Method and system for determining skin freezing during cooling

Abstract

The present disclosure relates to an applicator, a cooling system including such an applicator, and a method for cooling treatment of a skin fold of a subject. A method for determining a freezing event includes measuring an electrical impedance between a contact plate of the applicator and a return electrode. The method also includes determining possible migration, which may also be based on the electrical impedance measurement.

Description

[Technical Field]

[0001] This application claims priority from European Patent Application No. 21382374.3, filed April 28, 2021.

[0002] The present disclosure relates to a method and system for determining a freezing event of skin during cooling. The present disclosure relates to an applicator of such a system and a method for determining a freezing event based on measuring electrical impedance.

[0003] The present disclosure also relates to methods and systems for treating a subject to locally reduce adipose tissue, particularly cosmetic treatment, and more particularly to methods and systems for locally reducing adipose tissue in a safe manner.

[0004] US2016 / 0045755 discloses systems and methods for use in fat reduction, which in some embodiments include an applicator with electrodes forming a capacitor for heating tissue.

[0005] US2012 / 0022518 discloses a system and method that allows delivery of radiofrequency and cryotherapy applications to adipose tissue for body fat reduction and contouring.

[0006] WO2007 / 093998 discloses a method and apparatus for the treatment of adipose tissue. The method comprises applying ultrasound energy to a region of adipose tissue. In one embodiment, an RF field is generated within the region of adipose tissue together with the ultrasound energy.

[0007] US2002 / 0049483 discloses a fluid delivery apparatus for introducing a fluid cooling medium to a skin surface, which includes a template having a skin interface. An energy delivery device is coupled to the template. [Background technology]

[0008] background Liposuction has been practiced for many years to reduce a patient's excess body fat. A much less invasive treatment aimed at locally reducing adipose tissue by applying cold to a subject's skin folds has also been commercially available for many years. It has been found that subcutaneous adipose tissue is 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 undamaged or minimally damaged. Over time, the lipid-rich cells die and disappear through the natural apoptotic process. This allows for the provision of a cosmetic treatment for locally reducing fat.

[0009] For this type of cryotherapy, treatment devices are known that have one or more applicators containing a cavity. Suction can be applied to the cavity to suck in the subject's skin folds. One or more thermally conductive (metallic) contact plates may be provided inside the cavity. Thermoelectric cooling elements (Peltier elements) can be used to cool the plates to low temperatures. Although thermoelectric cooling elements are the most widely used, alternative cooling methods can also be used, for example, based on cryogenic fluids cooling conductive plates.

[0010] The contact plate may be substantially straight. One or more contact plates may be provided within the cavity of the applicator. A single curved contact plate or multiple curved contact plates that conform to the area of ​​the subject's body may also be used.

[0011] Some form of temperature control is usually provided to control the temperature of the contact plates, and thus the temperature of the skin. In some known devices, the temperature of the skin may be measured during treatment. Alternatively, in other known devices, the temperature of the conductive plates is measured during treatment.

[0012] By suctioning the skin folds, improved contact between the skin and the cooling element (e.g., metal contact plates) is achieved. Furthermore, squeezing the skin folds between the metal plates can reduce local blood flow, thus reducing heat supply to the area and making cooling more effective. Applicators that do not rely on suctioning the skin folds are also known.

[0013] The risk of severe and painful injury to patients is associated with freezing of the skin or the formation of crystals within the skin during such treatment. It is known that at temperatures below about 0°C, freezing of the skin can occur depending on the duration of exposure.

[0014] To avoid freezing of the skin, the use of cryoprotectants is known. Cryoprotectants are substances that can be used to protect biological tissues from freezing damage (i.e., due to the formation of large ice crystals).

[0015] One of the challenges associated with the use of cryoprotectants in such cryotherapy relates to effectively protecting the skin with the cryoprotectant. For cryotherapy to be effective, the treatment may involve applying temperatures of -5°C or below, e.g., -10°C or below, to the metal plate for an extended period of time, e.g., more than 30 minutes, more particularly, more than 45 minutes, or even more than 1 hour.

[0016] US 7,367,341 relates to a method for selective destruction of lipid-rich cells by controlled cooling. Feedback mechanisms used in these methods to monitor and control skin temperature are described. Such feedback mechanisms may include, for example, invasive thermocouples for local temperature measurement. Ultrasound imaging, acoustic, optical, and mechanical measurements are also mentioned for monitoring crystal formation. Electrical feedback devices may be used to monitor changes in the electrical impedance of the epidermis caused by ice formation within the epidermis. These monitoring systems are not described in detail beyond the invasive temperature measurement.

[0017] WO2009 / 026471 discloses a system for monitoring or detecting an event during heat removal from subcutaneous lipid-rich tissue. In some embodiments, the system detects an increase in temperature at a treatment device in contact with the subject's skin, determines that the increase in temperature is associated with a treatment event, and performs an action based on the determination. In some embodiments, the system shuts off the treatment device, alerts an operator, or reduces cooling in response to the determined treatment event.

[0018] One drawback associated with some of these prior art systems is that they are complex and therefore costly to integrate into a system for localized adipose tissue reduction. Another drawback 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 immediately adjacent to the probe or sensor, the freezing may not be detected until it spreads. If freezing is detected, damage may already have occurred. Summary of the Invention [Problem to be solved by the invention]

[0019] There remains a need for devices that can provide safe and effective treatment of the skin and that can avoid or mitigate one or more of the aforementioned problems. [Means for solving the problem]

[0020] overview 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 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 is configured to determine an electrical impedance between the cooling element and a first return electrode configured to be placed on the body of the subject.

