FIELD OF THE INVENTION

The present invention relates to an ultrasound system for performing an ultrasound measurement on a surface of a body, in particular skin of a subject, and a method of operating such ultrasound system, as well as a computer program for implementing such method.

The present invention further relates to a system for performing an action on a skin of a subject and a method of operating such system, as well as a computer program for implementing such method. BACKGROUND OF THE INVENTION

In order to derive a sufficient image quality of an ultrasound image, typically a contact agent is required between an ultrasound probe and skin of the subject (e.g. test person). The usual procedure is to manually place a contact agent in form of a contact gel onto the skin and/or the ultrasound probe or transducer. The amount of contact gel to be used usually needs to be estimated and requires prior knowledge by the user of the system. This leads to several disadvantages. The first disadvantage is that the amount of contact agent or gel needs to be estimated and therefore, in order to ensure a good image quality, more contact agent or gel than probably needed has to be applied to the skin. This leads to unnecessary waste and possible discomfort of the subject (e.g. test person). A second disadvantage is that the contact agent or gel needs to be manually applied and therefore an extra step in the whole imaging process or ultrasound procedure is needed. For a system used in a consumer application, this would lead to a lower ease of use and probably non-acceptance of the system. Furthermore, after finishing the ultrasound measurement, the user of the system needs to manually remove and clean the contact agent or gel from the skin. Another disadvantage is that the contact agent or gel is perceived by the subject (e.g. test person) as being inconvenient and uncomfortable. Another disadvantage is that there are usually air bubbles in the ultrasound contact agent or gel, which cause noise in the ultrasound signal. Furthermore, for certain during the ultrasound measurement, the user of the system has to ensure that the ultrasound measurement is performed with a constant (or monitored) pressure to ensure that all tissues are equally compressed during the whole ultrasound measurement and that repeated ultrasound measurements produce reproducible results.

US 2011/0190635 Al discloses an ultrasound scanner comprising a gel distributing device which is attached, or built into, at least one signal emitting probe. The ultrasound scanner is provided with a gel holder for gel used to transmit ultrasound waves for medical, paramedical and/or veterinary procedure purposes. The holder is fixed to the probe and has an opening in the vicinity of the signal emitting or receiving window of the probe. The holder is a tight, sterile, supple pouch, which is tightly connected by tubes or the equivalent to a pump which, in turn, is tightly connected to at least one probe. The invention also relates to the use of the fluid circuit of the ultrasound scanner, comprising at least the tight, sterile, supple pouch that is tightly connected via the tube to the pump set which, in turn, is tightly connected via the tube for supplying the signal emitting and/or receiving window of the probe with gel, in order to automatically prevent the operator from having to manually supply the gel and to stop the gel remaining for subsequent procedures from coming into contact with the air, the patient, or any other sources of contamination.

However, such ultrasound scanner is not very well adapted for consumer applications.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide an improved and/or automated ultrasound system and method of operating the same, in particular adapted for consumer applications, as well as a computer program for implementing such method.

It is a further object of the present invention to provide an improved and/or automated system for performing an action on a skin of a person and method of operating the same, in particular adapted for consumer applications, as well as a computer program for implementing such method.

In a first aspect of the present invention an ultrasound system for performing an ultrasound measurement on a surface of a body is presented, the system comprising: a reservoir containing contact agent, an ultrasound probe comprising at least one transducer element for transmitting and/or receiving ultrasound waves in an ultrasound measurement area, at least one opening for releasing the contact agent from the ultrasound probe into the ultrasound measurement area, a contact agent delivery unit for delivering a specific amount of the contact agent through the at least one opening, and a control unit for receiving sensor information on the ultrasound measurement and for generating a control signal based on the sensor information, the control unit automatically controlling the contact agent delivery unit based on the control signal.

