Monitoring urine flow of a subject

Abstract

There is provided a system for monitoring urine flow of a subject. The system comprises: one or more sensors comprising an ultrasound transducer configured to be inserted in the subject and to detect a dimension of a urinary bladder of the subject; and one or more data modules that are in communication with the one or more sensors, wherein the one or more data modules are configured to: receive bladder data from the one or more sensors, the bladder data comprising measurements of the dimension over a time period; determine a volume and / or a change in volume of the urinary bladder over the time period based on the bladder data; determine one or more values for a parameter indicating urine flow based on the volume and / or change in volume of the urinary bladder over the time period. There is also provided a computer-implemented method for monitoring urine flow of a subject and a computer program product.

Description

[0001] MONITORING URINE FLOW OF A SUBJECT

[0002] TECHNICAL FIELD

[0003] The present disclosure relates to a systems, methods, and computer program products for monitoring bladder volume and / or urine flow of a subject.

[0004] BACKGROUND

[0005] The urinary bladder is part of the urinary system and performs a critical clinical function in humans and other mammals. It collects and stores urine, a waste product of the human or animal body, before that urine is expelled by urination.

[0006] Urination may change, and such changes may be a sign of a urinary condition or a wider urological condition. Changes in urination may include increases or decreases in frequency of urination, increases or decreases in volume expelled during urination, uncontrolled or involuntary urination, referred to as urinary incontinence, or by changes in how the urge to urinate is felt. These changes may be clinically significant, indicating, for example, a voiding dysfunction, infection and other complications, or, in males, an enlarged prostate. In humans, at least, such changes can be a source of embarrassment and discomfort.

[0007] Conventional ways of investigating urinary bladder function and urination are unsuitable for long-term monitoring and are either uncomfortable and highly invasive or require careful management. For example, in urodynamic testing, a patient may be required to keep a constant diary of urinary events and may be required to use an in-toilet device for measuring expelled volumes of urine. Such solutions are cumbersome, difficult to manage, and subject to error in how the diary is kept or how the device is used.

[0008] For voiding dysfunction, some specific solutions exist for children. These solutions use external ultrasound sensors fixed to the subject’s skin to determine when a volume of urine in the bladder exceeds a particular threshold and to alert the subject that it is time to urinate. Such solutions cannot be used in adults, due to significant differences in body and bladder shape. Such solutions are also highly dependent on posture of the subject. SUMMARY

[0009] The aspects described herein address at least some of the above issues. Briefly, it is described below how at least one ultrasound transducer can be configured to be implanted into a subject to monitor a urinary bladder of the subject. The ultrasound transducer provides measurements to modules that perform analysis to determine the bladder volume and / or characteristics of the flow of urine into or out of the urinary bladder.

[0010] According to a first aspect, there is provided a system for monitoring urine flow of a subject. The system comprises: one or more sensors comprising an ultrasound transducer configured to be inserted in the subject and to detect a first dimension of a urinary bladder of the subject; and one or more data modules that are in communication with the one or more sensors, wherein the one or more data modules are configured to: receive bladder data from the one or more sensors, the bladder data comprising measurements of the first dimension of the urinary bladder over a first time period; determine a volume and / or a change in volume of the urinary bladder over the first time period based on the bladder data; and determine one or more values for a parameter indicating urine flow into or out of the urinary bladder based on the volume and / or change in volume of the urinary bladder over the first time period.

[0011] The system described provides a different way for monitoring urine flow than other techniques. Some other techniques monitor urine flow using urine as it is expelled from the body, for example by utilizing cumbersome in-toilet devices that collect and weigh the amount of urine expelled. While the amount of urine collected can be used to determine flow, such techniques may not enable any further analysis. In contrast, the present system utilizes a determination of bladder volume and / or changes in volume, which enables a more direct measure of urine flow because the bladder’s volume is generally proportional to the amount of urine in it. Using a more direct measure of urine flow, by monitoring the bladder directly, can enable greater insight into the workings of the bladder. The determination of the volume and / or change in volume can be an estimation of the volume / volume changes as discussed further below, with enhanced accuracy in this estimation due to the use of data from an implanted sensor that can more directly measure at least the first dimension of the bladder during the first time period. Optionally the bladder data can be measured at different time periods as well, e.g. over a longer continuous time split into several time periods, or over several separated time periods such as time periods spaced out at a desired frequency of measurement. The sensors may be configured to detect additional dimensions, e.g. orthogonal dimensions, such as by means of additional ultrasound transducers as discussed below. In one example the sensors are configured to detect each of three dimensions, e.g. width, depth and height. Bladder volume can also be used in other ways, such as to determine the maximum storage capacity and to determine postvoid residual volume, and so is useful to monitor for those reasons as well as for assessing urine flow.

[0012] Alternative existing techniques may artificially fill the bladder and may use intrusive and uncomfortable probes inserted into the rectum and urethra to monitor how the bladder reacts. In contrast, the present system utilizes implantable / insertable sensors or sensor assemblies, which may be referred to as body sensors. These are much less intrusive and uncomfortable than making use of inserted probes. Advantageously, this system allows for ambulatory monitoring, as well as monitoring when the patient is at rest. These sensors can also enable more detailed monitoring of events, both in relation to urination and otherwise, because they can monitor the normal functioning of the bladder without artificial filling.

[0013] Moreover, existing techniques may only be able to determine urine flow out of the bladder when the subject is expecting to expel urine, such as during urination. Urination may be referred to as a urination event, voiding, or a voiding event. The use of bladder volume to measure parameters relating to urine flow enables monitoring of urine flow at other times, enabling leakage to be identified and quantified, the filling of the bladder to be quantified, and for the relationship between urine flow and pre- and post-urination volumes to be better understood.

[0014] Overall, such a system can provide greater insight into a subject’s bladder, aiding faster diagnosis by a physician.

[0015] While some of the above advantages are described for circumstances where the subject is human, the subject may alternatively be an animal having a urinary bladder. Specifically, the subject may be a mammal having a urinary bladder, such as a dog or a horse.

[0016] The system may be provided in a single device or may be a distributed system. As a single device, the system may be configured to be wholly attached to the subject, enabling ambulation. For example, the one or more sensors may be configured to be inserted within the subject and may connect to the one or more data modules which may be positioned outside of the subject and worn by the subject, by being attached to the skin of the subject or by being incorporated into a garment worn by the subject.

[0017] As a distributed system, the one or more sensors may be inserted in the subject and the one or more data modules may be configured to be at a separate location, such as a remote computing device or at multiple remote computing devices. In other embodiments, the one or more data modules may be split so that some of the one or more data modules are configured for direct connection to the one or more sensors, in the form of a wearable module, and some of the one or more data modules may be at the remote computing device or devices. For example, the one or more data modules may comprise a data collection module and a data analysis module. In some embodiments, these modules may be split so that the data collection module is configured to collect data directly from the one or more sensors and the data analysis module may be remote and separate from the data collection module. The data analysis module may be configured to obtain the data from the data collection module, either by receiving it in a transmission or by reading it from the data collection module. The data analysis module may be provided in a mobile device, such as a mobile telephone, and may receive data from the data collection module via a wired or wireless communication means.

