JPH10328318A - Radiotherapy system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a radiotherapy system which enables determining of a period during which a lesion moving associated with respiration rests for any organ containing the lesion, quantitatively and automatically setting of an irradiation allowable period based on the period and radiotherapy synchronizing with the period thus quantified. SOLUTION: This system comprises an image diagnosing device 60, a respiration detection means 61, a photographing means to photograph a lesion measuring time, an image extraction means 17 to extract a rest period of the lesion, a means 19 by which the timing of an image extracted is collated 18 with that of respiration information obtained by the respiration detection means to extract the rest period of the lesion as irradiation control period and a means 22 to set an irradiation starting/ending point from the period extracted. A radiotherapy is conducted during the set irradiation control period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiotherapy system for performing radiotherapy on the basis of image diagnostic information of a lesion of a subject.

[0002]

2. Description of the Related Art In radiation therapy, it is important to irradiate only a lesion with an electron beam and a radiation beam while suppressing exposure of normal tissues around the lesion. In particular, it is important that the respiratory movement of the treatment target can accurately irradiate only the lesion that moves with the respiration.
In that sense, it is significant to use the respiratory-gated irradiation method.

[0003] Here, the respiratory-gated irradiation method is a method of irradiating a lesion with the above-mentioned beam in synchronization with the rest period of the lesion moving by respiratory movement. For the period during which the lesion is stationary, see "Study on respiratory phase-synchronized irradiation."
(Kiyoshi Ohara, 6 others: Journal of the Japan Society for Medical Radiology, No. 47
Vol. 3, No. 3, 488-496, 1987), and the lesion is located at a fixed position during end expiration (when exhaling) of about 2 seconds out of about 5 seconds in one cycle of breathing. .

As for the setting of a synchronizing (control) signal for irradiating in synchronism with the rest period of a lesion, see "Development of respiratory-gated irradiation method and its clinical evaluation" (Hiroshi Tsuji, 5 others: Video Information Medical: Vol.25: No.19: P1071-
1077: 1993), and confirming that the synchronization (control) signal is correctly tuned to the actual respiratory phase by an aiming / confirmation system of the irradiation field by the X-ray fluoroscope. This is a method of performing irradiation after setting.

According to such a respiratory-gated irradiation method, more ideal radiotherapy can be performed as compared with a general irradiation method in which an irradiation field is set wide so as to include the entire moving range of a lesion. .

[0006]

In order to perform respiratory-gated irradiation, it is important to accurately determine the rest period of a lesion. If the rest period of this lesion is different from the respiration information, it means that the irradiation synchronization (control) signal for treatment is shifted, and irradiation is performed including the period during which the lesion is moving. Exposure to normal tissues. In this sense, the conventional X before treatment is also used.
The method of confirming with the fluoroscope and setting the synchronization (control) signal is a method of visually confirming the period during which the lesion is stationary and setting the synchronization (control) signal. Because there are limits to improving accuracy,
Irradiation including the period during which the lesion is moving is performed as described above, or treatment irradiation is performed by narrowing the period during which the lesion is stationary. There must be a method available.

There is also a need for an improvement in that the conventional method cannot be used for any organ including a lesion with an X-ray fluoroscope.

[0008] An object of the present invention is to be able to grasp the period during which a lesion moving with respiration is stationary for any organ including the lesion, and to quantitatively and automatically determine the irradiation period based on the period. An object of the present invention is to provide a radiotherapy system that can be set and perform radiotherapy in synchronization with the quantified period.

[0009]

The object of the present invention is to provide an image diagnostic apparatus for obtaining an image capturing the movement of a lesion moving with respiration, a respiratory detecting means for detecting respiratory information,
A photographing means which starts simultaneously with the detection of the respiratory information and photographs the lesion while measuring the time from the start; and an image extracting means for extracting a period during which the lesion is stationary from an image photographed by the photographing means. Extracting means for extracting an irradiation control period by comparing the time between the image range and the respiration information; setting means for setting an irradiation start point and an irradiation end point at the time of irradiation from the irradiation control period; This can be achieved by a radiotherapy system including a radiotherapy apparatus that performs irradiation in synchronization with the period from the irradiation start point to the irradiation end point based on the respiration information obtained by the respiration detection means at the time.

