JPH0481469B2 - - Google Patents

Description

[Detailed Description of the Invention] [Objective of the Invention] (Industrial Application Field) The present invention is directed to measuring the dose of radiation irradiated and transmitted to a patient during radiation therapy, processing the transmitted dose as data, The present invention relates to a radiation therapy device that has the function of determining the irradiation field area and water permeation thickness, measuring the movement of a patient or affected area based on changes in transmittance over time, and stopping radiation irradiation as necessary.

(Prior Art) Conventional radiation therapy equipment includes, for example, a linear particle accelerator that accelerates electrons using high-frequency electrolysis, a betatron that accelerates electrons using an alternating magnetic field, and a cobalt therapy equipment that uses a radioisotope such as cobalt-60 as a radiation source. etc. are known.

When performing treatment using the radiation therapy device, first, the specifications such as the shape and location of the lesion are determined using various diagnostic devices such as an X-ray CT device, and then,
The dose of radiation to be irradiated is calculated using a treatment planning device, etc., and the necessary data is obtained. Based on the obtained data, the affected area is treated by emitting radiation using a radiotherapy device.

Next, regarding the outline of the radiotherapy device, the fourth
The explanation will be given with reference to the figures and FIG.

As shown in FIG. 4, a fixing frame 1 for fixing the radiation therapy device is installed in the treatment room.
A rotary pedestal 2 is attached to the fixed pedestal 1 so as to be rotatable about a center line A. An irradiation head 3 is attached to the horizontal axis of the rotating pedestal 2, and a treatment bed 5 for holding a patient 4 in a fixed position is installed in front of the irradiation surface of the irradiation head 3.

In addition, the cassette 7 that stores the X-ray film is
The photosensitive surface of the X-ray film, which is attached to the rotating frame 2 via the support column 8 and stored in the cassette 7, is arranged so as to always face the irradiation surface of the irradiation head 3 regardless of the rotation of the rotating frame 2. ing.

On the other hand, irradiation of radiation such as X-rays from the irradiation surface of the irradiation head 3 is carried out as follows. That is, as shown in FIG. 5, the electrons generated in the electron generating section 9 are guided to the electron accelerating section 10, and the microwaves oscillated by the microwave generating section 11 are applied to the electron accelerating section 10 to perform microwave electrolysis. This generation accelerates the electrons guided to the electron acceleration section. The accelerated electrons are then deflected in a desired direction by the deflection unit 12, the deflected electron beam is converted into X-rays, and the diaphragm unit 13 installed in the irradiation head 3 is used to irradiate the affected area 6 according to the target direction. form a field,
The affected area 6 is irradiated with X-rays through the aperture part 13. The film stored in the X-ray cassette 7 that has passed through the body of the patient 4 is also irradiated.

Then, the rotating frame 2 equipped with the electron generator 9, the electron accelerator 10, the microwave generator 11, the deflector 12, the diaphragm 13, and the cassette 7 is driven to rotate around the center line A. The affected area 6 can be treated by irradiating X-rays from all orthogonal angles.

Furthermore, prevention of X-ray exposure to normal tissue and analysis of irradiation dose are performed as follows. That is,
As shown in FIG. 5, the angle detection section 15 detects the rotation angle of the rotating frame 2 driven by the rotation mechanism section 14, and outputs the detected signal to the aperture control section 16. The aperture control unit 16 controls the aperture unit 13 according to the rotation angle of the rotary pedestal 2 from the detection signal and data regarding the affected area 6 obtained in advance,
X-rays are irradiated only to the affected area 6 to minimize the exposure dose to normal tissues.

Furthermore, when the X-rays passing through the patient's body irradiate the film in the cassette 7, the film is exposed to the affected area 6.
It is exposed to light so that the degree of blackening is proportional to the irradiation dose on the tomographic plane. By analyzing the degree of blackening of this film, it is possible to know the approximate value of the irradiation dose distribution in the affected area 6 and its surroundings.

(Problem to be solved by the invention) However, with the above method, it is necessary to analyze the degree of blackening of the film, and that data cannot be obtained until after irradiation, and the value is an approximate value of the relative dose. Moreover, it is the integrated value of one irradiation,
During the specified time during irradiation, the transmitted dose value at the specified angle cannot be obtained. Therefore, there has been a problem in that it is not possible to detect or correct movement of the patient or affected area during irradiation or for each irradiation, making it impossible to perform accurate and optimal radiation therapy.

Therefore, the present invention was made in view of the above circumstances, and a dosimeter is arranged so as to sandwich a treatment bed holding a patient and face an irradiation head, and the radiation transmitted through the patient's body is measured by time or angle. The purpose of this system is to provide a radiotherapy device that enables accurate and optimal radiotherapy by continuously measuring each dose and accurately determining the transmitted dose in absolute value from the data. .