In a further aspect of the present invention method of operating an ultrasound system for performing an ultrasound measurement on the surface of a body is presented, the system comprising a reservoir containing contact agent, an ultrasound probe comprising at least one transducer element for transmitting and/or receiving ultrasound waves in an ultrasound measurement area, at least one opening for releasing the contact agent into the ultrasound measurement area, and a contact agent delivery unit for delivering a specific amount of the contact agent through the at least one opening, the method comprising:

receiving sensor information on the ultrasound measurement, generating a control signal based on the sensor information, and automatically controlling the contact agent delivery unit based on the control signal.

In a further aspect of the present invention a computer program comprising program code means for causing a computer to carry out the steps of the method according to the invention when said computer program is carried out on the computer.

The basic idea of the invention is to provide a system with an intelligent (or automatic) dispense or release mechanism for a contact agent, in particular a contact gel, into the measurement area (on the surface of the body). A contact agent is in general any agent (e.g. fluid or gel) provided between the system and the skin, in particular for improving the coupling between the ultrasound system and the skin in the case of an ultrasound contact agent. The delivery of a specific amount or dose (in particular per unit time) of contact agent through the at least one opening is based on sensor information. In particular, the control is working automatically (e.g. continuously or repeatedly), such that a feedback loop can be provided.

In a further aspect of the present invention a system for performing an action on skin of a subject, the system comprising: a reservoir containing contact agent, an action performing element for performing an action on the skin in an action area, at least one opening for releasing the contact agent into the action area, a contact agent delivery unit for delivering a specific amount of the contact agent through the at least one opening, and a control unit for receiving sensor information on the performed action and for generating a control signal based on the sensor information, the control unit automatically controlling the contact agent delivery unit based on the control signal.

In a further aspect of the present invention a method of operating a system for performing an action on skin of a subject is presented, the system comprising a reservoir containing contact agent, an action performing element for performing an action on the skin in an action area, at least one opening for releasing the contact agent into the action area, a contact agent delivery unit for delivering a specific amount of the contact agent through the at least one opening, the method comprising receiving sensor information on the performed action, generating a control signal based on the sensor information, and automatically controlling the contact agent delivery unit based on the control signal.

In a further aspect of the present invention a computer program is presented comprising program code means for causing a computer to carry out the steps of the method according to the invention when said computer program is carried out on the computer.

Preferred embodiments of the invention are defined in the dependent claims. It shall be understood that the claimed method or computer program has similar and/or identical preferred embodiments as the claimed ultrasound system and as defined in the dependent claims. Further it shall be understood that the claimed system for performing an action on skin, the claimed method of operating such system, or the computer program has similar and/or identical preferred embodiments as the claimed ultrasound system and as defined in the dependent claims.

In a first embodiment, the sensor information is based on an ultrasound signal obtained from the ultrasound waves received by the at least one transducer element. In this way the ultrasound probe or transducer element(s) itself act as a sensor for providing the sensor information in the ultrasound measurement. This reduces costs as no further sensors are needed.

In a variant of this embodiment, the sensor information is information on a quality of the ultrasound signal or of an ultrasound image derived from the ultrasound signal. In this way an indirect measurement of the amount of contact agent is performed, as the ultrasound signal or image quality correlates with the amount of contact agent used. The system can in particular comprise a processing unit for deriving the ultrasound image from the ultrasound signal. In particular, the quality of the ultrasound signal or ultrasound image can comprise a certain signal-to-noise ratio of the ultrasound signal or image.

In a variant of this variant, the control unit configured to automatically control the contact agent delivery unit based on the control signal such that the specific amount of contact agent is a minimally required amount in order to obtain a minimally required quality of the ultrasound signal or image. In this way it is ensured that the amount of contact agent is sufficient to perform the ultrasound measurement. Thus, the reliability, convenience and/or ease of use of the ultrasound measurement is improved. In a further variant of this embodiment, the sensor information is information on an ability of an algorithm processing the ultrasound signal to interpret an ultrasound image derived from the ultrasound signal. In this variant the algorithm can for example be an algorithm or method for determining actual tissue layer boundaries of the body. In this way the contact agent delivery unit can be controlled to deliver contact agent until the algorithm is able to interpret the ultrasound image (e.g. to detect the required tissue layer boundaries). This ability to interpret the ultrasound image (e.g. to determine actual tissue layer

boundaries) usually requires a sufficient signal-to-noise ratio of the ultrasound signal or image.

