JP3748113B2 - CT system - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a CT system having a radiotherapy planning function for planning a radiotherapy plan, and in particular, determines an irradiation range of radiation and collates with an irradiation result. Or The present invention relates to a CT system in which a transmission image is used for the purpose.
[0002]
[Prior art]
Conventionally, radiation therapy for irradiating a lesion such as cancer with radiation has been performed in clinical settings, and its effectiveness has been recognized.
[0003]
In general, a linear accelerator is used as a radiotherapy apparatus for performing this radiotherapy. This linear accelerator irradiates an affected part of a patient lying on a treatment table with radiation (X-rays) generated by applying an accelerated electron beam to a target or directly irradiates an accelerated electron beam Or To do.
[0004]
In order to treat using such a radiotherapy apparatus, various preparatory operations are required. The first step is to acquire an image of a diseased part using, for example, an X-ray CT scanner. In the second stage, the image is used to accurately grasp the position, size, shape, number, etc. of the affected area, and what isocenter position and dose distribution, irradiated particles (field of view, angle, number of gates, etc.) If you select, decide whether only the affected area can be irradiated with radiation accurately. Furthermore, in the third stage, the isocenter determined by the X-ray simulator, isocenter setting using the dose distribution and irradiation conditions, patient positioning by fluoroscopy, body surface marking (isocenter, irradiation field), and simulation by the determined irradiation method are performed. Is called.
[0005]
When the process up to the simulation is completed in this way, the treatment with the radiotherapy apparatus is usually performed after an appropriate period. Prior to this treatment, the radiation field is collated with the fluoroscopic image for collation, the patient is positioned by the isocenter mark among the body surface marks attached to the patient, and the irradiation range of the collimator is set by the radiation field mark. After this, actual radiation therapy is performed according to the determined irradiation method.
[0006]
In recent years, various approaches to cancer treatment have been made, and the significance of radiation therapy has been reviewed as radical treatment and palliative treatment. More accurate affected area positioning, more precise treatment planning, and more accurate treatment Is being demanded.
[0007]
Under such circumstances, when a treatment plan is made, generally, a scanogram of a subject and a reconstructed axial image are used. That is, the irradiation field for the lesion (target) is determined by a scanogram or an equivalent image, and the line cone is confirmed by an axial image.
[0008]
When an image of a diseased part is acquired by an X-ray CT scanner, a transmission image reconstructed from a CT image is often used as a reference image for determining an irradiation field. The transmission image is an image viewed from the therapeutic radiation source (that is, the line of sight spreads from one point), and three-dimensional voxel data is formed intermediately from a plurality of two-dimensional CT images (tomographic images). A transmission image is created from the dimensional voxel data. A CT image is used as the axial image.
[0009]
Conventionally, the length of an integration path for creating a transmission image extends over the entire subject (full thickness) in the line-of-sight direction, as shown in FIG.
[0010]
[Problems to be solved by the invention]
However, since the transmission image according to the above-described conventional method uses an integration path over the entire region (total thickness) in the line-of-sight direction of the subject, for example, integration paths P1 and P2 in FIG. The ratio of the bone B serving as a position determination mark to the body thickness may be low. In such a case, there is no significant difference between the integrated values of the path P1 that passes through the bone B and the path P2 that does not (see FIG. 23). reference). For this reason, the contrast of the bone B with respect to the background is low, and its position is difficult to identify, and it is difficult to use positional information such as bones and tracheal bifurcation points for identification of the transmission image and the patient site, and positioning accuracy Was low.
[0011]
The present invention has been made to improve the above-described problems related to conventional transmission images, and even if the proportion of the specific part such as bones or tracheal bifurcation points serving as landmarks in the body thickness is low, It is an object of the present invention to provide a CT system having a radiotherapy planning function capable of increasing the contrast on a transmission image and enabling highly accurate position identification.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, the present invention is configured as follows.
