JPS5976A - High energy ct for radiation treatment - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] The present invention uses a radiation therapy machine such as a medical linear
The present invention relates to a device for so-called radiotherapy, which treats cancer by irradiating a patient with a lesion in the body with radiation. Among these, the so-called CT (computed
TomographyComputed Tomography
) This relates to an apparatus for obtaining images, using the images for radiation treatment planning, and for performing accurate positioning during treatment.

Conventionally, in this type of technology, a radiation therapy machine such as a medical linear scanner and a CT are separate and separate devices and are operated separately from each other. Therefore, it had the following drawbacks.

1. Since CT is used for diagnostic purposes, the operating rate for diagnostic purposes is high, making it difficult to find time to use it for treatment.

2. Conventional CT is an OCT image as a distribution of X-ray absorption coefficient obtained by a low-energy X-ray source with an energy of 12 CIKV class, so it is difficult to treat with a high-energy X-ray source of several MY class. It lacked accuracy when used directly for planning (especially dose distribution calculations).

3. It was extremely difficult to position the patient using the radiation therapy machine while maintaining the same body position and anatomical structure that was used to position the patient using CT. In particular, since CT is made for diagnostic use, it cannot be operated as if it had the same structure as a treatment machine, and even if a patient's photograph is taken with CT, it cannot be used for treatment as is. There were often cases where this was not possible.

In addition, a device for positioning that operates as if it had the same structure as a conventional radiation therapy machine, the so-called shoe 2
Rator? However, unlike CT, it is not possible to obtain a cross-sectional image of the patient with this device, and it is difficult to accurately position the lesion because it cannot be grasped three-dimensionally based on the anatomical structure inside the body. The drawback was that it was not possible. )Special request 1977
3-28515 (published in 1986-8623) Temple Shogo ≠, the above drawbacks 1. This is the ninth solution to solve 3 and 3. However, 2. However, this method had the disadvantages of requiring two sets of radiation sources and detectors, making it a complicated and expensive device, and creating new drawbacks such as complicated operation and difficult maintenance.

The purpose of the present invention is to solve the above-mentioned drawbacks, to facilitate radiation treatment planning (#il! distribution calculation and positioning), and to reproduce the same body position and anatomical structure during treatment as during planning. An object of the present invention is to provide a device that can be easily positioned to accurately absorb radiation to a patient's lesion, thereby minimizing radiation damage to other healthy tissues and improving the clinical results of treatment. .

To achieve said objective f: the high-energy CT for radiotherapy according to the present invention shares the same radiation source as the radiation source of the radiation therapy machine, obtains radiation of the same energy or the same radiation quality from this source, and performs the same treatment on the same patient. Positioning geometry and machine #i! )
In addition to the same functions as regular whole-body CT, it can take scanography from any angle, and in addition to the same functions as regular radiation therapy machines, it uses the same beam energy when taking CT scans. However, it is configured so that it can operate as a CT scanner by lowering the dose rate and emitting an X-ray beam of the required shape during CT imaging.

That is, in the present invention, a radiation source for treatment of a radiation therapy machine and C
By using the same radiation source for T, sharing exactly the same patient positioning mechanism, and embedding the CT detector in the conventional beam stopper of the treatment machine or by providing a new structure, it can be said to be the same as the treatment machine. It integrates with CT. To this end, we have developed a method for making effective use of the linear range of sensitivity of the CT detector by keeping the energy of the radiation from the radiation source the same and reducing the dose rate only during CT imaging. Add or create something new inside. In addition, if we focus on the functions of conventional treatment machines, we can add a so-called CT function to reconstruct and display images from the data of transmitted X-rays that have passed through the patient's body obtained from the detector. Be prepared. Furthermore, one of the functions of CT is so-called scanography (a bed on which a patient is placed is moved at a constant speed while emitting X-rays in the form of a thin slit to obtain a projection image that reproduces the positioning of the patient. It goes without saying that the above-mentioned simulator has the same functions as the above-mentioned simulator. The present invention utilizes the same principle as rotational therapy such as linear therapy in radiotherapy and CT in that radiation is irradiated by rotating a radiation source around the patient. The present invention performs the function of a CT in addition to the original function of a radiation therapy machine, but it is not a mere combination or combination of these two operations.
．． We created a new action motion that can be used as a simulator for treatment planning, an X-ray absorption coefficient in the X-ray energy region that can be used directly for dose distribution calculations, and an action motion that represents the anatomical structure as a distribution of electron density. The function is to maintain strict reproducibility of the set-up for each treatment of the patient, rather than making mistakes.

