JP2006280449A - Diagnostic imaging system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress reduction in frame rate by simultaneously displaying ultrasound tomographic images and high-resolution optical tomographic images. <P>SOLUTION: An ultrasonic transducer 81 and an irradiation means 82 are formed in an integrated fashion at the end of a probe 2. Ultrasound tomographic images are generated by ultrasonic waves transmitted by the ultrasonic transducer 81 and optical tomographic images are generated by using interference light of the light emitted from the irradiation means 82. In this case, a region of interest is set in a limited area of the ultrasound tomographic image and the ultrasound tomographic image and the optical tomographic image only in the region of interest are simultaneously displayed on a screen of a monitoring device 3. Also, in the case of the TD-OCT system, the probe 2 is rotated at a speed which allows OCT scanning in the set region of interest and the probe 2 is rotated at a speed which allows ultrasonic scanning in the rest of the region. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an image diagnostic apparatus capable of acquiring an ultrasonic tomographic image and an optical tomographic image using light interference.

  Generally, when acquiring a tomographic image of a body tissue, an ultrasonic tomographic image diagnostic apparatus using ultrasonic waves is used. The ultrasonic tomographic image diagnosis apparatus is roughly composed of an ultrasonic probe having an ultrasonic transducer provided at the tip thereof and an ultrasonic observation apparatus to which the ultrasonic probe is connected in an detachable manner. The ultrasonic transducer provided at the tip of the ultrasonic probe is driven and controlled by the ultrasonic observation device, transmits the ultrasonic wave to the subject, receives the reflected echo, converts it to a received signal, Output to. Then, after predetermined signal processing is performed in the ultrasonic observation apparatus, an ultrasonic tomographic image is displayed by a monitor device connected to the ultrasonic observation apparatus.

  On the other hand, an image diagnostic apparatus using OCT (Optical Coherence Tomography) is becoming widespread as an apparatus for acquiring an optical tomographic image of a body tissue or the like using light interference. There are roughly three types of scanning by OCT. One of them is called TD (Time Domain) -OCT. This method outputs low-coherence light from a light source, splits the low-coherence light into measurement light and reference light, and reflects the reflected light of the measurement light guided to the subject and the reference light reflected by the reference surface. Optical tomographic information at a predetermined depth of the subject is acquired by causing interference with light. The obtained optical tomographic information is subjected to predetermined signal processing in the computer, and then displayed as an optical tomographic image on a monitor device connected to the computer.

  The other is called SS (Swept Source) -OCT. In this method, the wavelength (frequency) of the light source is changed at a constant period by an external resonator or the like, and the frequency of the emitted light is temporally changed. This light is branched into measurement light and reference light, and the reflected light from the observed (measured) body of the measurement light and the reflected light reflected by the reference surface are combined and interfere. Since the interference light includes intensity information at each depth of the subject for each wavelength band (for each frequency band), by performing frequency analysis by Fourier transform on the detected interference light signal, Obtain optical tomographic information in a certain range in the vertical direction.

  Another method is called SD (Spectral Domain) -OCT. In this method, low-coherence light is emitted from a light source, and an optical tomographic image is obtained by Fourier transform on the spectral intensity distribution of reflected light from the subject. For this reason, wavelength separation is performed by the spectrum spectrometer on the interference light after the reflected light of the measurement light and the reflected light of the reference light are combined, and the line detector is used for each wavelength band (for each frequency band). To detect. Then, frequency analysis is performed by Fourier transform, and optical tomographic information in a certain range in the depth direction is acquired.

  SS-OCT fluctuates the wavelength (frequency) of light source light at a constant period, and SD-OCT acquires optical tomographic information in the depth direction by performing wavelength decomposition using a spectrum spectrometer. . Therefore, while TD-OCT drives the reference plane to acquire optical tomographic information in the depth direction, both SS-OCT and SD-OCT do not need to drive the reference plane and are fixed, Optical tomographic information can be acquired at high speed.

  Here, in any method of OCT scanning, since OCT scanning uses light interference information, scanning can be performed with high resolution. For this reason, an optical tomographic image with high resolution can be acquired. However, since OCT scanning uses light, an image at a deep depth cannot be acquired from the surface of the subject. On the other hand, ultrasonic scanning can acquire an image with a deep depth, but cannot acquire an image with a resolution as high as that of OCT scanning.

