An assembly and a method for determining a temperature distribution of a foot

Abstract

The invention relates to an assembly and method for determining a temperature distribution of a foot. The assembly comprises : a mat comprising a surface for receiving and conforming to at least part of a plantar surface of the foot, wherein a temperature distribution of the surface of the mat is locally changeable by the plantar surface, and a thermal imaging apparatus comprising a detector responsive to infrared radiation and configured for acquiring a thermal image of at least the surface of the mat. The method uses the thermal imaging apparatus of the assembly to acquire a thermal image of a thermal footprint left on the surface of the mat by at least part of a plantar surface of the foot. The thermal image provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot.

Description

[0001] An assembly and a method for determining a temperature distribution of a foot

[0002] BACKGROUND

[0003] The invention relates to an assembly and a method for determining a temperature distribution of a foot , preferably a foot of a person .

[0004] Evidence exists that an early stage of a diabetic foot ulcer may be detectable from the temperature distribution of a skin of the foot . Accordingly, a determination of the temperature distribution of the feet of a diabetes patient on a regular basis can provide an indication for a possible presence of foot ulcers , and can provide an early warning system for foot ulcers or their preliminary stages . The final diagnosis that indeed a foot ulcer is developing will be made by a quali fied doctor or qualified person .

[0005] US5678566 discloses an insole for providing a visual indication of a thermal emission pattern of a plantar surface of a human foot . The insole is adapted to be placed within an interior of a shoe of a particular person, wherein the insole consists of a top foot-engaging layer af fixed to a bottom cushioning layer . The foot-engaging layer consists of a thin layer of micro-encapsulated, thermochromic liquid crystals sandwiched between a transparent polymer sheet and a black absorbing background layer . The thermochromic liquid crystal layer is heat-sensitive and exhibits di fferent colors depending on a temperature of the thermochromic liquid crystal layer .

[0006] The document further discloses inserting a bare foot of a patient within the shoe such that the plantar surface of the foot rests atop the foot engaging layer of the insole . As a result of the thermal emissions from the plantar surface of the foot, a pattern of colors is formed in the thermochromic liquid crystal layer which is indicative of a temperature of the plantar surface of the foot . Following a manual removal of the insole from the shoe , the insole is immediately photographed to provide a permanent record of the formed pattern of colors .

[0007] SUMMARY OF THE INVENTION

[0008] A disadvantage of the insole for determining a temperature distribution of a plantar surface of a foot as disclosed by US5678566 is that the insole is too complex and burdensome for patients for use on a regular, preferably daily basis .

[0009] A further disadvantage of the insole disclosed by US5678566 is that in order to provide a record of the formed pattern of colors in the thermochromic liquid crystal layer, the insole needs to be manually extracted from the shoe . As a result , the thermal emissions produced by the hand or fingers of the person extracting the insole tends to locally distort or corrupt the recorded thermal emission pattern .

[0010] It is an obj ect of the present invention to provide at least an alternative assembly and a method for determining a temperature distribution of a foot, and to obviate one or more of the above disadvantages at least partially .

[0011] According to a first aspect , the invention provides an assembly for determining a temperature distribution of a foot , wherein the assembly comprises : a mat comprising a surface for receiving at least part of a plantar surface of the foot , wherein a temperature distribution of the surface of the mat is locally changeable by said at least part of the plantar surface of the foot that is placed onto the surface of the mat, and a thermal imaging apparatus that is arranged spaced apart from the surface of the mat , wherein the thermal imaging apparatus comprises a detector that is responsive to infrared radiation and that is configured for acquiring a thermal image of at least the surface of the mat .

[0012] In response to at least part of the plantar surface of the foot ( thermally) contacting the surface of the mat , the foot tends to locally change a temperature distribution and / or locally heat up the surface of the mat . Accordingly, there is a heat exchange between the at least part of the plantar surface of the foot and the surface of the mat, which provides the temperature distribution of the surface of the mat . As a result, a temperature distribution of at least part of the plantar surface of the foot is transferred to the surface of the mat or, in other words , a thermal footprint is generated on the surface of the mat . Accordingly, the temperature distribution or the thermal footprint left on the surface of the mat substantially corresponds to the temperature distribution of a particular portion of the foot that has been in contact with the surface of the mat or which has been placed close to the surface of the mat . Following a removal of the foot from the surface of the mat, the subsequently obtained thermal image of the surface of the mat by the detector of the thermal imaging apparatus provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot .

[0013] When using the assembly of the invention, the person or patient only needs to place his / her foot or feet onto the surface of the mat for a suf ficient period of time to provide a thermal footprint and subsequently remove his / her foot or feet in order to acquire a thermal image of the surface of the mat to obtain a map or image that corresponds to the temperature distribution of at least part of the plantar surface of the foot . Accordingly, the assembly of the present invention allows a way of establishing a temperature distribution of at least part of the plantar surface of the foot on a regular, preferably on a daily basis which is easy and uncomplicated for a user .

[0014] In addition, by using the thermal imaging apparatus to record the thermal image of the thermal footprint generated by the foot on the surface of the mat , no further manual interaction is required to record the thermal footprint . As a result , a distortion or corruption caused by manual handling is substantially avoided .

[0015] A further advantage is that by determining the temperature distribution via the detector of the thermal imaging apparatus which is sensitive to infrared radiation, a measure or measurement is obtained that is substantially not affected or influenced by an environmental lighting condition . This allows to more easily compare dif ferent measurements obtained at dif ferent points in time . In contrast , obtaining a record of , for example , a color pattern in a thermochromic liquid crystal layer by means of a conventional visible light camera is significantly influenced by a particular lighting condition or camera setting used during the recording of the color pattern . As a result , an accurate comparison between di fferent measurements obtained at different points in time or at dif ferent locations can be dif ficult when using the visible light camera .

