RELATED APPLICATION

This application claims the benefit of priority of U.S. Provisional Patent Application Nos. 62/218,026 and 62/218,020, both filed on September 14, 2015, the contents of which are incorporated herein by reference in their entirety.

FIELD AND BACKGROUND OF THE INVENTION

The present invention, in some embodiments thereof, relates to data analysis and, more particularly, but not exclusively, to a method and system for correcting image data, preferably using a universal function.

The use of imaging in medicine is known. Presently there are numerous different imaging modalities at the disposal of a physician allowing imaging of hard and soft tissues and characterization of both normal and pathological tissues. For example, infra red imaging is utilized for characterizing a thermally distinguishable site in a human body for the purposes of identifying inflammation. Infrared cameras produce two- dimensional images known as thermographic images. A thermographic image is typically obtained by receiving from the body of the subject radiation at any one of several infrared wavelength ranges and analyzing the radiation to provide a two- dimensional temperature map of the surface. The thermographic image can be in the form of either or both of a visual image and corresponding temperature data. The output from infrared cameras used for infrared thermography typically provides an image comprising a plurality of pixel data points, each pixel providing temperature information which is visually displayed, using a color code or grayscale code. The temperature information can be further processed by computer software to generate for example, mean temperature for the image, or a discrete area of the image, by averaging temperature data associated with all the pixels or a sub-collection thereof.

Based on the thermographic image, a physician diagnoses the site, and determines, for example, whether or not the site includes an inflammation while relying heavily on experience and intuition.

International Patent Publication No. 2006/003658, the contents of which are hereby incorporated by reference, discloses a system which includes non-thermographic image data acquisition functionality and thermographic image data acquisition functionality. The non-thermographic image data acquisition functionality acquires non- thermographic image data, and the thermographic image data acquisition functionality acquires thermographic image data.

U.S. Patent No. 7,292,719, the contents of which are hereby incorporated by reference discloses a system for determining presence or absence of one or more thermally distinguishable objects in a living body. A combined image generator configured combines non-thermographic three-dimensional data of a three-dimensional tissue region in the living body with thermographic two-dimensional data of the tissue region so as to generate three-dimensional temperature data associated with the three- dimensional tissue region.

SUMMARY OF THE INVENTION

According to some embodiments of the invention there is provided a method of correcting image data. The method comprises obtaining at least one 3D thermospatial representation having 3D spatial data representing a non-planar surface of a portion of a living body and thermal data associated with the 3D spatial data; based on the spatial data, calculating a viewing angle for each of a plurality of picture-elements over the thermospatial representation; and for each of at least some of the picture-elements, applying a predetermined correction function which describes a dependence of a correction of the thermal data on the viewing angle, for correcting thermal data associated with the picture-element.

According to some embodiments of the invention the predetermined correction function is stored in a non-transitory computer readable medium as a lookup table.

According to some embodiments of the invention the obtaining the at least one

3D thermospatial representation comprises obtaining two or more 3D thermospatial representations of the same portion of the living body, and wherein the applying the predetermined correction function is repeated for at least two of the two or more 3D thermospatial representations, each time using the same predetermined correction function. According to some embodiments of the invention the method comprises determining presence or absence of a thermally distinguished region in the portion of the living body based on the corrected thermal data.

According to some embodiments of the invention the method comprises determining whether or not the thermally distinguished region is a tumor based on a predetermined criterion or a predetermined set of criteria.

According to some embodiments of the invention the portion of the living body is a breast of a human subject.

According to some embodiments of the invention the method comprises re- generating the at least one 3D thermospatial representation using the corrected thermal data.

According to some embodiments of the invention the method comprises displaying the re-generated 3D thermospatial representation on a display and/or transmitting the re-generated 3D thermospatial representation to a non-transitory computer readable medium.

According to some embodiments of the invention the method comprises generating a temperature map of the portion of the body using the corrected thermal data.

According to some embodiments of the invention the method comprises displaying the temperature map on a display and/or transmitting the temperature map to a non-transitory computer readable medium.

According to an aspect of some embodiments of the present invention there is provided a computer software product. The product comprises a non-transitory computer-readable medium in which program instructions are stored, which instructions, when read by a data processor, cause the data processor to receive at least one 3D thermospatial representation of a portion of a living body and execute the method as delineated above and optionally and preferably as further exemplified below.

According to an aspect of some embodiments of the present invention there is provided an image correction system. The system comprises: a digital input for receiving at least one 3D thermospatial representation having 3D spatial data representing a non- planar surface of a portion of a living body and thermal data associated with the 3D spatial data; and a data processor configured for calculating, based on the spatial data, a viewing angle for each of a plurality of picture-elements over the thermospatial representation, and for applying, for each of at least some of the picture-elements, a predetermined correction function which describes a dependence of a correction of the thermal data on the viewing angle, for correcting thermal data associated with the picture-element.

