IL229052A - Probe assembly for non-invasive optical monitoring - Google Patents

Description

1 229052/3 PROBE ASSEMBLY FOR NON INVASIVE OPTICAL MONITORING FIELD OF THE INVENTION This invention is generally in the field of medical devices, and relates to a probe device and a monitoring system utilizing such a probe device for carrying out measurements on a subject. The invention is particularly useful for monitoring various parameters, e.g. oxygen saturation in blood vessels, capillaries and venules, and oxygen saturation in deep tissues, such as brain, muscle, kidney and other organs.

BACKGROUND Various techniques of non invasive monitoring of conditions of a subject have been developed. These techniques include impedance-based measurement techniques, photoacoustic measurements, acoustic measurements (Doppler measurements), and optical measurements (e.g. oxymetry).

Another approach, based on use of ultrasound tagging of light in measurements of various chemical and physiological parameters, has been developed and disclosed for example in WO 06/097910 and WO 05/025399, both assigned to the assignee of the present application.

WO 06/097910 describes measurement system and method for use for non-invasive measurements in a human body. Acoustic radiation is applied to a certain illuminated region in the body, with at least two different conditions of the applied radiation achievable by varying at least one characteristic of the acoustic radiation. Light scattered from the body part is detected, and measured data indicative of detected photons tagged and untagged by the acoustic radiation is generated. The measured data is analyzed to extract therefrom a data portion corresponding to the tagged photons and being therefore associated with a light response of said certain region, thereby enabling determination of tissue properties of said certain region based on a relation between the measured data portions corresponding to the at least two different operating conditions.

US 2006/0122475 (being a continuation of WO 05/025399 above) describes method, system and probe device for use in noninvasive monitoring of at least one parameter of a region of interest in a human body. The system comprises a measurement unit (e.g. a probe device) and a control unit. The measurement unit 2 229052/3 comprises an optical unit having an illumination assembly configured to define at least one output port for illuminating light, and a light detection assembly configured to define at least one light input port for collecting light and to generate measured data indicative of the collected light; and an acoustic unit configured to generate acoustic waves of a predetermined ultrasound frequency range. The measurement unit is configured and operable to provide an operating condition such that the acoustic waves of the predetermined frequency range overlap with an illuminating region within the region of interest and substantially do not overlap with a region outside the region of interest, and that the detection assembly collects light scattered from the region of interest and light scattered from the region outside the region of interest. The measured data is thus indicative of scattered light having both ultrasound tagged and untagged light portions, thereby enabling to distinguish between light responses of the region of interest and the region outside the region of interest. The control unit is connectable to the optical unit and to the acoustic unit to operate these units, and is responsive to the measured data and preprogrammed to process and analyze the measured data to extract therefrom data indicative of a light response of the region of interest and determine the at least one desired parameter.

US Patent 7048687 describes a medical probe including a memory for maintaining a use value. The medical probe is coupled to a medical device that inhibits its function when the use value reaches a predetermined threshold value, preventing improper use of the probe. The probe memory may also store identification, usage, and clinical data. A probe auto-identification function, a probe re-identification function and a probe functional test sequence are disclosed for the medical probe. After use, a reprocessing step may reset the probe memory, permitting further probe use.

GENERAL DESCRIPTION The present invention provides a novel probe assembly and a monitoring device using the same enabling effective continuous monitoring of one or more conditions of a subject.

The present invention takes advantage of the monitoring techniques utilizing principles of ultrasound tagging of light, for example as disclosed in the above-indicated publications WO 05/025399 and WO 06/097910 assigned to the assignee of 3 229052/3 the present application. Thus, a probe assembly of the invention operates to irradiate a region of interest with acoustic waves while taking optical measurements on said region of interest.

The present invention provides for controlling condition(s) of the monitoring procedure such as to allow the monitoring procedure to start and/or to proceed in case certain condition(s) exist(s). The condition to be controlled may be the existence of a contact between the probe and the subject's tissue and/or a degree of coupling between the subject and an acoustic/light ports at the probe, and/or positioning of the probe in a docking station, etc. If the required condition is not satisfied, the monitoring procedure is not allowed, for example by canceling or disabling the laser emission at all, or disabling the laser emission in the monitoring mode.

Thus, the present invention, according to its one broad aspect, provides a probe assembly for use in monitoring one or more parameters of a subject. The probe assembly comprises an acoustic port for transmitting acoustic radiation into a region of interest in the subject, at least one light output port for transmitting incident light towards the region of interest, at least one light input port for receiving light returned from the subject, and a control utility integrated in the probe assembly. The control utility is configured for controlling at least one condition of a monitoring procedure and for enabling the monitoring procedure upon identifying that said at least one condition is satisfied.

In some embodiments of the invention, the control utility comprises at least one of the following: (i) a coding chip adapted for identifying whether the probe assembly is a certified one; and (ii) a sensor and actuator system adapted for sensing a predetermined condition of the probe assembly.