[0016] In an embodiment , the thermal imaging apparatus is configured for acquiring a thermal image of at least part of a dorsal surface of the foot that is placed on the surface of the mat . The thermal image acquired by the detector of the thermal imaging apparatus is based on the infrared emissions substantially directly emitted by the dorsal surface of the foot . This in contrast to a more ' indirect' determination of the temperature distribution of the plantar surface of the foot according to the present invention, wherein the acquired thermal image is based on the infrared emissions of the thermal footprint that remains on the surface of the mat due to an earlier contact of at least the plantar surface of the foot with the surface of the mat . Accordingly, the assembly according to this embodiment is configured to determine a temperature distribution of both the dorsal and plantar surfaces of the foot with a single thermal imaging apparatus , which single thermal imaging apparatus is preferably arranged at a fixed position above the surface of the mat . This is highly advantageous for an early warning system for foot ulcers , since ulcers can form both at the plantar and the dorsal side .

[0017] It is noted that one way to configure the thermal imaging device may be by selecting a detector with a large dynamic range that allows to acquire both a direct image of the foot and an indirect image of the thermal footprint with suf ficient details and / or contrast in each of the images . Another way to configure the thermal imaging device may be to adj ust the exposure settings , such as for example a shutter speed or aperture of the detector . It is to be understood that the assembly is preferably configured or used for determining a native or initial temperature distribution of a (human) foot . It is noted that the native temperature distribution of a foot refers to the temperature distribution of the foot immediately before positioning the foot on the mat . An alternative wording for 'native temperature distribution of a foot ' is ' initial temperature distribution of a foot' .

[0018] In an embodiment , at least the surface of the mat is configured to conform to the foot placed on said surface of the mat , in particular reversibly conform to the foot . As a result of at least the surface of the mat conforming to the foot, in particular to a shape of the plantar surface of the foot, an improved thermal contact between the plantar surface of the foot and the surface of the mat is achieved . Since the mat is configured to conform to the foot that is placed onto the mat, the concave portions of the plantar surface, such as an arch of the foot, are much closer to or in contact with the surface of the mat , in particular when compared to a mat comprising a substantially hard, non-conforming surface . Preferably said concave portions touch the surface of the mat to provide an improved thermal contact . The improved thermal contact in turn provides for an improved determination of the temperature distribution of at least the plantar surface of the foot . Furthermore, the improved thermal contact can act to shorten a contact time required between the foot and the surface of the mat to form the thermal footprint .

[0019] In an embodiment, the surface of the mat is configured to contact, in particular reversibly contact, a lateral surface and / or a medial surface of the foot . In an embodiment, the mat is configured to at least partially wrap around the foot that is arranged on the surface of the mat , in particular when the mat is compressed by the foot . As a result of the surface of the mat contacting the lateral surface and / or the medial surface of the foot, the thermal footprint formed on the surface of the mat encompasses a larger portion of the foot . Accordingly, upon removal of the foot from the mat, the subsequently acquired thermal image additionally comprises an image or map that substantially corresponds to a temperature distribution of the plantar surface, and the lateral surface and / or the medial surface of the foot . In particular when the assembly is configured for acquiring a thermal image of the dorsal surface of the foot, the assembly allows to provide a substantially ' all- around' determination of the temperature distribution of the foot .

[0020] In an embodiment, the assembly further comprises a control unit that is communicatively connected to the thermal imaging apparatus , wherein the control unit is configured to determine a presence of the foot on the surface of the mat and / or removal of the foot from the surface of the mat, preferably via a thermal image acquired by the detector of the thermal imaging apparatus . Accordingly, this embodiment allows to operate the assembly substantially automatically . In particular, this embodiment allows , in response to the determination of the presence and / or removal of the foot, to ( automatically) acquire a thermal image of the surface of the mat after removal of the foot and / or of the dorsal surface of the foot when present on the mat .

[0021] It is noted that preferably the control unit is configured to determine a presence and / or removal of the foot on the surface of the mat based on a thermal image acquired by the thermal imaging apparatus or an image acquired by a visible light imaging apparatus . In addition or alternatively, in an embodiment, the mat comprises a sensor, in particular a pressure sensor, arranged in the mat, wherein the sensor is communicatively connected to the control unit for sending a signal to the control unit that indicates the presence and / or removal of the foot on / from the surface of the mat . Alternatively, the assembly can be provided with a user interface, such as a button, which user interface is connected to the control unit for sending a signal to the control unit that indicated the presence and / or removal of the foot on / from the surface of the mat . In a further alternative , the assembly can be provided with a motion sensor that is configured to detect a motion indicative for the presence and / or removal of the foot on / from the surface of the mat . In a further alternative, the mat may be provided with one or more markings that promote a correct placement of the foot on the surface of the mat .

[0022] In an embodiment , the surface of the mat is a top surface, wherein the mat further comprises a bottom surface facing away from the top surface, wherein the top surface of the mat is locally deformable by the foot towards the bottom surface by at least 5 mm, preferably at least 10 mm, more preferably at least 15 mm and most preferably approximately 30 mm.

[0023] In an embodiment , the mat comprises or is substantially manufactured from a viscoelastic material , preferably wherein the viscoelastic material has a shore A hardness lower than 40 , more preferably lower than 10 , more preferably lower than 5 and most preferably lower than 3 and / or preferably wherein the viscoelastic material is a polymeric foam, more preferably a memory foam, and most preferably a memory foam comprising or based on polyurethane .