In a second embodiment, the sensor information is obtained from at least one additional non-ultrasound sensor of the ultrasound system. In this way any kind of information on the ultrasound measurement can be obtained.

In a variant of this embodiment, the additional non-ultrasound sensor is a pressure sensor for sensing a pressure applied by the ultrasound probe on the surface. In this way a steady pressure during the whole ultrasound measurement (e.g. scanning process) can be ensured. In this way the assumption that the lower the pressure, the more contact agent is required, can be taken into account for the automatic release mechanism. In particular, a plurality of pressure sensors can be provided.

In a further variant of this embodiment, the additional non-ultrasound sensor is a sensor selected from the group comprising a distance sensor for sensing a distance travelled by the ultrasound probe on the surface, a time sensor for sensing a time which the ultrasound probe travelled on the surface, or a speed sensor for sensing a speed of the ultrasound probe. In this way the assumption that the longer the distance travelled, the longer the travel time, or the faster the movement, the more contact agent is required, can be taken into account for the automatic release mechanism.

In a further variant of this embodiment, the additional non-ultrasound sensor is a movement sensor for sensing a movement of the ultrasound probe. In this way the assumption that the longer the distance travelled, the longer the travel time and/or the faster the movement, the more contact agent is required, can be taken into account for the automatic release mechanism. The movement sensor can in particular be a laser-based movement sensor. Alternatively, the movement sensor can be an optical and/or mechanical movement sensor.

In a further variant of this embodiment, the additional non-ultrasound sensor is a camera for sensing a movement trajectory or a location of the ultrasound probe on the surface. In this way the assumption that the longer the distance travelled, the longer the travel time and/or the faster the movement, the more contact agent is required, can be taken into account for the automatic release mechanism. By sensing the movement trajectory, it can be achieved that always the same trajectory is travelled (or rescanned) on the surface. This improves reproducibility of the measurement.

In a further variant of this embodiment, the additional non-ultrasound sensor is a dryness sensor for sensing a dryness of the surface of the body. In this way the assumption that the dryer the skin, the more contact agent is required, can be taken into account for the automatic release mechanism.

In a further variant of this embodiment, the sensor information is obtained from a plurality of non-ultrasound sensors which are any combination of sensors mentioned in the variants above.

In a further embodiment, the first embodiment, or one of its variants, and the second embodiment, or one of its variants, is combined.

In a further embodiment, the ultrasound probe comprises a single transducer element. In this way a cheap ultrasound system can be provided, in particular for consumer applications.

In an alternative embodiment, the ultrasound probe comprises multiple transducer elements. In this way the ultrasound measurement, in particular ultrasound image, can be improved.

In a further embodiment, the at least one opening is arranged in the ultrasound probe and/or the system comprises a plurality of openings. In particular, the plurality of openings can at least partly (or completely) surround the transducer element(s) or

measurement area.

In a further embodiment, the system comprises a manual release means for releasing the contact agent, wherein the manual release means can be manually activated. In this way, additionally to the automatically control, also a manual dispense or release mechanism of the contact agent is provided. The manual release means can for example be activated by the user of the system if he or she is not satisfied with the amount of contact agent delivered by the automatic dispense or release mechanism.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter. In the following drawings: Fig. 1 shows a schematic diagram of a system according to a first embodiment, Fig. 2 shows a schematic diagram of a system according to a second embodiment,

Fig. 3 shows a perspective view of an ultrasound system according to an embodiment,

Fig. 4 shows a perspective view of part of the ultrasound system according to the embodiment of Fig. 3,

Fig. 5 shows a perspective view of an ultrasound probe of an ultrasound system according to an embodiment applied to skin of a subject,

Fig. 6 shows a schematic diagram of an ultrasound probe of an ultrasound system according to an embodiment, the ultrasound probe being positioned on the surface of a body having two tissue layers,

Fig. 6a shows a schematic block diagram of a part of an ultrasound system for performing an algorithm or method for determining actual tissue layer boundaries,

Fig. 6b shows a flowchart of the corresponding method to the system of Fig.