[0021] In the applicator according to this embodiment, electrical impedance may be used to determine a freeze event. In the applicator according to this embodiment, electrical impedance is measured between a substantial portion of the cooling surface and the first return electrode, rather than the point-by-point measurement known from the prior art. Therefore, determination of a freeze event may be more reliable than in the prior art.

[0022] Lower conductivity means that the conductivity of the surface is at least 30%, specifically at least 50%, lower than the conductivity of the cooling element. In certain embodiments, the surface of the cooling element may be substantially non-conductive. Substantially non-conductive as used throughout this disclosure may be understood to mean an electrical resistivity of 1,000 Ω-cm or greater, specifically 10,000 Ω-cm or greater.

[0023] In some embodiments, the cooling element can be a metal contact plate, optionally an aluminum plate with an anodized aluminum layer as the cooling surface. Aluminum has high thermal conductivity and therefore makes an effective and efficient cooling element. Anodized aluminum can be provided relatively easily. Its electrical properties vary depending on its composition, but can be, for example, 10 9 Ω.cm or more, even 10 11 It can have a high electrical resistivity of Ω·cm or more.

[0024] In some embodiments, an electrical cable for providing electrical current to the cooling element, the electrical cable being attached to the cooling element with screws.

[0025] In some embodiments, the current for determining the electrical impedance is less than 35 mA, specifically less than 1 mA, and more specifically 0.5 mA or less. Because very little current can be used to measure the electrical impedance, it does not adversely affect the user experience during cooling therapy.

[0026] In some embodiments, the applicator may include an accelerometer for measuring the subject's movements. In other embodiments, electrical impedance between other electrodes may be used to determine the potential movements of the subject or of the applicator relative to the subject's skin folds.

[0027] In a further aspect, there is provided a cooling system for cooling a skin portion of a subject, comprising a base station and one or more applicators according to any of the embodiments disclosed herein. The applicators are configured to be coupled to the base station, optionally via flexible tubing. In embodiments, such flexible tubing may be configured to provide an electrical and / or electronic and / or pneumatic connection between the control base station and the applicators.

[0028] The control circuitry, power supply, and pneumatic system may be provided within the base station. The applicators may be controlled from the base station. Measurements (e.g., temperature, impedance) may be taken at the applicators and provided to the base station. In an embodiment, some of the control circuitry may be provided in each applicator.

[0029] In some embodiments, the first return electrode is configured to be placed on the subject's extremity. A certain distance between the cooling element and the return electrode is beneficial to improve electrical impedance measurements. The subject's arms and legs may be suitable for this purpose, particularly when cooling treatment is administered to the abdomen, submental tissue, or buttocks.

[0030] In some examples, the cooling system may be further configured to determine freezing of the subject's skin based on electrical impedance, particularly based on variations in electrical impedance. When the freezing event is determined based on electrical impedance, the applicator does not require a specific additional auxiliary system for measuring movement.

[0031] In some examples, the cooling system may be further configured to determine skin freezing based on the time derivative of the electrical impedance. Variations in electrical impedance (and specifically the time derivative) have been found to be a better indicator of a freezing event than the absolute value of the measured electrical impedance.

[0032] Separate from the freezing event, movement may also be determined using electrical impedance. When both movement and freezing events are measured using the same electrical parameter, systems or components can be combined to integrate different functions, reducing complexity and reducing independent system failures. The system may be configured to determine movement of the subject or movement of the skin portion relative to the cooling element by determining the electrical impedance between the movement sensor electrode and the movement sensor return electrode. Optionally, the movement sensor return electrode may be the first return electrode, i.e., the same electrode used to measure the freezing event.

[0033] The movement sensor electrodes may be positioned near or around a cavity in the applicator configured to receive the skin fold so that movement of the applicator relative to the skin fold can be measured by both systems. Alternatively, if only the system with the cooling element measures an event of interest and the other system for detecting movement does not, the likelihood of a real event increases. In this way, both false negatives and false positives may be reduced.

[0034] In a further aspect, a method for determining a freezing event during cooling therapy is provided. A cooling element cools a skin portion of a subject during cooling therapy. 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 includes determining movement, including movement of the subject relative to the cooling element and / or movement of the skin portion of the subject, using a mechanism for detecting movement. The method includes determining a freezing event when the time derivative of the first electrical impedance satisfies one or more freezing conditions during a first time slot, and distortions of the first electrical impedance due to movement within the same time slot are discarded, thereby determining a freezing event.

[0035] To reduce false positives, two or more freezing conditions may be established. Two or more criteria for determining possible migration may be established to reduce false negatives.

[0036] The time derivative may be understood as the derivative of a function (in this case the measured first electrical impedance) with respect to time. The time derivative of the determined first electrical impedance may in particular be a first or second time derivative.

[0037] Distortion due to movement in the first time slot may be discarded if no indication of possible movement is derived from the mechanism for detecting movement, or if the possible movement derived from the mechanism for detecting movement is not sufficient to cause a freeze condition to occur.

[0038] Throughout this disclosure, a "first time derivative" may be understood as a first order time derivative, i.e., it represents the rate of change of a variable with respect to time. Throughout this disclosure, "first time derivative," "first time derivative," and "first order derivative" may be used interchangeably.