Preferably, the control utility comprises a memory unit adapted for recording data indicative of measurements taken on a specific subject during a certain period of time. In some embodiments of the invention, these data serve as a measurement history of the specific subject. The data recorded in the control utility of certain probe assembly may include data portions corresponding to measurements taken on said subject by one or more different probe assemblies.

As indicated above, the control utility may comprise a sensor and actuator system adapted for sensing one or more conditions of the probe assembly. This may 4 229052/3 be determination of a degree of attachment between the probe assembly and the subject, which in turn is indicative of a degree of coupling between the subject and acoustic and/or light ports.

In some embodiments, the probe assembly is configured as a two-part device comprising a first unit (probe body unit) and a second unit. The latter presents an interface between the probe assembly and the subject when the probe assembly is put in operation, and may be configured so that it can be removed from, or connected to the first unit. The second unit may carry at least a part of the control utility. For example, the second unit carries a memory unit adapted for recording data indicative of measurements taken on a specific subject during a certain period of time. The recorded data may be used as a measurement history of the specific subject, and may for example include data portions corresponding to the measurements taken on the same subject by at least two different probe assemblies.

The first probe body unit may comprise the acoustic port, the at least one light output port, and the at least one light input port. The second unit thus interfaces an output surface of the first unit through which acoustic and light radiations are transmitted in between the probe assembly and the subject, and may transmit acoustic and light radiation therethrough towards and from the subject.

The second unit may be configured as a flexible cover on an output surface of the first unit.

The probe assembly may comprise an ultrasound- skin coupling pad. The latter comprises one or more materials selected to provide desired acoustic coupling between the acoustic port and the subject (e.g. has acoustic impedance similar to that of tissue or skin of the subject).

In some embodiments relating to the two-part design of the probe assembly, the second unit is configured as a probe-subject adhesive assembly unit being associated with a probe-subject adhesive media, e.g. including such probe-subject adhesive media. The probe-subject adhesive media may comprise the ultrasound- skin coupling pad providing the desired acoustic coupling being substantially transparent for a wavelength range used in the probe.

The ultrasound-skin coupling pad is preferably electrically insulating. The ultrasound-skin coupling pad may have a matrix that is a polymerization product of a suspension of elastomeric resins in a plasticizer. Such ultrasound-skin coupling pad may comprise Polymelt™. 5 229052/3 In yet another aspect of the invention there is provided a monitoring system for monitoring one or more parameters of a subject. The system comprises one or more of the above-described probe assemblies. The control utility is configured and operable to carry out at least one of the following: (i) recording data indicative of measurements taken on a specific subject during a certain period of time; (ii) identifying whether the probe assembly is a certified one; and (iii) sensing at least one condition of the monitoring system and enabling operation upon identifying that said at least one condition is satisfied.

In multiple -probe embodiments of the monitoring system, the memory unit of each of the probe assemblies is preferably adapted for storing data indicative of results of measurements taken by all the probes (or at least some of them).

According to yet another aspect of the invention there is provided a probe assembly for use in monitoring one or more parameters of a subject. The probe assembly comprises: an acoustic port for transmitting acoustic radiation into a region of interest in the subject; and an ultrasound-skin coupling pad presenting an interface between the subject's surface and the acoustic port, the ultrasound-skin coupling pad comprising a matrix that is a polymerization product of a suspension of elastomeric resins in a plasticizer.

The ultrasound- skin coupling pad may be substantially transparent to light of a predetermined wavelength range and is preferably electrically insulating.

According to yet another aspect of the invention there is provided an acoustic coupling device for placing on a subject body surface to interface between the body surface and an acoustic unit, the acoustic coupling device comprising a matrix that is a polymerization product of a suspension of elastomeric resins in a plasticizer.

The acoustic coupling pad has a sticky surface to permit tight contact with a body surface substantially without air pockets.

The invention also provides a device configured as a cover for mounting on an outer surface of an acoustic probe by which the probe is brought in contact with a subject when in operation, said cover comprising a matrix that is a polymerization product of a suspension of elastomeric resins in a plasticizer.

The probe assembly can be configured as a two-part device comprising a first probe body unit and a second unit (e.g. probe-subject adhesive assembly). The second unit presents an interface between the first probe body unit and the subject when the 6 229052/3 probe assembly is put in operation. The second unit may be removed from or connected to the first probe body unit.

In some embodiments, the second unit carries at least a part of the control utility. Preferably, the second unit carries the memory unit adapted for recording data indicative of measurements taken on a specific subject during a certain period of time.

The second unit may be associated with a probe-subject adhesive media. For example, the second unit comprises such a probe-subject adhesive media.

In some embodiments of the invention, the first probe body unit comprises the acoustic port, the at least one light output port, and the at least one light input port. The second unit interfaces between the probe body and the subject on an output surface of the probe body unit through which acoustic and light radiations are transmitted.

The second unit may be configured as a flexible cover on an output surface of the first probe body unit.

