JP5617577B2 - Chest diagnosis support information generation method - Google Patents

Description

The present invention relates to a method for generating chest diagnosis support information .

In contrast to still image photography and diagnosis by chest radiation using conventional film / screen or photostimulable phosphor plate, a dynamic image of the chest is taken using a semiconductor image sensor such as FPD (flat panel detector), Attempts have been made to apply it to diagnosis. Specifically, by utilizing the responsiveness of reading / erasing of image data of the semiconductor image sensor, pulsed radiation is continuously irradiated from the radiation source in accordance with the reading / erasing timing of the semiconductor image sensor. Take multiple shots per second to capture the dynamics of the chest. By sequentially displaying a series of a plurality of images acquired by imaging, a doctor can observe a series of movements of the chest accompanying respiratory motion, heart beats, and the like.

  Various techniques for extracting diagnostic support information useful for diagnosis from a dynamic image of the chest have also been proposed. For example, Patent Document 1 describes a dynamic imaging system that performs dynamic imaging of the chest, analyzes changes in amplitude and period over a plurality of respiratory cycles, and determines abnormal ventilation functions.

JP 2009-273671 A

  However, as described in Patent Document 1, dynamic imaging of the chest is performed during normal rest breathing, and the ventilation function is evaluated using signal changes (for example, amplitude information of signal value waveforms) of the obtained dynamic image. However, it is difficult to evaluate how much breathing can be performed in resting breathing.

  For example, it is assumed that the ventilation function is evaluated for the subjects A and B using the amplitude of the signal waveform during rest breathing, the evaluation of the subject A is 100, and the evaluation of the subject B is 100. In this case, since the evaluation values of the subjects A and B are the same, the evaluation of the ventilation function of the two persons is the same. In this case, it is determined that there is no abnormality in the ventilation function in both cases.

  However, it is assumed that the evaluation of the ventilation function of subject A during deep breathing is 300 and the evaluation of the ventilation function of subject B during deep breathing is 120. Then, during rest breathing, the subject A breathes with a considerable surplus power, but B breathes almost at full power. Therefore, the evaluation by only rest breathing is covered, and the subject B has an abnormality in the ventilation function.

  Further, for example, it is assumed that the ventilation function is evaluated using the signal waveform amplitude during deep breathing for the subjects A and B, the evaluation of the subject A is 300, and the evaluation of the subject B is 300. In this case, since the evaluation values of the subjects A and B are the same, the evaluation of the ventilation function of the two persons is the same. In this case, it is determined that there is no abnormality in the ventilation function in both cases.

  However, it is assumed that the evaluation of the ventilation function of the subject A during rest breathing is 100 and the evaluation of the ventilation function of the subject B during rest breathing is 280. Then, during rest breathing, the subject A breathes with a considerable surplus power, but B breathes almost at full power. Therefore, the evaluation based only on the deep breath is covered, and the subject B has an abnormality in the ventilation function.

  The subject of this invention is enabling it to evaluate a ventilation function from the new viewpoint of the remaining power evaluation at the time of rest breathing.

In order to solve the above-described problem, the chest diagnosis support information generating method according to the invention described in claim 1 includes:
A resting breathing imaging step of capturing a series of frame images by capturing at least one cycle of dynamics during resting breathing of the chest by imaging means;
A deep breath imaging step of capturing one or more frame images including a frame image of at least a maximum inspiratory position by performing imaging during the deep breathing of the chest by the imaging unit;
Based on a series of frame images obtained in the rest breathing imaging step, a first step of calculating a feature amount related to the rest breathing of the chest,
Based on one or more frame images obtained in the deep breath imaging step, a second step of calculating a feature amount related to deep breathing of the chest,
Based on the ratio of the two feature quantities calculated in the first step and the second step, a calculation step for calculating a feature amount indicating a remaining power level during rest breathing of the chest ,
including.

The invention according to claim 2 is the invention according to claim 1,
The first step calculates an amplitude value of a signal waveform at rest of the chest based on a series of frame images obtained in the rest breathing imaging step,
The second step calculates an amplitude value of a signal waveform during deep breathing of the chest based on one or more frame images obtained in the deep breath imaging step,
The calculating step is based on the ratio of the amplitude value of the signal waveform during rest breathing calculated in the first step and the amplitude value of the signal waveform during deep breathing calculated in the second step. A feature amount indicating the degree of remaining power is calculated.

The invention according to claim 3 is the invention according to claim 1 or 2,
In the deep breath imaging step, the imaging means performs imaging of the maximum inspiratory position and the maximum expiratory position during deep breathing of the chest, and a frame image corresponding to the maximum inspiratory position of the chest and two sheets corresponding to the maximum expiratory position. Generate a frame image,
In the second step, a feature amount during deep breathing of the chest is calculated based on a frame image corresponding to the maximum inspiratory position and a frame image corresponding to the maximum expiratory position obtained in the deep breath imaging step .

The invention according to claim 4 is the invention according to claim 1 or 2,
The deep breath imaging step performs imaging of only the maximum inspiratory position during deep breathing of the chest by the imaging means , and generates a single frame image corresponding to the maximum inspiratory position of the chest,
The second step is based on a frame image corresponding to the maximum inspiratory position obtained in the deep breathing imaging step and a frame image corresponding to the resting expiratory position obtained in the resting breathing imaging step, during deep breathing of the chest The feature amount is calculated .

