Flexible 3D Printed Water Sac Insert

Abstract

During hyperthermia treatment in the head and neck region, a conventional water bladder used to direct electromagnetic waves and cool the patient's skin during such treatment may collapse onto the patient's face due to the weight and / or pressure of the water within the water bladder. An insert may be disposed within the water bladder to remedy this, where the insert provides additional stiffness and thus resists the weight and pressure of the water. However, the insert should not resist the patient's shape too much and thus, the insert provides a first stiffness in a first load direction and a second stiffness in a second load direction, where the first stiffness is not equal to the second stiffness.

Description

Field of the Invention

[0001] The present invention relates to a water bolus for covering a part of the external body surface of a body part. Background Art

[0002] Hyperthermia treatment is a method for treating tumor cells by exposing the body tissue of a cancer patient to a temperature of 40 to 44 °C. Hyperthermia stimulates blood perfusion, resulting in, for example, more effective delivery of drugs and more oxygen in the tissue, and thus more oxygen free radicals are generated by ionizing radiation. Hyperthermia also makes the tissue sensitive to these DNA-damaging agents in various ways (such as by blocking DNA damage repair). When hyperthermia treatment is performed at a temperature of up to 44 °C for up to 1 hour, healthy tissue can remain unharmed. The high temperature required for hyperthermia treatment is caused by exposing the patient's body tissue to electromagnetic waves.

[0003] When tumor cells are heated, the electromagnetic waves may cause skin burns to the patient's skin. In addition, it may be difficult to direct the electromagnetic waves to the correct position within the patient's body. To solve these problems, a layer of water, a water bolus, is placed between the electromagnetic wave generator and the patient's skin as a coolant to prevent burns caused by radiant heat and as a transmitter of electromagnetic energy. The electromagnetic waves typically have a frequency of 500 kHz to 1 GHz.

[0004] Known water boluses are formed as air bags through which water can circulate. One side of the water bolus is arranged for skin contact, and preferably, the contact between the water bolus and the skin is as good as possible, which means that an air gap between the water bolus and the skin is not desired. However, a water bolus that is completely filled with water cannot provide reliable skin contact because, for example, wrinkles or sharp wedges appear on the patient side of the water bolus, which creates an undesired air gap between the patient's skin and the water bolus. At the site of the wedge, the shape change may cause a high concentration of electromagnetic fields, resulting in local hyperthermia and a risk of toxicity to the patient. After hyperthermia, the wedge results in an area with poor cooling, which, combined with heating, poses a high risk of burns.

[0005] In addition, due to the weight and pressure of the water within the water bladder, the fully filled water bladder presses against the body part of the patient being treated. For example, when the body part is the patient's head, face, or neck, this pressure may be felt as uncomfortable. EP2744564B1 discloses the use of a foam insert provided within the water bladder. Such a foam insert increases the shape stability and reduces the amount of unwanted wrinkles on the patient side of the water bladder. Any insert has the drawback that it reduces the volume percentage of water within the water bladder, which can reduce the volume-averaged dielectric value and thus reduce the guidance of electromagnetic energy or acoustic energy. Therefore, open-cell polyether foam is used because it provides a low filling percentage and thus allows most of the available volume within the water bladder to be filled with water. The open-cell structure of the foam also allows water to flow easily through the insert and thus through the water bladder, which is beneficial for effectively cooling the patient's skin and obtaining a more uniform water temperature within the water bladder. Summary of the Invention

[0006] Preferably, a water bladder is provided with even more improved shape stability.

[0007] Although the open-cell foam insert improves the shape stability, unforeseen wrinkles are still prone to appear on the patient-skin side of the water bladder. These wrinkles locally block the water circulation and inhibit the prevention of temperature hotspots on the patient's skin. In addition, the increased shape stability of the water bladder can provide a better match between the software simulation of hyperthermia treatment and the real situation. The software simulation can be used for treatment planning.

[0008] In a first aspect, there is provided a water bladder for covering a part of the external body surface of a body part, which comprises a flexible cover forming a container arranged to contain a fluid and an insert provided within the container, wherein the insert is arranged to provide a first stiffness in a first load direction and a second stiffness in a second load direction, wherein the first stiffness is lower than the second stiffness, and the cover stiffness of the flexible cover is lower than the first stiffness. In an embodiment, the first load direction is perpendicular to the second load direction.