In the two-part design of the probe assembly, an ultrasound- skin coupling pad if used is located in the second unit. As indicated above, the ultrasound-skin coupling pad may be substantially transparent for a wavelength range used in the probe. The ultrasound-skin coupling pad has acoustic impedance similar to that of tissue or skin of a subject. For example, the ultrasound- skin coupling pad includes a matrix that is a polymerization product of a suspension of elastomeric resins in a plasticizer. For example, the ultrasound-skin coupling pad comprises Polymelt. Preferably, the ultrasound-skin coupling pad is electrically insulating.

According to yet another aspect of the invention, there is provided a probe assembly for use in monitoring one or more parameters of a subject, the probe assembly being configured as a two-part device comprising a probe-subject adhesive assembly unit and a probe body unit, wherein: the first unit is configured as a probe body unit and comprises an acoustic port for transmitting acoustic radiation into a region of interest in the subject, at least one light output port for transmitting incident light towards the region of interest, at least one light input port for receiving light returned from the subject, the second unit presents an interface between the first unit and the subject when the probe assembly is put in operation and comprises an electronic unit having a memory utility adapted for recording data indicative of 7 229052/3 measurements taken on a specific subject during a certain period of time, enabling use of said data as a measurement history of the specific subject, the recorded data corresponding to the measurements being taken by one or more of the probe assemblies.

BRIEF DESCRIPTION OF THE DRAWINGS In order to understand the invention and to see how it may be carried out in practice, embodiments will now be described, by way of non-limiting examples only, with reference to the accompanying drawings, in which: Fig. 1 is a block diagram of an example of a probe assembly according to the invention; Fig. 2 is a block diagram of an example of a monitoring system of the present invention utilizing multiple probe assemblies of Fig. 1; Fig. 3 is an example of a logical circuit for a sensor-actuator ("interlock") system; Figs. 4A and 4B exemplify a sensor-actuator system that incorporates a microswitch sensor, where Fig. 4A shows the microswitch sensor in its closed state, and Fig. 4B shows the microswitch sensor in its normally open state; Figs. 5A and 5B exemplify a sensor-actuator system that incorporates an optical proximity sensor, where Fig. 5A shows the probe-tissue relative position such that the reflected light beam reaches the detector of the proximity sensor and Fig. 5B shows the probe-tissue relative position in which the reflected light beam does not reach the detector; Fig. 6 is an example of an ultrasound pulse and its reflection; Fig. 7 is an example of a sensor-actuator system that incorporates an ultrasound reflection proximity sensor; Fig. 8 is an example of the probe assembly of Fig. 1 being configured as a two-part device; Fig. 9A exemplifies a specific configuration of a probe body suitable to be used in the present invention; Fig. 9B exemplifies a system formed by two probe assemblies each having the probe body of Fig.9A; Fig. 9C shows an example of a two-part probe assembly; 8 229052/3 Figs. 10A and 10B show two examples of the configuration of a probe body utilizing an off-probe photodetector via a light guide (A) or an on-probe photodetection system (B); Fig. 11 exemplifies a configuration of a probe-subject adhesive assembly to be used with a probe body in the probe assembly of the present invention; Fig. 12 provides a description of an interface connector that is used to connect the probe body to the probe-subject adhesive assembly; Fig. 13 shows the position of the interface connector on the probe body; Fig. 14 shows an example of an acoustic transducer arrangement suitable to be used in the probe assembly of the present invention; DETAILED DESCRIPTION OF EMBODIMENTS Referring to Fig. 1, there is illustrated, by way of a block diagram, an example of a probe assembly, generally designated 110, which is configured and operable according to the invention for monitoring one or more parameters of a subject. The probe assembly 110 is adapted for carrying out ultrasound tagging based optical measurements. The principles of such a technique are described for example in WO 2006/097910 and WO 2005/025399, both assigned to the assignee of the present application.

Probe assembly 110 includes an acoustic port 112 for transmitting acoustic radiation into a region of interest in the subject, at least one light output port 114 for transmitting incident light towards the region of interest, and at least one light input port 116 for receiving light returned from the subject. These ports are typically located on a common housing or support structure (not shown here).

It should be understood that the acoustic port may be constituted by an acoustic transducer itself or by an acoustic guide. Similarly, the light output port may be a light source itself (light emitter) or may be connectable to an external light source via an appropriate light guide (an optical fiber or an optical fiber bundle); and the light input port may be that of an on-probe photodetection system or may be connectable to an off-probe photodetector via a light guide. There could be more than one ingoing light guide, as well as more than one outgoing light guide.

Typically, the probe assembly itself includes the light ports, while light emitter(s) (e.g. laser(s)), as well as light detector(s), are located outside the probe 9 229052/3 assembly and are connectable to the respective ports via light guides (optical fibers or optical fiber bundles). For example, a fiber, at its one end (e.g. the end which is intended for connection with the probe) is equipped with a connector (21 in Fig. 9B), e.g. a clip-bridge, for example such as disclosed in US 6,188,825. Such a connector is configured to ensure a normally-closed state of the fiber end of the probe (i.e. state in which no light transmission is allowed through the end of the fiber). The state of this connector changes into an open state (i.e. light transmission is allowed) only upon connection to the respective light port at the controller. A corresponding adapter at the controller side is also normally closed, to prevent dust collection, and opens upon connection to the above-described optical connector at the probe side (i.e. both sides are normally closed, and become open only upon connection to one another).

