Abstract:
A method and system for acquiring an image of an object using optical coherence tomography using an interferometer and a detector, wherein the object is irradiated with light emitted by the interferometer, light reflected by the object is fed back into the interferometer and detected by the detector, the image of the object is derived from the detected light, and a file containing information, in particular graphical information and/or photographic image information, relating to the object is assigned to and/or correlated with the image of the object.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a 371 National Stage Application of PCT/EP2013/002901, filed Sep. 26, 2013. This application claims the benefit of European Application No. 12006715.2, filed Sep. 26, 2012, which is incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a method and system for optical coherence tomography. 
     2. Description of the Related Art 
     Optical coherence tomography (OCT) is a non-invasive method of investigating the inside of light-scattering specimens. Due to its light-scattering properties biological tissue is particularly suitable for diagnostic examination by OCT. Since for OCT relatively low light intensities are sufficient and the wavelengths of the light used mostly come within the near infrared range (750 nm to 1350 nm), unlike ionizing X-ray diagnostics it does not contaminate biological tissue with radiation. It is therefore particularly significant for medicine. The currently most important areas of application of OCT are in ophthalmology, dermatology and the diagnosis of cancer. However, there are also some non-medical applications, such as, e.g., in materials testing. 
     OCT is roughly comparable to ultrasound diagnostics, wherein, instead of sound, broadband light of a very short coherence length is used. The running times of the light reflected on different boundary layers within the specimen are recorded by an interferometer. With OCT typical resolutions higher by one or two orders of magnitude can be achieved than with ultrasound, but the measuring depth achievable is considerably smaller. Due to optical scattering the cross-section images obtained only reach into the tissue up to a depth of a few millimeters. 
     SUMMARY OF THE INVENTION 
     Preferred embodiments of the present invention provide a method and system for optical coherence tomography which is improved compared to methods and systems known from the state of the art. 
     The advantages and benefits of the present invention are achieved by the method and system described below. 
     With the method for optical coherence tomography (OCT) according to a preferred embodiment of the invention an OCT image of an object, in particular a biological tissue like the skin of a human or animal being, is acquired by an OCT system comprising an interferometer and a detector, wherein the object is irradiated with light emitted by the interferometer, light reflected by the object is fed back into the interferometer and detected by the detector and an OCT image of the object is derived from the detected light. Preferably, a data file containing information relating to the object is assigned to and/or correlated with the OCT image of the object. 
     The system for optical coherence tomography (OCT) for acquiring an OCT image of an object, in particular a biological tissue like the skin of a human or animal being, comprises an interferometer for outputting light with which the object can be irradiated, a detector for detecting light which is reflected by the object and fed back into the interferometer and a control unit for deriving an OCT image of the object from the detected light of the object and, preferably, for assigning and/or correlating a data file containing information relating to the object to or with, respectively, the OCT image of the object. 
     The invention is based on the approach, to assign additional information to the obtained OCT image or vice versa, wherein the assigned additional information characterizes the object or a part of the object, from which the OCT image was or is obtained. For example, the information assigned or to be assigned to an OCT image may contain graphical and/or photographic and/or text information relating to a region of or location on or within the object from which the OCT image was or is obtained, e.g., a body part or a specific location on a body part. Such an assignment or a correlation between the data file containing the additional information, on the one hand, and the OCT image, on the other hand, can be achieved, for example, by at least one of the following methods: 
     providing a memory address of the stored OCT image in the data file of the corresponding additional information and/or 
     providing a memory address of the data file of the additional information in the data file of the corresponding OCT image and/or 
     incorporating data of the data file of the additional information directly into the data file of the corresponding OCT image and/or 
     incorporating data of the OCT image directly into the data file of the corresponding additional information. 
     As a result, by the system and method according to the preferred embodiments of the invention, additional information can be reliably and easily assigned to a corresponding OCT image. 
     Within the meaning of the present invention, the term “assigning” not only relates to assigning additional information to the obtained OCT but also to assigning an obtained OCT image to the additional information. Accordingly, the term “correlating” not only relates to correlating additional information with the obtained OCT image but also to correlating an obtained OCT image with the additional information. 
     Preferably, the data file contains text information and/or graphical information and/or image information, in particular a document or report, relating to the object. Preferred data formats of text information, like a report, are PDF, DOC or TXT. 
     It is particularly preferred that the file contains at least one photographic image of the object, in particular of the surface of the object or a part thereof, and/or a graphical representation of the object or a part of the object. Both photographic images and graphical representations of the object provide expressive additional information in view of diagnostic purposes. Alternatively or additionally, the file contains a video image of the object, in particular of the surface of the object or a part thereof. A video image of the object preferably comprises a sequence of photographic images of the object. Therefore, all elucidations given herein in context with images, in particular photographic images, apply to video images accordingly. Preferred video image formats are, e.g., avi or mpeg. 