[0013]
According to claim 1 of the present invention, three-dimensional voxel data is created from a plurality of X-ray CT images of a subject, and a transmission image is created when the three-dimensional voxel data is seen through from a virtual position of a radiation source. In the CT system in which the transmission image is used for the radiotherapy planning of the subject, the non-linear conversion data in which the CT values of the plurality of X-ray CT images emphasize the bone of the subject in the transmission image By converting the plurality of X-ray CT images from the plurality of X-ray CT images while enhancing the contrast of the bone portion. Voxel data Three-dimensional data creation means for creating and the direction along the perspective Voxel data An integrated range setting means for setting an integrated range of CT values of the three-dimensional data, and the three-dimensional data generating means Voxel data In accordance with the integration range set by the integration range setting means to emphasize the contrast of the bone portion of the subject Voxel data And a transmission image generating means for generating the transmission image including
[0014]
According to a second aspect of the present invention, the apparatus further comprises three-dimensional data creation means for creating three-dimensional voxel data from a plurality of X-ray CT images of the subject, and the three-dimensional voxel data is used as a virtual position of a radiation source. In a CT system that creates a transmission image when seen through and uses this transmission image for planning radiotherapy of the subject, the direction along the direction of fluoroscopy Voxel data An integration range setting means for setting the integration range of the CT value, and according to the integration range set by the integration range setting means, Voxel data To enhance the contrast of the bone part of the subject. Voxel data And a transmission image generating means for generating the transmission image including
Furthermore, according to claim 3 of the present invention, the integrated range setting means includes, for example, a means for displaying a reference image related to the three-dimensional voxel data, and the bone portion in the fluoroscopic direction in the reference image. Means for superimposing and displaying a definable ROI on the reference image.
[0015]
[Action]
In the present invention, when generating third-order voxel data from a plurality of X-ray CT images, the CT values of the plurality of X-ray CT images are obtained by nonlinear conversion data in which bones are emphasized. Converted Create a transmission image from the 3D voxel data When seeing through The CT value integration range along the direction By ROI Limited Do . As a result, the bone part appearing in the transmission image has a much higher contrast than the conventional one even when the proportion of the body thickness is small, and it is easy to identify the position using the bone part. .
[0016]
【Example】
Hereinafter, an entire radiation therapy system including a radiation therapy planning apparatus according to an embodiment of the present invention will be described with reference to FIGS.
[0017]
This radiotherapy system, as shown in FIG. 1, a radiotherapy planning CT system 1 as a radiotherapy planning device for performing consistently from image acquisition to treatment planning and alignment (simulation) in radiotherapy, A radiotherapy apparatus 2 that performs radiotherapy according to the treatment plan data planned and simulated by the CT system 1 for radiotherapy planning, and automatically controls a collimator (described later) built in the radiotherapy apparatus 2; The CT system 1 for radiotherapy planning and the radiotherapy apparatus 2 are connected by a signal line 3 as a signal transmission line. In the middle of the signal line 3, a collation recording device 4 is inserted which allows the operator to finely adjust the opening of the collimator during actual radiotherapy. Furthermore, in the CT system 1 for radiation treatment planning, a treatment processing dedicated processing device 5 for performing specialized calculation processing such as radiation dose distribution calculation and a laser printer 6 for outputting plan data are transmitted via transmission lines 7 and 8. Each is connected.
[0018]
Among these components, the radiation treatment planning CT system 1 (hereinafter simply referred to as “CT system”) will be described first.
[0019]
The CT system 1 is configured by applying a normal X-ray CT scanner, and includes a gantry 11, a bed 12, and a control console 13 as shown in FIG. It is a device to do. A top plate 12a is disposed on the top surface of the bed 12 so as to be slidable in the longitudinal direction (Z-axis (body axis) direction), and the subject P is placed on the top surface of the top plate 12a. It is done. The top plate 12 a is inserted into the diagnostic opening OP of the gantry 11 so as to be able to advance and retract by driving a slide mechanism represented by the electric motor 13.
[0020]
The gantry 11 includes an X-ray tube 20 and an X-ray detector 21 that face each other with the subject P inserted in the opening OP (see FIG. 2). A weak current signal corresponding to the transmitted X-ray detected by the X-ray detector 21 is converted into a digital quantity by the data collection unit 22 as shown in FIG. In FIG. 2, the code | symbol 23 shows the collimator and filter in the gantry 11, and the code | symbol 24 has shown the X-ray fan.
[0021]
Further, three positioning laser projectors 27a, 27b, and 27c that are operated when marking the isocenter are disposed on the front side of the gantry 11, that is, inside the front cover 11a that is located on the bed 12 side.
