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Researchers Submit Patent Application, "Control Device, Control Method and Control Program for Optical Coherence Tomographic Image-Generating...

August 1, 2014



Researchers Submit Patent Application, "Control Device, Control Method and Control Program for Optical Coherence Tomographic Image-Generating Apparatuses", for Approval

By a News Reporter-Staff News Editor at Health & Medicine Week -- From Washington, D.C., NewsRx journalists report that a patent application by the inventor Kakuma, Hideo (Chiba, JP), filed on January 16, 2012, was made available online on July 17, 2014 (see also The Yoshida Dental Mfg. Co., Ltd.).

The patent's assignee is The Yoshida Dental Mfg. Co., Ltd.

News editors obtained the following quote from the background information supplied by the inventors: "Conventionally, optical coherence tomography apparatuses (hereinafter, referred to as OCT apparatuses) have been applied to ophthalmic practice such as tomographic imaging of a cornea and/or a retina of an eye in the biomedical fields. The OCT allows for non-invasive and non-contact diagnosis by irradiating a living tissue with light. Examples of a known diagnostic system other than the OCT include: CT (Computed Tomography) with resolution of 200 micrometers or less; MRI (Magnetic Resonance Imaging) with resolution of 800 micrometers or less; and PET (Positron Emission Tomography) with resolution of 1000 micrometers or less. Compared with these systems, the OCT can achieve by far superior resolution from several to several dozens micrometers, and can display a high-resolution precise image. It has been known that the OCT systems can be classified roughly into TD (Time Domain)-OCT and FD (Frequency Domain)-OCT. The latter FD-OCT can be further classified into SD (Spectrum Domain)-OCT and SS (Swept Source)-OCT.

"For example, in the SS-OCT, a laser source is used to continuously sweep wavelengths (wave numbers); and spectral information as obtained using a detector is subject to FFT (Fast Fourier Transform) processing to specify an optical path length. The SS-OCT has a higher resolution than X-ray equipment and CT devices, which are widely used in dental practice, and is characterized in that a real-time measurement can be performed without being exposed to radiation.

"Meanwhile, the above-described TD-OCT has been tested for dental practice. The SS-OCT, however, can acquire data faster with higher sensitivity than the TD-OCT. Thus, the SS-OCT has a motion artifact (a ghost due to body movement)-resistant feature.

"In order to obtain a tomogram, the OCT apparatus requires two-dimensional mechanical scanning in a widthwise direction (a left-right direction with respect to an object) and in a lengthwise direction (a front-rear direction with respect to the object), which are perpendicular to a laser beam direction (a vertical or depthwise direction with regard to the object) facing the object. Unfortunately, the imaging and diagnosis conventionally take a long time.

"A technology (see JP2010-142428A) regarding an ophthalmic OCT apparatus has been known that prior to acquisition of a detailed image used for diagnosis, an overview of an object is obtained.

"An imaging apparatus disclosed in JP2010-142428A includes: a tomographic image acquisition section whose function is implemented by an OCT apparatus; and a front image acquisition section whose function is implemented by a fundus camera or an SLO (Scanning Laser Ophthalmoscope) to acquire a front image. The front image acquisition section is to obtain an overview of an object.

"In addition, in the dental fields, a handpiece for a dental optical diagnostic apparatus includes OCT means. Then, means for positioning an optical diagnosis site in a tooth is implemented by a camera imaging system, which includes an imaging camera for acquiring a surface image (see Japanese Utility Model Registration Application No. 3118718). Accordingly, the camera image can be used for prior positioning."

As a supplement to the background information on this patent application, NewsRx correspondents also obtained the inventor's summary information for this patent application: "Problems To Be Solved By the Invention

"However, a conventional apparatus beforehand obtains a surface image while a tomogram should be obtained as an image taken for determination of a detailed image used for diagnosis (detailed imaging). Unfortunately, it takes a long time to acquire a desired tomogram used for diagnosis.

"Here, the present invention has resolved the above problems. It is an object of the present invention to provide a controller, a control method, and a control program for an optical coherence tomography apparatus allowing for fast acquisition of a desired tomogram of an object.