Therefore, a light guiding means for guiding low-coherence light and an ultrasonic transducer for transmitting ultrasonic waves are integrally formed at the probe tip, and a high-resolution optical tomographic image by OCT at a depth near the surface of the subject. For example, Patent Document 1 discloses that an ultrasonic tomographic image is acquired at a deeper depth of an affected area.
JP 11-56752 A

  By the way, OCT scanning is performed with very high resolution compared to ultrasonic scanning. Here, in Patent Document 1, OCT scanning is performed over the entire range in which OCT scanning can be performed (all ranges in the radial direction), and display is performed. Since the ultrasonic tomographic image and the optical tomographic image have a difference in information amount depending on the resolution, the same monitor device is used as disclosed in Patent Document 1, and the region is divided into two. When displaying on the same (or almost the same) scale, it is necessary to display the optical tomographic image after performing reduction processing (mainly thinning processing). That is, since the resolution differs greatly between the ultrasonic scanning and the OCT scanning, the acquired optical tomographic image also has an extremely large amount of information with respect to the ultrasonic tomographic image. Therefore, if no reduction process is performed on the optical tomographic image, the optical tomographic image has a scale with a magnification depending on the resolution ratio as compared with the ultrasonic tomographic image. In other words, the optical tomographic image is enlarged and displayed with respect to the ultrasonic tomographic image at an enlargement ratio corresponding to the ratio between the ultrasonic scanning resolution and the OCT scanning resolution. For example, if the resolution of the OCT scanning is n times higher than the resolution of the ultrasonic scanning, the optical tomographic image has an information amount n times that of the ultrasonic tomographic image, and the enlargement ratio thereof. Is also displayed in n times. Therefore, when the ultrasonic tomographic image and the optical tomographic image are displayed on the same scale by dividing the region of the same monitor device into two, it is necessary to perform a reduction process according to the resolution ratio and display it.

  For this reason, the OCT scanning can be performed with a very high resolution, but the original reduction of the OCT that scans with a high resolution is lost because a reduction process is performed when displaying. become. In other words, an image that can be originally displayed at a high resolution is displayed after being reduced, so that an optical tomographic image cannot be displayed at a high resolution.

  Of course, if an optical tomographic image and an ultrasonic tomographic image are displayed on separate monitor devices and the optical tomographic image is displayed on a monitor device having a resolution higher than the resolution of the monitor device displaying the ultrasonic tomographic image, it should be applied. The amount of reduction processing can be suppressed to some extent. However, since the resolution of OCT in recent years tends to be very high, even if separate monitor devices with different resolutions are used, the above problem cannot be solved.

  In addition, the ultrasonic tomographic image and the optical tomographic image are subjected to predetermined signal processing. However, since the ultrasonic tomographic image has a smaller amount of information than the optical tomographic image, the ultrasonic tomographic image is obtained in a relatively short time. Signal processing can be performed on the image. However, since an optical tomographic image has a very large amount of information compared to an ultrasonic tomographic image, signal processing performed on the optical tomographic image requires a very long time. Therefore, there is a problem that the speed at which the optical tomographic image is imaged cannot keep up with the speed at which the ultrasonic tomographic image is imaged.

  The above-mentioned problem is a problem that occurs in any of TD-OCT, SS-OCT, and SD-OCT. For TD-OCT, an ultrasonic tomographic image that can be acquired within a certain period of time when an optical tomographic image is generated. There is also a problem that the number of sheets, that is, the frame rate is lowered.

  In the case of ultrasonic scanning, the ultrasonic reflected wave transmitted from the ultrasonic transducer is received to form an ultrasonic tomographic image for one line signal, and the ultrasonic transducer is moved in the radial direction or linear direction. To generate a two-dimensional ultrasonic tomographic image. On the other hand, in the case of TD-OCT scanning, only information of a predetermined depth is acquired corresponding to the position of the reference plane. Therefore, in order to generate a one-line signal, the reference plane is only a distance corresponding to the one-line signal. It is necessary to change the optical path length by driving the position. Therefore, compared with the case of receiving an ultrasonic reflected wave, the TD-OCT scan needs to change the position of the reference plane in order to form a one-line signal. The formation speed is lower than that of the ultrasonic tomographic image. For this reason, the moving speed of the probe in the radial direction or linear direction is lower in the TD-OCT scanning than in the ultrasonic scanning. As in the invention of Patent Document 1, when scanning is performed by integrally forming an ultrasonic transducer and a light guide unit on a probe, it is necessary to adjust the moving speed or rotational speed of the probe to the scanning by TD-OCT. If the scanning by the TD-OCT is followed, the scanning speed by the ultrasonic wave becomes lower than the original scanning speed, so that there is a problem that the frame rate of the ultrasonic tomographic image is lowered.

  Therefore, an object of the present invention is to provide an image diagnostic apparatus that can simultaneously display an ultrasonic tomographic image and a high-resolution optical tomographic image and solve the problem of a decrease in the frame rate of the ultrasonic tomographic image. To do.

  The diagnostic imaging apparatus of the present invention irradiates the subject with the ultrasonic transducer that ultrasonically scans a predetermined range of the subject and the measurement light from the light source at the tip of the probe having the flexible tube, A light irradiating means for receiving the reflected light is integrally formed, an ultrasonic image generating means for generating an ultrasonic image based on a reflected echo received by the ultrasonic transducer, and the measurement light is derived to the subject. Optical tomographic image generation means for generating an optical tomographic image by performing optical scanning of the subject using interference between the reflected light of the reference light branched from the light source and the reflected light from the subject A region of interest in a part of the ultrasonic image generated by the ultrasonic image generation means is set, and the ultrasonic image and an optical tomographic image of only the set region of interest are simultaneously displayed on the screen It is characterized by being displayed above.