[0009] For stiffness, in this specification, this property means how an object resists deformation under a certain force. Stiffness can be expressed in N / mm, that is, the amount of force required to deform an object a certain distance. Stiffness can depend on the material of which the object is made, the shape of the object, the wall thickness of the object, and in which direction the force is applied to the shape of the object. In addition to the known open-cell foam inserts, the insert according to the present invention provides different stiffnesses in different load directions. Opposite to stiffness is flexibility, that is, the property of how an object conforms to deformation under a certain force.

[0010] Known open-cell foam inserts in the art provide substantially the same stiffness in each load direction and, due to the structure of the open-cell foam, also provide substantially the same stiffness wherever the force is applied. The structure consists of pores that are not completely closed, which is required to allow water to flow through the insert.

[0011] In a first load direction, greater flexibility may be required, for example to ensure a good fit between the patient's skin and the water bladder. In a second load direction, greater stiffness may be required, for example to resist the shape instability of the water bladder due to the weight and pressure of the water within the water bladder, or to resist an external load on the water bladder, such as the operation of the user. The flexible cover forming the container is generally more compliant than the insert, which means that the shape of the insert mainly determines the shape of the container, and the shape of the flexible cover adapts to the shape of the insert.

[0012] In many configurations, the water bladder will have an overhanging portion, which is the part of the higher portion that hangs over the lower portion when in use. When the water bladder is filled with water, the higher portion will tend to deform towards the lower portion. In use, the patient's head can be located between the lower portion and the higher portion, and thus the higher portion can press into the patient's face, which can be considered an uncomfortable pressure. By reducing the deformation of the higher portion towards the lower portion and thereby reducing the pressure on the patient's head, the increased stiffness of the insert resisting this overhang can increase the comfort of the patient. More generally, since the container includes a flexible cover, when filled with water, the flexible cover elastically deforms due to water pressure and weight, and the container tends to sag.

[0013] For open-cell foam inserts, due to the isotropic stiffness of the open-cell foam material, a single stiffness has been selected for all load directions. This results in a non-optimal first stiffness in the first load direction, a non-optimal second stiffness in the second load direction, or a compromise between the two stiffnesses, such that neither the optimal first stiffness nor the optimal second stiffness is achieved. A first aspect provides a water bladder containing an insert having anisotropic stiffness.

[0014] At least a portion of the inner surface of the insert can be substantially complementary to at least a portion of the external body surface, and the first load direction can be oriented substantially orthogonal to the inner surface of the insert for most of the inner surface. Since at least a portion of the inner surface of the insert is complementary to at least a portion of the external body surface, the water bladder is preformed to fit the external body surface, which reduces the likelihood of unwanted wrinkles on the patient side of the water bladder.

[0015] The complementarity between the inner surface of the insert and the external body surface can result in small deviations in the correspondence between the inner surface of the insert and the external body surface. The water pressure filled into the container can be used to compensate for the small deviations.

[0016] To provide a first stiffness in a first load direction and a second stiffness in a second load direction, the insert may include a plurality of connected, thin-walled, elongated, parallel hollow structures.

[0017] The structures are connected to allow direct force transfer between adjacent structures and thus, for example, can prevent buckling. The structures are thin-walled to minimize the volume of the insert within the bladder, which maximizes the possible volume of water within the bladder. The structures are elongated to allow an elongated flow path through the structures and are parallel to make the flow paths substantially parallel to each other. The structures are hollow to allow water to flow through the structures from one end to the other.

[0018] Within the bladder, a certain dielectric constant may be preferred. The dielectric constant may preferably be relatively high as it may match the electromagnetic frequencies used by certain hyperthermia devices. Additionally or alternatively, the dielectric constant may match the dielectric constant of the patient's body. To obtain the desired dielectric constant, a certain ratio of insert volume to water may be selected to obtain the desired dielectric constant.

[0019] Furthermore, the dielectric constant may be different in different sections of the bladder, for example by locally adjusting the ratio of insert volume to water volume. The material used to manufacture the insert typically has a lower dielectric constant than water, and thus this property can be used to at least locally reduce the dielectric constant, as observed by electromagnetic waves passing through the bladder towards the patient. For example, the local adjustment of the dielectric constant can be achieved by locally adjusting the wall thickness of the insert. The preferred dielectric constant can be calculated or determined before manufacturing the insert, for example using computer simulations, so that a customized insert can be manufactured for a specific case or patient.

