Detection of implanted wireless energy receiving device

The present invention relates to an apparatus and method for detecting a wireless energy receiving device subcutaneously implanted in a patient to enable accurate positioning of an exterior wireless energy transmission device.

In new generations of energy consuming implants wireless energy transmission may be used for supply of energy to such implants. To optimise the transfer efficiency of the wireless energy it is important to locate the wireless energy receiver, typically subcutaneously implanted in the patient, in order to be able to put an exterior energy transmission device close to the implanted energy receiving device. Document <patcit id="pcit0001" dnum="US5314453A"><text>US-A-5 314 453</text></patcit> shows an arrangement for localising an implanted receiver coil and aligning a transmitter antenna coil with the former. The arrangement includes a magnet placed concentrically within the implanted receiver coil and a reed switch as magnetic field sensing device placed within the transmitter antenna coil.

The object of the present invention is to provide an inexpensive apparatus for accurate detection of a wireless energy receiving device subcutaneously implanted in a patient, and further to provide an apparatus with parts to be implanted that are relatively small.

This object is obtained by an apparatus as defined in claim 1, comprising a magnetic device adapted to emit a local magnetic field, and a magnetic detector adapted to detect the local magnetic field emitted by the magnetic device. The magnetic device is designed to be subcutaneously implanted in the patient at the implanted energy receiving device, and the magnetic detector is movable externally along the patient's body to establish an energy transmission position at the patient's skin where the local magnetic field emitted by the magnetic device is detected by the magnetic detector. Alternatively, the magnetic detector is designed to be subcutaneously implanted and the magnetic device is movable along the patient's body to establish the energy transmission position at the patient's skin where the local magnetic field emitted by the magnetic device is detected by the magnetic detector. As a result, the wireless energy transmission device can be put in the established energy transmission position, in order to efficiently transmit wireless energy to the implanted energy receiving device.

Thus, the present invention provides an easy way of detecting the position of the wireless energy receiving device subcutaneously implanted in a patient, which enables accurate positioning of the wireless energy transmission device outside the patient's body for efficient transmission of wireless energy to the implanted energy receiving device by using magnetism. Typical applications for such an energy receiving device are for energizing an implant in the patient, for example for treating reflux disease, obesity, anal or urinary incontinence, or impotence. The apparatus of the invention may conveniently be used for detecting an implanted energy receiving device coupled to such implants.

In accordance with a main first embodiment of the invention, the magnetic device is designed to be subcutaneously implanted in the patient at the implanted energy receiving device to emit the local magnetic field through a portion of the patient's skin adjacent to the energy receiving device, and the magnetic detector is movable externally along the patient's body to establish the energy transmission position where the local magnetic field is detected by the magnetic detector. Suitably, the magnetic detector is adapted to establish the energy transmission position at least substantially in front of the subcutaneously implanted energy receiving device to enable a most efficient energy transmission. The magnetic detector may be adapted to emit a sound when detecting the local magnetic field. Alternatively, the magnetic detector may be provided with at least one diode adapted to emit light when the detector detects the local magnetic field, or be provided with a display adapted to indicate when the detector detects the local magnetic field.

In accordance with a second embodiment of the invention, the magnetic detector is designed to be subcutaneously implanted in the patient at the implanted energy receiving device, and the magnetic device is adapted to emit the local magnetic field through the patient's skin from outside the patient's body and is movable externally along the patient's body to establish the energy transmission position where the local magnetic field is detected by the implanted magnetic detector. Also in this second embodiment the magnetic device is suitably adapted to establish the energy transmission position at least substantially in front of the subcutaneously implanted energy receiving device. In its simplest form, the implanted magnetic detector may be adapted to emit a sound when detecting the local magnetic field. In a more sophisticated form, a sender may be implantable in the patient's body and be capable of sending information about the magnetic detector to outside the patient's body, as the magnetic detector detects the local magnetic field emitted by the magnetic device from outside the patient's body. For example, the implanted sender may send RF signals that inform when the implanted detector detects the local magnetic field, whereby an accurate energy transmission position at the patient's skin can be established. The accurate energy transmission position may be directly or indirectly correlated to the intensity of magnetism detected by the magnetic detector.

The magnetic device may be a solenoid or a permanent magnet, which is sending out a magnetic field.

In any of the above embodiments the magnetic detector includes a semiconductor circuit, preferably in the form of at least one Hall-element. By using one or more Hall-elements, a special type of semiconductor known in the art, it is easy to locate the centre of the magnetic field emitted by the magnetic device. The magnetic detector suitably comprises several Hall-elements grouped around a central point in a triangular or square configuration. For example, three Hall-elements may be arranged at the corners of an equilateral triangle. An important advantage is that the Hall-elements are able to detect even a weak magnetic field emitted from the magnetic device.

