JP3554129B2 - Radiography equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a radiation imaging apparatus that captures an image of a subject using radiation.
[0002]
[Prior art]
(1) FIG. 33 shows a configuration diagram of a radiation imaging apparatus according to a first conventional example, in which a radiation image imaging means for imaging a transmitted radiation image of a subject S in front of radiation irradiation means 1 which is a radiation source for generating radiation. The radiation irradiating means 1 and the radiation image photographing means 2 irradiate the radiation based on the photographing conditions set by the operator with the photographing condition setting means 3, for example, the tube voltage, the tube current and the irradiation time. Take a picture.
[0003]
(2) Conventional radiography is performed using a system combining a film and an intensifying screen. In recent years, with the development of computers, various digital image photographing apparatuses have been developed and are being used clinically. An imaging device using a stimulable phosphor sheet, one of which is to record a radiation image of the subject S once on the stimulable phosphor sheet, and then emit excitation light such as laser light to the stimulable phosphor sheet A radiation image of the subject S is displayed on a silver halide film or a CRT display based on an image signal obtained by irradiating the sheet with photostimulable light and photoelectrically reading the light.
[0004]
An imaging device using a light detection array converts a radiation image of the subject S into a visible image using a scintillator or an image intensifier, converts the visible image into an image signal using the light detection array, and converts the image signal into a signal. A radiation image of the subject is displayed on a silver halide film or a CRT display based on the image.
[0005]
(3) Further, in radiography in the medical field, it is necessary to adapt the condition setting of radiography to the state and characteristics of the subject S in order to obtain a high-quality image without performing re-imaging. That is, it is required to optimize a radiation field, a radiation quality, and a radiation dose, and in a digital radiation image, appropriate image processing is required to make it easy to see.
[0006]
FIG. 34 shows a configuration diagram of a radiation imaging apparatus of a second conventional example. When radiation is irradiated from the radiation irradiating means 1 to the subject S, the internal structure of the subject S is affected by the interaction of the subject S with the radiation such as absorption and scattering. The radiation is intensity-modulated and scattered in accordance with, and reaches the radiation image capturing means 2 to become a radiation image. The grid 4 arranged before the radiation image capturing means 2 is for removing the scattered radiation and improving the contrast of the radiation image.
[0007]
Generally, the radiation image capturing means 2 is a phosphor CaWO that emits fluorescence having an intensity proportional to the irradiation radiation dose. _Four The subject S is recorded on the film as a latent image, is presented as a visible image giving a density proportional to the logarithm of the amount of fluorescence after the development processing, and is used for diagnosis and inspection.
[0008]
Also, a computed radiography (CR) device using a BaFBr: Eu phosphor emitting stimulable fluorescence and an imaging plate coated with the BaF: Eu phosphor has been used. This CR apparatus temporarily records a radiation image of the subject S on an imaging plate, and thereafter irradiates the imaging plate with excitation light such as laser light to cause stimulable emission, and photoelectrically reads this light to obtain the image. A radiation image of the subject S is displayed on a silver halide film or a CRT display based on the image signal.
[0009]
More recently, a technique has been developed for acquiring a digital image using a photoelectric conversion device in which pixels composed of minute photoelectric conversion elements, switching elements, and the like are arranged in a grid pattern in the radiation image capturing means 2.
[0010]
(4) In radiation imaging, it is important to obtain high-quality images without re-imaging, and it is necessary to select optimal radiation imaging conditions according to the state and characteristics of the subject S and the state and characteristics of the radiation imaging apparatus. There is. That is, it is necessary to narrow down the radiation irradiation field and optimize the radiation quality and irradiation dose. Further, when the radiographic image is digitally processed, it is necessary to determine the position of the subject S and extract the contour.
[0011]
Conventionally, a lead diaphragm is provided immediately after the radiation generator and the diaphragm is manually moved to narrow the radiation irradiation field. A visible light source is provided at the position of the conjugate, and the degree to which the projection light is lost by the aperture is visually observed by a human. In addition, in the X-ray fluoroscopic apparatus, the irradiation range is confirmed in advance on a television monitor.
[0012]
In setting the radiation quality and the irradiation dose, the photographer determines appropriate conditions based on the body position and imaging region of the subject S and performs the setting, or the photographer inputs the body position and imaging region information of the object S to the apparatus. Then, the device automatically sets appropriate conditions.
[0013]
[Problems to be solved by the invention]
(B) However, in the above-mentioned conventional example (1), the operator needs to set the optimal imaging conditions in order to obtain a radiation image that is easy to observe. The positional relationship between the two needs to be changed, and each time the distance between the two must be measured with a measure. In addition, during a period of inexperience in using the apparatus, such as after installation of the imaging apparatus, it is necessary to create an irradiation condition table or the like and perform photographing while referring to the irradiation condition table. It is necessary to directly measure the chest thickness using an instrument such as a chest measurement device in contact with the subject who becomes S.
[0014]
(B) Further, in the above-mentioned conventional example (2), when over-exposure or under-exposure occurs due to improper setting of photographing conditions, an image processing means for outputting an image with optimum density and contrast is provided. There is a device that performs the image processing, and a device that includes a determining unit that determines a photographing position, a photographing site, and an irradiation field of the subject S in order to optimally perform the image processing. However, since the radiation image of the subject S is used for these determinations, the sample size is large, for example, 1024 × 1024, the quantization number is 12 bits, and the image size is large. There are problems such as difficulty in accurately performing pattern matching and irradiation field recognition of the subject S due to the influence.
[0015]
(C) In the above-mentioned conventional example (3), the movable radiation diaphragm 5 provided immediately before the radiation irradiating means 1 is manually adjusted in order to narrow the irradiation field of the radiation from the radiation irradiating means 1. A light source 6 is provided at a position conjugate with the radiation irradiating means 1, and the degree of lack of projection light from the movable radiation diaphragm 5 is visually checked to confirm an irradiation field. In this case, the operator needs to stand on the radiation irradiating means 1 side to view the projection light, and must adjust the width of the radiation movable diaphragm 5 every time the subject S is changed. Required. In particular, in the case of chest imaging, in order to alternately capture the front image and the side image of the same subject S, the width of the aperture must be adjusted once each time. In some cases, the narrow radiation side image may be photographed as it is without stopping the movable radiation diaphragm 5.