     Preferably, the photographic image and/or graphical representation of the object or a part thereof may be a survey image which comprises photographic and/or graphical image information of a region of the object, wherein the region of the object is larger than a region of interest (ROI) of the object from which the OCT image is acquired. It is further preferred that the photographic image of the object and/or graphical representation of the object is an image of a patient&#39;s body area where a region of interest (ROI), from which the OCT image is acquired, is located. These preferred embodiments allow for a particularly reliable assignment of an OCT image to the corresponding location on the object as well as a comfortable retrieval of the OCT image by the survey image or photographic image, respectively. 
     Alternatively or additionally, the photographic image of the object may be a microscopic image which comprises photographic image information of a region of interest (ROI) of the object from which the OCT image is acquired. This allows for a particularly precise assignment of an OCT image to a specific location on the object. 
     It may also be of particular advantage if the photographic image of the object is a photographic color image of the object. Alternatively or additionally, the graphical representation of the object may also a color representation of the object. By this, the reliability of assigning positional information to the OCT image is further enhanced and, due to color images or color representation, the additional information is enriched by possibly further diagnostically relevant information, e.g. color or appearance of skin parts from which the OCT image is obtained. 
     According to another preferred embodiment, the photographic image and/or graphical representation of the object is provided with at least one mark or symbol corresponding to or denoting a position on the object at which an OCT image was or is acquired. Preferably, the photographic image and/or graphical representation of the object together with the at least one mark or symbol is displayed on a display and, upon selection of the at least one displayed mark or symbol by a user, an OCT image acquired at the corresponding position on the object is displayed on the display. These preferred embodiments further contribute to increase the reliability of the assignment of an OCT image to the corresponding location on the object as well as the comfortable retrieval of the OCT image by the photographic image and/or graphical representation of the object. 
     According to an additional or alternative aspect of the invention, the OCT system examines, in particular continuously, whether a photographic image of the object, in particular of the surface of the object, is available to the OCT system. 
     The system is preferable configured such that in the case that an OCT image acquisition session of the OCT system is running and a photographic image is available to the OCT system, the control unit of the OCT system indicates to a user that a photographic image is available. 
     Preferably, it is indicated to a user that a photographic image is available by displaying a pop-up window on the display of the OCT system. 
     Further, the system is preferable configured such that in the case that an OCT image acquisition session of the OCT system is running and a photographic image is available to the OCT system, the user is requested as to whether the available photographic image shall be stored in the file and/or shall be assigned to or correlated with the OCT images acquired at the current OCT image acquisition session. 
     Moreover, the system is preferably configured such that in the case that a photographic image of the object is available, in particular available to the OCT system, the photographic image and the OCT image are stored in a memory such that the stored OCT image contains information relating to the photographic image or a storage address of the stored photographic image and/or the stored photographic image contains information relating to the OCT image or a storage address of the stored OCT image. 
     The above-mentioned additional or alternative aspects of the invention are based on the approach that photographic images of an object, which were acquired by a photographic camera, like a digital camera, a microscopic camera, a USB microscope, a smart phone comprising a camera or a tablet PC comprising a camera, can be provided, e.g. sent, transferred or communicated, to the OCT system by which OCT images of the object, in particular of certain regions of interests (ROI) of the object, are acquired in an OCT image acquisition session. As a camera a dermatoscopic camera or any other digital imaging device used in dermatology can also be used. 
     Therefore, preferred embodiments of the invention also relate to a photographic camera for acquiring photographic images of an object, in particular a biological tissue like the skin of a human or animal being, which is designed such that an acquired photographic image can be provided, in particular sent or communicated, to the system for optical coherence tomography (OCT). 
     The term “camera” or “photographic camera” in the context of the invention is not limited to photographic cameras in the narrower sense, i.e. cameras for acquiring, in particular digital, photographs or photographic images, but also comprises other image acquisition systems allowing for an acquisition of electromagnetic radiation images, in particular in the visible spectral range, e.g. microscopes, epi-illumination imaging systems, trans-illumination imaging systems and fluorescence imaging systems. 
     In the context of the invention, a photographic image is preferably acquired from the skin of a patient. Alternatively or additionally, a photographic image can also be acquired from the whole patient or from a patient&#39;s body area where a region of interest, e.g. a skin lesion or similar, is located. 
     Moreover, the above-mentioned preferred embodiments are not restricted to photographic images as such. Alternatively or additionally, documents and/or reports and/or any kind of files containing text and/or graphical and/or information relating to an object can be provided, e.g. sent, transferred or communicated, to an OCT system by which OCT images of the object, in particular of certain regions of interests (ROI) of the object, are acquired in an OCT image acquisition session. 
