JP4068098B2 - Blood flow measuring device - Google Patents

Description

  The present invention relates to analysis processing of image data taken in the medical field.

  Conventionally, in the medical field, a lot of image data has been used for diagnosis and research. For example, X-ray CT (Computed Tomography) and MRI (Magnetic Resonance Imaging) are often used in the diagnosis of stroke. Both of these can take a tomographic image of the brain. And blood flow can be grasped | ascertained by performing image processing about the image image | photographed using these, and many analysis methods of this image have been reported (for example, nonpatent literature 1).

  One of the analysis methods is a deconvolution method. For example, a certain change occurs in an artery, and the change appears in the vein. At this time, the change appears in the vein through various decorations. The deconvolution method examines what is happening in the capillaries. Many of the deconvolution methods are calculated by Fourier transform or Laplace transform. There is also this simple method (for example, Non-Patent Document 2).

Another analysis method is trigonometry (Trapez). The trigonometric method is a method of calculating whether or not there is more blood flow than the magnitude of the value divided by the height of the triangle, taking the three points of the peak part of the obtained dye dilution curve and the flat part at both ends. is there.
ISTVAN SCHISZLER, MINORU TOMITA, YASUO FUKUCHI, NORIO TANAHASHI, AND KOJI INOUE "New optical method for analyzing cortical blood flow heterogeneity in small animals: validation of the method", (US), Am J Physiol Heart Circ 279, 2000 years, H1291 -H1298 Satoshi Hamada, “Indicator transit time distribution function in organs—a simple method of devolution”, Ayumi Medicine, Ishigaku Shuppan Co., Ltd., 1973, 84, p. 137-p. 138 Am J Physiol 235, H56-H63, 1978 Am J Physiol 245, H385-H398, 1983 Am J Physiol 279, H1291-H1298, 2000

  However, in the above conventional method, in order to obtain an image of an ischemic portion (a portion where arterial blood flowing locally decreases and a blood supply necessary for tissue is insufficient), a complicated calculation based on enormous information is performed. Had gone. The time until the result is obtained depends on the performance of hardware such as the processing speed of the computer. Also, such computers were expensive and not found in any medical institution.

  In view of the above problems, the present invention provides a cerebral blood flow measurement device that measures blood flow in a living body in a shorter time and a program thereof.

According to the present invention, there is provided a blood flow measurement device for measuring a blood flow volume in a predetermined region of a biological tissue of a specimen into which carbon black or physiological saline is injected as a contrast agent. Acquisition of frame image data of 20 frames at a sampling rate of 1/10 second from a plurality of image data of the predetermined area that are taken in time series under a reflected light at a frame rate of 30 frames / second Means, a frame image dividing means for dividing each acquired frame image into a plurality of sections, and a partition luminance value for calculating a change in the brightness value for each section over time based on the plurality of frame image data The first moment, the deconvolution, based on the dye dilution curve which is the result calculated by the transition calculation means and the section luminance value transition calculation means. Or means for calculating the average passage time of the contrast agent for each of the sections, and a blood flow amount calculation means for calculating the reciprocal of the average passage time to obtain the blood flow volume Display means for converting the calculated blood flow rate into a luminance value, displaying it as an image, and displaying it.

With this configuration, Ru can be easily calculated blood flow in a predetermined region of the living tissue.

In addition, by this configuration, easily observe the blood flow, ing so as to obtain a clean dye dilution curve.

Further, by such a configuration, Ru can be used either irradiation method according to the condition of the state and the surrounding of the sample.

In addition, with this configuration, it is possible to simplify the calculation of blood flow.
A blood flow measurement program according to the present invention for causing a computer to execute a process for measuring blood flow in a predetermined region of a biological tissue of a specimen into which carbon black or physiological saline is injected as a contrast agent is stored in a mass storage device. Frames of 20 frames at a sampling rate of 1/10 second from a plurality of image data of the predetermined area consecutively taken in time series captured at a frame rate of 30 frames / second under transmitted light or reflected light An acquisition process for acquiring image data, a frame image division process for dividing each acquired frame image into a plurality of sections, and a change in luminance value for each section over time based on the plurality of frame image data Based on the pigment dilution curve that is the result of the calculation of the block luminance value transition calculation process and the block luminance value transition calculation process. An average transit time calculation process for calculating an average transit time of the contrast agent for each of the sections using a first-order moment, deconvolution, or trigonometry, and a reciprocal of the average transit time to calculate the blood The computer executes the blood flow rate calculation process for the flow rate.