[0039] In yet a further aspect, a method of reducing adipose tissue, particularly a cosmetic method for reducing adipose tissue, is provided. The method includes providing a cooling system according to any of the embodiments disclosed herein, providing contact between a skin portion of a subject and a cooling element of the cooling system, and cooling the skin portion of the subject for a period of time, e.g., up to 70 minutes, 90 minutes, 120 minutes, or more. The method also includes performing a method of determining a freezing event as disclosed herein during cooling.

[0040] In embodiments, cooling of the skin portion may be discontinued if a freezing event is detected and / or an alarm may be generated and / or temporary heating (instead of cooling) may be performed to avoid damage to the subject's skin.

[0041] In embodiments, the method may further include checking correct function of the cooling system by determining the electrical impedance between the cooling element and the first return electrode and / or by determining the electrical impedance between the moving electrode and the moving return electrode. If proper contact with the skin is provided, the electrical impedance is within an expected range. Such measurements may be used during, at, or even before the initiation of cooling therapy to determine that the skin folds are in contact with the contact plates. If cryoprotectant pads are used, proper placement of the cryoprotectant pads may also be checked by measuring the electrical impedance.

[0042] Throughout this disclosure, the term "skin," when used in connection with a freezing event, can refer to the dermis, the epidermis, or both. [Brief explanation of the drawings]

[0043] Non-limiting examples of the present disclosure are described below with reference to the accompanying drawings.

[0044] [Figure 1] 1 illustrates a schematic representation of an embodiment of a cooling system. [Figure 2A]1A and 1B illustrate schematic diagrams of an embodiment of an applicator and a cooling system including such an applicator. [Figure 2B] 1A and 1B illustrate schematic diagrams of an embodiment of an applicator and a cooling system including such an applicator. [Figure 3] 1 illustrates a schematic diagram of a method for reducing adipose tissue according to an embodiment. [Figure 4] 1 illustrates a schematic diagram of a method for determining a freezing event during cooling therapy, according to an embodiment. [Figure 5] 10 illustrates, in schematic form, a further embodiment of a method for determining a freezing event during cold therapy. [Figure 6] 10 illustrates, in schematic form, a further embodiment of a method for determining a freezing event during cold therapy. [Figure 7] 1 illustrates a schematic representation of an impedance sensor signal and a method for evaluating such a signal according to an embodiment; [Figure 7A] 1 illustrates a schematic representation of an impedance sensor signal and a method for evaluating such a signal according to an embodiment; DETAILED DESCRIPTION OF THE INVENTION

[0045] FIG. 1 shows a schematic representation of an embodiment of a cooling system that may be used in methods for reducing adipose tissue, particularly cosmetic methods for reducing adipose tissue.

[0046] The method may include providing a cooling system as shown in Figure 1. The cooling system of Figure 1 includes a base station 100 and one or more applicators 110, 120. The base station may include a user interface 150 including a screen that may show information related to the cooling treatment.

[0047] The user interface 150 may include a tactile screen, and / or one or more control buttons or handles may be used to adjust a suitable cooling treatment and / or parameters for the cooling treatment.

[0048] The applicators 110, 120 may each be connected to a base station via a flexible tube or hose 105, 115. Such flexible tubes 105, 115 may be configured to provide an electrical and / or electronic and / or pneumatic connection between the base station and the applicator.

[0049] The base station may have a power source, for example an electrical cable with a plug.

[0050] The applicator may have different sizes and shapes adapted to cool different parts of the subject's body. In a method of reducing adipose tissue, a fold of the subject's skin may be introduced into a cavity of the applicator, and a portion of the subject's skin may be brought into contact with the cooling element of the applicator.

[0051] Cooling treatment can involve cooling an area of ​​a subject's skin for a period of up to 90 minutes, with duration and other settings (e.g., temperature) varying depending on the area of ​​skin being cooled and the goal of the treatment.

[0052] In an embodiment, cooling the skin portion includes controlling the temperature of the cooling element to between 0 and -15°C, specifically between -5 and -13°C. The skin portion of the subject may be one or more of the thigh, buttocks, abdomen, submental tissue, knee, back, face, and arm. The cooling system may include multiple applicators to simultaneously treat multiple skin folds.

[0053] At temperatures below 0°C for extended periods, freezing of the skin may occur. To avoid such freezing, pads or absorbents with cryoprotectants may be used. Cryoprotectants may be provided between the skin and the cooling element to protect the skin.

[0054] In embodiments of the present disclosure, a method for determining a freezing event may be performed continuously throughout the cooling treatment. If a freezing event is detected, the cooling treatment may be interrupted or otherwise modified to avoid damage or injury to the subject's skin. If a freezing event is detected, cooling of the skin portion may be discontinued. In embodiments, the method may include temporarily heating the cooling element if a freezing event is detected. In embodiments, an audible or visual alarm may be generated if a freezing event is detected so that an operator can intervene by manually modifying the treatment, interrupting the treatment, disconnecting the base station, etc.

[0055] 2A and 2B schematically illustrate an embodiment of an applicator 10 and cooling system for treating skin folds on a subject 90. Similar to the embodiment of FIG. 1, the cooling system of FIG. 2B may include a base station 100 having a user interface 150 and multiple applicators 110, 120, 160. The applicators may be similar to the applicator 10 shown in FIG. 2A.