Further, the image extracting means for extracting the rest period of the lesion is a subtraction means for obtaining a subtraction image based on a plurality of images obtained by the photographing means, and a gradation preset based on the subtraction image. This can be achieved more by means of extracting a range. Further, the subtraction means can be achieved by means for calculating and displaying a difference between CT values between images, and means for calculating and displaying an absolute value of a difference between CT values between images.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 4 shows a system configuration of the radiotherapy system. The X-ray CT apparatus 60 (image diagnostic apparatus) collects image data of a lesion of a treatment target using dynamic scan, spiral scan, or the like. Image the lesion while measuring. The respiratory synchronization device 61 (respiration detection means) is connected to a strain gauge for detecting the abdominal pressure of the body to be treated and a lamina for detecting the ventilation volume in order to obtain respiration information, displays the detected respiration information, and displays the respiration information. An irradiation start point and an irradiation end point of radiation to the body are set (22 in FIG. 1 described later). This respiratory synchronization device 61
At the time of treatment, it is connected to a treatment device 70 composed of a control unit 65, an accelerator 66, a gantry 67, and a treatment table 68, and while taking respiration information 83 from the treatment target 90, breathes based on the set irradiation start point and irradiation end point. The synchronization signal 84 is created (23 in FIG. 1) and the control unit 6
5 is output.

The treatment planning device 62 includes image information 80 from the X-ray CT device 60 and breath information 8 from the respiratory synchronization device 61.
The operator inputs 1 and plans how to radiate radiation to the subject to be treated based on these two pieces of information. This device 62 has a subtraction function (FIG. 1).
10), an area calculation function (13 in FIG. 1), a focus rest period extraction function (17 in FIG. 1), a collation function (18 in FIG. 1), etc., and image information 80 from the X-ray CT apparatus 60. Is input, the image of the lesion during the rest period is extracted (17 in FIG. 1), and the respiration information 81 from the respiratory synchronization device 61 is further input, and this information 81 is compared with the image during the rest period (FIG. 1). 1
8) Then, the irradiation start point and the irradiation end point are determined from the both (20 in FIG. 1), and the data is output (21 in FIG. 1).

The control unit 65 controls the respiratory synchronization signal 8
4 to output control signals 86, 87 and 88,
6, the gantry 67, the treatment table 68, and the like are controlled to perform respiratory-gated irradiation.

The collation device 63 inputs data 85 planned by the treatment planning device 62, sends the data 85 to the control unit 65, and constantly communicates with the control unit 65. The information that moves the gantry 67 and the treatment table 68 is received, and it is confirmed whether or not the plan made in the treatment plan is executed as it is.

Next, an embodiment of the present invention will be described in detail with reference to FIGS. In FIG. 1, the numbers in parentheses correspond to the device numbers.

At the same time, the collection of image information by the X-ray CT apparatus 60 (step 2) and the collection of respiration information of the subject by the respiratory synchronization apparatus 61 (step 3) are started (step 1)
At the same time, time measurement (step 1) is performed at the same time. The time is stored as data at the time of image acquisition in the X-ray CT apparatus, and the respiration information can be obtained as a time axis.

When the collection of image information by the X-ray CT apparatus 60 is completed (step 4), image data is output (step 5). On the other hand, when the collection of the respiration information by the respiratory synchronization device 61 is completed (Step 4 ′), the respiration information is output (Step 6).