[0022]
As shown in FIG. 2, the console 13 includes a main control unit 40 that controls the entire CT system, a bed control unit 41 and a gantry control unit 42 that operate in response to a command from the main control unit 40. They are connected to each other via a bus. The main controller 40 is also connected to an X-ray controller 43 outside the console, and is provided with a high voltage generator 44 that operates according to a drive signal from the X-ray controller 43. The high voltage generated by the high voltage generator 44 is supplied to the X-ray tube 20 and X-ray exposure is performed. Further, the console 13 receives an acquisition signal from the data acquisition unit 22 and reconstructs image data, an image reconstruction unit 45 that stores image data, an image memory 46 that stores image data, a display 47 that displays a reconstructed image, and an operator Are provided with input devices 48 for giving commands to the main control unit 40, respectively. Each control unit and the controllers 40 to 43 are equipped with a computer and operate based on a program stored in advance in the memory.
[0023]
The internal bus of the console 13 is further connected to a signal line extension board 13A, and a projector controller 49 for controlling the marker irradiation positions of the projectors 27a to 27c is connected to the extension board 13A via a signal line 50. The laser printer 6 and the verification recording device 4 are connected via signal lines 8 and 3.
[0024]
Next, the radiotherapy apparatus 2 will be described.
[0025]
The radiotherapy apparatus 2 (hereinafter simply referred to as “therapeutic apparatus”) treats using X-rays in this embodiment. As shown in FIG. 1, a treatment table 60 on which the subject P is placed, and the subject P A console 61 is provided with a gantry 61 that can rotate about the body axis (Z) direction as a rotation axis, and a gantry support body 62 that rotatably supports the gantry 61.
[0026]
The treatment table 60 includes a top plate 60a on the upper side thereof. Since the height of the treatment table 60 can be adjusted by an internal drive mechanism, the top plate 60a can be moved up and down (Y-axis direction). In addition, the treatment table 60 can move the top plate 60a in the longitudinal direction (Z direction) and the lateral direction (X direction) within a predetermined range by driving another internal drive mechanism, and further drive. By operating the mechanism, it is possible to rotate the top column support and the center of the isocenter. The operation of the treatment table 60 is necessary when positioning the subject P on the top plate 60a and performing radiation irradiation, and is controlled by a control signal from the console.
[0027]
On the other hand, the gantry 61 includes an irradiation head 61a that deflects accelerated electrons from the klystron and applies them to a target, and irradiates the subject P with an X-ray beam generated therefrom. In the irradiation head 61a, a multi-leaf collimator 65 that determines an irradiation field on the body surface of the subject P is installed between a target, that is, a radiation source and an irradiation port.
[0028]
Further, the gantry support 62 can be rotated clockwise or counterclockwise by the built-in drive mechanism. The operation of this drive mechanism is performed based on a control signal from a console (not shown). The console of the treatment device 2 includes a main control unit that manages the entire treatment device 2, a collimator control unit, and the like.
[0029]
Next, the operation of this embodiment will be described with reference to a flowchart.
[0030]
FIG. 3 shows the entire flow from the scan for acquiring the image of the treatment site to the treatment plan, and is a process performed mainly by the console 13 of the CT system 1.
[0031]
First, in step 101 of FIG. 3, it is confirmed that the positions of the projectors 27 a to 27 b are in the home position, and the process proceeds to processing for the treatment plan after step 102. First, in step 102, the main control unit 40 gives a helical scan command to the bed control unit 41, the gantry control unit 42, and the X-ray control unit 43 to execute a scan, and the collected data of the data collection unit 22 is collected. Based on the above, the image reconstruction unit 45 is instructed to perform image reconstruction. Thereby, CT image data of a three-dimensional region including the treatment site is obtained as a plurality of axial image data. Prior to this helical scan, a scanogram (perspective image) of the treatment site is taken.
[0032]
When it is determined in step 103 that the series of scans and the reconstruction thereof have been completed, the process proceeds to step 104 to determine whether or not dose distribution calculation is necessary. This dose distribution calculation is often performed in a confirming manner when the treatment site is a new location that is not clinically routine. Therefore, the main control unit 40 determines whether or not such calculation is instructed based on the operator command information from the input device 48. If YES, the main control unit 40 transfers the image data to the dedicated processing device 5 online, and determines the dose. Command distribution calculation. In this case, the dedicated processing device 5 performs the commanded dose distribution calculation and uses this device 5 Isocenter and An irradiation method is determined. This determination data is taken into the CT system 1 again at the time of laser marking described later.