[0056] The applicator 10 may include a cavity 2 for receiving a skin fold. An orifice connected to a suction system may be provided at the bottom of the cavity 2. A pump and power source for drawing the skin fold into the applicator may be incorporated into the base station. A flexible tube or hose 5 may connect the applicator 10 to a corresponding base station. The applicator 10 may include a suitable coupling for connecting 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 disposed within the cavity.

[0057] Depending on the skin fold to be treated, the applicator may include one or more linear contact plates, e.g., two contact plates positioned on opposite sides of the cavity. In other embodiments, a single contact plate may be curved and / or shaped like a cup.

[0058] The applicator 10 for the system for cooling a skin portion of a subject includes 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.

[0059] The cooling element 3 may be a metal contact plate, optionally an aluminum plate. The aluminum plate may have relatively good thermal conductivity. The applicator may further comprise 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 element, the temperature of the contact plate, and therefore the cooling of the skin fold, can be controlled. A temperature sensor may be placed in contact with the skin, or alternatively, may measure the temperature of the contact plate or the Peltier element.

[0060] The cooling surface may be substantially electrically non-conductive. The higher resistivity of the cooling surface means that the entire contact plate may function as an electrode for impedance measurements. The cooling surface may include an electrically non-conductive coating. The cooling surface may be an anodized aluminum layer.

[0061] The applicator 10 may include an electrical cable for providing current to the cooling element, the electrical cable being attached to the cooling element with a screw. The current for determining the electrical impedance may be less than 35 mA, specifically less than 1 mA, and more specifically 0.5 mA or less.

[0062] The applicator 10 may further include a mechanism for determining movement. Movement may include movement of the applicator, movement of a skin fold relative to the applicator, or movement of the subject. Such movement may affect electrical impedance measurements and, therefore, the reliability of the determination of a freezing event.

[0063] In some embodiments, the applicator 10 may include an accelerometer for measuring the subject's movement. In other embodiments, additional impedance measurements may be used to detect movement.

[0064] In some embodiments, the first return electrode 190 may be configured to be placed on the extremity of the subject, and the electrical impedance between the contact plate 3 and the first return electrode 190 may be measured to determine possible freezing of the skin.

[0065] The cooling system may be configured to determine freezing of the subject's skin based on electrical impedance, in particular, by receiving a signal related to the electrical impedance from the applicator and analyzing the signal based on variations in electrical impedance.

[0066] In an embodiment, the cooling system may be configured to determine skin freezing based on the time derivative of electrical impedance. In particular, it has been found that variations in electrical impedance can be a reliable indicator of a freezing event.

[0067] In an embodiment, 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 electrical impedance between the moving sensor electrode 14 (in FIG. 2A) and the moving sensor return electrode. In FIG. 2B, the moving sensor electrode 14 is integrated into the applicator. The moving 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 embodiment, a kit may be provided that can upgrade or retrofit the applicator with a suitable system for measuring electrical impedance to determine possible freezing.

[0068] In an alternative embodiment, the movement sensor electrode 180 may be separate from the applicator.

[0069] In an embodiment, the travel sensor return electrode may be first return electrode 190, ie, the same return electrode used in combination with the contact plate.

[0070] 3 schematically illustrates a method of reducing adipose tissue according to an embodiment. In any of the embodiments disclosed herein, the skin folds to be treated may be in one of the following areas of a subject: thighs, buttocks, abdomen, submental tissue, knees, back, face, and arms. In any of the embodiments disclosed herein, several skin folds may be treated simultaneously. For example, a single treatment device may include two or more applicators, and the applicators may be applied to different skin folds simultaneously.

[0071] In block 210, a configuration for cooling may be determined. The configuration may depend, among other things, on which body part is being treated. In particular, a cooling temperature and a cooling time may be configured. The cooling temperature may be related to the temperature of the subject's body in the treated area (e.g., the temperature measured at the epidermis) or the temperature of the cooling element.

[0072] In embodiments, the contact plate of the treatment device may be maintained at a temperature below 0°C, more specifically below -5°C, for 15 to 90 minutes. In particular, the contact plate may be maintained in contact with the skin for 20 to 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 the treatment time for other areas of the skin may be, for example, 60 to 75 minutes.

[0073] In some embodiments, the base station of the cooling system may have several pre-defined stored cooling programs. The operator may simply select the selected treatment or body part to be treated. Alternatively, the base station may be able to determine which applicator is active or connected to the base station. If an applicator can only be used in a single area, the base station may automatically recognize the area or body part being treated and automatically select the appropriate configuration accordingly. Alternatively, the base station may recognize the applicator, but the operator indicates (e.g., selects on the base station) which specific area, zone, or body part is to be treated from the different areas or zones that can be treated with a particular applicator.

[0074] The skin fold may be introduced into the applicator. A cryoprotectant may be disposed between the skin fold and the contact plate within the applicator. In block 220, the skin fold may be specifically cooled to cool the adipose tissue and locally reduce fat.

[0075] During cooling therapy, continuous monitoring may be performed to detect a freeze event in block 230. If such a freeze event is detected in block 230, the freeze may be mitigated in block 240 in any of a variety of ways as commented herein, including disconnecting the cooling system, (temporarily) warming up the contact plates, shutting down the cooling system, and others.

