JPH09253226A - Radiotherapeutic apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrict undesired exposure dose to normal tissues by calculating a deviation value between the current respiratory waveform and that during the rest period to forbid the irradiation of radiation when an integrated value of the deviation values during a specified cycle exceeds a specified value. SOLUTION: Prior to the start of treatment, a CPU 20 inputs a specified cycle of respiratory waveforms from a strain gauge or an air current transducer through an A/D converter 22 and averages the waveforms to record the results into a memory 24 as past respiratory waveform. The number of the input waveforms is inputted by an operator from an input section 42. The past respiratory waveforms are displayed on a display section 44 and the operator inputs an irradiation allowable range by the input section 42. The CPU 20 detects the inclination, level and the like of a respiration signal at the staring and ending points of the irradiation allowable range to be recorded into the memory 24. The CPU 20 determines a deviation value between the current respiratory waveform and the past respiratory waveform and compares an integrated value of the deviation values with a specified value during one cycle to judge abnormality in the respiratory signal. When the integrated value is above the specified value, abnormality is determined to forbid the irradiation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radiation therapy apparatus for irradiating an affected area with radiation, and more particularly to a radiation therapy apparatus which turns on and off a radiation output in synchronization with respiratory movement, and which moves a respiratory moving organ (an organ moving with respiration). For example, the present invention relates to a radiation therapy apparatus that performs respiratory synchronization irradiation suitable for the treatment of lung, liver, spleen, and the like.

[0002]

2. Description of the Related Art In radiotherapy, a radiation irradiation method called a stereotactic method has attracted attention. The stereotactic method is a treatment method aimed at destruction of the lesion by applying a high dose from multiple directions only to the lesion, using a narrow beam of radiation to concentrate stereoscopically at one point, Irradiation to the normal tissue at the site where the lesion is destroyed by the treatment is extremely reduced, so that there is an effect of reducing adverse effects on the normal site.

[0003] When a respiratory moving organ (eg, lung, liver, spleen, etc.) whose lesion moves with respiration is treated by a stereotactic method, since the radiation is limited to the lesion cells, the target moves. It is necessary to have a technique for irradiating radiation by reliably grasping the situation. Therefore, as shown in FIG. 10, a respiratory tuning irradiation method has been proposed in which a strain gauge 60 is attached to a patient's abdomen 62 with a tape 64 to detect a respiratory phase, tune the target to a state where it can be regarded as stationary, and radiate radiation. I have. The strain gauge 60 has a leaf spring 60B as shown in FIG.
When the piezo element 60A moves up and down in conjunction with the respiratory movement of the abdomen against the spring force of the above, the distortion generated in the piezo element 60A is detected as an electric signal.

[0004] In addition to the above-mentioned strain gauge, an airflow transducer 80 as shown in FIG. 11 is inserted into the mouth of a patient, and an airflow resistance tube 80A generates a pressure difference during exhalation and inhalation. By detecting with the differential pressure gauge 80B, the respiratory phase can be detected.

[0005]

However, during the treatment while detecting the respiratory phase using a strain gauge or an airflow transducer as described above, the tape of the strain gauge may become loose, or the airflow of the airflow transducer may be reduced. The signal value may gradually differ from the initially detected respiration signal, such as when the resistance tube is clogged. Unstable breathing may occur due to hiccups or sneezing.

Further, when irradiating radiation by the respiratory synchronization irradiation method, the radiation irradiation timing is controlled by software based on detection signals input from various detection devices. For this reason, the software is complicated because of its multi-function, and may have low reliability and malfunction. In such a case, when the radiation is applied, there is a problem that the respiratory phase to be irradiated may be incorrect and the normal tissue may be exposed.

The present invention has been made in view of such circumstances, and can suppress unnecessary exposure dose to normal tissues even when unstable breathing, abnormality in a detection system, or malfunction of software occurs. An object is to provide a safe radiotherapy device.