[0033]
If NO in step 104, the treatment plan is entered without calculating the dose distribution. That is, the interactive function of the CT system is activated in step 105, and a treatment planning method is selected in step 106. In this embodiment, two types of “scano plan” and “oblique plan” are prepared as treatment plan methods, and one of them is selected in step 107a or 107b.
[0034]
The scan plan uses either or both of the front image (top image) and the side image (side image) of the scan image. Socenta (If there is only one scano image, Center In order to determine the vertical direction, at least one axial image is required.) This is a plan suitable for routine irradiation (one or two opposite) of uterine cancer, laryngeal cancer, etc., and the collimator of the treatment apparatus 2 65 control information is also output.
[0035]
Furthermore, an oblique plan which is a second plan of the treatment planning method will be described. The oblique plan is used when the above-mentioned scano plan is difficult to plan, and a plurality of targets (targets) and important organs can be accurately traced by the ROI. In addition, a plurality of axial images are used to create and display a transmission image and a target image from a virtual source (assuming that the source rotation plane is at an arbitrary angle and an axial plane), and beam irradiation and safety margins are appropriate. It is possible to accurately grasp whether or not. Here, control information for multi-port irradiation and collimator is also output.
[0036]
FIG. 4 shows an outline of this oblique plan.
[0037]
First, in step 120 of FIG. 19, the main controller 40 selects an axial image and a scano image necessary for the plan. In such an oblique plan, the scanogram is isolated in the body axis direction. Center Used for specification.
[0038]
Next, the process proceeds to step 121, and ROI tracing of the target and the vital organ is performed. That is, as shown in FIG. 5, the position and shape of the target and the important organ are ROI traced on the selected image using the mouse.
[0039]
Next, in step 122, the isolator on the (XY) plane is Center It is specified. In other words, the (XY) plane (axial surface) iso Center In order to determine, all the ROIs having the designated target number / important organ number are superimposed and displayed on the image designated by the user by image forwarding. Based on this superimposed ROI, the user can Center The location is estimated (see FIG. 6). Iso Center is Stored in the system along with the target number.
[0040]
Next, in step 123, the isolator on the (XZ) plane is Center It is specified. That is, the (X-Z) plane (plane in the body axis direction) Center Display the scanogram to determine. On this scanogram, the shapes of the target and the important organ are superimposed. Users can refer to these and isolate large cross-ROIs. To the center Set (see FIG. 7). Stored with this isocenter target number.
[0041]
Next, the process proceeds to step 124, where the isochronism is detected on all images. center It is determined whether I / C has been determined. If there are remaining images, steps 123 and 124 are repeated. All iso center When the I / C is determined, the process proceeds to step 125, and the virtual source position and beam angle are designated. As the irradiation method here, one gate irradiation, two opposing gate irradiations, two right angle gate irradiations, and multiple gate irradiations are possible.
[0042]
Next, in step 126, a transmission image in an arbitrary direction is created from the three-dimensional tomographic image data.
[0043]
An image created on the assumption that a beam is emitted from a virtual radiation source is referred to as a transmission image (see FIG. 8). By using this transmission image, an image that is geometrically equivalent to that during treatment can be obtained. If the geometric distance of the treatment device, SAD (Source-to-axis-of radiation distance) and SID (Source-to-image-receptor distance) are known, transmission images can be obtained (these are “environmental parameters”). Should be set as).
[0044]
The procedure for creating the transmission image will be described with reference to FIG.
[0045]
First, in step 126-1 in the figure, an initial image necessary for transmission image creation is displayed on the display 47, for example, in a divided manner as shown in FIG. Here, an axial image, a sagittal image, and a coronal image are created by cross-sectional transformation from a plurality of three-dimensional X-ray CT images, and the limitation of the integration range for transmission image creation described below is as follows: Depending on the irradiation direction of the virtual radiation source, one, two, or three of the axial image, sagittal image, and coronal image are appropriately used. In this embodiment, the image includes the spine, and the axial range and the sagittal image are used to limit the integration range. The axial image and the sagittal image have line segments ROI; LU and LL indicating the integration range, respectively. It is displayed superimposed on the initial position (see FIG. 10). These line segments ROI; LU, LL can be moved in the integrated path direction P for transmission image creation with the mouse of the input device 48, etc., and the line segments ROI; LU, L, on any image (for example, axial image) When LL is moved, the corresponding ROIs on other images (for example, sagittal images); LU, LL are also moved in conjunction with each other.