According to some embodiments of the invention the predetermined correction function is nonlinear with respect to the angle.

According to some embodiments of the invention the predetermined correction function comprises a quadratic function.

According to some embodiments of the invention the system comprises a non- transitory computer readable medium, wherein the predetermined correction function is stored in the computer readable medium as a lookup table.

According to some embodiments of the invention the input receives two or more 3D thermospatial representations of the same portion of the living body, and wherein the data processor is configured for applying the predetermined correction function separately for at least two of the two or more 3D thermospatial representations, each time using the same predetermined correction function.

According to some embodiments of the invention the data processor is configured for determining presence or absence of a thermally distinguished region in the portion of the living body based on the corrected thermal data.

According to some embodiments of the invention the data processor is configured for determining whether or not the thermally distinguished region is a tumor based on a predetermined criterion or a predetermined set of criteria.

According to some embodiments of the invention the system comprises an image generator for re-generating the at least one 3D thermospatial representation using the corrected thermal data.

According to some embodiments of the invention the system comprises at least one of a display for displaying the re-generated 3D thermospatial representation, and a non-transitory computer readable medium for storing the re-generated 3D thermospatial representation. According to some embodiments of the invention the system comprises an image generator for generating a temperature map of the portion of the body using the corrected thermal data.

According to some embodiments of the invention the system comprises at least one of a display for displaying the temperature map, and a non-transitory computer readable medium for storing the temperature map.

According to an aspect of some embodiments of the present invention there is provided an imaging system. The imaging system comprises: a thermospatial generator for generating a 3D thermospatial representation of a portion of a living body, the 3D thermospatial representation having 3D spatial data representing a non-planar surface of the portion of the living body and thermal data associated with the 3D spatial data; and the image correction system as delineated above and optionally and preferably as further exemplified below.

Unless otherwise defined, all technical and/or scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the invention pertains. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of embodiments of the invention, exemplary methods and/or materials are described below. In case of conflict, the patent specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be necessarily limiting.

Implementation of the method and/or system of embodiments of the invention can involve performing or completing selected tasks manually, automatically, or a combination thereof. Moreover, according to actual instrumentation and equipment of embodiments of the method and/or system of the invention, several selected tasks could be implemented by hardware, by software or by firmware or by a combination thereof using an operating system.

For example, hardware for performing selected tasks according to embodiments of the invention could be implemented as a chip or a circuit. As software, selected tasks according to embodiments of the invention could be implemented as a plurality of software instructions being executed by a computer using any suitable operating system. In an exemplary embodiment of the invention, one or more tasks according to exemplary embodiments of method and/or system as described herein are performed by a data processor, such as a computing platform for executing a plurality of instructions. Optionally, the data processor includes a volatile memory for storing instructions and/or data and/or a non-volatile storage, for example, a magnetic hard-disk and/or removable media, for storing instructions and/or data. Optionally, a network connection is provided as well. A display and/or a user input device such as a keyboard or mouse are optionally provided as well.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Some embodiments of the invention are herein described, by way of example only, with reference to the accompanying drawings and images. With specific reference now to the drawings in detail, it is stressed that the particulars shown are by way of example and for purposes of illustrative discussion of embodiments of the invention. In this regard, the description taken with the drawings makes apparent to those skilled in the art how embodiments of the invention may be practiced.

In the drawings:

FIGs. 1A-C are schematic illustrations of a synthesized thermospatial image, according to some embodiments of the present invention;

FIG. 2 is a flowchart diagram of a method suitable for correcting image data, according to some embodiments of the present invention;

FIG. 3 is a graph of measured temperatures of several points on a human's skin as a function of angle between the normal to skin and the optical axis of a thermal camera;

FIG. 4 is a schematic illustration of an image correction system, according to some embodiments of the present invention;

FIG. 5 shows experimental results in which thermal data of images were corrected in accordance with some embodiments of the present invention;

FIG. 6 is a thermographic image obtained during experiments performed according to some embodiments of the present invention;

FIGs. 7A and 7B are visible light images from the two different viewing angles, obtained during experiments performed according to some embodiments of the present invention; FIG. 7C shows registration of the images of FIGs. 7 A and 7B, obtained during experiments performed according to some embodiments of the present invention;

FIG. 7D shows picture-elements for which a registration difference calculated during experiments performed according to some embodiments of the present invention was less than 2 mm;

FIGs. 7E and 7F show grey level differences between thermal images before (FIG. 7E) and after (FIG. 7F) thermal data correction performed according to some embodiments of the present invention;

FIG. 7G shows difference between the absolute values of the images in FIGs. 7E and 7F; and

FIG. 7H shows regions at which the thermal correction of the present embodiments provides improvement.