The chest diagnosis support information generating method of the invention according to claim 5 is:
An imaging process for generating a series of frame images by imaging one cycle or more of the dynamics during rest breathing and deep breathing of the chest by imaging means,
Based on a series of frame images of each of the chest rest breath and deep breath obtained in the imaging step, calculating a feature amount related to the chest rest breath and a feature amount related to the deep breath;
Calculating a feature amount indicating a degree of remaining power during rest breathing of the chest, based on a ratio of the calculated feature amount relating to the rest breathing of the chest and a feature amount relating to deep breathing;
including.

  According to the present invention, it is possible to evaluate a ventilation function from a new viewpoint of remaining power evaluation during rest breathing, and it is possible to diagnose an abnormality without remaining power during rest breathing, which has not been regarded as abnormal in the past. .

It is a figure which shows the whole structure of the chest diagnosis assistance system in embodiment of this invention. It is a flowchart which shows the flow of imaging | photography in embodiment of this invention. 3 is a flowchart illustrating a shooting control process executed by a control unit of the shooting console of FIG. 1. It is a flowchart which shows the image analysis process performed by the control part of the diagnostic console of FIG. It is a figure which shows the frame image of several time phase T (T = t0-t6) image | photographed in one respiration cycle (during deep breathing). (A) is a figure which shows typically the amplitude which shows the ventilation volume computed from a deep breathing image, (b) is a figure which shows typically the amplitude which shows the ventilation volume computed from a rest breathing image. (A) is a figure which shows the signal waveform of the abnormal area | region of a lung field, (b) is a figure which shows the signal waveform of the normal area | region of a lung field. It is a figure which shows an example of an analysis result screen. It is a figure which shows the other example of an analysis result screen.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples.

[Configuration of Chest Diagnosis Support System 100]
First, the configuration will be described.
FIG. 1 shows the overall configuration of a chest diagnosis support system 100 in the present embodiment.
The chest diagnosis support system 100 is a system that performs dynamic imaging of the chest of the subject M, who is the subject, and calculates a feature quantity C that indicates the degree of remaining breathing power by analyzing the obtained dynamic image.

  As shown in FIG. 1, in the chest diagnosis support system 100, an imaging device 1 and an imaging console 2 are connected by a communication cable or the like, and the imaging console 2 and the diagnostic console 3 are connected to a LAN (Local Area Network). Etc., and connected via a communication network NT. Each device constituting the chest diagnosis support system 100 conforms to the DICOM (Digital Image and Communications in Medicine) standard, and communication between the devices is performed in accordance with DICOM.

[Configuration of the photographing apparatus 1]
The imaging apparatus 1 is an apparatus that captures the dynamics of the chest with periodicity (cycle) and still images of the chest, such as changes in the form of lung expansion and contraction associated with respiratory motion. Dynamic imaging is performed by continuously irradiating a human chest with radiation such as X-rays to acquire a plurality of images (that is, continuous imaging). A series of images obtained by this continuous shooting is called a dynamic image. Each of the plurality of images constituting the dynamic image is called a frame image.
As shown in FIG. 1, the imaging apparatus 1 includes a radiation source 11, a radiation irradiation control device 12, a radiation detection unit 13, a reading control device 14, and the like.

The radiation source 11 is disposed at a position facing the radiation detection unit 13 across the subject M, and irradiates the subject M with radiation (X-rays) according to the control of the radiation irradiation control device 12.
The radiation irradiation control device 12 is connected to the imaging console 2 and controls the radiation source 11 based on the radiation irradiation conditions input from the imaging console 2 to perform radiation imaging. The radiation irradiation conditions input from the imaging console 2 are, for example, pulse rate, pulse width, pulse interval during continuous irradiation, number of imaging frames per dynamic imaging, X-ray tube current value, and X-ray tube voltage value. , Filter type and the like. The pulse rate is the number of times of radiation irradiation per second, and matches the frame rate described later. The pulse width is a radiation irradiation time per one irradiation. The pulse interval is the time from the start of one radiation irradiation to the start of the next radiation irradiation in continuous imaging, and coincides with a frame interval described later.

  The radiation detection unit 13 is configured by a semiconductor image sensor such as an FPD. The FPD has, for example, a glass substrate or the like, detects radiation that has been irradiated from the radiation source 11 and transmitted through at least the subject M at a predetermined position on the substrate according to its intensity, and detects the detected radiation as an electrical signal. A plurality of pixels to be converted and stored are arranged in a matrix. Each pixel includes a switching unit such as a TFT (Thin Film Transistor).

  The reading control device 14 is connected to the imaging console 2. The reading control device 14 controls the switching unit of each pixel of the radiation detection unit 13 based on the image reading condition input from the imaging console 2 to switch the reading of the electrical signal accumulated in each pixel. Then, the image data is acquired by reading the electrical signal accumulated in the radiation detection unit 13. This image data is a frame image. Then, the reading control device 14 outputs the acquired frame image to the photographing console 2. The image reading conditions are, for example, a frame rate, a frame interval, a pixel size, an image size (matrix size), and the like. The frame rate is the number of frame images acquired per second and matches the pulse rate. The frame interval is the time from the start of one frame image acquisition operation to the start of the next frame image acquisition operation in continuous shooting, and coincides with the pulse interval.