[0046]
Next, in step 126-2, the main control unit 40 determines whether or not to convert the CT value by detecting whether or not the operator clicks the “CT value conversion” area on the screen via the mouse or the like. To do. This CT value conversion is related to the subject of the present invention, and an attempt is made to create a CT image in which a bone portion is emphasized in advance while creating intermediate three-dimensional voxel data from a plurality of X-ray CT images. It is. If the operator clicks as shown in FIG. 11 and the determination in step 126-2 is YES (converts the CT value), then the CT value is actually converted in step 126-3. In this embodiment, this CT value conversion is performed using a conversion table stored in advance in the internal memory, and its input value (CT value before conversion) vs. output value (CT value after conversion). As shown by the curved convex portion in FIG. 14, the CT value range RBONE of interest such as bone is emphasized by giving characteristics of output values larger than those of other CT value regions. ing. The convex region RBONE in FIG. 14 has an input CT value ranging from about 200 to an appropriate value above it.
[0047]
Note that the conversion table used for CT value conversion may have the conversion characteristics shown in FIG. 15 in addition to the characteristic curves shown in FIG. In the case of FIG. 15, the slope of the input CT value-output CT value is gentle in the range where the input CT value is less than “200”, which generally corresponds to bones, and in the range above “200” which is the threshold value. The curve jumps stepwise and increases its slope. Thereby, a tissue having a CT value of “200” or more such as a bone is emphasized.
[0048]
After the CT value conversion is completed in this way, intermediate three-dimensional voxel data is created by axial interpolation in step 126-4.
[0049]
If it is determined in step 126-2 that the CT value conversion is not performed, the processing of steps 126-3 and 4 is skipped and the process proceeds to step 126-5.
[0050]
Next, the process proceeds to step 126-5, and the main control unit 40 inputs the positions of the line segments ROI; LU, LL on the image. At this time, assuming that the line segment ROI; LU, LL of the axial image is narrowed to the vicinity thereof while sandwiching the spine B, for example, as shown in FIG. The determination of “whether or not the line segment ROI has moved” is confirmed as YES (moved).
[0051]
In this case, in step 126-7, the line segment ROI; LU, LL on the sagittal image is also moved in conjunction. Then, in step 126-8, it is determined whether or not the ROI position is finally determined based on the input information of the operator. If NO, the process returns to step 126-5. In the case of YES, the process proceeds to step 126-9, and the integrated (addition) range in which the determined position information is read and a transmission image is created is calculated. The integration range Py is set to a narrow range in the integration path direction P with the spine B interposed therebetween as necessary.
[0052]
Next, the process proceeds to step 126-10, and the CT value of each path seen through with the virtual source as one point is added over only the set integration range Py to create transmission image data.
[0053]
In step 126-11, the created transmission image is divided and displayed on the display 47 for confirmation. This is illustrated in FIG. As shown in the figure, since the displayed transmission image is subjected to CT value conversion and the integration range Py is limited to a narrow region near the spine B, the contrast of the spine B with respect to the background image becomes much clearer.
[0054]
Finally, in step 126-11, the main control unit 40 temporarily stores the transmission image data in a predetermined area of the image memory 46 and finishes a series of processes for creating the transmission image. The process returns to step 127.
[0055]
FIG. 16 shows a flow of a series of processes in FIG.
[0056]
In the transmission image creation procedure shown in FIG. 9, the procedures relating to “CT value conversion” and “determination of integration range” are interchanged, and “determination of integration range” is performed first. May be. Furthermore, the program may be simplified so that only the procedure related to either one of “CT value conversion” and “determination of integration range” is performed. Even when only one of these processes is performed, the contrast of the spine B is enhanced.