[0018] The ultrasound transducer, which may be referred to as an ultrasonic transducer, may transmit and receive ultrasonic signals. The ultrasound transducer may comprise an ultrasonic transmitter and an ultrasonic receiver. The ultrasound transducer may comprise a plurality of ultrasonic transmitters and / or a plurality of ultrasonic receivers. The ultrasonic transmitter may emit an ultrasonic signal. The signal may reflect off a wall of the urinary bladder. The ultrasonic receiver may receive one or more reflections of the signal. Electronics of the ultrasonic receiver may be configured to determine a direct reflection of the one or more reflections. Said electronics may be configured to determine a time of flight of the ultrasonic signal from the ultrasonic transmitter to the ultrasonic transceiver for the direct reflection. The electronics may be configured to determine the dimension of the urinary bladder based on the time of flight of the signal. The ultrasonic transmitter may be separate to the ultrasonic receiver or the transducer may comprise a combined transmitter and receiver. Where the transducer comprises a combined transmitter and receiver then this may be referred to as a transceiver, which may include any of the transmitter or receiver features discussed herein. The ultrasound transducer may comprise a transmitter circuit for driving the ultrasonic transmitter. The ultrasound transducer may comprise a receiver circuit for detecting signals from the ultrasound receiver. The ultrasound transducer may comprise a combined transmitter-receiver circuit for operating a combined ultrasonic transmitter and receiver. The combined transmitter-receiver circuit may include switching electronics to enable switching between transmitting and receiving the ultrasonic signal.

[0019] The ultrasound transducer may be a piezoelectric ultrasound transducer or a capacitive transducer. The ultrasound transducer may be a microscale ultrasound transducer or a nanoscale ultrasound transducer. The ultrasound transducer may be manufactured using micro-machining. The ultrasound transducer may be a micro-electromechanical system (MEMS) ultrasound transducer. MEMs transducers may be referred to as micromachined ultrasonic transducers, and may be piezoelectric micromachined ultrasonic transducers (PMUTs) or capacitive micromachined ultrasonic transducers (CMUTs).

[0020] The ultrasonic transmitter and ultrasonic receiver may be on a single die, e.g. a MEMS die or microsystems die. The transducer may be arranged to transmit and receive signals without switching electronics.

[0021] The ultrasound transducer may be referred to as an in-vivo ultrasound transducer, because it is configured to be inserted within the subject. The ultrasound transducer may be configured to be inserted through the subject’s skin to access the bladder. For example, the ultrasound transducer may be configured to be inserted into the subject’s abdomen, such as through the abdominal wall. The ultrasound transducer may therefore be referred to as a percutaneous ultrasound transducer, a transcutaneous ultrasound transducer, or a transabdominal ultrasound transducer. The ultrasound transducer, at least, may be configured to be inserted through a bladder wall of the subject. As the ultrasound transducer is configured to be inserted through tissue of the subject, it may be referred to as an implantable ultrasound transducer or an ultrasound transducer that is configured to be implanted. Such insertion may be referred to as implantation. In this sense, the ultrasound transducer is implantable or an implantable sensor rather than an insertable probe that passes into the urethra. The ultrasound transducer may be configured to be inserted via an introducing device such as a transcutaneous catheter or suprapubic catheter. The system may comprise such an introducing device, such as a transcutaneous introducing device or catheter for inserting the ultrasound transducer in the subject, and specifically through the skin of the subject. This is in contrast to transducers forming part of a probe that are passed through the urethra only, which may pass through the urethra using a urethral catheter.

[0022] The ultrasound transducer may be configured as an implantable device, i.e. one which is inserted into the patient and kept in place for prolonged time periods, such as over 30 days. The ultrasound transducer may be configured to be inserted at the bladder, e.g. in, on or adjacent to the bladder. The ultrasound transducer may be configured to be inserted to a location within the subject that is outside the urinary bladder of the subject, to a location that is within a wall of the urinary bladder, or to a location within the urinary bladder. When the ultrasound transducer is configured to be inserted outside the urinary bladder, it may also be configured to be adhered or otherwise attached, such as by using a suture, to the urinary bladder wall. Insertion within a wall of the bladder may be done via submucosal implantation / insertion. When the ultrasound transducer is configured to be inserted inside the urinary bladder, it may also be configured to be attached to the urinary bladder, such as by suturing the transducer to a wall of the bladder. Wired attachments or anchors may also be used to provide attachment to the tissues of the bladder wall. The transducer may be firmly attached to a specific point on the wall, or it tethered to allow for some movement, e.g. to avoid adverse effects on the sensor measurements from the expansion and contraction of the bladder walls / rugae. Alternatively, the ultrasound transducer may be configured to be left unattached within the internal volume of the bladder.

[0023] The ultrasound transducer may have one or more modifications that make it suitable for use within the body of the subject, and particularly for use close to or within the bladder. For example, as is discussed below in more detail, the ultrasound transducer may include a biocompatible material.

[0024] The one or more sensors may include additional transducers or sensors other than the ultrasound transducer. The one or more sensors may include further ultrasound transducers and / or pressure sensors, for example. The sensors may be arranged as a sensor assembly. The sensor assembly may be small compared to the volume of the bladder, to provide as little interference with the operation of the bladder as possible. Specifically, the use of microscale sensors within the sensor assembly may allow for such a small size. The sensor assembly may be provided on or within a flexible or rigid housing, and the housing may be non-inflatable.

[0025] The measurements of the first dimension of the urinary bladder are obtained by the ultrasound transducer over the first time period. Multiple measurements are taken, e.g. at least two, in order to allow for urine flow to be assessed by reference to the change in the measured dimension(s) of the bladder. As noted below there may be measurements of multiple dimensions, e.g. by additional ultrasound transducers, so that the first dimension is one of a set of dimensions that may be used to determine the bladder volume or the changes in volume. The ultrasound transducer may obtain the measurements at a sampling rate. The bladder data may hence comprise multiple sets of measurements of the dimension(s) for the first time period and for further time periods.

[0026] The one or more data modules may be in wired communication with the one or more sensors or in wireless communication with the one or more sensors. The one or more data modules may receive the bladder data using said wired or wireless communication. The bladder data may be received as a packet of data for a time period. The bladder data may be received as a packet of data for each sensor of the one or more sensors or as a packet of data for all the sensors of the one or more sensors. The bladder data may be received at the end of the first time period. Alternatively, the bladder data may be received as it is measured, i.e. at one or more points before the end of the first time period. In other words, the bladder data may be streamed from the sensors to the one or more data modules. When the bladder data is received in this way, it may be received over the first time period. The one or more data modules may include a cache or other data storage in which the data is stored as it is received, so that it can be subsequently analysed.

[0027] The measurements of the first dimension may be in the form of voltage measurements at the ultrasound transducer. The one or more data modules may be configured to interpret such measurements to determine measurements in an appropriate form, i.e. using the correct units.

[0028] The first time period may be part of a wider time period. For example, bladder data may be received over an hour, several hours, a day, a week, or more. The first time period may be a portion of that period, such as a few seconds or minutes out of the hour, hours, day, or week. Bladder data may also be obtained for a second time period, e.g. a new time period separated from the first time period. This can allow data for the same patient to be compared for different phases of a monitoring / treatment programme.