6a, and

Fig. 7 shows a screen shot of an ultrasound image displayed on a display of an ultrasound system.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a schematic diagram of a system according to a first embodiment, and Fig. 2 shows a schematic diagram of a system according to a second embodiment. In each of Fig. 1 and Fig. 2 an ultrasound system for performing an ultrasound measurement on a surface 2 of a body 1, in particular skin of a subject, is shown. The body 1 can be understood to be the body of a subject, or any body part of the subject (e.g. an arm, leg, belly, or the like). The system comprises an ultrasound probe 10 comprising at least one transducer element 24 (forming a transducer) for transmitting and/or receiving ultrasound waves in an ultrasound measurement area A. The ultrasound probe 10 can comprises a single transducer element 24, in particular in a consumer application. However, it will be understood that the ultrasound probe 10 can also comprises multiple transducer elements 24, as is generally the case in a conventional medical application.

The system further comprises a reservoir 9 containing contact agent (e.g. gel), and at least one opening 11 for releasing the contact agent into the ultrasound measurement area A on the surface 2, thus onto the surface 2. In Fig. 1 and Fig. 2 a bulk 3 of contact agent on the surface 2, released from the at least one opening 11, is shown. In Fig. 1 and Fig. 2 the opening 11 is arranged in the ultrasound probe 10. However, the opening 11 can also be arranged in a separate device close to the ultrasound probe 10 and measurement area A. The system further comprises a contact agent delivery unit 13 for delivering a specific amount of the contact agent (in particular per unit time) through the at least one opening 11. The contact agent delivery unit 13 can for example be a pump, valve, or any other suitable means for enabling a flow of the contact agent. The amount of contact agent can for example be defined by a specific flow rate. The contact agent is delivered from the contact agent reservoir 9 to the contact agent delivery unit 13 through a tube 9a or the like. The contact agent is delivered from the contact agent delivery unit 13 to the at least one opening 11 through a tube 13a or the like.

The system further comprises a control unit 15 for receiving sensor information 15a on the ultrasound measurement and for generating a control signal 15b based on the sensor information 15a, the control unit 15 automatically controlling the contact agent delivery unit 13 based on the control signal 15b. In this way an intelligent (or automatic) dispense or release mechanism for the contact agent is provided. The delivery or release of contact agent is automatically controlled based on sensor information 15a. In particular, the control is automatically (e.g. continuously or repeatedly) such that a feedback loop can be provided.

A corresponding method of operating such ultrasound system comprises the steps of receiving sensor information 15a on the ultrasound measurement, generating a control signal 15b based on the sensor information 15a, and automatically controlling the contact agent delivery unit 13 based on the control signal 15b.

In the first embodiment of Fig. 1 the system further comprise a processing unit 34 for processing an ultrasound signal 34a, and in particular for deriving an ultrasound image 36 from the ultrasound signal 34a. The ultrasound signal 34a is obtained from the ultrasound waves received by the at least one transducer element 24. In the first embodiment of Fig. 1, the sensor information 15a is based on the ultrasound signal 34a. In this way the ultrasound probe 10 or transducer element(s) 24 itself act as a sensor for providing the sensor information in the ultrasound measurement. In one example, the sensor information 15a can be information on a quality of the ultrasound signal 34a or of an ultrasound image 36 derived from the ultrasound signal 34a. In particular, the control unit 15 can be configured to automatically control the contact agent delivery unit 13 based on the control signal 15b such that the specific amount of contact agent is a minimally required amount in order to obtain a minimally required quality of the ultrasound signal or image 34a, 36. In another example, the sensor information 15a can be information on an ability of an algorithm processing the ultrasound signal 34a to interpret an ultrasound image 36 derived from the ultrasound signal 34a. The algorithm can for example be an algorithm or method for determining actual tissue layer boundaries of the body, as will be further explained with reference to Fig. 6, Fig. 6a, Fig. 6b and Fig. 7.