[0024] In an embodiment, the thermal imaging apparatus is configured and / or arranged to provide a thermal image of at least the surface of the mat with a spatial resolution on the mat of 5 mm or smaller . Accordingly, an increase in the spatial resolution allows for a determination of the temperature distribution of the foot in greater detail , and thus a detection or prediction of smaller or more complex ulcer regions . It is noted that the wording 'or smaller' refers to an improved resolving power of the thermal image acquired by the thermal imaging apparatus , such as 3 mm.

[0025] In an embodiment, the mat does not comprise a sensor for determining the temperature distribution of the foot and / or the surface of the mat . Accordingly, a substantially 'passive ' mat is provided which is easier to clean and substantially easier or less costly to manufacture compared to a mat comprising one or more sensors configured to determine a temperature .

[0026] In an embodiment, the mat does not comprise a heating element for heating the surface of the mat, and / or wherein the mat is not configured for ( actively) heating the surface of the mat .

[0027] According to a second aspect , the invention provides a method for determining a temperature distribution of a foot using the assembly according to the first aspect of the invention or any one embodiment thereof , wherein the method comprises the following step : using the thermal imaging apparatus to acquire a thermal image of a thermal footprint left on the surface of the mat by at least part of a plantar surface of the foot, wherein the thermal image provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot . In particular, the method provides for a determination of a native or initial temperature distribution of a (human) foot . The native or initial temperature distribution refers to the temperature distribution immediately before the foot is placed on the mat . Alternative wordings for the 'native temperature distribution' or ' initial temperature distribution' are 'pristine temperature distribution' or 'unaltered temperature distribution' .

[0028] The method according to the invention solves substantially the same problems and provides substantially the same advantages as discussed above in relation to the assembly of the present invention .

[0029] In an embodiment , the method further comprises a step of using the thermal imaging apparatus to acquire a thermal image of at least part of a dorsal surface of the foot, performed prior to the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot , wherein the thermal image of at least part of the dorsal surface of the foot provides a map or image that substantially corresponds to a temperature distribution of at least part of the dorsal surface of the foot . Accordingly, the method according to this embodiment allows to acquire images or maps that substantially correspond to a temperature distribution of both the dorsal and plantar surfaces of the foot with a single thermal imaging apparatus .

[0030] In an embodiment, at least the surface of the mat is configured to conform to the foot, in particular reversibly conform to the foot , wherein the method further comprises a step of using the foot for deforming the surface of the mat to at least partially conform the surface of the mat to the foot, in particular at least part of the plantar surface of the foot, performed prior to the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot . Accordingly, the method according to this embodiment can provide an improved thermal contact between the foot and the mat .

[0031] In an embodiment, the method further comprises a step of using at least part of the plantar surface of the foot to locally compress the mat such that the surface of the mat comes into contact with at least a part of the lateral surface and / or medial surface of the foot , performed prior to the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot . Accordingly, upon removal of the foot from the mat, the subsequently acquired thermal image additionally comprises an image or map that substantially corresponds to a temperature distribution of the plantar surface, and the lateral surface and / or the medial surface of the foot .

[0032] In an embodiment, the method further comprises the following step : determining a presence of the foot on the surface of the mat , preferably based on a thermal image acquired by the thermal imaging apparatus , and wherein the step of using the thermal imaging apparatus to acquire the thermal image of at least part of the dorsal surface of the foot is performed i f the presence of the foot on the surface is determined .

[0033] In an embodiment, the method further comprises the following step : determining a removal of the foot from the surface of the mat , preferably based on a thermal image acquired by the thermal imaging apparatus , and wherein the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot is performed if the removal of the foot from the surface of the mat is determined .

[0034] It is noted that a removal of the foot is a transition from a state in which the foot is present on the mat to a state in which the foot is removed from the mat . Accordingly to establish a removal of the foot, one needs to preferably first establish that the foot is / was present on the mat , and that subsequently the foot is no longer present on the mat .

[0035] In an embodiment, the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot further comprises a second thermal footprint left on the surface of the mat by at least part of a plantar surface of a second foot , wherein the thermal image further provides a map or image that substantially corresponds to a temperature distribution of at least part of the plantar surface of the second foot .

[0036] In an embodiment , the method further comprises a step of comparing a portion of the thermal image that comprises the thermal footprint of at least part of the plantar surface of the foot with a second portion of the thermal image that comprises the second thermal footprint to determine whether or not one or more regions are present in the temperature distribution of the foot that comprise a temperature deviation from the same or similar regions in the temperature distribution of the second foot .

[0037] In an embodiment, the thermal image of at least part of the dorsal surface of the foot further comprises at least part of a dorsal surface of the second foot , wherein the thermal image further provides a map or image that substantially corresponds to a temperature distribution of at least part of the dorsal surface of the second foot .

[0038] In an embodiment , the method further comprises a step of comparing a portion of the thermal image that comprises at least part of the dorsal surface of the foot with a second portion of the thermal image that comprises at least part of the dorsal surface of the second foot to determine whether or not one or more regions are present in the temperature distribution of the foot that comprise a temperature deviation from the same or similar regions in the temperature distribution of the second foot .

[0039] In an embodiment , the method further comprises a step of providing an indication to a user in response to determining that one or more regions are present in the temperature distribution of the foot that comprise the temperature deviation from the same or similar regions in the temperature distribution of the second foot that exceeds a predetermined threshold value .

[0040] In an embodiment , the method further comprises a step of storing the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot, and / or the thermal image of at least part of the dorsal surface of the foot, in a memory of a control device or processor .

[0041] In an embodiment , the method further comprises a step of comparing the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot with a previously stored thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot to determine whether or not one or more regions are present in the temperature distribution of the foot that comprise a temperature deviation from the same or similar regions in the previously stored image ( s ) .