As further illustrated in a specific but non-limiting example of Fig. 1, the probe assembly 110 communicates with a controller 140, which typically includes a computer system. The communication between the probe assembly and the controller may be via wires or by means of wireless signal/data transmission (e.g. RF, IR, acoustic). The controller 140 may include among other things a light source system and/or a detection system and/or an acoustic generator (e.g. arbitrary waveform generator).

Preferably, a light guide connecting an external light emitter (e.g. in the controller) and a light output port at the probe is a small core fiber (e.g. a single-mode, a 50 pm or a 62.5 pm core fiber). As for a light guide connecting an external light detector (e.g. in the controller) and a corresponding light input port at the probe, it has an appropriate cross-sectional dimension of the core in order to satisfy the collection efficiency requirement. For example, a fiber or a fiber bundle, having a core of a diameter equal to or higher than 100 pm can be used. The maximal diameter and numerical aperture of a collecting fiber is determined so that the total path difference between light traveling in different paths in the fiber core is less than the coherence length of the light source.

According to the invention, the probe device 110 also includes an integral control utility 120. Generally, the control utility allows for identifying whether the probe assembly is a certified one; and/or is capable of sensing a predetermined condition of the probe assembly (e.g. including a degree of coupling between the subject and the acoustic/light ports); and/or is configured to actuate/operate the 10 229052/3 measurement of the monitoring unit 150 and/or laser emission; and/or is adapted for recording data indicative of measurements taken on a specific subject during a certain period of time (thus enabling use of this data as a measurement history of the specific subject).

Thus, as shown in Fig. 1, according to some embodiments of the invention, the control utility includes a memory unit 122 (shown in dashed lines in Fig. 1) adapted for recording data indicative of measurements taken on a specific subject during a certain period of time. Such data may serve as a measurement history of a specific subject. Alternatively or additionally, the control utility contains a coding chip 123 for the purpose of controlling the use of a "certified" probe, by using a unique activation code, so that when a probe is attached to the controller 140 only a certified probe could be used. Alternatively or additionally, the control utility 120 includes a sensor 124A (also shown in dashed lines) adapted for sensing one or more predetermined probe condition(s) at which the probe and controller 140 are allowed to operate, and an actuator 124B adapted for enabling/disabling measurement of the monitoring system 150, and/or operation of the controller 140, and/or laser emission, and/or acoustic emission according to sensor identification of these predetermined condition(s).

It should be noted that for performing measurements involving ultrasound tagging of light, a sufficient degree of acoustic coupling between the acoustic port 112 and the subject should be obtained. According to some embodiments of the present invention, the outer surface 125 of the probe assembly 110 by which it is brought into contact with the subject to be monitored, provides the desired acoustic coupling by means of an ultrasound-skin-coupling pad 126. The ultrasound-skin coupling pad could be separate from the transducer or the probe assembly, or it could be an integral part of one or both of these.

In reference to Fig. 2, a monitoring system 150 is exemplified, including a controller 140 and one or more probe assemblies 110. As illustrated in the specific non-limiting example of Fig. 2, the monitoring system includes two probe assemblies 110 and 110' for placing on different locations LI and L2 on the subject and associated with the same or different regions of interest in the subject. The probe assemblies 110 and 110' are configured as described above with reference to Fig. 1, including their own control utilities 120 and 120'. In the present example, the control utilities include memory units 122 and 122', respectively. It should be understood, 11 229052/3 although not specifically shown, that the control utility may include the sensor and actuator as well (124A and 124B in Fig. 1). The system configuration is such that each of measurement data pieces MD1 and MD1’ corresponding to measurements taken by probe assemblies 110 and 110', or a measurement taken by other probes hooked to the same controller 140, is stored in both memory units 122 and 122'. In addition, the measurement data of a measurement taken by a probe assembly can be transferred to any other probe assembly hooked to any other controller, by connecting them to the same controller, or by connecting all the controllers to another common one. In other words, each of said control utilities is adapted for storing data indicative of results of measurements taken by all or some of the probe assemblies. All the probe assemblies are connectable to the common controller 140, which is configured to determine and synchronize the measurement data and results among all the probe devices. The probe(s) and the controller are configured for appropriate data exchange between them.