[0016]
However, when a side image of the subject S is photographed in a state where the movable movable diaphragm 5 is opened without being stopped in this way, radiation is irradiated to an area invalid for the photographing, so-called a region that is not absorbed by the human body. The radiation in the transparent state directly reaches the phototimer light receiving unit 7 for automatically controlling the irradiation dose. Therefore, the detection error of the irradiation dose increases due to the radiation, and there is a problem that the irradiation dose cannot be detected correctly.
[0017]
Usually, the front and sides of the chest are imaged with different radiation qualities, but at present, the operator visually checks the body position, switches the radiation tube voltage on the console of the radiation generator, and connects the front and the chest. I am shooting the side.
[0018]
In a radiographic imaging apparatus in which a radiation image intensifier and a television camera are combined, radiographic observation is performed on a television monitor prior to film shooting, so that the radiation range can be visually checked. In this case, the operator does not need to stand on the side of the radiation irradiating means, and can adjust the aperture by remote control. However, if an attempt is made to extract a subject area from a subject perspective image in order to automate the adjustment of the aperture, the contour is blurred due to the effects of scattered radiation and the like, so that it becomes difficult to extract the area. In addition, the subject S is also irradiated with the radiation during the fluoroscopic observation.
[0019]
On the other hand, in a CR device using an imaging plate, a signal level is grasped by coarse scanning using a weak laser beam called pre-reading to extract a subject area and optimize scanning conditions for main reading. Since it is performed after the photographing of the subject S, it does not help to optimize the photographing itself. Further, similarly to the case of the radiographic imaging apparatus, the extraction of the subject region is considerably difficult due to the influence of scattered radiation and the like.
[0020]
As described above, the setting of the imaging conditions and the like of the radiation imaging apparatus is performed by the operator observing the subject S visually, narrowing the irradiation field in accordance with the size of the subject S, and setting the radiation quality according to the frontal photographing and the side photographing. Is adjusted, and the gain switching of the photo timer is performed manually.
[0021]
However, it is difficult for the radiation imaging apparatus to accurately recognize the subject area, in particular, because information for recognizing the state and characteristics of the subject S must depend on the operator. Further, in order to reduce the work load, the operator may omit the setting for each subject S, for example, the work of narrowing down the irradiation field, and as a result, an image with inappropriate image quality may be taken. . For example, if radiation is emitted to an area that is invalid for imaging, the phototimer may misrecognize due to the effect of through-radiation, and a desired irradiation dose may not be given, and an effective radiation image may not be obtained. Also, if the radiation quality is not switched to produce a difference in the amount of radiation depending on whether the subject S is a thin front image or a thick side image, an effective radiation image cannot be obtained, Radiation.
[0022]
(D) In the above-mentioned conventional example (4), in the imaging site where the imaging cycle represented by the group examination is fast, the adjustment of the position of the lead stop made every time the subject S changes is cumbersome, and particularly in the chest region. In photographing, a front image and a side image may be alternately photographed for one subject S, and adjustment must be performed each time. For this reason, there is a case where an image is taken with the aperture opened, and when an object S having a small width such as a side image is imaged in this state, the radiation irradiation amount is automatically controlled due to the influence of radiation that is not absorbed by the human body. The detection error of the photo timer of the automatic exposure means increases, and an appropriate irradiation dose cannot be obtained. As a result, since sufficient subject information cannot be obtained from the acquired image, re-imaging is forced.
[0023]
Further, the optimization of the radiation quality set manually is necessary to improve the image quality. However, since the optimum conditions differ depending on the subject part or the subject body position, the setting for each subject S is performed similarly to the case of the lead diaphragm. Is extremely troublesome, so that all subjects S are photographed under the same conditions. In addition, there is a problem that an effective radiation image cannot be obtained unless the gain of the photo timer is switched due to a difference in the amount of scattered radiation reaching the subject body position between the front photographing and the side photographing. There is also a risk that inappropriate shooting will be performed.
[0024]
(E) In any case, in any case, it is difficult to perform photographing accurately according to the subject.
[0025]
An object of the present invention is to solve the above-described problems and to provide a radiographic apparatus capable of obtaining a good radiation image by obtaining a two-dimensional image of an object by optical means and determining imaging conditions. is there.
[0026]
[Means for Solving the Problems]
To achieve the above object, a radiation imaging apparatus according to the present invention includes: a radiation emitting unit that emits radiation to a subject; a radiation image capturing unit that acquires a radiation image of the subject; a light source that emits light toward the subject; Subject information obtaining means for receiving a light beam from a light source to obtain a two-dimensional image of the subject by optical means, determining a body position or part of the subject based on the two-dimensional image, and performing radiation imaging based on the determination. And a photographing condition determining means for determining the photographing condition.
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
FIG. 1 shows a configuration diagram of a radiation imaging apparatus according to a first reference example. In front of a radiation irradiating unit 10 which is a radiation source for generating radiation, a radiation image for capturing a radiation image of the subject S via the subject S is shown. An imaging unit 11 is arranged, and an automatic distance measuring unit 12 that measures the distance from the irradiation unit 10 to the radiation image imaging unit 11 and / or the subject S in a non-contact manner is arranged near the irradiation unit 10. .
[0030]
The output of the imaging condition setting means 13 for controlling the radiation irradiation by the operator setting the imaging conditions such as the tube voltage, the tube current and the irradiation time is connected to the radiation irradiating means 10 and the output of the radiation image photographing means 11 is It is connected to the photographing condition setting means 13. The output of the automatic distance measuring means 12 is connected to distance information presenting means 14 for presenting distance information.
[0031]
The subject S, which is a patient, is located in front of the radiation imaging unit 11, and the operator sets various imaging conditions by using the imaging condition input unit 13. The radiation emitted from the radiation irradiating unit 10 passes through the subject S and reaches the radiation image capturing unit 11, where a radiation image of the subject S is captured. At this time, the distance from the radiation irradiating unit 10 to the radiation image capturing unit 11 and / or the subject S is measured in a non-contact manner by the automatic distance measuring unit 12 and presented to the distance information presenting unit 14.
[0032]
FIG. 2 is an explanatory view of the distance measurement by the automatic distance measuring means 12. The automatic distance measuring means 12 narrows down the light from the light source 15 such as an LED or an LD and the light beam from the light source 15 to a light spot P on the observation surface. It comprises a projection optical system 16 to be formed, a position detecting element 17 such as a CCD or PSD, and an imaging optical system 18 for forming a light spot image P ′ on the position detecting element 17.
[0033]
The light beam emitted from the light source 15 is narrowed down by the projection optical system 16 to a small light beam, and a small light spot P is formed on the observation surface. This light spot P is formed on the position detecting element 17 by the image forming optical system 18 to form a light spot image P ′. The relative distance Z between the light spot image P 'on the observation surface and the automatic distance measuring means 12 can be calculated from the coordinates of the light spot image P' on the position detecting element 17.
[0034]
In FIG. 2, the principal point of the imaging optical system 18 is defined as the origin O, the imaging surface of the position detecting element 17 is arranged at the position of Z = −d, and the principal point of the projection optical system 16 is located at the position of X = L. It is assumed that they are arranged. When the light spot image P ′ formed on the observation surface by the light beam irradiated in the φ direction with respect to the origin O is observed in the θ direction from the origin O, the relative distance D from the light spot image P ′ becomes It is obtained by the formula.
D = (L × tanθ × tanφ) / (tanθ + tanφ)
[0035]
However, if the coordinate of the light spot image P ′ on the position detecting element 17 is x, the angle θ is obtained by the following equation.
θ = tan-1 (x / d)
[0036]
The distance from the radiation irradiating unit 10 to the radiation image capturing unit 11 is obtained by projecting a light spot P on the front surface of the radiation image capturing unit 11, for example, on a breast contact surface, and obtaining the relative distance D from the above equation. The distance to S is obtained as the relative distance D from the above equation by projecting the light spot P on the surface of the subject S.
[0037]
FIG. 3 is a cross-sectional view showing a case where an X-ray film changer 20 is used as the radiation image photographing means 11, and a pressure plate 22a having two intensifying screens 21a and 21b adhered to the side where radiation X is incident. A film F is sandwiched between the front intensifying screen 21a and the rear intensifying screen 21b at the time of photographing, and the film F is held in close contact with the front pressure plate 22a and the rear pressure plate 22b. .
[0038]
Behind this, a radiation intensity detecting means 23 for detecting the intensity of the radiation X transmitted through the film F and a vacuum pump 24 are arranged, and further behind this, a supply magazine 25a for storing the unphotographed film F, The receiving magazine 25b for storing the used film F 'is arranged. Above, a pair of rollers 26a, 26b, 26c and a pair of rollers 26a, 26b, 26c for transporting the unphotographed film F from the supply magazine 25a to the photography position and transporting the captured film F 'to the receiving magazine 25b. Is disposed.
[0039]
When photographing is performed by the film changer 20 having the above-described configuration, first, the motor 27 drives the roller pair 26a, 26b to take out one film F from the unphotographed film storage supply magazine 25a, and perform rear sensitization. The paper 21b is fed to the front surface of the rear pressure plate 22b on which the paper 21b is stuck. Then, the rear pressure plate 22b is driven in the direction of arrow A by a rear pressure plate drive mechanism (not shown), and the film F is pressed against the front intensifying screen 21a attached to the front pressure plate 22a, and the vacuum pump 24 is operated. As a result, a vacuum contact is made between the front and rear intensifying screens 21a and 21b. After the film F is completely brought into contact with the front and rear intensifying screens 21a and 21b and becomes ready for photographing, radiation is irradiated from the radiation irradiating means 10 by an operation of the operator, and a radiation image of the radiation transmitted through the subject S is formed. Be photographed.
[0040]
Further, in the radiation image photographing means 11, the radiation transmitted through the subject S is incident on the radiation intensity detecting means 23, and the radiation intensity is detected. This radiation intensity information is set in a lookup table creating means described later, Used to create uptables.
[0041]
FIG. 4 is a cross-sectional view of a radiation image capturing means 11 using a stimulable phosphor sheet. In this radiation image capturing apparatus, radiation image information is stored and recorded in a stimulable phosphor sheet P, and the radiation image information is excited. A radiation image information recording / reading device 30 is used for irradiating light, detecting stimulating light in accordance with the stored and recorded image information, reading the image information, converting this optical signal into an electric signal, and reproducing the electric signal. ing.
[0042]
In the radiation image information recording and reading apparatus 30, endless belts 31a, 31b, 31c, and 31d for transporting the stimulable phosphor sheet P are arranged on four sides of a rectangular parallelepiped. Reference numeral 31d is connected to a transmission mechanism (not shown) such as a chain or gear and a motor 32 serving as a drive source. In the vicinity of the endless belt 31b, there is disposed a reading means 35 composed of a laser light source 33 and a photomultiplier 34 for reading radiation information accumulated and recorded on the stimulable phosphor sheet P. In the vicinity of the endless belt 31d, a reading means 35 is provided. An erasing means 37 which comprises an erasing light source 36 such as a lamp and emits residual energy of the stimulable phosphor sheet P is arranged.
[0043]
First, after the residual energy is released by the erasing light emitted from the erasing light source 36 of the erasing means 37 in the endless belt 31d, the stimulable phosphor sheet P drives the motor 32 by the control means (not shown) to control the transmission mechanism. The endless belts 31a to 31d are driven via the belt, and the stimulable phosphor sheet P is transported to the radiation incident position. The stimulable phosphor sheet P irradiated with the radiation X on the endless belt 31a moves to the endless belt 31b on which the reading unit 35 is disposed, and the stimulable phosphor sheet P is irradiated with laser light from the laser light source 33. Then, photostimulable emission light having an intensity corresponding to the radiation image information of the photostimulable phosphor sheet P is received by the photomultiplier 34. As a result, the radiation image information accumulated and recorded on the stimulable phosphor sheet P is read photoelectrically, and this radiation image information is transferred to a look-up table creating means described later and used for creating a look-up table. Are also transferred to an image processing means (not shown).
[0044]
FIG. 5 shows a cross-sectional view of the radiation image capturing means 11 using a photodetector array. A scintillator 40 is arranged on the side where the radiation X is incident, and a photodetector array 41 is arranged adjacent to the scintillator 40. . The output of the drive circuit 42 is connected to the photodetector array 41.
[0045]
When the radiation X is incident, the base substance of the phosphor is excited by the high-energy X-rays in the scintillator 40, and the fluorescence in the visible region is obtained by the binding energy at the time of recombination. In addition, this fluorescence is CaWO _Four And CdWO _Four And a luminescent center substance activated in the host such as CsI: Tl or ZnS: Ag. Then, the drive circuit 42 drives the photodetector array 41, converts photons into electric signals, and reads out electric signals from each pixel. The radiation image information obtained by the drive circuit 42 is transferred to a look-up table creating means described later and used for creating a look-up table. The radiation image information is also transferred to an image processing unit (not shown).
[0046]
FIG. 6 shows a configuration diagram of an equivalent circuit of the photodetection array 41. Here, a two-dimensional amorphous silicon sensor is used as a detection element. For example, a solid-state imaging element such as another charge-coupled element or a photomultiplier tube is used. The function and configuration of the A / D conversion unit are the same even if a simple element is used.
[0047]
One element of the photodetection array 41 is composed of a photodetection section 50 and a switching TFT 51 for controlling charge accumulation and reading, and is generally composed of amorphous silicon (αSi) disposed on a glass substrate. . The capacitor 52 in the light detection unit 50 may be simply a photodiode having a parasitic capacitance, or may be a photodetector including the photodiode 53 and an additional capacitor 52 for improving the dynamic range of the detector in parallel.
[0048]
The anode A of the photodiode 53 is connected to a bias line Lb, which is a common electrode, and the cathode K is connected to a controllable switching TFT 51 for reading out the charge stored in the capacitor 52. The switching TFT 51 is a thin film transistor connected between the cathode K of the photodiode 53 and the charge reading amplifier 54, and a capacitance element 55 and a reset switching element 56 are connected in parallel between the switching TFT 51 and the amplifier 54. ing.
[0049]
After the switching element for resetting 56 is operated by the switching TFT 51 and the signal charge to reset the capacitor 52, radiation corresponding to the radiation dose is generated in the photodiode 53 by radiation emission and stored in the capacitor 52. . Thereafter, the reset switching element 56 is operated again by the switching TFT 51 and the signal charge, whereby the charge is transferred to the capacitance element 55, and the amount accumulated by the photodiode 53 is read out by the amplifier 54 as a potential signal, and A / D conversion is performed to detect the amount of incident radiation.
[0050]
FIG. 7 shows a configuration diagram of the radiation imaging apparatus of the second reference example. A subject thickness calculating means 60 is connected between the automatic distance measuring means 12 and the distance information presenting means 14 in FIG. Calculates the body thickness of the subject S based on the distance from the radiation irradiating means 10 measured by the automatic distance measuring means 12 to the radiation image capturing means 11 and / or the subject S. Others are the same as the first reference example.
[0051]
The body thickness of the subject S is determined by projecting a light spot on the front surface of the radiographic image capturing means 11, for example, a breast contact surface, the relative distance between the radiation image capturing means 11 and the automatic distance measuring means 12, and projecting the light spot on the subject S. From the relative distance between the subject S and the automatic distance measuring means 12 obtained as described above. The distance information presenting means 14 presents the distance information obtained by the automatic distance measuring means 12 and / or the body thickness information obtained by the subject thickness calculating means 60.
[0052]
In the above-described reference example, the light spot is projected on the subject S and the distance to one point is calculated, but the laser light emitted from the light source 61 is used by the rotating mirror 62 as shown in FIG. By scanning the subject S with a light spot, the body thickness of the light-cut surface of the subject S can be measured. Also, as shown in FIG. 9, even if the laser light emitted from the light source 61 is spread out like a single band using the cylindrical lens 63 and projected onto the subject S, the thickness of the light-cut surface of the subject S can be reduced. Can also be measured. Similarly, as shown in FIG. 10, the laser beam emitted from the light source 61 can be reflected by the cylindrical mirror 64 to measure the body thickness of the light-cut surface of the subject.
[0053]
FIG. 11 shows a configuration diagram of the radiation imaging apparatus of the third reference example. The radiation image imaging means 11, the imaging condition input means 13, and the automatic distance measurement means 12 are provided to a lookup table creation means 65 for creating a lookup table. It is connected. In the following, description of other parts similar to those of the first and second reference examples will be omitted.
[0054]
FIG. 12 is a graph diagram showing a look-up table showing the relationship of the mAs value (tube current × irradiation time) with respect to the chest thickness of the subject who is the subject S. For a tube voltage of 100 and 120 kVp, a chest thickness of 17, The mAs value when the intensity information or the radiation image information of the radiation transmitted through the subject of 18, 19, 20, 21, 22, 23 cm outputs a certain value, is plotted, and an exponential function or a quadratic function is used. Approximation.
[0055]
Here, an example is shown in which the relationship between the chest thickness and the mAs value is obtained for seven subjects with different chest thicknesses, but the relationship between the chest thickness and the mAs value is obtained for a larger number of subjects. By averaging, a more accurate look-up table can be created. The creation of the look-up table may be performed using a phantom made of a substance having the same transmittance as that of the human body without actually using the data of the subject.
[0056]
The look-up table includes, besides the tube voltage, chest thickness, and mAs value, the photographing distance, photographing region, photographing position, body thickness of the subject S, intensifying screen type, film type, scattered radiation removing filter type, and additional filter. The imaging conditions such as the type can be stored as information. For example, an approximate function expression representing the relationship between the chest thickness and the mAs value for each tube voltage, and all or a part of the numerical values obtained from the approximate function expression are stored in a memory or The information may be stored in a recording medium such as an HD.
[0057]
FIG. 13 is a configuration diagram of a radiation imaging apparatus according to a fourth reference example, in which an automatic imaging condition determination unit 66 is connected to the radiation irradiation unit 10, the radiation image imaging unit 11, the imaging condition input unit 13, and the subject thickness calculation unit 60, respectively. Have been. In the following, description of other parts similar to those of the first, second, and third reference examples will be omitted.
[0058]
In order for the photographing condition automatic determining means 66 to determine the photographing conditions using, for example, the look-up table shown in FIG. 12, the operator first sets the tube voltage and the tube current with the photographing condition input means 13 and In the irradiation time determination mode in which the automatic determination means 66 determines the irradiation time, for example, the tube current set by the imaging condition input means 13 is A (mA), the tube voltage is 100 (kVp), When the examiner's chest thickness is measured to be 21.5 (cm), the look-up table indicates that the mAs value should be set to 2.9, and the irradiation time T (second) is 2 .9 / A.
[0059]
Next, in the tube current determination mode in which the operator sets the tube voltage and the irradiation time by the imaging condition input unit 13 and the imaging condition automatic determination unit 66 determines the tube current, for example, the setting is performed by the imaging condition input unit 13. If the irradiation time is T (seconds), the tube voltage is 100 (kVp), and the subject's chest thickness is measured to be 21.5 (cm) by the subject thickness calculating means 60, the tube current (mA) becomes It can be determined by 2.9 / T.
[0060]
Further, in the tube power determination mode in which the operator sets the tube current and the irradiation time with the imaging condition input unit 13 and the imaging condition automatic determination unit 66 determines the tube voltage, for example, the tube set by the imaging condition input unit 13 When the current is 40 (mA), the irradiation time is 0.05 (second), that is, the mAs value is 2, and the subject thickness calculating means 60 measures the subject's chest thickness to 21.5 (cm), Referring to the look-up table, the tube voltage is 100 + Δα / (α + β) from the ratio α to β at 100 (kVp) and 120 (kVp) of point c where 2 mA and chest thickness 21.5 (cm) intersect. ｝ × (120-100) (kVp) can be determined. It is to be noted that a more accurate tube voltage can be determined by holding a lookup table for more tube voltages, for example, every 5 (kVp).
[0061]
FIG. 14 is a block diagram of a radiation imaging apparatus according to a fifth reference example. In order to capture a radiation image transmitted through the subject S, a stimulable phosphor is provided in front of a radiation irradiation unit 70 for generating radiation. A radiographic image capturing apparatus 71 using a light receiving array or the like on the image receiving surface is arranged, and a visible image capturing means 72 for capturing a visible image of the subject S is disposed near the radiation irradiating means 70.
[0062]
The output of the radiation image photographing means 71 is connected to an image processing means 73, and the image processing means 73 has image processing functions such as histogram analysis, gradation correction, and frequency emphasis of the image information obtained by the radiation image photographing means 71. The output of the visible image photographing means 72 is connected to the position correspondence means 74, and the output of the radiation image photographing means 71 is also connected to the position correspondence means 74. Further, the output of the visible image photographing means 72 is connected to the image processing condition determining means 75, and the output of the image processing condition determining means 75 is connected to the image processing means 73. Thus, the image processing condition determining means 75 has a function of determining the image processing conditions of the image processing means 73 based on the visible image information obtained by the visible image photographing means 72.
[0063]
FIG. 15 shows a configuration diagram of the visible image photographing means 72. The visible image photographing means 72 has an imaging lens 76, a folding mirror 77 having high transparency to radiation, a CCD camera 78, and radiation irradiation of an arbitrary size. The CCD camera 78 has, for example, a sampling number of 512 × 512, a quantization number of 8 bits, and a structure capable of obtaining a black-and-white and a visible image that can be handled by a general-purpose image processing apparatus. Have been. Although the optical axis of radiation and the optical axis of the visible image capturing means 72 are shown on the same axis, the same optical axis may not be used as long as the positional relationship is calibrated.
[0064]
With such a configuration, radiation is emitted from the radiation irradiating unit 70 to the subject S, and the radiation transmitted through the subject S reaches the radiation image capturing unit 71, where a radiation image is captured. Then, image processing is performed by the image processing means 73, and radiation image information of the subject S having the imaging region B as shown in FIG. 16 is obtained. Further, a visible image of the imaging area C as shown in FIG. 17 is captured by the CCD camera 78 of the visible image capturing means 72.
[0065]
Here, the imaging area B of the radiation image imaging means 71 and the imaging area C of the CCD camera 78 are made to correspond to each other with reference to the mark M on the radiation incident side of the radiation image imaging means 71, and are obtained by the visible image imaging means 71. The relationship between the coordinate positions of the visible image information and the image information obtained by the radiation image capturing unit 71 can be associated by the position association unit 74. Note that the visible information and the radiation information do not correspond one-to-one. For example, when the visible information is composed of an image of 512 × 512 pixels and the radiation information is composed of 1024 × 1024 pixels, one pixel of the visible information is the radiation information. Correspond to the four pixels. Further, since the visible image information is imaged by a lens, the peripheral portion of the image may be distorted. However, it is preferable that the distortion is corrected to correspond to the radiation information.
[0066]
First, when the image processing condition determining means 75 includes an irradiation field determining means for determining an irradiation field, the movable irradiation area 79 of the radiation irradiation means 70 can adjust the radiation irradiation field to an arbitrary size. Therefore, as shown in FIG. 18, the radiation image capturing area B is divided into an irradiation area B1 and a non-irradiation area B2 masked by the movable stop 24. Further, as shown in FIG. 19, the visible image information photographed by the visible image photographing means 72 is divided into an irradiation field region C1 and a non-irradiation field region C2 by binarization processing. Since these areas C1 and C2 can be associated with the respective areas B1 and B2 of the radiation image information by the position correspondence means 74, the image processing means 73 performs image processing on the irradiation field area B1 of the radiation image information.
[0067]
Next, in a case where the image processing condition determining means 75 includes a posture determining means for determining the posture of the subject S between the front photographing and the side photographing, as shown in FIGS. The front photographed image D and the side photographed image E of the visible image information are divided into subject areas D1 and E1 and non-subject areas D2 and E2 by binarization processing. For example, the front photographing D or the side photographing is performed based on the width (length of both arrows) of the subject regions D1 and E1 and / or the symmetry with respect to the center of the image (dotted line) and / or the presence or absence of an arm. The position of E is determined. Then, the determined body position information is sent to the image processing means 73, and image processing suitable for each body position is performed on the subject regions D1 and E1.
[0068]
Finally, when the image processing condition determining means 75 includes an imaging part determining means for determining the imaging part of the subject S, the visible image information obtained by the visible image A binarized image F as shown is created. Comparison of this binarized image F with a prepared head template G1, chest template G2, and hand template G3, for example, the error between the binarized image F and each of the region templates G1, G2, G3 is determined for each pixel. Then, the sum of the errors is compared with a predetermined threshold value, and a part to be photographed is determined such that a part smaller than the threshold value is determined as a part at that time. Then, the part information is sent to the image processing means 73, and the subject area of the radiation image information is subjected to image processing suitable for each part. Here, only the head, chest, and hands have been described, but the abdomen, feet, and the like can be also discriminated in a similar manner.
[0069]
FIG. 23 shows a configuration diagram of the radiation imaging apparatus according to the first embodiment. A folding mirror 81, a movable diaphragm 82, a subject S, and a radiation imaging unit 83 are sequentially arranged on the front surface of a radiation irradiating means 80. The light source 84 is arranged in the direction of incidence of. The radiation imaging unit 83 includes a grid 85, a photo timer light receiving unit 86, and a radiation image capturing means 87. The difference between this embodiment and the second conventional example shown in FIG. In addition, a subject information obtaining means 88 having a visible light sensor for obtaining two-dimensional information of the subject S is arranged.
[0070]
Thus, the provision of the subject information obtaining means 88 enables one-to-one correspondence with the radiation image capturing means 87, so that the correspondence between the radiation image of the subject S and the two-dimensional information is facilitated. It is particularly advantageous when the portable radiation imaging unit 83 is formed. The wavelength range of light actually used is not limited to visible light as long as it is harmless to the human body.
[0071]
24 to 28 show perspective views of the subject information obtaining means 88. FIG. 24 shows the subject information obtaining means 88 composed of a plurality of photoelectric conversion elements 89, which are semiconductor elements such as CdTe. An object receiving cover 90 that is transparent to light is arranged on the front surface of the object 88 so that the object S does not directly touch the object information acquisition unit 88. FIG. 25 shows a subject information acquisition unit 88 comprising a light detection array 91 which is a photoelectric conversion surface sensor made of amorphous silicon (αSi) or the like. FIG. 26 shows a subject information acquisition unit 88 composed of a line sensor 92 which is a linear photoelectric conversion element and a driving unit 93. By driving the line sensor 92 in the direction orthogonal to the scanning, the subject S is Dimension information is obtained. In this case, the driving means 93 is composed of a guide driving screw and a driving motor, and evacuates the line sensor 92 to the outside of the radiation irradiation area during radiation irradiation.
[0072]
Further, FIG. 27 shows subject information acquiring means 88 comprising a light transmitting means 94 and a line sensor 95 which is a linear photoelectric conversion element. In this case, a line sensor 95 is attached to an end face of the light transmitting means 94. , The line sensor 95 is arranged so as to efficiently receive the light from the light transmitting means 94. The light transmitting means 94 is formed by laminating rods 96 made of a material having a uniform radiation absorption such as acrylic resin by the number corresponding to the number of pixels of the line sensor 95. Are different from each other, so that two-dimensional information of the subject S can be obtained by the light incident pattern.
[0073]
FIG. 28 is a perspective view of the light transmitting means 94. The rod 96 is divided into two parts so that light is not transmitted on the way, and each rod 96 is provided with an opening 97 through which light is incident. A line sensor 97, which is a photoelectric conversion element, is attached, so that twice the amount of information can be obtained.
[0074]
Such subject information acquiring means 88 can obtain two-dimensional information of the subject S based on the silhouette image of the subject S or the presence / absence of light due to light being blocked by the subject S, as shown in FIG. By turning on the light source 84 that emits visible light or infrared light, more clear two-dimensional information of the subject S can be obtained. If ambient light correction means for correcting the influence of ambient light or room light other than the illumination light of the light source 84 is used, the ambient light information obtained by the subject information acquisition means 88 when the light source 84 is not turned on can be used as the light source. By subtracting from the incident light information obtained by the subject information obtaining means 88 when the light 84 is turned on, more clear two-dimensional information of the subject S can be obtained.
[0075]
As described above, since the subject information acquiring means 88 uses visible light or infrared light, it is harmless to the human body, and visible information acquired by the subject information acquiring means 88, for example, a silhouette image is displayed on a television monitor. Thus, remote operation is also possible.
[0076]
FIG. 29 is a configuration diagram of the radiation imaging apparatus according to the second embodiment. In the radiation imaging apparatus according to the first embodiment, imaging condition determination is performed based on the two-dimensional information of the subject S obtained by the subject information acquisition unit 88. , A photographing condition determining means 99 for performing the above operation is added.
[0077]
The photographing condition determining means 99 determines photographing conditions in the following order based on the two-dimensional information of the subject S.
[0078]
(1) Judgment of the body position of the front or side of the subject S is performed to determine the radiation quality, that is, the radiation tube voltage.
(2) The site of the subject S is determined to determine the radiation quality.
(3) The irradiation range is determined, and the stop range of the movable radiation stop 82 is determined.
(4) The photographing range of the subject S is determined.
(5) Determine the effective area of the photo timer light receiving unit 86.
(6) Determine the gain switching of the photo timer.
(7) Determine the reading range when reading out radiation image information from the radiation image capturing means 87.
(8) Processing parameters for performing image processing on the radiation image information read from the radiation image capturing means 87 are determined.
(9) Determine the size of the film for outputting the radiation image information with a laser printer or the like.
[0079]
As described above, since the imaging condition determination unit 99 uses the two-dimensional information of the subject S, there is no influence of blur due to scattered radiation of the radiation image information, and processing such as contour extraction is easy, and more appropriate imaging is performed. A condition decision can be made.
[0080]
In the first and second embodiments described above, it is necessary to set the radiation quality and dose of the radiation irradiating means 80, set the movable aperture 82, and set image processing parameters of a radiation image such as extraction of the contour of the subject S. The two-dimensional information of the subject S can be easily acquired. Based on the acquired two-dimensional information of the subject S, the imaging conditions such as the setting of the radiation quality and dose of the radiation irradiating unit 80 and the setting of the movable aperture 82 are set. The decision can be made accurately and easily.
[0081]
FIG. 30 shows a configuration diagram of the third embodiment. A folding mirror 101 having a high transmittance characteristic for X-rays, a movable diaphragm 102, a subject S, Radiation imaging means 104 having a phototimer light receiving unit 103 are sequentially arranged, and an imaging lens 105 and a CCD camera 106 are arranged in the reflection direction of the folding mirror 101. This radiation imaging apparatus can automatically set a radiation irradiation field to optimal conditions when imaging a human chest as an object S and acquiring medically useful object information from the captured image.
[0082]
Radiation is irradiated from the X-ray tube 100 toward the subject S, and a radiation intensity distribution transmitted through the subject S is imaged by the radiation imaging unit 104. The photo-timer light receiving unit 103 performs radiation input suitable for the sensitivity characteristics of the imaging device, protects the chest from being exposed abnormally, and outputs an irradiation stop signal to the control device of the X-ray tube 100 when a radiation amount suitable for imaging is detected. Send Further, the movable stop 102 blocks radiation irradiation to an area that is invalid in chest radiography, thereby avoiding malfunction of the phototimer light receiving unit 103 and radiation unnecessary for radiography. On the other hand, the CCD camera 106 observes a visible subject image via the imaging lens 105 and the folding mirror 101 in order to obtain subject position information without performing radiation irradiation.
[0083]
In order to determine the effective irradiation field and automatically set the optimum condition of the actual irradiation field in the radiography, ie, the main radiography, the subject image is taken by the CCD camera 106 immediately before the main radiography, and the subject image S as shown in FIG. 'To obtain subject position information. Here, inside the photographing region H1 of the CCD camera 106, there is a main photographing receiving region H2 when the movable aperture 102 is opened, and a background image T 'exists behind the subject image S'. The background image T ′ has a different color tone or the like from the subject image S ′ in accordance with the light receiving characteristics of the CCD camera 106 so that the subject image S ′ has a high discriminability from the subject image S ′ and enables accurate and easy extraction of the subject region. Is preferred. Then, the subject area S1 is extracted as shown in FIG. 32 (a) by subject area extracting means for binarizing the subject image S 'and the background image T' in the main shooting image receiving area H2 from the subject position information by color tone or the like. I do.
[0084]
Next, the optimum irradiation field L in the main imaging is determined using the optimum imaging condition determining means, in this embodiment, the appropriate irradiation field determining means in the chest imaging. By vertically integrating the subject area S1 extracted in the frontal shooting, a histogram is created as shown in (b), and the arm area with a small distribution in the vertical direction is identified and identified as the chest. This procedure is omitted for the subject S having no arms as in the above. Then, the optimum target irradiation field L is determined according to the movable diaphragm edges N1 and N2 in (a) according to the width of the remaining chest.
[0085]
Finally, the movable aperture 102 is automatically set, and the preparation for the main photographing is completed. Further, when the photographer does not want the automatic setting, the optimum radiation irradiation field L may be compared with the currently set irradiation state to judge the inappropriateness as a threshold, and the result may be displayed as a warning.
[0086]
In the present embodiment, the CCD camera 106 and the imaging lens 105 are used as the subject position information acquisition means, but a two-dimensional image pickup tube other than the CCD camera 106 is also possible. Although the optical axis of the radiation and the optical axis of the subject position information acquisition means are arranged on the same axis, the same optical axis does not have to be used as long as the main imaging position is calibrated. Further, as the object position information acquiring means, a configuration for obtaining an intensity distribution on the photographing surface by laser scanning and an optical sensor for receiving the reflected light, or an object by an existing illumination and an optical fiber array and an optical sensor arranged in front of the photographing surface. A configuration that receives the projection distribution may be used. In this embodiment, the movable stop 102 is movable only in the horizontal direction. However, the movable stop 102 may be disposed in the vertical direction to protect the head and lower abdomen.
[0087]
As described above, in the third embodiment, the subject area S1 is easily and accurately extracted immediately before the actual photographing, and the optimal photographing conditions in the actual photographing are automatically set and presented. It is possible to prevent shooting errors. In addition, the subject area S1 is extracted immediately before the main shooting, the irradiation field optimal for the main shooting can be automatically set and presented to the photographer, and the effective area of the phototimer light receiving unit 103 is determined from the subject area S1. be able to. In addition, by determining the body position of the subject S in the front photographing and the side photographing from the subject area S1, the gain of the photo timer according to the body position can be determined. Furthermore, by comparing the subject region S1 with a reference table prepared in advance, the imaging region can be determined, and the tube voltage according to the imaging region can be automatically set and presented to the photographer, so that radiation exposure can be performed. It is possible to prevent a main shooting error due to a poor quantity.
[0088]
Incidentally, in order to prevent malfunction due to the influence of the through-radiation, a radiation imaging apparatus that automatically sets a phototimer light receiving area to an optimum condition is also conceivable. In this case, the subject position information acquiring means and the subject area extracting means of the third embodiment are used to extract the subject's chest contour. The effective effective area of the photo timer in the actual shooting is determined and automatically set by using an optimal condition determining means such as not using a part other than the subject area in the light receiving area of the photo timer light receiving section 103 or performing weighting. .
[0089]
In addition, the switching of the phototimer gain can be automatically set in order to correct the difference in scattered radiation between the front and side images. The subject position information acquiring means and the subject area extracting means of the third embodiment are used to extract the subject's chest contour. The width and the symmetry of the subject S and the presence / absence of an arm are determined by thresholds to determine whether the photographing is frontal or lateral, and the phototimer gain is switched to an existing value for frontal photographing or side photographing. In order to prevent an erroneous determination, the determination result may be merely presented to the photographer using the display means.
[0090]
Further, automatic setting of the radiation quality for optimizing the subject contrast of the radiation transmission image depending on the imaging region can also be performed. In this case, the radiation quality adjustment is substantially determined by the tube voltage of the X-ray tube 100. Using the subject position information acquiring means and the subject area extracting means of the third embodiment, a subject area is extracted, and the extracted subject areas are prepared in advance, and the head, chest, abdomen, hands, and feet are referred to as photographed parts. The object part is determined by collating with the table and performing pattern matching. For the determined part, the recommended tube voltage reference table prepared for each part prepared in advance is checked, and the tube voltage for the main photographing is automatically set or displayed as the recommended tube voltage.
[0091]
【The invention's effect】
As described above, according to the radiation imaging apparatus according to the present invention, since a two-dimensional image of a subject is obtained by optical means and imaging conditions are determined and imaging is performed, a good radiation image matching the imaging purpose is obtained. be able to.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a first reference example.
FIG. 2 is an explanatory diagram of automatic distance measurement according to a first reference example.
FIG. 3 is a cross-sectional view of a radiation image capturing unit using a silver halide film according to a first reference example.
FIG. 4 is a cross-sectional view of a radiation image capturing unit using a stimulable phosphor according to a first reference example.
FIG. 5 is a cross-sectional view of a radiation image capturing unit using a light detection array according to the first reference example.
FIG. 6 is a configuration diagram of an electric circuit of a light detection unit according to a first reference example.
FIG. 7 is a configuration diagram of a second reference example.
FIG. 8 is an explanatory diagram of body thickness measurement using a rotating mirror according to a second reference example.
FIG. 9 is an explanatory diagram of body thickness measurement using a cylindrical lens according to a second reference example.
FIG. 10 is an explanatory diagram of body thickness measurement using a cylindrical mirror according to a second reference example.
FIG. 11 is a configuration diagram of a third reference example.
FIG. 12 is a graph showing the relationship between the chest thickness and the mAs value in the third reference example.
FIG. 13 is a configuration diagram of a fourth reference example.
FIG. 14 is a configuration diagram of a fifth reference example.
FIG. 15 is a configuration diagram of a visible image photographing unit according to a fifth reference example.
FIG. 16 is an explanatory diagram of a radiographic image capturing area according to a fifth reference example.
FIG. 17 is an explanatory diagram of a CCD camera imaging area according to a fifth reference example;
FIG. 18 is an explanatory diagram of a radiographic image capturing area according to a fifth reference example.
FIG. 19 is an explanatory diagram of a CCD camera imaging area according to a fifth reference example;
FIG. 20 is a front view of body position determination according to a fifth reference example;
FIG. 21 is a side view of the fifth reference example.
FIG. 22 is an explanatory diagram of a part determination according to a fifth reference example;
FIG. 23 is a configuration diagram of the first embodiment.
FIG. 24 is a perspective view of a radiation imaging unit using a plurality of photoelectric conversion elements according to the first embodiment.
FIG. 25 is a perspective view of a radiation imaging unit using a light detection array according to the first embodiment.
FIG. 26 is a perspective view of a radiation imaging unit including a line sensor and a driving unit according to the first embodiment.
FIG. 27 is a perspective view of a radiation imaging unit including a light transmission unit and a line sensor according to the first embodiment.
FIG. 28 is a perspective view of the light transmitting means of the first embodiment.
FIG. 29 is a configuration diagram of a second embodiment.
FIG. 30 is a configuration diagram of a third embodiment.
FIG. 31 is an explanatory diagram of subject position information according to the third embodiment.
FIG. 32 is an explanatory diagram of a subject area information processing method according to the third embodiment.
FIG. 33 is a configuration diagram of a first conventional example.
FIG. 34 is a configuration diagram of a second conventional example.
[Explanation of symbols]
10, 70, 80, 100 radiation irradiation means
11, 71, 81, 104 radiation image capturing means
12 Automatic distance measuring means
13 Shooting condition input means
14 Distance information presentation means
40 scintillator
41 Photodetection Array
60 means for calculating subject thickness
65 Look-up table creation means
66, 99 shooting condition determining means
72 Visible image capturing means
73 Image processing means
74 Position correspondence means
75 Image processing condition determining means
78, 100 CCD camera
79, 82, 102 Movable diaphragm
83 Radiation imaging unit
86, 103 Phototimer light receiving unit
88 Subject information acquisition means

Claims (14)

Radiation emitting means for emitting radiation to a subject, radiation image capturing means for acquiring a radiation image of the subject, a light source emitting light toward the subject, and two-dimensional imaging of the subject by optical means for receiving a light beam from the light source Subject information obtaining means for obtaining an image; and imaging condition determination means for determining a body position or a part of the subject based on the two-dimensional image and determining imaging conditions for radiation imaging based on the determination. Radiation imaging device. The apparatus according to claim 1, further comprising an image processing unit configured to perform image processing on the radiation image acquired by the radiation image capturing unit, wherein the imaging condition determination unit determines an image processing parameter of the image processing unit based on the determination. 2. The radiation imaging apparatus according to 1. The subject information obtaining means radiographic apparatus according to claim 1 or 2, characterized in that it comprises a plurality of light detecting elements. The subject information obtaining means radiographic apparatus according to claim 1 or 2, characterized in that it comprises a photodetector array. The radiographic apparatus according to claim 1 or 2, wherein the object information acquisition means is characterized in that it comprises a line sensor. The radiation imaging apparatus according to claim 5 , further comprising a driving unit configured to drive the line sensor in a direction orthogonal to a scanning direction of the line sensor. The radiation imaging apparatus according to claim 5, wherein the line sensor is retracted from a radiation irradiation area when radiation is emitted. The subject information obtaining means, a plurality of the optical transmission means, the radiation imaging apparatus according to claim 1 or 2, characterized in that it comprises a line sensor disposed on the end face of the optical transmission means of the plurality of. 9. The radiation imaging apparatus according to claim 8 , wherein the light transmission unit is made of a material having a uniform radiation absorption rate. The radiation imaging apparatus according to claim 8, wherein the light transmission unit is made of an acrylic resin. The radiation imaging apparatus according to claim 1 , further comprising a correction unit configured to correct an influence of ambient light other than light emitted by the light source. The radiation imaging apparatus according to any one of claims 1 to 11 , wherein the subject information acquisition unit is arranged in front of the radiation image imaging unit. The radiation imaging apparatus according to claim 1 , wherein the imaging condition determination unit determines the quality of radiation generated by the radiation emission unit based on the determination. A phototimer for receiving the radiation emitted by the radiation emitting means at a phototimer light receiving unit and controlling the radiation emitting means based on the received radiation dose; and the imaging condition determining means sets the photo time based on the determination. The radiation imaging apparatus according to claim 1 , wherein a gain of the timer is determined.

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