[0042] In an embodiment , the method further comprises a step of comparing the thermal image of at least part of the dorsal surface of the foot, with a previously stored thermal image of at least part of the dorsal surface of the foot , to determine whether or not one or more regions are present in the temperature distribution of the foot that comprise a temperature deviation from the same or similar regions in the previously stored image ( s ) .

[0043] In an embodiment the temperature deviation exceeds a predetermined threshold value , preferably wherein the threshold value exceeds 0 . 5 ° C, more preferably 1 ° C, and most preferably 2 .2 ° C .

[0044] In an embodiment , the method further comprises a step of providing an indication to a user in response to determining that one or more regions are present in the temperature distribution of the foot that comprise the temperature deviation from the same or similar regions in the previously stored image ( s ) that exceeds a predetermined threshold value .

[0045] In an embodiment, the method further comprises the following step that is performed before the step of comparing the thermal image ( s ) with previously stored thermal image ( s ) : registering the thermal image ( s ) with the previously stored thermal image ( s ) .

[0046] It is noted that this image registering is a process of trans forming di f ferent images into one coordinate system, which allows an easy comparison of the thermal image ( s ) with the previously stored thermal image ( s ) .

[0047] In an embodiment, the method further comprises the following steps : providing an indication of a possible presence or development of a foot ulcer to a user based on a detection of an aberrant or abnormal region in the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot , and / or the thermal image of at least part of the dorsal surface of the foot .

[0048] The various aspects and features described and shown in the specification can be applied, individually, wherever possible . These individual aspects , in particular the aspects and features described in the attached dependent claims , can be made subj ect of divisional patent applications .

[0049] BRIEF DESCRIPTION OF THE DRAWINGS

[0050] The invention will be elucidated on the basis of an exemplary embodiment shown in the attached drawings , in which :

[0051] Figure 1 shows a schematic side view of an assembly for determining a temperature distribution of a foot, wherein the assembly comprises a thermal imaging apparatus and a mat ;

[0052] Figure 2 shows a side view of the assembly of figure 1 , wherein a foot is arranged on a surface of the mat ;

[0053] Figure 3 shows a schematic front view of the foot arranged on the surface of the mat through plane I I I- I I I of figure 2 ;

[0054] Figure 4A schematically illustrates a thermal image of a pair of feet placed on the surface of the mat , wherein the thermal image provides a map or image that substantially corresponds to a temperature distribution of a dorsal surface of the foot ;

[0055] Figure 4B schematically illustrates a thermal image of the surface of mat after a removal of the feet from the mat , wherein the thermal image provides a map or image that substantially corresponds to a temperature distribution of at least a plantar surface of the foot ;

[0056] Figures 5A and 5B each schematically illustrate a thermal image that respectively corresponds to the thermal images shown in figures 4A and 4B acquired by the thermal imaging apparatus at a later point in time ;

[0057] Figures 6A, 6B, 6C and 6D show examples of a flow diagram of methods according to the present invention .

[0058] DETAILED DESCRIPTION OF THE INVENTION

[0059] Figure 1 shows a side view of an assembly 1 for determining a temperature distribution of a foot, in particular of a skin of a bare human foot . The assembly 1 comprises a mat 2 arranged on a floor 5. The mat 2 comprises a top surface 3 for receiving at least part of a plantar surface, or a surface of a bottom side, of the foot . The top surface 3 of the mat 2 is locally heatable by at least part of the plantar surface of the foot when the foot is placed on the surface 3 of the mat 2 . Furthermore, or additionally, a temperature distribution of the top surface 3 of the mat 2 is locally changeable by at least part of the plantar surface of the foot when the foot is placed on the top surface 3 of the mat 2 . Accordingly, there is a heat exchange between the top surface 3 of the mat 2 and the foot which provides the temperature distribution of the top surface 3 of the mat 3 that is determined by the assembly 1 according to this example of the present invention .

[0060] The mat 2 further comprises a bottom surface 15 that is facing away from the top surface 3 and that abuts the floor 5. In the present example , the mat 2 comprises a thickness T of approximately 3 centimeters . The assembly 1 further comprises a thermal imaging apparatus 4 that is arranged spaced apart from the top surface 3 of the mat 2 . The assembly 1 is further comprises a mounting member 10 fixedly attached to a wall 6, wherein the mounting member 10 is configured for holding the thermal imaging apparatus 4 at a substantially fixed position above the mat 2 . It is noted that instead of a mounting to a wall 6, the thermal imaging apparatus 4 may, for example , also be mounted on a tripod that is standing on the floor 5 , or mounted directly on the floor 5, in particular at a position on the floor 5 next to the mat 2 .

[0061] The thermal imaging apparatus 4 comprises a detector 18 that is responsive to infrared or thermal radiation and that is configured for acquiring a thermal image of at least the surface 3 of the mat 2 . Accordingly, the detector 18 of the thermal imaging apparatus 4 is configured to detect at least infrared radiation emitted by the surface

[0062] 3 of the mat 2 . Furthermore, the assembly 1 comprises a control unit 19 and a memory 20 , preferably arranged in the thermal imaging apparatus 4 . The control unit 19 is configured to store one or more thermal images acquired via the detector 18 of the thermal imaging apparatus 4 in the memory 20 .

