JP2005177212A - Radiographic image processing device, radiographic image processing system, radiographic system, radiographic device, radiographic image processing method, computer-readable storage medium and program - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a cone-beam CT apparatus for detecting the strength of inspiration to be used as the human body fixing strength in rotating the human body, capable of solving the following problems; that a patient can not easily respire if the fixing strength of a belt wound across the thoracic region is increased to reduce the body movement in photographing the thoracic region when the patient is fixed to a top plate with the belt, etc. to reduce the body movement of the patient or to prevent the patient from falling from the top plate in a human body rotating type CT apparatus, and that it is difficult to adjust the strength of an air-bag when the air-bag is used instead of fixing the patient locally with the belt. <P>SOLUTION: The apparatus consists of a top plate means for fixing a subject, a fixing belt means to be connected to the top plate, an inspiration strength detecting means for measuring the strength of inspiration of the subject applied to the fixing belt, and a photography control means. The photography control means permits the photography when the strength of inspiration is larger than a reference value. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a radiation imaging apparatus that images radiation characteristic distribution in a subject using radiation in general, such as an X-ray CT apparatus that performs image capturing using radiation such as X-rays. In particular, the cone beam CT apparatus is characterized in that when the human body is rotated, the intake air intensity is detected to obtain a human body fixing intensity.

  Conventionally, X-rays are exposed to a subject, X-rays transmitted through the subject or scattered by the subject are detected by an X-ray detector, and based on this X-ray detection output (number of photons of X-rays) An X-ray CT apparatus that captures a fluoroscopic image, a tomographic image, or a three-dimensional image of a subject is known. As such an X-ray CT apparatus, a cone beam CT apparatus has been developed. In a normal X-ray CT apparatus, the X-ray beam is cut out thinly in the Z direction, which is called a fan beam, but cone beam CT (CBCT) uses an X-ray beam that also spreads in the Z direction. The beam is called a cone beam.

  By the way, during X-ray CT scanning (during data acquisition), it is premised that the subject is completely fixed, and body motion or organ motion during scanning causes a false image in the reconstructed image, The diagnostic ability is reduced. Therefore, various techniques for fixing the patient are disclosed.

For example, in a top plate that supports the subject in order to perform a medical act on the subject, cross sections formed along the longitudinal direction on both edges of the subject support surface of the top plate are T-shaped. A subject-supporting top board comprising: a guide having a shape; and a variable-length band having hooks detachably and slidably engaged with the guide at both ends. (For example, see Patent Document 1)
According to another disclosed example, the top mat on which the subject is placed and disposed on the top of the medical bed includes an auxiliary member that can be expanded according to the size of the subject. Medical sleeper mat. (For example, see Patent Document 2)
According to another disclosed example, a support that rotatably supports the subject, an X-ray source that irradiates the subject on the support with X-rays, and the X across the subject. An X-ray image provided with an X-ray detector arranged to face the radiation source and detecting the transmitted X-rays of the subject, and means for acquiring an X-ray image from the transmitted X-rays detected by the X-ray detector In the diagnostic apparatus, when the X-ray image is acquired by the X-ray image acquisition means, the support is inflated by injecting fluid so as to support the subject in close contact with the body surface of the subject An X-ray diagnostic imaging apparatus comprising: a body; and means for controlling injection or discharge of fluid into the expansion body. (For example, see Patent Document 3)
According to another disclosed example, a band set for fixing an examinee to a top plate of an X-ray diagnostic apparatus, the first band being wound around the top plate and fixed to the top plate; The first band is stitched slightly inward from the side of the top side of the top band of the first band, the second band is formed with a crimp-type fastener at the other end, and one end is the first band. And at least one third band which is sewn in the vicinity of the side of the back side of one band and wraps and fixes the subject. (For example, see Patent Document 4)
Prior art documents related to the invention of this application include the following.
Japanese Patent Publication No. 05-005499 (Claims) JP 2003-210457 A (Claims) JP 2000-070260 A (Claims) JP 06-217972 A (Claims)

  In the human body rotation type CT, the patient is fixed to the top board with a belt or the like in order to reduce the patient's body movement or prevent the patient from falling. However, in order to reduce body movement in chest imaging, there is a problem that breathing becomes difficult if the fixing force of the belt passed to the chest is increased. An air bag or the like is considered instead of locally fixing with a belt, but it is difficult to adjust the strength of the air bag.

  Therefore, in a normal state, the fixing belt is adjusted so that pressure is not applied to the chest, and when the subject shifts to the inhalation state, a force for lifting the ribs is used to obtain a human body fixing force. Then, the fixing force is detected and compared with a reference value to determine whether a sufficient fixing force can be obtained. If sufficient, photographing can be performed, and if not sufficient, the fixing belt is strengthened.

  According to the invention of claim 1, a top plate means for fixing a subject, a fixed belt means connected to the top plate, an intake air intensity detecting means for measuring the intake air intensity of the subject added to the fixed belt, The photographing control means is characterized in that the photographing control means is brought into a photographing enabled state when the intake air intensity is larger than a reference value. According to a second aspect of the present invention, in the first aspect of the present invention, the intake air intensity detection is calculated by detecting a tensile strength of a connecting portion between the top plate and the fixed belt. According to a third aspect of the present invention, in the first aspect of the present invention, the intake air intensity detection is calculated by detecting a tensile strength of a connecting portion between the fixed belts.

  As described above, according to the present invention, there is no fixing strength when the belt is fixed, and by detecting the respiratory strength of the subject and determining whether or not photographing is possible, the belt is fixed with a fixing strength inappropriate for patient breathing. Fixing can be avoided.

  A preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings (FIGS. 1 to 6).

  FIG. 1 is a conceptual diagram for explaining the overall image of the present invention. The upper part of FIG. 1 is Example 1, but the subject 5 is fixed to the top plate 3 by the fixing belt 4. The subject in this state is not in the maximum inspiration state but in the natural breathing state. In this state, the intake air intensity detection unit 1 does not satisfy the intake intensity that can be photographed. When the subject performs conscious maximum inspiration from this state, the rib rises, the cross-sectional area of the chest increases, and the force that extends to the fixed belt 4 acts to cause the respiratory intensity detection unit 1 to exceed the photographic inspiratory intensity. When CT data is collected in this state, the patient is appropriately fixed to the top board, and the body movement during data collection can be reduced. In the first embodiment shown in FIG. 1, the intake intensity detecting unit 1 is provided at the connecting portion between the fixed belt 4 and the top plate 3, whereas in the second embodiment shown in the middle of FIG. The intake air intensity detecting unit 2 is attached to the joint portion of the fixed belt. In the third embodiment shown in the lower part of FIG. 1, the intake air intensity detecting unit 6 is attached to the belt portion instead of the fixed belt coupling portion. A tension sensor or a strain gauge can be used as the intake air intensity detection unit. Examples of the tension sensor include an EM sensor using a coil and a thermometer, and a force displacement sensor that measures the contraction force of the heart muscle.

  FIG. 2 is a configuration example of the embodiment. X-rays emitted from the X-ray focal point 11 pass through the human body 16 and then pass through the breastplate 13 and the scattered radiation removal grid (not shown) and then reach the two-dimensional detector 12. The two-dimensional detector 12 is composed of a semiconductor sensor, and one pixel is 250 × 250 μm and the sensor outer shape is 43 × 43 cm. The number of pixels is 1720 × 1720 pixels. Data acquired by the two-dimensional detector 12 is transferred to the reconstruction unit 14 for image reconstruction. The fan angle φ and cone angle are determined by the geometric arrangement of the X-ray focal point 11 and the two-dimensional detector 12. In this embodiment, since a square two-dimensional detector is used, the fan angle and the cone angle are the same.

  FIG. 3 shows a system block diagram of the first embodiment. The entire system is composed of one computer system. The BUS 24 can be considered as an internal bus of the computer, and control signals and data are transmitted and received via the BUS. The control means 18 is a computer CPU. An instruction to start photographing is issued via the interface means 21. When a shooting instruction is given, the intake air intensity detecting means 17 detects the intake air intensity of the subject. If the intake air intensity is appropriate for the start of photographing, a completion of preparation for photographing is displayed on the interface means 21 (not shown). When an instruction to start photographing is issued, the rotary table 15 to which the human body 16 is fixed starts rotating according to an instruction from the control means 18.

  The control means 18 monitors an encoder signal (not shown) generated from the rotary table 15 and confirms whether a predetermined constant speed and angle have been reached. When a predetermined constant speed and angle are reached, a signal is sent to the X-ray generation means 11 to start X-ray exposure. The encoder signal is also used to determine the data integration timing.

  If an encoder that generates 25000 pulses per rotation of the table is used and if 1000 views of projection data are collected per rotation, data is collected from the two-dimensional detector 12 every 25 pulses of the encoder signal. become. The control means 18 counts the encode pulses, generates an integrated signal every 25 pulses, and counts the X-ray dose reaching the two-dimensional detector 12. In the present embodiment, it is assumed that X-rays are continuously generated, but the present invention is not limited to this. X-rays may be generated. Data from the two-dimensional detector 12 is sequentially transferred to the reconstruction unit 14 via the BUS 24. Data transfer continues until the turntable 15 rotates a predetermined rotation angle and a predetermined number of views are collected. The last projection data is collected immediately after the X-ray exposure is completed. The collected projection data is reconstructed into 3D voxel data by the reconstruction means 14.

  The reconstruction unit 14 includes preprocessing, filter processing, and back projection processing. The preprocessing includes offset processing, LOG conversion, gain correction, and defect correction. In the filter processing, a Ramachandran function or a Shepp Logan function is generally used, and these are also used in this embodiment. The filtered data is backprojected. The algorithm from the filtering process to the back projection uses the Feldkamp algorithm. When the back projection is completed and the CT cross-sectional image is reconstructed, the cross-section is displayed on the image display means 19.

  Here, although the Feldkamp algorithm is used as the reconstruction algorithm, the reconstruction algorithm is not limited to this. References include the method described by Feldkamp, Davis and Kress ("Practical Cone-Beam Algorithm"), J. Opt. Soc. Am. 612-619, 1984.

  This will be described with reference to the flowchart of the embodiment shown in FIG. An instruction to start photographing is issued via the interface unit 21 (S101). When an instruction for photographing is given, the intake air intensity is detected by the intake air intensity detector (S103). At the time of detecting the intake intensity, the subject is instructed to be in a conscious maximum intake state. If the detected intake air intensity is greater than or equal to a predetermined photographing intake air intensity, it is determined that photographing is possible and the rotation table starts rotating (S105). Even if the subject is in the conscious maximum inhalation state, the fixing belt is reset if the photographing inspiration intensity is lower (S014). The setting of the fixed belt is adjusted in the natural breathing state, but it is considered that the setting was too weak.

  The control means 18 monitors an encoder signal (not shown) generated from the rotary table 15 and confirms whether a predetermined constant speed and angle have been reached. When a predetermined constant speed and angle are reached, a signal is sent to the X-ray generation means 11 to start X-ray exposure. When the rotary table 15 rotates a predetermined rotation angle and reaches a predetermined view number (projection number), the control means 18 instructs the X-ray generation means to stop the X-ray exposure. Thereafter, the rotating table 15 is controlled to be stopped while decelerating (S106).

  Even during data collection, the intake air intensity of the subject is periodically recorded by the intake air intensity detection means 17, but at the time of completion of imaging, it is confirmed whether the intake air intensity during imaging is equal to or lower than the imaging intake air intensity (S107). . If there is no problem with the imaging intake air intensity, reconstruction is performed using the collected data (S109), and imaging ends (S112).

  However, if the inspiration intensity during photographing is less than or equal to the photographing inspiration intensity, there is a high possibility that body movement has occurred. Therefore, body motion detection is performed (S109). Data rearrangement (S110) for extracting half scan data from full scan data is performed according to the result of body motion detection, half reconstruction is performed by the half scan data (S111), and imaging is completed (S111). S112). However, as will be described later, data rearrangement (S110) and half reconstruction (S111) are performed for each divided image. Specifically, a motion area, a stop area, and a body movement area are set for each divided image area as shown in FIG. 6, and only the divided image areas corresponding to the body movement area are rearranged (S110) and half-reset. The configuration (S111) is performed for each divided image.

  Body motion detection (S109) will be described in detail. The first embodiment is a method approximate to the method disclosed in JP-A-2002-355241. The left side of FIG. 5 is an example of projection data in one direction, but for the sake of simplicity, it is assumed that the image is an image of the chest taken accidentally from the front. This image is divided into seven divided images (strip-shaped) in the Z-axis direction (body axis direction), and the mean square of the difference images before and after rotation is calculated between the divided images (hereinafter simply referred to as difference average). The graph is the right side of FIG. The difference average graphs of the divided images (1) to (4) show patterns due to the human body having an elliptical cross section, but the divided images (5) to (7) are patterns representing heart beats. It has become. Further, when the divided images (1) and (2) are compared, a similar pattern is shown from 0 degrees to 225 degrees, but after that a different pattern is obtained. This indicates that body movement has occurred in the area of the divided image (1).

  A method of detecting whether or not body motion exists in the difference average graph of each divided image will be described with reference to FIG. The point to note here is that it is necessary to separate periodic movements such as body movements and heart beats. First, spectrum analysis is performed for each divided image by Fourier transform or the like (S201). If the possibility of pulsation by the heart is detected, it is examined whether or not a spectrum having a period of 0.75 to 1.5 seconds exists (S202). If it exists, it is immediately recognized as an exercise area (S203). Next, when a spectrum indicating pulsation is not detected, the presence or absence of body movement is detected (S204). The body movement is detected by comparing the average difference between 0 degrees and 360 degrees. If the difference is equal to or less than a preset threshold value, it is assumed that there is no body movement because continuity is maintained. If no body movement is detected, the divided image is recognized as a stop area (S205). If body movement is detected, the divided image area is recognized as an exercise area (206).

  For the divided image that is recognized as the body movement area, the body movement section is further certified (S207). Based on this authorization result, half data is determined from the full scan data so as not to include the body movement section. Therefore, when there is a divided area recognized as a stop area in another divided image, a difference average difference between the divided images is calculated as shown in FIG. In the example of FIG. 7, the difference is zero until 200 degrees, and the difference occurs at 200 to 360 degrees. Specifically, half data is created in a section in which the difference of the average difference is continuously 180 + fan angles. Next, when there is no divided area recognized as a stop area in the other divided images, the continuous section for 180 + fan angle is shifted in the same manner as the method disclosed in JP-A-2000-217810, and each time Half data is determined by confirming the image quality of the reconstructed image.

Conceptual diagram of the present invention Example shooting system System block diagram of the embodiment Flow chart for executing the embodiment Motion region detection method Flow chart showing body motion region detection method Example showing detection method of body movement area

Explanation of symbols

11 X-ray generation means 12 Two-dimensional detector 13 Breast pad 14 Reconstruction means 15 Rotary table 16 Human body 17 Respiration intensity detection means 18 Control means 19 Image display means 21 Interface means 24 BUS

Claims (3)

  An X-ray imaging apparatus comprising: a top plate means for fixing a subject; a fixed belt means connected to the top plate; an intake air intensity detecting means for measuring the intake air intensity of the subject attached to the fixed belt; The imaging control means is configured to enable imaging when the intake air intensity is greater than a reference value.   In Claim 1, the said intake strength detection is calculated by detecting the tensile strength of the connection part of the said top plate and the said fixed belt.   In Claim 1, the said intake strength detection is calculated by detecting the tensile strength of the connection part between the said fixed belts.

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