WO2011107645A1 - Sensor no invasivo para determinar características funcionales de la córnea, dispositvo que incluye dicho sensor y su uso - Google Patents
Sensor no invasivo para determinar características funcionales de la córnea, dispositvo que incluye dicho sensor y su uso Download PDFInfo
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- WO2011107645A1 WO2011107645A1 PCT/ES2011/070131 ES2011070131W WO2011107645A1 WO 2011107645 A1 WO2011107645 A1 WO 2011107645A1 ES 2011070131 W ES2011070131 W ES 2011070131W WO 2011107645 A1 WO2011107645 A1 WO 2011107645A1
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- microelectrodes
- sensor according
- impedance
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Classifications
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/053—Measuring electrical impedance or conductance of a portion of the body
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/05—Detecting, measuring or recording for diagnosis by means of electric currents or magnetic fields; Measuring using microwaves or radio waves
- A61B5/053—Measuring electrical impedance or conductance of a portion of the body
- A61B5/0537—Measuring body composition by impedance, e.g. tissue hydration or fat content
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B5/00—Measuring for diagnostic purposes; Identification of persons
- A61B5/68—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient
- A61B5/6801—Arrangements of detecting, measuring or recording means, e.g. sensors, in relation to patient specially adapted to be attached to or worn on the body surface
- A61B5/6813—Specially adapted to be attached to a specific body part
- A61B5/6814—Head
- A61B5/6821—Eye
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/02—Details of sensors specially adapted for in-vivo measurements
- A61B2562/0209—Special features of electrodes classified in A61B5/24, A61B5/25, A61B5/283, A61B5/291, A61B5/296, A61B5/053
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/04—Arrangements of multiple sensors of the same type
- A61B2562/043—Arrangements of multiple sensors of the same type in a linear array
-
- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61B—DIAGNOSIS; SURGERY; IDENTIFICATION
- A61B2562/00—Details of sensors; Constructional details of sensor housings or probes; Accessories for sensors
- A61B2562/16—Details of sensor housings or probes; Details of structural supports for sensors
- A61B2562/166—Details of sensor housings or probes; Details of structural supports for sensors the sensor is mounted on a specially adapted printed circuit board
Definitions
- the object of the present invention relates to a sensor and a device incorporating said sensor for obtaining non-invasively, data useful for the diagnosis of the condition of the cornea.
- it is a device that allows the impedance of the cornea to be measured at different frequencies to establish a correlation between the impedance and permeability of the endothelium and epithelium and the level of hydration of the stroma, in order to determine the functional characteristics of the cornea
- the cornea is the transparent hemispheric structure located in front of the ocular organ, which allows the passage of light and protects the iris and lens. It has the shape of a spherical cap with an average diameter in the human of 1 1.5 mm and has significant optical refractive properties, providing approximately 70% of the total focusing capacity of the eye.
- the cornea consists of three layers; the most external is the corneal epithelium, composed of non-keratinized pluriestratified epithelium with great regenerative potential; the mean is the stroma, the widest layer of the three; and the most internal is the monostratified endothelium consisting of a single layer of cells.
- the epithelium represents 10% of the total thickness of the cornea (550 ⁇ approximately in the human) and is formed by several cell layers that act as a protective barrier to external agents.
- the transport of ions through the cells of the epithelial layer is one of those responsible for regulating corneal functionality.
- the stroma is formed in humans by about 200-250 collagen fiber sheets arranged parallel to the corneal surface.
- the stroma is ultimately responsible for the biomechanical properties of the cornea, as well as its curvature and its transparency. To maintain its transparency it does not have capillaries to nourish it, so that nutrients are supplied through the epithelium and endothelium.
- the degree of hydration of the stroma is directly related to the transparency of the cornea, remaining in a continuous state of dehydration.
- the endothelium consists of a monolayer of cuboid cells that form a hexagonal mosaic and maintains tissue transparency by controlling stromal hydration.
- endothelial cells are specialized in pumping water from the stroma to the aqueous humor, creating an active flow through the fluidic pump and ensuring homeostasis of the cornea.
- a characteristic of the corneal endothelium, unlike the epithelium, is its inability for cell renewal.
- Figure 1 shows the different layers that make up the cornea, as well as the main mechanisms of control of the level of hydration of the stroma: diffusion through the epithelium, diffusion and pumping through the endothelium.
- the study of the passive electrical properties of the different layers of the cornea is usually used in in-vitro studies to evaluate their permeability. But the methods used in these studies are not applicable to in-vivo measures.
- the cellular and acellular media have a different behavior against the electric current.