Hereinafter, the apparatus according to the present invention will be explained in more detail with reference to the drawings and the like.

FIG. 1 is a side view and a simple structural diagram of the inside of the device according to the embodiment of the present invention, and FIG. 2 is a side view of the device as seen from the right side to the left of the side view of FIG. This is a simple structural diagram. FIG. 3 is a front view of the CT image display device.

Most of the external appearance and structure shown in Figures 1 and 2 are the same as conventional or current radiation therapy machines (medical linear accelerators in this figure); The only difference is that an X-ray detector 11 is included.

Although not shown in the figure, circuits related to the X-ray detector 11 and other related devices are attached to the medical linear rack. The microwave oscillated by the klystron 1 passes through the circulator 2 and reaches the acceleration tube 4, where it accelerates the electron beam as a pulse emitted from the electron mirror 3.
It is accelerated to an energy of several M e V. (In this example, it is 10 MeV.) At 77, the target 5 is collided with, and the source 5 of X-rays having that energy irradiates the xsi patient 21. At this time, in order to obtain an arbitrary size and shape of the irradiation field of the X-rays irradiated to the patient, the length in the axial direction of the patient's body is adjusted by the collimator 6, and the width in the lateral direction of the body is adjusted by the collimator 61. . □The collimator 6 is adjusted to obtain a slice width with a constant thickness when this device is used as a CT. Although this is not shown in this diagram, the CT scan is performed from the treatment machine on the console.
When the button to switch to the function is pressed, settings are automatically made to obtain the slice thickness (for example, 1011II) at the irradiation site of the patient. At the same time, the collimator 61 is also fully opened (for example, 42 degrees) so as to cover the entire width of the patient. As a result, a normal beam system for obtaining the X-ray fan beam 9 has about 32 sub-fields when fully opened, so this device can obtain a wide irradiation field (42 tM) even if it has been modified. When setting up the patient 21 on the treatment bed T at a predetermined position, the patient 21 is moved vertically, horizontally, and vertically using the functions of the treatment bed as a normal treatment machine. When acquiring a CT image (this point is one of the most important points in the present invention), the same patient is set up at the same position that would be set up during treatment. Therefore, the operation of the treatment table may be exactly the same as in a conventional hospital. However, if the bed top on which the patient directly stands and the frame on which the top rests are made of metal, which is used in conventional treatment machines, artifacts will occur in both CT images, so these must be avoided. As shown in the figure, in the case of a single-support bed, materials other than metal that have sufficient strength include carbon graphite and other materials. For example, the American company Vaγtan's CTV-36
Such a material is used for the single support top plate of 0-3. The X-ray detector 11 is a detector based on the principle of so-called third generation OCT.

An ion chamber method, a scintillation crystal and a photomultiple, a scintillation crystal and a semiconductor amplification device, etc. may be used. However, it is most ideal to use a semiconductor detector that converts the X-rays directly into electrical signals through a surface barrier set of high-purity silicon crystals.

In this case, when using this device as a CT, there is an advantage that it can be used without significantly reducing the dose rate while maintaining the same high energy as in the case of full energy treatment.
Is this because the X-ray irradiation dose rate is linear from a small amount to a large amount? This is because detection can be performed while maintaining the

By the way, in order to use this device as both a treatment machine and a CT, the dose rate used as a treatment machine must be several hundred rads/mi.
n and the dose rate ralls/min used as CT,
Even if the gantry 8 that houses the radiation source 5 is rotated while the energy is maintained at a predetermined stable high energy level at slightly different dose rates and the patient is irradiated, the radiation remains unchanged even if the entire treatment is performed by CT imaging or rotational irradiation. It is necessary to obtain a stable output with no time change in rate. The reason for this is that during CT imaging, the radiation exposure to the patient must be kept as low as possible, and as mentioned above, the X-ray detector is saturated with radiation at a high dose rate. There is a technical reason why the X-ray intensity cannot be detected while maintaining linearity. To this end, when using this device as kcT, the following operations are performed.