[0029] The data modules receive the bladder data and determine the volume of the bladder and / or changes in the volume of the bladder. Thus, the data modules may carry out an assessment of volume parameters based on the bladder data. This may involve an estimation of volume according to assumptions about bladder shape and / or prior knowledge of the patient’s bladder shape. The bladder volume, or change in volume, may be determined using one or more predetermined formulas or by correlating the first dimension. The system may use techniques known in the art for obtaining a measure of volume based on dimensions of the bladder, i.e. to establish an estimate of absolute volume. The system may alternatively use the change in the dimension(s) of the bladder to estimate a change in volume without determining the overall volume of the bladder.

[0030] The system is configured to detect the first dimension over the first time period in order to obtain multiple measurements (i.e. at least two) of the first dimension. Optionally further dimensions are also measured, e.g. orthogonal dimensions or some other set of non-parallel dimensions. Determining the volume of the urinary bladder over the first time period may include determining the volume for each measurement of the first dimension, determining the volume for a subset of the measurements of the first dimension (e.g. taking an average or peak value of the dimension), or determining the volume for a subset of times within the first time period. The subset of measurements or times may correspond to at least two measurements or to two times within the first time period. Determining the change in volume of the urinary bladder over the first time period may include comparison of two volumes determined as above, or it may include determining a change in the first dimension (and optionally multiple dimensions) and using that change to make an assessment of a change in volume.

[0031] Information about the bladder volume is determined directly from the bladder data, which include at least the first dimension, and the parameter indicating urine flow is determined from the changes in volume. Accordingly, the parameter is based on direct measurements, rather than performing any sort of imaging and inferring the parameter from said imaging. Directly determining the change in volume and subsequently the urine flow parameter requires less computation and less data than imaging, which is useful where storage capacity and computational resources are limited, such as in an ambulatory device. Other measurements in addition to the volume may be used to determine the parameter. Other parameters or measurements may be determined based on the volume, and these other parameters or measurements may be used to determine the values for the parameter indicating urine flow. An example of this is that the one or more data modules may be configured to determine a rate of change of the volume of the urinary bladder over at least a portion of the first time period. The one or more values for the parameter indicating urine flow may be based on the rate of change of the volume of the urinary bladder. The rate of change of volume may be the parameter indicating urine flow.

[0032] The bladder data may comprise timestamps corresponding to each measurement of the first dimension. The rate of change of volume may be determined between two timestamps at the beginning and the end of the first time period. The rate of change of volume may be determined as the difference in volume divided by the amount of time between the two timestamps. The rate of change of volume may be expressed as a flow rate.

[0033] The first time period may correspond to an event. The event may be urination, which may be referred to as a voiding event or voiding phase. The event may be a filling event or filling phase. The one or more data modules may be configured to determine the portion of the first time period. The first time period may be determined from a wider time period by determining the event or by determining timestamps corresponding to the event. A trigger for the event may be identified. For example, a trigger may be a rate of change of volume exceeding a threshold amount over a short time period.

[0034] The rate of change of volume may be directly correlated to an amount of urine flow from the urinary bladder, due to the way in which the bladder expands as it fills with urine. It is therefore useful to determine the value or values for the parameter indicating urine flow based on the rate of change of volume.

[0035] Alternatively, the one or more values for the parameter indicating urine flow may be determined directly from the volume / change in volume of the urinary bladder. Statistical analysis may be used to determine the value or values for the parameter based on a time series indicating volume over the first time period.

[0036] The rate of change of volume may be an average rate of change of volume, a maximum rate of change of volume, or a minimum rate of change of volume. Alternatively, the parameter indicating urine flow may be a urine flow rate. The urine flow rate may be an average urine flow rate, a maximum urine flow rate, or a minimum urine flow rate.

[0037] The urine flow rate may be determined based on a rate of change of volume. The volume may be determined as or converted to a liquid volume, to allow the urine flow rate to be determined. The rate of change of volume may be converted to or determined as a liquid volume, thereby allowing the urine flow rate to be determined.

[0038] The one or more data modules may be configured to monitor the parameter indicating urine flow over a plurality of time periods that includes the first time period. The one or more data modules may be configured to determine a rate of change of the parameter indicating urine flow over the plurality of time periods. Where the parameter is a urine flow rate, the one or more data modules may be configured to determine a rate of change of urine flow rate over the plurality of time periods. This may allow changes to the bladder or urinary system to be identified, for example in response to treatment.

[0039] The ultrasound transducer may be a first ultrasound transducer and the one or more sensors may comprise a second ultrasound transducer configured to be inserted in the subject and to detect a second dimension of the urinary bladder, the second dimension being different to the first dimension. The second dimension is different to the first dimension and may be not parallel to the first dimension. The second dimension may be perpendicular to the first dimension. The bladder data may comprise a plurality of measurements of the second dimension of the urinary bladder over the first time period.

[0040] Utilizing multiple ultrasound transducers allows different dimensions to be determined and a better determination of the volume to be made. The volume may be determined based on one dimension (i.e. the first dimension), based on two dimensions, based on three dimensions, based on four dimensions, based on five dimensions, or based on more than five dimensions. A single dimension may be sufficient to assess volume or changes in volume in some situations, e.g. when information about shape is known, but using multiple dimensions can enhance the accuracy of the determination of volume or change in volume, e.g. when there is also a change in bladder shape or a change in orientation of the sensor. The different dimensions may be non-parallel. A typical configuration may be arranged to obtain measurements in each of three orthogonal dimensions. Each dimension may be determined using a different ultrasound transducer. In some examples, more than one dimension can be determined using a single ultrasound transducer.

[0041] The one or more sensors may comprise a third ultrasound transducer configured to be inserted in the subject and to detect a third dimension of the urinary bladder, the third dimension being different to the first dimension and the second dimension. The bladder data may comprise a plurality of measurements of the third dimension of the urinary bladder over the first time period.

[0042] The first, second, and third dimensions may be an orthogonal set of dimensions, and may for example be a width, a height, and a depth of the urinary bladder.

[0043] More than one ultrasound transducer may be provided configured to determine a dimension. Two first ultrasound transducers may be provided that are configured to determine the first dimension. The two first ultrasound transducers may be provided on either side of a probe or sensor assembly, and may be configured to each measure a different part of the first dimension. In some examples, two first ultrasound transducers, each configured to determine separate parts of the first dimension, and two second ultrasound transducers, each configured to determine separate parts of the second dimension, may be provided. A single third ultrasound transducer may be provided, or two third ultrasound transducers may be provided to determine the third dimension.