  The diagnostic imaging apparatus of the present invention can simultaneously display an ultrasonic tomographic image and a high-resolution optical tomographic image, and does not require a long time for signal processing of the optical tomographic image. In TD-OCT, it is possible to further suppress a decrease in frame rate.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a case where TD-OCT is applied, FIG. 2 shows a case where SS-OCT is applied, and FIG. 3 shows an outline of a signal processing apparatus 1 constituting the diagnostic imaging apparatus of the present invention when SD-OCT is applied. A block diagram is shown.

  As shown in FIGS. 1 to 4, the diagnostic imaging apparatus of the present invention includes a signal processing device 1, a probe 2, a monitor device 3, and an input unit 4, and the probe 2 and the monitor device 3 are respectively provided. Connected to the signal processing device 1. The above is common to the OCT of each method, and the configuration of the signal processing apparatus 1 differs depending on each method. Hereinafter, each method will be described separately.

A. When TD-OCT is applied First, a case where TD-OCT is applied will be described with reference to FIG. As shown in FIG. 1, the signal processing apparatus 1 includes an ultrasonic observation apparatus 5 that generates an ultrasonic tomographic image and an OCT observation apparatus 6 that generates an optical tomographic image. A transmission / reception unit 51, an A / D (Analog Digital Converter) 52, a line memory 53, a scan converter 54, a scan controller 55, a ROI (Region of Interest) controller 56, and a D / A (Digital Analog Converter) 57. The OCT observation apparatus 6 includes an A / D 61, a line signal memory 62, a scan converter 63, a scan controller 64, a reflector controller 65, and a D / A 66, and further includes an OCT control unit 7. The OCT control unit 7 includes a light source 71, an optical branching unit 72, a reflector 73, and a photodetector 74. The photodetector 74 is connected to the A / D 61, and the reflector 73 is connected to the reflector controller 65.

  The transmission / reception unit 51 of the ultrasonic observation apparatus 5 is connected to an ultrasonic transducer (ultrasonic transducer 81 to be described later) disposed at the tip of the probe 2, and transmits a drive signal and a reception signal from the ultrasonic transducer. Receive. The received signal is converted from an analog signal to a digital signal by the A / D 52 and input to the line memory 53. A scan converter 54 is connected to the line memory 53, and the received signal stored in the line memory 53 is converted in the scanning direction of the ultrasonic tomographic image by the scan converter 54, and one frame of the ultrasonic tomographic image is converted. It is formed. Then, the formed ultrasonic tomographic image of one frame is stored in the scan converter 54. In order to form one frame of the ultrasonic tomographic image, a scan controller 55 is provided for controlling switching between the transmission side and the reception side of the transmission / reception unit 51 and capturing of signals into the scan converter 54. When an ultrasonic tomographic image for one frame is formed, it is input to the D / A 57 via the ROI controller 56 for setting a region of interest (ROI), and converted from a digital signal to an analog signal. Later, it is output to the monitor device 3 and an ultrasonic tomographic image is displayed on the monitor device 3.

  Next, the OCT observation apparatus 6 will be described. In the OCT control device 7 included in the OCT observation device 6, light emitted from a light source 71 (for example, a light source that emits light having low coherence such as SLD (Super Luminescent Diode)) is measured by an optical branching unit 72. The measurement light Ls is branched into light Ls and reference light Lr, and the measurement light Ls is guided to light irradiation means (light irradiation means 82 described later) connected to the probe 2. Then, the reflected light from the subject enters the light branching portion 72 again as detection light. On the other hand, the reference light Lr is reflected by a reflector 73 configured by a reflecting mirror or the like, and enters the light branching unit 72 as reflected light. The detection light of the measurement light Ls and the reflected light of the reference light Lr are combined at the optical branching unit 72, and the interference light is detected at the photodetector 74. Thereby, optical scanning is performed, and a tomographic image of a predetermined depth in the subject can be acquired. That is, when the optical path length of the measurement light Ls and the optical path length of the reference light Lr substantially coincide with each other, the detection light from the subject and the reflected light from the reflector 73 show interference for the first time. What is necessary is just to control the optical path length of the light Lr. Since the optical path length of the reference light Lr is uniquely determined by the position of the reflector 73, the optical tomographic information in the depth direction in the subject can be acquired by driving the position of the reflector 73.

  As described above, interference light is detected by the light detection unit 74. Since the interference light is tomographic information at a predetermined depth of the subject, in order to acquire tomographic information in a certain range in the depth direction, It is necessary to change the position of the reflector 73. Accordingly, by moving the reflector 73 by an amount corresponding to the scanning range in the depth direction, it is possible to generate one line signal of the optical tomographic image. The photodetection unit 74 photoelectrically converts the interference light to generate a reception signal, and the position of the reflector 73 is changed to generate one line of reception signal (one line signal). This one-line signal can be handled as a signal similar to the reception signal by the ultrasonic transducer.