[0057]
Furthermore, in the process of FIG. 9, when moving the line segment ROI to determine the integration range, an axial image, a sagittal image, and a coronal image are reconstructed using a plurality of CT tomographic images that have been converted into CT values, and these images May be displayed again. As a result, the integrated range Py can be more strictly specified by the line segment ROI while observing the spine B with improved contrast on the redisplayed image.
[0058]
On the other hand, in step 127 of FIG. 4, a target image is created. Target image is iso Center This refers to an image parallel to the containing plane (see FIG. 17). This target image is center The irradiation situation in each cross section parallel to the surface can be accurately grasped. Target image is iso center Since the image is horizontal to the surface, the cross-sectional direction is determined depending on where the virtual radiation source is located as in the transmission image. The user can specify a position in the depth direction by a mouse or numerical input (distance from the virtual radiation source, etc.), and can obtain a target image at that position. Further, in step 128, the trace results of the target and the important organ are synthesized on the transmission image and the target image, so that the irradiation range can be easily confirmed.
[0059]
Since the transmission image and the target image are created by cross-sectional transformation from the three-dimensional tomographic image data, an oblique image is obtained when the position of the virtual source is oblique to the X, Y, and Z axes.
[0060]
In step 129, an irradiation field and a safety margin are set. That is, since the treatment apparatus is equipped with a multi-leaf collimator, as shown in FIG. 18, the shape of the target is directly used as the irradiation field shape, and the safety margin is made similar to the irradiation field shape.
[0061]
Next, in step 130, the irradiation field is confirmed on the transmission image and the target image, and in step 131, it is determined whether or not resetting is necessary. In the case of resetting, the process returns to step 129, and when it is not necessary, the process proceeds to step 132, where the pyramid display on the axial image and the irradiation field display on the oblique image are performed, and the irradiation field, beam angle, Check parameters such as irradiation conditions. This is shown in FIG. In any case of the line cone and irradiation field shape display on the axial image and oblique image, the display can be performed by designating the target number and the virtual radiation source.
[0062]
Thereafter, if it is necessary to redo the various processes described above, the determination in step 133 is YES, and the process from step 129 can be redone. If YES in step 134, the process proceeds to step 135, and the set parameter data is stored in the memory.
[0063]
As mentioned above, the scano plan and oblique plan center Position (three-dimensional position data) and an irradiation field shape (two-dimensional shape data) on the body surface are set.
[0064]
Therefore, the main control unit 40 returns the processing to FIG. 3, performs the processing shown in steps 108 to 111, and performs the marking operation using the laser projectors 27a to 27c. This marking Center I / C position cross Marker Is to control the position of the projectors 27a to 27c and the position of the top plate 11a of the bed 11 so as to automatically instruct. Three on the body surface of the subject P Marker When these are irradiated, the operator marks these positions with a magic or the like, and is usually prepared for radiation therapy performed later.
[0065]
Subsequently, collimator control in radiation therapy by the treatment apparatus 2 will be described with reference to FIG. Here, the CT system 1 for making a treatment plan directly controls the opening of the collimator 65 of the treatment apparatus 2.
[0066]
First, in step 140 of FIG. 20, the main control unit 40 of the CT system 1 determines whether or not to perform radiation therapy based on operation information from the input device 48, and when performing therapy (YES), step 141. The processes of ˜143 are sequentially performed.
[0067]
That is, in step 141, the predetermined shape data of the irradiation field is called from the image memory 46. In step 142, the angle of the entire collimator 65 and the leaf control mode are set. This angle is determined appropriately according to the inclination of the irradiation field shape, for example, in the long axis direction. The leaf control modes include “inscribed mode”, “externally selected mode”, “middle point mode”, and the like.
[0068]
When the data for controlling the collimator 65 is determined in this way, the process proceeds to step 143 and the data is output to the collation recording device 4.
[0069]
The collation recording device 4 mainly focuses on fine adjustment of the irradiation field as time elapses from the time when the irradiation field is set to the actual radiotherapy. For example, a fluoroscopic mechanism added to the treatment device 2 is used. The fluoroscopic image obtained immediately before the treatment and the irradiation field set in the past are displayed in a superimposed manner, and the operator is collated and judged.
[0070]
If the result of this collation is, for example, that the lesion is small, NO is determined in step 145 as to whether or not collation is OK. In this case, in step 146, the position of the leaf is finely adjusted, and new correction data is prepared in the collation recording device 4.