[0044] Where more than one dimension is measured by a plurality of sensors, such as a least a first ultrasound transducer and a second ultrasound transducer, a relationship between at least some of the sensors may be known. By a known relationship, it is meant that relative locations and / or orientations of the sensors are predefined or determinable in order that the relationship between the corresponding dimensions is known (e.g. as a set of orthogonal dimensions). The sensors may have fixed locations and / or orientations relative to one another, and these fixed relative locations and / or orientations may also fixed within or relative to the bladder, or may be arranged such that the relative locations and / or orientations can be determined. These fixed relative locations and / or orientations between the sensors may be the same at all times, i.e. the sensors may be fixed relative to one another prior to insertion and after insertion, and this fixing may not vary during the insertion or measurement process. Thus, the measurements of the dimensions may be linked together to enable precision in the determination of the volume. The first ultrasound transducer and the second ultrasound transducer, at least, may be arranged as an ultrasound array. This array may optionally include further sensors, e.g. a third ultrasound transducer. The known relationship between the sensors / dimensions may be achieved by such an ultrasound array. In an array, the ultrasound transducers are arranged in a predefined way, meaning at least one of a relative location or a relative orientation of the transducers is fixed. The ultrasound array may be a tessellated array. The ultrasound array may be a rectangular array. The ultrasound array may have a depth of one transducer and a length equal to the number of transducers in the array.

[0045] An ultrasound transducer may comprise an array of transmitters and / or an array of receivers.

[0046] An ultrasonic signal may be directed using beamsteering using the ultrasound array or an array of ultrasound transmitters. A direction of a received signal may be determined using beamsteering using the ultrasound array or an array of ultrasound receivers.

[0047] The one or more data modules may be configured to determine the volume of the urinary bladder over the first time period based on a predetermined volume formula that includes the at least the first dimension and the second dimension, and optionally the third dimension and any other dimensions for which there are ultrasound transducers to determine them or that are known.

[0048] The predetermined volume formula may be width x height x length x A, where A represents a constant that corresponds to an approximate bladder shape. The constant A may be 0.7, in the case of a typical bladder shape. The constant A may be determined based on preliminary bladder data, as will be described below. Alternatively, the urinary bladder may be modelled as a sphere, a triangular prism, a cylinder, a cuboid, or another three- dimensional shape, and the predetermined volume formula may be the corresponding formula for determining volume of the shape on which the bladder is modelled. The system may comprise one or more modules configured to determine a volume formula for the urinary bladder of the subject.

[0049] The one or more data modules may be configured to receive preliminary bladder data from the one or more sensors, the bladder data comprising measurements of the first dimension of the urinary bladder over a preliminary time period that is before the first time period, and determine a relationship between at least the first dimension and a volume of the bladder based on the preliminary bladder data, wherein the volume of the urinary bladder over the first time period is based on the relationship.

[0050] The relationship may be between a plurality of dimensions and the volume, e.g. a relationship using an orthogonal set of dimensions. The relationship may indicate a predetermined volume formula to be used for the bladder. A new volume formula may be determined based on the relationship.

[0051] The relationship may be determined based on relative changes in a plurality of dimensions. The relationship may be determined by correlating at least the first dimension with a volume of urine expelled from the bladder or a volume of liquid ingested by the subject. Thus, earlier volume data for urination can be used to determine a relationship between the measured dimension(s) and the bladder volume / change in volume, such as by fitting a formula to the earlier volume data and / or by creating a look-up table.

[0052] The preliminary bladder data may be received by the one or more data modules as part of an initialization phase on the system performed before the first time period. The one or more data modules may receive a signal that causes it to begin the initialization phase. The initialization phase may be performed automatically and a signal may be output by the one or more data modules once it has been finished. The initialization phase may be referred to or may include calibration of the one or more sensors.

[0053] The one or more data modules may be configured to receive further preliminary bladder data, the relationship being determined based on the further preliminary bladder data. The further preliminary bladder data may include indications of urination, measurements relating to urination such as a volume of urine expelled, or other data that may allow correlation of one or more dimensions with a volume. The further preliminary bladder data may comprise bladder pressure data over the preliminary time period.

[0054] Bladder pressure data may be used to identify when the bladder is at a maximum or minimum volume or to identify urination. The system may include a bladder pressure probe or sensor as part of the one or more sensors, the bladder pressure probe being configured to provide bladder pressure data to the one or more data modules, or the bladder pressure data may be received from a pressure probe that is separate to the system. The bladder pressure probe or sensor may be inserted through the skin of the subject as described above in relation to the ultrasound transducer. The system may include more than one bladder pressure probe or sensor. One bladder pressure probe or sensor may be configured to be inserted within the bladder, while another bladder pressure probe or sensor may be configured to be inserted outside of the bladder. The bladder pressure probe or sensor outside of the bladder may be implanted in the abdominal wall or in the bladder wall. Each bladder pressure probe or sensor, where there are more than one, may be configured to be inserted through the skin of the subject. More than one pressure probe may enable a reference pressure and a bladder pressure to be determined for comparison. Such data may provide further context for analysis of volume changes within the bladder.

[0055] The one or more data modules may be configured to determine a first time in the first time period indicating initiation of urination based on the bladder data and determine a second time in the first time period indicating cessation of the urination based on the bladder data. The one or more data modules may be configured to determine the one or more values for the parameter indicating urine flow between the first time and the second time.

[0056] Urination may be identified based on a change in volume. The first and second times may be identified based on when a rate of change of volume is above a threshold. The first and second times may alternatively be identified based on when the volume is above and below a threshold amount.

[0057] The one or more data modules are configured to determine a postvoid residual volume of the urinary bladder based on the bladder data. Postvoid residual volume may be determined based on a volume determined after urination. The postvoid residual volume may be a minimum volume of the urinary bladder.

[0058] The system may be an ambulatory system. An ambulatory system may be a system that allows the subject to be mobile and to walk or otherwise move around without being encumbered by bulky machinery or power sources. An ambulatory system may be a system that allows the subject to perform everyday activities without interference from the system. An ambulatory system may also be a system that allows for such activities for the duration of measurement by the system. For example, if the sensor is configured to remain within the subject for a prolonged period of time, then to be truly ambulatory the system must allow for the subject to be mobile and to perform everyday activities for that entire period. Accordingly, the system is designed to be portable and can be used outside of a clinical setting, allowing the subject to continue with their everyday life. The subject may be an outpatient. An ambulatory system may be a partially or fully wearable system, hence including the inserted (in vivo) sensor as well as wearable elements that can be carried by the user at the outside of the body. The one or more data modules may be wearable. The one or more sensors may be wearable. The term ‘wearable’ is intended to mean that portion that is wearable can be attached to and worn by the subject. Wearable systems are affixed to a part of the subject and move with movement of the subject. This differs from the term ambulatory, which means that the subject is able to move while the system is being used. A system may therefore be both ambulatory and wearable.

[0059] An ambulatory system may include an integral power supply. An ambulatory system may include an integral data storage device.

[0060] The system may comprise an attachment device for attaching at least one of the one or more data modules to the skin of the subject. An attachment device may comprise an adhesive patch. Such an attachment device may enable the system to be ambulatory and / or at least partially wearable.

[0061] The ultrasound transducer may have a biocompatible layer. The biocompatible layer may comprise one selected from: parylene; silicon oxide; titanium oxide; and diamond-like- carbon. The biocompatible layer may comprise a thin film. The biocompatible layer may comprise a coating. The biocompatible coating may comprise a sandwich structure, such as a coating formed by a thin film or by several layers of a thin film. The biocompatible layer may have a microscale or nanoscale thickness. The biocompatible layer may be for preventing or resisting corrosion of the transducer by tissue or body fluid. The biocompatible layer may be for resisting or preventing fouling of a surface of the transducer by tissue or body fluid.