  The one line signal is output to the A / D 61 of the OCT observation apparatus 6, converted from an analog signal to a digital signal, and then output to the line memory 62. Then, similarly to the ultrasonic observation apparatus, the received signal is taken from the line memory 62 to the scan converter 63 and the scanning direction is converted to generate an optical tomographic image for one frame. Then, the optical tomographic image for one frame is stored in the scan converter 63. At this time, a scan controller 64 and a reflector controller 65 are provided in order to perform control of taking in one line signal into the scan converter 63. The scan controller 64 controls the signal capture timing based on a rotation angle detected by an encoder (encoder 110 described later) connected to the proximal end side of the probe 2, and the reflector controller 65 is an OCT control device 7. This is for controlling the position of the reflector 73. When the optical tomographic image for one frame is captured by the scan converter 63, the D / A 66 converts the digital signal into an analog signal, and the optical tomographic image is displayed on the screen of the monitor device 3.

  Next, the probe 2 will be described. FIG. 4 is a diagram showing the configuration of the probe 2. The ultrasonic transducer 81 and the light irradiation means 82 are integrally formed at the distal end portion 2 A of the probe 2, and the ultrasonic transducer 81 and the light irradiation means 82 are rotated coaxially by a rotation block 86. When the drive pulse from the ultrasonic observation apparatus 5 is applied, the ultrasonic transducer 81 transmits the ultrasonic wave toward the subject, converts the reflected echo into a reception signal, and transmits the received signal to the ultrasonic observation apparatus 5. To do. Therefore, the scanning direction of the ultrasonic waves is a radial direction, and the scanning plane is a direction orthogonal to the rotation axis 104 of the rotating block 86. The light irradiation means 82 has a function of condensing the light from the OCT observation apparatus 6, and the light emitted from the light irradiation means 82 is reflected at a right angle by the prism 83 and condensed at a predetermined depth of the subject. Irradiated as follows. As a result, the optical scanning direction substantially coincides with the ultrasonic scanning direction. The reflected light from the subject is fed back as detection light to the OCT observation apparatus 6 via the prism 83 and the light irradiation means 82 again. For this reason, as a material of the light irradiation means 82, for example, a GRIN lens whose refractive index changes steplessly is used in order to condense the light of the diverging optical fiber. A signal line 84 is connected to the ultrasonic transducer 81 so that signals can be exchanged with the ultrasonic observation device 5 of the signal processing apparatus 1, and a fiber 85 is connected to the light irradiation means 82. Then, the measurement light from the OCT observation apparatus 6 is guided, and the measurement light is irradiated toward the subject by the light irradiation means 82 and the prism 83 fixed to the light irradiation means 82. Further, the signal line 84 and the fiber 85 are combined into a single cable 89. A flexible shaft 91 made of a double or triple dense supercoil or the like wound in opposite directions is connected to the rotating block 86, and the cable 89 is inserted into the flexible shaft 91. The flexible shaft 91 rotates by the rotational driving force of the motor 101 connected to the proximal end side. A sleeve 92 is provided so as to enclose these members. At least the tip of the sleeve 92 is made of a transparent member so that light can pass through.

  On the proximal end side 2 </ b> B of the probe 2, a rotatable first electrode cylinder 93 and a second electrode cylinder 95 connected to the signal line 84 are provided on the outer periphery of the fiber 85 included in the cable 89. Between them, a rotatable insulating cylinder 94 is interposed. Either the first electrode cylinder 93 or the second electrode cylinder 95 is connected to the ground electrode, and the other is connected to the ultrasonic observation apparatus 5 to exchange signals. The fixed cylinder 97 is a member for holding the rotating member in a rotatable manner. The fixed cylinder 97 has a bearing 96 therein and is connected to the sleeve 92. Therefore, the fiber 85 connected to the light irradiation means 82, and the first electrode cylinder 93 and the second electrode cylinder 95 connected to the ultrasonic transducer 81 are rotated together.

  The proximal end 2B of the probe 2 is connected to the drive connector 100 as shown in FIG. The drive connector 100 includes a motor 101, and the driving force of the motor 101 is transmitted to the gear 103 via the drive unit 102, and the rotation shaft 104 is rotated by the rotation of the gear 103. Accordingly, when the proximal end portion 2B of the probe 2 is connected to the rotating shaft 104, the fiber 85, the first electrode cylinder 93, and the second electrode cylinder 95 are also rotated. An encoder 110 is connected to the motor 101, and the rotation angles of the ultrasonic transducer 81 and the light irradiation means 82 can be detected from the rotation angle of the motor 101.

  The monitor device 3 is a display device for displaying an ultrasonic tomographic image and an optical tomographic image, and is connected to the D / A 57 of the ultrasonic observation device 5 and the D / A 66 of the OCT observation device 6 in the example of FIG. . Therefore, the screen of the monitor device 3 may be divided into two regions, and an ultrasonic tomographic image and an optical tomographic image may be displayed in each region, or one screen may be a main screen, A so-called picture-in-picture method in which the screen is embedded may be employed. In addition, when there is room to install a plurality of monitor devices, two monitor devices may be prepared and an ultrasonic tomographic image and an optical tomographic image may be displayed respectively. It is preferable that the ultrasonic tomographic image and the optical tomographic image are displayed at the same time, but this does not prevent the display from being switched.