"Means For Solving the Problems

"In order to solve the above problems, the present invention relates to a controller for an optical coherence tomography apparatus, the optical coherence tomography apparatus includes: an optical unit including: a light source for periodically emitting laser beam on an object; and a detector for detecting internal information of the object; a probe including; a scanning mechanism which can perform two-dimensional scanning with the laser beam, the probe guiding the laser beam emitted through the optical unit to the object and guiding light reflected by the object to the optical unit; and a control unit including: the controller for controlling generation of an optical coherence tomogram of the object from data converted from a detection signal of the detector while performing imaging by controlling the scanning mechanism in synchrony with the laser beam; and a display for displaying the optical coherence tomogram, including: an imaging control means for imaging with a predetermined imaging mode based on an external input; and an image-processing means for performing image processing of the detection signal as obtained at the imaging, wherein the imaging control means includes: a first imaging control means for starting imaging when it is determined to receive an input of a measurement command to scan an imaging range of the object with the laser beam at a predetermined pitch by using the scanning mechanism so as to determine the internal information of the object and for stopping the imaging after an imaging time according to the predetermined pitch; and a second imaging control means for starting imaging when it is determined to receive an input of a preview command to scan the imaging range with the laser beam at a larger pitch than the predetermined pitch by using the scanning mechanism and for stopping the imaging when it is determined to receive an input of a command to cancel the preview command.

"According to such a configuration, the controller for the optical coherence tomography apparatus uses the first imaging control means to start imaging the object when receiving the measurement command. Next, the controller uses the image-processing means to perform image processing of the detection signal as obtained using the scanning mechanism by scanning the object with laser beam at a predetermined pitch. Then, the display displays an optical coherence tomogram of the object at a predetermined resolution. At this time, the imaging is terminated after an imaging time according to a scanning pitch of the scanning mechanism. Consequently, after completion of the imaging, the display displays a still image of the optical coherence tomogram. Here, when a rectangular imaging range is segmented into 300 points in length and width and the measurement is performed for imaging, for example, the scanning mechanism repeats a small movement and stop 300 times per side. When the measurement for imaging is performed at these 300 points, it takes a shorter period to complete imaging than that at 400 points. In addition, the controller for the optical coherence tomography apparatus uses the second imaging control means to start imaging the object when receiving the preview command. Next, the controller uses the image-processing means to perform image processing of the detection signal as obtained using the scanning mechanism by scanning the object with the laser beam at a larger pitch than the predetermined pitch. Then, the display displays an optical coherence tomogram of the object at a lower resolution than the predetermined resolution. When the optical coherence tomogram is displayed by the preview command, the detection signal is used that has been obtained by scanning the object at a larger pitch than that used in the optical coherence tomogram displayed by the measurement command. Accordingly, the optical coherence tomogram can be displayed faster. For example, a rectangular imaging range is segmented into 128 points in length and width and the preview imaging is performed. At that time, it takes a shorter period to complete imaging than that at 300 points or 400 points. In addition, with regard to the optical coherence tomogram at a low resolution, the imaging and image processing continue until a command to cancel the preview command is input. Accordingly, the optical coherence tomogram obtained can be displayed as a real-time moving image. Note that no resolution variation is observed in a direction along an optical axis toward the object.

"In addition, the controller for an optical coherence tomography apparatus according to an embodiment of the present invention preferably includes a foot controller connected to the imaging control means in wired or wireless communication in a configuration having received an input of the preview command and an imaging command, the foot controller including a first switch and a second switch, wherein when a user uses his/her foot to operate either the first switch or the second switch, the imaging control means is informed of a first or second switch signal corresponding to the first or second switch; when the second imaging control means receives an input of the first switch signal from the foot controller, it is determined to receive an input of the preview command; when the second imaging control means receives an input of the second switch signal from the foot controller, it is determined to receive an input of a command to cancel the preview command; and when the first imaging control means receives an input of the second switch signal from the foot controller, it is determined to receive an input of the measurement command.

"In such a configuration, the controller for the optical coherence tomography apparatus uses the second imaging control means to determine that an input of the preview command is received when a user uses his/her foot to operate the first switch of the foot controller. In addition, the controller uses the first imaging control means to determine that an input of the measurement command is received while canceling the preview command when the user uses his/her foot to operate the second switch of the foot controller. This configuration allows the user to press the foot controller by his/her foot when the user makes a diagnostic probe section contact a patient during imaging even if his/her both hands are occupied. This makes it possible to input the preview command and/or the measurement command even in the above situation. This improves operability.