[0062] The ultrasound transducer may have a coating for acoustic impedance matching, e.g. to reduce reflection and other unwanted effects as ultrasound travels from the fluid in the bladder to the material of the transducer. This coating may be of a single layer or a sandwich structure that provides acoustic impedance matching. This impedance-matching coating may reduce the risk of reflections from the ultrasound transducer being received and interpreted as reflections from the bladder. The impedance-matching coating may be particularly useful where more than one ultrasound transducer is used by reducing reflections of received signals and thereby avoiding anomalies in the measurements of another transducer. One possible coating system would include acoustic impedance matching layers deposited on the front surface of the transducer and a suitable backing layer between the rear surface and the substrate. The backing layer can be for absorbing the acoustic energy reflected from the substrate, which also can cause interference. A preferred coating for the front surface may be impedance-matching and with at least the outermost layer being biocompatible. Examples of such coatings are Parylene, AI2O3, TiCh or a combination of such materials.

[0063] The one or more sensors may comprise a pressure sensor configured to be inserted (e.g. inserted) in the subject and configured to detect a pressure of the urinary bladder, and wherein the bladder data includes measurements of the pressure of the urinary bladder over the first time period.

[0064] The pressure sensor may comprise a MEMS sensor. The pressure sensor may be a first pressure sensor. The one or more sensors may comprise a second pressure sensor. The second pressure sensor may be a reference pressure sensor. The first pressure sensor may be configured for insertion into the urinary bladder and the second pressure sensor may be configured for insertion into an abdominal region of the subject.

[0065] The pressure sensor may comprise a biocompatible layer.

[0066] The one or more sensors may comprise a sensor assembly. The sensor assembly may include the ultrasound transducer and the pressure sensor. The sensor assembly may comprise a first ultrasound transducer and a second ultrasound transducer. By “sensor assembly” it is meant that a plurality of sensors are provided at a shared or common body or housing, and are not provided as separate sensors. The sensors may be provided within or mounted to the housing. The sensors may be provided in the body of the sensor assembly. The sensor assembly may have a shared tubing through which a wire extends to connect to one or more data modules. The sensor assembly may include circuitry for each sensor. Where an ultrasound transducer and pressure sensor are provided as part of a sensor assembly, the transducers may be mounted to an exterior of a body or housing, and the pressure sensor may be provided within an opening in the body or housing that allows it to be in contact with body tissue or a body fluid when inserted within the subject. In the sensor assembly, the sensors may be in a fixed orientation and location relative to the housing, and may therefore be in fixed relative orientations and locations to one another. This may allow measurements from the sensors to be used to determine the dimensions precisely, and for the measurements to be comparable.

[0067] In examples, the sensor assembly may include the pressure sensor and a plurality of ultrasound transducers. One ultrasound transducer may be provided on an end of the housing and at least two ultrasound transducers may be provided at sides of the housing of the sensor assembly, such that each ultrasound transducer is orthogonal to the others. The sensor assembly may comprise five ultrasound transducers, one at the end, and four that are spaced evenly around a circumference of the housing.

[0068] In some examples, a sensor assembly may be provided that includes only ultrasound transducers. The pressure sensor may be provided separately.

[0069] The system may comprise an output module configured to transmit the one or more values for the parameter indicating urine flow into or out of the urinary bladder to a remote computing device for display to a user by a display device (e.g. a GUI) of the remote computing device.

[0070] The output module may comprise a transmitter. The output module may use a wired or wireless transmission means to transmit the one or more values to the remote computing device. The remote computing device may be a mobile device or a server.

[0071] The output module may be configured to transmit at least one of the bladder data and the volume of the urinary bladder to the remote computing device. Transmitting the bladder data and volume to the remote computing device may enable a physician to review it in addition to the one or more values for the parameter indicating urine flow and may therefore assist in diagnosis.

[0072] The system may comprise the remote computing device. The remote computing device may be configured to display a representation of the one or more values for the parameter indicating urine flow, the bladder data, or the volume of the urinary bladder on the display device in real time. Displaying values in real time may enable real-life events such as urination to be correlated with the data. The representation may be a value, a time series, or a graphical representation of the bladder. According to a second aspect, there is provided a computer-implemented method for monitoring urine flow of a subject. The method comprises: receiving bladder data from a one or more sensors that includes an ultrasound transducer configured to be inserted in the subject and to detect a first dimension of a urinary bladder of the subject, the bladder data comprising measurements of the first dimension of the urinary bladder over a first time period; determining a volume of the urinary bladder over the first time period based on the bladder data; and determining a parameter indicating urine flow into or out of the urinary bladder based on the volume of the urinary bladder over the first time period.

[0073] According to a third aspect, there is provided a computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method described above.

[0074] According to a fourth aspect, there is provided a computer-readable media comprising instructions, which, when executed by a computer, cause the computer to carry out the steps of the method described above.

[0075] Features described in relation to the first aspect may also be applied to the second, third, and fourth aspects.

[0076] There may also be provided a sensor assembly configured to be inserted in a urinary bladder of a subject. The sensor assembly may comprise a housing and at least one first ultrasound sensor mounted to the housing and configured to detect a first dimension of the urinary bladder, at least one second ultrasound sensor mounted to the housing and configured to detect a second dimension of the urinary bladder that is orthogonal to the first dimension, and at least one third ultrasound sensor mounted to the housing and configured to detect a third dimension of the urinary bladder that is orthogonal to the first dimension and the second dimension.

[0077] The housing may comprise an outer surface and an end surface. The first ultrasound transducer may be mounted to the housing at the end surface. The second ultrasound transducer and the third ultrasound transducer may be mounted to the housing on the outer surface. The outer surface may be cylindrical. The first ultrasound transducer may be configured to transmit and receive ultrasound signals in a first direction, the second ultrasound transducer may be configured to transmit and receive ultrasound signals in a second direction that is orthogonal to the first direction, and the third ultrasound transducer may be configured to transmit and receive ultrasound signals in a third direction that is orthogonal to the first and second directions. The at least one first ultrasound sensor may comprise two first ultrasound transducers mounted to the housing that together are configured to detect the first dimension. The at least one second ultrasound sensor may comprise two second ultrasound transducers mounted to the housing that together are configured to detect the second dimension. The at least one third ultrasound sensor may comprise two third ultrasound transducers mounted to the housing that together are configured to detect the third dimension. Where two ultrasound transducers are provided that are configured to detect a dimension, they may be provided on opposing sides of the housing, and may be arranged to transmit and receive ultrasound signals in opposite directions.

[0078] The above techniques may also be applied to other organs that have a filling and voiding cycle.

[0079] BRIEF DESCRIPTION OF DRAWINGS

[0080] Fig. 1 is a schematic diagram of a system for monitoring a bladder of a subject.

[0081] Fig. 2 is a method of determining a urine flow rate of a subject.

[0082] Fig. 3 is a chart illustrating a time series of a bladder volume.

[0083] Fig. 4 is a schematic diagram of a device for use in the system of Fig. 1.

