WO2011161592A2

WO2011161592A2 - System with interventional ultrasound monitoring device

Info

Publication number: WO2011161592A2
Application number: PCT/IB2011/052627
Authority: WO
Inventors: Jan Frederik Suijver
Original assignee: Koninklijke Philips Electronics N.V.
Priority date: 2010-06-22
Filing date: 2011-06-16
Publication date: 2011-12-29
Also published as: WO2011161592A3

Abstract

The present invention relates to a system (200) comprising an interventional device (228) with a plurality of ultrasound transducers (212a-c). The system (200) furthermore comprises one or more delay units (218, 220) arranged so that ultrasonic signals converted into electrical signals by the ultrasound transducers (212a-c) may be temporally separated so that the resulting difference in temporal delay between two received electrical signals at a point of combination correspond to a time span being larger than a characteristic temporal length of an excitation signal. The electrical signals may be combined into a single temporally extended signal so that a single receiver (222) may be able to receive the signals as a single temporally extended signal. Analysis of the single temporally extended signal may allow separation of signals originating from respective ultrasound transducers. In a particular embodiment, the system further comprises an ablation unit.

Description

System with interventional ultrasound monitoring device

FIELD OF THE INVENTION

The present invention relates to the field of systems with interventional devices, in particular, the present invention relates to a system with interventional devices with ultrasound transducers, such as catheters with ultrasound transducers, and a

corresponding method applicable for monitoring in medical applications.

BACKGROUND OF THE INVENTION

Ultrasound transducers can be utilized to obtain information of an associated object, such as a heart of a patient. A setup for ultrasound measurements may utilize a sending ultrasound transducer, an excitation source for generating an electrical signal and an electrical connection for connecting the excitation source to the ultrasound transducer. For receiving an ultrasound signal reflected from the associated object, and therewith information regarding the associated object, a receiving ultrasound transducer which may or may not be the same ultrasound transducer as the sending ultrasonic transducer is used. The receiving ultrasound transducer is electrically connected to a receiver. The information from such a setup of one or more ultrasound transducers may be dependent on the direction of emitted ultrasonic signal, thus for obtaining spatially resolved information, such setup may not be very effective. Different approaches may be taken in order to obtain spatially resolved information in an efficient manner. One approach may be to move the ultrasound transducer spatially and repeat measurements with the ultrasound transducer in a new position. This may infer delicate and complicated operations associated with risks and discomfort for the patient being examined, and furthermore such approach may be time consuming.

Hence, an improved system for ultrasound monitoring an associated object would be advantageous, and in particular a more efficient, simple, fast and/or reliable system for ultrasound monitoring an associated object would be advantageous.

SUMMARY OF THE INVENTION

In particular, it may be seen as an object of the present invention to provide a system for ultrasound monitoring an associated object that solves the above mentioned problems of the prior art concerning how to simplify the system and the operation of the system, while keeping the system relatively cheap and efficient.

It is a further object of the present invention to provide an alternative to the prior art.

Thus, the above described object and several other objects are intended to be obtained in a first aspect of the invention by providing a system for ultrasound monitoring an associated object comprising:

a control unit, the control unit comprising:

an excitation source being capable of sending a primary electrical signal to a plurality of ultrasound transducers, and

a receiver being capable of receiving a tertiary electrical signal, an interventional device, the interventional device comprising: the plurality of ultrasound transducers, the plurality of ultrasound transducers being positioned in a distal end of the interventional device and being capable of emitting primary ultrasonic signals to an associated object, which primary ultrasonic signals are based on the primary electrical signal, and receiving secondary ultrasonic signals from the associated object and converting the secondary ultrasonic signals into secondary electrical signals, and

a primary electrical connection electrically connecting the plurality of ultrasound transducers with a proximal end of the interventional device,

a point of combination where the plurality of secondary electrical signals from the plurality of ultrasound transducers are combined into a tertiary electrical signal, and

a secondary electrical connection serving to electrically connect the control unit to the primary electrical connection, wherein the secondary electrical connection comprises a delay unit serving to temporally delay an electrical signal going forth and back through the secondary electrical connection a time span tl, where tl is a time span larger than a characteristic temporal length of the primary electrical signal.

The invention is particularly, but not exclusively, advantageous for obtaining spatially resolved ultrasound monitoring in a simple, cheap and efficient manner. By implementing delay units and a point of combination as suggested, a single excitation source and a single receiver can be used to respectively send a primary electrical signal and receive a tertiary electrical signal, which tertiary electrical signal may be resolved so as to obtain separate information from each of the ultrasound transducers in the plurality of ultrasound transducers. The point of combination may simply be an electrical connection electrically connecting a plurality of electrical conductors.

In a particular embodiment the receiver may comprise an amplifier.

The primary electrical signal, the primary electrical signals, the secondary electrical signals and the tertiary electrical signal, may be analogue signals, such as voltage signals.

In another particular embodiment according to the invention the system may further comprise a switch. An advantage of having a switch may be that the switch may act to direct the primary electrical signal, such as an excitation pulse, towards the plurality of ultrasound transducers, and the secondary electrical signals or the tertiary electrical signal towards the receiver. This may be advantageous in that it may then be possible to avoid that a high-voltage excitation pulse goes to both the plurality of ultrasound transducers as well as the receiver. At the receiver, such high voltages may either damage or destroy the electronics, or it may lead to momentary 'blindness' of the electronics, thereby missing the much smaller (in the 0.1 - 100 mV range) tertiary electrical signal received back from the plurality of ultrasound transducers. The switch may be placed in the control unit or outside of the control unit.

It is understood that the interventional device might be a unit wherein the plurality of ultrasound transducers is integrated. The interventional device might comprise a catheter, a needle, a biopsy needle, guidewire, sheath, or an endoscope.

The primary and secondary ultrasonic signals might be pulsed-echo signals. The pulsed-echo technique is defined as sending a short ultrasound pulse by a low-Q transducer into a medium, and receiving the reflections back at the transducer from

irregularities in a medium (due to change of acoustical impedance), such as the surface of the associated object which is considered an irregularity in the present context. The transit time from sending the primary ultrasonic signal, which may be in the form of an initial pulse to reception of the echo, i.e., receipt of the secondary ultrasonic signal, is proportional to the depth at which the irregularities are found.

The delay units may have fixed temporal delays. In an alternative embodiment, the delay units may have temporal delays which are variable. Implementations of delay units may include simply using a distance of cable, retarded wave propagation, and/or an off-the-shelf device, such as a Bucket-Brigade device.

In another embodiment according to the invention, the system further comprises an ablation unit being capable of ablating the associated object. By implementing an ablation unit, the system may be applicable for an ablation process. During an ablation process, it may be important to be able to monitor various parameters.

As used herein, the term "ablation" refers to any kind of suitable ablation within the teaching and general principle of the present invention. Thus, it could be radio frequency (RF) based (incl. microwave), optically based (e.g., an optical emitter, such as a laser, such as a laser emitting wavelengths in the infrared, visible or ultraviolet range), a heating element, such as a hot water balloon, a cooling element (cryogenic ablation), or ultrasound-based ablation such as high intensity focused ultrasound (HIFU).

In the context of the present application, the term "ablation unit" refers to an optical emitter, such as a laser in case of optical-based ablation, an electrode (or other suitable RF emitting devices) in case of RF- and microwave-based ablation, a low-temperature thermal contact in the case of cryo ablation, and to an ultrasound transducer, such as a high intensity focused ultrasound (HIFU) transducer, in case of ultrasound based ablation.

By characteristic temporal length of the primary electrical signal is understood a temporal length representative of an order of magnitude of the temporal length of the primary electrical signal. For example, if a square pulse is used, the characteristic temporal length may correspond to the full width of the square pulse. In another example a bell-shaped function, such as a Gaussian function, may be used and the characteristic temporal length may be the full width at half maximum of the bell shaped function.

In another embodiment according to the invention, the ablation unit is comprised within the interventional device. An advantage of this may be that both the ablation unit and the plurality of ultrasound transducers are assembled into a single device.

In another embodiment according to the invention, tl is a time span comparable to a total time span of the primary ultrasonic signal going from the plurality of ultrasound transducers to the associated object summed with a time span of the secondary ultrasonic signal going from the associated object to the plurality of ultrasound transducers. This ensures that the secondary electrical signals at a point of combination are temporally separated by a time span comparable to the time it takes an ultrasonic signal a round trip from the ultrasound transducer to associated object and back. In a more particular embodiment, tl is a time span larger than a total time span of the primary ultrasonic signal going from the plurality of ultrasound transducers to the associated object summed with a time span of the secondary ultrasonic signal going from the associated object to the plurality of ultrasound transducers. In another embodiment according to the invention, the primary electrical connection comprises a separate electrical connection for each ultrasound transducer in the plurality of ultrasound transducers, wherein each separate electrical connection is traversing a distance from the distal end of the interventional device to the proximal end of the interventional device. This makes it possible to have all signal processing occurring outside the catheter.

In another embodiment according to the invention, the interventional device comprises a number n of ultrasound transducers, n being larger than 2, and the secondary electrical connection comprises a plurality of delay units, wherein the temporal delay of different delay units of an electrical signal going forth and back through the secondary electrical connection corresponds to different time spans, and wherein the difference in time spans between two delay units corresponds to a time span being larger than the characteristic temporal length of the primary signal. An advantage of having a plurality of delay units is that more than two ultrasound transducers can be used while still being able to temporally delay secondary electrical signals of all transducers so that the tertiary electrical signal may be resolved so as to obtain separate information from each of the ultrasound transducers in the plurality of ultrasound transducers. An advantage of coupling the delay units in parallel may be that it is then possible to arrange the delay units so that each delay unit is directly responsible for the temporal delay of only one ultrasound transducer. Another advantage may be that a relatively few number of wire interconnects is needed.

In another embodiment according to the invention the interventional device comprises a number n of ultrasound transducers, n being larger than 2, and the secondary electrical connection comprises a plurality of delay units, wherein two delay units in the plurality of delay units are coupled serially, and wherein an ultrasound transducer in the plurality of ultrasound transducers is electrically connected to a point between the two serially connected delay units. An advantage of having a plurality of delay units is that more than two ultrasound transducers can be used while still being able to temporally delay secondary electrical signals of all transducers so that the tertiary electrical signal may be resolved so as to obtain separate information from each of the ultrasound transducers in the plurality of ultrasound transducers. An advantage of coupling the delay units serially may be that it is then possible to arrange the delay units so that one or more delay units are used for a plurality of ultrasound transducers, thus diminishing the need for the total amount of delay unit. In another embodiment according to the invention wherein the control unit further comprises a digitizer for converting the tertiary electrical signal into a tertiary digital signal, and a processor arranged for receiving the tertiary digital signal, and sending a quaternary signal indicative of an associated object related parameter, the quaternary signal being based upon the tertiary digital signal. A possible advantage of having the tertiary electrical signal digitized is that it is then susceptible to digital processing. A processor may then be able to process the tertiary digital signal and extract information otherwise inaccessible.

In another embodiment according to the invention wherein the quaternary signal is any one of: local thickness of associated object, quality and/or quantity of contact between interventional device and associated object, progression of an ablation process across associated object, depth of an ablation lesion front. By having the quaternary signal represent any one of the given parameters, valuable information may be extracted from the tertiary digital signal. Information which may subsequently be arranged for utilization, such as incorporated in a feedback loop.

In another embodiment according to the invention the system is adapted to transmit a high frequency electrical signal from the plurality of ultrasound transducers to the receiver. Especially high frequency components have been shown valuable for extracting information related to one or more of the parameters: local thickness of associated object, quality and/or quantity of contact between interventional device and associated object, progression of an ablation process across associated object, depth of an ablation lesion front. Hence, the capability of transmitting high frequency electrical signals from the plurality of ultrasound transducers may be advantageous in order to extract the information underlying those parameters.

In another embodiment according to the invention the frequency of the high frequency electrical signal is larger than 10 MHz. In another embodiment the high frequency electrical signals are in the range of 10 - 60 MHz. In yet another embodiment, the electrical signals are in the range of 20 - 45 MHz.

In another embodiment according to the invention the plurality of ultrasound transducers is spatially arranged so that there will be a non-zero angle between a direction of a first and a second primary ultrasonic signal in the plurality of primary ultrasonic signals emitted from the plurality of ultrasound transducers. An advantage of this may be that it increases the probability that at least one ultrasound transducer in the interventional device is oriented so that a direction of the primary ultrasonic signal emitted from the interventional device is orthogonal to a surface of the associated object. One possible way to implement this is to angle an ultrasound transducer in the plurality of ultrasound transducers with respect to one other ultrasound transducer in the plurality of ultrasound transducers.

In a further embodiment according to the invention, a direction of a third ultrasonic signal in the plurality of primary ultrasonic signals emitted from the plurality of ultrasound transducers has a non-zero angle with respect to a plane spanned by the directions of the first and the second primary ultrasonic signals.

An advantage of this may be that it increases the probability that at least one ultrasound transducer in the interventional device is oriented so that a direction of the primary ultrasonic signal emitted from it is orthogonal to a surface of the associated object. One possible way to implement this is to angle a third ultrasound transducer in the plurality of ultrasound transducers with respect to the plane spanned by the directions of the first and the second primary ultrasonic signals emitted by first and second ultrasound transducers.

According to a second aspect of the invention, there is presented a method for operating a system for monitoring an associated object using a system according to any of the preceding claims, the method comprising the steps of:

generating a primary electrical signal,

sending the primary electrical signal to a secondary electrical connection, splitting the primary electrical signal into a plurality of primary electrical signals,

sending the plurality of primary electrical signals to the plurality of ultrasound transducers, the plurality of ultrasound transducers being positioned in a distal end of an interventional device and being capable of emitting primary ultrasonic signals to an associated object and receiving secondary ultrasonic signals from an associated object

sending a plurality of secondary electrical signals from the plurality of ultrasound transducers,

delaying a primary electrical signal in the plurality of primary signals and/or delaying a secondary electrical signal in the plurality of secondary electrical signals, wherein the resulting difference in temporal delay between two secondary electrical signals at a point of combination corresponds to a time span tl being larger than a characteristic temporal length of the primary electrical signal,

combining the plurality secondary electrical signals into a tertiary electrical signal at the point of combination, and

receiving the tertiary electrical signal at a receiver. The steps of the method need not necessarily be carried out in the order in which they are listed.

In another embodiment, the method for operating a system further includes the steps of converting the tertiary electrical signal into a tertiary digital signal, such as digitizing the tertiary electrical signal, and generating a quaternary signal indicative of an associated object related parameter, the quaternary signal being based upon the tertiary digital signal.

The first and second aspect of the present invention may each be combined with any of the other aspects. These and other aspects of the invention will be apparent from and elucidated with reference to the embodiments described hereinafter.

BRIEF DESCRIPTION OF THE FIGURES

The system according to the invention will now be described in more detail with regard to the accompanying figures. The figures show exemplary ways of implementing the present invention and is not to be construed as being limiting to other possible embodiments falling within the scope of the attached claim set.

Fig. 1 shows an example of a measurement using an ultrasound transducer for monitoring an associated object,

Fig. 2 shows an embodiment of the invention with delay lines connected in parallel,

Fig. 3 shows an example of a measurement using a plurality of ultrasound transducers for monitoring an associated object,

Figs. 4-5 show alternative embodiment of the invention with delay lines connected in parallel,

Fig. 6 shows an embodiment of the invention with delay lines connected in serial,

Fig. 7 shows an embodiment of the invention with delay lines connected in parallel and a plurality of switches,

Fig. 8 shows a distal end of an interventional device according to an embodiment of the invention,

Fig. 9 shows a system for monitoring an associated object according to the prior art,

Fig. 10 is a flow-chart of a method according to the invention, Fig. 11 shows an embodiment including a contact. DETAILED DESCRIPTION OF EMBODIMENTS

Figure 1 shows an example of a measurement using an ultrasound transducer for monitoring an associated object. In the present example, the monitored object is a heart. The graph has time along the primary axis with the units being microseconds (μβ) and intensity along the secondary axis being arbitrary units (a. u.). Such measurement can be obtained with a setup as depicted in Figure 9. In the measurement shown in Figure 1, one sees the following main features: The response 132 of the transducer on excitation (so-called 'ring-down'), the front wall of the cardiac tissue 134, and the back wall 136 of the cardiac tissue. Clearly, extending further in time (i.e., depth) beyond the back wall, a lot of 'useless' signal is recorded.

Figure 2 shows an embodiment of the invention with delay lines 218-220 connected in parallel. In the figure is shown an excitation source 208, capable of sending a primary electrical signal, the primary electrical signal being an excitation signal, such as a voltage pulse, capable of enabling an ultrasound transducer to emit an ultrasonic signal. The figure also shows an electrical connection 201 connecting the excitation source 208 to a switch 210. Furthermore is shown electrical connections 202a-c, 203a-c in a secondary electrical connection 227 electrically connecting the switch 210 to a primary electrical connection 205a-c, 206a-c in an interventional device 228. The secondary electrical connection 227 also comprises delay lines 218, 220. The interventional device 228 comprises the plurality of ultrasound transducers 212a-c in a distal end and the primary electrical connection 205 a-c, 206a-c which electrically connects the plurality of ultrasound transducers 212a-c with a proximal end 213 of the interventional device. The primary electrical connection 205 a-c, 206a-c may comprise a separate electrical connection for each ultrasound transducer in the plurality of ultrasound transducers, wherein each separate electrical connection is traversing a distance from the distal end of the interventional device to the proximal end of the interventional device. The electrical connection 202a-203a may be a single conducting path, or it may be a plurality of conducting paths such as two electrically conducting wires. Similarly the electrical connection 202b-203b and the electrical connection 202c-203c may each be a single conducting path or it may be a plurality of conducting paths. Similarly, the electrical connections 205a-c, 206a-c may each be a single conducting path, or it may each comprise a plurality of conducting paths. The switch 210 is connected via electrical connection 204 to a receiver 222. The receiver 222 is connected via connection 207 to a computer 224. The switch 210 acts to direct the primary electrical signal towards the plurality of ultrasound transducers 212a-c and the tertiary electrical signal towards the receiver 222. Furthermore, in the embodiment shown, the switch 210 also comprises the point of combination, where the secondary electrical signals from the plurality of ultrasound transducers are combined into a tertiary electrical signal. The switch may ensure that a high- voltage (>100 V) primary electrical signal, such as an excitation pulse, does not go to both transducers as well as receiver. At the receiver, which may comprise an amplifier, such high voltages will either damage or destroy the electronics, or it will lead to momentary

'blindness' of the electronics, thereby missing the much smaller (in the 0.1 - 100 mV range) tertiary electrical signal received back from the ultrasound transducers.

An exemplary use of the system is now outlined. The excitation source 208, such as a single pulser, is used to generate the primary electrical signal for the plurality of ultrasound transducers. In the present example, the primary electrical signal is a pulse. This pulse is fed into the switch 210. The output of the switch is now sent simultaneously to the secondary electrical connection, thus sending the output of the switch to first ultrasound transducer 212a as well as to the two ultrasound transducers 212b-c via the two delay lines 218,220. At each of the ultrasound transducers 212a-c the primary electrical signal is converted into a primary ultrasonic signal which is emitted from the respective ultrasound transducer. The respective primary ultrasonic signals may be reflected back to the ultrasound transducers by an associated object, such as a heart, in the form of respective secondary ultrasonic signals. The ultrasound transducers convert the secondary ultrasonic signals into respective secondary electrical signals, which are sent via the primary electrical connection 205 a-c, 206a-c to the secondary electrical connection 227 thus sending the secondary electrical signal associated with the ultrasound transducer 212a to the switch 210 and the respective secondary electrical signals from ultrasound transducers 212b-c via the two delay lines 218,220 to the switch 210. The secondary electrical signals from the three transducers 212a-c thus pass back to the switch 210 and further to the receiver 222 where they are amplified and digitized.

In consequence, the receipt of the respective secondary electrical signals from ultrasound transducers 212b-c at the switch 210 is delayed temporally with respect to receipt of the secondary electrical signal from ultrasound transducer 212a at the switch 210 by a time span corresponding to twice the time it takes an electrical signal to pass delay units 218,220 respectively, since the delay units 218,220 are passed both when the primary electrical signal is sent to the ultrasound transducers 212b-c, and when the corresponding secondary electrical signals go back to the switch 210. In order to determine an exemplary magnitude of the temporal delay of the delay units 218,220, a calculation is outlined.

A high-end digitizer card is able to record at a maximum of 200 MS/s (at 16 bit accuracy) with a total record length of 8192 samples. The speed of ultrasound in human tissue is known to be 1500 m/s. The required depth in the heart one wishes to monitor during progression of an ablation process is 5 - 10 mm. Given that the ultrasound has to do a round- trip through the tissue (send and receive is done with the same transducer), one needs to double this distance to 10 - 20 mm. At the highest sampling rate, the above implies that one needs to record a total of

(20 mm x 200 MS/s) / 1500 m/s = 2667 samples,

in a time of

A typical example of such a measurement is given in Figure 1. Therefore, the length of the delay lines in an embodiment as shown in Figure 2 could be:

Delay unit 218:

½ x 20 mm / 1500 m/s = 6.5 (which corresponds to 1334 samples), and

Delay unit 220:

1 x 20 mm / 1500 m/s = 13.3 (which corresponds to 2667 samples).

In the manner such as proposed above, one can record the signals of three different ultrasound transducers. Note that there will be a very small (6.5 - 13.5

microsecond) time difference between the three readouts. However, as this is orders of magnitude smaller than the typical time constants associated with cardio-pulmonary motion artifacts (millisecond range), the signals can be assumed to have been recorded at the same - instantaneous - moment. The skilled person will realize that the applicable number of ultrasound transducer for a given number of samples may depend on the sample rate, such as enabling a doubling of the number of temporally resolvable ultrasound transducers for a halving of the sample rate.

Figure 3 shows an example of what one may measure with an embodiment of the system as given in Figure 2. For clarity, the signals of the three transducers have been color coded differently (black, dark grey, light grey). Analogously to the measurement in Figure 1 , the measurement in Figure 3 shows an example of a measurement using a plurality ultrasound transducers for monitoring an associated object. In the present example, the monitored object is a heart. The graph has time along the primary axis with the units being microseconds (μβ) and intensity along the secondary axis being arbitrary units (a. u.). In the measurement shown in Figure 3, one sees the following main features: The response 332a-c of each of the ultrasound transducers 212a-c on excitation (so-called 'ring-down'), the front wall of the cardiac tissue 334a-c, and the back wall 336a-c of the cardiac tissue. Clearly, the response from each ultrasound transducer is temporally well resolved here, since the delay units 218,220 ensures that receipt of the respective secondary signals at the point of combination, such as within the switch 210, differs by time spans tl and t2. As the skilled person realizes, a computer 224 can be used to straightforwardly extract the different signals, as the exact temporal delay between each of the signals is known and given by twice the respective temporal delay of each delay unit. In an exemplary implementation, time band filters may be added to the computer. Such time band filter could then, for example, output to different analysis systems, or simply to different computer algorithms or programs within the same computer.

Figures 4-5 show alternative embodiment of the invention with delay lines connected in parallel. In Figures 4-5 the delay units 418,420 are also coupled in parallel. In Figure 4, the secondary electrical connection 427 comprises electrical connection 402b, 403b which in the present embodiment comprises two separate electrical conductors arranged so that the primary electrical signal does not go through a delay unit when travelling from the switch 210 to the ultrasound transducer 212b, but the secondary electrical signal passes delay unit 418 when going from the ultrasound transducer 212b to the switch 210. Similarly, for the electrical connection 402c, 403c where delay unit 420 is passed only by the secondary electrical signal and not by the primary electrical signal. The skilled person realizes that the magnitude of the temporal delay of the delay units 418, 420, may be different from the temporal delay of the delay units 218, 220, such as for example the double of the temporal delay of the delay units 218,220 in the embodiment depicted in Figure 2. Figure 5 shows a similar embodiment where the delay units 518, 520 are only passed by the primary electrical signal going from switch 210 to ultrasound transducers 212b-c, respectively, since in Figure 5, the secondary electrical connection 527 comprises electrical connection 502b, 503b which in the present embodiment comprises two separate electrical conductors arranged so that the primary electrical signal does go through a delay unit 518 when travelling from the switch 210 to the ultrasound transducer 212b, but the secondary electrical signal does not pass delay unit 518 when going from the ultrasound transducer 212b to the switch 210. Similarly for the electrical connection 502c, 503c where delay unit 520 is passed only by the primary electrical signal and not by the secondary electrical signal. Figure 6 shows an embodiment of the invention with a system 600 with a secondary electrical connection 627 with delay lines 618, 620 connected in serial. In this embodiment a primary signal going from switch 210 to ultrasound transducer 212a does not pass a delay unit, and a secondary electrical signal going from ultrasound transducer 212a to switch 210 does not pass a delay unit. Analogously to the embodiment described in Figure 2, both a primary electrical signal going from switch 210 to ultrasound transducer 212b and a secondary electrical signal going from ultrasound transducer 212b to switch 210 passes delay unit 618. In the embodiment of Figure 6, the delay units 618 and 620 are coupled serially. Ultrasound transducer 212b is electrically connected to a point between delay unit 618 and 620. A primary electrical signal going from switch 210 to ultrasound transducer 212c and a secondary electrical signal going from ultrasound transducer 212c to switch 210 passes delay unit 618 and delay unit 620. Thus the time span between receipts of secondary signals from ultrasound transducers 212a-c at the switch 210 is given by twice the temporal delay of delay unit 618 and delay unit 620, respectively.

Figure 7 shows yet another embodiment of the invention with a system 700 with delay units 718, 720 connected in parallel and a plurality of switches 710a-c which are used to guide primary electrical signals to the plurality of ultrasound transducers 212a-c and the secondary electrical signals to a point of combination 738. The electrical connections 202a-c are connected at their point of crossing as indicated by the filled circle. However, note that if there is no filled circle at a point of crossing between two electrical connections, the electrical connections which are crossing are not electrically connected at the point of crossing. This is, for example, the case for the electrical connection going from switch 710a to point of combination 738 which crosses the electrical connection going from delay unit 718 to switch 710b. Those two electrical connections are not electrically interconnected at the crossing. This applies also to the crossings shown between delay unit 720 and switch 710c.

Figure 8 shows a distal end 840 of an interventional device according to an embodiment of the invention, where the distal end 840 comprises three ultrasound transducers 812a-c. The figure shows the ultrasound transducers 812a-c arranged so that primary ultrasonic signals emitted from the ultrasound transducers are non-parallel. In the shown embodiment, the ultrasound transducers 812a-c are arranged so that primary ultrasonic signals emitted from the ultrasound transducers substantially lie within a single plane.

However, in other embodiment, the distal end of the interventional device comprises ultrasound transducers arranged to emit primary ultrasonic signals which do not all lie in a single plane. Figure 9 shows a system for monitoring an associated object according to the prior art, with components as described with reference to Figure 2, and a single ultrasound transducer 912.

Figure 10 is a flow-chart of a method according to the invention for operating a system for monitoring an associated object using a system according to any of the preceding claims, the method comprising the steps of generating a primary signal (SI 042) , sending the primary signal to a secondary electrical connection (SI 044), splitting the primary signal into a plurality of primary signals (SI 046), sending the plurality of primary signals to the plurality of ultrasound transducers (SI 048) where the plurality of ultrasound transducers are positioned in a distal end of an interventional device and being capable of emitting primary ultrasonic signals to an associated object and receiving secondary ultrasonic signals from an associated object, sending a plurality of secondary signals from the plurality of ultrasound transducers (SI 050), delaying a primary signal in the plurality of primary signals and/or delaying a secondary signal in the plurality of secondary signals (SI 052), wherein the resulting difference in temporal delay between two secondary signals at a point of combination corresponds to a time span tl being larger than a characteristic temporal length of the primary signal, combining the plurality secondary signals into a tertiary electrical signal at the point of combination (SI 054), receiving the tertiary electrical signal at a receiver (SI 056) and converting the tertiary electrical signal into a tertiary digital signal (SI 058). In the depicted embodiment, the method further includes the step of generating a quaternary signal (SI 060), the quaternary signal being indicative of an associated object related parameter, the quaternary signal being based upon the tertiary digital signal. The quaternary signal may be any one of a visible signal, such as an image, a number, an audible signal or a feed-back signal to be used in a process which is monitored.

Figure 11 shows an embodiment including a contact 1140. The excitation source 208 is connected to a point of combination 1138, which is connected to electrical paths 1102a-c in a secondary electrical connection. The contact 1140 is connected via to a receiver 222. The receiver 222 is connected via connection 207 to a computer 224. The contact 1140 may ensure that a high- voltage (>100 V) primary electrical signal, such as an excitation pulse does not go to the receiver.

To sum up, the present invention relates a system (200) comprising an interventional device (228) with a plurality of ultrasound transducers (212a-c). The system (200) furthermore comprises one or more delay units (218, 220) arranged so that ultrasonic signals converted into electrical signals by the ultrasound transducers (212a-c) may be temporally separated so that the resulting difference in temporal delay between two received electrical signals at a point of combination correspond to a time span being larger than a characteristic temporal length of an excitation signal. The electrical signals may be combined into a single temporally extended signal so that a single receiver (222) may be able to receive the signals as a single temporally extended signal. Analysis of the single temporally extended signal may allow separation of signals originating from respective ultrasound transducers. In a particular embodiment, the system further comprises an ablation unit.

Although the present invention has been described in connection with the specified embodiments, it should not be construed as being in any way limited to the presented examples. The scope of the present invention is set out by the accompanying claim set. In the context of the claims, the terms "comprising" or "comprises" do not exclude other possible elements or steps. Also, the mentioning of references such as "a" or "an" etc. should not be construed as excluding a plurality. The use of reference signs in the claims with respect to elements indicated in the figures shall also not be construed as limiting the scope of the invention. Furthermore, individual features mentioned in different claims, may possibly be advantageously combined, and the mentioning of these features in different claims does not exclude that a combination of features is not possible and advantageous.

Claims

CLAIMS:

1. A system (200) for ultrasound monitoring an associated object comprising:

a control unit (226), the control unit comprising:

an excitation source (208) being capable of sending a primary electrical signal to a plurality of ultrasound transducers (212a-c), and

a receiver (222) being capable of receiving a tertiary electrical signal, an interventional device (228), the interventional device comprising:

the plurality of ultrasound transducers (212a-c), the plurality of ultrasound transducers being positioned in a distal end of the interventional device and being capable of emitting primary ultrasonic signals to an associated object, which primary ultrasonic signals are based on the primary electrical signal, and receiving secondary ultrasonic signals from the associated object and converting the secondary ultrasonic signals into secondary electrical signals, and

a primary electrical connection (205 a-c, 206a-c) electrically connecting the plurality of ultrasound transducers with a proximal end (213) of the interventional device (228),

a secondary electrical connection (227) serving to electrically connect the control unit (226) to the primary electrical connection (205 a-c, 206a-c), wherein the secondary electrical connection comprises a delay unit (218, 220) serving to temporally delay an electrical signal going forth and back through the secondary electrical connection a time span tl, where tl is a time span larger than a characteristic temporal length of the primary electrical signal.

2. A system (200) according to claim 1, wherein the system (200) further comprises an ablation unit being capable of ablating the associated object.

3. A system (200) according to claim 2, wherein the ablation unit is comprised within the interventional device (228).

4. A system (200) according to claim 1, wherein tl is a time span comparable to a time span of the primary ultrasonic signal going from the plurality of ultrasound transducers (212a-c) to the associated object and the secondary ultrasonic signal going from the associated object to the plurality of ultrasound transducers (212a-c).

5. A system (200) according to claim 1, wherein the primary electrical connection (205 a-c, 206a-c) comprises a separate electrical connection for each ultrasound transducer in the plurality of ultrasound transducers, wherein each separate electrical connection is traversing a distance from the distal end of the interventional device to the proximal end (213) of the interventional device.

6. A system (200) according to claim 1, wherein

the interventional device (228) comprises a number n of ultrasound

transducers, n being larger than 2, and

the secondary electrical connection (227) comprises a plurality of delay units (218, 220), wherein the temporal delay of different delay units of an electrical signal going forth and back through the secondary electrical connection corresponds to different time spans, and wherein the difference in time spans between two delay units corresponds to a time span being larger than the characteristic temporal length of the primary signal.

7. A system (600) according to claim 1, wherein

the interventional device (228) comprises a number n of ultrasound

transducers, n being larger than 2, and

the secondary electrical connection (627) comprises a plurality of delay units

(618, 620), wherein two delay units in the plurality of delay units are coupled serially, and wherein an ultrasound transducer (212b) in the plurality of ultrasound transducers (212a-c) is electrically connected to a point between the two serially connected delay units (618, 620).

8. A system (200) according to claim 1, wherein the control unit (226) further comprises a digitizer for converting the tertiary electrical signal into a tertiary electrical signal, and a processor arranged for receiving the tertiary digital signal, and sending a quaternary signal indicative of an associated object related parameter, the quaternary signal being based upon the tertiary digital signal.

9. A system according to claim 8, wherein the quaternary signal is any one of: local thickness of associated object, quality and/or quantity of contact between interventional device and associated object, progression of an ablation process across the associated object, depth of an ablation lesion front.

10. A system (200) according to any claim 1, wherein the system is adapted to transmit a high frequency electrical signal from the plurality of ultrasound transducers (212a- c) to the receiver (222).

11. A system according to claim 10, where the frequency of the high frequency electrical signal is larger than 10 MHz.

12. A system according to claim 1, wherein the plurality of ultrasound transducers (212a-c) is spatially arranged so that there will be a non-zero angle between a direction of a first and a second primary ultrasonic signal in the plurality of primary ultrasonic signals emitted from the plurality of ultrasound transducers (212a-c).

13. A system according to claim 12, wherein a direction of a third ultrasonic signal in the plurality of primary ultrasonic signals emitted from the plurality of ultrasound transducers (212a-c) has a non-zero angle with respect to a plane spanned by the directions of the first and the second primary ultrasonic signals.

14. A method for operating a system for monitoring an associated object using a system (200) according to any of the preceding claims, the method comprising the steps of:

generating a primary electrical signal (SI 042),

sending the primary signal to a secondary electrical connection (SI 044), splitting the primary electrical signal into a plurality of primary electrical signals (SI 046),

sending the plurality of primary electrical signals to the plurality of ultrasound transducers, the plurality of ultrasound transducers being positioned in a distal end of an interventional device and being capable of emitting primary ultrasonic signals to an associated object and receiving secondary ultrasonic signals from an associated object (S1048), sending a plurality of secondary electrical signals from the plurality of ultrasound transducers (SI 050),

delaying a primary electrical signal in the plurality of primary electrical signals and/or delaying a secondary electrical signal in the plurality of secondary electrical signals, wherein the resulting difference in temporal delay between two secondary electrical signals at a point of combination corresponds to a time span tl being larger than a characteristic temporal length of the primary electrical signal (SI 052),

combining the plurality secondary electrical signals into a tertiary electrical signal at the point of combination (SI 054), and

receiving the tertiary electrical signal at a receiver (SI 056).

15. A method for operating a system according to claim 14, wherein the method further includes the steps of

converting the tertiary electrical signal into a tertiary digital signal (SI 058), and

generating a quaternary signal indicative of an associated object related parameter (SI 060), the quaternary signal being based upon the tertiary digital signal.