With this configuration, Ru can be easily calculated blood flow in a predetermined region of the living tissue.

In addition, by this configuration, easily observe the blood flow, ing so as to obtain a clean dye dilution curve.

Further, by such a configuration, Ru can be used either irradiation method according to the condition of the state and the surrounding of the sample.

In addition, with this configuration, it is possible to simplify the calculation of blood flow.

  By using the present invention, blood flow in a living body can be measured in a shorter time than in the prior art.

  The present invention divides a frame image into a plurality of sections and calculates a blood flow rate in each section from a dye dilution curve represented by a change in luminance value of the section over time.

  For example, when photographing an image of the brain surface of a specimen into which a dye has been injected, the flow starts from photographing → injection of dye → photographing ends. At this time, for example, in the case of a cat or rat brain, about 100 seconds are taken in order to obtain a sampling rate of approximately 1/10 intervals. Since filming is continuously performed with video, the timing of taking an image is about 1 second before dye injection. Then, from the image photographed in this way, a dye dilution curve such as a rising, rising curve, a peak, a falling curve, and a baseline return is obtained.

The dye dilution curve rises from about 0.5 seconds after the dye is injected, and peaks at about 1 second.
Now, an embodiment according to the present invention will be described below.

  FIG. 1 shows an image analysis apparatus 1 according to this embodiment. In FIG. 1, the image analysis apparatus 1 includes at least a mass storage device 2, a memory 3, an output interface 5, an input interface 8, a CPU (central processing unit) 10, and a bus 4 for connecting them. A display device 6 and the like are connected to the output interface 5, and an imaging device 7 and an input device 9 and the like are connected to the input interface 8. The image analysis apparatus 1 may be a normal personal computer.

  As an example of the large-capacity storage device 2, various types of storage devices such as a hard disk and a magnetic disk can be used, and a flow program and the like to be described later are stored. This program is read by the CPU 10, and each process of the flow is executed.

  The memory 3 is a storage device such as a RAM (Random Access Memory) and a ROM (Read Only Memory) used in various processes. The display device 6 is a display or the like.

  The input device 9 includes a keyboard, mouse, or electronic camera, microphone, scanner, tablet, storage medium (flexible disk, CD, CD-ROM, CD-R, DVD, DVD-R, DVD-ROM, memory card). Etc.) can be used. In addition, other peripheral devices can be connected.

  The imaging device 7 is, for example, a digital video camera or a video scope. The digital image stored in the large-capacity storage device 2 may be stored via the communication network from the imaging device 7, or the digital image stored in a storage medium or the like may be read out and stored by the reading device. Good.

  FIG. 2 shows the overall flow in this embodiment. First, the operator opens a hole (head window) in a part of the skull of a rat or mouse (hereinafter referred to as a specimen) using the cranial window method, and the object to be observed in the brain surface viewed through the head window. (Region of interest (ROI: Region Of Interest)) is determined (step 1, hereinafter, step is referred to as “S”).

  Next, a light source for irradiating the ROI with light and an imaging device 7 for photographing the ROI are installed. Here, there are two patterns of light irradiation methods: an irradiation method as reflected light and an irradiation method as transmitted light. Reflected light is light that is emitted from a light source that is distant from the brain tissue, and the irradiated light is reflected on the surface of the brain tissue. On the other hand, the transmitted light is light that is irradiated with light in a state where the light source is in contact with the brain tissue or in the vicinity of the brain tissue, and the light passes through the body tissue and goes out of the body tissue.

  Although there are photographing methods based on these two patterns of irradiation methods, the light used is preferably transmitted light. This is because when a body tissue to be imaged is photographed using reflected light, light is irradiated only to a thin layer near the surface of the body tissue, so there is little information obtained from the reflected light, and the body tissue Although it is only information near the surface, when a body tissue to be imaged is photographed using transmitted light, the light passing through the body tissue contains information in the body tissue and the amount of information is larger than the reflected light Because.

  The specific method for obtaining the transmitted light of the body tissue as described above has the following research report by the present inventor. In order to obtain the transmitted light of the brain tissue, when a micro lamp with a diameter of 1 mm is inserted into the brain tissue and fixed at about 1 mm from the surface of the brain, the brain tissue around the micro lamp appears to be stained red (non-patented). Document 3, Non-Patent Document 4), and a glass fiber having a diameter of about 200 microns is used in the same manner as described above (Non-Patent Document 5).

  After the light irradiation, imaging of the ROI is started by the imaging device 7 (S2). In the present embodiment, the ROI imaged by the imaging apparatus is an area of 3 mm × 3 mm. Here, the shooting speed was 30 frames / second.

  Next, physiological saline or carbon black is injected into the internal carotid artery of the specimen while photographing with the imaging device (S3). Physiological saline or carbon black serves as a kind of contrast agent. In this embodiment, physiological saline or carbon black is used. However, the present invention is not limited thereto, and any material can be used as long as it can be used as a contrast medium.

  After the predetermined time elapses, the photographing by the imaging device 7 is ended (S4). The image data captured between S2 and S5 is transmitted to the image analysis device 1 and stored in the mass storage device 2. Next, image analysis of the image data is performed (S5). Details of the processing of S5 will be described with reference to FIG.

  FIG. 3 shows a flow of measuring blood flow by image analysis in the present embodiment. This figure is a program (a program incorporated in a general-purpose numerical analysis program MATLAB (registered trademark)) executed by the CPU 10 of the image analysis apparatus 1.

  First, the CPU 10 reads a program for executing this flow stored in the memory 3 and activates this program. Next, the CPU 10 reads out image data (a group of consecutive frame images) stored in the large-capacity storage device 2 for a predetermined number (S11).

  Here, for example, 20 frames are read out from the captured frame image group at a sampling rate of 1/10 [second]. It should be noted that 20 frames are sufficient to draw the dye dilution curve neatly.

  Next, the frame image read in S11 is divided into a plurality of sections (S12). That is, the frame image is divided into vertical m × horizontal n to form a matrix. This will be described with reference to FIG. Note that m and n are positive numbers.

  FIG. 4 shows an example when the frame image in this embodiment is divided into m × n. In the present embodiment, as shown in the figure, the frame image is divided into 50 × 50 matrix. In this case, there are 50 vertical sections × 50 horizontal sections = 2500 sections. As described above, the frame image is an image of an ROI having a scale of 3 mm × 3 mm. In this embodiment, the frame image is divided into 50 × 50. However, the present invention is not limited to this, and m × n is arbitrary. Returning to the description of FIG.

  Next, the brightness value of each section is calculated (S12). One section is a set of one or more pixels. Therefore, the luminance value of the section can be, for example, an average value of pixels existing in the section. Therefore, in this embodiment, luminance values for 2500 sections are calculated.

  In this way, the processing for the first frame image is completed, and if there is a next frame image, the processing returns to S12 and the processing of S12 and S13 is performed for that image (S14). In this way, the processing of S12-S13 is repeated for each frame image read in S11.

  Next, a dye dilution curve is calculated (S15). The dye dilution curve indicates a change in the concentration (abundance) of the dye in the brain (in this embodiment, physiological saline or carbon black injected in S3). In the present embodiment, the luminance blood calculated in S13 is handled as a concentration. Now, a method for calculating a dye dilution curve will be described with reference to FIG.

  FIG. 5 shows an example of a dye dilution curve for each section in the present embodiment. The vertical axis represents a value corresponding to the concentration (luminance value) of the dye, and the horizontal axis represents time (seconds). By arranging the luminance values for each section in time series, a dye dilution curve as shown in the figure can be drawn for each section. Returning to the description of FIG.

  Next, the mean transit time (MTT) of the blood in each compartment is calculated (S16). When carbon black is injected in S3, the MTT of the carbon black can be regarded as blood MTT. In addition, when physiological saline is injected, blood is diluted by the physiological saline and flows through the blood vessels, so that it can be regarded as a flow of blood erythrocytes. Therefore, this physiological saline MTT can be regarded as blood MTT.

  The MTT is, for example, a dye dilution calculated in S15 using a commonly used method such as first-order moment (statistical method), deconvolution method, or trigonometry (Trapez). Calculated from the curve. The MTT is obtained for each section by any one of these methods.

  Based on the MTT calculated for each section (that is, each dye dilution curve) in this way, the cerebral blood flow for each section (that is, each dye dilution curve) is calculated (S17). The flow rate of the contrast medium in the tissue, that is, cerebral blood flow (CBF) is generally calculated from the following equation (1).