[0076] 4 schematically illustrates a method for determining a freezing event during cooling therapy according to an embodiment. During cooling therapy, impedance may be measured substantially continuously. Measuring impedance in block 310 means measuring electrical impedance between the metal contact plate and the first return electrode. Measuring impedance may be performed, for example, at a frequency between 1 kHz and 1000 kHz, specifically between 10 kHz and 200 kHz.

[0077] At block 320, a possible freezing event of the user's skin can be determined based on the measured impedance. If the electrical impedance occurs in a way that does not suggest a freezing event, the flow diagram proceeds to block 340 and the conclusion is that there is no freezing event. It should be clear that the method is continuous, i.e., measuring impedance can be performed continuously and therefore continuous conclusions regarding freezing can be reached.

[0078] If a possible freeze event is detected in block 320, a determination may be made whether there is possible movement in block 350. In an embodiment, movement may be continuously measured in block 330. If the electrical impedance measured in block 310 occurs in such a way that freezing is detected, and at the same time no movement is detected, a conclusion may be reached that there is a freeze event in block 360. The reason for checking for possible movement is to reduce false positives, as movement can cause impedance changes similar to a freeze event.

[0079] According to this embodiment, possible movement may be measured continuously, but an assessment of possible movement is only made if a freezing event is suspected.

[0080] An alternative embodiment is shown in Figure 5. As in Figure 4, movement and electrical impedance may be continuously measured between the cooling element and a first return electrode placed on the subject (blocks 310, 330). Movement may be measured by determining the electrical impedance between the movement sensor electrode and the movement sensor return electrode. The movement sensor return electrode may be the first return electrode.

[0081] Independently of each other and consecutively, possible frozen elements may be detected and possible movements may be detected (blocks 320, 340).

[0082] Unless a freeze event is suspected, a conclusion is reached in block 340 that a freeze event does not exist and therefore there is no reason to interrupt or modify the cooling therapy. If a freeze event is suspected, a verification is made as to whether movement may have affected the determination of the freeze event. At the same time, if a freeze element is suspected and a determination is made that movement cannot cause it, a conclusion is reached in block 360 that a freeze event has occurred or is occurring.

[0083] In the embodiment of Figure 5, an additional block 370 is introduced. If a freeze event is suspected and migration is also suspected, a further check is made to determine whether there is an actual freeze event. In block 370, a further evaluation may be made by comparing the occurrence or variation of the electrical impedance measured for migration detection with the electrical impedance measured to determine the freeze event. If a freeze event occurs, the electrical impedance may increase in both measurements, but more significantly between the cooling element and the return electrode.

[0084] In either of the embodiments of Figures 4 and 5, a freeze event may be suspected if one or more freeze conditions are met for the electrical impedance.

[0085] In any of the embodiments, a method for determining a freezing event during cooling therapy in which a cooling element cools a skin portion of a subject includes determining a first electrical impedance between the cooling element and a first return electrode placed on the subject (block 310) and determining a time derivative of the determined first electrical impedance.

[0086] In particular, the first time derivative may be used, which indicates the rate of change of the first electrical impedance and has been found to be reliably indicative of a possible freezing event if the first time derivative exceeds a threshold value.

[0087] In other examples, the second time derivative may be used. The second time derivative indicates an acceleration of the first electrical impedance. Outliers in the second time derivative over time may also indicate a possible freezing event. In one example, the absolute value of the second time derivative may be compared to a threshold value.

[0088] The method may further include determining movement (block 320), including movement of the subject and / or movement of the subject's skin portion relative to the cooling element, using a mechanism for detecting movement.

[0089] A freeze event may be determined when the first time derivative of the first electrical impedance satisfies one or more freeze conditions during the first time slot and distortion of the first electrical impedance due to movement within the same time slot is discarded, where the first freeze condition is when the first time derivative of the first electrical impedance exceeds a first freeze threshold during the first time slot.

[0090] In some embodiments, the first freezing threshold is determined based at least in part on a measurement of the first time derivative. In embodiments, the first freezing threshold may vary over time.

[0091] A further example is shown in Figure 6. In block 405, a signal related to the electrical impedance between the cooling element and the first return electrode may be received. In block 410, a filter may be applied to the received signal. In particular, an averaging filter may be applied, for example, where a number of individual measurement points are summed, averaged, and correlated to a single measurement time (the center of the averaged measurement points).

[0092] In an embodiment, impedance measurements may be performed at frequencies between 1 kHz and 1,000 kHz, specifically between 50 and 200 kHz, and more specifically at about 100 kHz.

[0093] The sampling time of the averaging filter may be 0.1 seconds to several seconds, specifically 0.5 seconds to 2.5 seconds.

[0094] Similarly, a signal related to the electrical impedance between the moving sensor electrode and the moving return electrode is received in block 505. A similar averaging filter may be applied in block 510. The measurement frequency and averaging may be the same or of the same order of magnitude for the moving impedance measurements and the impedance measurements for detecting potential freeze events.

[0095] After filtering, the time derivatives, particularly the first time derivatives, of both measurements may be determined in blocks 415, 515. In blocks 430 and 440, multiple freezing conditions may be defined for the first time derivative of the electrical impedance.

[0096] The first freezing condition (block 430) may be that the first time derivative of the first electrical impedance exceeds a first freezing threshold or is between a predetermined first freezing threshold values ​​during the first time slot. Thus, the freezing threshold value corresponds to a value of the rate of change of the electrical impedance. In some embodiments, the first freezing threshold value may vary over time. Optionally, an average value of two or more moments in time may be compared to the threshold value, rather than individual values ​​of the first time derivative.

[0097] In one embodiment, Impedance_variation = (current impedance variation - last impedance variation) / 2 (Equation 1) Peak=impedance_variation / first_threshold_value (Formula 2) First_threshold_value=(fixed_threshold*gain_threshold)+(abs[impedance_variation]*gain_impedance) (Formula 3)

[0098] Equation 1 represents the average over two time slots of the first time derivative of the electrical impedance. Equation 2 defines the peak value as the ratio between the first time derivative of the electrical impedance and a threshold. If the peak is at a predetermined level, a freezing event can be detected. If the peak is low, the electrical impedance fluctuation is too low and freezing is unlikely to occur. If the peak is too high, a freezing event is unlikely because there must be another cause of very rapid fluctuations in electrical impedance (e.g., loss of contact between the skin and the cooling element or the like). Equation 3 shows how the first threshold may change over time, taking into account measurements from specific components in a specific cooling treatment.

[0099] A second freezing condition may be defined in block 440. The second freezing condition in this example is that the integral of the (natural) logarithm of the first time derivative during a second time slot exceeds a second freezing threshold, and the second time slot is longer than the first time slot. Ln_value=Σ(ln(peak) / second time slot(Formula 4)

[0100] The second time slot may be longer than the first time slot. The first time slot (for first time derivative) may be 1 to 5 seconds, specifically 1 to 4 seconds. The second time slot may be longer. In one embodiment, the second time slot may be 5 seconds.

[0101] If both the first and second freezing conditions are met, the algorithm proceeds to block 450 or block 540, as described below. If any one of the freezing conditions is not met, a conclusion is drawn in block 490 that freezing has not occurred.

[0102] Simultaneously, the first time derivative of the electrical impedance between the moving sensor electrode and the return electrode may be determined in block 515, and in block 530, a first movement criterion may be defined.

[0103] If the 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 or between predetermined movement thresholds, possible movement may be derived (block 530). In block 530, similar equations 1-3 may be applied to the signal associated with the movement sensor. The motion threshold may be determined based at least in part on a measurement of the first time derivative. The first motion threshold may vary over time.

[0104] If no movement is determined or suspected in block 530 and freezing is suspected in blocks 430 and 440, a third freezing condition may be checked in block 450.

[0105] In an embodiment, the first time derivative (particularly the electrical impedance between the cooling element and the return electrode) may be determined over a time window having a first span and over 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, while a second averaging filter based on 64 measurement points may be applied. It should be clear that 32 and 64 are mentioned merely as examples. In an embodiment, a "Haar" filter is used.

[0106] A third freeze condition in block 450 may be defined by the first time differential determined over a first span (in this example, an averaging filter with 32 points) during the first time slot being substantially different from the first time differential measured over a second span (an averaging filter with 64 points). If freeze-up occurs, the first time differential using the averaging filter over a shorter time span will be different from the first time differential using the averaging filter over a longer time span. If, instead, the averages are not significantly different, the third freeze condition is not met and a conclusion is reached in block 490 that there is no freeze event.

[0107] If the first and second freeze conditions are met at blocks 430, 440 and the movement criterion is met at block 530, it may be further determined whether movement has distorted the electrical impedance measurements.

[0108] In an embodiment, distortion due to movement in the first time slot may be discarded if no indication of possible movement is derived from the mechanism for detecting movement, or if the possible movement derived from the mechanism for detecting movement is not sufficient to cause a freeze condition to be established.

[0109] Thus, the method may include checking additional criteria based on the time derivative of the first electrical impedance and the electrical impedance between the moving sensor electrode and the moving sensor return electrode.

[0110] 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 greater than a threshold value. Ratio=Impedance_variation_freezing / impedance_variation_movement (Formula 5)

[0111] 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 locomotion.

[0112] In some embodiments, the additional criteria may be determined for the first time slot, i.e., the same time slot as the first and second freezing conditions (block 540). In other embodiments, the additional criteria may be determined after the first time slot.

[0113] 7 and 7A show schematic diagrams of impedance sensor signals and methods for evaluating such signals according to embodiments. In Fig. 7, at the top, filtered signals of impedance measurements for freezing (between the cooling element and the return electrode, reference number 600) and transfer (between the transfer electrode and the corresponding electrode, reference number 610) are shown.

[0114] After applying the averaging filter and the derived first time derivative, the results are shown at the bottom of the figure with reference numerals 602 and 612, respectively. In Figure 7, two different time windows, A and B, in which a freezing event may be suspected are identified. In particular, in window B, a particular "jump" or increase in electrical impedance may be recognized.

[0115] The above-described embodiment of FIGS. 4, 5, and 6 of a method for determining a freeze event can be applied to these three time windows as follows.

[0116] FIG. 7A shows time window A in more detail. Reference numeral 620 denotes a threshold value of the first time derivative that varies over time. Referring to Equations 1-3, the threshold value may correspond to the minimum peak value. In FIG. 7A, it can be seen that the resulting signal after applying the averaging filter allows for easier identification of specific increases than the unfiltered signal. For example, referring to the example of FIG. 6, it can be seen that in time window A, the first freezing condition is met, but the second freezing condition is not. As a result, the freezing event may not be detected, and cooling therapy may continue normally.