     Accordingly, all elucidations given with respect to photographic images also apply mutatis mutandis to documents and/or reports and/or any kind of files containing text and/or graphical and/or image information relating to the object. 
     Preferably, the camera is provided with a camera control unit by which acquired photographic images can be selected by a user and subsequently sent to the OCT system via a data communication between the camera and the OCT system. The camera control unit is designed such that it can execute a corresponding application computer program, a so-called “App”. The data communication between the camera and the OCT system can be based on a wire-bound connection, like via local area network (LAN), universal serial bus (USB) or the internet, or a wireless connection, like Bluetooth. 
     The OCT system is preferably provided with a control unit which is designed for examining whether a photographic image is available, e.g. by checking whether a photographic image has been provided or sent by the camera to the OCT system and/or by checking whether a photographic image is present, i.e. stored, in a pre-defined memory, wherein the pre-defined memory is preferably part of the OCT system, in particular part of the control unit. 
     In the case that the examination yields that a photographic image is available while an OCT image acquisition session is running, i.e. while an OCT image of the object has recently been acquired or is to be acquired soon, the photographic image is displayed on a display unit, preferably a display unit of the OCT system. Alternatively, only an indicator showing the availability of a photographic image is displayed. 
     Moreover, the control unit can be designed so that it gives a request to a user for an input whether the available photographic image shall be imported and/or stored and/or assigned to and/or correlated with the OCT image which has been or will be recorded in the current OCT imaging acquisition session. Preferably, depending on the user-input the available photographic image will be assigned to and/or correlated with the OCT image which has been or will be recorded in the current OCT imaging acquisition session so that a unique and/or bijective and/or unambiguous allocation of the photographic image and the OCT image is achieved. 
     The above-mentioned additional or alternative aspects of the invention allow for a convenient and safe acquisition, transfer and addition of supplemental diagnostic information in the form of photographic images and/or graphical representations of an object to OCT images of the object. 
     In a method for optical coherence tomography according to a more generalized approach an OCT image of an object, in particular a biological tissue like the skin of a human or animal being, is acquired by an OCT system comprising an interferometer and a detector, wherein 
     the object is irradiated with light emitted by the interferometer, 
     light reflected by the object is fed back into the interferometer and detected by the detector and 
     an OCT image of the object is derived from the detected light. 
     A system for optical coherence tomography for acquiring an OCT image of an object, in particular a biological tissue like the skin of a human or animal being, according to a more generalized approach comprises 
     an interferometer for outputting light with which the object can be irradiated, 
     a detector for detecting light which is reflected by the object and fed back into the interferometer and 
     a control unit for deriving an OCT image of the object from the detected light. 
     Preferably, the OCT image is encoded in a first image data format and the photographic image and/or the graphical representation of the object is encoded in a second image data format, wherein the second image data format is different to the first image data format. 
     Preferably, at least one photographic image and/or the graphical representation of the object, which is encoded in the second image data format, is converted and/or incorporated into the first image data format of the OCT image. 
     Preferably, the first image data format corresponds to the DICOM format. A single DICOM file contains both a header which stores information about, e.g., the patient&#39;s name, the type of scan, image dimensions, etc., as well as all of the OCT image data which can contain information in three dimensions. The use of the DICOM format as the first image data format has the additional advantage that standardized reader software for DICOM files exists so that a possibly available proprietary reader software of the OCT system is not mandatory in the case that the OCT image file together with the converted or incorporated file with additional information has to be read by another instance, e.g. by an external physician, where the OCT system is not available. 
     The term “DICOM format” in the sense of the present invention also comprises the so-called DICOMDIR format, with comprises one or more DICOM format files in a directory or folder, in particular a directory structure or folder structure. 
     Preferably, the second image data format corresponds to one of the following formats: JPEG, TIFF, PNG, BMP, GIF or PDF. 
     Preferably, the first image data format, in particular the DICOM format, of the OCT image comprises a header section and an image data section, wherein 
     the header section contains general information related the OCT image, e.g. object ID, type of examination or OCT image dimensions, and the image data section contains image data of the OCT image, 
     image data of the at least one photographic image and/or the graphical representation of the object are incorporated into the header section of the first image data format of the OCT image. 
     Preferably, the OCT image in the first image data format is stored in a memory, wherein the header of the OCT image in the first image data format contains the image data of the photographic image and/or the graphical representation of the object. 