[0020] When the insert includes a plurality of connected, thin-walled, elongated, parallel hollow structures, the second load direction may be oriented substantially parallel to the elongation direction of the hollow structures, and the first load direction is substantially perpendicular to the elongation direction of the hollow structures.

[0021] In an embodiment of the bladder, the hollow structures are arranged in an elongated hexagonal structure, also known as a honeycomb structure. As the name already implies, the honeycomb structure is inspired by the way bees build their hives to provide sufficient strength while also providing as much space as possible for their honey. The hexagonal structure eliminates unnecessary material, which results in a small fill percentage of the structural material and a large fill percentage of water within the bladder. This ensures a limited effect of the material on electromagnetic waves.

[0022] When the insert is arranged in an elongated hexagonal structure, the insert can be arranged to provide a third stiffness in a third load direction, where the third load direction is substantially perpendicular to the elongation direction of the hollow structure and is oriented at an angle of about 90 degrees relative to the first load direction, and where the third stiffness can be higher than the first stiffness. Alternatively, the third stiffness of the insert can be lower than the first stiffness, as understood by those skilled in the art, for example by manipulating the wall thickness of some or all of the walls of one or more structures, or by manipulating the cross-section of one or more structures. Thus, these three load directions can be orthogonal to each other.

[0023] In the use of the water bladder, the third load direction can be a substantially vertical direction, and the first load direction can be a substantially horizontal direction.

[0024] The container can include a fluid input for receiving fluid and a fluid output for releasing fluid, such that fluid flow can be provided between the fluid input and the fluid output within the container. Fluid flow through the water bladder can be established between the fluid input and the fluid output. This flow allows for better regulation of the fluid temperature in the water bladder, and more specifically, allows for a more uniform fluid temperature. A uniform fluid temperature may be most desirable at or near the patient's skin, and the insert design can be adjusted to optimize the fluid flow, which is arranged to provide such a uniform fluid temperature at or near the patient's skin.

[0025] The preferred fluid is water, but other fluids can also be used in the water bladder. Water has the advantages of being inexpensive and widely available, having good thermal properties, and being non-toxic. For example, different fluids can be selected according to the dielectric constant of the desired water bladder or its section.

[0026] The first of the fluid input and the fluid output can be provided on the first side of the flexible cover, and the second of the fluid input and the fluid output can be provided by a fluid conduit that extends substantially from the first side of the flexible cover to the second side opposite the first side.

[0027] Regarding this configuration of the fluid input and the fluid output, both can be provided on the same side of the water bladder while maintaining good water flow through the entire water bladder.

[0028] When the second of the fluid input and the fluid output is provided by a fluid conduit, the fluid conduit can extend through the container and thus not be outside the container. This can provide a compact form factor for the water bladder and there is no space on either the patient side or the device side for extending the fluid conduit outside the water bladder.

[0029] At least some of the plurality of hollow structures may include a plurality of perforations such that the hollow interiors of adjacent hollow structures provided with perforations are in fluid communication with each other. This not only allows separate fluid to flow through each separate elongate structure, but also allows fluid to flow between adjacent structures. This can increase the uniformity of the water temperature within the water bladder.

[0030] The water bladder fluid may be arranged such that fluid flows within the water bladder from a first side to a second side, and the flow-through surface of the perforations may increase significantly from the first side to the second side.

[0031] To be able to measure the pressure applied to the patient's skin, a pressure sensor may be inserted into the water bladder. Based on the measured pressure, the water volume within the bladder may be increased or decreased.

[0032] The water bladder may be arranged for transmitting electromagnetic energy through the water bladder, for example when the water bladder is to be used for hyperthermia treatment.

[0033] The wall thickness of the hollow structure may be increased according to the expected fluid pressure within the water bladder. This allows for further optimization of the volume occupied by the insert within the water bladder. The wall thickness does not need to be the same everywhere, as the forces due to water pressure will increase in the direction opposite to gravity.

[0034] When the water bladder is arranged for fluid flow within the water bladder from a first side to a second side, the perforations may be spaced apart, and the average distance between adjacent perforations may increase from the first side to the second side.