  Here, the radiation irradiation control device 12 and the reading control device 14 are connected to each other, and exchange synchronization signals to synchronize the radiation irradiation operation and the image reading operation. In addition, at the time of dark reading for acquiring one or a plurality of dark images for calculating an offset correction coefficient used for offset correction, which will be described later, it is not synchronized with the radiation irradiation operation and is not irradiated with radiation. A series of image reading operations from data reading to reset is performed, but may be performed at any timing before or after a series of dynamic imaging.

[Configuration of the shooting console 2]
The imaging console 2 outputs radiation irradiation conditions and image reading conditions to the imaging apparatus 1 to control radiation imaging and radiographic image reading operations by the imaging apparatus 1, and also captures dynamic images acquired by the imaging apparatus 1. Displayed for confirmation of whether the image is suitable for confirmation of positioning or diagnosis.
As shown in FIG. 1, the imaging console 2 includes a control unit 21, a storage unit 22, an operation unit 23, a display unit 24, and a communication unit 25, and each unit is connected by a bus 26.

The control unit 21 includes a CPU (Central Processing Unit) and a RAM (Random Access Memory).
) Etc. The CPU of the control unit 21 reads the system program and various processing programs stored in the storage unit 22 in accordance with the operation of the operation unit 23, expands them in the RAM, and performs shooting control processing described later according to the expanded programs. Various processes including the beginning are executed to centrally control the operation of each part of the imaging console 2 and the radiation irradiation operation and the reading operation of the imaging apparatus 1.

  The storage unit 22 is configured by a nonvolatile semiconductor memory, a hard disk, or the like. The storage unit 22 stores various programs executed by the control unit 21 and data such as parameters necessary for execution of processing by the programs or processing results. For example, the storage unit 22 stores a shooting control processing program for executing the shooting control process shown in FIG. In addition, the storage unit 22 stores radiation irradiation conditions and image reading conditions in association with the examination target region. Various programs are stored in the form of readable program code, and the control unit 21 sequentially executes operations according to the program code.

  The operation unit 23 includes a keyboard having a cursor key, numeric input keys, various function keys, and the like, and a pointing device such as a mouse. The control unit 23 controls an instruction signal input by key operation or mouse operation on the keyboard. To 21. In addition, the operation unit 23 may include a touch panel on the display screen of the display unit 24. In this case, the operation unit 23 outputs an instruction signal input via the touch panel to the control unit 21.

  The display unit 24 is configured by a monitor such as an LCD (Liquid Crystal Display) or a CRT (Cathode Ray Tube), and displays an input instruction, data, or the like from the operation unit 23 in accordance with an instruction of a display signal input from the control unit 21. To do.

  The communication unit 25 includes a LAN adapter, a modem, a TA (Terminal Adapter), and the like, and controls data transmission / reception with each device connected to the communication network NT.

[Configuration of diagnostic console 3]
The diagnostic console 3 acquires a dynamic image (a series of frame images) and a still image from the imaging console 2, and analyzes the acquired image, for example, diagnostic support such as a feature amount C indicating the degree of remaining breathing capacity. It is a device for creating and displaying information.
As shown in FIG. 1, the diagnostic console 3 includes a control unit 31, a storage unit 32, an operation unit 33, a display unit 34, and a communication unit 35, and each unit is connected by a bus 36.

  The control unit 31 includes a CPU, a RAM, and the like. The CPU of the control unit 31 reads out the system program and various processing programs stored in the storage unit 32 in accordance with the operation of the operation unit 33 and expands them in the RAM, and performs image analysis described later according to the expanded programs. Various processes including the process are executed to centrally control the operation of each part of the diagnostic console 3.

  The storage unit 32 is configured by a nonvolatile semiconductor memory, a hard disk, or the like. The storage unit 32 stores data such as parameters necessary for execution of processing or data such as processing results by various programs and programs including an image analysis processing program for executing image analysis processing by the control unit 31. These various programs are stored in the form of readable program codes, and the control unit 31 sequentially executes operations according to the program codes.

  The operation unit 33 includes a keyboard having cursor keys, numeric input keys, various function keys, and the like, and a pointing device such as a mouse. The control unit 33 controls an instruction signal input by key operation or mouse operation on the keyboard. To 31. The operation unit 33 may include a touch panel on the display screen of the display unit 34, and in this case, an instruction signal input via the touch panel is output to the control unit 31.

  The display unit 34 is configured by a monitor such as an LCD or a CRT, and displays an input instruction, data, or the like from the operation unit 33 in accordance with an instruction of a display signal input from the control unit 31.

  The communication unit 35 includes a LAN adapter, a modem, a TA, and the like, and controls data transmission / reception with each device connected to the communication network NT.

[Operation of Chest Diagnosis Support System 100]
Next, the operation in the chest diagnosis support system 100 will be described.