     The preferred embodiments elucidated above are based on the approach to assign additional information relating to the object, like a photographic image and/or a graphical representation of the object and/or additional text information, to an OCT image by incorporating data of the data file of the additional information into the data file of the corresponding OCT image. For example, data of a photographic or graphical image data file of a first data format, like JPEG or GIF, are incorporated into the OCT image data file of a second data format, in particular DICOM. In this way, a particularly reliable assignment or correlation of additional information relating to the object, on the one hand, to/with an OCT image, on the other hand, is achieved in a very simple way. As a result, when retrieving an accordingly stored OCT image data file, corresponding additional information, in particular photographic and/or graphical image data, are retrieved at the same time and vice versa. 
     Preferably, the photographic image of the object is provided to the OCT system by data communication connection between the camera and the OCT system. Preferably, the data communication connection is a wireless data connection. Alternatively, any other kind of communication path is also allowed, e.g. a wire-bound data connection. 
     Preferably, the camera comprises a camera control unit by which image data of the photographic image are provided, in particular sent or transferred, to the OCT system. Preferably, the image data of the photographic image are provided to the OCT system upon selection of a photographic image from a list of photographic images displayed at the camera. Preferably, the selection of a photographic image from a list of photographic images displayed at the camera is done by a user. Preferably, the image data of the photographic image are provided to the OCT system upon a corresponding command given by a user. Preferably, a command for providing the image data of the photographic image to the OCT system is given by activation of a corresponding button at the camera or icon displayed on the display of the camera. Alternatively or additionally, a user command can also be given by, e.g., language statements of the user, i.e. commands or instructions by the user&#39;s voice, or gestures of the user performed in space and/or on the display. Accordingly, a respective command receiving unit, e.g. a speech recognition unit and/or a gesture recognition unit and/or a touch screen, is provided. Preferably, the assigned photographic image and OCT image of the object are displayed simultaneously on a common display. 
     Further advantages, features and examples of the present invention will be apparent from the following description of following figures: 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows an example of a part of an OCT system; 
         FIG. 2  shows an example of an OCT system; 
         FIG. 3  shows examples of a graphic representation of a whole patient (upper part of figure) and of a patient&#39;s part (lower part of figure); 
         FIG. 4  shows an example of a graphic representation of a patient&#39;s part together with examples of imported photographic images obtained from areas of the patient&#39;s part; 
         FIG. 5 . shows an example of a preferred workflow for assigning graphical information and/or photographic images to OCT images; 
         FIG. 6  shows another example of a preferred workflow for assigning graphical information and/or photographic images to OCT images; 
         FIG. 7  shows graphical representations and a photographic image for the illustration of workflows for retrieving OCT images; 
         FIG. 8  shows graphical representations for the illustration of a further workflow for retrieving OCT images; 
         FIG. 9  shows another graphical representation for the illustration of a further workflow for retrieving OCT images; 
         FIG. 10  shows graphical representations for the illustration of yet another workflow for retrieving OCT images; 
         FIG. 11  shows an example of displaying OCT images together with graphical representations of corresponding body parts; 
         FIG. 12  shows a first schematic representation of the contents of an OCT image data file in DICOM format; and 
         FIG. 13  shows a second schematic representation of the contents of an OCT image data file in DICOM format. 
     
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       FIG. 1  shows a schematic representation of an example of a part of an OCT system comprising an interferometer  10  with a beam splitter  11 , an illumination arm  12 , a reference arm  13 , a sample arm  14  and a detector arm  15 . Moreover, an illumination light source  21  is provided for generating light which is filtered by an optical filter  22  and focused into the entrance region  25  of a light guide  26  by optics which comprises lenses  23  and  24 . 
     The light coupled into the light guide  26  is coupled into the illumination arm  12  of the interferometer  10  by optics  28  located at the exit region  27  of the light guide  26 . The light reaches the beam splitter  11  by which the light is forwarded to the reference arm  13  and reflected on a reference mirror  16  located at the end of the reference arm  13 . On the other hand, a part of the light passes the sample arm  14  and illuminates an area  2  of an object  1 . The object is preferably a biological tissue, in particular the skin of a human being. 
     The light reflected, in particular back-scattered, by the object  1  passes again the sample arm  14  and is superimposed in the beam splitter  11  with light reflected by the reference mirror  16  of the reference arm  13 . The superimposed light finally reaches by passing the detector arm  15  the detector  30  which comprises a plurality of detector elements which are arranged along a, preferably plane, area and therefore enables a spatially resolved acquisition of the light reflected or scattered by the object  1 , in particular the detection of a corresponding interference pattern. 
     Preferably, the detector  30  comprises a CMOS camera, the detector elements of which are sensitive in the infrared spectral range, in particular in a spectral range between approximately 1250 nm and 1350 nm. Preferably, the CMOS camera has 512×640 detector elements. 