From the images obtained by X-ray CT, a plurality of original images near the end-expiration where the lesion rests are shown in FIG.
The subtraction function is started based on the plurality of pieces of image data (step 10), and the subtraction image between the images is obtained as shown in FIG. 2 (ab-f-f).
Collect as shown in g) (step 11). If the focus is moving, the moving part appears as a difference in gradation (black part 51 or white part 52) in the subtraction image. However, in the range where the lesion is stationary, there is no difference in the gradation in the subtraction image, and the gradation is almost 0.
It is a nearby image. The black portion 51 has a minus gradation, and can be regarded as a gradation range where the gradation is −50 or less, for example. The white portion 52 has a positive gradation, and can be regarded as a gradation range of, for example, a gradation of +50 or more. The gradation range of the black portion 51 and the white portion 52 is specified in advance (for example, when the gradation is minus 50).
The following range and the range of plus 50 or more are designated as gradation ranges), the subtraction images obtained as shown in FIG. 2 are calculated one by one, and the area of the black portion 51 and the white portion 52 is calculated. (Step 13). In the case where there are many portions 53 near the gray level of approximately 0 between black and white, or in the case of all intermediate portions, the calculated area of the combined black portion 51 and white portion 52 is substantially zero. That is, a period during which an image having an area of approximately 0 is acquired is a stationary period.

Alternatively, by taking the absolute value of the gradation of the subtraction image, by taking the absolute value of the black portion where the gradation is minus and making it positive by taking the absolute value, all the moving portions of the lesion are displayed as white portions. can do.
In addition, by inverting the plus and minus of this image, all the portions where the lesion is moving can be displayed as black portions. By displaying in this way, the operator can clearly know the part where the lesion is moving. In the subtraction image having the absolute value as described above, for example, in a case where all the moving portions of the lesion are displayed as white portions, the gradation range of the white portion is designated in advance (for example, the gradation is plus 50). The above range is designated as a gradation range), the subtraction images are calculated one by one, and the area of the white portion is calculated (step 13). If there are many parts 53 whose gradation is near zero or all of them are intermediate parts, the calculated area of the white part is substantially zero. That is, a period during which an image having an area of approximately 0 is acquired is a stationary period.

From the result, an image range (c, d, e in FIG. 2) in which the area is substantially zero is output (steps 15, 16).
Then, a period during which the image is obtained is extracted as a period during which the lesion is stationary (step 17). This stationary period shows an image at the start point (c in FIG. 2) and an image at the end point (e in FIG. 2) of the stationary period. The extracted image has time data at the time of image acquisition as described above, and the extracted image information is input to the treatment planning device 62 (step 31).
At the same time, the respiratory information of the object to be treated, which is acquired at the time of imaging by X-ray CT, is input from the respiratory synchronization device 61 to the treatment planning device 62 (step 32). The respiration information waits for data as a continuous time, and the imaging performed by the X-ray CT starts at the same time as the acquisition of the respiration information of the respiratory synchronization device. Since the time of the image of the start point and the time of the image of the end point of the stationary period can be compared with the time of the respiration information, this comparison is performed (step 18), and the start point and the end point of the stationary period can be determined on the respiration information. (Steps 19 and 20), and the data of the start point and the end point are output to the respiratory synchronizer 61 (Step 2).
1) In the respiratory synchronization apparatus, the start point, the irradiation start point (40 in FIG. 3) and the end point are set to the irradiation end point (4 in FIG. 3).
Set as 1) (step 22). The irradiation start point (40 in FIG. 3) and the irradiation end point (4 in FIG. 3)
The period between 1) and 2) is a period during which the lesion is stationary, and is an irradiation period. Therefore, a respiratory synchronization signal (45 in FIG. 3) can be created during this period (step 23).

With reference to FIG. 3, the setting of the irradiation start point and the irradiation end point and the generation of the respiratory synchronization signal will be described in detail. The image data 100 is the X-ray CT device 60
, And a plurality of images are continuously collected. This raw data is acquired, for example, with a scan time of one second per image.