(Operation of the photographing apparatus 1 and the photographing console 2)
First, the photographing operation by the photographing apparatus 1 and the photographing console 2 will be described.
FIG. 2 shows a photographing flow by the photographing apparatus 1 and the photographing console 2.
As shown in FIG. 2, first, the operation section 23 of the imaging console 2 is operated by the imaging engineer, and patient information (patient name, height, weight, age, sex, etc.) of the imaging target (subject M) is input. Performed (step S1). Next, rest breathing imaging is performed (step S2). Next, imaging of deep breathing is performed (step S3). Hereinafter, the imaging control process executed by the control unit 21 of the imaging console 2 in step S2 and step S3 will be described.

  FIG. 3 shows a flowchart of the photographing control process. The photographing control process is executed in cooperation with the photographing control processing program stored in the control unit 21 and the storage unit 22.

  First, the radiation irradiation conditions are read from the storage unit 22 and set in the radiation irradiation control device 12, and the setting conditions such as the image reading conditions are read from the storage unit 22 and set in the reading control device 14 ( Step S101). In the case of taking a rest breath, the setting for taking a rest breath is taken, and in the case of taking a deep breath, the setting for taking a deep breath is taken. When the radiation exposure conditions and the image reading conditions are the same for both radiographs, settings during radiographing are omitted.

  Next, a radiation irradiation instruction by the operation of the operation unit 23 is waited (step S102). Here, the shooter prepares for shooting such as positioning of the subject M in the shooting apparatus 1. When taking a rest breath in step S2 in FIG. 2, the subject (subject M) is instructed to make it easier, and urged to continue the rest breath. When photographing deep breathing in step S3, the subject M is instructed to breathe in accordance with the announcement. When preparation for imaging is completed, the operation unit 23 is operated to input a radiation irradiation instruction.

When a radiation irradiation instruction is input from the operation unit 23 (step S102; YES), a photographing start instruction is output to the radiation irradiation control device 12 and the reading control device 14, and dynamic photographing is started (step S103). That is, radiation is emitted from the radiation source 11 at a pulse interval set in the radiation irradiation control device 12, and a frame image is acquired by the radiation detection unit 13. In the case of taking a deep breath image, the image is taken while making an announcement for inducing deep breaths such as “inhale and exhale greatly”. It is preferable that the photographing apparatus 1 is provided with an audio output device, a speaker, and the like, and an announcement for guiding deep breathing is performed in conjunction with photographing.
When photographing of a predetermined number of frames is completed, the control unit 21 outputs a photographing end instruction to the radiation irradiation control device 12 and the reading control device 14, and the photographing operation is stopped. The number of frames to be captured is the number of frames that can be captured for at least one respiratory cycle.

The frame images acquired by shooting are sequentially input to the shooting console 2, and correction processing is performed on each frame image (step S104). In the correction process of step S5, four correction processes including an offset correction process, a gain correction process, a defective pixel correction process, and a lag (afterimage) correction are performed as necessary.
First, an offset correction process is performed on each acquired frame image, and an offset value caused by a dark current superimposed on each acquired frame image is removed. In the offset correction process, for example, a process of subtracting an offset correction coefficient stored in advance from each pixel value (density value; hereinafter referred to as a signal value) of each acquired frame image is performed. Here, the offset correction coefficient is an image obtained by averaging a plurality of dark images (frame images) acquired in advance when radiation is not irradiated.
Next, a gain correction process is performed, and pixel-to-pixel variations caused by individual differences between detection elements corresponding to the pixels of each frame image and gain unevenness of the readout amplifier are removed. In the gain correction process, for example, a process of multiplying each frame image after the offset correction by a gain correction coefficient stored in advance is performed. Here, the gain correction coefficient is an image obtained by averaging a plurality of offset-corrected frame images acquired when the radiation detector 13 is uniformly irradiated with radiation, and an output signal value expected under the radiation irradiation conditions at this time. Thus, the coefficient is calculated and stored in advance so that the corrected signal value of each pixel becomes uniform.
Next, defective pixel correction processing is performed to remove pixels whose sensitivity is non-linear compared to surrounding pixels and missing pixels that have no sensitivity. In the defective pixel correction processing, for example, in accordance with the defective pixel position information map stored in advance, in each defective pixel registered in the defective pixel position information map, the signal value of the defective pixel is averaged of the signal values of the pixels that are not defective in the vicinity thereof. Processing to replace with a value is performed. Here, in the defective pixel position information map, a plurality of defective pixels are recognized in advance from the offset-corrected and gain-corrected frame images acquired when the radiation detecting unit 13 is uniformly irradiated with radiation, and the positions of the defective pixels are detected. Is a registered map. In the offset correction coefficient, gain correction coefficient, and defective pixel position information map, optimum values are stored in advance according to collection modes such as binning and dynamic range, and optimum values corresponding to the respective collection modes are stored. Is read out.
Next, lag (afterimage) correction is performed. Lag is a phenomenon in which the effect of the previous radiation exposure appears in the current frame image, and it may appear differently depending on the detector configuration, frame rate, etc. Is done. Note that when performing inter-frame difference processing using each frame image, the lag effect may be ignored, so that correction processing is performed as necessary. Similarly, in the above-described offset correction process, gain correction process, and defective pixel correction process, the correction process may be omitted when priority is given to the analysis processing speed over the accuracy of the analysis result.