[0084] Fig. 5 is an illustration of a sensor assembly for use in the system of Fig. 1 and the device of Fig. 4.

[0085] Fig. 6 is an illustration of a sensor assembly including a pressure sensor for use in the system of Fig. 1 and the device of Fig. 4.

[0086] DETAILED DESCRIPTION

[0087] Fig. 1 provides an overview of a system 100 for monitoring a urinary bladder 15 of a subject 10. The subject 10 is a human subject in this example. A urinary system 12 of the subject 10 is schematically depicted in Fig. 1, including a pair of kidneys 13, ureters 14, the urinary bladder 15 and a urethra 16. A physician 20 may desire to monitor the urinary bladder 15 to understand how urine flows into and / or out of the urinary bladder 15. The system 100 is used for such monitoring. The system 100 includes a plurality of sensors 110. The plurality of sensors 110 are here depicted as part of a single sensor assembly 111. The sensor assembly 111 has been inserted into the subject, and is positioned within an internal volume of the urinary bladder 15. The sensor assembly 111 has been inserted into the subject through the skin of the subject 10, through the abdominal wall of the subject 10, and through the bladder wall of the subject 10 to be provided within the internal volume of the urinary bladder 15. The sensor assembly 111 has therefore been implanted, and can be described as an implantable or configured for implantation.

[0088] The sensors of the sensor assembly 111 are not visible in Fig. 1, but include a pressure sensor configured to detect a pressure in the bladder and a plurality of ultrasound transducers configured to detect at least three dimensions of the bladder 15. The sensor assembly 111 may be said to include an array of ultrasound sensors, therefore, because the plurality of ultrasound transducers are arranged or configured to detect different dimensions of the bladder 15. This means that they have fixed locations relative to the sensor assembly and to one another. An example of such a sensor assembly 111 can be seen in Fig. 5, which is explained below. A reference pressure sensor may also be provided as part of the plurality of sensors 110, although this is not shown in Fig. 1 to preserve clarity in Fig. 1.

[0089] The plurality of sensors 110 are in communication with one or more data modules 120. In this example, the communication is by means of a wired connection 125, although in other examples the connection may be wireless. The one or more data modules 120 depicted in Fig. 1 include a data collection module 121 and a data analysis module 122. The data collection module 121 receives bladder data 115 from the plurality of sensors 110. The bladder data 115 includes measurements of a first dimension 116 of the urinary bladder 15, received from a first ultrasound transducer, measurements of a second dimension 117 of the urinary bladder 15, received from a second ultrasound transducer, and measurements of a third dimension 118 of the urinary bladder 15, received from a third ultrasound transducer. The bladder data 115 also includes measurements of a pressure 119 of the urinary bladder 15. The measurements 116-119 are made over a first time period. Although not depicted in Fig. 1, the bladder data 115 also includes timestamps corresponding to the measurements taken over the first time period and may include data relating to the sensors 110, such as calibration data.

[0090] The data collection module 121 may receive and collate the bladder data 115 from the open or more sensors 110. The bladder data 115 is then provided to the data analysis module 122 for analysis. The data analysis module 122 may determine parameters associated with the urinary bladder 15 based on the bladder data 115. Fig. 1 shows four such parameters. A first parameter is a volume, V, of the urinary bladder over the first time period. The volume, V, is determined based on the first, second, and third dimensions 116-118 and is determined according to a predetermined formula. In Fig. 1, the bladder 15 is being modelled as a cuboid, and the dimensions are represented as such, meaning that the predetermined formula for determining the volume is that of a cuboid.

[0091] The data analysis module 122 also determines a parameter indicating urine flow into or out of the urinary bladder based on the volume, V, of the urinary bladder 15 over the first time period. The parameter is urine flow rate, Q, in the example of Fig. 1. The urine flow rate indicates how quickly the urinary bladder 15 empties or fills. The data analysis module 122 determines the urine flow rate, Q, by determining a rate of change of the volume, V, over the first time period. The urine flow rate, Q, is then determined by converting the rate of change of volume to a flow rate.

[0092] The data analysis module 122 can also determine a postvoid residual volume, PVR, using the bladder data 115 and one or more pressure parameters, p, such as average pressure over the first time period, maximum or minimum pressures, or instantaneous pressure values at points within the first time period corresponding to the changes in the volume or changes in the urine flow rate.

[0093] The system 100 includes a data output module 140 in communication with the one or more data modules 120. The data output module 140 receives data, including the parameters such a V, Q, etc., from the data analysis module 122 and optionally the bladder data 115, and outputs it to one or more locations. In the example of Fig. 1, the data output module 140 outputs the data to a remote computing system 150. The remote computing system 150 includes a display device 160 and the data received by the remote computing system 150 can be displayed on the display device 160 to allow the physician 20 to view it. The system 100 may include data storage 170. The data analysis module 122 may store the parameters it has determined in the data storage 170. The data analysis module 122 may store the bladder data 115 in the data storage 170. The data storage 170 may be local to the data analysis module 122, and so may be stored directly. Alternatively, the data storage 170 may be remote from the data analysis module 122 and so the parameters and / or bladder data 115 may be stored in the data storage 170 by outputting the data via the data output module 140. Alternatively, or additionally, the data collection module 121 may store the bladder data 115 in the data storage 170.

[0094] Fig. 2 provides a flow chart summarizing a general method 200 that can be performed by one or more data modules, such as the one or more data modules 120 in Fig. 1. The method 200 includes step 210, in which bladder data is received from one or more sensors. Generally, the one or more sensors include at least one ultrasound transducer configured to be inserted in the subject and to detect a first dimension of a urinary bladder of the subject. The bladder data comprises measurements of the first dimension of the urinary bladder over a first time period. As shown in Fig. 1, the one or more sensors can comprise more than a single ultrasound transducer, and the bladder data can comprise measurements of multiple dimensions as well as further data, such as pressure data.

[0095] In step 220 of the method 200, a volume of the urinary bladder over the first time period is determined based on the bladder data.

[0096] Step 230 of the method 200 follows step 220, and in this step, a parameter indicating urine flow into or out of the urinary bladder is determined based on the volume of the urinary bladder over the first time period.

[0097] In Fig. 2, step 230 is shown as being able to be split into two further steps 231 and 232. These further steps 231, 232 represent the case where the parameter indicating urine flow is a urine flow rate. In this case, in step 231, a rate of change of volume of the urinary bladder over the first time period is determined based on the volume of the urinary bladder, and, in step 232, the urine flow rate is determined based on the rate of change of volume of the urinary bladder. The urine flow rate may be an average urine flow rate, a maximum urine flow rate, or a minimum urine flow rate over the first time period. Fig. 3 indicates how volume measurements may be used to determine a rate of change of volume, for the purpose of determining a urine flow rate, as in steps 231 and 232 of the method 200.

[0098] A chart 300 of volume, V, of a urinary bladder over time, T, is shown in Fig. 3. A time period between time to and time t? is shown. The volume, V, may have been determined using a data analysis module, such as the data analysis module 122 of Fig. 1, and based on bladder data, such as bladder data 115.