[0008]

In order to achieve the above object, the present invention detects a resting respiratory waveform in advance before irradiating the affected part with radiation, and determines a phase in which the affected part stops in the resting respiratory waveform. Setting a range, when irradiating the affected area, the current respiratory waveform is detected, in a radiation therapy apparatus that radiates radiation in synchronization with the phase range in the current respiratory waveform, the respiratory waveform at rest Calculating means for calculating a shift amount between the current respiratory waveform and the current respiratory waveform;
Radiation irradiation prohibiting means for prohibiting the irradiation of the radiation when the integrated value between the cycles is equal to or more than a predetermined value.

According to the present invention, radiation irradiation is prohibited when the integrated value of the difference between the respiratory waveform at rest and the current respiratory waveform during one cycle is equal to or greater than a predetermined value. This makes it possible to prohibit the irradiation of radiation even in the event of unstable respiration or abnormalities in the detection system, and to prevent unnecessary exposure of normal tissues. In order to achieve the above object, in the radiotherapy apparatus, detecting means for detecting a time width of a phase range for irradiating the radiation, and a time width detected by the detecting means or a predetermined tolerance for the time width. The time width to which time is added is set, and when a signal indicating the start point of the phase range in the current respiratory waveform is input, the irradiation time of radiation is measured from the input time point, and the measured irradiation time is A timer for outputting an irradiation prohibition signal for forcibly prohibiting the irradiation of the radiation when the set time width is exceeded.

According to the present invention, when the irradiation of the radiation is performed over the time width of the phase range for irradiating the radiation or the time width obtained by adding a predetermined allowable time to the time width, the irradiation of the radiation is forcibly performed. Outputs the irradiation prohibition signal to prohibit. This makes it possible to forcibly stop the radiation irradiation even in the case where the irradiation of the radiation does not stop due to a malfunction of the software or the like, thereby suppressing unnecessary exposure of normal tissues.

Further, in order to achieve the above object, in the radiation therapy apparatus, detecting means for detecting a maximum value and a minimum value of a respiratory waveform at rest in a phase range for irradiating the radiation, and detecting by the detecting means. Upper limit and lower limit based on the maximum value and the minimum value are set,
Comparing the signal level of the current respiratory waveform with the set upper and lower limits, and irradiating the radiation when the signal level of the current respiratory waveform exceeds the range between the upper and lower limits; And a comparing means for outputting an irradiation prohibition signal for forcibly prohibiting the irradiation.

According to the present invention, when the signal level of the current respiratory waveform exceeds the range between the upper limit and the lower limit based on the maximum and minimum values of the respiratory waveform at rest in the phase range in which the radiation is irradiated, radiation irradiation is performed. Output an irradiation prohibition signal for forcibly prohibiting. This makes it possible to forcibly stop the irradiation of radiation even when an abnormality of the respiration, the detection system, or the like occurs, thereby suppressing unnecessary exposure of normal tissues.

[0013]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a radiotherapy apparatus according to the present invention. FIG.
1 is an overall configuration diagram showing an embodiment of a radiotherapy apparatus according to the present invention.

The radiation therapy apparatus shown in FIG. 1 includes a strain gauge 2, an airflow transducer 4, a respiratory synchronization device 6, an electron beam control device 8, an electron accelerator 10, and a treatment gantry 12.
And a treatment table 14. As shown in the figure, a strain gauge 2 is installed on the body surface (for example, abdomen) of a patient lying on the treatment table 14. Alternatively, the airflow transducer 4 is attached to the mouth of the patient. A voltage or current signal proportional to the detected amount is output from these detectors.

The amount of physical change in the ecology due to respiration detected by the detector is input to the respiratory synchronization device 6. The respiratory synchronizing device 6 determines a period during which the respiratory moving organ in the respiratory signal waveform changes from inhalation to inhalation and a period in which inhalation changes to inhalation in a respiratory signal waveform, and outputs a signal for instructing irradiation or non-irradiation of radiation. I do. The details will be described later. The electron beam control device 8 inputs a signal from the respiratory synchronization device 6,
A control signal is output to the electron accelerator 10 based on this signal, and the electron accelerator 10 outputs an electron beam. The electron beam output from the electron accelerator 10 irradiates a high energy X-ray or an electron beam from the gantry 12. The electron accelerator 10 may be either a microtron or a linac, and instead of the electron accelerator 10, an ion accelerator that irradiates high energy charged particles such as protons may be used.