First, a gantry 8 holding an X-ray source 5 and a detector 11
1. When emitting X-rays in pulses while rotating the patient 360 degrees, it is necessary to make it possible for an electron beam pulse to be emitted into the accelerator tube for every 1 degree of displacement of the gantry rotation. For that purpose, the gun is set so that the IJ rotation speed can be accurately controlled at a constant speed of 1 revolution per minute.

This is possible with the existing technology of conventional medical linear axes.

Also, the pulse of the electron beam emitted from the electronic mirror 3 is 3
It is precisely controlled to 60 pulses/min, that is, an integral multiple of 60 ppm, and a steering coil is installed at the connection between the accelerating tube and the electron mirror to thin out the pulses of the electron beam that enters the accelerating tube from the electron mirror. This makes it possible to accelerate an electron beam of exactly 60 ppH. This is done by controlling the oscillator of the pulse voltage generator applied to the cathode of the electron mirror and the circuit that drives the steering coil.

Second, the current value per pulse of the electron beam emitted from the electron mirror 3 must be reduced. This is done by controlling the bias voltage applied to the grid provided in the electronic mirror 3. Exactly the same means are used to make the energy of the linear strike variable.

Thirdly, the microwave power supplied to the accelerator tube is reduced in accordance with the electron beam current value reduced by the second means,
It must be controlled to be able to accelerate to a predetermined energy (for example, IOMV) and to be able to accelerate stably. To this end, the klystron 1 and its control device are controlled so that microwave power of a predetermined value obtained through calculation and experiment is oscillated.

This is exactly the same means used to vary the energy of the linear electron beam.

Next, a method of using the present device will be explained for a patient 21 (an example to be treated). First, this device uses the CT scanography function to clarify the location of the patient's lesion and the irradiation range. That is, the target volume is determined. To this end, we will make effective use of the system's imaging techniques using this device. Unlike general OCT, this device can obtain scanography from any gantry angle (i.e., irradiation angle from any direction), so this advantage can be effectively utilized to determine the target volume. It is possible to take photographs at the irradiation angle for treatment and determine the irradiation field range, etc. The embodiment shown in FIG. 3 shows an example in which the gantry angle is set slightly to the upper right, that is, the radiation source position is set slightly to the upper right, and scanography is taken. A graphical display 34 showing the irradiation range is obtained while determining the ditarget volume by looking at the scanography chart 33t of the CTT image display device 31.

The size, position, and shape can be arbitrarily determined by operating the levers and knobs attached to the CT chart display device 31. When performing multi-field irradiation, scanographic imaging is performed at gantry angles between each field to obtain sets of images 33 and 34 as many as the number between the fields. The usage described above is almost the same as that of conventional treatment simulators.

Second, this device utilizes the CT cross-sectional imaging function to confirm the location of the patient's lesion and clarify the irradiation range.

That is, the target volume in the transverse direction is determined. At this time, it goes without saying that operations such as determining and confirming the slice position can be performed using photographs obtained by scanography and the scale tube contained therein, as in ordinary CT. The embodiment shown in FIG. 3 shows an example in which the gantry angle f is set slightly to the upper right, the radiation source position is set slightly to the upper right, and the irradiation direction and irradiation range are set.

CT image chart display device 31 CTT image 32 + t- while looking 3
You can determine the irradiation angle and irradiation field width by operating the levers and knobs attached to the 35-ft graphic display that shows the irradiation field range. At this time, since it must be consistent with the irradiation angle and irradiation field width determined in the aforementioned scanography image 33 and the graphic display 34 showing the irradiation field range above it, the software automatically All checks are carried out and the operator is informed so that they can understand. When performing multi-field irradiation, the cancer between each field)
The width of the irradiation field is determined based on the angle within the IJ.