[0071]
When the final collimator control data is thus established, the process proceeds to step 147 and the data is transmitted to the main control unit of the treatment apparatus 2. Receiving this, the main control unit independently drives the drive mechanism of each leaf along the control data.
[0072]
As a result, the size and shape of the opening formed by the two sets of leaf groups of the collimator 65 almost completely match the set irradiation field on the body surface, and X-rays subsequently performed on the internal lesion The irradiation range also almost completely matches. Therefore, after that, the radiotherapy is performed by the treatment apparatus 2 in accordance with the planned treatment method. The site to be treated (ie iso center When a plurality of radiation fields are set, radiation treatment is performed for each treatment site through the same collimator control data setting, collation confirmation, and collimator automatic control.
[0073]
As described above, in the radiotherapy system according to the present embodiment, conventionally, a plurality of devices such as an X-ray CT apparatus, a radiotherapy planning apparatus, and an X-ray CT simulator are used, and a scanner function for image acquisition, treatment Based on the integration of the planning function and the simulator function, a single CT system for radiation therapy planning is used to replace most of these functions and operations. Therefore, compared to conventional radiotherapy systems, the hardware configuration of the entire system can be reduced in size and simplified, and a significant space saving can be achieved, and transportation accompanying installation or room layout change is easy. Become.
[0074]
Further, in this embodiment, as schematically shown in FIG. 16, the range of the CT value conversion and transmission image creation is limited, and the contrast of mark sites such as bones and tracheal branch points is increased and emphasized. As a result, it is possible to accurately and easily identify the lesion of the patient using the mark site, and to accurately and easily check the transmission image and the X-ray film. Accuracy can be increased. In addition, since the position of the mark can be easily confirmed, the patient's restraint time can be shortened. Furthermore, when the integration range is limited, the amount of calculation for transmission image creation is also reduced, so that the transmission image creation time can be greatly shortened and the treatment plan itself can be completed in a shorter time.
[0075]
In the above embodiment, the CT system for radiation treatment planning is provided with an oblique plan and a simpler scano plan. However, only the function of the oblique plan may be provided as necessary.
[0076]
The CT value conversion process described above can also be applied to the image used in steps 122 and 123 of FIG. 4, and the CT value-converted bone-enhanced axial image, scano image (in this case, the CT image) The isocenter may be designated on the MPR image from (1).
[0077]
Furthermore, although the radiotherapy apparatus of the said Example used X-rays as a radiation source, it is not necessarily limited to this, The treatment apparatus which uses other radiation sources, such as a fast neutron beam and a gamma ray, may be sufficient.
[0078]
Next, a modified example related to transmission image creation according to the present invention will be described with reference to FIG. FIG. 1 shows a block diagram of a transmission image creating apparatus that specializes in creating a transmission image. The transmission image creating apparatus includes two first and second high-speed arithmetic processors 220 and 221, first to third memories 223 to 224, an input device 225, and a display device 226. In the first memory 223, a plurality of CT images are stored in advance. The input unit 225 can give processing instructions and other necessary information to the high-speed arithmetic processors 220 and 221 and can also instruct the display unit 226 to display the transmitted image. The first high-speed arithmetic processor 220 has a high-speed CPU, and when a process is instructed from the input device 225, a plurality of CT images are read from the first memory 222, and the CT is similar to the above-described embodiment. Three-dimensional voxel data is generated by performing value conversion, and the three-dimensional voxel data is stored in the second memory 223. Note that the first high-speed arithmetic processor 220 may fill the data in the space by performing axial interpolation together with CT value conversion.
[0079]
The second high-speed arithmetic processor 221 also has a CPU that operates at high speed, and operates by being energized by a processing command from the input device 225. That is, three-dimensional voxel data is read from the second memory 223, and CT values are added along each perspective line path for a given viewpoint, perspective angle, and perspective range to create transmission image data. The transmission image data is stored in the third memory 224, and the transmission image is displayed on the display 226 in response to a command. The second high-speed arithmetic processor 221 may execute filter processing such as edge enhancement together.
[0080]
Even in the transmission image creating apparatus configured and functioning in this way, the bone part of the subject is emphasized by CT value conversion, and the contrast of the part is also increased. For this reason, by providing this transmission image creation apparatus integrally or online with the above-described CT system, a suitable radiotherapy plan using a transmission image as described above can be made.