[0035] When the structure includes a plurality of perforations, the first perforation may be arranged such that it is not aligned with the second perforation with respect to the elongate direction. This can provide the water bladder with a flow path through the perforations having enhanced thermal properties. Brief Description of the Drawings

[0037] Now its various aspects and embodiments will be discussed in conjunction with the drawings. In the drawings:

[0038] Figure 1A A top view of a part of a hyperthermia device is shown;

[0039] Figure 1B A front view of a part of a hyperthermia device is shown;

[0040] Figure 2A Another top view of a part of a hyperthermia device is shown;

[0041] Figure 2B Another front view of a part of a hyperthermia device is shown;

[0042] Figure 3A A part of an embodiment of an insert is shown;

[0043] Figure 3BAnother embodiment of the insert is shown;

[0044] Figure 4A A schematic view of a part of the hyperthermia device is shown; and

[0045] Figure 4B Another schematic view of a part of the hyperthermia device is shown. Detailed Description

[0046] Based on examples of using a water bag in hyperthermia treatment, different embodiments of the present invention will be explained in more detail. Different applications of the water bag are also envisioned, as will be further discussed in this specification.

[0047] One of the most difficult areas to reach in hyperthermia treatment is the head and neck region. Therefore, the drawings will be directed to embodiments of the water bag for hyperthermia treatment of the head, neck, and / or larynx. Those skilled in the art will understand that different applications of the water bag for different body parts are also envisioned, and thus the water bag can be shaped differently from those shown in the drawings. For example, a water bag for treating the head region can span the distance between a patient's eyes and chin. In another example, a water bag for treating the neck region can span the distance between a patient's eyes and the cervical vertebrae. The height of the water bag can, for example, reach the height of the patient's eye level from behind the patient's head. In yet another example, the water bag can be shaped to complement one or more other body parts, such as at least a part of the skull, abdomen, leg, at least a part of the pelvic region, breast, any other body part, especially a curved body part, or any combination thereof. The shaped water bag can be preformed such that the desired shape is obtained after filling the water bag with water. Computer calculations and / or simulations can be used to determine the shape of the water bag without water and the shape of the water bag when the water bag has been filled with water. Since gravity can affect the shape of the water bag, the position and / or orientation at which the water bag is used can also be considered.

[0048] The main purpose of the water bag, as discussed, is to transmit electromagnetic waves to the patient's tissue and prevent skin burns to the patient's skin due to the heat caused by these electromagnetic waves. Another purpose of the water bag is to help maintain the position and / or orientation of the patient's head during treatment.

[0049] In addition to making the patient more comfortable, the operator of the hyperthermia device that needs to handle the water bag can also use the water bag according to the present invention more easily because the stiffness is increased in certain load directions. Easier usability can lead to one or more of the following: higher reproducibility of hyperthermia treatment between different treatment environments, better transfer of the predicted energy pattern to the patient, and better treatment results. In addition, faster setup of the hyperthermia device can be achieved, which can save time and enhance the patient's acceptance of the treatment.

[0050] Figure 1A The top view of a part of the hyperthermia device 100 is shown, where a part of the patient 200 is located inside the device 100. The hyperthermia device 100 includes two separate water sacs: the left water sac 102 and the right water sac 104, where left and right are as viewed by the patient. The left water sac 102 is arranged to cover a part of the outer surfaces of the head 202, neck 204, and larynx 205, which are the outer body surfaces of a body part. The right water sac 104 is arranged to cover the outer surfaces of the head 202 and neck 204 of the outer body surface as a body part. For the sake of brevity of description and because the functions of the two water sacs are similar, only the left water sac 102 will be discussed hereinafter and it will be referred to as the water sac 102. The water sac can be supported by a frame 112 included in the hyperthermia treatment device 100.

[0051] The radiation source included in the hyperthermia device 100 is not shown in the figure, and the radiation source is arranged to direct electromagnetic radiation through the water sac 102 towards the patient. In use, the water sac 102 will be disposed between the body part of the patient that will receive the electromagnetic radiation and the radiation source.

[0052] The water sac 102 includes a flexible cover 106 that forms a container 108 arranged to contain a fluid (such as water) and an insert 110 disposed inside the container, where the insert 100 is arranged to provide a first stiffness in a first load direction and a second stiffness in a second load direction, where the first stiffness is lower than the second stiffness, and the stiffness of the flexible cover is lower than the first stiffness.

[0053] Figure 1B The front view behind the head 202 of the hyperthermia device 100 and the patient 200 is shown. The left water sac 102 and the right water sac 104 surround the head 202, and for the clarity of the drawing, the left water sac 102 and the right water sac 104 are slightly moved outward away from the head 202. In use, the water sac 102 will be placed in contact with the patient's skin.