[0117] In time window B, the first and second freezing conditions may be found to be satisfied. At the same time, the movement sensor also exhibits peaks above the corresponding thresholds. That is, in block 530 of FIG. 6, a sufficient increase in electrical impedance is also measured between the movement sensor electrode and the return electrode, and thus possible movement is detected. Applying the embodiment of FIG. 6, the algorithm may proceed to block 540, where a comparison of the first time derivatives of both electrical impedances may be performed. For time window B, the ratio defined in Equation 5 may be found to be satisfied, and a conclusion may be reached that a freezing event has occurred or is occurring.

[0118] Electrical impedance sensor measurements can also be used to determine correct positioning of the applicator and skin fold. If the sensor measurements show an abnormal pattern, especially at the beginning of treatment, this may indicate that the applicator is not placed correctly, that the anti-freeze pad is not properly placed, or another problem, and therefore that the user's skin is not being properly protected and / or the cooling treatment is not effective.

[0119] Embodiments of the methods disclosed herein may be implemented in hardware, software, firmware, and combinations thereof.

[0120] Those skilled in the art will further appreciate that the various illustrative logic blocks, modules, circuits, and algorithm steps described in connection with the disclosure herein may be implemented as electronic hardware, computer software, or a combination 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 on the particular application and design constraints imposed on the overall system. Those skilled in the art may implement the described functionality in various ways for each particular application.

[0121] The various illustrative logic 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 combination thereof, designed to perform the functions described herein. A general-purpose processor may be a microprocessor, but alternatively, 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, multiple microprocessors, one or more microprocessors in conjunction with a DSP core, or any other such configuration.

[0122] Various aspects of the disclosure are set forth in the following numbered clauses. Clause 1. An applicator for a system for cooling a skin portion of a subject, comprising: an 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; the cooling element is electrically conductive, the cooling surface having a lower electrical conductivity than the remainder of the cooling element; The applicator, 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 the subject's body. Clause 2. The applicator of clause 1, wherein the cooling element is a metal contact plate, optionally an aluminum plate. Clause 3. The applicator of clause 2, further comprising a thermoelectric cooler configured to cool the metal contact plate. Clause 4. The applicator of clause 2 or 3, wherein the cooling surface is an anodized aluminum layer. Clause 5. An applicator according to any one of clauses 1 to 4, wherein the cooling surface is substantially non-conductive. Clause 6. The applicator of clause 5, wherein the cooling surface comprises an electrically non-conductive coating. Clause 7. An applicator according to any one of clauses 1 to 6, comprising an electrical cable for providing current to the cooling element, the electrical cable being attached to the cooling element by screws. Clause 8. An applicator described in any one of clauses 1 to 7, comprising a cavity configured to receive a skin fold, a cooling element disposed within the cavity and configured to cool the skin fold. Clause 9. The applicator of any one of clauses 1 to 8, wherein the current for determining the electrical impedance is less than 35 mA, specifically less than 1 mA, more specifically 0.5 mA or less. Clause 10. An applicator according to any one of clauses 1 to 9, comprising an accelerometer for measuring the movement of the subject. Clause 11. A cooling system for cooling a portion of a subject's skin, comprising a base station and one or more applicators according to any one of clauses 1 to 10 configured to be coupled to the base station. Clause 12. The cooling system of clause 11, wherein the applicator is coupled to the base station by a flexible tube. Clause 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. Clause 14. A cooling system described in any one of clauses 11 to 13, wherein the first return electrode is configured to be placed on an extremity of the subject. Clause 15. A cooling system according to any one of clauses 11 to 14, further configured to determine freezing of the subject's skin based on electrical impedance, in particular based on variations in electrical impedance. Clause 16. The cooling system of clause 15, wherein the cooling system is further configured to determine skin freezing based on a time derivative of the electrical impedance. Clause 17. A cooling system according to any one of clauses 11 to 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. Clause 18. A cooling system as described in clause 17, wherein the system is configured to determine movement of the subject or movement of the skin portion relative to the cooling element by determining electrical impedance between the moving sensor electrode and the moving sensor return electrode. Clause 19. The cooling system of clause 18, wherein the moving sensor return electrode is the first return electrode. Clause 20. A cooling system according to clause 18 or 19, wherein the moving sensor electrode is disposed on the applicator. Clause 21. The cooling system of clause 20, wherein the moving sensor electrode is positioned near or around a cavity in the applicator configured to receive a skin fold. Clause 22. A system according to claim 20 or 21, wherein the moving sensor electrode is attached to the applicator, in particular by means of an adhesive or fasteners. Clause 23. A method for determining a freezing event during cooling therapy, comprising: a cooling element cooling a skin portion of a subject; and the method comprising: determining a first electrical impedance between the cooling element and a first return electrode disposed on the subject; determining a time derivative of the determined first electrical impedance; determining movement, including movement of the subject and / or movement of the skin portion of the subject relative to the cooling element, using a mechanism for detecting movement; determining a freezing event if a time derivative of the first electrical impedance satisfies one or more freezing conditions during the first time slot and distortion of the first electrical impedance due to movement within the same time slot is discarded. Clause 24. The method of clause 23, wherein the determined time derivative of the first electrical impedance is a second time derivative of the first electrical impedance. Clause 25. The method of clause 23, wherein the determined time derivative of the first electrical impedance is a first time derivative of the first electrical impedance. Clause 26. The method of clause 25, wherein the first freezing condition is that the first time derivative of the first electrical impedance exceeds a first freezing threshold during the first time slot. Clause 27. The method of clause 26, wherein the first freezing threshold is determined based at least in part on a measurement of the first time derivative. Clause 28. The method of clause 27, wherein the first freezing threshold varies over time. Clause 29. A method according to any one of claims 26 to 28, wherein the second freezing condition is that the integral of the logarithm of the first time derivative during a second time slot exceeds a second freezing threshold, the second time slot being longer than the first time slot. Clause 30. A method according to any one of claims 26 to 29, wherein the first time derivative is determined over a time window having a first span and over a time window having a second span, the second span being longer than the first span. Clause 31. The method of clause 30, wherein the third freezing condition is that during the first time slot, the first time derivative determined over the first span is substantially different from the first time derivative measured over the second span. Clause 32. A method according to any one of clauses 23 to 31, wherein distortion due to movement in the first time slot is discarded if no indication of possible movement is derived from the mechanism for detecting movement, or if the possible movement derived from the mechanism for detecting movement is not sufficient to cause a freeze condition to be established. Clause 33. The method of any one of clauses 23 to 32, wherein detecting possible movement includes determining an electrical impedance between a movement sensor electrode and a movement sensor return electrode. Clause 34. The method of clause 33, wherein the moving sensor return electrode is the first return electrode. Clause 35. The method of clause 33 or 34, wherein a possible movement is derived if the first time derivative of the electrical impedance between the moving sensor electrode and the moving sensor return electrode during the first time slot exceeds a movement threshold. Clause 36. The method of clause 35, wherein the movement threshold is determined based at least in part on a measurement of the first time derivative. Clause 37. The method of clause 36, wherein the movement threshold varies over time. Clause 38. The method of any one 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 moving sensor electrode and the moving sensor return electrode. Clause 39. The method of clause 38, wherein 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 greater than a threshold value. Clause 40. The method of clause 39, wherein additional criteria are determined for the first time slot. Clause 41. The method of clause 39, wherein the additional criteria is determined after the first time slot. Article 42. A method for reducing adipose tissue, in particular a cosmetic method for reducing adipose tissue, comprising: Providing a cooling system according to any one of clauses 11 to 22; providing contact between a portion of the subject's skin and a cooling element of a cooling system; Optionally, cooling the subject's skin area for a period of up to 90 minutes; and and during cooling, carrying out the method of any one of clauses 23 to 41. Clause 43. The method according to clause 42, wherein cooling the skin portion comprises controlling the temperature of the cooling element to 0 to -15°C, in particular -5°C to -13°C. Clause 44. The method of clause 42 or 43, wherein cooling of the skin area is discontinued when a freezing event is detected. Clause 45. The method of any one of clauses 42 to 44, comprising temporarily heating the cooling element if a freeze event is detected. Clause 46. The method of any one of clauses 42 to 45, wherein an alarm is generated if a freezing event is detected. Clause 47. The method of any one of clauses 42 to 46, wherein the subject's skin portion is one or more of the thigh, buttocks, abdomen, submandibular tissue, knee, back, face, and arm. Clause 48. A method according to any one of clauses 42 to 47, further comprising checking the correct functioning of the cooling system by determining the electrical impedance between the cooling element and the first return electrode and / or by determining the electrical impedance between the moving electrode and the moving return electrode.