       FIG. 2  shows an example of an OCT system  50  comprising a housing  51 , input elements in form of a keyboard  53 , a computer mouse  54  as well as a pedal control unit  55 . The OCT system  50  is also called “SKINTELL” which is a registered trade mark of Agfa HealthCare N.V., Belgium. 
     The system  50  further comprises a sensor head  57  which is connected with the housing  51  via a cable  58  or a cable conduit. In its rest position, the sensor head  57  is plugged into a holder provided at the housing  51  and can be removed from the holder—as indicated by dotted lines of the sensor head  57  and the cable  58 —when OCT images shall be acquired. 
     The system further comprises a display  52  in form of a flat screen on which OCT images  60  and  61 , which were acquired from the object  1 , in particular a patient, by setting the sensor head  57  onto the object  1 , in particular onto a patient&#39;s skin. 
     On the display  52  of the OCT system  50  a photographic image  62  of the object  1  is displayed in addition to the OCT images  60  and  61 . The photographic image  62  has been acquired by a photographic digital camera  70  which can be, for example, a usual digital camera, a smart phone, a tablet PC or a digital microscope. The camera  70  comprises a camera display  71  which displays one or more photographic images  62 ′ acquired by a photographic image acquisition unit (not shown) of the camera  70 , preferably comprising one or more optical lenses and a CCD array for converting light received from the object  1  into spatially resolved photographic image data of the object  1 . Upon activation of a respective selection button  72  by a user, the photographic image data of the captured photographic image  62 ′ are sent by a wireless communication connection  73  to the OCT system  50  and received by the latter. 
     A control unit (not shown) of the OCT system  50  continuously examines whether photographic image data are available or have been sent to the OCT system  50  and, in the affirmative case, gives the user a notice that a photographic image is available, for example by a pop-up window at the display  52  of the OCT system  50  showing the transmitted photographic image and requesting the user for an input whether the available photographic image shall be imported and/or assigned and/or correlated with the one or more OCT images  60  and  61  which have been or will be acquired from the same object  1 . In the case that the user decides to accept the available photographic image  62 , the latter will be stored in a memory of the OCT system  50  and/or displayed on the display  52  of the OCT system  50 . 
     The method and system  50  described above allows for a very convenient and safe acquisition, transfer and addition of photographic image information of an object to OCT images acquired from the same object. This considerably helps the user, in particular a medical practitioner, to identify the location on the object  1  on which or from which OCT images  60  and  61  were acquired. 
     In particular, the system  50  and/or the camera  70  is/are designed for executing a method, in particular in form of a software package, for wireless transfer of, in particular jpeg, images from a smart phone operating system, in particular iOS, to a windows PC (XP SP3; 7). The image transfer is easy and fast for the user. Preferably, a graphical user interface (GUI) on the iOS guides the user intuitively (no reading of user manual up-front necessary). 
     Preferably, the OCT system  50  and/or a component thereof is designed for importing JPG images stored on a storage medium that is available in the OS of a camera  70  into the OCT system  50 . It is possible to import a JPG image to the OCT system via bluetooth or WiFi from a registered device, like a smart phone. Preferably, the method or system comprise the following steps and/or features, wherein unless otherwise stated, the term “image” or “images” refers to photographic image(s): 
     A button “Import image from file” located at the lower edge of the screen  52  (in row with export buttons) shall trigger the import from file. 
     Bluetooth or WiFi import: a window will pop up automatically as soon as a file was sent to the PC of the OCT system  50  via bluetooth or WiFi hardware. 
     The application running at the control unit of the OCT system  50  supervises a folder (configurable in the *.ini); if a jpg or jpeg image is added to this folder, a window pops up automatically. Preferably, any other file-extension shall be ignored. 
     Import of images (bluetooth, WiFi and from file) is possible if a session is open or in a scanning mode, i.e. a mode in which an OCT image has been or is to be acquired. 
     It is possible to add images to an old, i.e. previous, session which was opened via an “admin screen”. 
     Clicking on “Import image from file” opens a context menu that allows to chose an image file from all available storage media (hard disk; USB stick; camera . . . ) pre-select only “*.JPG and *.JPEG”. 
     The image will be displayed in the main view window and in a thumbnail list after import. 
     Default size of the image frame is maximum 1200 pixels wide and/or maximum 1000 pixels high, dependent on image ratio which limit should be applied. 
     Default display of image fits the image into an image frame but shall not distort the image (after choosing image from thumbnail list); (e.g. an image with 2000×500 pixels is displayed as 1200×300; or an image with 1200×1800 pixels is displayed as 667×1000). 