[0054] Figure 1B The overhanging part 114 of the water sac 102 is shown, and due to the weight of the water inside the water sac 102, the overhanging part 114 will tend to collapse in a direction opposite to the gravity g. In Figure 1B it, the internal shape 116 of the insert 110 is also visible, which corresponds to the outer body surface.

[0055] As can be seen from Figure 1A and Figure 1B it is preferable to expose at least some parts of the patient's face. This allows the patient to breathe through his nose and / or mouth, and preferably allows the patient's eyes to also remain exposed. The exposure increases the patient's comfort and reduces the feeling that the patient is confined inside the device.

[0056] Figure 2AA top view of a portion of the high heat device 100 is also shown, with a portion of the patient 200 located within the device 100. In the embodiment of the water bladder 102 as shown in Figure 2A , the insert 110 includes a plurality of connected, thin-walled, elongated, parallel hollow structures 114. In the embodiment of Figure 2A , the elongation direction 206 of the structure 114 is substantially parallel to the length of the patient 200 from head to toe. Embodiments of the insert are also envisioned where the elongation direction 206 is perpendicular to the length of the patient.

[0057] The cross-section of the elongated structure can be constant along the length of the structure and can have any shape, such as triangular, rectangular, square, circular, hexagonal, any other shape, or any combination thereof. Embodiments of the insert 110 including elongated structures with different cross-sections are also envisioned, and the cross-section of a structure need not be constant along the length of that structure.

[0058] Figure 2B A rear view of the head 202 of the patient 200 is shown, with the head 202 partially surrounded by the water bladder 102 and the water bladder 104. In Figure 2B , the elongation direction 206 extends within the plane of the paper. The structure 114 of the insert 110 is hexagonal in this embodiment. The structure 114 is arranged in the embodiment of Figure 2B such that two straight side planes of the hexagonal structure are substantially parallel to the direction of gravity g. Embodiments of the insert 110 are also envisioned where the structure 114 is rotated 90 degrees or any other angle in the elongation direction.

[0059] The hexagonal structure 114 provides a first stiffness in a first load direction, a second stiffness in a second load direction, and a third stiffness in a third load direction. The first load direction, represented by 221 in detail 220 of Figure 2B , can be a direction perpendicular to one of the planes included in the hexagon and can be substantially perpendicular to the direction of gravity g in use. The second load direction can be parallel to the elongation direction 206 of the hexagonal structure. The third load direction, represented by 223 in detail 220, can be a direction that is 90 degrees relative to the first load direction 221 about an axis parallel to the elongation direction 206. This corresponds to a load on the line where two planes of the hexagon intersect.

[0060] Depending on the material selection of the structure and the wall thickness of the structure, the first stiffness can be lower than the second stiffness, and the third stiffness can be higher than the first stiffness. Using this knowledge, a person skilled in the art can preferably position the structure within the water sac 102. To adjust the stiffness of the insert 110 in any direction, a person skilled in the art should understand the different ways of manipulating the properties of the structure (such as wall thickness, orientation, and cross-sectional shape) to achieve the desired stiffness in a certain direction and / or the ratio between different stiffnesses in different directions.

[0061] Figure 3A A portion of an embodiment of an insert 110 for a water sac is shown. The insert 110 includes a plurality of connected, thin-walled, elongated, parallel, hollow hexagonal structures 114. The internal shape 116 substantially corresponds to the external body surface represented by the dashed outline 302. Since the dashed outline 302 may not exactly correspond to the shape of the insert 110 made only of complete hexagonal structures, some structures are only partially provided as partial structures 304 that are present in only one, two, three, four, or five of the six possible planes.

[0062] Instead of using or in addition to using the partial structures 304, the insert 110 may include structures 114 having different cross-sectional shapes and / or dimensions. For example, to better follow the shape of the dashed outline 302, the insert 110 may include structures having a smaller cross-sectional surface near the internal shape 116. This allows the insert to include fewer partial structures 304 and thus include more complete structures. Additionally, for example, to better follow the shape of the dashed outline 302, one or more of the structures 114 may include a non-constant cross-sectional shape.

[0063] In addition to or as an alternative to the non-constant cross-sectional shape, one or more of the structures 114 included in the insert 110 may have a non-constant wall thickness. A locally higher wall thickness can increase the shape stability of the entire insert 110. In view of this, a person skilled in the art can easily understand how to adjust the wall thickness and / or cross-sectional shape of one or more of the structures 114 of the insert 110.