  The input unit 4 is an input device for setting a region of interest, and sets a region for OCT scanning with reference to an ultrasonic tomographic image displayed on the monitor device 3. As the input means 4, for example, a trackball, a mouse, a keyboard or the like is applied.

  What has been described above has been described by taking an example of performing radial scanning, but of course, the invention is not limited to this and can also be applied to linear scanning. In FIG. 2, the ultrasonic transducer 81 and the light irradiation means 82 (including the prism 83) are illustrated as being 180 ° out of phase, but are directed to any direction including the same direction. It is also possible to adopt a configuration to be used.

B. When SS-OCT is applied

  Next, a case where SS-OCT is applied will be described. When SS-OCT is applied, the configuration of the OCT observation apparatus 6 is different from that of TD-OCT. In TD-OCT, drive control for changing the position of the reflector 73 is performed by the reflector controller 65, but in SS-OCT, it is not necessary to change the position of the reflector 73. Therefore, the position of the reflector 73 is fixed. This will be specifically described below.

  As shown in FIG. 2, in SS-OCT, the light source 71 is wavelength-swept by a light source wavelength controller 68. The light source 71 is composed of a tunable laser, and the light source wavelength controller 68 can change the wavelength (frequency) of the laser light at a constant period. The light emitted from the light source 71 that has been subjected to the wavelength sweep by the light source wavelength controller 68 is branched into the measurement light Ls and the reference light Lr in the light branching unit 72, and the measurement light Ls is connected to the probe 2. 82 is guided. Then, the reflected light from the subject enters the light branching portion 72 again as detection light. On the other hand, the reference light Lr is reflected by a reflector 73 configured by a reflecting mirror or the like, and enters the light branching unit 72 as reflected light. The detection light and the reflected light of the reference light Lr are combined in the optical branching unit 72, and the interference light of both lights is detected in the photodetector 74.

  Here, the detection light that is the reflected light of the measurement light Ls irradiated to the subject has an intensity component for each wavelength band (frequency band). Of the detected light, the intensity information of the long wavelength band (low frequency band) is reflection information from a deep position in the body of the subject, and the intensity information of the short wavelength band (high frequency band) is the body of the subject. It is reflection information from a shallow position. In the photodetector 74, since the interference light between the detection light and the reflected light of the reference light Lr is received, the intensity of the reflected light at each depth is detected based on the intensity information for each wavelength band (for each frequency band). It can be done. The FFT control unit 75 performs frequency analysis on the interference light detected by the photodetector 74 by FFT (Fast Fourier Transform) to determine an optical tomogram of the interference light. Then, distance information of each layer of the subject and information for each reflection layer are acquired, and optical tomographic information is acquired. Therefore, as the information output from the FFT control unit 75 to the A / D 61, one line of received signal (one line signal) which is optical tomographic information in a certain range at each depth position is acquired simultaneously. Such a one-line signal can be handled as a signal similar to the one-line signal from the ultrasonic transducer.

  In TD-OCT, the position of the reflector 73 is driven and controlled in order to acquire one line signal constituting an optical tomographic image. In SS-OCT, each wavelength band (frequency band) is detected light. Since the depth tomographic information is included, one line signal can be acquired simultaneously without driving and controlling the position of the reflector 73. Since it is not necessary to drive and control the reflector 73, the SS-OCT is not provided with the reflector controller 65.

  In SS-OCT, the light source wavelength controller 68 performs wavelength sweep on the light source 71 in order to acquire tomographic information at each depth for each wavelength band (frequency band). When acquiring tomographic information for only this range, wavelength sweeping is performed according to that range. For this reason, the scan controller 64 outputs the range information in the depth direction of the region of interest from the ROI controller 56 to the light source wavelength controller 68, and the light source wavelength controller 68 performs the wavelength sweep so as to acquire tomographic information of only the range. I do.

C. When SD-OCT is applied Next, a case where SD-OCT is applied will be described. Even when SD-OCT is applied, the configuration of the OCT observation apparatus 6 is different from that of TD-OCT. Even in the SD-OCT, since the position of the reflector 73 does not need to be changed, the position is fixed. This will be specifically described below.

  In SD-OCT, low-coherent light is used as light emitted from the light source 71. Therefore, as the light source 71, a light source that emits light with low coherence, such as SLD, is used as in TD-OCT. The low coherent light emitted from the light source 71 is branched into the measurement light Ls and the reference light Lr in the light branching unit 72, the measurement light Ls is directed to the subject, and the reference light Lr is directed to the reflector 73. The process up to the configuration in which the detection light and the reflected light of the reference light Lr are combined at the optical branching unit 72 is the same as that of TD-OCT. In SS-OCT, the interference light between the detection light and the reflected light of the reference light Lr is wavelength-resolved by the spectral spectrometer 76 and is channel-divided by the optical line detector 69 into each wavelength component (each frequency component). Is detected.