[Structure of the invention]

(Means for Solving the Problems) In order to solve the above problems and achieve the objects, the present invention provides a radiation treatment method for treating an affected area by irradiating radiation from an irradiation head while rotating a rotary pedestal to which an irradiation head is attached. In a treatment device, a dosimeter having a number of detection elements arranged opposite to an irradiation head and converting a radiation dose into signal data proportional to the dose, and a monitor for data from the dosimeter and radiation output of the device. A data collection unit collects the detection data output from the circuit at fixed time intervals for each rotation angle of the rotating mount, and based on the data collected by this data collection unit, the absolute value of the equivalent dose, equivalent rate, and water equivalent thickness are calculated. , a data processing unit that calculates and processes the irradiation field shape and irradiation field area, and compares the data processed by this data processing unit with the same data during irradiation or the previous irradiation and outputs a radiation output stop signal. The present invention is characterized by comprising a data comparison section that performs the following operations.

(Function) According to such a configuration, the dose transmitted through the patient during irradiation is measured, and the absolute dose is calculated based on the data. This data is measured with and without a patient, and transmittance, water equivalent thickness, irradiation field area, and irradiation field shape can be calculated from each absolute dose.

In addition, by checking the change in transmittance during irradiation, it is possible to confirm the presence or absence of patient movement, and by comparing the transmittance with the previous irradiation, it is possible to check the reproducibility of patient positioning and changes in the affected area or surrounding tissue. Irradiation can be stopped if the deviation exceeds a specified value.

Furthermore, by comparing the irradiation field shape and aperture opening setting data, it is possible to detect abnormalities in the control system, drive system, and detection system of the apparatus, and to measure the actual irradiation field accurately regardless of the control system of the apparatus.

(Example) Next, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing the relationship between the diaphragm and the dosimeter, and FIG. 3 is a block diagram showing the implementation row.

The mechanical configuration of the radiation therapy device according to the present invention differs from the conventional radiation therapy device shown in FIG. 4 in that, as shown in FIG. 1, a dosimeter 17 is provided in place of the cassette 7. It is. That is, the dosimeter 17 is attached to the rotating pedestal 2 via the support 8, and the dosimeter 17 is attached to the top plate of the treatment bed 5 that holds the patient 4 regardless of the rotation of the rotating pedestal 2. The irradiation surface and the irradiation surface of the irradiation head 3 are always arranged to face each other.

As shown in FIG. 2, on the entrance surface of the dosimeter 17, a large number of semiconductor detection elements 20 are arranged in a matrix to detect radiation and convert it into a voltage proportional to the radiation dose.

On the other hand, a constriction section (not shown) is incorporated in the irradiation head 3 facing the dosimeter 17. As shown in FIG. 2, the aperture unit includes a first aperture device 19 that moves in the direction B in FIG. 2 and is composed of a plurality of sets of aperture blades arranged opposite each other, and It has a second diaphragm device (not shown) that moves in a direction perpendicular to the direction and includes a plurality of sets of diaphragm blades arranged opposite to each other.

The diaphragm section is configured to form an opening corresponding to the shape of the affected area 6 by moving opposing diaphragm blades in the first diaphragm device 19 and a second diaphragm device (not shown) toward and away from each other.

Moreover, if a large number of semiconductor detection elements 20 are arranged in a matrix on the entrance surface of the dosimeter 17, as shown in FIG. 2, so as to correspond to the aperture blades 19a to 19g, When radiation is irradiated from the irradiation head 3 through the diaphragm, the semiconductor detection element in a region similar in shape to the aperture of the diaphragm is detected.
20b ₆ ~ 20b ₈ , 20c ₅ ~ 20c ₉ , 20d ₄ ~ 10d ₁₀ , 20e ₄ ~
20e ₉ , 20f ₆ to 20f ₈ output a voltage signal proportional to the radiation dose.

The circuit configuration of the radiation therapy device according to the present invention differs from that of conventional radiation therapy devices as shown in FIG.
2. Data collection section 23, data processing section 24, data comparison section 25, signal processing section 26, time generation section 27
and that a selection circuit 28 is newly provided.

The dose detection unit 21 includes a semiconductor detection element 20 and an amplifier, and is configured such that each semiconductor detection element 20 irradiated with radiation outputs a voltage signal proportional to the radiation dose for each element. The converter 22 inputs the output signal from the dose detection section 21, converts it into a digital signal of a code, for example, a BCD code, and outputs the digital signal.

The signal processing section 26 inputs an output dose signal of the apparatus main body from an output dose monitor circuit of the apparatus main body (not shown), processes the signal, and outputs a signal equivalent to that of the converter 22. The time generator 27 outputs a time signal used during fixed irradiation, the angle detector 15 that detects the rotation angle of the rotating pedestal 2 outputs an angle signal used during rotation irradiation, and the selection circuit 28 outputs a time signal used during fixed irradiation. The time signal has the function of selecting the angle signal and outputs a signal that matches the irradiation method. Furthermore, the aperture control section 16 outputs an aperture opening setting signal. These signals are input to the data collection section 23. The data collection unit 23 collects radiation data corresponding to time or angle of these signals, and also collects aperture opening setting data.