"Further, the controller for an optical coherence tomography apparatus according to an embodiment of the present invention preferably includes scanning-area-selection-controlling means for controlling selection of a range scanned by the scanning mechanism according to an area of interest, wherein the area is selected by the user from a plurality of predetermined different areas as imaging ranges for the object; and the area is input to the imaging control means.

"In such a configuration, the controller for the optical coherence tomography apparatus can use the scanning-area-selection-controlling means to control and select the range scanned by the scanning mechanism according to the area selected by the user from the plurality of the different areas. This improves operability. In such a configuration, the controller for the optical coherence tomography apparatus may have the fixed number at which the small movement and stop of the scanning mechanism is repeated so as to take a series of images of the object. At that time, changing the area of the imaging range enables the scanning pitch of the scanning mechanism to be changed. This can increase resolution of the image obtained. For example, a small rectangular imaging range may be segmented into 400 points in length and width. That case should have a higher resolution than the case where a large rectangular imaging range is segmented into 400 points in length and width. Accordingly, an image is taken with the widest range. Next, an area of interest on the object is targeted. Then, the image is narrowed to the smallest range. This procedure makes it possible to display the targeted area of interest at a higher resolution.

"Furthermore, in the controller for an optical coherence tomography apparatus according to an embodiment of the present invention, the image-processing means preferably uses data obtained by taking an image of the object to generate: an optical coherence tomogram with respect to a tomographic plane in a direction along an optical axis toward the object; a two-dimensional image with respect to a scanning plane perpendicular to the optical axis toward the object; and a three-dimensional image of the object, wherein the image-processing means controls and displays each generated image on one page of the display as image information regarding the object.

"Such a configuration makes it possible for the controller for the optical coherence tomography apparatus to display the optical coherence tomogram, the two-dimensional image with regard to the scanning plane of the object, and the three-dimensional image of the object on one page of the display. Accordingly, the user can intuitively recognize which part of the object and which tomographic plane the displayed optical coherence tomogram represents.

"In addition, in the controller for an optical coherence tomography apparatus according to an embodiment of the present invention, the image-processing means preferably generates, as the two-dimensional image with regard to the scanning plane perpendicular to the optical axis toward the object, an en-face image which combines information on the surface of the object irradiated with the laser beam and information on the object in a direction along the optical axis.

"Such a configuration allows the controller for the optical coherence tomography apparatus to construct the two-dimensional image with respect to the scanning plane of the object, which two-dimensional image is displayed together with the optical coherence tomogram and the three-dimensional image of the object, from data obtained using image-processing of the signal detected by the OCT. Consequently, not only information on the outer surface of the object but also internal information is superimposed to construct the two-dimensional image. Thus, this two-dimensional image can be used for measurement and/or diagnosis. Also, such a configuration circumvents a need to install a camera member, etc., specialized for obtaining a two-dimensional image with regard to a scanning plane of the object. Because of this, for example, a camera does not have to be installed in a probe, so that the probe can be made smaller.

"Moreover, the present invention relates to a method for controlling an optical coherence tomography apparatus, the optical coherence tomography apparatus includes: an optical unit including: a light source for periodically emitting laser beam on an object; and a detector for detecting internal information of the object; a probe including: a scanning mechanism which can perform two-dimensional scanning with the laser beam, the probe guiding the laser beam emitted through the optical unit to the object and guiding light reflected by the object to the optical unit; and a control unit including: the controller for controlling generation of an optical coherence tomogram of the object from data converted from a detection signal of the detector while performing imaging by controlling the scanning mechanism in synchrony with the laser beam; and a display for displaying the optical coherence tomogram, including the steps of: stating imaging when it is determined to receive an input of a measurement command to scan an imaging range of the object with the laser beam at a predetermined pitch by using the scanning mechanism so as to determine the internal information of the object and stopping the imaging after an imaging time according to the predetermined pitch, as one of predetermined imaging modes based on an external input for a controller; starting imaging when it is determined to receive an input of a preview command to scan the imaging range with the laser beam at a larger pitch than the predetermined pitch by using the scanning mechanism and stopping the imaging when it is determined to receive an input of a command to cancel the preview command, as another of the predetermined imaging modes based on an external input for the controller; and image-processing a detection signal as obtained by the imaging of either imaging mode.