Third, dose distribution calculations are performed using all 90T images obtained with this device. It is well known that conventional OCT images can be used to calculate dose distributions, so we will not discuss them in detail. This method expresses the electron density distribution in the body as it is, and it has the feature that there is no need to incorporate uncertain elements such as approximate conversion from low-energy absorption coefficient (CT number) to electron density as in the conventional method. are doing. Further, it is not necessary to use a method such as approximation by extrapolation of electron density using the dual energy method. This device can perform CT scans with the same radiation quality as used for such treatments.
Even if we utilize only the features that allow us to calculate the dose distribution accurately and with theoretical consistency by obtaining the image (J?), it is valuable in itself. The optimal treatment plan for a given patient can be obtained by comparing the results of the determination of the irradiation field size and the irradiation field size.
Cancer in the hilum) IJ internal angular field dimensions.

In addition to dose, wedge filters, and other treatment parameters, it also includes information such as the position of the patient and the movement of the treatment table.

Fourthly, this device is used as a radiation therapy machine to perform treatment. At this time, it is of course necessary to set up the patient 21t on the treatment table 7 by placing it in the same position and posture as when using this device as a tCT, but in order to ensure accuracy or to confirm To take care 1. A major feature of this device is that it can be used again as a CT immediately before treatment.

As a result, a graphic display 34 showing the irradiation field range on the same scanography image 33 that was taken at the time of treatment planning, a CT image table 2 and a graphic display 3 showing the irradiation field range above it.
The patient is set up and the treatment machine is set up so as to obtain a treatment plan of 5. Both CT images are taken and compared with the treatment plan. Radiotherapy for the same patient is often divided into dozens of sessions over dozens of days and repeated using the exact same setup to maintain accurate reproducibility. It also has important effects that were not previously available. That is, 1. It is possible to not only accurately match the treatment plan in setting up the patient and setting up the radiation therapy machine, but also maintain accurate reproducibility in each treatment.

As explained above, the present invention has a radiation source with the same energy as that of the radiation therapy machine, and the same patient setup and treatment as during treatment by configuring the C'l having the same geometrical arrangement and mechanism of the patient setup. It has the effect of enabling treatment planning during machine setup, and provides an X-ray absorption coefficient distribution using high-energy X-rays that was previously unobtainable in order to accurately calculate dose distribution. Accuracy of matching with the treatment plan mentioned above in each radiation treatment.

This has the effect of maintaining reproducibility accuracy. The synergistic effect of these three effects contributes to improving the precision of radiotherapy that could not be obtained previously, and produces new effects that are useful for improving the clinical results of cancer treatment.

[Brief explanation of the drawing]

Fig. 1 is a side view and a simple internal structural diagram of an apparatus according to an embodiment of the present invention, and Fig. 2 is a side view and a simple internal structural diagram as viewed from the right side of Fig. 1 to the left side. FIG. FIG. 3 is a front view of the CT image display device. 1Φ...klystron 2...e-circulator 3...electronic mirror 4...acceleration tube 5--X-ray source 6..., collimator 7...treatment bed 8...gantry 9...X Ray fan beam 61...Collimator 11...X-ray detector 21...Fist patient 31...CT chart display device□ 32...CT chart 33...Fist scanography image 34...・Graphic display 35 showing the Φ irradiation range...Graphic display showing the irradiation range Patent applicant: NEC Corporation Representative Patent attorney: Hisashi Inoro

Claims (1)

[Claims] In high-energy CT for radiation therapy, it shares the same radiation source as that of the radiation therapy machine, obtains radiation of the same energy or quality from this source, and shares the same patient positioning geometry and mechanism. Do K, normal whole body C
In addition to the same functions as T, it can also take scanography from any angle, and in addition to the same functions as regular radiation therapy machines, CT
For radiation therapy, which is characterized by being configured to lower the dose rate while keeping the beam energy the same during imaging, and to emit an X-ray beam of the required shape during CT imaging, allowing operation as a CT scanner. High energy T0