The collected data is input to the data processing section 24. The data processing unit 24 stores the input data, and after normalizing the transmitted dose with the output dose of the apparatus main body, calculates the absolute value of the transmitted dose. In addition, the transmittance of the dose transmitted through the patient is calculated by measuring the absolute value of the transmitted dose when there is no patient and comparing it with the absolute value of the transmitted dose when the patient is present. Here, by determining the transmittance with respect to water depth and inputting the value in advance as a transmittance table with respect to water depth, the irradiated area of the patient is calculated as the water equivalent thickness from the transmittance calculated above.
Also, based on the absolute value or relative value of the determined transmitted dose, the irradiation field shape and area are calculated by defining the irradiation range to be the area above the specified value.

These various calculation data are input to the data comparison section 25. The data comparison unit 25 outputs these calculation results to a display/recording device (not shown), and
Transmittance data within the patient is compared every time during irradiation or with the same data from the previous irradiation, and an irradiation stop signal is output when the difference exceeds a specified value. It also compares the diaphragm opening setting data with the calculated irradiation field shape, and outputs an irradiation stop signal when the difference exceeds a specified value. When this irradiation stop signal is generated, the radiation generation of the device is stopped.

Note that the aperture control section 16 controls the aperture opening degree of the aperture section 13, that is, the irradiation field, based on the angle signal output from the angle detection section 15 and preset aperture control data.

Since the radiation therapy apparatus is configured as described above, during rotational irradiation, when radiation is irradiated from the irradiation head 3 to the affected area 6 while rotating the rotating pedestal 2 around the center line A, the amount of radiation transmitted through the patient's body is measured. can be collected for each angle of the rotating gantry, and during fixed irradiation, can be collected for each time to determine the absolute dose.

Furthermore, by obtaining data when there is no patient and data when there is a patient (during treatment), the transmittance within the patient can be calculated, and this transmittance can be compared at each time during one irradiation (fixed irradiation). By comparing the patient's movement with the previous data (time or angle), it is possible to check the reproducibility of patient positioning and changes in the affected area and surrounding tissues. Since radiation output can be stopped during treatment, safe and reproducible treatment can be performed.

Furthermore, by comparing the aperture opening setting data that sets the irradiation field with the irradiation field shape data obtained by calculation, the own irradiation field can be determined regardless of failures in the device control system or detection system, and the specified irradiation field can be determined. When the deviation exceeds the value, radiation output can be stopped, allowing safe and reliable treatment.

One embodiment of the present invention has been described in detail above, but
The present invention is not limited to the above embodiments,
Various modifications can be made within the scope of the invention.

For example, the number of semiconductor detection elements, their arrangement method, and data collection method can be changed as necessary.

In addition, the data collection section, data processing section, data comparison section, etc. can be shared with the device's own control system and monitoring system, or data processing for each irradiation can be performed by adding up multiple pieces of dose data obtained from one irradiation. You can also do it.

〔Effect of the invention〕

According to the present invention, the following effects can be achieved. That is, in the radiation therapy apparatus according to the present invention, the dosimeter is provided so as to sandwich the treatment table holding the patient and face the irradiation head, so that the transmitted dose of radiation can be accurately measured in absolute value. In addition, based on this data, the patient's transmittance, water equivalent thickness, etc. are calculated, and by comparing the same data every time during irradiation or the previous time, it is possible to check the reproducibility of patient movement and patient positioning. When the difference becomes large, radiation output can be stopped.

Furthermore, it is possible to compare the irradiation field setting data and the actual irradiation field shape based on the transmitted dose data, and if the difference becomes large, the radiation output can be stopped.

Therefore, with the radiation therapy apparatus according to the present invention, more accurate, safer, and highly accurate radiation therapy can be performed.

[Brief explanation of drawings]

FIG. 1 is a schematic explanatory diagram showing an embodiment of the present invention;
Figure 2 is an explanatory diagram showing the relationship between the aperture part and the dosimeter;
FIG. 3 is a block diagram showing the same embodiment, FIG. 4 is a schematic explanatory diagram showing a conventional device, and FIG. 5 is a block diagram of the same device. 2... Rotating frame, 3... Irradiation head, 17... Dosimeter, 23... Data collection section, 24... Data processing section,
25...Data comparison section, 26...Signal processing section, 27...
Time generator, 28... selection circuit.

Claims (1)

[Claims] 1 In a radiation therapy device that treats an affected area by irradiating radiation from the irradiation head while rotating a rotary frame to which the irradiation head is attached, a signal that is placed opposite to the irradiation head and is proportional to the radiation dose. A dosimeter that has a large number of detection elements that is converted into data, and data collection that collects data from this dosimeter and detection data output from the radiation output monitor circuit of the device at every rotation angle of the rotating stand or every fixed time. a data processing section that calculates and processes the absolute value of equivalent dose, equivalent rate, water equivalent thickness, irradiation field shape, and irradiation field area based on the data collected by this data collection section; What is claimed is: 1. A radiation therapy apparatus comprising: a data comparison section that compares and processes the data obtained during irradiation or the same data from the previous irradiation and outputs a radiation output stop signal.