In the second embodiment of Fig. 2 the ultrasound system comprises at least one additional non-ultrasound sensor 40. The sensor information 15a is obtained from this at least one additional non-ultrasound sensor 40 of the ultrasound system. The additional non- ultrasound sensor 40 can be one or more sensors selected from the group comprising: a pressure sensor 40a for sensing a pressure applied by the ultrasound probe 10 on the surface 2, a distance sensor for sensing a distance d travelled by the ultrasound probe 10 on the surface 2, a time sensor for sensing a time t which the ultrasound probe 10 travelled on the surface 2, a speed sensor for sensing a speed v of the ultrasound probe 10, a movement sensor for sensing a movement of the ultrasound probe 10, a camera for sensing a movement trajectory or a location of the ultrasound probe 10 on the surface 2, and a dryness sensor for sensing a dryness of the surface 2 of the body 1. In the embodiment of Fig. 2 the additional non-ultrasound sensor 40 is arranged in the ultrasound probe 10. However, the non- ultrasound sensor 40 can also be arranged in a separate device.

It will be understood that the ultrasound system of the second embodiment of

Fig. 2 can also comprise a processing unit 34 (indicated by dashed lines in Fig. 2) for processing the ultrasound signal 34a as explained with reference to Fig. 1. Further, it will be understood that the first embodiment of Fig. 1 and the second embodiment of Fig. 2 can be combined. In this case the sensor information 15a is based on both the ultrasound signal 34a and sensor information from additional non-ultrasound sensor(s) 40, as explained above. For example, in this way it the system can be prevented from releasing contact agent when the system is not placed on the surface for the ultrasound measurement or not performing the ultrasound measurement (e.g. while being idle). Thus, the additional non-ultrasound sensor(s) 40 (e.g. pressure sensor or movement sensor) can for example be used to prevent the system from releasing gel is not placed on the surface for the ultrasound measurement or not performing the ultrasound measurement (e.g. while being idle).

Fig. 3 shows a perspective view of an ultrasound system according to an embodiment, and Fig. 4 shows a perspective view of part (end portion) of the ultrasound system according to the embodiment of Fig. 3. The ultrasound system of Fig. 3 and Fig. 4 is in particular suitable for a consumer application. As can be seen in Fig. 4, the ultrasound probe 10 of the system comprises a single transducer element 24 for transmitting and/or receiving ultrasound waves in an ultrasound measurement area A. The system comprises a reservoir 9, containing contact agent, which is attached to the ultrasound probe 10. As can be seen in Fig. 4, there are a plurality of openings 11 in the ultrasound probe 10. Through these openings 11 the contact agent from the contact agent reservoir 9 is released into the ultrasound measurement area A. In this embodiment the openings 11 (arranged in a circle) completely surround the transducer element 24 or measurement area A. The system further comprises (not shown in Fig. 3 and Fig. 4) a contact agent delivery unit 13 and a control unit 15 for automatically controlling the contact agent delivery unit, as explained with reference to the first embodiment of Fig. 1 and the second embodiment of Fig. 2. As can be seen in Fig. 4, the system further comprises a pressure sensor 40a for sensing a pressure applied by the ultrasound probe 10 on the surface 2 and a movement sensor 40b for sensing a movement of the ultrasound probe 10. In this embodiment the sensor information 15a comprises at least the sensor information from the pressure sensor 40a and/or the sensor information from the movement sensor 40b.

Fig. 5 shows a perspective view of an ultrasound probe 10 of an ultrasound system according to an embodiment applied to skin 2 of a subject 1. The ultrasound system can in particular be the ultrasound system as described with reference to Fig. 3 and Fig. 4. The body to which the ultrasound probe 10 is applied is here an arm of the subject 1 in Fig. 5. In this ultrasound measurement the ultrasound probe 10 travels a distance d on the skin 2, for a specific time t and with specific a speed v. One or more of these parameters can be measured by a respective sensor and the automatic control of the contact agent delivery can be based on one or more of these parameters, as explained with reference to the second embodiment of Fig. 2.

Fig. 6 shows a schematic diagram of an ultrasound probe 10 of an ultrasound system according to an embodiment, the ultrasound probe 10 being positioned on the surface 2 of a body 1 having two tissue layers 16, 18. The body has a first tissue layer 16 and a second tissue layer 18, which are separated by a tissue layer boundary 20. The first tissue layer 16 is fat, the second tissue layer 18 is some other tissue, for example muscle. The ultrasound probe 10 has a transducer 22 which comprises a plurality of transducer elements 24 for transmitting ultrasound 26 and/or receiving reflected ultrasound 28. Ultrasound can mainly get reflected either from tissue layer boundaries 20 or from local tissue inhomogeneities 30. Usually, only a small percentage of the transmitted ultrasound 26 is reflected, so that ultrasound gets reflected also from tissue layer boundaries 20 or tissue inhomogeneities 30 that are located deeper inside the body. The arrow 32 indicates the direction of increasing depth. The elements 24 of the transducer 22 are connected to a processing unit 34 (or reconstruction unit), which computes a two-dimensional image.

Fig. 6 shows that the processing unit 34 (or reconstruction unit) is located on or in the ultrasound probe 10. However, in general it can also be located outside the ultrasound probe 10. Although not explicitly shown, it is understood that the processing unit 34 may also comprise a noise removal means, for example a noise removal means that is adapted to perform filtering or Otsu thresholding. The user can move the ultrasound probe 10 along a direction 38 that is tangential to the surface 2 of the body 1 and orthogonal to the plane of Fig. 6. For example, the user can slowly move the ultrasound probe 10 along the user's belly in order to get a full measurement of the fat layer of the belly. The ultrasound probe 10 comprises a tangential movement detection means 40 (or movement sensor), which can detect such tangential movement. The detection means 40 can be designed similar to the detection means that are used in computer mice, for example using an LED or laser with a corresponding photo detector. To determine the orientation of the ultrasound probe the probe further comprises an orientation sensor 42. While the user moves the ultrasound probe along the surface 2 of the body 1, the probe continuously acquires ultrasound images 36. The ultrasound images 36 thus correspond to adjacent positions on the surface 2 of the body 1. The images are typically 2D, but could also be 3D image volumes. The plurality of ultrasound images 36 is sometimes also referred to as frames of an ultrasound video.

The ultrasound system can in particular be configured to perform an algorithm or method for determining actual tissue layer boundaries of the body. Fig. 6a shows a schematic block diagram of a part of an ultrasound system for performing an algorithm or method for determining actual tissue layer boundaries, and Fig. 6b shows a flowchart of the corresponding method to the system of Fig. 6a. The ultrasound system comprises an ultrasound probe 10 for acquiring (SI 2) two or more ultrasound images 36 at adjacent positions of a surface 2 of the body 1, a converter 44 for converting (SI 4) said ultrasound images 36 separately to depth signals 46, wherein a depth signal 46 is obtained by summing intensities of one of said ultrasound images 36 along a line 66 of substantially constant depth in the body 14. The ultrasound system further comprises a detector 48 for detecting (S16) a set of candidate tissue layer boundaries 50 for an ultrasound image 36 by thresholding the depth signal 46 obtained for said ultrasound image 36, and a selection means 52 for selecting (SI 8) from a set of candidate tissue layer boundaries 50 a nearest candidate tissue layer boundary 54 that is nearest to the surface 2 of the body 1. The ultrasound system further comprises a processing means 56 for determining (S20) an actual tissue layer boundary 58 from the nearest candidate tissue layer boundaries 54 obtained for various ultrasound images 36. Optionally, the ultrasound system can further comprise a display 60 for displaying the tissue layer boundary 58.

The ultrasound system of the ultrasound probe shown in Fig. 6 or Fig. 6a further comprises (not shown in Fig. 6) a reservoir 9 containing contact agent, at least one opening 11 for releasing the contact agent into the ultrasound measurement area A, a contact agent delivery unit 13 for delivering a specific amount of the contact agent through the at least one opening 11, and a control unit 15 for automatically controlling the contact agent delivery unit 13 as explained above, in particular as explained with reference to the first embodiment of Fig. 1 or the second embodiment of Fig. 2.

Referring to Fig. 6b, in a first step S10, the probe 10 is positioned on the surface 12 of the body 14. At step S12, images 36 are acquired with the probe 10. At step S14, the converter 44 converts some of these images to depth signals 46 by summing the intensities of the image 36 along a line that corresponds to essentially constant depths in the body. At step SI 6, the detector 48 uses thresholding of the depth signal 46 to detect candidate tissue layer boundaries 50. At step 20, the selection means 52 selects from a set of such candidate tissue layer boundaries 50 a nearest candidate tissue layer boundary 54 that is nearest to the surface 2 of the body 1. At step S20, the processing means 56 determines an actual tissue layer boundary 58 from said nearest candidate tissue layer boundaries, which were selected for various images 36. At step S22, the actual tissue layer boundary 58 is displayed on a display 60. In addition to the display 60, the system may also comprise a user interface, e.g. for changing settings of the tissue layer measurement.

Fig. 7 shows a screen shot of an ultrasound image displayed on a display of an ultrasound system. The display of Fig. 7 is in particular the display 60 as explained with reference to Fig. 6a and Fig. 6b. The display 60 shows an ultrasound image window 62 in which the actual tissue layer boundary 58 is displayed, as explained above. The ultrasound image window 62 shows the tissue layer boundary 58 as a function of time or distance travelled by the ultrasound probe. As can be seen in Fig. 7, there is a circled portion 62a (or time period or area travelled) of the ultrasound image window 62 in which no actual tissue layer boundary 58 can be seen. This is an area (or time period or area travelled) where no or an insufficient amount of contact agent or contact gel is present on the surface 2 of the body (or skin of the subject). The circled portion 62a (or time period or area travelled) marks an area in the image (or time period or area travelled) where gel application has been

insufficient. For this area (or time period or area travelled) the algorithm for automatically determining actual tissue layer boundaries does not work and therefore layer thickness cannot be quantified due to a too low signal-to-noise ratio. Thus, in this case the sensor information can be information on the ability of the algorithm to interpret an ultrasound image.

In one embodiment the probe dispenses the contact agent based on the image quality information from the transducer. The agent is dispensed in a way that just a sufficient image quality for a working algorithm is assured.

In another embodiment the probe dispenses the contact agent based on the information of the pressure sensor(s) together with the image quality information from the transducer. Low pressure requires more contact agent than high pressure, but for very high pressure, it might be wise to increase the agent flow (or gel distribution pressure) to make sure some agent is still present between the transducer and the skin.

In another embodiment the probe dispenses the contact agent in dependence of the speed and displacement of the probe on the skin, together with the image quality information from the transducer. Fast movements require more contact agent than slower scans and longer contact times require more agent (proportionally to the drying coefficient or absorption coefficient of one or more of the contact agent components).

In another embodiment any combination of the above mentioned sensor information can be implemented, e.g. a combination of pressure, displacement and/or transducer information to adjust the disposal of the contact agent.

One or more of the following assumptions can be made: trajectory scans require more contact agent than On the spot' measurements, fast movements require more contact agent than slower scans, longer contact time requires more contact agent

(proportionally to the drying coefficient or absorption coefficient of one of more of the contact agent components), low pressure requires more gel than high pressure, but for very high pressure, it might be wise to increase the gel flow (or gel distribution pressure) to make sure some gel is still present between the transducer and the skin.

The contact agent can for example be or comprise one or more agents selected from the group comprising ultrasound gel, water, alcohol, alcohol gel (e.g. DESC017), high viscous gel, gel pad, and a combination of any.

The use of alcohol gel can be advantageous, since manual removal is not required due to vaporizing properties. Although the gel needs a higher viscosity than water in order to prevent dripping, the viscosity of the used ultrasound gel might be too high. Air bubbles stay trapped in the gel. Because the viscosity of alcohol gel is lower than ultrasound gel (but higher than water), gel bubbles disappear after a while.