The controller 140 may be adapted to control and operate with various data synchronization scenarios. For example, a user may input data indicative of that a “New patient” is to be monitored, in which case the "measurement history" data is deleted from a memory of the controller 140 (the so-called “empty” status). When a user chooses “Continue procedure” mode, the controller 140 operates to transfer/copy most or all of the recently updated stored data from its memory into the memory units (122, 122' in Fig. 2) of all the probes that are connected to it. Similarly, history data may be transferred to the memory of the controller 140 to update the data previously stored therein. In addition, the updated data may be refreshed from time to time between the two (or more) probes. When one of the probe assemblies with a memory unit therein or a part of one of the probe assemblies that includes the memory unit, are replaced by a new one, while the other probe assemblies remain unchanged and retain their memory units, the history data from the memory units of the remaining probe assemblies is transferred to the new memory unit. In an additional example of a data synchronization scenario, the controller is configured to identify a used memory unit. If a new patient is declared, while the memory unit was not changed, the measurement will be disabled until the replacement of the memory unit.

In cases where the operation of the controller or the probe assembly should be controlled automatically, without active involvement of the operator, for example in cases where the monitoring system utilizes laser emission, safety measures should 12 229052/3 preferably be taken in order to protect the subject in case of an accidental detachment of the probe assembly from the inspected tissue. The sensor 124A and actuator 124B (shown in Fig. 1) are configured to sense predetermined condition(s) of the system, and to enable/disable measurement of the monitoring system 150, and/or operation of the controller 140, and/or laser emission, and/or acoustic emission.

In one embodiment of the invention, such a condition could be the existence of a contact between the probe assembly and the subject's tissue. It could be defined either as a Boolean YES/NO condition, or as a threshold distance between the probe assembly and the subject's skin, as predetermined by the system. Thus, the sensor 124A and actuator 124B may be configured and operable for generating data indicating the distance of the probe to the subject's skin as compared to a predetermined threshold value. In another embodiment of the invention, such a condition could be the positioning of the probe in a docking station. The actuator system typically controls or communicates with the operation system of the acoustic transducer (at the controller) and/or the light source system to thereby selectively permit (enable or disable) the probe operation depending on whether the predetermined condition(s) is/are satisfied. In a specific although non-limiting example, the sensor 124A and actuator 124B serve to cancel or disable any laser emission if risk of unnecessary exposure to the laser radiation is present. According to the example, there are two possible situations for each probe assembly in which laser operation is allowed: (a) probe is attached to the patient; (b) probe is in the docking position. The actuator will not allow any other probe situation, in which case it will stop laser emission.

In Fig. 3 an example for a logical circuit of such a sensor-actuator ("interlock") system is provided. This specific example is for the case of a monitoring system with two probes. As shown, the probes are equipped with interlock sensing devices 31 and 32 (can be replaced by 124A, 124B and 124A', 124B' of Fig. 1) and docking switches 33 and 34 respectively. In this non-limiting example, the interlock sensors 31, 32 are constituted by a proximity detector. Docking switches 33 and 34 are coupled through a gate 35 to an inverter 36. As an example, a condition is described when one probe assembly (the right one in the figure) is correctly attached to the patient’s skin, the proximity detector 31 output is logical "0", and the other probe assembly (the left one in the figure) is in the docking station, the appropriate switch 34 is activated and provides a logical "0" to gate 35. Only when both inputs of 13 229052/3 gate 35 are logical "0", the output will be logical "0". The output of gate 35 is the input of inverter 36 so that an output of logical "0" at gate 35 results in logical "1" as the output of inverter 36.

A flip-flop set, formed by gates 37 and 38, controls laser emission. Optionally, an additional switch 39 can be used. When switch 39 is activated while the output of inverter 36 is logical "0", the output of gate 38 becomes logical "1", and the output of gate 37 becomes logical "0". This activates a relay 40, thus providing a voltage supply to the lasers.

If for any reason one of the probes becomes detached (generally, its position does not satisfy a predetermined degree of attachment condition, or is released from the docking station during laser operation), gate 35 becomes logical "1", gate 36 becomes logical "0" bringing about logical " 1 " as the output of gate 37, which in turn releases the relay 40 terminating laser emission. In case of laser emission termination, in order to resume laser operation, switch 39 should be reactivated.

The monitoring system 150 may utilize any one of (but is not limited to) the following sensor 124A and actuator 124B systems to provide such safety measures.

The sensor system may be adapted for direct microswitch sensing, an example of which is given in Figs. 4A and 4B. A microswitch is located on the probe assembly. The microswitch contacts 12A are normally open (state NO = logic 1), as in Fig. 4B. When the probe assembly is attached to a subject's body, the microswitch is depressed and is thus closed (logical 0), as in Fig. 4A, indicating normal operation. Once the probe assembly is detached from the subject 55, the switch will open the circuit (logical "1") and laser emission and/or operation of the monitoring system will stop, as described above. Examples for micro-switches suited for this embodiment are mechanical micro-switches, with a lever of a few millimeters (see Figs. 4A and 4B). As a non-limiting example, a microswitch such as ESE-2131BT of Panasonic, Japan, can be used.