  That is, the interference light between the detection light and the reflected light of the reference light Lr is interference light having a plurality of wavelengths. If the interference light is separated into each frequency band (each wavelength band) in the spectrum spectrometer 76, each frequency is obtained. The intensity information of the band (each wavelength band) can be acquired. Since the intensity information of each frequency band (each wavelength band) corresponds to the tomographic information at each depth of the subject, if frequency analysis is performed by performing FFT on the spectral density information from the optical line detector 69. The tomographic information in a certain range in the depth direction of the subject can be acquired without changing the position of the reflector 73. That is, in the SD-OCT, it is not necessary to drive and control the position of the reflector 73, and tomographic information at each depth position of one line signal constituting the optical tomographic image can be acquired simultaneously. Therefore, the reflector controller 65 is not provided in the SD-OCT.

  In SD-OCT, a channeled spectrum wavelength-resolved by the spectroscope 76 is detected by the optical line detector 69 in order to acquire tomographic information at each depth for each wavelength band (frequency band). When acquiring tomographic information of only a partial range in the depth direction, the optical line detector 69 detects a channeled spectrum corresponding to the range. For this reason, the optical line detector 69 outputs the information on the range in the depth direction of the region of interest from the ROI controller 56 to the optical line detector 69 by the scan controller 64, and acquires the tomographic information of only the range. A channeled spectrum corresponding to the range is detected.

  The operation of the diagnostic imaging apparatus of the present invention having the above configuration will be described with reference to the flowchart of FIG. First, the operation when TD-OCT is applied will be described, and the operation when SS-OCT and SD-OCT are applied will be described later.

D. Operation of the present invention when the TD-OCT method is applied First, an ultrasonic tomographic image of the subject is generated in advance together with the rotation of the probe 2 and displayed on the monitor device 3 (step S1). Accordingly, the rotational speed of the probe 2 is a speed for acquiring an ultrasonic tomographic image, and the ultrasonic observation device 5 drives the ultrasonic transducer 81 at a predetermined timing according to the rotational speed of the probe 2 to receive the ultrasonic tomographic image. An ultrasonic tomographic image is generated from the received signal. Then, when the operator operates the input unit 4 while the ultrasonic tomographic image is displayed on the screen of the monitor device 3, the setting of the region of interest is started (step S2).

  First, a range for performing OCT scanning is set (step S3). In the example of FIG. 1, since the radial scanning is performed instead of the linear scanning, in order to specify the scanning range, the offset, the scanning angle (scanning range in the rotation direction), and the scanning depth (scanning range in the depth direction) are set. Must be set. For example, when setting a region of interest from the ultrasonic tomographic image shown in FIG. 6A, an offset S (starting point for setting a scanning range) is set, and a scanning angle θ and a scanning depth D are set. To do. By setting the above three elements, it is possible to specify the range in which the OCT scan is performed, but it is also possible to set the range to be displayed on the screen of the monitor device 3 (step S4). That is, when it is not necessary to display the entire range in which the OCT scan is performed, the optical tomographic image in a certain range can be set to be displayed.

  By the way, in the case of TD-OCT, since the OCT scanning and the ultrasonic scanning have a large difference in the speed of acquiring one line signal, the rotational speed of the probe 2 is also different. As described above, the frame rate is deteriorated. Therefore, in the present invention, control is performed so that the rotation is performed at the rotational speed of the OCT scanning within the region of interest and at the rotational speed of the ultrasonic scanning outside the region of interest. That is, the probe 2 that has been rotated outside the region of interest at the rotational speed of the ultrasonic scanning is controlled so as to rotate at the rotational speed of the OCT scan by decreasing the rotational speed when entering the region of interest. For this reason, a configuration in which the rotational speed of the probe 2 is variable is adopted.

  Here, if the light irradiation means 82 enters the region of interest and at the same time the rotational speed of the probe 2 is drastically reduced, rotation unevenness may occur. Similarly, even if the rotational speed of the probe 2 is suddenly increased at the same time as the exit from the region of interest, there is a risk that uneven rotation will occur. For this reason, the rotational speed of the motor 101 is controlled so that the rotational speed is gradually decreased immediately before the light irradiation means 82 enters the region of interest, and the rotational speed is increased stepwise immediately before leaving the region of interest.

  Next, the sampling speed is set by the input means 4 (step S5). For example, when the region of interest is enlarged and displayed, it is necessary to perform OCT scanning with higher resolution. Therefore, it is necessary to set the sampling rate in order to perform sampling according to the desired resolution.

  Various settings are completed as described above. All the set contents are output to the ROI controller 56. The ROI controller 56 outputs the offset and operation angle information of the set contents to the motor 101, and the offset, operation angle, scanning depth and sampling speed information to the scan controller 64. Output.

  According to the information from the ROI controller 56, the motor 101 rotates at the rotational speed so that the probe 2 is rotated at the rotational speed of the OCT scan within the range of the scanning angle for performing the OCT scan and at the rotational speed of the ultrasonic scan in the other. Control is performed (step S6). At this time, the motor 101 performs control so as to gradually decrease the rotation speed when entering the range where OCT scanning is performed. As the motor 101 rotates, the rotating shaft 104 connected to the driving unit 102 rotates, and each rotating member of the probe 2 connected to the rotating shaft 104 rotates. Thereby, the rotation speed of the probe 2 is controlled.