Next, the respiratory synchronizing device 6 in the above radiotherapy apparatus will be described. FIG. 2 is a configuration diagram showing an embodiment of the respiratory synchronization device 6. As shown in the figure, the respiratory tuning apparatus 6 receives a respiratory signal from the strain gauge 2 or the airflow transducer 4, detects a phase of the respiratory signal, detects an abnormality of the respiratory signal, and sets the respiratory signal to a predetermined phase. And, only when normal, the AND gate 40 outputs an irradiation permission signal (High level signal) for permitting radiation irradiation.

An AND gate 40 outputs an output signal (AND gate 3) indicating the logical product of the irradiation flag 26 and the normal flag 28.
6) and the signal levels of the output signals of the timer 30 and the comparator 38, and outputs an irradiation permission signal only when all of these signal levels are High level. The irradiation flag 26 and the normal flag 28 correspond to a CP described later.
The signal levels output from these are controlled by the determination process of U20, and are determined by arithmetic processing by software.

On the other hand, the timer 30 and the comparator 38 are controlled by a hardware configuration, and forcibly stop the irradiation when the operation of the CPU 20 is abnormal and the radiation irradiation runs away. First, the processing contents of the CPU 20 by software will be described. Strain gauge 2
Alternatively, the respiratory signal detected by the airflow transducer 4 is converted from an analog signal to a digital signal by the A / D converter 22 and input to the CPU 20.

Before starting treatment, the CPU 20 performs A / D conversion.
A respiratory waveform for a predetermined cycle is input from the strain gauge 2 or the airflow transducer 4 via the converter 22, and these respiratory waveforms are averaged. Then, the averaged respiratory waveform is recorded in the memory 24 as a past respiratory waveform.
The number of waveforms to be averaged is input by the operator from the input unit 42 in advance. Further, the CPU 20 displays the respiratory waveform on the display unit 44, and the starting point (sweep point) of each cycle of the respiratory waveform.
Is input from the input unit 42 to obtain the slope (increase or decrease) and signal level of the respiratory signal at this sweep point. Thereby, the CPU 20 determines the starting point of the respiratory waveform in each cycle from the respiratory waveform continuously input.

Then, the calculated past respiratory waveform is displayed on the display unit 44, and the operator is made to input the range of irradiation of radiation (irradiation permitted range) from the input unit 42. CPU
20 detects the slope (increase or decrease) and signal level of the respiratory signal at the start point (irradiation start point) and end point (irradiation end point) of the irradiation permission range input as shown in FIG.
These information are recorded in the memory 24.

At the same time, as shown in FIG. 4, the maximum value V _max and the minimum value V
It detects the _min, to detect the time length T _e of the radiation permitted range. Then, the thus detected maximum value V _max and the minimum value V _min in the tolerance V _t adds or subtracts, V
calculates _max + V _t and V _min -V _t, these values are set to the D / A converter 32.

Further, by adding the tolerance T _t in the time width T _e of irradiation permission range, calculates T _e + T _t, sets this value in the timer 30. After the preparation for the treatment is completed as described above, when performing the treatment, the CPU 20 transmits the strain gauge 2 or the airflow transducer 4 via the A / D converter 22.
, A respiratory waveform is sequentially input from the above, and a point where the inclination and the signal level of the respiratory signal at the above-mentioned irradiation start point and irradiation end point coincide with each other is detected to detect the irradiation permission range. Then, the irradiation flag 26 is turned on in the irradiation permission range (High level).
Set to. The details will be described later.

Further, the CPU 20 makes a determination to detect an abnormality of the respiratory signal input from the strain gauge 2 or the airflow transducer 4 shown below, and turns on the normal flag 28 (H
(high level) / off (low level). The normal flag 28 is for forcibly prohibiting radiation irradiation when a respiratory signal abnormality occurs, and radiation irradiation is possible only when both the irradiation flag 26 and the normal flag 28 are on.