Alternatively or additionally, the sensor system (124A in Fig. 1, or 31, 32 in Fig. 3) may include an optical proximity sensor, an example of which is shown in Figs. 5A and 5B. In this case a light beam 240 should be directed to the plane of attachment between the probe assembly and the subject body 55, in such a manner that only when proper attachment is achieved the light reflection 241 could be detected in the probe assembly, for example at detector 242 in Fig. 5A, and should be above/below a certain threshold. When the probe is detached the detected signal drops 14 229052/3 below the threshold (logical "1") and the actuator will disable the operation of the monitoring system and the probe assembly, as in Fig 5B.

In one embodiment, the reflection of the monitoring system’s own laser(s) is detected. In this case, the monitoring system is preferably configured for differentiating between the lasers' and ambient light, by locking the detected light to the modulation between the different lasers, and filtering low-frequency (i.e. ambient) light.

In another embodiment of an optical proximity sensor, an optically coupled IR LED and a detector are utilized. In order to ensure that ambient light does not disturb the operation of this sensor, the LED is modulated and the received signal is correlated with this modulation. In the example shown in Figs. 5A and Fig. 5B, a modulator 243 modulates the transmitted signal from light source 246, while the received signal is transferred from the demodulator 244 to a correlator 245 where it is correlated with the transmitted signal from the modulator 243.

Yet another possible implementation is to use a capacitance proximity sensor adapted for sensing the distance between the probe assembly and the patient’s skin by tracking changes in capacitance between the two surfaces. A change in the distance between the two surfaces results in a change in the electric field that brings upon a change in capacitance. There are many methods utilizing this physical phenomenon to measure distance, such as a capacitance bridge, variations in frequency of an oscillator and other devices designed for capacitive proximity detection such as QT113 by Quantum Technology, AD 7151 by Analog devices or the like. A capacitance chip, equipped with an electronic circuit capable of determining the capacitance level associated with the probe assembly position relative to the subject's body or a docking site, can be used. Thus, when the capacitance measured exceeds a predetermined capacitance threshold, the output of the circuit is logical "0" (i.e. probe is attached), and when the measured capacitance is below that threshold, the output is logical "1". A more complicated circuitry that detects gradients in capacitance can be utilized, enabling detection of detachment condition demonstrated by a positive gradient in the detected capacitance (logical "1"), relative to steady state (logical "0").

Yet another option is to use ultrasound reflectance detection in the sensor-actuator system. Since the system already includes an acoustic transmitter, the same transmitter can be used, with an acoustic receiver, to detect an ultrasound pulse reflected from the patient’s body. 15 229052/3 Referring to Fig. 6, an ultrasound pulse 41 is sent from a transducer toward the subject's body, resulting in a reflection 42 of this pulse from the interface with a known feature in the body (such as bone). The reflected pulse 42 is detected in the probe assembly. The time difference between the onset of the sent pulse 41 and the reflected pulse 42 (time delay t ) is used to calculate the distance between the probe assembly and the subject's body. A safety threshold for the time delay should be predetermined by the monitoring system, and the operation of the probe assembly and the monitoring system should be controlled accordingly (logical "0" is defined when t is above a predetermined threshold). When the probe assembly is detached from the body and an air gap is established therebetween, the signal is reflected from the edge of the transducer and time delay t is reduced to almost zero, so that the sensor mechanism will thus shut down the operation (logical "1") of the probe/lasers.

A non-limiting example for a circuit of such a sensor-actuator system is provided in Fig. 7. An acoustic transducer 53 is connected to tissue 55 via an ultrasound-skin coupling pad 126. If the ultrasound- skin coupling pad (as part of the probe assembly) is detached from the subject's tissue, a reflection burst (42 in Fig. 6) will appear at a very short time delay (almost zero) relative to the onset of the pulse. A circuit 56 is the gating mechanism to separate between the transmitted signal and the received one. In order to reduce the chance of a false alarm, the received, reflected, pulse is amplified and delayed in an amplifier 58 and then correlated in an appropriate correlation utility 59 with the transmitted signal 57. The output of the correlation utility 59 is compared with the threshold level, Vth, at a comparator 60, providing an output of logical "0" or logical "1" as the interlock signal.

It should be noted that the probe assembly could be a multi-part unit, e.g. two-part unit, where the components described above could be distributed in between those parts (as will be shown in a specific non-limiting example).

Turning back to Fig. 1, the outer surface 125 of the probe assembly 110 by which it is brought into contact with the subject to be monitored is associated with an acoustic coupling media that provides the desired acoustic coupling between the acoustic port 112 and the subject's skin or tissue, or may include such media as a constructional part thereof. As shown in the figure, the outer surface 125 of the probe assembly includes an ultrasound-skin-coupling pad 126. It is necessary to ensure that the acoustic transducer outer surface/port is in complete contact with the skin, and that no air pockets exist. Due to skin-air impedance mismatch, air pockets reflect acoustic 16 229052/3 waves and reduce the coupling efficacy of the acoustic waves into the tissue dramatically.