[0099] At time to, the urinary bladder is at a minimum volume, Between times ti and t2, the volume increases to reach a maximum volume, vmax, as urine flows into the bladder. The period between ti and t2 may therefore be classified as a filling event or filling phase. Between t2 and t3, there is a voiding phase or event, in which urination occurs and the volume of the bladder decreases from vmax back to Vmin as urine is expelled from the bladder.

[0100] The rate of change of volume during the voiding phase, which is denoted as A in Fig. 3, can be calculated based on the change of volume over the time period corresponding to the voiding phase. Accordingly, the rate of change of volume is the difference between vmax and Vmin divided by the difference between t3 and t2, giving the equation A=(vmax-vmin) / (t3- t2) as shown in Fig. 3. The rate of change of volume can subsequently be converted to a flow rate

[0101] The rate of change of volume may also be determined for other phases such as filling phases. It will be appreciated that this system can allow for new information to be gathered that can help with assessment of various issues, including by permitting monitoring of changes in both pressure and volume, where there is a correlation in both the filling phase and in the voiding phase. For example, in the voiding phase information about volume can aid in seeing certain relationships that might indicate different problems: high pressure (HP) - low flow (LF) can relate to an obstruction, HP / HF can forewarn of bladder collapse, LP / HF could be an indicator for urinary incontinence, and LP / LF might indicate a collapsed bladder. Being able to see volume changes as well as rates of change will evidently be of great value.

[0102] Fig. 1 illustrates the system 100 schematically to enable the functions and interactions of the different modules to be clearly seen. Fig. 4 shows an example configuration 101 of the system 100, in which the data modules 120, output module 140, and data storage 170 are provided as part of a wearable device 130. The remote computing system 150 is not shown in Fig. 4, and for the purposes of this example, is not considered to be part of the system configuration 101. Providing a wearable device 130 and an implantable / insertable set of sensors 110 results in the system being an ambulatory system, enabling the urinary bladder 15 to be monitored while the subject 15 goes about their daily life as normal and while the urinary bladder 15 is used under normal conditions. This is in contrast to being artificially filled, or utilizing devices that measure expelled urine and so can only measure discrete events.

[0103] Fig. 4 shows the subject 10 and their urinary system 11, including the urinary bladder 15. As in Fig. 1, sensors 110 are provided in the form of a sensor assembly 111 that has been inserted within an internal volume of the urinary bladder 15.

[0104] A wired connection 125 connects the sensor assembly 111 to the wearable device 130. In use, the wired connection 125 may extend from the sensor assembly 111 through the tissue of the subject, i.e. through the bladder wall, through the abdominal wall, and through the skin of the subject to connect to the wearable device 130. The wearable device 130 is provided externally to the subject’s body, and is adhered to a patch of skin of the subject using an attachment device 135, here depicted as an adhesive patch. Several modules are attached to the adhesive patch, including the data modules 120, the data storage 170, the output module 140, and a power supply 180. The data modules 120 are configured to receive data from the sensors 110 and to perform a method such as the method 200 of Fig. 2. The data modules 120 may subsequently store bladder data and analysis data in the data storage 170, and the output module 140 may transmit the data from the data storage 170 over a wired or wireless connection as appropriate to a remote computing system.

[0105] Figs. 5 and 6 illustrate example sensor assemblies. Fig. 5 illustrates a sensor assembly 511 that includes a plurality of ultrasound sensors and a pressure sensor. The sensor assembly 511 can be used as the sensor assembly 111 of Figs. 1 and 4.

[0106] The sensor assembly 511 of Fig. 5 includes a housing 512, a plurality of ultrasound transducers 520 mounted on the housing 512, and a pressure sensor 530 provided in the housing. The housing 512 has a cylindrical or oval outer surface 513 and a portion 514 that includes an opening. The portion 514 has an end surface 515.

[0107] The pressure sensor 530 is positioned within the housing 512 beneath the opening. The opening allows a pressure element 531 of the pressure sensor 530, which may be a diaphragm or membrane and which is for the purpose of sensing the pressure within the bladder, to sense pressure applied by a fluid or tissue, such as the urine within the bladder. The housing 512 may have a seal that seals off a remainder of the inside of the housing 512 to prevent the fluid or tissue interacting with the interior of the housing 512, although this is not shown in Fig. 5 to preserve clarity. The pressure sensor 530 and the pressure sensors referred to throughout this application may be any suitable pressure sensor. An example pressure sensor is described in International Patent Application PCT / EP2016 / 075990, published as WO 2017 / 072261 Al, and titled “Sensor Assembly”.

[0108] The ultrasound transducers 520 comprise a first ultrasound transducer 521 configured to detect a first dimension of a urinary bladder, two second ultrasound transducers 522-1 and 522-2 configured to detect a second dimension of the urinary bladder, and two third ultrasound transducers 523-1 and 523-2 configured to detect a third dimension of the urinary bladder. The ultrasound transducers 520 and the ultrasound transducers described herein more generally may be any suitable ultrasound transducers, including piezoelectric or capacitive ultrasound sensors, and particularly piezoelectric micromachined ultrasound transducers (PMUTs) or capacitive micromachined ultrasound transducers (CMUTs).

[0109] The first ultrasound transducer 521 is provided on the end surface 515 of the portion 514 including the opening. The first ultrasound transducer 521 is therefore positioned to point in a first direction.

[0110] The second transducers 522-1, 522-2 and the third transducers 523-1, 523-2 are provided on the cylindrical outer surface 513. The second transducers 522-1, 522-2 are provided on opposite sides of the outer surface 513. The second transducers 522-1, 522-2 therefore point in opposite directions and are aligned with one another along a diameter of the housing 512. The second transducers 522-1, 522-2 are oriented to be orthogonal to the first ultrasound transducer 521, thereby allowing a second dimension to be gathered. The second transducers 522-1, 522-2 may therefore each transmit and receive an ultrasound signal. The second dimension may be determined to be the sum of a distance from one of the second transducers 522-1 to a wall of the bladder, a distance from the other of the second transducers 522-2 to an opposite wall of the bladder, and a distance between the second transducers 522-1, 522-2.

[0111] The third transducers 523-1, 523-2 are also provided on opposite sides of the cylindrical outer surface 513, and are oriented to be orthogonal to the second transducers 522-1, 522- 2 and the first transducer 521. The second transducers 522-1, 522-2 and the third transducers 523-1, 523-2 are therefore evenly spaced around the housing 512, so that each second transducer 522-1, 522-2 is between the third transducers 523-1, 523-2 around the housing 512 and vice versa. The third transducers 523-1, 523-2 therefore allow a third dimension to be determined, as the sum of a distance from one of the third transducers 523- 1 to a wall of the bladder, a distance from the other of the third transducers 523-2 to an opposite wall of the bladder, and a distance between the third transducers 523-1, 523-2.

[0112] The ultrasound transducers 520 and the pressure sensor 530 are connected by connectors 540 to a circuit board 550, which may include circuits controlling switching of the transducers 520 and collation of measurements of dimensions and pressure from the transducers 520 and sensor 530. The assembly 511 also includes a flexible connector 560 to connect the circuit board 550 to one or more data modules.

[0113] The transducers 520 and pressure sensor 530 are fixed in position within the housing 512 so that their location and orientation relative to the housing 512 and relative to each other are known. The sensor assembly 511 may therefore be said to include an ultrasound array.