[0063] Figure 2 shows a side view of the assembly 1 , wherein at least part of the plantar surface 9 of the foot 7 has been brought into ( thermal ) contact with the surface 3 of the mat 2 . In particular, the foot 7 locally compresses or deforms at least the surface 3 of the mat 2 . The foot 7 is arranged at least partially between the surface 3 of the mat 2 and the thermal imaging apparatus 4 . When the thermal imaging apparatus 4 is further configured to directly acquire thermal images of the foot 7 , the thermal imaging apparatus

[0064] 4 can be used to acquire a thermal image of a dorsal surface 8 of the foot 7 , when the foot 7 is arranged on the surface 3 of the mat 2 . As exemplified in figure 4A, the acquired thermal image of at least part of the dorsal surface 8 , or a surface of a top side, of the foot 7 provides a map or image that substantially corresponds to the temperature distribution of at least part of the dorsal surface 8 of the foot 7 . In particular, figure 4A schematically illustrates a thermal image acquired by the detector 18 of the thermal imaging apparatus 4 of at least part of the dorsal surface 8 of a pair of feet comprising the foot 7 , in particular a right foot 7 , and a second foot 7 ’ , in particular a left foot 7 ’ , arranged on the surface 3 of the mat 2 . It is noted that in figure 4A a part of each lower leg is obscured by a trouser 17 worn by a person whose feet 7 , 7 ' are arranged on the surface 3 of the mat 2 .

[0065] The figure 2 further shows that the surface 3 of the mat 2 thermally contacts a surface or the skin of at least part of the plantar surface 9 of the foot 7 . Accordingly, a temperature distribution or a thermal footprint is generated on the surface 3 of the mat 2 , wherein the temperature distribution or the thermal footprint substantially corresponds to the temperature distribution of the surface of the foot 7 contacting the surface 3 of the mat 2 . When the foot 7 is subsequently removed from the surface 3 of the mat 2 , the detector 18 of the thermal imaging apparatus 4 can be used to acquire the thermal image of at least the surface 3 of the mat 2 comprising the thermal footprint . As exemplified in figure 4B, the thermal image of at least part of the thermal footprint 21 provides a map or image or a measure that substantially corresponds to the temperature distribution of at least a part of the plantar surface 9 of the foot 7 .

[0066] Returning now again to figure 2 , at least the surface 3 of the mat 2 is shown to conform to a shape of the plantar surface 9 of the foot 7 . As a result, a thermal contact between the foot 7 and the surface 3 of the mat 2 is improved . In particular when compared to a mat comprising a substantially hard, non-conforming surface . Furthermore, a larger portion of the plantar surface 9 of the foot 7 is brought into thermal contact with the surface 3 of the mat 2 when the foot 7 is arranged on the mat 2 . In turn, this leads to the temperature distribution or thermal footprint 21 formed on the surface 3 of the mat 2 to correspond to the larger portion of the plantar surface 9 of the foot 7 . Furthermore, if the surface 3 of the mat 2 is suf ficiently conforming, an arch surface 11 of the foot 7 will thermally contact the surface 3 of the mat 2 and thus contributing to the formed thermal footprint 21 .

[0067] Figure 3 shows a front view of the foot 7 arranged on the surface 3 of the mat 2 through plane I I I- I I I of figure 2 . The figure 3 shows that the surface 3 of the mat 2 is further configured to conform to a complex shape of a plurality of toes at the plantar surface 9 of the foot 7 . It is noted that the surface 3 of the mat 2 is preferably configured to reversibly conform to the foot 7 , wherein upon removal of the foot 7 the surface 3 of the mat 2 returns to its original state substantially corresponding to figure 1 .

[0068] Both figure 2 and figure 3 further illustrate that the surface 3 of the mat 2 is configured to contact, in particular reversibly contact, a side of the foot 7 or at least partially wrap around the side of the foot 7 . In particular, figure 3 shows the surface 3 of the mat 2 thermally contacting a lateral surface 16 , or a surface at a pinky toe side, of the foot 7 . Furthermore , the surface 3 of the mat 2 thermally contacts a medial surface 14 , or a surface at a big toe side, of the foot 7 . Additionally, as shown in figure 2 , the surface 3 of the mat 2 is furthermore configured to contact a heel surface 12 and a front surface 13 of the foot 7 . Accordingly, the surface 3 of the mat 2 tends to wrap around the foot 7 providing a thermal contact of the surface 3 of the mat 2 with the plantar surface 9 , lateral surface 15, medial surface 14 , front surface 13 and heel surface 12 of the foot 7 . Upon removal of the foot 7 , the surface 3 of the mat 2 returns back to its substantially flat condition, as schematically shown in figure 1 , and the parts of the surface that contacted the lateral surface 16, medial surface 14 , front surface 13 and heel surface 12 of the foot 7 are arranged adj acent to the part of the surface 3 that contacted the plantar surface 9.

[0069] As shown in figure 4B, the corresponding thermal footprint 21 formed on the surface 3 of the mat 2 upon a removal of the foot 7 further comprises a map or image that substantially corresponds to the temperature distribution of the lateral 16 , medial 14 , front 13 , arch 11 and heel 12 surfaces of the foot 7 , which surround the map or image of the plantar surface 9 of the foot 7 . In particular, the thermal image schematically illustrated in the figure 4B shows the thermal footprint 21 comprising a plantar region 9' , arch region 11 ' , medial region 14 ' , lateral region 16' , front region 13 ' and heel region 12 ' respectively corresponding to the regions of the surface 3 of the mat 2 which previously thermally contacted the plantar surface 9 , arch surface 11 , medial surface 14 , lateral surface 16, front surface 13 and heel surface 12 .

[0070] Accordingly, as respectively shown in figures 1 and 2 , by acquiring the thermal image of at least the dorsal surface 8 of the foot 7 , and after removal of the foot 7 from the surface 3 of the mat 2 , acquiring the thermal image of at least the thermal footprint 21 left by at least the plantar surface 9 of the foot 7 , a map or image that substantially corresponds to the temperature distribution is obtained that extends substantially 'all-around' the foot 7 .