Generally, the probe assembly of the present invention may be used with any suitable ultrasound transmission/coupling material, known in the art (for example gel, hydrogel or a dry coupling pad). However, the gels that are currently in use suffer from a number of drawbacks. For example, most gels are aqueous, therefore over time water evaporates and the gel dries, so that recurrent gel spreading is required. In addition, such gels suffer from their conductive nature, which is undesired in applications where electric insulation between the skin and the apparatus is required. Therefore, there is a need in the art for a dry ultrasound coupling pad. The present invention solves this problem by providing a novel ultrasound-skin coupling pad which is made of a transparent rubber-like elastomer material, which is appropriate for use in any application requiring coupling between any transducer assembly, or any acoustic port, and a subject's tissue or skin.

As a non-limiting example the ultrasound-skin coupling pad could be made of Polymelt which is a suspension of elastomeric resins in a plasticizer. Any other elastomer, with acoustic impedance similar to that of tissue or skin, can be used. The ultrasound-skin coupling pad can be molded in any shape and size.

The ultrasound- skin coupling pad can be used in any application in which coupling is required between a transducer assembly and a subject's skin or tissue. The acoustic properties of the ultrasound- skin coupling pad do not vary with time, so that it is optimal in applications where ultrasound is to be applied for extensive time periods. The pad is electrically insulating, therefore it can be used in applications where electrical insulation is required between the ultrasound transducer and a subject's skin. The ultrasound- skin coupling pad should be able to bear an electric field of approximately lOOOV/mm for it to be insulating.

The ultrasound-skin coupling pad can be used for coupling between any acoustic transducer assembly and any object. Since it can be molded to any shape and size it can fill in air gaps surrounding any measured object that one requires to be coupled to a transducer assembly (provided the object can withstand the temperature of the fluid suspension that is used to create the ultrasound- skin coupling pad). In this manner, the ultrasound-skin coupling pad becomes a buffer for the measured object, and allows the coupling of ultrasound to rough surfaces as well. An example for such an application is NDT (Non Destructive Tests). Such an acoustic coupling pad may be 17 229052/3 configured as or be a part of a cover mountable onto an outer surface of an acoustic probe (or a probe having acoustic port(s)).

In some embodiments, the acoustic coupling material is substantially transparent for an electromagnetic wavelength range used for illumination by the probe. For example, in applications where ultrasound waves and light are emitted from an overlapping output port, the ultrasound-skin coupling pad medium should be transparent to electromagnetic waves within the emitted wavelength range, to enable the transmittance of light through it. An acoustic coupling pad may include one or more materials possessing transparency/or opacity to the electromagnetic wavelength range in use.

The ultrasound-skin coupling pad can be biocompatible, and provide direct coupling to the skin, or be covered with a biocompatible film that forms the direct interface with the skin/tissue. As an example, a biocompatible double sided adhesive may be applied on the outer surface of the attachment unit to facilitate better contact of the probe and the subject's tissue.

The following are some specific non-limiting examples of a probe assembly, of probe parts, and of probe part configurations.

Reference is made to Fig. 8 showing a specific but non-limiting example of the configuration of the probe device of Fig. 1. The probe assembly 110 is configured as a two-part device comprising a probe body unit 130 and a probe-subject adhesive assembly unit 132 configured for interfacing between the probe assembly and the subject when the probe assembly is operating. The probe-subject adhesive assembly 132 is associated with a probe-subject adhesive media, e.g., comprises such a probe-subject adhesive media. The probe-subject adhesive assembly unit 132 may be configured so that it can be removed from, or connected to the probe body unit.

The probe body unit 130 includes at least the following components: the acoustic port 112, the light output port(s) 114, and the light input port(s) 116. The probe-subject adhesive assembly unit 132 interfaces an output surface of the probe body unit 131 through which acoustic and light radiations are transmitted in between the probe and the subject. Thus, when in operation, the probe assembly is brought into contact with the subject by the probe-subject adhesive assembly unit 132. A probe-subject adhesive assembly unit 132 is preferably constituted by an element configured to serve as a cover on the output surface 131 of the probe body unit 130 through which acoustic and light radiations are transmitted in between the probe body unit and 18 229052/3 the subject. The probe body contains an interface connector 119 that is connected to an interface connector on the probe-subject adhesive assembly unit 119A. The outer surface 125 of the probe-subject adhesive assembly unit includes an ultrasound- skin coupling pad 126 in the form of one of a selection of materials selected to provide the desired acoustic coupling between the acoustic port 112 and a subject. The probe-subject adhesive assembly unit 132 may include a coding chip 123. The probe-subject adhesive assembly unit 132 may comprise both flexible and rigid support materials.

Either one or all of the electronic unit 122, the coding chip 123, the sensor 124A, and the actuator 124B may be accommodated in the probe body unit or in the probe-subject adhesive assembly unit. With regard to the sensor 124A and actuator 124B system, it should be understood that its elements may be appropriately distributed between the probe body unit and the probe-subject adhesive assembly unit. In one embodiment, the probe-subject adhesive assembly unit 132 may be a disposable part of the probe device. In such an embodiment, the electronic memory unit 122 is preferably carried by the disposable probe-subject adhesive assembly unit 132, since it is aimed at recording and storing a subject's monitoring history.