DESCRIPTION OF SPECIFIC EMBODIMENTS OF THE INVENTION

The present invention, in some embodiments thereof, relates to data analysis and, more particularly, but not exclusively, to a method and system for correcting image data, preferably using a universal function.

Before explaining at least one embodiment of the invention in detail, it is to be understood that the invention is not necessarily limited in its application to the details of construction and the arrangement of the components and/or methods set forth in the following description and/or illustrated in the drawings and/or the Examples. The invention is capable of other embodiments or of being practiced or carried out in various ways.

The present inventors have devised an approach which enables the correction of image data. It was found by the present inventors that corrected image data according to some embodiments of the present invention can be used to determine presence or absence of one or more distinguishable regions in a portion of a body, more preferably a living body. Preferably, the technique of the present embodiments is applied for correcting thermal data, which can include temperature data or some proxy thereof, such as, but not limited to, grayscale data and/or wavelength data.

In some embodiments of the present invention, the corrected thermal data is used for determining the likelihood for the presence of a thermally distinguishable region in the portion of the body. When the thermal image is of a portion of a living body such as a breast of a male or female subject, the analysis of the present embodiments can be used to extract properties of the underlying tissue. For example, determination of the likelihood that a thermally distinguished region is present in the portion of the body can be used for assessing whether or not the portion of the body has a pathology such as a tumor or an inflammation.

An elevated temperature is generally associated with a tumor due to the metabolic abnormality of the tumor and proliferation of blood vessels (angiogenesis) at and/or near the tumor. In a cancerous tumor the cells proliferate faster and thus are more active and generate more heat. This tends to enhance the temperature differential between the tumor itself and the surrounding tissue. The present embodiments can therefore be used for diagnosis of cancer, particularly, but not exclusively breast cancer.

The technique of the present embodiments is optionally and preferably applied to surface information that describes the surface of the body. The surface information optionally and preferably comprises thermal information and spatial information.

The thermal information comprises data pertaining to heat evacuated from or absorbed by the surface. Since different parts of the surface generally evacuate or absorb different amount of heat, the thermal information comprises a set of tuples, each comprising the coordinates of a region or a point on the surface and a thermal numerical value (e.g. , temperature, thermal energy) associated with the point or region. The thermal information can be transformed to visible signals, in which case the thermal information is in the form of a thermographic image.

The thermal data is typically arranged gridwise in a plurality of picture-elements (e.g. , pixels, arrangements of pixels) representing the thermographic image. Each picture-element is represented by an intensity value or a grey-level over the grid. It is appreciated that the number of different intensity values can be different from the number of grey-levels. For example, an 8-bit display can generate 256 different grey- levels. However, in principle, the number of different intensity values corresponding to thermal information can be much larger. As a representative example, suppose that the thermal information spans over a range of 37 °C and is digitized with a resolution of 0.1 °C. In this case, there are 370 different intensity values and the use of grey-levels is less accurate by a factor of approximately 1.4. Use of higher formats (e.g. , 10 bit, 12 bit, 14 bit or higher) is also contemplated. For example, a photon thermal camera can provide information pertaining to the number of photons detected by the camera detector. Such information can extend over a range of about 6000-8000 intensity values.

In some embodiments of the present invention the correction technique is applied to intensity values, and in some embodiments of the present invention the correction technique is applied to grey-levels. Combinations of the two (such as double processing) are also contemplated.

The term "pixel" is sometimes abbreviated herein to indicate a picture-element. However, this is not intended to limit the meaning of the term "picture-element" which refers to a unit of the composition of an image.

The terms "thermographic image", "thermal image", "thermal information" and "thermal data" are used interchangeably throughout the specification without limiting the scope of the present embodiments in any way. Specifically, unless otherwise defined, the use of the term "thermographic image" is not to be considered as limited to the transformation of the thermal information into visible signals. For example, a thermographic image can be stored in the memory of a computer readable medium, preferably a non-transitory computer readable medium, as a set of tuples as described above.

In embodiments in which the surface information also comprises spatial information, the spatial information comprises data pertaining to geometric properties of a surface which at least partially encloses a three-dimensional volume. In some embodiments of the present invention the surface is non-planar, e.g. , curved. Generally, the surface is a two-dimensional object embedded in a three-dimensional space. Formally, a surface is a metric space induced by a smooth connected and compact Riemannian 2-manifold. Ideally, the geometric properties of the surface would be provided explicitly for example, the slope and curvature (or even other spatial derivatives or combinations thereof) for every point of the surface. Yet, such information is rarely attainable and the spatial information is provided for a sampled version of the surface, which is a set of points on the Riemannian 2-manifold and which is sufficient for describing the topology of the 2-manifold. Typically, the spatial information of the surface is a reduced version of a 3D spatial representation, which may be either a point-cloud or a 3D reconstruction (e.g. , a polygonal mesh or a curvilinear mesh) based on the point cloud. The 3D spatial representation is expressed via a 3D coordinate-system, such as, but not limited to, Cartesian, Spherical, Ellipsoidal, 3D Parabolic or Paraboloidal coordinate 3D system.

The spatial data, in some embodiments of the present invention, can be in a form of an image. Since the spatial data represent the surface such image is typically a two- dimensional image which, in addition to indicating the lateral extent of body members, further indicates the relative or absolute distance of the body members, or portions thereof, from some reference point, such as the location of the imaging device. Thus, the image typically includes information residing on a surface of a three-dimensional body and not necessarily in the bulk. Yet, it is commonly acceptable to refer to such image as "a three-dimensional image" because the surface is conveniently defined over a three- dimensional system of coordinate. Thus, throughout this specification and in the claims section that follows, the terms "three-dimensional image" and "three-dimensional representation" primarily relate to surface entities.

The lateral dimensions of the spatial data are referred to as the x and y dimensions, and the range data (the depth or distance of the body members from a reference point) is referred to as the z dimension.

When the surface information of a body comprises thermal information and spatial information, the surface information (thermal and spatial) of a body is typically in the form of a synthesized representation which includes both thermal data representing the thermal image and spatial data representing the surface, where the thermal data is associated with the spatial data (i.e. , a tuple of the spatial data is associated with a heat-related value of the thermal data). Such representation is referred to as a thermospatial representation. The thermospatial representation can be in the form of digital data (e.g. , a list of tuples associated with digital data describing thermal quantities) or in the form of an image (e.g. , a three-dimensional image color-coded or grey-level coded according to the thermal data). A thermospatial representation in the form of an image is referred to hereinafter as a thermospatial image.

The thermospatial representation is defined over a 3D spatial representation of the body and has thermal data associated with a surface of the 3D spatial representation, and arranged gridwise over the surface in a plurality of picture-elements (e.g. , pixels, arrangements of pixels) each represented by an intensity value or a grey-level over the grid.

When the thermospatial representation is in the form of digital data, the digital data describing thermal properties can also be expressed either in terms of intensities or in terms of grey-levels as described above. Digital thermospatial representation can also correspond to thermospatial image whereby each tuple corresponds to a picture-element of the image.

Preferably, one or more thermographic images are mapped or projected onto the surface of the 3D spatial representation to form the thermospatial representation. The thermographic image to be projected onto the surface of the 3D spatial representation preferably comprises thermal data which are expressed over the same coordinate- system as the 3D spatial representation. Any type of thermal data can be used. In one embodiment the thermal data comprises absolute temperature values, in another embodiment the thermal data comprises relative temperature values each corresponding, e.g., to a temperature difference between a respective point of the surface and some reference point, in an additional embodiment, the thermal data comprises local temperature differences. Also contemplated, are combinations of the above types of temperature data, for example, the thermal data can comprise both absolute and relative temperature values, and the like.

Typically, but not obligatorily, the information in the thermographic image also includes the thermal conditions (e.g. , temperature) at one or more reference markers. The acquisition of surface data is typically performed by positioning the reference markers, e.g. , by comparing their coordinates in the thermographic image with their coordinates in the 3D spatial representation, to thereby match, at least approximately, also other points hence to form the synthesized thermospatial representation.

A representative example of a synthesized thermospatial image for the case that the body comprise the breasts of a female or male subject is illustrated in FIGs. 1A-C, showing a 3D spatial representation illustrated as a non-planar surface (FIG. 1A), a thermographic image illustrated as planar isothermal contours (FIG. IB), and a synthesized thermospatial image formed by mapping the thermographic image on a surface of the 3D spatial representation (FIG. 1C). As illustrated, the thermal data of the thermospatial image is represented as grey-level values over a grid generally shown at 102. It is to be understood that the representation according to grey-level values is for illustrative purposes and is not to be considered as limiting. As explained above, the processing of thermal data can also be performed using intensity values. Also shown in FIGs. 1A-C, is a reference marker 101 which optionally, but not obligatorily, can be used for the mapping.

In some embodiments of the present invention a series of thermal images of a section of a living body is obtained. Different thermal images of the series include thermal data acquired from the portion of the body at different time instants. Such series of thermal images can be used by the present embodiments to determine thermal changes occurred in the portion of the body over time.

In some embodiments of the present invention a series of thermospatial representation of a section of a living body is obtained. Different thermospatial representations of the series include thermal data acquired from the portion of the body at different time instants. Such series of thermospatial representations can be used by the present embodiments to determine thermal and optionally spatial changes occurred in the portion of the body over time.

The series can include any number of thermal images or thermospatial representations. It was found by the inventors of the present invention that two thermal images or thermospatial representations are sufficient to perform the analysis, but more than two thermal images or thermospatial representations (e.g. , 3, 4, 5 or more) can also be used, for example, to increase accuracy of the results and/or to allow selection of best acquisitions.

The 3D spatial representation, thermographic image and synthesized thermospatial image can be obtained in any technique known in the art, such as the technique disclosed in International Patent Publication No. WO 2006/003658, U.S. Published Application No. 20010046316, and U.S. Patent Nos. 6,442,419, 6,765,607, 6,965,690, 6,701,081, 6,801,257, 6,201,541, 6, 167,151, 6, 167,151, 6,094, 198 and 7,292,719.

Some embodiments of the invention can be embodied on a tangible medium such as a computer for performing the method steps. Some embodiments of the invention can be embodied on a computer readable medium, preferably a non-transitory computer readable medium, comprising computer readable instructions for carrying out the method steps. Some embodiments of the invention can also be embodied in electronic device having digital computer capabilities arranged to run the computer program on the tangible medium or execute the instruction on a computer readable medium. Computer programs implementing method steps of the present embodiments can commonly be distributed to users on a tangible distribution medium. From the distribution medium, the computer programs can be copied to a hard disk or a similar intermediate storage medium. The computer programs can be run by loading the computer instructions either from their distribution medium or their intermediate storage medium into the execution memory of the computer, configuring the computer to act in accordance with the method of this invention. All these operations are well-known to those skilled in the art of computer systems.

FIG. 2 is a flowchart diagram of a method suitable for correcting image data, according to some embodiments of the present invention. The method is applied to at least one 3D thermospatial representation of a portion of a body, preferably a living body. The portion of the body can include one or more organs, e.g., a breast or a pair of breasts, or a part of an organ, e.g., a part of a breast. The 3D thermospatial representation has 3D spatial data representing a non-planar surface of the portion of the living body and thermal data associated with the 3D spatial data.

It is to be understood that, unless otherwise defined, the operations of the method described hereinbelow can be executed either contemporaneously or sequentially in many combinations or orders of execution. Specifically, the ordering of the flowchart diagrams is not to be considered as limiting. For example, two or more operations, appearing in the following description or in the flowchart diagrams in a particular order, can be executed in a different order (e.g., a reverse order) or substantially contemporaneously. Additionally, several operations method steps described below are optional and may not be executed.

The method begins at 10 and continues to 11 at which the 3D thermospatial representation is obtained. The method can obtain the 3D thermospatial representation by receiving it from an external source such as a 3D thermospatial representation generator, or by generating the 3D thermospatial representation, for example, by combining 3D and thermal imaging. The method optionally continues to 12 at which the spatial and/or thermal data is preprocessed. In some embodiments of the present invention the preprocessing operation includes definition of one or more spatial boundaries for the surface, so as to define a region-of-interest for the analysis. For example, when the spatial data of the thermospatial representation comprises data representing a surface of tissue being nearby to the portion of the body, the preprocessing operation can include defining a spatial boundary between the surface of the portion of the body and surface of the nearby tissue. In this embodiment, the surface of the nearby tissue is preferably excluded from the analysis.

In some embodiments of the present invention the preprocessing comprises transformation of coordinates. For example, when the method is executed for correcting image data pertaining to more than one body portions having similar shapes, the method preferably transform the coordinates of one or more portions of the body so as to ensure that all body portions are described by the same coordinate- system. A representative example is a situation in which the surface data describe a left breast and a right breast. In this situation, the system of coordinates of the 3D thermospatial representation of one of the breasts can be flipped so as to describe both thermal images and both 3D thermospatial representations using the same coordinate-system.

In some embodiments of the present invention the preprocessing comprises normalization of the thermal data. The normalization is useful, for example, when it is desired not to work with too high values of intensities. In various exemplary embodiments of the invention the normalization is performed so as to transform the range of thermal values within the thermal data to a predetermined range between a predetermined minimal thermal value and a predetermined maximal thermal value. This can be done using a linear transformation as known in the art. A typical value for the predetermined minimal thermal value is 1, and a typical value for the predetermined maximal thermal value is 10. Other ranges or normalization schemes are not excluded from the scope of the present invention.

In some embodiments of the present invention the preprocessing operation includes slicing of the surface described by the spatial data to a plurality of slices. In these embodiments, the correction procedure described below can be applied separately for each slice. The slicing can be along a normal direction (away from the body), parallel direction or azimuthal direction as desired. The slicing can also be according to anatomical information (for example a different slice for a nipple region). Also contemplated is arbitrary slicing, in which case the surface is sliced to N regions.

In some embodiments of the present invention the preprocessing comprises normalization of the spatial data. The normalization is useful when it is desired to compare between thermal data of different portions of the body, for example, body portions having similar shapes but different sizes. These embodiments are particularly useful when the portion of the body is a breast and it is desired to compare the thermal data of breasts of different sizes (e.g. , a left breast to a right breast of the same subject, or a breast of one subject to a breast of another subject).

The method preferably continues to 13 at which a viewing angle is calculated based on the spatial data for one or more of a plurality of picture-elements over the thermospatial representation. The viewing angle Θ of a given picture-element p is conveniently defined between the normal to the surface of the body at picture-element p and the optical axis of the thermal imaging system that provides the thermal data associated with picture-element p. The viewing angle Θ is calculable because the shape of the surface is known from the spatial data, and because the optical axis is known from the thermal data.

The method optionally and preferably continues to 14 at which a predetermined correction function g(9) is applied to each of at least some of the picture-elements for correcting thermal data associated with the respective picture-element. The concept of the correction function will now be explained in greater detail.

For a light ray having a range of wavelengths [λι, λ ₂ ] and arriving to a pixel sensor s of a thermal imaging system from the surface of the body, the associated thermal data typically relates to the luminosity of the light multiplied by the thermal imaging system' s response the li ht and integrated over the wavelength:

where R( ) is the response of the thermal imaging system to light at wavelength λ, L( ,T) is the luminosity of light of wavelength λ arriving from a surface being at a temperature T. The thermal data associated with the pixel sensor s (for example, the grey level GL) is typically a linear function of P(T): GL(T) = a (T) + b

where a and b are constants that do not depend on the temperature.

When the pixel sensor of the thermal imaging system receives light that propagate along the optical axis of the thermal imaging system, the corresponding gray level is typically as indicated above. For light rays that arrive from directions that deviate from the optical axis the thermal imaging system typically employs a Lambertian correction that is proportional to the fourth power of the cosine of the deviation angle. It was found by the present inventors that some curved objects, particularly living bodies, the Lambertian correction is insufficient since different parts of the surface have different primary light emission directions.

In these situations, the grey levels provided by the thermal imaging system do not adequately describe the temperature map of the surface. In other words, for a picture-element at temperature T, the grey level provided by the thermal imaging system when the picture-element is at a viewing angle θι differs from the grey level that would have been provided by the thermal imaging system had the picture-element been at a viewing angle θ ₂ .

According to some embodiments of the present invention the thermal data provided by the thermal imaging system are corrected such that the corrected thermal data of all picture-elements (for which the correction is employed) are the thermal data that would have been provided by the thermal imaging system had all these picture- element been at the same viewing angle relative to the thermal imaging system. For example, the correction can be employed such that for all the picture-elements the corrected thermal data are the thermal data that would have been provided by the thermal imaging system had all these picture-element been at zero viewing angle.

The above procedure can be written mathematically as follows. Denote the thermal data provided by the thermal imaging system for temperature T and viewing angle Θ by GL(T,9), and the thermal data that would have been provided by the thermal imaging system for the same temperature T and zero viewing angle Θ by GL(T,0). The relation between GL(T,9) and GL(T,0) can be expressed as:

GL(T,9) = f(9)-GL(T,0), and

GL(T,0) = g(9)-GL(T,9) where g(9) = f ^θ), is the predetermined correction function applied to the thermal data

GL(T,9) to provide the corrected thermal data GL(T,0).

When the preprocessing operation 12 is executed, the predetermined correction function g(9) can be applied either before or after the preprocessing.

The predetermined correction function g(9) is preferably nonlinear with respect to the angle. A representative example of such nonlinear dependence is shown in FIG.

3, which is a graph of measured temperatures of several points on a human's skin as a function of angle between the normal to skin and the optical axis of a thermal camera.

The data shown were collected from several human subjects. As shown, the angular dependence of the temperature is the generally the same for all the tested subjects.

Without being bound to any particular theory it is assumed that a universal correction function g(9) can be employed for correcting the thermal data irrespectively of the subject under analysis.

The correction function g(9) can be stored in a non-transitory computer readable medium as a lookup table, or it can be provided as an analytical function. Such analytical function can be obtained by parameterizing the correction function g(9) and calculating the parameters based on experimentally observed angular dependence. A representative example of nonlinear correction function is a quadratic function. In experiments performed by the present inventors it was found that a quadratic function of the form g(9) = K 9 or equivalent thereof can be employed, where 9 is measured in radians and K is a constant ranging from -2 to -0.1 or from -1 to -0.1 or from -0.8 to -0.2 or from -0.5 to -0.4. In some embodiments of the present invention K is about -0.4686.

In some embodiments of the present invention the method proceeds to 15 at which the 3D thermospatial representation is regenerated using said corrected thermal data, and/or 16 at which a temperature map of the portion of the body is generated using the corrected thermal data. The 3D thermospatial representation and/or temperature map can optionally be displayed on a display device.

The method can continue to 17 at which the corrected data are compared 17 to data of a reference thermospatial representation, which can be obtained from a library or can be constructed by the method of the present embodiments. The reference thermospatial representation can describe a reference portion of the body other than the portion of the body being analyzed. For example, the reference portion of the body can be a portion of the body which is similar in shape to the portion of the body being analyzed. When the portion of the body is a breast, the reference portion of the body can be the other breast of the same subject. In this embodiment, the aforementioned transformation of coordinates is preferably employed so as to facilitate conceptual overlap of one portion of the body over the other.

In some embodiments of the present invention the reference thermospatial representation includes history data of the portion of the body. Thus, the reference portion of the body can be the same portion of the body as captured at an earlier time. The inclusion of history data in the thermospatial representation can be achieved by recording the reference thermospatial representation at a date earlier than the date at which the method is executed. This embodiment can also be useful for monitoring changes in the portion of the body over time.

When a series of thermospatial representations is obtained, the reference thermospatial representation can be one of the thermospatial representations of the series. In some embodiments of the present invention the ambient temperature at the surface of the portion of the body is changed between two successive captures of surface information, and the corresponding thermospatial representations are obtained. In these embodiments, the corrected thermal data of two such successive thermospatial representations are compared.

A change in the ambient temperature corresponds to different boundary conditions for different thermospatial representations. Specifically, in these embodiments, two successive thermospatial representations describe the portion of the body while the subject is exposed to two different ambient temperatures. A change in the ambient temperature can be imposed, for example, by establishing contact between a cold object and the portion of the body or directing a flow of cold gas (e.g., air) to the surface of the portion of the body between successive data acquisitions. Also contemplated is a procedure in which the portion of the body is immersed in cold liquid (e.g. , water) between successive data acquisitions. Also contemplated is a procedure in which another portion of the body is exposed to a different (e.g. , lower) temperature so as to ensure transient thermal condition. For example, the subject can immerse his or her limb in a cold liquid (e.g. , water). The method can optionally and preferably continue to 18 at which the presence or absence of a thermally distinguished region in the portion of the living body is determined based on the corrected thermal data. This can be achieved using any technique known in the art, except that the uncorrected thermal data used in known techniques is replaced with data corrected according to some embodiments of the present invention. The method can also determine whether or not the thermally distinguished region is a tumor based on a predetermined criterion or a predetermined set of criteria. The set of criteria can include at least one of the temperatures of the region, the temperature difference between the region and its immediate surrounding, the temperature difference between the region and the average temperature of the body portion or some region-of-interest thereof, the size of the region and the like.

The method ends at 19.

Reference is now made to FIG. 4 which is a schematic illustration of an image correction system 20, according to some embodiments of the present invention. System 20 preferably comprises a digital input 22 for receiving one or more 3D thermospatial representations as further detailed hereinabove. System 20 can further comprise a data processor 24 that calculates, based on the spatial data of the input 3D thermospatial representation, a viewing angle Θ, and that applies a predetermined correction function g(9) for correcting the thermal data as further detailed hereinabove.

System 20 typically comprises a non-transitory computer readable medium 26, that can stores computer readable data types and/or computer readable instructions for carrying out the operations of data processor 24. For example, when the predetermined correction function g(9) is in the form of a lookup table, the lookup table can be stored in medium 26 and when the correction function g(9) is in the form of analytical function, computer instructions for calculating g(9) for a given angle 9 can be stored in medium 26.

Data processor 24 can, in some embodiments of the present invention, determine presence or absence of a thermally distinguished region in portion of living body based on corrected thermal data, as further detailed hereinabove. Optionally and preferably data processor 24 determines whether or not thermally distinguished region is a tumor based on a predetermined criterion or a predetermined set of criteria. In some embodiments of the present invention system 20 comprises an image generator 28 that re-generates the 3D thermospatial representation using the corrected thermal data. Additionally or alternatively, image generator 28 can generate a temperature map of portion of body using the corrected thermal data. The re-generated 3D thermospatial representation and/or temperature map can be stored in memory medium 26. System 20 can further comprise a digital output 30 that outputs the regenerated 3D thermospatial representation and/or temperature map, at any known data format. The re-generated 3D thermospatial representation and/or temperature map can be transmitted to an external system such as a cloud storage facility or a remote computer. The re-generated 3D thermospatial representation and/or temperature map can also be transmitted to a display 32 which displays the 3D thermospatial representation and/or temperature map, for example, as color or gray scale images or as contour plots.