The original image 110 is the output of the image data in step 5 of FIG. 1 and includes the image data a to g of FIG. The original image 110 is reconstructed based on the image data 100 (raw data).
Minute time (eg 0.1 seconds) over a range of 00
This is an image obtained by shifting. Image 1 of focus rest area
20 is extracted in step 17 in FIG. 1, and the images c, d, and e are, as described above, image data a in FIG.
This is an image showing a period in which the lesion is stationary, where the area values of the white portion and the black portion are determined to be approximately 0 as a result of mutual subtraction of 〜g. That is, the start point of the still period is at the start point of the image c, and its end point coincides with the end point of the image d. This image 120 is input to the treatment planning device 62 for collation (step 18) in step 31. The respiratory information 81 is the output in step 6, where two convex waves indicate that the lesion moves due to respiration of the object to be treated is large, and a concave wave sandwiched between them indicates that the lesion moves little. Is shown. This respiration information 81 is input to the treatment planning device 62 in step 32. The treatment planning device 62 collates the image 120 of the focus rest period with the respiration information 81 (step 18), extracts the irradiation control period 46 in step 19, and determines the start point of the irradiation control period (start point of the image c) in step 20. Irradiation start point P
1. The end point (end point of the image e) is set to the irradiation end point P2.
And outputs the P1 and P2 data to the respiratory synchronizer 61 in step 21. The respiratory synchronization device 61 sets the respective points where the respiration information 81 intersects the points P1 and P2 as the irradiation start point 40 and the irradiation end point 41 in step 22, and stores the set values in the memory. The period between the points 40 and 41 is the period during which the lesion is stationary, and is the irradiation period. At the time of treatment, the respiratory synchronizer 61 for which the irradiation period has been set is inserted into the treatment device 7.
Connect to 0. The respiratory synchronization device 61 collects the current respiration information (83 in FIG. 4) of the treatment target (step 28),
Start point 4 of irradiation period already stored in memory
A respiration synchronization signal 84 is created from 0 and the end point 41 (step 23). That is, as shown in FIG. 3, the respiratory synchronization signal 84 is a high level between the irradiation start point 40 and the irradiation end point 41.
And an off signal 43 which is low during periods other than the on signal 42. The respiratory synchronization device 61 outputs the respiration synchronization signal 84 to the control unit 65 (step 2).
5) When the respiration information 83 is in the irradiation control period 46, the on-signal 42 causes the treatment device 70 to emit radiation to the treatment target 90. When the respiration information 83 is outside the irradiation control period 46, the off signal 43 is output to the control unit 65, and the irradiation of the treatment device 20 is prohibited.
After a lapse of a predetermined time, the treatment is terminated (step 3).
0).

[0023]

According to the present invention, for any organ including a lesion, the period during which the lesion moving with respiration stops can be grasped, and the irradiation period can be quantitatively and automatically determined based on the period. The radiation treatment with good operability can be performed because the irradiation time is accurate, and the irradiation period is accurate, so that a safe treatment that can minimize the exposure to normal tissues around the lesion can be performed.

[Brief description of the drawings]

FIG. 1 is a flowchart of a respiratory-gated irradiation system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a subtraction function according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram of irradiation control period setting according to the embodiment of the present invention.

FIG. 4 is a configuration diagram of a radiotherapy system according to an embodiment of the present invention.

[Description of Signs] 40 Irradiation start point 41 Irradiation end point 45 Respiratory synchronization signal 46 Irradiation control range 60 X-ray CT device 61 Respiratory synchronization device 62 Treatment planning device 70 Treatment device

Claims (3)

[Claims] 1. An image diagnostic apparatus for obtaining an image capturing the movement of a lesion moving with respiration, a respiratory detecting means for detecting respiratory information, and starting simultaneously with the detection of the respiratory information to start A photographing means for photographing a lesion while measuring the time from, an image extracting means for extracting a period in which the lesion is stationary from an image photographed by the photographing means, and a time between the image range and the respiration information. Extraction means for extracting an irradiation control period by matching, setting means for setting an irradiation start point and irradiation end point at the time of irradiation from the irradiation control period, and respiration information obtained by respiration detection means during treatment. And a radiation treatment apparatus that performs irradiation in synchronization with a period from the irradiation start point to the irradiation end point. 2. An image extracting means for extracting a stationary period of a lesion, wherein said image extracting means obtains a subtraction image based on a plurality of images obtained by a photographing means, and a predetermined gradation based on the subtraction image. 2. The radiotherapy system according to claim 1, comprising means for extracting a range. 3. The subtraction means includes means for calculating and displaying a difference between CT values between images, and means for calculating and displaying an absolute value of a difference between CT values between images. Radiation therapy system.