The invention relates to a method of recording the bladder volume in humans or animals.
The invention moreover relates to an apparatus for recording the bladder volume in humans or animals.
The techniques used till now for determining the volume of the bladder in humans or animals comprise the generally known image diagnostic techniques based on e.g. magnet resonance (MR), X-ray, nuclear medicine or ultrasound.
However, it is characteristic of these techniques that they call for the use of heavy and large equipment which normally requires that the patient is confined to bed during the measurement.
Ultrasound equipment is available which can measure the volume of the bladder in ambulatory patients. This equipment is based on the use of a single ultrasound transducer, which rotates the transducer over the patient's bladder mechanically by means of a gear system driven by an electric motor, such that the entire bladder is scanned, and then, via signal processing in a computer, a three-dimensional (3D) reconstruction of the surface of the bladder and thereby also the volume of the bladder may be created.
The ultrasound measuring equipment driven by an electric motor is portable in the sense that the equipment is fixed in a belt which is tightened around the patient on whom measurements are to be performed. The system, however, is relatively large and heavy because of the mechanical components used for the rotation of the ultrasound transducer and therefore not comfortable for the patients to wear.
Also, the bulky structure with the complicated, mechanical movements means that the apparatus will inevitably generate mechanical noise which may also be unpleasant to the patient.
The mechanically complicated structure will moreover be vulnerable to external impacts, which may occur if the unit is e.g. dropped. The complicated structure will also be expensive to manufacture and require relatively great current maintenance costs.
The operation by an electric motor will require considerable electrical power, which means that batteries for the energy supply must be large and heavy, which in turn makes it difficult and inconvenient to use the apparatus in practice.
Thus, it is a problem of the known techniques that they cannot be used in practice for long term monitoring of ambulatory patients, which is a great clinical need, e.g. in connection with the evaluation of the effect of recently developed medicine.
Both in a research and a clinical connection there is a great need for long term monitoring of the bladder volume in patients where it is attempted to diagnose various bladder and urinary tract disorders.
Another great need for long term monitoring of the volume of the bladder with a user-friendly easily portable apparatus is found in patients who suffer from involuntary nocturnal incontinence.
If these individuals could be equipped with a small, simple and non-hampering measuring device which could measure the volume of the bladder continuously and emit a signal when the bladder reached a preselected maximum volume, the individuals would have an alarm that woke them before the urinary incontinence was initiated, so that the individuals could urinate in time and thereby avoid the inconvenience of the otherwise occurring urinary incontinence.
Urinary nocturnal incontinence is a great problem for up to 15% of all children aged 3-10 years.
It is an object of the present invention to enable continuous measurement of the volume of the bladder in humans or animals who or which move about free and easy or are at sleep.
The object of the invention is achieved by a method of the type defined in the introductory portion of claim 1, which is characterized in that the recording takes place on the basis of analysis of signals from two or more ultrasound transducers which are arranged in a portable fixture, such as a belt or a waistband of a pair of trousers, which is attached to the individual being measured, and in that each transducer, by signal sweep, images a plane in the body of the individual being measured, which in one dimension, runs radially from each individual transducer to the centre of a circle on which all the transducers are positioned.
Expediently, as stated in claim 2, the transducers used are fixed mechanically as phased-array units.
Thus, use of a phased-array ultrasound transducer is involved, which is characteristic in that it does not contain mechanically moveable components, but are composed of several ultrasound units, typically of piezoelectric crystals, arranged in parallel. Thus, without mechanically movable parts, a phased-array ultrasound transducer may perform scanning in a plane, in the longitudinal direction, in which the piezoelectric crystals are arranged, by individual excitation of the individual crystals with a time delay between each excitation. The scanning is performed between two extreme angles which are determined by the time delay between the excitations of the individual crystals.
The mechanically fixed transducers are arranged in the portable fixture as defined more fully in claims 3-4. In other words, in such a manner that the scanning planes of the transducers, which are the region in which the ultrasound signals are emitted and detected after reflection from transitions between tissues of different density, cover the bladder of the individual.
When, as stated in claim 5, the signals from the ultrasound transducers are processed in an electronic circuit which is integrated in the fixture, and which calculates the volume of the bladder and is capable of emitting a signal if the volume exceeds a preselected maximum, it is advantageously ensured that it is possible to preselect a maximum volume for the bladder which, if exceeded, triggers an alarm.
As mentioned, the invention also relates to an apparatus.
This apparatus is characterized in that the apparatus contains two or more mechanically fixed ultrasound transducers of the phased-array type, and in that each transducer, by signal sweep, images a plane in the body of the individual being measured, which, in one dimension, is described by a line extending through the transducer and the central line extending through the centre of a circle line on which the transducer is positioned, said transducers being arranged in a portable fixture, such as a belt or a waistband of a pair of trousers, which may be attached to the individual being measured, as well as a calculation unit which is capable of calculating the volume of the bladder on the basis of the signals from the ultrasound transducers.
As stated in claim 7, the apparatus may contain two transducers which are positioned on a common circle line with a spacing of 90°, whereby the scanning planes for the transducers can cover the entire bladder, allowing subsequent 3D reconstruction of the external shape and volume of the bladder.
As stated in claim 8, the apparatus may also be provided with three or more phased-array ultrasound transducers which are positioned equidistantly on a common circle line.
When, as stated in claim 9, the transducers are positioned on a common circle line in such a manner that lines of sight pointing perpendicularly out from the centre of the active surface of each transducer in a direction toward the object to be measured, will extend through the same point on the centre line extending through the centre of the circle on which all the transducers are positioned.
As stated in claim 10, the fixture of the apparatus has integrated therein electronic circuits which are used for controlling the transducers and for processing the signals from the transducers, which electronic circuits may be connected to an input medium, such as a keyboard, and an output medium, such as a sound generator or vibrator, thereby allowing the recorded signals to be processed. In addition, the electronic circuits may input and output data, if the input and output media are connected thereto. The electronic circuits may thus be used for emitting e.g. an acoustic alarm signal, if the bladder volume exceeds a preselected maximum.
When, as stated in claim 11, the belt has integrated therein electronic circuits which are capable of wirelessly communicating with external units, such as computers or mobile telephones, the keyboard of the mobile telephone may e.g. be used as an input medium for inputting data, e.g. to describe how large the volume of a bladder must be as a basis for the triggering of an alarm.
In the example involving communication with a mobile telephone, an alarm signal may of course also be given via the mobile telephone in the form of a call or vibrator activation.