     Preferably, the system is configured such that an image distortion shall not be possible. 
     The image size is scaled at import to 4000 pixels if image width or height is larger than 4000. 
     It is possible to add an image comment to imported images. 
     Imported images appear in HTLM reports in the same manner as SKINTELL images, i.e. OCT images. 
     Export as TIFF is not mandatory for imported images but is allowed. 
     Imported images are stored in the data base in the same way as SKINTELL images, i.e. OCT images. 
     A session contains both SKINTELL images, i.e. OCT images, and imported images, i.e. photographic images. 
     Re-calling a session can show all SKINTELL images, i.e. OCT images, and imported images. 
     A DICOM export includes imported images. 
     A folder clean-up is performed at start-up of SKINTELL only, wherein files older than two days are deleted. 
     If an image is added via BlueTooth or WiFi and the OCT system  50  is in compare screen mode, the jpg or jpeg are always added to the left session. 
     If the OCT system  50  is in compare screen mode and the same session is open on both sides, the jpg/jpeg images are added to this session and are displayed in both thumbnail lists. 
     In the following, the assigning of additional information in form of photographic images and/or a graphic representation of an object, in particular a patient, to OCT images obtained from the object will be elucidated in more detail. 
       FIG. 3  shows an example of a graphic representation of a whole patient (upper part) and of a patient&#39;s region (lower part) in form of line drawings. Such a mere graphical representation is preferred in the case that no photographic images are available or were imported. The graphical representations are displayed preferably on the display  52  of the OCT system  50  (see  FIG. 2 ) when the latter is in a diagnostic mode in which OCT images  60 ,  61  are acquired. Preferably, the graphical representations of the patient are displayed on the display  52  instead of or in addition to a photographic image  62  of the patient or a part of the patient. 
     By the displayed graphic representation of the patient or a patient&#39;s part, a user can pre-define regions of interest and/or suspicious regions on the body of a patient under examination by selecting a body region, like the arm (upper part of  FIG. 3 ), and/or by selecting an exact location or position on a displayed part of the object, for example on the arm (lower part of  FIG. 3 ), e.g. by a mouse pointer  5 . Preferably, the selected location on the graphical representation of the body part, e.g. the arm, is labeled with a mark  6 , like a circle, which is visible to the user. 
     Upper part of  FIG. 4  shows an example of a graphic representation of a patient&#39;s arm which is displayed, preferably on display  52  of OCT system  50  (see  FIG. 2 ), together with a list  63  of imported photographic images obtained from different areas of the patient&#39;s arm. 
     After an initial selection of a body region, i.e. the arm, by the user (see upper part of  FIG. 3 ), the system is configured such that the user can define exact locations on the displayed body region, e.g. on the upper arm or near the wrist, preferably by dragging (see arrows A and B) a photographic image from the displayed list  63  of photographic images to the corresponding position on the displayed representation of the arm. In the graphical representation of the arm, respective positions are automatically labeled with marks  6  and  7 , respectively. By this, photographic images  63  of areas of a patient or a patient&#39;s part can be exactly and intuitively assigned to corresponding locations on the displayed body region. 
     Preferably, the photographic images  63  may also contain marks  8 ,  9  indicating one or more positions or regions of interest, in particular positions or regions of the body from which OCT images were or have to be obtained. Preferably, the size of the marks  6  to  9  displayed in the graphic representation and/or the photographic images  63  can be changed by zooming a mark, e.g. mark  8 , from its center, e.g. by a mouse pointer  5  as illustrated by dashed arrow in the lower part of  FIG. 4 . 
       FIG. 5  shows an example of a preferred workflow for assigning graphical information and/or photographic images to OCT images. 
     In a first step, as illustrated in  FIG. 5 a   ), at least one photographic image  62  of an area on the patient&#39;s skin is imported into the OCT system  50  and provided with marks  9   a  to  9   c  indicating regions of diagnostic interest on the area and, preferably, assigned to the corresponding location, see mark  7 , on a graphical representation (left part of  FIG. 5 a   ) of the respective body region as elucidated in detail above, preferably by dragging and dropping the image  62  to the according location on the graphical representation of the patient. In the case that no photographic image has been imported, only the graphical representation is provided with an according mark  7 . 
     In a second step, as illustrated in  FIG. 5 b   ), the sensor head  57  (see  FIG. 2 ), in particular a light outlet and inlet window of the sensor head  57 , is placed onto an area of the skin of the patient  1  corresponding to the area from which the displayed photographic image  62  was obtained and/or corresponding to the location of mark  7  on the graphical representation of the patient. In particular, the sensor head  57  is placed onto a region of interest on the patient&#39;s skin corresponding to the location which is indicated by one of the marks  9   a  to  9   c  on the photographic image  62 . 