- tissues are composed of cells embedded in an extracellular medium. At low frequencies, ⁇ 1 kHz, the current is distributed through the extracellular medium (primarily an ionic solution with resistive behavior), while at higher frequencies,> 100 kHz, the current is able to pass through the cell walls and the intracellular medium (the behavior of the membranes is capacitive and the intracellular medium is resistive).
- Fig. 2 graphically depicts this difference in behavior as a function of frequency. Based on this behavior of the biological tissues, the state of the different layers of the cornea can be analyzed using measurements based on the passive electrical properties of the cornea, as is the case with the impedance measurements.
- the present invention provides an impedance measurement sensor useful for determining the functional characteristics of the cornea, as well as a device comprising said sensor.
- a first aspect of the invention relates to an impedance measurement sensor comprising n microelectrodes, being between 4 and 30, arranged on a substrate, the size and arrangement of the microelectrodes being suitable for simultaneous contact. with a cornea, and where the microelectrodes are selected to perform the measurement in groups of 4 by way of 2 external microelectrodes and 2 internal microelectrodes.
- a second aspect of the present invention relates to an impedance measuring device comprising a sensor as described above and a multi-frequency impedance measuring device connected either physically by wires or by telemetry to said sensor.
- a third aspect of the invention relates to the use of a sensor or a device comprising said sensor as described above for the measurement of impedance to determine the functional characteristics of the cornea.
- microelectrodes refers to microelectrodes that only require contact with the surface of the cornea to perform the impedance measurement.
- size and configuration suitable for simultaneous contact with a cornea refers to the fact that, in order to correctly measure the impedance, all the microelectrodes used must make electrical contact with the cornea, which implies size limitations and relative arrangement of microelectrodes.
- the sensor of the invention is connected to the impedance measurement equipment. These equipments work by injecting an electric current into the medium whose impedance is desired to be measured through the microelectrodes, simultaneously obtaining the resulting electrical potential through other microelectrodes. From this data, the impedance of the tissue is calculated.
- the impedance measuring equipment incorporates means for injecting an electric current of variable frequency in the cornea and means for simultaneous reading of the resulting potential, thus obtaining data of the tissue impedance for a multi-frequency measurement in the range of 10 Hz to 1 MHz
- the measurements carried out in different frequency ranges and with the appropriate microelectrodes give rise to impedance values that allow conclusions about the functional status of the different layers of the cornea.
- the measured conductivity basically depends on the conductivity of the epithelial layer. Due to its low conductivity at low frequencies, the amount of electrical current that can pass through it is practically zero, so that the voltage drop recorded depends on the conductivity of the corneal epithelium.
- the analysis of the impedance measurement is more complex, as several factors are involved.
- the conductivity of the cell layers is two orders of magnitude greater than that of the other layers, allowing the passage of a significant amount of current to the acellular layers (stroma and aqueous humor).
- the conductivity of the aqueous humor is higher than that of the stroma, so the electric current will tend to circulate through this layer.
- the amount of current that can pass through the endothelium and circulate with aqueous humor is directly related to the conductivity of the endothelium, and in turn with its permeability. Consequently, if the current flowing through the aqueous humor increases, the recorded impedance drops, which indicates an increase in the permeability of the endothelium.
- the electric current is able to pass through cells, so that the measurement of the impedance depends on the conductivity of the stroma and the aqueous humor, as they are the largest layers.
- the conductivity of the aqueous humor can be considered constant, so that the variations in the measured impedance are related to the Stromal conductivity variations, and these in turn with their degree of hydration.
- the microelectrodes are arranged planarly on the substrate.
- the sensor comprises 10 microelectrodes.
- the conductive microelectrodes may be of metallic or non-metallic material, preferably of a biocompatible material.
- the microelectrodes are of metallic material selected from gold, platinum, nickel, aluminum, titanium, titanium nitride, chromium and possible alloys thereof;
- the microelectrodes are of non-metallic material selected from carbon nanotubes, graphene and conductive polymers. These microelectrodes can be modified by processes that improve their performance.
- carbon nanotubes can be deposited or electro-deposited black platinum or gold to improve tissue contact and hydrogels such as polyhydroxymethylmethacrylate (pHEMA) can be deposited to stabilize the above processes.
- said microelectrodes have an elongated shape and are arranged in parallel according to their longer side, the microelectrodes being configured either to inject an electric current or to measure a potential.
- the substrate on which the microelectrodes are arranged is constituted by a biocompatible material and can be rigid or flexible, preferably transparent, which allows the person making the measurement Observe whether the microelectrodes are making contact with the surface of the cornea.
- a rigid substrate can be essentially flat or have an angle of curvature that allows its adaptation on the surface of the cornea.
- the material is selected from silicon, silicon carbide, glass and PCB (printed circuit board, RF4).
- the material is selected from polymers such as: SU8, polymethylmethacrylate (PMMA), polydimethylsiloxane (PDMS), polyimide, polyethylene naphthalate (PEN), polyethylene terephthalate (PET), polystyrene, cycloolefin polymer (COP ) and polycarbonate.
- the substrate is rigid and the microelectrodes have a length of 2 mm and a width of 0.3 mm.
- the substrate is flexible and the microelectrodes have a length of 1 mm and a width of 0.3 mm
- Figure 3A shows a diagram of the different layers that define the sensor, the substrate and the microelectrodes.
- the sensor can be adapted in different ways for its implementation to perform the impedance measurements.
- the possibility of manufacturing the sensor in the form of a lens, the adaptation of the sensor to a support or a container that may contain insulated corneas is contemplated.
- the measured impedance values depend on the geometry of the microelectrodes used. In the same way the contribution of the electrical properties of each layer of the cornea to the total impedance measured is different. It can be said that the layers closest to the microelectrodes have a higher sensitivity, so that a variation in their electrical properties will cause a greater variation in the total impedance. In this way, the depth of the measurement performed depends on the relative distance between the microelectrodes.
- the sensor of the present invention has the advantage that the measurement of the impedance of the cornea at different frequencies to establish a correlation between the impedance and permeability of the endothelium and epithelium and the level of hydration of the stroma, it can be determined with the use of the same sensor described above by conveniently combining four microelectrodes of the various present in the sensor, since it allows modulating the amplitude of the relative distance between them.
- Figure 3B shows how the use of different microelectrodes allows the permeability of the different layers of the cornea to be determined. The design and use of the microelectrodes complies with certain parameters.
- Fig. 4 schematizes these parameters in a sensor formed by ten microelectrodes.
- the microelectrodes are of equal length and width and are arranged parallel with 2 external microelectrodes I-) and 2 internal microelectrodes (V +, V-), and the arrangement of the microelectrodes as external (V +, V-) may also be feasible.
- 2 internal microelectrodes see Fig. 5.
- Ws is the width of the set of electrodes selected to measure or distance between the midlines of the external microelectrodes, and is between 0.2 mm and 11 mm.
- the preferred value of this parameter depends on the layer from which Information is desired, with 5 mm being for the endothelial layer, 1 mm for the epithelium and 1.8 mm for the stroma.
- each layer of the cornea correlates with the measurement of the corneal impedance as a function of the width of the selected electrode set (Ws) and the frequency at which the measure.
- Ws selected electrode set
- Figure 1 shows schematically the different layers that make up the (tear, cell epithelium, acellular stroma, cell endothelium and aqueous humor) and the main mechanisms of control of the level of hydration of the stroma.
- a continuous line the flow is shown by diffusion of aqueous humor to the stroma through the endothelium
- in a broken line the flow is shown by pumping of the stroma to aqueous humor through the endothelium
- in a semi-discontinuous line the flow is shown by diffusion of the tear to the stroma through the epithelium.
- Figure 2 schematically shows the behavior of electric current at different frequencies when crossing cell layers.
- the low frequencies, ⁇ 1 kHz, are represented in a broken line, and it is observed that the current is distributed through the extracellular medium.
- the high frequencies,> 100 kHz, are shown in a continuous line, and it is observed that the current flows through the cell wall and the intracellular medium.
- Figure 3A shows a diagram of the different layers that define the sensor, the substrate and the microelectrodes.
- Figure 3B exemplifies how the use of the same sensor conveniently combining several microelectrodes of the various present in the sensor, allows the penetration of the current to the different layers of the cornea.
- Figure 4 shows the example of a sensor with 10 microelectrodes, where the different parameters of the sensor geometry are defined: We, width of the microelectrode; You; microelectrode length; Ws, width of the set of microelectrodes selected to perform the measurement; Se, distance between the midlines of an internal microelectrode and the nearest external microelectrode; Sei, distance between the midlines of the internal microelectrodes.
- Figure 5 shows an example of a sensor formed by four microelectrodes arranged on a substrate, detailing the two external microelectrodes ( ⁇ +, I-) and the two internal microelectrodes (V +, V-) to perform an impedance measurement at four points .
- a sensor with 10 gold microelectrodes deposited on a glass substrate was used.
- an insulating layer of Si0 2 - S ⁇ 3N 4 300 nm + 700 nm.
- the shape of the microelectrodes and the insulating layer were made by standard photolithography processes in microtechnology processes.
- a microelectrode configuration with a Ws of 1 mm and an Nre of 3 was selected.
- the impedance team injected a current of 10 uA at 100 Hz between the external microelectrodes and recorded the potential drop in the internal microelectrodes, obtaining the measurement of the impedance of the cornea.
- the measurement obtained at 100 Hz was 10 ⁇ ⁇ 2 ⁇ in the case of a healthy cornea and 4 ⁇ ⁇ 1 ⁇ in the case of a cornea with the altered epithelial layer.
- a microelectrode configuration with a Ws of 5 mm and an Nre of 3 was selected to detect alterations in the endothelial layer, obtaining a 10 kHz measurement of 2 ⁇ ⁇ 0.5 ⁇ for a healthy cornea and a measurement of 200 ⁇ ⁇ 100 ⁇ for a cornea with the altered endothelial layer.
- the increase in stromal hydration was measured due to the increase in corneal endothelial permeability.
- a microelectrode configuration with a Ws of 1.8 mm and an Nre of 3 was selected, obtaining a measurement at 1 MHz of 250 ⁇ ⁇ 20 ⁇ for a healthy cornea and a measurement of 80 ⁇ ⁇ 20 ⁇ for a cornea with the altered stromal layer.
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- Animal Behavior & Ethology (AREA)
- Veterinary Medicine (AREA)
- Biophysics (AREA)
- Pathology (AREA)
- Engineering & Computer Science (AREA)
- Biomedical Technology (AREA)
- Heart & Thoracic Surgery (AREA)
- Public Health (AREA)
- Molecular Biology (AREA)
- Surgery (AREA)
- Physics & Mathematics (AREA)
- General Health & Medical Sciences (AREA)
- Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
- Radiology & Medical Imaging (AREA)
- Ophthalmology & Optometry (AREA)
- Measurement And Recording Of Electrical Phenomena And Electrical Characteristics Of The Living Body (AREA)
- Eye Examination Apparatus (AREA)
- Investigating Or Analyzing Materials By The Use Of Electric Means (AREA)
- Ultra Sonic Daignosis Equipment (AREA)
- Measurement Of Resistance Or Impedance (AREA)
Abstract
Description
Claims
Priority Applications (10)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP11750233.6A EP2543310A4 (en) | 2010-03-02 | 2011-02-28 | NONINVASIVE SENSOR FOR DETERMINING HORNIAL FUNCTIONAL PROPERTIES, DEVICE WITH THIS SENSOR AND USE THEREOF |
BR112012020485A BR112012020485A2 (pt) | 2010-03-02 | 2011-02-28 | sensor e dispositivo para medição de impedância, e uso dos mesmos |
MX2012010091A MX2012010091A (es) | 2010-03-02 | 2011-02-28 | Sensor no invasivo para determinar caracteristicas funcionales de la cornea, dispositivo que incluye dicho sensor y su uso. |
KR1020127025364A KR20130037666A (ko) | 2010-03-02 | 2011-02-28 | 각막의 기능적인 특성을 결정하기 위한 비외과적인 센서, 상기 센서를 포함하는 장치, 및 그 용도 |
AU2011222850A AU2011222850C1 (en) | 2010-03-02 | 2011-02-28 | Non-invasive sensor for determining functional characteristics of the cornea, device including said sensor and use thereof |
CN201180009959.6A CN102762145B (zh) | 2010-03-02 | 2011-02-28 | 用于测定角膜的功能特性的非侵入式传感器、包含该传感器的装置及其应用 |
JP2012555452A JP5925700B2 (ja) | 2010-03-02 | 2011-02-28 | 角膜の機能特性を明らかにするための非侵襲センサ、該センサを備える装置、および該装置の使用 |
CA2789203A CA2789203A1 (en) | 2010-03-02 | 2011-02-28 | Non-invasive sensor for determining functional characteristics of the cornea, device including said sensor and use thereof |
RU2012141892/14A RU2576370C2 (ru) | 2010-03-02 | 2011-02-28 | Неинвазивный датчик для определения функциональных характеристик роговицы, устройство, содержащее упомянутый датчик, и его применение |
US13/581,994 US8948840B2 (en) | 2010-03-02 | 2011-02-28 | Non-invasive sensor for determining functional characteristics of the cornea, device including said sensor and use thereof |
Applications Claiming Priority (2)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
ES201030307A ES2372082B1 (es) | 2010-03-02 | 2010-03-02 | Sensor no invasivo para determinar características funcionales de la córnea y dispositivo que incluye dicho sensor. |
ESP201030307 | 2010-03-02 |
Publications (1)
Publication Number | Publication Date |
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WO2011107645A1 true WO2011107645A1 (es) | 2011-09-09 |
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PCT/ES2011/070131 WO2011107645A1 (es) | 2010-03-02 | 2011-02-28 | Sensor no invasivo para determinar características funcionales de la córnea, dispositvo que incluye dicho sensor y su uso |
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EP (1) | EP2543310A4 (es) |
JP (1) | JP5925700B2 (es) |
KR (1) | KR20130037666A (es) |
CN (1) | CN102762145B (es) |
AR (1) | AR084671A1 (es) |
BR (1) | BR112012020485A2 (es) |
CA (1) | CA2789203A1 (es) |
ES (1) | ES2372082B1 (es) |
MX (1) | MX2012010091A (es) |
RU (1) | RU2576370C2 (es) |
TW (1) | TWI548392B (es) |
UY (1) | UY33257A (es) |
WO (1) | WO2011107645A1 (es) |
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US8690331B2 (en) * | 2011-08-29 | 2014-04-08 | The Regents Of The University Of California | Corneal hydration sensing system |
US8989834B2 (en) | 2012-09-25 | 2015-03-24 | Google Inc. | Wearable device |
US9861288B2 (en) * | 2014-07-11 | 2018-01-09 | Wisconsin Alumni Research Foundation | Transparent and flexible neural electrode arrays |
RU179826U1 (ru) * | 2017-11-07 | 2018-05-24 | Федеральное государственное автономное образовательное учреждение высшего образования "Волгоградский государственный университет" | Лазерный триангуляционный измеритель толщины роговицы и остаточных роговичных слоев глаза |
RU191566U1 (ru) * | 2019-03-07 | 2019-08-13 | Антон Андреевич Адамов | Лазерный триангуляционно-интерферометрический измерительный комплекс оптических характеристик прозрачных биологических тканей и плёнок |
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2010
- 2010-03-02 ES ES201030307A patent/ES2372082B1/es not_active Expired - Fee Related
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2011
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- 2011-02-28 CA CA2789203A patent/CA2789203A1/en not_active Abandoned
- 2011-02-28 RU RU2012141892/14A patent/RU2576370C2/ru not_active IP Right Cessation
- 2011-02-28 EP EP11750233.6A patent/EP2543310A4/en not_active Withdrawn
- 2011-02-28 KR KR1020127025364A patent/KR20130037666A/ko not_active Application Discontinuation
- 2011-02-28 BR BR112012020485A patent/BR112012020485A2/pt not_active IP Right Cessation
- 2011-02-28 JP JP2012555452A patent/JP5925700B2/ja not_active Expired - Fee Related
- 2011-02-28 WO PCT/ES2011/070131 patent/WO2011107645A1/es active Application Filing
- 2011-02-28 MX MX2012010091A patent/MX2012010091A/es active IP Right Grant
- 2011-02-28 US US13/581,994 patent/US8948840B2/en not_active Expired - Fee Related
- 2011-03-02 AR ARP110100643A patent/AR084671A1/es unknown
- 2011-03-02 TW TW100106958A patent/TWI548392B/zh active
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Also Published As
Publication number | Publication date |
---|---|
AU2011222850A1 (en) | 2012-10-11 |
CA2789203A1 (en) | 2011-09-09 |
US8948840B2 (en) | 2015-02-03 |
UY33257A (es) | 2011-09-30 |
EP2543310A1 (en) | 2013-01-09 |
US20130012803A1 (en) | 2013-01-10 |
CN102762145B (zh) | 2015-02-25 |
TW201134452A (en) | 2011-10-16 |
RU2012141892A (ru) | 2014-04-10 |
JP2013521034A (ja) | 2013-06-10 |
CN102762145A (zh) | 2012-10-31 |
ES2372082B1 (es) | 2013-01-30 |
MX2012010091A (es) | 2012-09-21 |
TWI548392B (zh) | 2016-09-11 |
KR20130037666A (ko) | 2013-04-16 |
AR084671A1 (es) | 2013-06-05 |
EP2543310A4 (en) | 2014-02-26 |
ES2372082A1 (es) | 2012-01-13 |
RU2576370C2 (ru) | 2016-02-27 |
BR112012020485A2 (pt) | 2016-05-17 |
AU2011222850B2 (en) | 2015-10-29 |
JP5925700B2 (ja) | 2016-05-25 |
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