Here, the determination of whether the breathing signal is normal or abnormal will be described. Abnormal respiratory signals are mainly classified into abnormalities in the detection system and abnormalities in the respiration of the patient. When performing a determination for detecting an abnormality in the detection system, the CPU 20 inputs a respiratory waveform for a predetermined period and calculates an average of these respiratory waveforms (hereinafter, this waveform is referred to as a current average respiratory waveform).
Then, a difference from the past respiratory waveform recorded in the memory 24 is obtained. This difference is calculated by the following equation, for example.

[0025]

[Equation 1] Here, f (t) indicates a past respiratory waveform, g (t) indicates a current average respiratory waveform, and T indicates a shorter cycle of the two respiratory waveforms f (t) and g (t). The area of the hatched portion shown in FIG.

If the difference S thus obtained is larger than a predetermined value, it is regarded that the detection system is abnormal and the normal flag 28
Turn off to prohibit irradiation. For example, when an abnormality such as looseness of the tape of the strain gauge 2 or clogging of the tube of the airflow transducer 4 occurs, the irradiation is prohibited by this determination. On the other hand, when determining to detect a patient's respiratory abnormality, the CPU 20 obtains a difference between the current average respiratory waveform and the sampling value of the current respiratory waveform. Then, as shown in FIG. 6, the difference is a predetermined value (V _d ).
If it is larger, it is regarded as a patient's respiratory abnormality, and the normal flag 28 is turned off to prohibit radiation irradiation. For example,
When unstable breathing such as hiccups or sneezing of the patient occurs, this determination prohibits radiation irradiation.

As described above, whether the respiratory signal is normal or abnormal is determined, and ON / OFF of the normal flag 28 is controlled. The processing procedure of the CPU 20 by this software will be described with reference to a flowchart. FIG. 7 is a flowchart showing a main processing procedure of the CPU 20.

When the CPU 20 starts operation, it first sets the operation mode to "under preparation" (step S2). And
It is determined whether or not to perform the treatment (step S4). If the treatment is not to be performed, the process is terminated.
The sweep point and the number of waveforms to be averaged are input from the input unit 42 (step S6). As described above, the sweep point indicates the start point of each cycle in the respiratory signal, and the number of waveforms to be averaged indicates the number of waveforms for calculating a past respiratory waveform.

Then, as described above, the past respiratory waveform is calculated, this waveform is displayed on the display unit 44, and the irradiation permission range is input from the input unit 42 according to the instruction of the operator (step S8). Next, it is determined whether or not the irradiation preparation has been completed (step S10). If the irradiation preparation has not been completed, the processing from step S6 to step S8 is repeated. , The current respiratory signal is input from the strain gauge 2 or the airflow transducer 4, and an averaged respiratory waveform is calculated. Then, the averaged respiratory waveform is stored as a past respiratory waveform (step S12).

After calculating the past respiratory waveform, the maximum value of the voltage (V
_max) and the minimum value (V _min) and the time width T of the irradiation permission range
_e is obtained, and a value obtained by adding an allowable range to these values is set in the D / A converter 32, the D / A converter 34, and the timer 30, respectively (step S14). After making the above settings,
The operation mode is set to "treatment" (step S16).
Then, the following interrupt processing is repeatedly executed until the end of the treatment is designated. If the end of the treatment is specified, the process returns to step S2.

Next, the interrupt processing will be described.
FIG. 8 is a flowchart showing the procedure of the interrupt processing. When the interruption process is started, first, a respiration signal is sampled from the strain gauge 2 or the airflow transducer 4 (Step S20). When the input signal level indicates an abnormal value, the normal flag 28 is set to off (step S22), and the irradiation flag 26 is set to off (step S25).