     Preferably, the system is designed such that a user can toggle between marks  7  and/or  9   a  to  9   c . This can be achieved, e.g., by pressing a button, like a button at the sensor head  57 , keyboard  53 , mouse  54  and/or pedal control unit  55 , or by any other control element. In general, the system may be configured such that toggling is not only possible between marks  7  and  9   a  to  9   c  of the same body part but also between marks on different body parts. By this, one of the marks  7  and  9   a  to  9   c  can be easily selected by the user before the sensor head  57  is placed onto the location on the patient&#39;s skin corresponding to the position of the selected mark  7  and  9   a  to  9   c.    
     In a third step, as illustrated in  FIG. 5 c   ), acquisition of an OCT image  61  from the region of interest, onto which the sensor head  57  is placed, is initiated, preferably by pressing the same or another button, in particular a button at the sensor head  57 , keyboard  53 , mouse  54  and/or pedal control unit  55 , or by any other control element. Subsequently, the acquired OCT image  61  is stored and assigned to the graphical representation of the patient and/or to the photographic image  62  of the corresponding area, preferably together with respective marks  7  or  9   a  to  9   c.    
     The workflow elucidated above is of particular advantage if body locations of interest have already been defined before corresponding OCT images are acquired. 
       FIG. 6  shows another example of a preferred workflow for assigning graphical information and/or photographic images to OCT images. This workflow allows for an assignment of OCT images to corresponding body locations after the OCT images have been obtained. 
     In a first step, an imported photographic image  62  of an area of the patient&#39;s skin is assigned to the corresponding location on a graphical representation of the patient by dragging (see arrow A) and dropping the photographic image  62 , e.g. by a mouse pointer  5 , to the corresponding location on the graphical representation, whereupon the location is labeled with a corresponding mark  7 . 
     In a second step, a previously acquired OCT image  60  is dragged (see arrow B) and dropped, preferably by a mouse pointer, to a location  9   a  on the displayed photographic image  62 , which corresponds to the location of the region of interest on the patient&#39;s skin from which the selected OCT image  60  was obtained. Same applies accordingly to a further OCT image  61 , which is dragged (see arrow C) and dropped to location  9   b  on the displayed photographic image  62 . 
     Preferably, the system is configured such that in the case that no photographic image  62  is available, an OCT image  60 ,  61  can be dragged (see dashed arrows B′ and C′) and dropped to a location (see mark  7 ) on the displayed graphical representation of the patient&#39;s part, wherein the location corresponds to the region of interest from which the selected OCT image  60 ,  61  was obtained. 
     The workflows elucidated above allow for a particularly reliable retrieval of OCT images, in particular when a follow-up diagnosis is carried out. This will be elucidated in detail in the following. 
       FIG. 7  shows graphical representations and a photographic image of the patient or a patient&#39;s part, respectively, by which workflows for retrieving OCT images are illustrated. 
     As shown in the upper part of  FIG. 7 , from a graphical representation of the whole body of the patient a part, e.g. the head, can be selected, preferably by a mouse pointer  5 . In the case that OCT images were previously assigned to a graphical representation of this part, an enlarged representation of the selected part appears, in which the exact locations of the corresponding regions of interest on the patient&#39;s skin, from which OCT images were obtained, are labeled with corresponding marks. By selecting the marks, e.g. by a mouse pointer  5 , the corresponding OCT image can be retrieved and displayed. 
     Alternatively or additionally, as illustrated in the lower part of  FIG. 7 , from a graphical representation of a part of the body of the patient a region, e.g. near the wrist, can be selected, preferably by a mouse pointer  5 . In the case that at least one photographic image  62  was previously assigned to this region, the at least one photographic image  62  appears upon selection of this region in the graphical representation. Further, in the case that OCT images were assigned to the photographic image  62  of this region, the exact locations of the regions of interest on the patient&#39;s skin, from which the OCT images were obtained, are labeled with corresponding marks in the displayed photographic image  62 . By selecting these marks, e.g. by a mouse pointer  5 , the corresponding OCT images can be retrieved and displayed. 
       FIGS. 8 and 9  show graphical representations for the illustration of further examples of workflows for retrieving OCT images, which are of particular advantage in the case that a large number of consultations were made and/or a large number of regions of interest of the patient were investigated. A large number in this context is a number which preferably exceeds 12 or 16. 