  Although the rotation direction is controlled as described above, in the TD-OCT OCT scanning, it is necessary to drive and control the reflector 73 corresponding to the scanning depth. Therefore, the scan controller 64 transmits the information on the scanning depth output from the ROI controller 56 to the reflector controller 65, and the reflector controller 65 moves the reflector 73 by an amount corresponding to the scanning depth according to the information (step S7). ).

  Since the optical path length on the reference light side also changes as the position of the reflector 73 changes, information at a depth corresponding to the optical path length is acquired. Therefore, if the position of the reflector 73 is moved by the scanning range in the depth direction, the tomographic information at each depth can be acquired, and they can be combined into one line signal. Since the scan controller 54 controls the signal capture by the scan controller 64, the signal is captured by the scan converter 63 accordingly. Then, along with the rotation of the probe 2, the next one-line signal is formed. Based on the control from the scan controller 64, the scan converter 63 generates an optical tomographic image within the target range (within the region of interest). The optical tomographic image is converted into an analog signal by the D / A 66, and then output to the monitor device 3 to be displayed on the screen as shown in FIG. 6B (step S8).

  Then, control is performed so that the rotational speed is increased stepwise when exiting from the OCT scanning range. Thereafter, ultrasonic scanning is performed, and when entering the OCT scanning region, the rotational speed is decreased stepwise and matched to the rotational speed of the OCT scan. As a result, the rotation speed of the probe 2 can be set to a speed corresponding to the OCT scan only in the region of interest, and the other areas can be set to a speed corresponding to the ultrasonic scan. Accordingly, since it is not necessary to set the omnidirectional speed corresponding to the OCT scanning, it is possible to suppress a decrease in the frame rate.

E. Operation of the present invention when the SS-OCT method and the SD-OCT method are applied Next, the operation when the SS-OCT and SD-OCT are applied will be described. As described above, since SS-OCT and SD-OCT do not need to drive and control the position of the reflector 73, it is not necessary to reduce the rotation speed of the probe 2. Therefore, the probe rotation speed control in step S6 and the reflector drive control in step S7 are not required when SS-OCT and SD-OCT are applied. Other steps are the same as in TD-OCT.

  In SS-OCT and SD-OCT, the scan converter 63 captures one line signal from the line memory 62 as needed under the control of the scan controller 64. The scan converter 63 converts the captured signal in the scanning direction and records the converted signal for one frame. At this time, the scan converter 63 acquires the setting information of the region of interest from the ROI controller 56 via the scan controller 64. Then, the scan converter 63 applies a predetermined signal only to the region of interest among the signals for one frame stored in itself, and generates an optical tomographic image of only the region of interest. The optical tomographic image generated by the scan converter 63 is converted from a digital signal to an analog signal by the D / A 66 and displayed on the screen of the monitor device 3.

  As described above, even when any of the TD-OCT, SS-OCT, and SD-OCT methods is used, an ultrasonic tomographic image and a partial range set from the ultrasonic tomographic image are used. An optical tomographic image of only the region of interest is displayed simultaneously.

  Since the optical tomographic image is an image generated by performing OCT scanning with a very high resolution, it has a very large amount of information. Therefore, when the same monitor device is used and the display area is divided into two, and the ultrasonic tomographic image and the optical tomographic image are displayed on the same scale, the optical tomographic image of the entire range of the ultrasonic tomographic image is displayed. Therefore, the optical tomographic image is displayed after being subjected to a reduction process such as a thinning process and cannot be displayed at a high resolution. Further, if the ultrasonic tomographic image and the entire range of the optical tomographic image are displayed on different monitoring devices instead of the same monitoring device, both images are suppressed while suppressing the reduction rate of the reduction processing applied to the optical tomographic image to some extent. Can be displayed. However, since there is a very large difference between the information amount of the ultrasonic tomographic image and the information amount of the optical tomographic image of the entire range, the resolution of the monitor device that displays the ultrasonic tomographic image and the monitor that displays the optical tomographic image Even if the resolution of the apparatus is changed, the optical tomographic image in the entire range needs to be reduced with a high reduction ratio. Therefore, the optical tomographic image cannot be displayed with high resolution.

  In the present invention, an optical tomographic image of only a region of interest in a part of the range is generated instead of the entire range of the ultrasonic tomographic image. Therefore, the amount of information of the optical tomographic image of the region of interest can be reduced compared with the optical tomographic image of the entire range. For this reason, even if an ultrasonic tomographic image and an optical tomographic image having a large amount of information are displayed at the same time, the reduction ratio can be made extremely small even if the reduction process is not performed or the reduction process is performed. Optical tomographic images can also be displayed with high resolution.

  In general, the ratio of the region of interest displayed in the optical tomographic image occupies only a small portion and is not so large. Therefore, if only an optical tomographic image of a very small region of interest is displayed, a high-resolution optical tomographic image of the region of interest and the entire ultrasonic tomographic image can be displayed simultaneously.

  In addition, since the optical tomographic image only needs to be subjected to signal processing only in the region of interest, there is no problem that the signal processing takes a very long time.

  By the way, since the optical tomographic image is composed of only a part of the ultrasonic tomographic image, only the optical tomographic image is used to determine which part of the ultrasonic tomographic image the optical tomographic image indicates. It may be difficult to grasp at a glance. As described above, the optical tomographic image is a partial region of interest in the ultrasonic tomographic image, and the proportion of the region of interest in the entire region is not so large. The smaller the ratio of the region of interest to the entire region, the more difficult it is to grasp which part of the optical tomographic image of the region of interest is displayed in the entire region.

  Therefore, when the region of interest is set from the ultrasonic tomographic image in step S4, the set region of interest is not hidden after setting, but the region of interest is included in the ultrasonic tomographic image. The display is made so that it is clearly distinguished from other areas. In FIG. 6, the range of the region of interest surrounded by a solid line is illustrated. However, the present invention is not limited to this, and any region can be used as long as the region of interest and other regions can be clearly distinguished. This makes it possible to clearly display the region of interest in the ultrasonic tomographic image, and to easily grasp the range of the ultrasonic tomographic image corresponding to the region of interest. Become. When a new optical tomographic image of a region of interest different from the displayed region of interest is to be displayed, the previously displayed region of interest is hidden and the newly set region of interest is displayed. Display the area so that it can be clearly distinguished from other areas.

  When the TD-OCT method is applied, since the rotational speed of the probe can be used for OCT scanning only in the region of interest and the other regions can be used for ultrasonic scanning, the frame rate of the ultrasonic tomographic image. Can be prevented from decreasing.

  As described above, in the present invention, the optical tomographic image displayed simultaneously with the ultrasonic tomographic image is an image of only a part of the region of interest, not the entire range of the ultrasonic tomographic image. Can be reduced. Therefore, the ultrasonic tomographic image and the high-resolution optical tomographic image can be displayed at the same time, and the problem that it takes a long time to perform signal processing on the optical tomographic image can be solved. In addition, when displaying, the displayed ultrasonic tomographic image is displayed so that the set region of interest can be clearly distinguished from other regions. It is possible to grasp at a glance which part is displayed in the sonic tomographic image.

  In the case of TD-OCT, since the rotation speed of the probe is used for OCT scanning only in the region of interest and the other regions are used for ultrasonic scanning, the frame rate does not decrease.

  In the above-described embodiment, the example in which radial scanning is performed has been described as an example. However, the present invention can be applied to that in which linear scanning is performed.

It is a schematic block diagram of the signal processing apparatus of this invention by a TD-OCT system. It is a schematic block diagram of the signal processing apparatus of this invention by SS-OCT system. It is a schematic block diagram of the signal processing apparatus of this invention by SD-OCT system. It is a schematic block diagram of a probe. It is a flowchart which shows the flow of a process. It is a figure which shows an example of an ultrasonic tomographic image and an optical tomographic image.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Signal processing apparatus 2 Probe 3 Monitor apparatus 5 Ultrasonic observation apparatus 6 OCT observation apparatus 7 OCT control part

Claims (5)

An ultrasonic transducer that ultrasonically scans a predetermined range of a subject at the tip of a probe having a flexible tube, and a light irradiation unit that irradiates the subject with measurement light from a light source and receives the reflected light And integrally formed,
Ultrasonic image generation means for generating an ultrasonic image based on a reflected echo received by the ultrasonic transducer, reflected light of reference light branched from a light source for deriving the measurement light to a subject, and the target Optical tomographic image generation means for generating an optical tomographic image by performing optical scanning of the subject using interference with reflected light from the sample,
A region of interest in a part of the ultrasonic image generated by the ultrasonic image generation unit is set, and the ultrasonic image and an optical tomographic image of only the set region of interest are simultaneously displayed on the screen. An image diagnostic apparatus characterized by:   The image diagnosis apparatus according to claim 1, wherein the ultrasonic image is displayed so that a set range of the region of interest and a range of other regions can be clearly distinguished.   A rotating block that is driven to rotate by a rotatable flexible shaft is provided in the probe, and the ultrasonic transducer is provided in the rotating block, and is scanned in a direction perpendicular to the rotation axis, and the light irradiation means 2. The diagnostic imaging according to claim 1, wherein an optical fiber and a prism that bends the optical path so that the light emitted from the optical fiber substantially coincides with the scanning direction of the ultrasonic transducer are provided in the rotating block. apparatus.   2. The diagnostic imaging apparatus according to claim 1, wherein the measurement light from the light source uses low-coherence measurement light, and the optical tomographic image generation means performs optical scanning only on the set region of interest. . 5. The image according to claim 4, wherein the rotation speed of the probe is gradually reduced immediately before the probe enters the region of interest in the rotation direction and is accelerated stepwise immediately after leaving the region of interest. Diagnostic device.

Images