nature.

[0036] The present invention is not only clinically useful, providing a numerical measurement of fluid accumulation indicative of edema, but if implemented using appropriate methods (e.g., a 3D camera), it can measure changes in fluid accumulation in patients at home. This can not only save the patient's time to go to the hospital for an appointment or the time for the clinical team to reach the patient, but if implemented as part of a telemedicine system, it can provide alerts about the patient's deteriorating health status. Such a system may reasonably reduce the current extremely high rate of repeat hospitalizations for chronic diseases (e.g., heart failure), not only saving a lot of medical resources, but also providing patients with a better quality of life.

[0037] Obviously, the "difference" between volumes need not be a simple subtraction difference, but can be a proportional relationship, or any number of statistical results tests or other numerical comparisons. It is also obvious that, as opposed to strictly using volumes, a large number of volume-related model outputs can be used in embodiments of the present invention. For example, the aforementioned virtual 3D model can virtually measure the thickness or circumference at various locations and compare these virtual circumference measurements, or the surface area of ​​the 3D model can be compared. For the purposes of the present invention, all of these types of comparisons are considered to be a non-limiting list of possible size comparisons in the claims.

Claims

1. A method for identifying fluid accumulation in a body part of a patient, the method comprising: Measuring a first parameter related to the size of a body part of the patient to obtain an actual measurement value of the body part, wherein the measurement includes three-dimensional imaging of the body part to obtain the measurement value of the first parameter; obtaining an estimated measurement of the first parameter related to the size of the body part of the patient by measuring at least one alternative predefined parameter of the body part of the patient; the alternative predefined parameter being based on a relationship of an alternative parameter to the size of the body part, the body part size being based on at least one population-derived value of the at least one alternative predefined parameter; and correlating the actual measurements and the estimated measurements of the body part of the patient to assess any fluid accumulation in the body part; characterized in that: The three-dimensional imaging of the first parameters provides a first deformable model based on the actual body part with a plurality of deformation parameters, which is compared with the estimated measurements comprising a second model based on predefined parameters and the effusion.

2. The method according to claim 1, wherein: After three-dimensional imaging of the body part, the three-dimensional data is associated with a three-dimensional model of the body part to obtain a measurement value of the first parameter.

3. The method according to claim 1 or 2, wherein: The second model is based on population-derived parameters.

4. The method according to claim 1, 2 or 3, wherein: The second model did not include effusion.

5. The method according to any one of claims 1 to 4, wherein: The second model has a plurality of deformation parameters.

6. The method according to claim 1, wherein: The estimated measurements are adjusted based on the patient's overall height, weight, and / or bioimpedance.

7. The method of claim 1 further comprising obtaining and processing the measurements over time to track changes in fluid accumulation in the patient.

8. The method according to claim 1, wherein: The first parameter is the volume, thickness or circumference of the body part; the alternative predefined parameters are the length of the body part, the width of the body part, the weight of the body part, the height of the body part, the density of the body part and the circumference of the body part.

9. The method according to claim 1, wherein: The body part is a foot.

10. The method according to claim 8, wherein: The first parameter is the volume of a predefined area of ​​the foot and the alternative parameter is the length of the foot.

11. The method according to claim 1, wherein: The method is computer-implemented and further includes assessing and / or communicating a patient's health status and risk based on the identified difference between the actual measurement and the estimated measurement of the body part.

12. A system for identifying fluid accumulation in a body part of a patient, the system comprising: a measurement instrument including a depth sensing camera device to provide three-dimensional imaging of a body part and to correlate the three-dimensional data of the body part with the three-dimensional image to produce a measurement of a first parameter based on the actual body part; a measurement data comparison unit configured to compare the measured value of the first parameter of the body part with an estimated measured value of the parameter for the body part, wherein the estimated measured value comprises a second model based on at least one alternative predefined parameter of the body part, the alternative predefined parameter being based on a relationship of an alternative parameter to a size of the body part, the body part size being based on at least one population-derived value of the at least one alternative predefined parameter for having or not having effusion; and The diagnosis unit is configured to determine the fluid accumulation in the patient based on the result of the comparison of the actual measurement value and the estimated measurement value by the comparison unit.

13. The system according to claim 12, wherein: The depth sensing camera device includes at least one emitter and one detector array, or at least two detector arrays.

14. The system according to claim 12 or 13, wherein: The measuring instrument is configured to provide a first deformable model with a plurality of deformation parameters based on the actual body part from three-dimensional imaging for the first parameters.

15. A system according to any one of claims 12 to 14, wherein: The measurement data comparison unit is configured to provide estimated measurement values ​​including a second model having a plurality of deformation parameters.

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