     In order to avoid a confusion of the user due to large numbers of corresponding marks on the respective representation of the body or body part, the system is configured such that in an initial step a body region in the graphical representation of the body is highlighted when a pointing element, e.g. a mouse pointer  5 , is over the body region, as shown in the posterior view of the graphical representation of the patient in  FIG. 8 , where the mouse pointer  5  is located over the head. Preferably, this body region is highlighted in the presence of the pointing element  5  only in the case that additional text information and/or OCT images were assigned to this body region. Additionally or alternatively to a highlighting of the body region, an information on possibly available prior consultations and/or OCT image recordings is displayed, e.g. date and clinical findings and/or symptoms, as exemplarily shown in  FIG. 8 . 
     After the body part has been selected, an enlarged representation of this body part is displayed (see  FIG. 9 ) which is labeled with marks at the exact locations of regions of interest from which OCT images were acquired. Additionally, the system is configured such that when the mouse pointer is over a mark, an information on possibly available prior consultations and/or OCT image acquisitions is displayed, e.g. date and clinical findings and/or symptoms. 
       FIG. 10  shows graphical representations of the patient&#39;s body for the illustration of a further example of a workflow for retrieving OCT images, which is of particular advantage in the case that only a small number of consultations were made and/or a small number of regions of interest of the patient were investigated. A small number in this context is a number which is preferably smaller than 12 or 16. 
     In this case, an initial pre-selection of a relevant part of the body, as elucidated above in connection with  FIG. 8 , may be omitted. Rather, according marks are displayed directly on the graphical representations of the whole body, as illustrated in  FIG. 9 . As for the rest, the elucidations in connection with  FIG. 9  apply accordingly. 
     The examples of workflows and functionalities elucidated above allow for a comfortable and reliable retrieval of OCT images by correspondingly marked graphical representations and/or photographic images of the patient&#39;s body, which are also called “body maps”. 
       FIG. 11  shows an example of a window on the display  52  of the OCT system  50  (see  FIG. 2 ), where OCT images  60 ,  61  are displayed together with graphical representations of corresponding body parts including corresponding marks and further textual information, e.g. date of consultation and clinical findings and/or symptoms. Preferably, the system is configured such that the OCT images  60 ,  61  can be dragged (see arrows A and B) from a displayed list of downscaled OCT images  60 ′,  61 ′ to a viewer window section, where enlarged image  60 ,  61  are displayed. 
     As already elucidated above, it is preferred to assign additional information relating to the object, like photographic images and/or a graphical representation of the object and/or additional text information, to an OCT image by incorporating data of the data file of the additional information into the data file of the corresponding OCT image. For example, data of a photographic or graphical image data file of a first data format, like JPEG, TIFF or GIF, are incorporated into the OCT image data file of a second data format, in particular DICOM. This will be elucidated in more detail in the following. 
     Digital Imaging and Communications in Medicine (DICOM) is a standard for handling, storing, printing and transmitting information in medical imaging. It includes a file format definition and a network communications protocol. The communication protocol is an application protocol that uses TCP/IP to communicate between systems. 
     In DICOM format, information is grouped into data sets, which means that a file of an OCT image actually contains, i.a., the patient ID within the file, so that the OCT image cannot be separated from this information by mistake. A DICOM data file consists of a number of attributes, including items such as patient name, ID, etc., and one special attribute containing the OCT image pixel data (a single DICOM object can have only one special attribute containing pixel data). Within the meaning of the present invention, a DICOM data file comprises a “header” in form of a list of attributes, like patient ID, as well as only one special attribute in form of pixel data of a single OCT image. 
       FIG. 12  shows a first schematic representation of the contents of an OCT image data file in DICOM format. The present representation has been established by a DICOM viewer tool which shows a list of attributes  75 , i.e. a header, from which “patient&#39;s name” was selected. In field  76  storage addresses (left column) and their content (hexadecimal) are displayed, wherein the highlighted sequence contains the patient&#39;s name in hexadecimal, which is also displayed in cleartext in field  77  (also highlighted). 
     After scrolling down the list of attributes  75  and selecting “frame data”, as shown in  FIG. 13 , in field  76  storage addresses (left column) and content (highlighted) of additional photographic and/or graphical image data relating to the present patient and/or the OCT image obtained from the patient are displayed. As apparent from  FIG. 13 , additional photographic and/or graphical image data (highlighted) are incorporated in the “header” (list of attributes) of the DICOM file, which also contains OCT image pixel data (not shown) as a special attribute. 
     By the above-mentioned incorporation of photographic and/or graphical image data into the header of the OCT image data file, which is preferably in DICOM format, a particularly reliable assignment or correlation of additional information relating to the object, on the one hand, to/with an OCT image, on the other hand, is achieved, so that, when retrieving an accordingly stored OCT image data file, corresponding additional information, in particular photographic and/or graphical image data, is retrieved at the same time and vice versa. Accordingly, the OCT image cannot be separated from this additional information by mistake.