When the value is normal, it is judged whether or not the current sampling point is the sweep point (step S26). In the case of the sweep point, the process first proceeds to step S28 to determine whether the detection system is normal or abnormal, and then to step S38.
Then, it is determined whether the patient is breathing normally or abnormally. On the other hand, if it is not the sweep point, the flow shifts to step S38 to determine only whether the patient is normal or abnormal.

First, the processing when the current sampling point is not the sweep point will be described. In this case, step S
Then, it is determined whether the operation mode is “treatment” or not (38). If the operation mode is not “treatment”, the irradiation flag 26 is turned off (step S40). On the other hand, when the operation mode is “treatment”, it is determined whether or not the difference between the current respiratory waveform sampling value and the current average respiratory waveform is larger than a predetermined value as described above (step S42).
If the difference is larger than the predetermined value, the normal flag 28 is turned off (step S24), and then the irradiation flag 26 is turned off (step S25). Conversely, when the difference is equal to or smaller than the predetermined value, it is determined whether or not the current sampling point of the respiratory waveform is within the irradiation permission range (step S44), and if it is within the irradiation permission range, the irradiation flag 26 is turned on (step S44). S46), if outside the irradiation permission range, the irradiation flag 26 is turned off (step S25).

Next, the processing when the current sampling point is the sweep point in step S26 will be described. In this case, the process proceeds to step S28, and the current average respiratory waveform is calculated as described above. And the operation mode is "
It is determined whether or not the treatment is “treatment” (step S30). If the operation mode is not “treatment”, the process proceeds to step S38. If the operation mode is “treatment”, the current average respiratory waveform and the current It is determined whether the difference S from the past respiratory waveform is greater than a predetermined value (step S32), and if so, the normal flag 28 is turned off (step S2).
4), turn off the irradiation flag 26 (step S2)
5). If the difference S is equal to or smaller than the predetermined value, the normal flag 28 is turned on, and the process proceeds to step S38.

As described above, the CPU 20 sets the irradiation flag 26
ON / OFF of the normal flag 28 is controlled. Next, a timer 30 for preventing runaway of radiation irradiation by hardware
And the operation of the comparator 38 will be described. A timer 30 as described above, a value obtained by adding the time width T _e and tolerance T _t of irradiation permission range is set. As shown in FIG. 9, the timer 30 inputs the output signal of the AND gate 36 from the gate, and when this signal changes from the Low level to the High level, outputs the High level only during the time T _e + T _t input from the CPU 20. And time T _e + T _t
Is reset to Low level after elapse. That is, the timer 30 outputs a low level signal to the AND gate 40 when the radiation irradiation is performed beyond the irradiation permission range _Tt from the irradiation permission range due to an abnormal operation of the CPU 20 or the like, and the output signal of the AND gate 40 is output. Is forced to a Low level to stop radiation irradiation.

Further, the value V _max + V _t and V _min -V _t tolerance by adding or subtracting a V _t to the maximum value V _max and the minimum value V _min in the irradiation permitted range as described above CPU2
0 to D / A converters 32 and 34, respectively. D / A converter 32 outputs a digital signal of V _max + V _t and V _min -V _t respectively to the comparator 38 to an analog signal.

The comparator 38, a respiration signal from the strain gauge 2 is directly input in the form of analog signals, the V inputted from the D / A converter 32, 34 _max + V _t and V _min -V _t
Is determined to be within the signal level range. When the respiratory signal is within these signal level ranges, a High level signal is output to the AND gate 40, and when it is out of the range, a Low level signal is output to the AND gate 40. That is, when the respiratory signal exceeds the range obtained by adding the permissible range to the signal level range in the permissible irradiation range, the comparator 38 physically prevents radiation from being performed due to an abnormal operation of the CPU 20 or the like.

As described above, the irradiation tuning apparatus calculates the logical product of the irradiation flag 26 and the normal flag 28 controlled by software and the output of the timer 30 and the comparator 38 controlled by hardware.
The calculation is performed by the ND gate 40, and the irradiation permission signal is output only when all the outputs are at the High level. Thereby, even when an operation abnormality occurs in the CPU 20 operated by software, runaway irradiation of radiation is prevented by processing by hardware.