[0071] The control unit 19 of the thermal imaging apparatus 4 as shown in the figures 1 and 2 is preferably configured to determine an arrival , presence or removal of the foot 7 on or near the surface 3 of the mat 2 . In response to the control unit 19 determining the arrival or the presence of the foot 7 on or near the surface 3 of the mat 2 , the control unit 19 is configured to acquire the thermal image of at least the dorsal surface 8 of the foot 7 . Accordingly, the control unit 19 is preferably configured to detect a situation substantially corresponding to figures 2 and 3 . Furthermore, the control unit 19 is preferably further configured to determine a removal of the foot 7 from the surface 3 of the mat 2 . In response to the control unit 19 determining the removal of the foot 7 from the surface 3 of the mat 2 , the control unit 19 is configured to acquire the thermal image of at least the surface 3 of mat 2 comprising the thermal footprint 21 as shown in figure 4B . Alternatively, the control unit 19 may be configured to determine the arrival , presence and / or removal of a foot 7 via a (pressure ) sensor (not shown) arranged in or under the mat 2 . Furthermore , the assembly 1 although not shown can be provided with a motion detecting unit or a user interface communicatively coupled to the control unit 19 .

[0072] As illustrated in figure 2 , the top surface 3 of the mat 2 is locally deformable by the foot 7 towards the bottom surface 15 of the mat 2 . Figure 2 further shows that the top surface 3 is deformable, or compressible, towards the bottom surface 15 by a distance D of at least 5 mm. The mat 2 is preferably prepared from or comprises a viscoelastic material , in particular a polyurethane memory foam. It is noted that at least the surface 3 of the mat 2 is preferably thermally insulating to , for example , avoid a cold sensation when a person arranges a bare foot 7 on the surface 3 of the mat 2 , and to ensure that the thermal footprint 21 remains on the surface 3 of the mat 2 for sufficient time to acquire the thermal image of the thermal footprint 21 as shown in figure 4B .

[0073] Figures 4A and 4B each schematically illustrate a thermal image that substantially corresponds to a temperature distribution of a healthy pair of feet 7 , 7 ' substantially without aberrant or abnormal regions . In contrast , figures 5A and 5B each illustrate a thermal image that substantially corresponds to a temperature distribution of a pair of feet 7 , 7 ' comprising regions 22 - 25 with an increased or decreased temperature . In particular, the figures 5A and 5B correspond to or represent a pair of thermal images recorded of the feet 7 , 7 ' of the same person at a later point in time compared to figures 4A and 4B .

[0074] Figure 5A shows a first region 22 of the dorsal surface 8 of the foot 7 , in particular the right foot 7 , showing an increased temperature compared to a corresponding region of the dorsal surface 8 of the second foot 7 ’ , in particular the left foot 7 ' , or a corresponding region of the dorsal surface 8 of the foot 7 of the earlier thermal image shown in figure 4A. Furthermore, figure 5A shows a second region 23 of the dorsal surface 8 of the second foot 7 ' , in particular a second toe, with a decreased temperature compared to a corresponding region of the foot 7 or a corresponding region of the second foot 7 ' of the earlier thermal image shown in figure 4A. Figure 5B shows a thermal footprint 21 comprising a third region 24 and a second thermal footprint 21 ' comprising a fourth region 25. Here, the thermal footprint 21 and the second thermal footprint 21 ' respectively substantially correspond to the temperature distribution of the foot 7 and second foot 7 ' . The third region 24 is arranged at least partially in or at the lateral region 16 ' of the thermal footprint 21 and accordingly substantially corresponds to the lateral surface 16 of the foot 7 . Furthermore , the third region 24 shows an increased temperature compared to a corresponding region of the second thermal footprint 21 ' , and / or a corresponding region of the thermal footprint 21 of the earlier thermal image shown in figure 4B . The fourth region 25 is arranged at least partially in the front region 13 ' and accordingly substantially corresponds to the front region 13 of the second foot 7 ' . The fourth region 25 shows a decreased temperature compared to a corresponding region of the thermal footprint 21 and / or a corresponding region of the footprint 21 ' in the earlier thermal image shown in figure 5B . Furthermore, it is noted that the fourth region 25 shown in figure 5B is formed through thermal contact with a portion of the second foot 27 ' that is substantially adj acent to the second region 23 shown in figure 5A. Accordingly, the thermal images shown in figures 5A and 5B together provide a temperature distribution that substantially corresponds to a plantar surface , front surface and dorsal surface of the second toe .

[0075] In particular the first and third regions 22 , 24 that show an increase in temperature compared to an earlier thermal image or the corresponding other foot, are an indication of a possible presence , formation or development of a foot ulcer . Accordingly, said indication can be used to provide an early warning for foot ulcers or their preliminary stages . It is to be understood that , a final diagnosis that a foot ulcer is indeed developing is made by a qualified person or doctor .

[0076] Figure 6A schematically shows a flow chart illustrating a set of method steps for determining a temperature distribution of a foot . The method comprises the following steps , preferably performed subsequently :

[0077] 101 providing a mat that comprises a surface for receiving at least part of a plantar surface of the foot ,

[0078] 102 providing a thermal imaging apparatus that is spaced apart from the surface of the mat , wherein the thermal imaging apparatus comprises a detector that is responsive to infrared radiation,

[0079] 103 placing the foot onto the surface of the mat , wherein at least part of the plantar surface of the foot is in ( thermal ) contact with the surface of mat ,

[0080] 104 optionally, using the thermal imaging apparatus to acquire a thermal image of at least part of a dorsal surface of the foot ,

[0081] 105 removing the foot from the surface of the mat, and

[0082] 106 using the thermal imaging apparatus to acquire a thermal image of a thermal footprint left on the surface of mat , wherein the thermal image provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot .

[0083] Figure 6B schematically shows a flow chart illustrating a set of alternative method steps for determining a temperature distribution of a foot . The method comprises the following steps , preferably performed subsequently :

[0084] 110 providing a mat that comprises a surface for receiving at least part of a plantar surface of the foot ,

[0085] 111 providing a thermal imaging apparatus that is spaced apart from the surface of the mat , wherein the thermal imaging apparatus comprises a detector that is responsive to infrared radiation,

[0086] 112 using the foot for deforming the surface of the mat to at least partially conform the surface of the mat to the foot, in particular the plantar surface of the foot ,

[0087] 113 using at least part of the plantar surface of the foot to locally compress the mat such that the surface of the mat comes into contact with at least a part of the lateral surface and / or medial surface of the foot

[0088] 114 optionally, using the thermal imaging apparatus to acquire a thermal image of at least part of a dorsal surface of the foot ,

[0089] 115 removing the foot from the surface of the mat, and

[0090] 116 using the thermal imaging apparatus to acquire a thermal image of a thermal footprint left on the surface of mat , wherein the thermal image provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot, in particular at least part of the plantar, lateral and / or medial surfaces of the foot .

[0091] Figure 6C schematically shows a flow chart illustrating a set of further alternative method steps for determining a temperature distribution of a foot . The method comprises the following steps :

[0092] 118 using a thermal imaging apparatus to acquire a thermal image of a thermal footprint left on a surface of a mat and / or at least part of a dorsal surface of a foot according to the method steps shown in figure 6A, or using a thermal imaging apparatus to acquire a thermal image of a thermal footprint left on a surface the surface of a mat and / or at least a part of dorsal surface of a foot according to the method steps shown in figure 6B,

[0093] 119 comparing the thermal image of the thermal footprint left on the surface of the mat with at least one earlier thermal image of the thermal footprint left on the surface of the mat to determine whether or not the temperature distribution of the foot has changed with respect to the temperature distribution according to the at least one earlier thermal image,

[0094] 120 (optionally) comparing the thermal image of the dorsal surface of the foot with at least one earlier thermal image of the dorsal surface of the foot to determine whether or not the temperature distribution of the foot has changed with respect to the temperature distribution according to the at least one earlier thermal image, and

[0095] 121 providing an indication of a possible presence or development of a foot ulcer to a user based on a detection of an aberrant or abnormal region in the thermal image of the thermal footprint left on the surface of the mat and / or the thermal image of the dorsal surface of the foot based on the comparison .

[0096] Figure 6D schematically shows a flow chart illustrating a set of further alternative method steps for determining a temperature distribution of a foot . The method comprises the following steps :

[0097] 130 using a thermal imaging apparatus to acquire a thermal image of a first thermal footprint and a second thermal footprint left on a surface of a mat by at least part of a plantar surface of respectively a first foot and a second foot,

[0098] 131 comparing a first portion of the thermal image that comprises the first thermal footprint with a second portion of the thermal image that comprises the second thermal footprint, 132 determine whether or not one or more regions are present in the first portion that comprise a temperature deviation from the same or similar regions in the second portion,

[0099] 133 (optionally) using the thermal imaging apparatus to acquire a thermal image of at least part of a dorsal surface of the first foot and at least part of a dorsal surface of the second foot,

[0100] 134 (optionally) comparing a first portion of the thermal image that comprises at least part of the dorsal surface of the first foot with a second portion of the thermal image that comprises at least part of the dorsal surface of the second foot,

[0101] 135 (optionally) determine whether or not one or more regions are present in first portion that comprise a temperature deviation from the same or similar regions in the second portion, and

[0102] 136 providing an indication to a user in response to determining that one or more regions are present in the first portion of the thermal image that comprise the temperature deviation from the same or similar regions in the second portion of the thermal image which exceed a predetermined threshold value .

[0103] It is to be understood that the above description is included to illustrate the operation of the preferred embodiments and is not meant to limit the scope of the invention . From the above discussion, many variations will be apparent to one skilled in the art that would yet be encompassed by the scope of the present invention .

[0104] In summary, the invention relates to an assembly and method for determining a temperature distribution of a foot . The assembly comprises : a mat comprising a surface for receiving and conforming to at least part of a plantar surface of the foot , wherein a temperature distribution of the surface of the mat is locally changeable by the plantar surface , and a thermal imaging apparatus comprising a detector responsive to infrared radiation and configured for acquiring a thermal image of at least the surface of the mat .

[0105] The method uses the thermal imaging apparatus of the assembly to acquire a thermal image of a thermal footprint left on the surface of the mat of the assembly by at least a plantar surface of the foot . The thermal image provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot .

Claims

C L A I M S1 . An assembly for determining a temperature distribution of a foot , wherein the assembly comprises : a mat comprising a surface for receiving at least part of a plantar surface of the foot , wherein a temperature distribution of the surface of the mat is locally changeable by said at least part of the plantar surface of the foot that is placed onto the surface of the mat, wherein at least the surface of the mat is configured to conform to the foot placed on said surface of the mat, and a thermal imaging apparatus that is arranged spaced apart from the surface of the mat , wherein the thermal imaging apparatus comprises a detector that is responsive to infrared radiation and that is configured for acquiring a thermal image of at least the surface of the mat .2 . The assembly according to claim 1 , wherein the thermal imaging apparatus is configured for acquiring a thermal image of at least part of a dorsal surface of the foot that is placed on the surface of the mat .3 . The assembly according to claim 1 or 2 , wherein at least the surface of the mat is configured to reversibly conform to the foot placed on said surface of the mat .4 . The assembly according to claim 1 , 2 or 3 , wherein the surface of the mat is configured to contact, in particular reversibly contact, a lateral surface and / or a medial surface of the foot, preferably wherein the mat is configured to at least partially wrap around the foot that is placed on the surface of the mat , in particular when the mat is compressed by the foot .