It should be understood that in the case of a disposable (removable) probe subject-adhesive assembly unit 132, it may be used for multiple measurement sessions in which it is attached to the same or to different probe body units, as long is it is not removed from the subject's skin. When the adhesive assembly unit is attached to a probe body unit, the subject monitoring history data, stored in said disposable unit, is synchronized with the controller 140 connected to the respective probe body unit. However a disposable subject-adhesive assembly unit can serve as a memory utility holding the subject's monitoring history data even when the disposable unit cannot or is no longer used for further measurement sessions (e.g. in some embodiments, after the disposable subject-adhesive assembly unit had been detached from a subject skin it is not used in further measurements). Reference is made to Figs. 9A-9C. In this embodiment, the probe assembly is configured as a two-part device comprising a probe body unit 130 and a probe-subject adhesive assembly unit 132 (shown in Figs. 9B and 9C). The probe body 130 illustrated in Fig.9A includes an acoustic transducer 112, two light output ports 114 (associated with light emitters), and a light input port 116 associated with a light detection unit. It should be noted that the provision of the second light output port is optional. Also provided in the probe body unit 130 is an interface connector 119 (an optional part of the sensor 124A actuator 124B system) 19 229052/3 configured to electronically connect the probe subject-adhesive assembly to the probe body unit and to carry out data/signal transmission between the probe body unit and the electronic memory unit (not shown here) in the probe-subject adhesive assembly unit (through the interface connector 119A of Fig. 8). A common housing 118 accommodates the elements of the probe body unit.

Fig. 9B illustrates a monitoring system which includes two probe assemblies each having the above-described probe body unit 130 and a probe-subject adhesive assembly unit 132 mounted on the probe body. Each probe is connected to an optical fiber bundle composed of two optical fibers for carrying electromagnetic radiation from the light source 4, and to the detector 4A. Each probe is connected to the controller 140 via an electrical cable 5 adapted for data/signal transmission and via an optical connector 21 and an electrical connector 22. The light source and the detection unit may be located in the controller 140.

Fig. 9C is a perspective side view of the above-described probe assembly with the probe-subject adhesive assembly 132 mounted onto the probe body 130. The probe is connected via a connector 3 including a strain relief, to an optical fiber bundle comprising two separate fibers 4 and 4A, which connect the probe assembly to the light source and to the detector (not shown here), respectively and also via an electric cable 5.

Figs. 10A and 10B illustrate the internal architecture of the probe body unit 130 according to two embodiments. Each of the probe body units comprises an acoustic transducer 112 and an interface connector 119 for data/signal transmission to and from the electronic memory unit (e.g. in the probe-subject adhesive assembly unit) and to the interlock sensor/actuator when positioned on the probe-subject adhesive assembly unit. The probe body unit includes an electronic board 6 upon which the acoustic transducer, optical elements and the interface connector are assembled. Electronic board 6 includes an electronic circuit (e.g. PCB) connected to the acoustic transducer and to the electronic unit (e.g. in the probe-subject adhesive assembly unit) via the interface connector 119. Electronic board 6 is connected to the controller 140 (not shown) via an electric cable 5. Optionally, board 6 may be connected to the controller 140 via a wireless connection. The light output port 114 could be on the side of the acoustic port 112, as shown in Fig. 9A. Optionally, light output port 114 could be through the acoustic port 112 and may include an optical prism 10, an optical rod 9 and an optical window 8 for directing propagation of light

Claims (5)

22 229052/3 CLAIMS:

1. A probe assembly for use in monitoring one or more parameters of a subject, the probe assembly comprising acoustic and light ports for carrying out ultrasound tagging based optical measurements, and a control utility comprising a safety system, wherein: said safety system comprises a sensor and an actuator, the sensor being configured for sensing at least one predetermined safety condition of the probe assembly and for producing a signal indicative of whether said at least one predetermined safety condition is satisfied, the actuator being configured to enable or disable actuation of a monitoring procedure in response to the signal produced by the sensor, such that the actuator starts the monitoring procedure upon identifying by the sensor that the at least one predetermined safety condition is satisfied and stops the monitoring procedure upon identifying by the sensor that the at least one predetermined safety condition is not satisfied.

2. The probe assembly of Claim 1, wherein the safety system is adapted for sensing said at least one predetermined safety condition comprising a degree of attachment between the probe assembly and the subject, being indicative of a degree of coupling between the subject and at least one of the acoustic and light ports.

3. The probe assembly of Claim 1 or 2, wherein the control utility comprises a memory unit for recording data indicative of measurements taken by one or more probe assemblies on a specific subject during a certain period of time, presenting a measurement history of the specific subject.

4. The probe assembly of any one of the preceding Claims, being configured as a two-part device comprising a first probe body unit, and a second unit which presents an interface between the probe assembly and the subject when the probe assembly is put in operation.

5. The probe assembly of Claim 4, wherein the second unit is removably attachable to the first probe body unit.