[0039]

As described above, according to the present invention, when unstable breathing, abnormality of the detection system, malfunction of software, etc. occur, irradiation of irradiation is forcibly prohibited, and runaway of irradiation is performed. Can be prevented. As a result, unnecessary exposure dose to normal tissues can be suppressed.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of a radiation irradiation apparatus according to the present invention.

FIG. 2 is a configuration diagram showing an embodiment of a respiratory synchronization device of the radiation irradiation apparatus according to the present invention.

FIG. 3 is an explanatory diagram showing an irradiation permission range of a respiratory waveform.

FIG. 4 is an explanatory diagram showing setting values of backup by hardware.

FIG. 5 is a diagram illustrating a method of determining an abnormality of a detection system.

FIG. 6 is a diagram showing a method for determining a respiratory abnormality of a patient.

FIG. 7 is a flowchart illustrating a procedure of a main process of a CPU;

FIG. 8 is a flowchart illustrating a procedure of an interrupt process of a CPU;

FIG. 9 is a timing chart showing the operation of the timer.

FIG. 10 is a configuration diagram of a strain gauge.

FIG. 11 is a configuration diagram of an airflow transducer.

[Explanation of symbols]

 2 ... Strain gauge 4 ... Airflow transducer 6 ... Respiratory tuning device 8 ... Electron beam control device 10 ... Electron accelerator 12 ... Therapeutic gantry 14 ... Treatment table 20 ... CPU 22 ... A / D converter 24 ... Memory 26 ... Irradiation flag 28 ... Normal flag 30 ... Timer 32 ... D / A converter 34 ... D / A converter 36 ... AND gate 38 ... Comparator 40 ... AND gate 42 ... Input unit 44 ... Display unit

Claims (3)

[Claims] 1. A method for detecting a respiratory waveform at rest in advance before irradiating the affected area, setting a phase range in which the affected area rests in the respiratory waveform at rest, and irradiating the affected area with radiation at present. In a radiation therapy apparatus for irradiating radiation in synchronization with the phase range of the current respiratory waveform, a calculating means for calculating a deviation amount between the resting respiratory waveform and the current respiratory waveform. If the integrated value of the deviation amount for one cycle is equal to or more than a predetermined value,
A radiation treatment apparatus comprising: radiation irradiation inhibiting means for inhibiting the irradiation of the radiation. 2. A method of detecting a resting respiratory waveform before irradiating the affected part with radiation, setting a phase range in which the affected part is stationary in the resting respiratory waveform, and setting a current range when irradiating the affected part with radiation. In a radiation therapy apparatus that detects the respiratory waveform of the present and synchronizes with the phase range in the current respiratory waveform to irradiate radiation, a detecting unit that detects a time width of the phase range to irradiate the radiation, and the detecting unit When the detected time width or the time width obtained by adding a predetermined allowable time to the time width is set, and a signal indicating the start point of the phase range in the current respiratory waveform is input, radiation from the input time point is detected. A timer for measuring an irradiation time and outputting an irradiation prohibition signal for forcibly prohibiting the irradiation of the radiation when the measured irradiation time exceeds the set time width. Radiation therapy equipment to be collected. 3. A method of detecting a resting respiratory waveform in advance before irradiating the affected part with radiation, setting a phase range in which the affected part is stationary in the resting respiratory waveform, and setting a current range when irradiating the affected part with radiation. A radiation therapy apparatus that irradiates radiation in synchronization with the phase range of the current respiratory waveform, and detects a maximum value and a minimum value of a respiratory waveform at rest in the phase range of irradiating the radiation. Detecting means, an upper limit value and a lower limit value based on the maximum value and the minimum value detected by the detecting means are set, and the signal level of the current respiratory waveform and the set upper limit value and the lower limit value are set. And comparing means for outputting an irradiation prohibition signal forcibly prohibiting the irradiation of the radiation when the signal level of the current respiratory waveform exceeds the range between the upper limit and the lower limit. A radiotherapy apparatus comprising: