CN117897108A - Method and system for determining skin freeze during cooling - Google Patents

Abstract

The present disclosure relates to applicators, cooling systems comprising such applicators, and methods for cooling treatment of skin folds of a subject. A method for determining a freeze event includes measuring an electrical impedance between a contact plate and a return electrode of an applicator. The method further comprises determining a possible movement, which may also be based on a measurement of the electrical impedance.

Description

Method and system for determining skin freeze during cooling

Technical Field

The present application claims priority from European patent application number 21382374.3 filed on 28, 4, 2021.

The present disclosure relates to methods and systems for determining a freeze event of skin during cooling. The present disclosure relates in particular to applications of such systems and to methods for determining a freeze event based on measuring electrical impedance.

The present disclosure also relates to methods and systems for treating, and in particular cosmetically treating, a subject to locally reduce adipose tissue, and more particularly to methods and systems for locally reducing adipose tissue in a safe manner.

US2016/0045755 discloses a system and method for reducing fat. In some embodiments, these include applicators with electrodes that form capacitors to heat tissue.

US2012/0022518 discloses systems and methods that enable delivery of radiofrequency and cryotherapy applications to adipose tissue to reduce body fat and shape body fat contours.

WO 2007/093998 discloses a method and apparatus for treating adipose tissue. The method includes applying ultrasonic energy to an adipose tissue region. In an embodiment, the RF electric field is generated in conjunction with ultrasonic energy within the adipose tissue region.

US2002/0049483 discloses a fluid delivery device for introducing a fluid cooling medium to a skin surface, the fluid delivery device comprising a template having a skin interface surface. An energy delivery device is coupled to the template.

Background

Liposuction has been performed for many years to reduce excess body fat in patients. Much less invasive treatments aimed at locally reducing adipose tissue by applying cold to the skin folds of a subject have also been commercially provided for many years. Subcutaneous adipose tissue has been found to be more sensitive to cold than other tissues. By applying cold to the skin, the underlying lipid-rich cells are damaged and destroyed, while other tissues are not damaged or are less damaged. Over time, lipid-rich cells die and disappear through natural apoptotic processes. Thereby, a cosmetic treatment for locally reducing fat can be provided.

For such cold treatment, treatment devices having one or more applicators comprising a cavity are known. Suction may be applied to the cavity to inhale skin folds of the subject. One or more thermally conductive (metal) contact plates may be provided on the inside of the cavity. Thermoelectric cooling elements (peltier elements) may be used to cool the plate to a low temperature. Although thermoelectric cooling elements are most widely used, alternative cooling methods based on a cold fluid, such as cooling a conductive plate, may also be used.

The contact plate may be substantially flat. One or more contact plates may be disposed in the cavity of the applicator. A single curved contact plate or multiple curved contact plates may also be used to conform to an area of the subject's body.

Some form of temperature control is typically provided to control the temperature of the contact plate and thus the skin. In some known devices, the temperature of the skin may be measured during treatment. In contrast, in other known devices, the temperature of the conductive plate is measured during treatment.

By sucking in the skin folds, an improved contact between the skin and the cooling element (e.g. the metal contact plate) is achieved. Additionally, by squeezing skin folds between the metal plates, local blood flow may be reduced. Thereby, the supply of heat to the area may be reduced and cooling may be more efficient. Applicators that do not rely on inhalation of skin folds are also known.

The risk of patients suffering from pain and serious injury is related to freezing of the skin or the formation of crystals in the skin during such treatment. It is known that freezing of the skin may occur around or below 0 ℃, depending on the time of exposure.

In order to avoid freezing of the skin, it is known to use cryoprotectants. Cryoprotectants are substances that may be used to protect biological tissue from freezing damage (e.g., due to the formation of large ice crystals).

One of the challenges associated with the use of cryoprotectants in such cold treatment relates to the effective protection of the skin by cryoprotectants. In order to be able to effectively perform cold treatment, the treatment may apply a temperature of less than-5 ℃ or less (e.g. -10 ℃ or less) to the metal sheet during a long period of time (e.g. more than 30 minutes and more particularly more than 45 minutes and even more than an hour).

US 7,367,341 relates to a method for selectively destroying lipid-rich cells by controlled cooling. Feedback mechanisms to be employed in these methods to monitor and control the temperature of the skin are described. Such feedback mechanisms may include, for example, an invasive thermocouple to locally measure temperature. In addition, ultrasound imaging, acoustic, optical and mechanical measurements are mentioned to monitor crystal formation. An electrical feedback device may be used to monitor changes in the electrical impedance of the epidermis caused by icing in the epidermis. These monitoring systems are not explained in detail except for invasive temperature measurements.

WO 2009/026471 discloses a monitoring system, or describes detection of events during heat removal from subcutaneous lipid-rich tissue. In some examples, the system detects an increase in temperature at a treatment device in contact with the skin of the subject, determines that the increase in temperature is related to a treatment event, and performs an action based on the determination. In some examples, the system turns off the treatment device, alerts the operator, or reduces cooling in response to a determined treatment event.

One disadvantage associated with some of these prior art systems is that they are complex and therefore costly to integrate into a system for locally reducing adipose tissue. Another disadvantage associated with many of these prior art systems is that localized freezing events of the subject's skin may not be detected. That is, if freezing occurs in a portion of the skin that is not just in the vicinity of the probe or sensor, the freezing may not be detected until the freeze-up spreads out. When freezing is detected, damage may have occurred.

There remains a need for devices that can provide safe and effective treatment of the skin and avoid or reduce one or more of the foregoing problems.

Disclosure of Invention

In a first aspect, an applicator for a system for cooling a skin portion of a subject is provided. The applicator includes a cooling element having a cooling surface for contacting a skin portion of a subject to cool the skin portion of the subject. The cooling element is electrically conductive and the cooling surface has a lower electrical conductivity than the remainder of the cooling element. The cooling system is configured to determine an electrical impedance between the cooling element and a first return electrode configured to be placed on a body of the subject.

With an applicator according to the present aspect, the electrical impedance may be used to determine a freezing event. With the applicator according to the present aspect, the electrical impedance between a substantial part of the cooling surface and the first return electrode is measured, instead of a point-by-point measurement as known from the prior art. Thus, the determination of the freeze event may be more reliable than in the prior art.

By low conductivity is meant that the conductivity of the surface is at least 30% lower than the conductivity of the cooling element, in particular at least 50% lower. In certain examples, the surface of the cooling element may be substantially non-conductive. Substantially non-conductive as used throughout the present disclosure may be understood to mean a conductivity of 1.000 Ω.cm or more, more specifically 10.000 Ω.cm or more.

In some examples, the cooling element may be a metal contact plate, optionally an aluminum plate, with an anodized aluminum layer as the cooling surface. Aluminum has a high thermal conductivity and is therefore an effective and efficient cooling element. Anodized aluminum can be provided relatively easily. Its electrical characteristics vary depending on its composition, but may have a high resistivity of, for example, 10 ⁹ Ω.cm or more, even 10 ¹¹ Ω.cm or more.

In some examples, a cable is used to provide current to the cooling element, wherein the cable is attached to the cooling element with a screw.

In some examples, the current used to determine the electrical impedance is less than 35mA, specifically less than 1mA, more specifically 0.5mA or less. Very little current can be used to measure the electrical impedance and thus the user experience during cooling treatment is not negatively affected.

In some examples, the applicator may include an accelerometer for measuring movement of the subject. In other examples, the electrical impedance between other electrodes may be used to determine possible movement of the subject or possible movement of the applicator relative to skin folds of the subject.

In yet another aspect, a cooling system for cooling a skin portion of a subject is provided, the cooling system comprising a base station and one or more applicators according to any of the examples disclosed herein. The applicator is configured to be coupled to a base station, optionally via a flexible tube. In an example, such flexible tubing may be configured to provide an electrical and/or electronic and/or pneumatic connection between the control base station and the applicator.

The control circuit, power supply and pneumatic system may be provided in the base station. The applicators can be controlled from the base station. Measurements (e.g., temperature, impedance) in the applicator may be measured and the measurements may be provided to the base station. In an example, some control circuitry may be provided in a separate applicator.

In some examples, the first return electrode is configured to be placed on an extremity of the subject. In order to improve the measurement of the electrical impedance, it is advantageous to have a distance between the cooling element and the return electrode. The subject's arms and legs may be suitable for this purpose, particularly when performing cooling treatment on the abdomen, chin tissue or buttocks.

In some examples, the cooling system may be further configured to determine a freezing of the skin of the subject based on the electrical impedance, in particular based on a change in the electrical impedance. If a freeze event is determined based on the electrical impedance, the applicator does not require a specific additional auxiliary system to measure movement.

In some examples, the cooling system may be further configured to determine the freezing of the skin based on a time derivative of the electrical impedance. It has been found that the change in electrical impedance (and in particular the time derivative) is a better indicator of a freezing event than the absolute value of the measured electrical impedance.

In addition to freezing events, electrical impedance may also be used to determine movement. If the same electrical parameters are used to measure both movement and freeze events, the system or component may combine and integrate different functions, thereby reducing complexity and reducing independent failure of the system. The system may be configured to determine movement of the subject or movement of the skin portion relative to the cooling element by determining an electrical impedance between the movement sensor electrode and the movement sensor return electrode. Optionally, the movement sensor return electrode may be a first return electrode, i.e. the same electrode used in the measurement of the freeze event.

The movement sensor electrode may be arranged near or around a cavity of the applicator, the cavity being configured to receive the skin fold such that movement of the applicator relative to the skin fold may be measured by both systems. If, on the contrary, only the system involving the cooling element measures a significant event, while the other system for detecting movement does not, the probability of an actual event increases. Negative false positives (FALSE NEGATIVE) and positive false positives (false positives) can be reduced in this way.

In yet another aspect, a method for determining a freezing event during cooling therapy is provided. The cooling element cools the skin portion of the subject during the cooling treatment. The method includes determining a first electrical impedance between the cooling element and a first return electrode disposed on the subject, and determining a time derivative of the determined first electrical impedance. The method further comprises determining movement using a mechanism for detecting movement, the movement comprising movement of the subject and/or movement of the skin portion of the subject relative to the cooling element. The method comprises the following steps: a freeze event is determined if the time derivative of the first electrical impedance during the first time slot satisfies one or more freeze conditions and if distortion of the first electrical impedance caused by movement in the same time slot is discarded.

More than one freeze condition may be established to reduce positive false positives. More than one criterion for determining possible movements may be established to reduce negative false positives.

The time derivative may be understood as the derivative of the function with respect to time (in this case the measured first electrical impedance). The determined time derivative of the first electrical impedance may in particular be a first or a second time derivative.

If no indication of a possible movement is derived from the means for detecting movement or if the possible movement derived from the means for detecting movement is insufficient to cause the freeze condition to be met, distortion in the first time slot due to movement may be discarded.

Throughout this disclosure, a "first time derivative" may be understood as a first time derivative, i.e. it represents the rate of change of a variable with respect to time. Throughout this disclosure, "first time derivative," "first derivative," and "first order time derivative" may be used interchangeably.

In a further aspect, a method for reducing adipose tissue, in particular a cosmetic method for reducing adipose tissue, is provided. The method comprises the following steps: providing a cooling system according to any of the examples disclosed herein; providing contact between a skin portion of a subject and a cooling element of a cooling system; and cooling the skin portion of the subject, for example, during a period of up to 70 minutes, 90 minutes, 120 minutes or more. The method further includes performing a method for determining a cooling event as disclosed herein during cooling.

In an example, if a freeze event is detected, cooling of the skin portion may be discontinued, and/or an alarm may be generated, and/or temporary heating (rather than cooling) may be performed to avoid damage to the subject's skin.

In an example, the method may further comprise checking the correct operation of the cooling system by determining an electrical impedance between the cooling element and the first return electrode and/or by determining an electrical impedance between the moving electrode and the moving return electrode. If proper contact with the skin is provided, the electrical impedance will be within the expected range. Such measurements may be used during the cooling treatment or at the beginning of the cooling treatment or even before the beginning of the cooling treatment to determine that skin wrinkles are in contact with the contact plate. If cryoprotectant (pad) is used, proper placement of the cryoprotectant pad may also be checked by measuring electrical impedance.

Throughout this disclosure, the term "skin" when used in connection with freezing times may refer to dermis, epidermis, or both.

Drawings

Non-limiting examples of the present disclosure will be described below with reference to the accompanying drawings, in which:

FIG. 1 schematically illustrates an example of a cooling system;

FIGS. 2A and 2B schematically illustrate examples of applicators and cooling systems comprising such applicators;

FIG. 3 schematically illustrates a method for reducing adipose tissue according to an example;

FIG. 4 schematically illustrates a method for determining a freeze event during a cooling treatment according to an example;

Fig. 5 and 6 schematically illustrate further examples of methods for determining a freezing event during a cooling treatment; and

Fig. 7 and 7A schematically illustrate signals of an impedance sensor and a method for evaluating such signals according to an example.

Detailed Description

Fig. 1 schematically shows an example of a cooling system that may be used in a method for reducing adipose tissue, in particular a cosmetic method for reducing adipose tissue.

The method may include providing a cooling system as shown in fig. 1. The cooling system of fig. 1 includes a base station 100 and one or more applicators 110, 120. The base station may include a user interface 150 that includes a screen that may indicate information regarding the cooling therapy.

The user interface 150 may include a touch screen. A touch screen and/or one or more control buttons or handles may be used to select an appropriate cooling treatment and/or adjust parameters of the cooling treatment.

The applicators 110, 120 may each be connected to the base station by flexible tubing or hoses 105, 115. Such flexible tubing 105, 115 may be configured to provide electrical and/or electronic and/or pneumatic connections between the base station and the applicator.

The base station may have a power supply, for example, a plugged cable.

The applicators may be of different sizes and shapes suitable for cooling different parts of the subject's body. In a method for reducing adipose tissue, a skin fold of a subject may be introduced into a cavity of an applicator, and a portion of the skin of the subject may be brought into contact with a cooling element of the applicator.

The cooling treatment may include cooling a skin portion of the subject during a period of up to 90 minutes. Depending on the skin portion to be cooled, and depending on the purpose of the treatment, the duration and other settings (e.g., temperature) may vary.

In an example, cooling the skin portion comprises controlling the temperature of the cooling element between 0 and-15 ℃, in particular between-5 ℃ and-13 ℃. The skin portion of the subject may be one or more of the thighs, buttocks, abdomen, under chin tissue, knees, back, face, and arms. The cooling system may include multiple applicators and may treat multiple skin folds simultaneously.

In case the temperature is below 0 ℃ for a long time, the skin may freeze. To avoid such freezing, a pad or absorbent with a cryoprotectant may be used. A cryoprotectant may be disposed between the skin and the cooling element to protect the skin.

In examples of the present disclosure, the method for determining a freeze event may be performed continuously throughout the cooling element. If a freezing event is detected, the cooling treatment may be discontinued or otherwise altered to avoid damaging or injuring the subject's skin. If a freeze event is detected, cooling of the skin portion may be discontinued. In an example, a method may include temporarily heating a cooling element if a freeze event is detected. In an example, an audible or visual alert may be generated such that if a freeze event is detected, an operator may intervene by manually changing the therapy, interrupting the therapy, disconnecting the base station, and so forth.

Fig. 2A and 2B schematically illustrate an example of an applicator 10 and a cooling system for treating skin folds of a subject 90. As in the example of fig. 1, the cooling system of fig. 2B may include a base station 100 with a user interface 150 and a plurality of applicators 110, 120, 160. The applicator may be similar to the applicator 10 shown in fig. 2A.

The applicator 10 may include a cavity 2 for receiving a skin fold. An orifice connected to the suction system may be provided in the bottom of the cavity 2. The pump and power supply for sucking the skin fold into the applicator may be incorporated in the base station. A flexible tube or hose 5 may connect the applicator 10 to a corresponding base station. The applicator 10 may include suitable couplings for coupling to the tube 5. Providing suction or vacuum may help ensure contact between the skin fold to be treated and one or more contact plates 3 arranged within the cavity.

Depending on the skin fold to be treated, the applicator may comprise one or more flat contact plates, e.g. two contact plates at two opposite positions of the cavity. In other examples, a single contact plate is included that may be curved and/or may be shaped as a cup.

The applicator 10 of the system for cooling a skin portion of a subject comprises a cooling element 3 having a cooling surface for contacting the skin portion of the subject to cool the skin portion of the subject. The cooling element is electrically conductive and the cooling surface has a lower electrical conductivity than the remainder of the cooling element. The cooling system may be configured to determine an electrical impedance between the cooling element 3 and a first return electrode 190 configured to be placed on the body of the subject.

The cooling element 3 may be a metal contact plate, optionally an aluminium plate. The aluminum plate may have a relatively good thermal conductivity. The applicator may also include a thermoelectric cooler configured to cool the metal contact plate. Each of the contact plates may be cooled with a peltier element. By controlling the power supplied to the peltier elements, the temperature of the contact plate and thus the cooling of the skin folds can be controlled. The temperature sensor may be arranged in contact with the skin or alternatively may measure the temperature of the contact plate or the peltier element.

The cooling surface may be substantially non-conductive. The higher resistivity of the cooled surface means that the entire contact plate can act as an electrode for impedance measurement. The cooling surface includes a non-conductive coating. The cooling surface may be an anodized aluminum layer.

The applicator 10 may comprise a cable for providing current to the cooling element, wherein the cable is attached to the cooling element with a screw. The current used to determine the electrical impedance may be less than 35mA, specifically less than 1mA, more specifically 0.5mA or less.

The applicator 10 may also include a mechanism for determining movement. The movement may include movement of the applicator, movement of the skin fold relative to the applicator, or movement of the subject. Such movement may affect the measurement of the electrical impedance and, thus, may affect the reliability of the determination of the freezing event.

In some examples, the applicator 10 may include an accelerometer for measuring movement of the subject. In other examples, another impedance measurement may be used to detect movement.

In some examples, the first return electrode 190 may be configured to be placed on an extremity of the subject. The electrical impedance between the contact plate 3 and the first return electrode 190 can be measured to determine possible freezing of the skin.

The cooling system may be configured to determine the freezing of the skin of the subject based on the electrical impedance, in particular based on a change in the electrical impedance, by receiving the signal and analyzing the signal from the applicator regarding the electrical impedance.

In an example, the cooling system may be configured to determine the freezing of the skin based on a time derivative of the electrical impedance. It has been found that in particular, a change in the electrical impedance may be a reliable indication of a freezing event.

In an example, the cooling system is further configured to determine movement of the subject or movement of the skin portion relative to the cooling element by determining an electrical impedance between the movement sensor electrode 14 (in fig. 2A) and the movement sensor return electrode. In fig. 2B, the motion sensor electrode 14 is integrated in the applicator. The movement sensor electrode may be attached to the applicator, for example, by fasteners (such as screws) or by adhesive or any other suitable means. In an example, a kit may be provided in which the applicator may be upgraded or retrofitted with a suitable system that measures electrical impedance to determine possible freezing.

In alternative examples, the motion sensor electrode 180 may be separate from the applicator.

In an example, the motion sensor return electrode can be the first return electrode 190, i.e., the same return electrode used in conjunction with the contact plate.

Fig. 3 schematically illustrates a method for reducing adipose tissue according to an example. In any of the examples disclosed herein, the skin fold to be treated may be one of the following areas of the subject: thigh, buttock, abdomen, submaxillary tissue, knee, back, face, arm. In any of the examples disclosed herein, several skin folds may be treated simultaneously. For example, a single treatment device may include more than one applicator, and the applicators may be applied to different skin folds simultaneously.

At block 210, a configuration for cooling may be determined. This configuration may depend in particular on which body part is treated. In particular, the cooling temperature and the cooling time may be configured. The cooling temperature may be related to the temperature of the subject's body at the treated area (e.g., the temperature measured at the epidermis) or the temperature of the cooling element.

In an example, the contact plate of the treatment device may be maintained at a temperature below 0 ℃, more particularly below-5 ℃ for a period of 15 minutes to 90 minutes. In particular, the contact plate may remain in contact with the skin for a period of between 20 minutes and 75 minutes. The treatment time may be adapted to the area of skin being treated. The treatment time for some areas of the skin may be, for example, 30 to 50 minutes, and for other areas of the skin, the treatment time may be, for example, 60 to 75 minutes.

In some examples, a base station of a cooling system may have a plurality of predefined and stored cooling programs. The operator can simply select the best treatment or body part to be treated. Alternatively, the base station may be able to determine which applicator to activate or connect to the base station. If the applicator can only be used in a single area, the base station can thus automatically identify the area or body part being treated and automatically select the appropriate configuration. Alternatively, the base station may identify the applicator, and the operator indicates (e.g., selects on the base station) which particular region, area, or body part of the different regions or areas that may be treated with the particular applicator is to be treated.

Skin folds may be introduced into the applicator. The cryoprotectant may be disposed between the skin fold and a contact plate in the applicator. At block 220, the skin folds may be specifically cooled, wherein the purpose is to cool the adipose tissue to locally reduce fat.

During the cooling treatment, continuous monitoring may be performed at block 230 to detect a freezing event. If such a freeze event is detected at block 230, at block 240, the freeze may be mitigated by any of a number of ways commented herein, including disconnecting the cooling system, heating the contact plate (temporarily), shutting down the cooling system, and so forth.

Fig. 4 schematically illustrates a method for determining a freezing event during a cooling treatment according to an example. During the cooling treatment, the impedance may be measured substantially continuously. The measured impedance at block 310 means the electrical impedance between the metal contact plate and the first return electrode. Measuring the impedance may be performed at a frequency of, for example, between 1kHz and 1000kHz, in particular between 10kHz and 200 kHz.

At block 320, based on the measured impedance, a likely freeze event of the user's skin may be determined. If the electrical impedance develops in a manner that will not suspect a freeze event, the flow chart passes to block 340 and the conclusion is that there is no freeze event. It will be appreciated that the method is continuous, i.e. the measurement of the impedance may be performed continuously, and thus conclusions about the freezing may be drawn continuously.

If a possible freeze event is detected at block 320, a determination may be made at block 350 as to whether there is a possible movement. In an example, at block 330, movement may be measured continuously. If the electrical impedance measured at block 310 develops in a manner that detects freezing and, at the same time, no movement is detected, then at block 360 a conclusion may be drawn that a freezing event exists. The reason for checking for possible movement is to reduce false positives, as movement may cause impedance changes similar to a freeze event.

According to this example, the possible movements may be measured continuously, but only if a freeze event is suspected, an evaluation of the possible movements is made.

An alternative example is shown in fig. 5. As in fig. 4, the movement and the electrical impedance between the cooling element and the first return electrode placed on the subject may be measured continuously (blocks 310, 330). Movement may be measured by determining an electrical impedance between the movement sensor electrode and the movement sensor return electrode. The motion sensor return electrode may be a first return electrode.

Possible freezing elements may be detected independently of each other and continuously, and possible movements may be detected (blocks 320, 340).

As long as no freezing event is suspected, a conclusion is drawn at block 340 that there is no freezing event and thus no reason to interrupt or modify the cooling therapy. If a freeze event is suspected, it is verified whether the movement may affect the determination of the freeze event. If at the same time, the freezing element is suspected and a determination is made that the movement cannot result in such a determination, then a conclusion is drawn at block 360 that a freezing event has occurred or is occurring.

In the example of fig. 5, a further block 370 is introduced. If a freeze event is suspected and movement is simultaneously suspected, a further check is made to determine if an actual freeze event exists. At block 370, further evaluation may be performed by comparing the electrical impedance measured for movement detection with the development or change in electrical impedance measured for determining a freeze event. If a freezing event occurs, the electrical impedance in both measurements may increase, but may be more pronounced between the cooling element and the return electrode.

In either of the examples of fig. 4 and 5, a freezing event may be suspected if the electrical impedance satisfies one or more freezing conditions.

In any of the examples, a method for determining a freezing event during a cooling treatment includes determining (block 310) a first electrical impedance between a cooling element and a first return electrode placed on a subject, and determining a time derivative of the determined first electrical impedance, wherein the cooling element cools a skin portion of the subject.

In particular, a first order time derivative may be used. The first time derivative indicates the rate of change of the first electrical impedance and has been found to be able to reliably indicate a possible freezing event even if the first time derivative is above a threshold.

In other examples, a second order time derivative may be used. The second time derivative is indicative of the acceleration of the first electrical impedance. An outlier of the second time derivative over time may also indicate a possible freeze event. In one example, the absolute value of the second time derivative may be compared to a threshold.

The method may also include determining movement (block 320) including movement of the subject and/or movement of a skin portion of the subject relative to the cooling element using a mechanism for detecting movement.

If the first time derivative of the first electrical impedance satisfies one or more freezing conditions during the first time slot, and if distortion of the first electrical impedance caused by movement in the same time slot is discarded, a freezing event may be determined. The first freezing condition is that the first time derivative of the first electrical impedance is above a first freezing threshold during the first time slot.

In some examples, the first freeze threshold is determined based at least in part on a measurement of the first time derivative. In an example, the first freezing threshold may change over time.

Yet another example is shown in fig. 6. At block 405, a signal may be received regarding an electrical impedance between the cooling element and the first return electrode. At block 410, a filter may be applied to the received signal. In particular, an averaging filter may be applied, for example, a plurality of individual measurement points may be summed and averaged and correlated with a single measurement time (in the middle of the averaged measurement points).

In an example, impedance measurements may be made at a frequency of between 1kHz and 1.000kHz, and specifically between 50 and 200kHz, and more specifically about 100 kHz.

The sampling time of the averaging filter may be 0.1 seconds to several seconds, and in particular between 0.5 seconds and 2.5 seconds.

Similarly, at block 505, a signal is received regarding an electrical impedance between the moving sensor electrode and the moving return electrode. At block 510, a similar averaging filter may be applied. The measurement frequency and average may be the same or on the same order of magnitude as the impedance measurement for movement and the impedance measurement for detection of a potential freeze event.

After filtering, at blocks 415, 515, the time derivatives, particularly first order time derivatives, of the two measurements may be determined. At blocks 430 and 440, a plurality of freeze conditions may be defined for the first time derivative of the electrical impedance.

The first freezing condition (block 430) may be that the first time derivative of the first electrical impedance is above a first freezing threshold or between predefined first freezing thresholds during the first time slot. Thus, the freezing threshold corresponds to the value of the rate of change of the electrical impedance. In some examples, the first freezing threshold may change over time. Optionally, rather than comparing individual values of the first time derivative to a threshold value, an average of two or more time instants may be used.

In one example:

impedance change= (current impedance change-last impedance change)/2 (equation 1)

Peak = impedance change/first threshold value (equation 2)

First_threshold_value= (fixed_threshold value_gain_threshold) + (abs [ impedance_change ] _gain_impedance) (equation 3)

Equation 1 expresses the average of the first time derivative of the electrical impedance over two time slots. Equation 2 defines the peak value as the ratio between the first time derivative of the electrical impedance and the threshold value. If the peak is at a predefined level, a freeze event may be detected. If the peak is low, freezing is not possible because the electrical impedance changes too low. If the peak is too high, a freezing event is not possible, as there must be another reason to cause the electrical impedance to change very rapidly (e.g., losing contact between the skin and the cooling element, and the like). Equation 3 indicates how the first threshold may change over time, taking into account measurements from specific components in a specific cooling treatment.

At block 440, a second freeze condition may be defined. In this example, the second freezing condition is that an integer value of the (natural) logarithmic value of the first time derivative is above a second freezing threshold during a second time slot, wherein the second time slot is longer than the first time slot.

Ln_value= Σ (Ln (peak value)/second slot (equation 4)

The second time slot may be longer than the first time slot. The first time slot (for the first time derivative) may be between 1 second and 5 seconds, in particular between 1 second and 4 seconds. The second time slot may be longer. In an example, the second time slot may be 5 seconds.

If both the first and second freezing conditions are met, the algorithm passes to block 450 or block 540 as will be explained below. If either of the freeze conditions is not met, a conclusion is drawn at block 490 that no freezing has occurred.

Meanwhile, at block 515, a first time derivative of the electrical impedance between the motion sensor electrode and the return electrode may be determined, and at block 530, a first motion criterion may be defined.

If the first time derivative of the electrical impedance between the motion sensor electrode and the motion sensor return electrode during the first time slot is above a motion threshold or between predefined motion thresholds (block 530), a possible motion may be deduced. At block 530, similar equations 1 through 3 may be applied, but for signals related to the motion sensor.

The movement threshold may be determined based at least in part on the measurement of the first time derivative. The first movement threshold may vary over time.

If at block 530, movement is not determined or suspected, and freezing is suspected at blocks 430 and 440, then at block 450, a third freezing condition may be checked.

In an example, the first time derivative (in particular the first time derivative of the electrical impedance between the cooling element and the return electrode) may be determined over a time window having a first span and a time window having a second span, the second span being longer than the first span. In practice, different averaging filters may be applied. For example, a first averaging filter based on 32 measurement points may be applied, and at the same time, a second averaging filter based on 64 measurements may be applied. It should be appreciated that 32 and 64 are mentioned by way of example only. In an example, a "Haar" filter is used.

The third freeze condition at block 450 may be defined as a first time derivative (in this example, an average filter having 32 points) determined over a first span during a first time slot that is substantially different than a first time derivative (an average filter having 64 points) measured over a second span. If freezing occurs, the first order time derivative with the average filter over a shorter time span will be different from the first order time derivative with the average filter over a longer time span. If, in contrast, the averages are not significantly different, then the third freezing condition is not met and a conclusion is drawn at block 490 that there is no freezing event.

If the first and second freezing conditions are met at blocks 430, 440 and the movement criteria are met at block 530, a further determination may be made as to whether the movement has distorted the electrical impedance measurement.

In an example, if no indication of a possible movement is derived from the means for detecting movement, or if the possible movement derived from the means for detecting movement is insufficient to cause the freeze condition to be met, distortion in the first time slot due to movement may be discarded.

Thus, the method may comprise checking for additional criteria based on the time derivative of the first electrical impedance and the electrical impedance between the mobile sensor electrode and the mobile sensor return electrode.

An additional criterion is that the ratio of the time derivative of the first electrical impedance to the time derivative of the electrical impedance between the moving sensor electrode and the moving sensor return electrode is above a threshold value.

Ratio = impedance_change_freeze/impedance_change_move (equation 5)

If the ratio of equation 5 is above a certain threshold, this indicates that the first time derivative of the electrical impedance for freezing is significantly higher than the first time derivative of the electrical impedance for moving.

In some examples, the additional criteria may be determined (block 540) within the first time slot (i.e., the same time slot as the first and second freezing conditions). In other examples, the additional criteria may be determined after the first time slot.

Fig. 7 and 7A schematically illustrate signals of an impedance sensor and a method for evaluating such signals according to an example. In fig. 7, in the top part, the filtered signal for frozen impedance measurement (between the cooling element and the return electrode, reference numeral 600) and the filtered signal for moving impedance measurement (between the moving electrode and the corresponding electrode, reference numeral 610) are shown.

After applying the averaging filter and deriving the first time derivative, the results are shown with reference numerals 602 and 612, respectively, in the bottom of the figure. In fig. 7, two different time windows a and B have been identified, where a freeze event may be suspected. In particular, in window B, a specific "jump" or increase in electrical impedance may be identified.

The foregoing examples of fig. 4, 5 and 6 of the method for determining a freeze event may be applied to these three time windows as follows.

Fig. 7A shows the time window a in more detail. Reference numeral 620 indicates a threshold value of the first time derivative that varies with time. Referring to equations 1 to 3, the threshold may correspond to a minimum peak. It can be seen in fig. 7A that the resulting signal after application of the averaging filter allows to identify a specific increase more easily than the unfiltered signal. Referring to the example of fig. 6, for example, in the time window a, it may be found that the first freezing condition is satisfied, but it may be found that the second freezing condition is not satisfied. The result is that no freezing event is detected and the cooling treatment can continue normally.

In the time window B, it can be found that the first freezing condition and the second freezing condition are satisfied. At the same time, the movement sensor also indicates a peak value above the corresponding threshold value. That is, at block 530 of fig. 6, a possible movement is detected, because a significant increase in electrical impedance is also measured between the moving sensor electrode and the return electrode. Applying the example of fig. 6, the algorithm will go to block 540 and the first time derivatives of the two electrical impedances may be compared. In the case of time window B, the ratio as defined in equation 5 may be found to be satisfied and a conclusion may be drawn that a freezing event has occurred or is occurring.

The measurements of the electrical impedance sensors can also be used to determine the correct positioning of the applicator and skin folds. If the measurement of the sensor indicates an abnormal pattern, particularly at the beginning of the treatment, this may indicate that the applicator is not properly positioned, that the cryoprotectant pad is not properly positioned, or another problem, and thus that the user's skin is not adequately protected and/or that the cooling treatment will not be effective.

Examples of the methods disclosed herein may be implemented in hardware, software, firmware, and combinations thereof.

Those of skill would further appreciate that the various illustrative logical blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or combinations of both. To clearly illustrate this interchangeability of hardware and software, various illustrative components, blocks, modules, circuits, and steps have been described above generally in terms of their functionality. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the overall system. Skilled artisans may implement the described functionality in varying ways for each particular application.

The various illustrative logical blocks, modules, and circuits described in connection with the disclosure herein may be implemented or performed with one or more general purpose processors, digital Signal Processors (DSPs), cloud computing architectures, application Specific Integrated Circuits (ASICs), field Programmable Gate Arrays (FPGAs) or other programmable logic devices (PLCs), discrete gate or transistor logic, discrete hardware components, or any combinations thereof, designed to perform the functions described herein. A general purpose processor may be a microprocessor, but in the alternative, the processor may be any conventional processor, controller, microcontroller, or state machine. A processor may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

Various aspects of the disclosure are set forth in the following numbered clauses:

1. an applicator for a system for cooling a skin portion of a subject, the applicator comprising:

A cooling element having a cooling surface for contacting the skin portion of the subject to cool the skin portion of the subject,

Wherein the cooling element is electrically conductive and the cooling surface has a lower electrical conductivity than the remainder of the cooling element, wherein

The cooling system is configured to determine an electrical impedance between the cooling element and a first return electrode configured to be placed on a body of the subject.

2. The applicator of clause 1, wherein the cooling element is a metal contact plate, optionally an aluminum plate.

3. The applicator of clause 2, further comprising a thermoelectric cooler configured to cool the metal contact plate.

4. The applicator of clause 2 or 3, wherein the cooled surface is an anodized aluminum layer.

5. The applicator of any one of clauses 1-4, wherein the cooling surface is substantially non-conductive.

6. The applicator of clause 5, wherein the cooling surface comprises a non-conductive coating.

7. The applicator of any one of clauses 1 to 6, comprising a cable for providing electrical current to the cooling element, wherein the cable is attached to the cooling element with a screw.

8. The applicator of any one of clauses 1-7, comprising a cavity configured to receive a skin fold, wherein the cooling element is disposed within the cavity and configured to cool the skin fold.

9. The applicator of any one of clauses 1 to 8, wherein the current used to determine the electrical impedance is less than 35mA, specifically less than 1mA, more specifically 0.5mA or less.

10. The applicator of any one of clauses 1 to 9, comprising an accelerometer for measuring movement of the subject.

11. A cooling system for cooling a skin portion of a subject, the cooling system comprising a base station and one or more applicators according to any one of clauses 1-10, the applicators configured to be coupled to the base station.

12. The cooling system of clause 11, wherein the applicator is coupled to the base station with a flexible tube.

13. The cooling system of clause 12, wherein the flexible tube is configured to provide an electrical and/or electronic and/or pneumatic connection between the control base station and the applicator.

14. The cooling system of any one of clauses 11-13, wherein the first return electrode is configured to be placed on an extremity of the subject.

15. The cooling system of any one of clauses 11-14, further configured to determine a freezing of the skin of the subject based on the electrical impedance, in particular based on a change in the electrical impedance.

16. The cooling system of clause 15, wherein the cooling system is configured to determine the freezing of the skin based on a time derivative of the electrical impedance.

17. The cooling system of any one of clauses 11-16, wherein the cooling system is further configured to determine movement of the subject or movement of the skin portion relative to the cooling element.

18. The cooling system of clause 17, wherein the system is configured to determine the movement of the subject or the movement of the skin portion relative to the cooling element by determining an electrical impedance between a movement sensor electrode and a movement sensor return electrode.

19. The cooling system of clause 18, wherein the motion sensor return electrode is the first return electrode.

20. The cooling system of clause 18 or 19, wherein the motion sensor electrode is disposed on the applicator.

21. The cooling system of clause 20, wherein the motion sensor electrode is disposed near or about a cavity of the applicator configured to receive a skin fold.

22. The system according to claim 20 or 21, wherein the movement sensor electrode is attached to the applicator, in particular with an adhesive or a fastener.

23. A method for determining a freezing event during a cooling treatment, wherein a cooling element cools a skin portion of a subject, the method comprising:

Determining a first electrical impedance between the cooling element and a first return electrode placed on the subject,

Determining a time derivative of the determined first electrical impedance,

Determining movement using a mechanism for detecting movement, the movement comprising movement of the subject and/or movement of a skin portion of the subject relative to the cooling element,

The freezing event is determined if the time derivative of the first electrical impedance during a first time slot satisfies one or more freezing conditions and if distortion of the first electrical impedance caused by movement in the same time slot is discarded.

24. The method of clause 23, wherein the time derivative of the determined first electrical impedance is a second time derivative of the first electrical impedance.

25. The method of clause 23, wherein the time derivative of the determined first electrical impedance is a first order time derivative of the first electrical impedance.

26. The method of clause 25, wherein the first freezing condition is: the first time derivative of the first electrical impedance during a first time slot is above a first freezing threshold.

27. The method of clause 26, wherein the first freeze threshold is determined based at least in part on a measurement of the first time derivative.

28. The method of clause 27, wherein the first freezing threshold varies over time.

29. The method of any of claims 26 to 28, wherein a second freezing condition is that an integer value of a logarithmic value of the first time derivative is above a second freezing threshold during a second time slot, wherein the second time slot is longer than the first time slot.

30. The method of any of claims 26 to 29, wherein the first order time derivative is determined over a time window having a first span and a time window having a second span, the second span being longer than the first span.

31. The method of clause 30, wherein the third freezing condition is: the first time derivative determined over the first span during the first time slot is substantially different than the first time derivative measured over the second span.

32. The method of any of clauses 23-31, wherein distortion caused by movement in the first time slot is discarded if no indication of possible movement is derived from the means for detecting movement or if the possible movement derived from the means for detecting movement is insufficient to cause the freeze condition to be met.

33. The method of any of clauses 23-32, wherein detecting the possible movement comprises determining an electrical impedance between the movement sensor electrode and the movement sensor return electrode.