"According to such a procedure, first, the method for controlling an optical coherence tomography apparatus can use a preview command to display an optical coherence tomogram at a low resolution, that is, an image at a desired tomographic plane, by using the detection signal as obtained by scanning the object with laser beam at a larger pitch. Next, the preview command can be canceled. Then, the method can use a measurement command to display an optical coherence tomogram at a high resolution, that is, an image at the desired tomographic plane, by using a detection signal as obtained by scanning the object with the laser beam with a smaller pitch. Note that the measurement command may include a command to cancel the preview command. Also, such a procedure, for example, makes it possible to beforehand obtain, at a lower resolution, an optical coherence tomogram similar to an optical coherence tomogram used for measurement and/or diagnosis by using the preview command. Besides, the preview command can be used to make it easy to repeatedly display different optical coherence tomograms at a low resolution. Accordingly, the user can quickly find out a desired tomographic plane as a tomogram of the object. This information can be used to allow for fast acquisition of a desired tomogram at a high resolution.

"Finally, the present invention relates to a program for controlling an optical coherence tomography apparatus, in which each means of the controller for an optical coherence tomography apparatus according to the above is used to make a computer function. Such a configuration enables each function based on this program to be implemented in the computer having this program installed thereon.

"Effect of the Invention

"The present invention makes it possible for a controller for an optical coherence tomography apparatus to quickly obtain a desired tomogram of an object.

BRIEF DESCRIPTION OF THE DRAWINGS

"FIGS. 1A-1B are outline views of optical coherence tomography apparatuses according to embodiments of the present invention;

"FIG. 1A illustrates an apparatus with a single-joint arm;

"FIG. 1B illustrates an apparatus with a multiple-joint arm;

"FIG. 2 is a schematic view illustrating how to configure units for an optical coherence tomography apparatus according to an embodiment of the present invention;

"FIG. 3 is a block diagram illustrating functions of an OCT controller according to an embodiment of the present invention;

"FIGS. 4A-4B illustrate how to take an image by using an optical coherence tomography apparatus according to an embodiment of the present invention;

"FIG. 4A describes types of recording area;

"FIG. 4B is a schematic diagram illustrating an optical path of laser beam which passes through the inside of a diagnostic probe;

"FIGS. 5A-5B illustrate how to generate OCT images by means of an OCT controller according to an embodiment of the present invention;

"FIG. 5A is an image showing internal information as obtained along with an A-scan and a B-scan of a sample;

"FIG. 5B is images showing internal information as obtained along with an A-scan, a B-scan, and a V-scan;

"FIG. 6 is a flowchart illustrating how to perform processing so as to display an OCT image by using an OCT controller according to an embodiment of the present invention;

"FIG. 7 is a flowchart illustrating how to perform processing so as to display an en-face image by using an OCT controller according to an embodiment of the present invention;

"FIGS. 8A-8E show an example of a timing chart for image-processing by an OCT controller according to an embodiment of the present invention;

"FIG. 8A illustrates a sweep trigger for a light source output;

"FIG. 8B illustrates a start trigger for a D/A converter circuit output;

"FIGS. 8C and 8D illustrate analog output voltages in X and Y directions as output from a galvanometer mirror control circuit;

"FIG. 8E illustrates a clock to generate an OCT image;

"FIG. 9 shows a screen display example regarding image information as obtained using preview imaging by an OCT controller according to an embodiment of the present invention; and

"FIG. 10 shows a screen display example regarding image information as obtained using detailed imaging by an OCT controller according to an embodiment of the present invention."

For additional information on this patent application, see: Kakuma, Hideo. Control Device, Control Method and Control Program for Optical Coherence Tomographic Image-Generating Apparatuses. Filed January 16, 2012 and posted July 17, 2014. Patent URL: http://appft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=%2Fnetahtml%2FPTO%2Fsearch-adv.html&r=3860&p=78&f=G&l=50&d=PG01&S1=20140710.PD.&OS=PD/20140710&RS=PD/20140710

Keywords for this news article include: Dentistry, The Yoshida Dental Mfg. Co., The Yoshida Dental Mfg. Co. Ltd.

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Source: Health & Medicine Week


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