[0123] While only certain embodiments are disclosed herein, other alternatives, modifications, uses, and / or equivalents are possible. Moreover, all possible combinations of the described embodiments are also covered. Accordingly, the scope of the present disclosure should not be limited by specific embodiments, but should be determined solely by a fair reading of the following claims.

Claims

1. 1. A cooling system for reducing adipose tissue by cooling a skin portion of a subject, comprising: a base station; and one or more applicators, the applicators comprising: 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; the cooling element is electrically conductive and the cooling surface is substantially non-conductive; the cooling system is configured to determine freezing of the skin of the subject based on a time derivative of an electrical impedance between the cooling element and a first return electrode configured to be placed on a body of the subject; 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 a moving sensor electrode and a moving sensor return electrode.

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. The cooling system of claim 3 , wherein the current for determining the electrical impedance is less than 35 mA, specifically less than 1 mA, more specifically less than or equal to 0.5 mA.

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

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

7. Freezing events during cooling treatment determining a first electrical impedance between the cooling element and the first return electrode disposed on the subject; determining a time derivative of the determined first electrical impedance; determining movement, 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; 2. The cooling system of claim 1, configured to determine the freeze event by determining if the time derivative of the first electrical impedance satisfies one or more freeze conditions during a first time slot and distortion of the first electrical impedance due to movement within the same time slot is discarded.

8. 8. The cooling system of claim 7, wherein the time derivative of the first electrical impedance is a first time derivative, and a first freeze condition is that the first time derivative of the first electrical impedance exceeds a first freeze threshold during a first time slot.

9. The cooling system of claim 8 , wherein the first freeze threshold is determined based at least in part on a measurement of the first time derivative.

10. 10. A cooling system as claimed in any one of claims 7 to 9, wherein distortion due to movement in the first time slot is discarded if no indication of possible movement is derived from the mechanism for detecting movement, or if the possible movement derived from the mechanism for detecting movement is not sufficient to cause the freeze condition to be established.

11. The cooling system of claim 10, wherein the cooling system is configured to detect possible movement when the first time derivative of the electrical impedance between the movement sensor electrode and the movement sensor return electrode during the first time slot exceeds a movement threshold.

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