5. The assembly according to any one of the claims 1 - 4 , wherein the assembly further comprises a control unit that is communicatively connected to the thermal imaging apparatus , wherein the control unit is configured to determine a presence of the foot on the surface of the mat and / or removal of the foot from the surface of the mat, preferably via a thermal image acquired by the detector of the thermal imaging apparatus .

6. The assembly according to any one of the claims 1 - 5, wherein the surface of the mat is a top surface , wherein the mat further comprises a bottom surface facing away from the top surface, wherein the top surface of the mat is locally deformable by the foot towards the bottom surface by at least 5 mm, preferably at least 10 mm, more preferably at least 15 mm and most preferably approximately 30 mm .7 . The assembly according to any one of the claims 1 - 6, wherein the mat comprises or is substantially manufactured from a viscoelastic material , preferably wherein the viscoelastic material has shore A hardness lower than 40 , more preferably lower than 10 , more preferably lower than 5 and most preferably lower than 3 , and / or preferably wherein the viscoelastic material is a polymeric foam, more preferably a memory foam, and most preferably a memory foam comprising or based on polyurethane .8 . The assembly according to any one of the claims 1 - 7 , wherein the thermal imaging apparatus is configured and / or arranged to provide a thermal image of at least the surface of the mat with a spatial resolution on the mat of 5 mm or smaller .

9. The assembly according to any one of the claims 1 - 8 , wherein the mat does not comprise a sensor for determining the temperature distribution of the foot and / orthe surface of the mat .10 . A method for determining a temperature distribution of a foot using the assembly according to any one of the claims 1 - 9 , wherein the method comprises the following step : using the thermal imaging apparatus to acquire a thermal image of a thermal footprint left on the surface of the mat by at least part of a plantar surface of the foot, wherein the thermal image provides a map or image that substantially corresponds to the temperature distribution of at least part of the plantar surface of the foot .11 . The method according to claim 10 , wherein the method further comprises a step of using the thermal imaging apparatus to acquire a thermal image of at least part of a dorsal surface of the foot, performed prior to the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot , wherein the thermal image of at least part of the dorsal surface of the foot provides a map or image that substantially corresponds to a temperature distribution of at least part of the dorsal surface of the foot .12 . The method according to claim 10 or 11 , wherein at least the surface of the mat is configured to conform to the foot , in particular reversibly conform to the foot, wherein the method further comprises a step of using the foot for deforming the surface of the mat to at least partially conform the surface of the mat to the foot, in particular at least part of the plantar surface of the foot, performed prior to the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot .13 . The method according to claim 10 , 11 or 12 , wherein the method further comprises a step of using at least part of the plantar surface of the foot to locally compress the mat such that the surface of the mat comes into contact with at least a part of the lateral surface and / or medial surface of the foot , performed prior to the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot .14 . The method according to claim 11 , or claim 12 or 13 when dependent on claim 11 , wherein the method further comprises the following step : determining a presence of the foot on the surface of the mat , preferably based on a thermal image acquired by the thermal imaging apparatus , and wherein the step of using the thermal imaging apparatus to acquire the thermal image of at least part of the dorsal surface of the foot is performed i f the presence of the foot on the surface is determined .

15. The method according to any one of the claims 10 - 14 , wherein the method further comprises the following step : determining a removal of the foot from the surface of the mat , preferably based on a thermal image acquired by the thermal imaging apparatus , and wherein the step of using the thermal imaging apparatus to acquire the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot is performed if the removal of the foot from the surface of the mat is determined .

16. The method according to any one of the claims 10 - 15, wherein the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot further comprises a second thermalfootprint left on the surface of the mat by at least part of a plantar surface of a second foot, wherein the thermal image further provides a map or image that substantially corresponds to a temperature distribution of at least part of the plantar surface of the second foot , wherein the method further comprises a step of comparing a portion of the thermal image that comprises the thermal footprint of at least part of the plantar surface of the foot with a second portion of the thermal image that comprises the second thermal footprint to determine whether or not one or more regions are present in the temperature distribution of the foot that comprise a temperature deviation from the same or similar regions in the temperature distribution of the second foot, preferably the method further comprises a step of providing an indication to a user in response to determining that one or more regions are present in the temperature distribution of the foot that comprise the temperature deviation from the same or similar regions in the temperature distribution of the second foot that exceeds a predetermined threshold value .17 . The method according to any one of the claims 10 - 16, wherein the method further comprises a step of storing the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot in a memory of a control device or processor .18 . The method according to claim 17 , the method further comprises a step of comparing the thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot with a previously stored thermal image of the thermal footprint left on the surface of the mat by at least part of the plantar surface of the foot to determine whether or not one or more regions are present in the temperature distribution of thefoot that comprise a temperature deviation from the same or similar regions in the previously stored image ( s ) , preferably the method further comprises a step of providing an indication to a user in response to determining that one or more regions are present in the temperature distribution of the foot that comprise the temperature deviation from the same or similar regions in the previously stored image ( s ) that exceeds a predetermined threshold value .

19. The method according to claim 16 or 18 , wherein the temperature deviation exceeds a predetermined threshold value, preferably wherein the threshold value exceeds 0 . 5 ° C, more preferably 1 ° C, and most preferably 2 .2 ° C .20 . The method according to any one of the claims 10 - 19, wherein the method further comprises the following steps : providing an indication of a possible presence or development of a foot ulcer to a user based on a detection of an aberrant or abnormal region in the thermal image of the thermal footprint left on the surface of the mat by at least the plantar surface of the foot , and / or ( if present ) the thermal image of at least part of the dorsal surface of the foot .-o-o-o-o-o- o-o-o-MVD / BP

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