The system can for example be used in one of the following applications: Automated Body composition monitoring for Lifestyle applications, Body composition monitoring for Healthcare, Personal Healthcare, Home Healthcare and Targeted Diagnostics applications. The system can for example be applicable for all healthcare related Outside body' transducers, such as for example in shaving, grooming or ultrasound-based drug delivery or ultrasound-based creme active ingredient penetration (the therapeutic ultrasound domain).

Body mass index (BMI) is the most widely used measure to diagnose obesity and to track changes in the development of body weight and composition. However, there are a couple of associated problems with using the BMI: The accuracy of detecting body adiposity in the adult population is largely unknown. Certainly there is a strong correlation between BMI and morbidity as well as mortality. Nevertheless, several studies worldwide have shown that people with slightly elevated BMIs have similar or even better outcomes regarding e.g. cardiovascular events compared to normal weight BMIs. However, these surprisingly favorable prognostic implications are probably in fact due to a limited diagnostic performance of the BMI due to the inability to discriminate between adipose tissue and lean body mass in intermediate BMI ranges. Furthermore, the BMI is not independent of age, gender and ethnicity, which in consequence would require adjusted reference tables for these variables. Additionally, increased bone mass, muscle mass or plasma volume as an effect of training also effect the numerator of the BMI.

To really get insight into a body's proportional composition it is necessary to distinguish several main tissues from each other. Therefore several body composition models have been developed throughout the last years. The pivotal tissues to detect from a health perspective therefore are: fat mass and fat-free mass, lean body mass and muscle mass and a further discrimination of adipose tissue in subcutaneous and intra-abdominal adipose tissue.

The system and ultrasound probe can be used to detect thicknesses of different tissue layers in the body, and to process this information to derive the respective information about the different compartments of the body, as explained above with reference to Fig. 6, Fig. 6a, Fig. 6b and Fig. 7.

In the preceding description an ultrasound system has been described.

However, it will be understood that the present invention can in a general case also be applied to a system for performing any action on skin 2 of a subject 1. Such system can for example be a shaver, but is not limited thereto. In the example of a shaver the system performs a shaving process on the skin of a subject and releases contact agent in the form of a shaving fluid, foam or cream (in order to reduce skin irritations).

In this general case, Fig. 1 shows a schematic diagram of such system according to a first embodiment, and/or Fig. 2 shows a schematic diagram of such system according to a second embodiment. In Fig. 1 or Fig. 2 the system comprises a reservoir 9 containing contact agent, an action performing element 24 (e.g. the transducer elements of an ultrasound system or a shaving blade of a shaver) for performing an action on the skin 2 in an action area A (e.g. an ultrasound measurement area for an ultrasound system or a shaving area for a shaver), at least one opening 11 for releasing the contact agent into the action area A, a contact agent delivery unit 13 for delivering a specific amount of the contact agent through the at least one opening 11, and a control unit 15 for receiving sensor information 15a on the performed action and for generating a control signal 15b based on the sensor information 15a, the control unit 15 automatically controlling the contact agent delivery unit 13 based on the control signal 15b. The same embodiments and details as discussed with reference to an ultrasound system can also be applied to such general system for performing an action on skin 2 of a subject.

Just an example, the system for performing an action on skin 2 of a subject 1 can be a shaver and the contact agent can be shaving fluid, foam or cream (e.g. Nivea cream). For example, the sensor information can be based on the shaving quality and sensor information from a movement sensor. In another example, the sensor information 15a can be based on the age of the shaver and sensor information from a movement sensor.

While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive; the invention is not limited to the disclosed embodiments. Other variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. A single element or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage. A computer program may be stored/distributed on a suitable medium, such as an optical storage medium or a solid-state medium supplied together with or as part of other hardware, but may also be distributed in other forms, such as via the Internet or other wired or wireless telecommunication systems.

Any reference signs in the claims should not be construed as limiting the scope.