The apparatus of the present invention is useful in a method of detecting a wireless energy receiving device subcutaneously implanted in a patient. The method comprises providing a magnetic device capable of emitting a local magnetic field through the patient's skin, providing a magnetic detector adapted to detect the local magnetic field emitted by the magnetic device, subcutaneously implanting the magnetic device or magnetic detector in the patient at the implanted energy receiving device, moving the magnetic detector or magnetic device externally along the patient's body, and establishing an energy transmission position at the patient's skin where the local magnetic field emitted by the magnetic device is detected by the magnetic detector. Then, the energy transmission device can be positioned in the established energy transmission position where the local magnetic field has been detected to efficiently transmit wireless energy to the subcutaneously implanted energy receiving device.

Where the magnetic detector is subcutaneously implanted and the magnetic device is moved along the patient's body, the method may further comprise implanting a sender and using the sender to send information to outside the patient's body confirming when the implanted magnetic detector detects the local magnetic field emitted by the exterior magnetic device.

The apparatus of the present invention may also be used in a surgical method for treating a patient having a disease, comprising the steps of: insufflating the patient's abdomen with gas; placing at least two laparoscopic trocars in the patient's body; implanting an operable implant designed for treating reflux disease, urinary incontinence, impotence, anal incontinence or obesity in the abdomen by using surgical instruments through the trocars; subcutaneously implanting a wireless energy receiving device for supplying energy for use in the operation of the implant and a magnetic device at the energy receiving device for emitting a local magnetic field through the adjacent skin portion of the patient; post-operatively moving an exterior magnetic detector along the patient's body to establish an energy transmission position in which the local magnetic field emitted by the implanted magnetic device is detected by the magnetic detector; bringing a wireless energy transmission device to the established energy transmission position; and transmitting wireless energy from the wireless energy transmission device through the patient's skin to the implanted wireless energy receiving device.

As an alternative, the surgical method may comprise subcutaneously implanting a magnetic detector at the energy receiving device and post-operatively moving an exterior magnetic device emitting a local magnetic field along the patient's body to establish the energy transmission position in which the local magnetic field emitted by the exterior magnetic device is detected by the implanted magnetic detector.

The skilled person should appreciate that the detection technique described above is simple, inexpensive and very accurate, and could be used for several different implants in combination with wireless energy transmission.

The invention is described in more detail in the following with reference to the accompanying drawings, in which <ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Fig.1</figref> shows a connection diagram for a magnetic detector of the apparatus according to the present invention,</li><li><figref idref="f0002">Fig.2</figref> schematically illustrates in a diagram the output of the magnetic detector positioned in front of a magnetic device of the apparatus of the invention,</li><li><figref idref="f0003">Fig. 3</figref> is a schematic view of an embodiment where the magnetic device is subcutaneously implanted in a patient, and the magnetic detector is movable externally along the patient's body,</li><li><figref idref="f0004">Fig. 4</figref> is a schematic view of an embodiment where the magnetic detector is subcutaneously implanted in the patient and the magnetic device is movable externally along the patient's body,</li><li><figref idref="f0005">Fig. 5</figref> is a schematic view of a hydraulically adjustable constriction device designed for treating reflux disease, urine incontinence, anal incontinence or obesity, and</li><li><figref idref="f0005">Fig. 6</figref> illustrates an embodiment according to the present invention using Hall-elements as the magnetic detecting device.</li></ul>

Referring to the drawing figures, like reference numerals designate identical or corresponding elements throughout the several figures.

DETAILED DESCRIPTION OF THE INVENTION

<figref idref="f0001">Fig. 1</figref> shows a connection circuit 1 for a magnetic detector 2 of the apparatus according to the present invention. A magnetic device in the form of a ring-magnet 3, which can be a solenoid or a permanent magnet, is implanted in a patient's body. Located outside the body and positioned in front of the implanted ring-magnet 3 is magnetic detector 2, which includes three linear magnetic field sensors 4 (such as Hall-elements or the like) grouped in a triangular configuration. Sensors 4 are connected to signal-conditioning amplifiers 5, which in turn, are connected to an A/D-converter 6. A microprocessor 7 is connected to A/D-converter 6. To visually display the output signals of sensors 4, a display-device 8 is connected to microprocessor 7.

The graph shown in <figref idref="f0002">Fig. 2</figref> illustrates, in principle, how the information obtained by detector 2 can be presented. On the X-axis in the graph is the position of detector 2 relative to the magnetic device. On the Y-axis is the combined output of sensors 4 of detector 2. Thus, the graph of <figref idref="f0002">Fig. 2</figref> shows the position "X" of detector 2 relative to the magnetic device as a function of detector 2's output "Y". To illustrate this method of detecting, a magnetic device in the form of a ring-magnet 9 is shown relative to the graph of <figref idref="f0002">Figure 2</figref>. Ring-magnet 9 is shown in cross-section to show the positions of its magnetic north pole N and south pole S, respectively. <figref idref="f0002">Fig. 2</figref> depicts the case where magnetic detector 2 (not shown in <figref idref="f0002">Fig. 2</figref>) has been centred in front of ring-magnet 9 and where all of the sensors 4 produce a maximum output, which is shown as peaks 10,11 in the graph of <figref idref="f0002">Fig. 2</figref>. Sensors 4 are connected (e.g., by connection circuit 1 shown in <figref idref="f0001">Fig. 1</figref>) to display device 8, which may display the graph shown in <figref idref="f0002">Fig. 2</figref>, or alternatively, a numeral result from the measurements taken by sensors 4.