[0114] Although not visible in Fig. 5, at least the transducers 520 and the pressure sensor 530 have a biocompatible coating or layer. The layer may be applied to the entire sensor assembly 511. An impedance-matching layer may also be applied to some or all of the sensor assembly 511.

[0115] In some examples, ultrasound transducers and pressure sensors may be provided separately. The ultrasound transducers may be provided in a sensor assembly, such as the sensor assembly 611 shown in Fig. 6.

[0116] The sensor assembly 611 includes some similar features to the assembly 511 of Fig. 5, and these features are labelled with the same reference numerals. For example, the sensor assembly 611 includes connections 540, a circuit board 550 and a flexible connector 560. The sensor assembly 611 differs from the sensor assembly 511 because it comprises only ultrasound transducers 620. The sensor assembly 611 has a housing 612 with a cylindrical outer surface 613 and an end surface 615. The cylindrical outer surface might have a circular profile, or it might be an alternative shape, such as with an oval or elliptical crosssection. A first ultrasound transducer 621 is provided on the end surface 615 and is configured to detect a first dimension of a urinary bladder. Two second ultrasound transducers 622-1, 622-2 and two third ultrasound transducers 623-1, 623-2 are provided on the outer surface 613, and are configured to detect a second and third dimension of a urinary bladder. The second ultrasound transducers 622-1, 622-2 and two third ultrasound transducers 623-1, 623-2 are arranged around the housing 612 in the same way as the second and third ultrasound transducers 522-1, 522-2, 523-1, 523-2 in the sensor assembly 511 described above in relation to Fig. 5.

[0117] As the sensor assembly 611 includes a plurality of ultrasound sensors 620 having a fixed relationship, the sensor assembly 611 may be referred to as a sensor array, or as including a sensor array.

[0118] While sensor assemblies 111, 511, 611 are described and shown in this application, in other examples the plurality of sensors 110 may be provided individually or combined in any suitable way.

[0119] Although five or six sensors are provided in the examples above, the number of sensors may be varied. Some systems and devices may include a single ultrasound transducer arranged to determine a dimension of the bladder. Other systems and devices may include two or three ultrasound transducers, or more, and may include other sensors including but not limited to pressure sensors.

Claims

CLAIMS1. A system (100) for monitoring urine flow of a subject (10), the system (100) comprising: one or more sensors (110) comprising an ultrasound transducer (111; 521; 621) configured to be inserted in the subject (10) and to detect a first dimension (116) of a urinary bladder (15) of the subject (10); and one or more data modules (120) that are in communication with the one or more sensors (110), wherein the one or more data modules (120) are configured to: receive (210) bladder data (115) from the one or more sensors (110), the bladder data (115) comprising measurements of the first dimension (116) of the urinary bladder (15) over a first time period; determine (220) a volume and / or a change in volume of the urinary bladder (15) over the first time period based on the bladder data (115); and determine (230) one or more values for a parameter indicating urine flow into or out of the urinary bladder (15) based on the volume and / or change in volume of the urinary bladder (15) over the first time period.

2. The system (100) of claim 1, wherein the one or more data modules (120) are configured to determine (231) a rate of change of the volume of the urinary bladder (15) over the first time period, the one or more values for the parameter indicating urine flow being based on the rate of change of the volume of the urinary bladder (15).

3. The system (100) of claim 2, wherein the rate of change of volume is the parameter indicating urine flow.

4. The system (100) of claim 1 or claim 2, wherein the parameter indicating urine flow is a urine flow rate.

5. The system (100) of any preceding claim, wherein the ultrasound transducer is a first ultrasound transducer (111; 521; 621) and wherein the one or more sensors (110) comprises a second ultrasound transducer (522-1; 622-1) configured to be inserted in the subject (10) and to detect a second dimension (117) of the urinary bladder (15), the second dimension (117) being different to the first dimension (116), wherein the bladder data (115) comprises a plurality of measurements of the second dimension (117) of the urinary bladder (15) over the first time period.

6. The system (100) of claim 5, wherein the one or more data modules (120) are configured to determine the volume of the urinary bladder (15) over the first time period based on a predetermined volume formula that includes the at least the first dimension (116) and the second dimension (117).

7. The system (100) of claim 5 or claim 6, wherein the one or more sensors includes an ultrasound array, wherein the ultrasound array includes the first ultrasound transducer (111; 521; 621) and the second ultrasound transducer (522-1; 622-1).

8. The system (100) of any preceding claim, wherein the one or more data modules (120) are configured to: receive preliminary bladder data from the one or more sensors (110), the preliminary bladder data comprising measurements of the first dimension (116) of the urinary bladder (15) over a preliminary time period that is before the first time period; and determine a relationship between at least the first dimension (116) and a volume of the bladder based on the preliminary bladder data, wherein the volume of the urinary bladder (15) over the first time period is based on the relationship.

9. The system (100) of any preceding claim, wherein the one or more data modules (120) are configured to: determine a first time in the first time period indicating initiation of urination based on the bladder data (115); determine a second time in the first time period indicating cessation of the urination based on the bladder data (115); determine the one or more values for the parameter indicating urine flow between the first time and the second time.

10. The system (100) of any preceding claim, wherein the one or more data modules (120) are configured to determine a postvoid residual volume of the urinary bladder (15) based on the bladder data (115).

11. The system (100) of any preceding claim, wherein the system (100) is an ambulatory system.

12. The system (100) of any preceding claim, wherein the ultrasound transducer (111; 521; 621) has an impedance matching and / or biocompatible layer.

13. The system (100) of any preceding claim, wherein the one or more sensors (110) comprise a pressure sensor (530) configured to be inserted in the subject (10) and to detect a pressure of the urinary bladder (15), and wherein the bladder data (115) includes measurements of the pressure (119) of the urinary bladder (15) over the first time period.

14. The system (100) of claim 13, wherein the one or more sensors comprises a sensor assembly (111), wherein the sensor assembly (111) includes the ultrasound transducer (112) and the pressure sensor (105).

15. The system (100) of any preceding claim, wherein the ultrasound transducer (111; 521; 621) is configured to be implanted in the subject (10).

16. The system (100) of claim 15, wherein the ultrasound transducer (111; 521 ;621 ) is configured to be implanted into an interior volume of the urinary bladder (15) through a bladder wall of the urinary bladder (15).

17. The system (100) of any preceding claim, further comprising a transcutaneous introducing device for inserting the ultrasound transducer in the subject.

18. A computer-implemented method (200) for monitoring urine flow of a subject (10), the method (200) comprising: receiving (210) bladder data (115) from a one or more sensors (110) that includes an ultrasound transducer (111; 621; 621) configured to be inserted in the subject (10) and to detect a first dimension (116) of a urinary bladder (15) of the subject (10), the bladder data (115) comprising measurements of the first dimension (116) of the urinary bladder (15) over a first time period; determining (220) a volume of the urinary bladder (15) over the first time period based on the bladder data (115); and determining (230) a parameter indicating urine flow into or out of the urinary bladder (15) based on the volume of the urinary bladder (15) over the first time period.

19. A computer program product comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method (200) of claim 18.

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