[0064] A first structure 306 and a second structure 308, which are adjacent structures, share a common plane 307 including a perforation 310. By means of the perforation 310, the first structure 306 and the second structure 308 are in fluid communication, and fluid can flow between the first structure 306 and the second structure 308 through the perforation 310. Any structure can include any number of perforations in any plane of the structure, such as any one of the six planes when the structure is formed as a hexagonal structure. For the sake of clarity and conciseness of the drawings, Figure 3A only one perforation 310 is shown in the figure.

[0065] Embodiments of insert 110 similar to those shown in Figure 3A are also envisioned, where the hexagonal structure 114 is rotated 90 degrees about the elongation direction 206, i.e., the flat sides of the hexagonal shape do not point up and down but rather left and right. Figure 3B Such an embodiment is shown in

[0066] Figure 3B The insert includes a plurality of connected, thin-walled, elongated, parallel, hollow, and hexagonal structures 114. Insert 110 also includes a plurality of perforations 310 disposed in the structures 114. As Figure 3B can be seen, a large number of perforations 310 can be provided on any and all planes of the hexagonal structure 114.

[0067] Insert 110 may also include a fluid inlet 322 and a fluid outlet 324. When filling the water bladder 102 with a fluid such as water, the fluid inlet 322 can be used, and the fluid inlet 322 can be used to drain the water bladder 102. Both the fluid inlet 322 and the fluid outlet 324 can be used for circulating water through the water bladder.

[0068] When the fluid inlet 322 is set below the fluid outlet 324 relative to gravity during use, filling the water bladder with fluid using the fluid inlet 322 allows air to escape the water bladder through the fluid outlet 324. When draining the water bladder, gravity will assist the fluid in leaving the water bladder through the lower fluid inlet 322.

[0069] Figure 4A A schematic view of a portion of the hyperthermia device 100 is shown to indicate an embodiment of how water, as an example of a fluid, flows through the water bladder 102. The hyperthermia device 100 also includes a pumping device 402 and an optional temperature regulator 404. The pumping device 402 is used to pump a liquid as a water flow through the water bladder 102, and the temperature regulator 404 is used to control the temperature of the water flowing through and to the water bladder 102. The temperature regulator 404 can be disposed downstream or upstream of the pumping device 402.

[0070] To receive the water flow, the water bladder 102 includes a fluid input 322, and to create a flow path towards the pumping device 402, the water bladder 102 also includes a fluid output 324. In Figure 4A the embodiment, the fluid input 322 and the fluid output 324 are disposed on the same side of the flexible cover 106 of the water bladder 102, which can be the first side.

[0071] Preferably, the fluid flow includes two directional components: a first flow direction 410 that substantially corresponds to the elongation direction 206 of the structure 114, and a second flow direction 412 that is perpendicular to the first flow direction 410. The flow in the first flow direction 410 allows passage through the hollow structure 114, and the flow in the second flow direction 412 allows passage through the plurality of perforations 310 indicated by the dashed lines.

[0072] In Figure 4A the embodiment of, the flow-through surface of the perforations 310 increases significantly from the first side 421 to the second side 422. Due to this increase, the fluid flow in the second flow direction 412 becomes easier the farther the flow is from the first side 421 where the pumping device 402 is provided. A more uniform fluid flow within the water bladder 102 can be achieved, and thus a more uniform temperature distribution within the water bladder 102 can also be achieved.

[0073] The perforations 310 of the structure can be aligned with the perforations 310 of the structure adjacent thereto in the second flow direction 412. Alternatively or additionally, some of the perforations 310 can be shifted, such as the exemplary shifted perforation 311, which is shifted along the first flow direction 410 relative to the other perforations 310. As Figure 4A is visible, such a shifted perforation 311 is not aligned with the perforations 310 of the structure adjacent thereto in the second direction 412. This misalignment can prevent the fluid from flowing directly through the vertically adjacent perforations 310 and increase the uniformity of the fluid flow and temperature within the water bladder 102.

[0074] The water bladder 102 can be provided with a fluid conduit 408 that extends substantially from the first side 421 to the second side 422 of the flexible cover 106. The fluid conduit 408 can shift the fluid output 324 from the first side 421 towards the second side 422. Due to this shift, the fluid flow can more easily reach the second side 422 of the water bladder 102 with a sufficient flow rate. Although the fluid conduit 408 can be partially provided outside the container 108, preferably the fluid conduit 408 extends through the container 108 to make the water bladder 102 compact.

[0075] As Figure 4B shown in the embodiment of a part of the hyperthermal device 100 substantially corresponds to the embodiment of a part of the hyperthermal device 100 as Figure 4A shown in. However, in Figure 4B the embodiment of, the average distance between adjacent perforations 310 decreases from the first side 421 to the second side 422. Due to this decrease in the average distance between adjacent perforations 310, the flow-through area provided for the fluid to flow in the second flow direction 412 is larger the farther the fluid flow is from the first side 421. This can also provide a more uniform fluid flow within the water bladder 102, and thus a more uniform temperature distribution within the water bladder 102.

[0076] Embodiments of the water bladder 102 are also envisioned in which the flow area of the perforations 310 increases from the first side 421 to the second side 422 and the average distance between adjacent perforations 310 decreases. This combination can even further provide a more uniform fluid flow within the water bladder 102 and thus an even more uniform temperature distribution within the water bladder 102.

[0077] In use, the first side 421 can correspond to the side pointed to by the top of the patient's head. Then, the second side 422 opposite the first side can correspond to the side of the patient's feet. In such embodiments, all fluid conduits can be provided outside the patient's field of view and out of reach.

[0078] In an embodiment of the water bladder 102, as Figure 4A and Figure 4B shown in, if the fluid inlet 322 and the fluid outlet 324 are interchangeable, the flow direction can be opposite to the flow direction described above herein.

[0079] Embodiments of the insert 110 are also envisioned in which the structure 114 is rotated 90 degrees relative to the Figure 4A and Figure 4B structure 114 shown in. Thus, fluid flow in the first flow direction 410 is allowed through the perforations 310, and fluid flow in the second flow direction 412 is allowed through the hollow structure 114.

[0080] Any embodiment of the insert 110 can be manufactured using 3D printing. This manufacturing technique allows for the design of the insert 110 with one side corresponding to the high heat device and the other side corresponding to the outer surface of the body part. The 3D model can first be composed of the body part, or the average model can be composed of multiple 3D models. Using such a body model, the internal shape 116 of the insert 110 can be determined for a specific patient or for an average set of patients. When using 3D printing, a CAD model can be used for the patient model and the insert 110 model.

[0081] Embodiments are also envisioned in which the insert 110 and the cover 106 are printed simultaneously, optionally as a single part. For this purpose, different 3D printing techniques known to those skilled in the art can be used, such as printing the cover 106 using a support material that can be dissolved and printing in a spiral, helix, or spiral bottle pattern.

[0082] Although the embodiments of this specification have been directed to the use of the water bladder in hyperthermia treatment of the head and neck regions, other applications of the water bladder according to the present invention are also envisioned even beyond hyperthermia treatment.

[0083] Examples of such applications are: temperature regulation, i.e. heating and / or cooling the outer surface of a human or animal body part. For example, heating or cooling the neck using a water bladder according to the invention can change the patient's temperature regulation by affecting the temperature of the thalamus. Skin cooling can also reduce the effect of a drug in the skin, and neck heating can stabilize the patient's temperature during anesthesia. A water bladder with increased shape stability can also be used in sports or physical therapy.

[0084] In medical applications other than hyperthermia treatment, a water bladder according to the invention can be placed between a medical device and a patient.

[0085] In summary, during hyperthermia treatment in the head and neck region, a conventional water bladder used in such treatments for guiding electromagnetic waves and cooling the patient's skin may collapse onto the patient's face due to the weight and / or pressure of the water inside the water bladder. An insert can be provided inside the water bladder to remedy this, where the insert provides additional stiffness and thus resists the weight and pressure of the water. However, the insert should not be too resistant to the shape of the patient, and thus, the insert provides a first stiffness in a first load direction and a second stiffness in a second load direction, where the first stiffness is not equal to the second stiffness.

[0086] In the above description, it should be understood that when an element such as a layer, region, or substrate is referred to as being "on" or "onto" another element, the element is directly on the other element, or intervening elements may also be present. Further, it should be understood that the values given in the above description are given by way of example, and other values may be possible and / or feasible.

[0087] In addition, the present invention can also be implemented with fewer components than those provided in the embodiments described herein, where one component performs multiple functions. The present invention can also be implemented with more elements than those depicted in the drawings, where the functions performed by one component in the provided embodiments are distributed among multiple components.

[0088] It should be noted that the drawings are only schematic illustrations of embodiments of the present invention given by way of non-limiting examples. For the purposes of clear and concise description, features are described herein as part of the same or separate embodiments, however, it should be understood that the scope of the present invention can include embodiments having combinations of all or some of the described features. The phrase "comprising" does not exclude the presence of other features or steps other than those listed in the claims. Further, the phrases "a" and "an" should not be construed as being limited to "only one", but are used to mean "at least one", and do not exclude a plurality.

[0089] Those skilled in the art should readily understand that various parameters and their values disclosed in the specification can be modified without departing from the scope of the present invention, and various embodiments disclosed and / or claimed can be combined.

[0090] The reference signs in the claims are stipulated not to limit the scope of the claims, but are inserted merely to enhance the readability of the claims.

Claims

1. A water bladder for covering a portion of an external body surface of a body part, comprising: - a flexible cover that forms a container arranged to hold a fluid; and - an insert disposed inside the container, wherein the insert is arranged to provide a first stiffness in a first load direction and a second stiffness in a second load direction, wherein the first stiffness is lower than the second stiffness, the stiffness of the flexible cover is lower than the first stiffness, and the insert has anisotropic stiffness.

2. The water bladder according to claim 1, wherein an inner surface of the insert is complementary to the external body surface, and the first load direction is oriented substantially orthogonally to the inner surface of the insert for most of the inner surface.

3. The water bladder according to claim 1, wherein the insert comprises a plurality of connected, thin-walled, elongated, parallel hollow structures.

4. The water bladder according to claim 3, wherein the second load direction is oriented substantially parallel to the elongation direction of the hollow structures, and the first load direction is substantially perpendicular to the elongation direction of the hollow structures.

5. The water bladder according to claim 3, wherein the hollow structures are arranged as elongated hexagonal structures.

6. The water bladder according to claim 5, wherein the insert is arranged to provide a third stiffness in a third load direction, wherein the third load direction is substantially perpendicular to the elongation direction of the hollow structures and is oriented at an angle of approximately 90 degrees relative to the first load direction, and wherein the third stiffness is higher than the first stiffness.

7. The water bladder according to claim 6, wherein in use, the third load direction is a substantially vertical direction, and the first load direction is a substantially horizontal direction.

8. The water bladder according to claim 1, wherein the container comprises a fluid inlet for receiving fluid and a fluid outlet for releasing fluid, such that fluid flow can be provided between the fluid inlet and the fluid outlet within the container.

9. The water bladder according to claim 8, wherein the first of the fluid inlet and the fluid outlet is provided on a first side of the flexible cover, and the second of the fluid inlet and the fluid outlet is provided by a fluid conduit extending substantially from the first side of the flexible cover to a second side opposite the first side.

10. The water bladder according to claim 9, wherein the fluid conduit extends through the container.

11. The water bladder according to claim 3, wherein the hollow structures comprise a plurality of perforations such that the hollow interiors of adjacent hollow structures are in fluid communication with each other.

12. The water bladder according to claim 11, wherein: - the container comprises a fluid inlet for receiving fluid and a fluid outlet for releasing fluid, such that fluid flow can be provided between the fluid inlet and the fluid outlet within the container; - The first of the fluid input portion and the fluid output portion is disposed on a first side of the flexible cover, and the second of the fluid input portion and the fluid output portion is provided by a fluid conduit that extends substantially from the first side of the flexible cover to a second side opposite the first side; - The fluid is arranged to flow from the first side to the second side within the water bladder; and - The perforated flow surface increases significantly from the first side to the second side.

13. The water bladder according to claim 11, wherein the first perforations are arranged to be misaligned with the second perforations with respect to the elongation direction.

14. The water bladder according to claim 11, wherein: - The container includes a fluid input portion for receiving fluid and a fluid output portion for releasing fluid, such that fluid flow can be provided between the fluid input portion and the fluid output portion within the container; - The first of the fluid input portion and the fluid output portion is disposed on a first side of the flexible cover, and the second of the fluid input portion and the fluid output portion is provided by a fluid conduit that extends substantially from the first side of the flexible cover to a second side opposite the first side; - The fluid is arranged to flow from the first side to the second side within the water bladder, the perforations are spaced apart, and the average distance between adjacent perforations increases from the first side to the second side.

15. The water bladder according to claim 3, wherein one or more structures included in the insert have a non-constant wall thickness.

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