<figref idref="f0003">Fig. 3</figref> shows an embodiment of the apparatus of the present invention for detecting a wireless energy receiving device 12 subcutaneously implanted in a patient 13 suffering from anal incontinence to enable accurate positioning of a separate wireless energy transmission device 14 outside patient 13's body for the transmission of wireless energy to energy receiving device 12. An operation device 19 is adapted to operate an implanted artificial sphincter 18 applied to the patient's rectum 20. Energy receiving device 12 powers operation device 19 with energy received from the energy transmission device 14. The implanted energy receiving device 12 may be of the type that transforms the received energy into electrical pulses. In this case, a sender may be implanted in the patient for sending feedback information on the number of electrical pulses that have been provided by the energy receiving device. The apparatus also includes a magnetic device 15 subcutaneously implanted in patient 13 close to the energy receiving device 12. Magnetic device 15 emits a local magnetic field extending through a portion of patient 13's skin 16 adjacent to energy receiving device 12. The apparatus further includes an external, separate magnetic detector 17 that may be manually moved along the patient 13's body to establish an energy transmission position at the patient's skin where the local magnetic field emitted by magnetic device 15 is detected by magnetic detector 17. When this energy transmission position has been established, energy transmission device 14 can be located in the same position to efficiently transmit wireless energy to implanted energy receiving device 12.

<figref idref="f0004">Fig. 4</figref> shows an embodiment of the invention identical to the embodiment according to <figref idref="f0003">Fig. 3</figref>, except that a magnetic detector 21 is subcutaneously implanted in patient 13 at energy receiving device 12 and an external separate magnetic device 22 that emits a local magnetic field through patient's 13 skin 16 is provided. Magnetic device 22 may be manually moved externally along the patient 13's body to establish an energy transmission position at the patient's skin where the local magnetic field emitted by magnetic device 22 is detected by the implanted magnetic detector 21. A sender 23 is implanted in patient 13 and sends information about the status of magnetic detector 21. Thus, when magnetic detector 21 detects the local magnetic field emitted by external magnetic device 22, sender 23 sends information confirming that magnetic device 22 is in a proper position for energy transmission. When this energy transmission position has been established, energy transmission device 14 can be placed in the same position to efficiently transmit wireless energy to the implanted energy receiving device 12.

<figref idref="f0005">Fig. 5</figref> shows an example of the artificial sphincter 18 shown in <figref idref="f0003">Figs. 3</figref> and <figref idref="f0004">4</figref>. Sphincter 18 includes a hydraulically adjustable constriction device 24 to be applied around the patient's rectum (not shown in <figref idref="f0005">Fig. 5</figref>). Constriction device 24 has a cavity 25 which can be inflated by supplying hydraulic fluid thereto, to close the rectum, and be deflated by withdrawing hydraulic fluid therefrom, to open the rectum. A hydraulic operation device 26 for operating constriction device 24 is powered with energy from implanted energy receiving device 12. This type of constriction device may also be used as an artificial sphincter for treating patient's suffering from heartburn and reflux disease or urinary incontinence, when combined with the apparatus of the present invention. Furthermore, constriction device 24 may be used for forming an adjustable stoma opening in the stomach or esophagus of an obese patient to treat obesity or for restricting the penile exit blood flow to treat an impotent patient, when combined with the apparatus of the invention.

<figref idref="f0005">Fig. 6</figref> shows an advantageous design of the embodiment shown in <figref idref="f0003">Fig. 3</figref>, in which the external magnetic detector 17 includes three symmetrically arranged Hall-elements 27 which are grouped around a central point in a triangular configuration. The magnetic device 15 is implanted and includes a ring-shaped magnet 28 surrounding the centre 29 of the implanted energy receiving device 12. When magnetic detector 17 is moved to a position in which Hall-elements 27 are placed symmetrically above and around ring-shaped magnet 28, as illustrated in <figref idref="f0005">Fig. 6</figref>, magnetic detector 17 detects a maximum intensity of the magnetic field emitted by the implanted magnet 28, whereby the most accurate position where the energy transmission device 14 should be placed is established. As an alternative, the design described above may be practised in the embodiment shown in <figref idref="f0004">Fig. 4</figref>. Thus, the implanted magnetic detector 21 may include the three Hall-elements 27 and the external magnetic device 22 may include the ring-shaped magnet 28.

Although the present invention has been described in terms of a particular embodiment and process, it is not intended that the invention be limited to that embodiment. Modifications of the embodiments of the invention will be apparent to those skilled in the art. The scope of the invention is defined by the claims that follow.