Cerebral blood flow = CBV / MTT (1)
(CBV: blood content (cerebral blood volume))
Here, since the cerebral blood flow to be calculated is a relative value, when CBV≈1, Equation (1) is
Cerebral blood flow = 1 / MTT (2)
It can be expressed as. From this equation (2), the cerebral blood flow volume for each section (that is, each dye dilution curve) is calculated. The cerebral blood flow calculated in this way can be displayed on the display 6 in various forms, as will be described below.

  FIG. 6 is an example of the blood flow calculated for each section arranged in a matrix so as to correspond to the position of the section. Thereby, it can be recognized as a numerical value whether there is much cerebral blood flow in this position (section).

  FIG. 7 is an image obtained by relatively replacing the blood flow value in FIG. 6 with a luminance value. In the figure, it is shown that the blood flow increases as it becomes white (high brightness value), and the blood flow decreases as it becomes black (low brightness value). FIG. 8 is a microphotograph of the same region as the above ROI. By referring to FIG. 7 and FIG. 8, it can be confirmed which part of the blood flow is large.

  As described above, according to the present embodiment, blood flow in the brain can be measured more easily and in a shorter time than in the past. Therefore, in order to diagnose stroke, it is not necessary to perform a complicated calculation as in the prior art, and a result similar to the result obtained by such a calculation can be obtained easily and quickly. Further, the present invention can be executed even in an environment such as a general personal computer without using an expensive apparatus. In the present embodiment, the blood flow in the brain has been described. However, the present invention is not limited to this, and the present invention can also be applied to blood flow in any organ.

1 shows an image analysis apparatus according to the present embodiment. The whole flow in this embodiment is shown. The flow which measures a blood flow by the image analysis in this embodiment is shown. An example when the frame image in this embodiment is divided into m × n is shown. An example of the dye dilution curve for every division in this embodiment is shown. It is an example in which blood flows calculated for each section are arranged in a matrix so as to correspond to the position of the section. It is the figure which replaced the value of the blood flow of FIG. 6 with the luminance value, and imaged it. It is the microphotograph which image | photographed ROI.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Image analysis device 2 Mass storage device 3 Memory 4 Bus 5 Output interface 6 Display 7 Imaging device 8 Input interface 9 Input device

Claims (2)

In a blood flow measurement device for measuring blood flow in a predetermined region of a biological tissue of a specimen into which carbon black or physiological saline is injected as a contrast agent,
Sampling of 1/10 second from image data of a plurality of the predetermined regions that are stored in the large-capacity storage device and taken in time series under transmitted light or reflected light at a frame rate of 30 frames / second Acquisition means for acquiring frame image data of 20 frames at a rate ;
Frame image dividing means for dividing each acquired frame image into a plurality of sections;
Based on the plurality of frame image data, a section luminance value transition calculating unit that calculates a change in the luminance value for each section over time,
Based on the dye dilution curve that is the result calculated by the section luminance value transition calculating means, the average transit time of the contrast agent is calculated for each section using first-order moment, deconvolution, or trigonometry. Means for calculating average transit time,
And blood flow rate it is calculating means and the blood flow rate by calculating the reciprocal of the mean transit time,
Display means for converting the calculated blood flow volume into a luminance value, displaying it as an image, and
A blood flow measuring device comprising: In a blood flow measurement program for causing a computer to execute a process of measuring a blood flow in a predetermined region of a biological tissue of a specimen into which carbon black or physiological saline is injected as a contrast agent,
Sampling of 1/10 second from image data of a plurality of the predetermined regions that are stored in the large-capacity storage device and taken in time series under transmitted light or reflected light at a frame rate of 30 frames / second An acquisition process for acquiring frame image data of 20 frames at a rate ;
A frame image dividing process of dividing each acquired frame image into a plurality of sections;
Based on the plurality of frame image data, a section luminance value transition calculation process for calculating a change in luminance value for each section over time,
Based on the dye dilution curve that is the result calculated by the section luminance value transition calculation process, the average transit time of the contrast agent is calculated for each section using first-order moment, deconvolution, or trigonometry. An average transit time calculation process,
A blood flow calculation process for calculating a reciprocal of the average transit time to obtain the blood flow ;
Is a blood flow measurement program that causes a computer to execute.