[0081]
【The invention's effect】
As described above, when creating a transmission image for use in determining the irradiation range and collating with the irradiation result, a process for emphasizing a part to be a mark such as a bone or trachea branch is added. Even when the proportion of the body thickness is low, the contrast of the landmark portion with respect to the background image can be significantly increased compared to the conventional one, and the position can be identified with high accuracy and simple. Can make a highly accurate treatment plan.
[Brief description of the drawings]
FIG. 1 is a schematic diagram of the overall configuration of a radiation therapy system according to an embodiment of the present invention.
FIG. 2 is a block diagram showing an outline of a CT system for radiation therapy planning.
FIG. 3 is a flowchart showing the overall flow of a treatment plan.
FIG. 4 is a flowchart showing the flow of an oblique plan.
FIG. 5 is an explanatory diagram for explaining an oblique plan.
FIG. 6 is an explanatory diagram for explaining an oblique plan.
FIG. 7 is an explanatory diagram for explaining an oblique plan.
FIG. 8 is an explanatory diagram for explaining an oblique plan.
FIG. 9 is a flowchart illustrating a flow of transmission image creation.
FIG. 10 is a monitor screen for explaining a procedure for creating a transmission image.
FIG. 11 is a monitor screen for explaining a procedure for creating a transmission image.
FIG. 12 is a monitor screen for explaining a procedure for creating a transmission image.
FIG. 13 is a monitor screen for explaining a procedure for creating a transmission image.
FIG. 14 is a graph showing conversion characteristics of CT value conversion.
FIG. 15 is a graph showing another conversion characteristic of CT value conversion.
FIG. 16 is an explanatory diagram schematically illustrating the flow of transmission image creation.
FIG. 17 is an explanatory diagram for explaining an oblique plan.
FIG. 18 is an explanatory diagram for explaining an oblique plan.
FIG. 19 is an explanatory diagram for explaining an oblique plan.
FIG. 20 is a flowchart showing collimator opening control during treatment.
FIG. 21 is a block diagram showing a schematic configuration of a transmission image creating apparatus according to a modification.
FIG. 22 is a diagram illustrating a transmission image creation path of a conventional example.
FIG. 23 is a diagram for explaining inconveniences caused by conventional total thickness integration.
[Explanation of symbols]
1 CT system for radiation therapy planning (CT system)
11 Gantry
12 sleeper
13 Console
40 Main control unit
45 Image reconstruction unit
46 Image memory
47 Display
48 input device

Claims (3)

Three-dimensional voxel data is created from a plurality of X-ray CT images of the subject, and a transmission image is created when the three-dimensional voxel data is seen through from a virtual position of the radiation source. In a CT system designed for radiation therapy planning,
By converting the CT values of the plurality of X-ray CT images with non-linear conversion data in which the bone of the subject in the transmission image is emphasized, the contrast of the bone portion is enhanced while the CT values of the plurality of X-ray CT images are enhanced. Three-dimensional data creating means for creating the three-dimensional voxel data ;
An integration range setting means for setting an integration range of CT values of the voxel data along the fluoroscopic direction;
The transmission image including the voxel data in which the contrast of the bone part of the subject integrated to according the voxel data created by the three-dimensional data generation means on the integration range set by the integration range setting means And a transmission image creating means for creating a CT system. A three-dimensional data creating means for creating three-dimensional voxel data from a plurality of X-ray CT images of a subject, and creating a transmission image when the three-dimensional voxel data is seen through from a virtual position of a radiation source; In a CT system in which a transmission image is used for planning radiotherapy of the subject,
An integration range setting means for setting an integration range of CT values of the voxel data along the fluoroscopic direction;
A transmission image creation means for creating the transmission image including the voxel data in which the voxel data is integrated according to the integration range set by the integration range setting means and the contrast of the bone part of the subject is emphasized; CT system characterized by comprising.   The integrated range setting means includes means for displaying a reference image related to the three-dimensional voxel data, and means for displaying an ROI capable of limiting the bone portion in the fluoroscopic direction on the reference image by superimposing the reference image on the reference image. The CT system according to claim 2, further comprising:

Images