  Next, each frame image after the correction processing is associated with a number indicating the shooting order and stored in the storage unit 22 (step S105) and displayed on the display unit 24 (step S106). Here, immediately before each frame image is stored, the signal value of each pixel of each frame image may be stored after being subjected to logarithmic conversion processing for converting from a true number to a logarithm. The imaging engineer confirms the positioning and the like based on the displayed dynamic image, and determines whether an image suitable for diagnosis is acquired by imaging (imaging OK) or re-imaging is necessary (imaging NG). Then, the operation unit 23 is operated to input a determination result. Note that the frame images acquired by shooting may be input together after the completion of all shooting.

  When a judgment result indicating photographing OK is input by a predetermined operation of the operation unit 23 (step S107; YES), an identification ID for identifying a dynamic image or each of a series of frame images acquired by dynamic photographing is displayed. Information such as patient information, examination target region, radiation irradiation condition, image reading condition, imaging order number, imaging date and time are attached (for example, written in the header area of the image data in DICOM format), and the communication unit 25 is To the diagnostic console 3 (step S108). Then, this process ends. On the other hand, when a determination result indicating shooting NG is input by a predetermined operation of the operation unit 23 (step S107; NO), a series of frame images stored in the storage unit 22 is deleted (step S109), and the shooting ends. To do. In this case, re-photographing is executed.

  Note that the order of resting breathing and deep breathing may be interchanged.

(Operation of diagnostic console 3)
Next, the operation in the diagnostic console 3 will be described.
In the diagnostic console 3, when a series of frame images necessary for image analysis is received from the imaging console 2 via the communication unit 35, an image analysis processing program stored in the control unit 31 and the storage unit 32 The image analysis processing shown in FIG.

Hereinafter, the flow of image analysis processing will be described with reference to FIG.
First, a lung field region is extracted from each frame image of a rest breathing image group obtained by photographing rest breathing and a deep breath image group obtained by photographing deep breathing (step S21).
Any method may be used to extract the lung field region. For example, a threshold value is obtained by discriminant analysis from a histogram of signal values (density values) of each pixel of a reference image (reference image) in a series of frame images, and a region having a signal higher than this threshold value is set as 1 as a lung field region candidate. Next extract. Next, edge detection is performed in the vicinity of the boundary of the first extracted lung field region candidate, and the boundary of the lung field region can be extracted by extracting along the boundary the point where the edge is maximum in a small region near the boundary. it can.
The reference image is preferably a frame image at the maximum inspiration level during deep breathing. The image of the maximum inspiratory position can be selected, for example, by extracting the lung field region in each frame image and selecting the image having the largest area as the frame image of the maximum inspiratory position. Since the maximum inspiratory position is a state in which the lung field has expanded to the maximum, the frame field in the maximum inspiratory position can be selected as a reference image, so that the lung field can be widely analyzed.

Next, the lung field region of each frame image is divided into a plurality of small regions, and the small regions of each frame image are associated with each other (step S22).
Specifically, corresponding point extraction processing (local matching processing) for extracting corresponding points between the frame images and nonlinear distortion conversion processing (warping processing) are performed to divide each frame image into a plurality of small regions. An area in which the same part of the field area is drawn is associated between the frame images. The position of the pixel in each small area is stored in the RAM of the control unit 31.

In the local matching process, first, the lung field region extracted from the reference image is divided into small regions made of, for example, a 5 mm square.
Next, P1 is a reference image, and a frame image adjacent to the reference image is P2 (a frame image in which the shooting order is adjacent (that is, a frame image adjacent in time, the same applies hereinafter)), and P2 is set to each subregion of P1. Set the search area. Here, the search area of P2 has the same center point (x, y), and the vertical and horizontal widths are smaller than those of the small area of P1, where the coordinates of the center point in each small area of P1 are (x, y). Set to be large (for example, 1.5 times). Then, for each region of P1, a corresponding position on P2 for each small region of P1 is calculated by obtaining a region having the highest matching degree in the search range of P2. As the matching degree, the least square method or the cross correlation coefficient is used as an index. Then, the lung field area of P2 is divided at the corresponding position of each small area of P1.
Next, P2 is newly regarded as P1, the next frame image adjacent to the new P1 is regarded as new P2, and the corresponding position of P2 in each small region of P1 is calculated. By repeating the above processing, it is possible to determine which position in each adjacent frame image each small region of each frame image corresponds to.
For the frame image during rest breathing, first, the local matching process and the warping process are performed by setting the reference image as P1, the frame image in the resting inspiratory position where the area of the lung field is maximized during rest breathing, and then the warping process. The local matching process and the warping process are performed by setting P1 as the frame image at the rest inspiratory position and P2 as the frame image adjacent thereto. Thereby, the lung field regions of all the frame images obtained by the series of imaging can be aligned with the lung field region of the frame image at the maximum inspiratory position during deep breathing. The obtained processing result is stored in the RAM of the control unit 31.

  Next, a warping process is performed. Specifically, P1 is a reference image, and P2 is a frame image in which the shooting order is adjacent (temporally adjacent), and the corresponding position of each small region between adjacent frame images calculated by the local matching process. Based on the above, a shift vector from P1 to P2 is calculated for each small region. Next, the calculated shift vector is fitted with a polynomial, and the shift vector of each pixel in each small region is calculated using this polynomial. Then, warping processing is performed based on the calculated shift vector of each pixel, and the position of each pixel in each small area of P2 is shifted to the position of the corresponding pixel in the frame image of P1. Next, the warping process P2 is newly regarded as P1, and the next frame image adjacent to the new P1 is regarded as a new P2, and the above process is performed. By sequentially repeating the above processing, the positions of the small areas of all the frame images can be substantially matched with the reference image. The correspondence of the position of the small area between the frame images is stored in the RAM of the control unit 31.

  Next, an average signal value is calculated in each small region of each frame image, and the signal value in the small region is replaced with this signal value (step S23).

  Next, a low-pass filter process in the time axis direction is performed (step S24). This low-pass filter process is a process for extracting the time change of the signal value due to ventilation. For example, a waveform of the signal value is created for each small region, and a cut-off frequency of 0.7 Hz for a rest breathing image group, The deep breathing image group is filtered at a cutoff frequency of 0.5 Hz.

  Next, for each of the rest breathing image group and the deep breathing image group, the amplitude value ANs of the signal waveform during rest breathing and the amplitude value ADs of the signal waveform during deep breathing are calculated (step S25). The amplitude value of the signal waveform can be obtained by calculating the difference between the maximum signal value (maximum value) and the minimum signal value (minimum value) in one respiratory cycle for each small region.

  Here, one respiratory cycle is composed of an expiration period and an inspiration period. FIG. 5 is a diagram showing frame images of a plurality of time phases T (T = t0 to t6) taken in one breathing cycle (during deep breathing). As shown in FIG. 5, during the expiration period, air is exhausted from the lungs by raising the diaphragm, and the area of the lung field is reduced. Along with this, the density of the lung field increases, so that the amount of radiation transmitted through the lung field and the signal value of the image indicating this decrease. At the maximum expiratory position, the diaphragm is in the highest position. During the inspiration period, air is taken into the lungs as the diaphragm descends, and the lung field region in the thorax increases as shown in FIG. Along with this, the density of the lung field decreases, so the amount of radiation transmitted through the lung field and the signal value indicating this increase. Therefore, for each small region of the deep breath image group, create a coordinate plane with the horizontal axis as the elapsed time from the start of imaging and the vertical axis as the average signal value of the pixels, and the elapsed time from the start of imaging of each frame image as When plotting the points where the average signal values calculated for the small area intersect, as shown in FIG. 6A, a waveform having the maximum inspiratory position as the maximum signal value and the maximum expiratory position as the minimum signal value can be obtained. . The difference between the maximum signal value and the minimum signal value is the amplitude ADs of the signal waveform, which corresponds to the ventilation volume. In the case of rest breathing, as shown in FIG. 6 (b), a waveform having a shorter cycle and amplitude than that during deep breathing can be obtained.

Next, for each small region, based on the amplitude value ADs of the signal waveform at the time of deep breathing and the amplitude value ANs of the signal waveform at the time of resting breathing, a feature amount C indicating the degree of remaining power during breathing is calculated ( Step S26).
The feature amount C can be obtained by the following equation (1).
Feature value C = Amplitude value ANs of signal waveform during rest breathing ÷ Amplitude value ADs of signal waveform during deep breathing (1)
When the ventilation function is functioning normally, breathing can be performed using only a part of the lung field during resting breathing, so that the remaining capacity remains compared to deep breathing where the entire lung field is used for full breathing. At this time, as shown in the lower graph of FIG. 7, the difference between the amplitude ADs during deep breathing and the amplitude ANs during rest breathing is large. That is, the value of the feature amount C becomes small. However, if the ventilation function is not functioning normally, even during resting breathing, breathing is performed using the power of the entire lung field, and there is no remaining power. At this time, as shown in the upper graph of FIG. 7, the difference between the amplitude value ADs during deep breathing and the amplitude value ANs during rest breathing is small, and the value of the feature amount C is close to 1.

When the calculation of the feature amount of each small region is completed, the analysis result is displayed on the display unit 34 (step S27).
FIG. 8 shows an example of the analysis result screen 341 displayed on the display unit 34 in step S27. As shown in FIG. 8, on the analysis result screen 341, a still image 34a in which each small area is displayed in a color (or luminance) corresponding to the feature amount C, and a color (or luminance) displayed in the still image 34a. And a display 34b showing the relationship between the feature amount C and the feature amount C. Here, the reference image is used as the still image. With this display, the doctor can grasp whether or not there is an abnormal part that has no surplus in the ventilation function during rest breathing, and only by glance at the abnormal part.

In step S27, a histogram indicating the distribution of feature values for each small area may be displayed together.
FIG. 9 shows an example of the analysis result screen 342 displayed on the display unit 34 in step S27. As shown in FIG. 9, the analysis result screen 342 displays a histogram 34c indicating the frequency of each feature quantity C in addition to the still image 34a and the display 34b similar to the analysis result screen 341. The histogram 34c allows the doctor to roughly grasp the ratio and distribution of the normal small area and the abnormal small area in the entire lung field.
Even if the still image 34a and the histogram 34c are arranged, the correspondence between the small area and the histogram may be difficult to understand at a glance. Therefore, when a point on the histogram (for example, a plurality of points with a feature amount ranging from 0 to 0.2 may be selected at a plurality of points, for example) may be selected by the operation unit 33, an area corresponding to the selected point of the still image 34a ( Only the attention area) may be colored and displayed. This makes it possible for the doctor to grasp at a glance where the attention area corresponding to the point on the histogram exists in the lung field.
Further, the ratio or the like of the attention area corresponding to the selected point with respect to the total area of the lung field may be calculated and displayed. In this way, the doctor can quantitatively grasp, for example, how much of the whole lung field is occupied by an abnormal part having little surplus power.

In addition, in the still image 34a displayed on the analysis result screen 341 or 342, when a small area is selected by the operation unit 33, the determination result is analyzed by determining whether the ventilation function of the selected small area is normal or abnormal. It may be displayed on the result screen 341 or 342. The determination of normal or abnormal can be made by comparing the feature amount C with a predetermined threshold value.
Here, the ventilation volume (spiratory capacity) of a general adult during deep breathing is 3000 to 4000 mL for men and 2000 to 3000 mL for women. A typical adult's ventilation during rest breathing is about 500 mL. Therefore, the ventilation volume at the time of male rest breathing is 6 to 1/8 of the ventilation volume at the time of deep breathing, and the ventilation volume at the time of female rest breathing is 4 to 1/6 of the ventilation volume at the time of deep breathing. Therefore, in the present embodiment, the threshold is set to 1/4 (= 0.25), and it is determined that the characteristic amount C is abnormal when the characteristic amount C is larger than 0.25, and is normal when the characteristic amount C is 0.25 or less. In addition, although the ventilation volume at the time of a general deep breath and the ventilation volume at the time of rest breathing are calculated | required by three-dimensional measurement data, what is calculated | required by analyzing a dynamic image is two-dimensional measurement data. Therefore, the above threshold value is a temporary estimate and is not limited to this.

(Modification 1)
In the above embodiment, the resting breathing and the deep breathing were photographed dynamically, but for the deep breathing, by taking only two frames of the maximum inspiratory position frame image and the maximum expiratory position frame image, for example, each frame image When the imaging apparatus 1 having a configuration in which the radiation dose is constant is used, it is possible to reduce the exposure dose of the patient. While resting breathing and resting breathing positions cannot be intentionally performed in resting breathing, in deep breathing, it is possible to take a picture of when the patient breathes in and out as much as possible. is there. The signal values of the small regions of the two images, the maximum inspiratory frame image and the maximum expiratory frame image, correspond to the maximum signal value and the minimum signal value in one deep breath cycle, respectively. An analysis result equivalent to that when performing dynamic imaging can be obtained while suppressing the amount.

  In this case, in step S2 of FIG. 2, deep breathing is induced, and only two imagings of the maximum inspiratory position and the maximum expiratory position are performed. In the image analysis process of FIG. 4, the low-pass filter process in step S24 is performed only on the resting breathing image group. This is because the deep breath image group has only two frame images, and it is difficult to extract only ventilation information even if processing is performed. In addition, since the signal change by a blood flow is small compared with the signal change by deep respiration, it is thought that there is little influence on a process even if it does not perform a low-pass filter process. Other processes are the same as those in the above embodiment.

(Modification 2)
Furthermore, in order to reduce the exposure dose of the patient, only the frame image at the maximum inspiratory position may be taken for deep breathing. In this way, the exposure dose of the patient can be further reduced.
In this case, in step S2 in FIG. 2, deep breathing is induced and only one imaging at the maximum inspiratory position is performed. In the image analysis process of FIG. 4, the low-pass filter process in step S24 is performed only on the resting breathing image group. This is because the deep breath image has only one frame image, and it is difficult to extract only ventilation information even if processing is performed. In addition, since the signal change by a blood flow is small compared with the signal change by deep respiration, it is thought that there is little influence on a process even if it does not perform a low-pass filter process. Further, the feature amount (referred to as C2) indicating the degree of remaining breathing power can be obtained by the following equation (2).
Feature value C2 = Amplitude value ANs of signal waveform during rest breath / (maximum inspiratory position signal value−rest expiratory signal value) (2)
That is, instead of the signal value of the frame image at the maximum expiratory position, the signal value of the frame image at the resting expiratory position is used to calculate the feature amount C2 indicating the evaluation of the respiratory ventilation function.
Here, since (maximum inspiratory position signal value−maximum expiratory signal value)> (maximum inspiratory position signal value−rest expiratory signal value), the threshold for determining normality / abnormality is an expression It is thought that it is necessary to make it larger than that applied to the feature amount C calculated in (1). Other processes are the same as those in the above embodiment.
In this case, it is possible to calculate a feature amount (referred to as C3) indicating the degree of remaining breathing ability by the following processing.
A frame image at a resting inspiratory position is extracted from a group of resting breathing images. Using the image and a frame image at the maximum inspiratory position during deep breathing, the horizontal axis represents each detector ( The output value indicated by (pixel) and a histogram with the vertical axis representing its appearance are generated, and the area of the lung field area (the central part of the histogram excluding output values corresponding to the direct irradiation area and the non-irradiation area) of the histogram It is also possible to calculate the feature amount C3 = area of rest histogram / area of deep breath histogram.