34. The method of clause 33, wherein the motion sensor return electrode is the first return electrode.

35. The method of clause 33 or 34, wherein if the first time derivative of the electrical impedance between the motion sensor electrode and the motion sensor return electrode during the first time slot is above a motion threshold, a possible motion is deduced.

36. The method of clause 35, wherein the movement threshold is determined based at least in part on the measure of the first time derivative.

37. The method of clause 36, wherein the movement threshold varies over time.

38. The method of any of clauses 35 to 37, further comprising checking additional criteria based on the time derivative of the first electrical impedance and the electrical impedance between the mobile sensor electrode and the mobile sensor return electrode.

39. The method of clause 38, wherein the additional criterion is that a ratio of a time derivative of the first electrical impedance to a time derivative of the electrical impedance between the mobile sensor electrode and the mobile sensor return electrode is above a threshold.

40. The method of clause 39, wherein the additional criteria is determined within the first time slot.

41. The method of clause 39, wherein the additional criteria is determined after the first time slot.

42. A method for reducing adipose tissue, in particular a cosmetic method for reducing adipose tissue, the method comprising:

Providing a cooling system according to any one of clauses 11 to 22;

Providing contact between a skin portion of the subject and a cooling element of the cooling system;

Cooling the skin portion of the subject during a period of up to 90 minutes; and

The method according to any one of clauses 23 to 41 being performed during said cooling.

43. The method of clause 42, wherein cooling the skin portion comprises: the temperature of the cooling element is controlled between 0 and-15 ℃, in particular between-5 ℃ and-13 ℃.

44. The method of clause 42 or 43, wherein if a freeze event is detected, the cooling of the skin portion is discontinued.

45. The method of any one of clauses 42 to 44, comprising: the cooling element is temporarily heated if a freeze event is detected.

46. The method of any of clauses 42 to 45, wherein an alert is generated if a freeze event is detected.

47. The method of any one of clauses 42 to 46, wherein the skin portion of the subject is one or more of the thigh, buttocks, abdomen, under chin tissue, knee, back, face, arm.

48. The method of any one of clauses 42 to 47, further comprising checking the proper operation of the cooling system by determining an electrical impedance between the cooling element and a first return electrode and/or by determining an electrical impedance between the moving electrode and the moving return electrode.

Although only a few examples have been disclosed herein, other alternatives, modifications, uses, and/or equivalents are possible. Moreover, all possible combinations of the described examples are also covered. Accordingly, the scope of the present disclosure should not be limited by the specific examples, but should be determined only by a fair reading of the claims that follow.

Claims (15)

1. A cooling system for reducing adipose tissue by cooling a skin portion of a subject, the cooling system comprising a base station and one or more applicators, the one or more applicators comprising:

A cooling element having a cooling surface for contacting the skin portion of the subject to cool the skin portion of the subject,

Wherein the cooling element is electrically conductive and the cooling surface is substantially non-conductive, wherein,

The cooling system is configured to determine freezing of the skin of the subject based on an electrical impedance between the cooling element and a first return electrode configured to be placed on a body of the subject.

2. The cooling system of claim 1, wherein the cooling element of the applicator is a metal contact plate, optionally an aluminum plate.

3. The cooling system of claim 2, wherein the cooling surface of the applicator is an anodized aluminum layer.

4. A cooling system according to any one of claims 1 to 3, wherein the current for determining the electrical impedance is less than 35mA, in particular less than 1mA, more in particular 0.5mA or less.

5. The cooling system of any one of claims 1 to 4, wherein the applicator is coupled to the base station with a flexible tube, and wherein the flexible tube is configured to provide an electrical and/or electronic and/or pneumatic connection between the base station and the applicator.

6. The cooling system of any one of claims 1 to 5, wherein the first return electrode is configured to be placed on an extremity of the subject.

7. The cooling system of any one of claims 1 to 6, configured to determine freezing of the skin of the subject based on a change in the electrical impedance.

8. The cooling system of claim 7, wherein the cooling system is configured to determine the freezing of the skin based on a time derivative of the electrical impedance.

9. The cooling system of any one of claims 1 to 7, wherein the cooling system is further configured to determine movement of the subject or movement of the skin portion relative to the cooling element.

10. The cooling system of claim 9, wherein the system is configured to determine movement of the subject or movement of the skin portion relative to the cooling element by determining an electrical impedance between a movement sensor electrode and a movement sensor return electrode.

11. The cooling system of any one of claims 1 to 10, configured to determine a freezing event during a cooling treatment by:

Determining a first electrical impedance between the cooling element and the first return electrode placed on the subject,

Determining a time derivative of the determined first electrical impedance,

Determining movement using a mechanism for detecting movement, the movement comprising movement of the subject and/or movement of a skin portion of the subject relative to the cooling element,

The freezing event is determined if the time derivative of the first electrical impedance satisfies one or more freezing conditions during a first time slot and if distortion of the first electrical impedance caused by movement in the same time slot is discarded.

12. The cooling system of claim 11, wherein the time derivative of the first electrical impedance is a first order time derivative, and wherein a first freezing condition is: the first time derivative of the first electrical impedance during a first time slot is above a first freezing threshold.

13. The cooling system of claim 12, wherein the first freezing threshold is determined based at least in part on a measurement of the first time derivative.

14. The cooling system of any one of claims 11 to 13, wherein distortion caused by movement in the first time slot is discarded if no indication of possible movement is derived from the means for detecting movement or if the possible movement derived from the means for detecting movement is insufficient to cause the freeze condition to be met.

15. The cooling system of claim 14, wherein the cooling system is configured to detect possible movement by determining an electrical impedance between a movement sensor electrode and a movement sensor return electrode, and optionally wherein the cooling system is configured to detect possible movement if a first time derivative of the electrical impedance between the movement sensor electrode and the movement sensor return electrode during the first time slot is above a movement threshold.