As used herein the term "about" refers to ± 10 %.

The word "exemplary" is used herein to mean "serving as an example, instance or illustration". Any embodiment described as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments and/or to exclude the incorporation of features from other embodiments.

The word "optionally" is used herein to mean "is provided in some embodiments and not provided in other embodiments". Any particular embodiment of the invention may include a plurality of "optional" features unless such features conflict.

The terms "comprises", "comprising", "includes", "including", "having" and their conjugates mean "including but not limited to".

The term "consisting of means "including and limited to".

The term "consisting essentially of" means that the composition, method or structure may include additional ingredients, steps and/or parts, but only if the additional ingredients, steps and/or parts do not materially alter the basic and novel characteristics of the claimed composition, method or structure.

As used herein, the singular form "a", "an" and "the" include plural references unless the context clearly dictates otherwise. For example, the term "a compound" or "at least one compound" may include a plurality of compounds, including mixtures thereof.

Throughout this application, various embodiments of this invention may be presented in a range format. It should be understood that the description in range format is merely for convenience and brevity and should not be construed as an inflexible limitation on the scope of the invention. Accordingly, the description of a range should be considered to have specifically disclosed all the possible subranges as well as individual numerical values within that range. For example, description of a range such as from 1 to 6 should be considered to have specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6 etc., as well as individual numbers within that range, for example, 1, 2, 3, 4, 5, and 6. This applies regardless of the breadth of the range.

Whenever a numerical range is indicated herein, it is meant to include any cited numeral (fractional or integral) within the indicated range. The phrases "ranging/ranges between" a first indicate number and a second indicate number and "ranging/ranges from" a first indicate number "to" a second indicate number are used herein interchangeably and are meant to include the first and second indicated numbers and all the fractional and integral numerals therebetween.

It is appreciated that certain features of the invention, which are, for clarity, described in the context of separate embodiments, may also be provided in combination in a single embodiment. Conversely, various features of the invention, which are, for brevity, described in the context of a single embodiment, may also be provided separately or in any suitable subcombination or as suitable in any other described embodiment of the invention. Certain features described in the context of various embodiments are not to be considered essential features of those embodiments, unless the embodiment is inoperative without those elements.

Various embodiments and aspects of the present invention as delineated hereinabove and as claimed in the claims section below find experimental support in the following examples.

EXAMPLES

Reference is now made to the following examples, which together with the above descriptions illustrate some embodiments of the invention in a non limiting fashion.

Experiment was conducted according to some embodiments of the present invention for correcting thermal data. Three women participated in the experiment. The breasts of each woman were imaged using two thermal cameras, wherein two different viewing angles were used for each camera. 3D spatial data for the breasts were also obtained from a 3D imager, and 3D thermospatial representations were obtained from the thermal and spatial data. The images of each camera were registered by translation and rotation relative to anchor points marked on each image.

The thermal data of each image was corrected in accordance with some embodiments of the present invention and the mean and standard deviation of the difference between the grey levels in each pair of images from the same camera were calculated both before and after the correction. The results of the calculations are summarized in Table 1, below, and graphically illustrated in FIG. 5.

Table 1

As shown in Table 1 and FIG. 5, the mean and standard deviation is consistently reduced by the correction procedure, indicating an improvement of the thermal uniformity between picture-elements that describe the same region from two different viewing angles. This observation was supported by a paired t-test which showed a confidence level of 95% that the mean of the differences is higher before the correction than after the correction. Some cases exhibited relatively high standard deviation values, presumable due to artifacts in the thermal data, such as the artifact that is marked with an oval in FIG. 6.

Visible light and thermal images of one woman subject are shown in FIGs. 7A- H. FIGs. 7A and 7B are visible light images from the two different viewing angles, FIG. 7C shows the registration of the two images, FIG. 7D shows picture-elements for which the registration difference is less than 2 mm, FIGs. 7E and 7F shows grey level differences between the thermal images before (FIG. 7E) and after (FIG. 7F) the correction of thermal data, FIG. 7G shows the difference between the absolute values of the images in FIGs. 7E and 7F, and FIG. 7H marks regions at which the thermal correction provides improvement.

Although the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, it is intended to embrace all such alternatives, modifications and variations that fall within the spirit and broad scope of the appended claims.

All publications, patents and patent applications mentioned in this specification are herein incorporated in their entirety by reference into the specification, to the same extent as if each individual publication, patent or patent application was specifically and individually indicated to be incorporated herein by reference. In addition, citation or identification of any reference in this application shall not be construed as an admission that such reference is available as prior art to the present invention. To the extent that section headings are used, they should not be construed as necessarily limiting.