  As described above, according to the chest diagnosis support system 100, the imaging device 1 and the imaging console 2 capture one cycle or more of the dynamics of the chest during rest breathing to generate a series of frame images and deep chest breathing. Occasionally, one or more frame images including at least the maximum inspiratory position frame image are generated and a series of frame images showing the chest dynamics during rest breathing in the diagnostic console 3 and at least the maximum inspiratory position during deep breathing Based on one or more frame images including the corresponding frame image, a feature amount indicating the degree of remaining power during rest breathing of the chest is calculated and output.

  Therefore, since the feature quantity indicating the degree of remaining power during rest breathing is calculated based on the comparison between rest breathing and deep breathing, the conventional method of analyzing images taken during rest breathing or deep breathing is abnormal. It is possible to provide diagnosis support information for an abnormality that has not been determined and has no power during rest breathing.

  During shooting, dynamic images are taken during rest breathing and deep breathing, and feature quantities indicating the remaining power during rest breathing are calculated based on a series of obtained frame images. It becomes possible to provide as.

Further, by taking only two images of the maximum expiratory position and the maximum inspiratory position during the deep breathing, the exposure dose of the patient can be obtained when using a photographing apparatus with a constant radiation dose per frame image of the dynamic image. Can be reduced.
Furthermore, the exposure of the patient can be further reduced by performing imaging during deep breathing only for one imaging at the maximum inspiratory position.

In addition, the said embodiment is a suitable example of this invention, and is not limited to this.
For example, in the above description, an example in which a hard disk, a semiconductor nonvolatile memory, or the like is used as a computer-readable medium of the program according to the present invention is disclosed, but the present invention is not limited to this example. As another computer-readable medium, a portable recording medium such as a CD-ROM can be applied. Further, a carrier wave is also applied as a medium for providing program data according to the present invention via a communication line.

  In addition, the detailed configuration and detailed operation of each device constituting the chest diagnosis support system 100 can be changed as appropriate without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 Chest diagnosis support system 1 Imaging device 11 Radiation source 12 Radiation irradiation control device 13 Radiation detection unit 14 Reading control device 2 Imaging console 21 Control unit 22 Storage unit 23 Operation unit 24 Display unit 25 Communication unit 26 Bus 3 Diagnosis console 31 Control unit 32 Storage unit 33 Operation unit 34 Display unit 35 Communication unit 36 Bus

Claims (5)

A resting breathing imaging step of capturing a series of frame images by capturing at least one cycle of dynamics during resting breathing of the chest by imaging means;
A deep breath imaging step of capturing one or more frame images including a frame image of at least a maximum inspiratory position by performing imaging during the deep breathing of the chest by the imaging unit;
Based on a series of frame images obtained in the rest breathing imaging step, a first step of calculating a feature amount related to the rest breathing of the chest,
Based on one or more frame images obtained in the deep breath imaging step, a second step of calculating a feature amount related to deep breathing of the chest,
Based on the ratio of the two feature quantities calculated in the first step and the second step, a calculation step for calculating a feature amount indicating a remaining power level during rest breathing of the chest,
A method of generating support information for chest diagnosis including The first step calculates an amplitude value of a signal waveform at rest of the chest based on a series of frame images obtained in the rest breathing imaging step,
The second step calculates an amplitude value of a signal waveform during deep breathing of the chest based on one or more frame images obtained in the deep breath imaging step,
The calculating step is based on the ratio of the amplitude value of the signal waveform during rest breathing calculated in the first step and the amplitude value of the signal waveform during deep breathing calculated in the second step. The chest diagnosis support information generation method according to claim 1, wherein a feature amount indicating a degree of remaining power is calculated. In the deep breath imaging step, the imaging means performs imaging of the maximum inspiratory position and the maximum expiratory position during deep breathing of the chest, and a frame image corresponding to the maximum inspiratory position of the chest and two sheets corresponding to the maximum expiratory position. Generate a frame image,
2. The second step calculates a feature amount during deep breathing of the chest based on a frame image corresponding to the maximum inspiratory position and a frame image corresponding to the maximum expiratory position obtained in the deep breath imaging step. Or the method for generating support information for chest diagnosis according to 2; The deep breath imaging step performs imaging of only the maximum inspiratory position during deep breathing of the chest by the imaging means, and generates a single frame image corresponding to the maximum inspiratory position of the chest,
The second step is based on a frame image corresponding to the maximum inspiratory position obtained in the deep breathing imaging step and a frame image corresponding to the resting expiratory position obtained in the resting breathing imaging step, during deep breathing of the chest The chest diagnosis support information generation method according to claim 1, wherein the feature amount is calculated . An imaging process for generating a series of frame images by imaging one cycle or more of the dynamics during rest breathing and deep breathing of the chest by imaging means,
Based on a series of frame images of each of the chest rest breath and deep breath obtained in the imaging step, calculating a feature amount related to the chest rest breath and a feature amount related to the deep breath;
Calculating a feature amount indicating a degree of remaining power during rest breathing of the chest, based on a ratio of the calculated feature amount relating to the rest breathing of the chest and a feature amount relating to deep breathing;
A method of generating support information for chest diagnosis including