JP6867670B2 - Microwave therapy device - Google Patents

Description

The present invention relates to a microwave therapy device.

The microwave therapy device is a hyperthermia therapy device that heats living tissues by radiating microwaves radiated from an antenna. Considering the frequency band of microwave treatment, it is possible to heat a deep part of a patient as compared with a treatment device using conductive heat such as a heater or radiant heat such as infrared rays. Further, the treatment can be performed even if the patient is wearing clothes or the like, and there is an advantage that the desired affected area can be thermally treated without taking off the clothes.

Here, in the conventional microwave therapy device, as shown in FIGS. 6 and 7, the AC power of AC100V is boosted by the high-voltage transformer 22, then rectified by the rectifier 23, and the voltage after the rectification is the voltage of the magnetron 24. It was generally supplied to the anode, and when the anode voltage of the magnetron 24 exceeded the oscillation voltage, a microwave was generated and finally radiated from the antenna 25 toward the patient.

JP 2015-119798 JP 2013-065406

The magnetron 24 used in the conventional microwave therapy device has a problem of unnecessary radiation peculiar to the magnetron 24. Specifically, magnetrons for microwave therapy generate microwaves in the 2450 MHz band on the anode body, but in reality, in addition to this fundamental wave, harmonic forces with frequencies that are integral multiples of that are also generated at the same time. There is. When this harmonic is radiated from the antenna 25, it is propagated to the outside including the human body in the same manner as the fundamental wave. In addition to harmonics, the unnecessary radiation of the magnetron 24 includes radiation of frequencies caused by the resonator structure inside the magnetron 24, radiation caused by an oscillation mechanism rising from noise, and the like. In order to suppress the unnecessary radiation, for example, as described in Prior Document 2, measures have been taken such as providing a choke for suppressing unnecessary radiation formed of a material in consideration of the coefficient of thermal expansion.

However, there is a mechanical limit to the suppression of the unnecessary radiation, which may cause a radio failure. In particular, in the case of irradiating a patient with microwaves for treatment, unlike a microwave oven, a method of shutting out leakage of unnecessary radiation with a housing structure cannot be expected, so unnecessary radiation is not required by a method other than the housing. It is necessary to control the leakage of radiation.
Further, the magnetron 24 is driven by using a device having a relatively large outer shape such as a high-voltage transformer, a heater transformer, and a high-voltage capacitor, and has a problem of miniaturization.

In order to solve the above problems, the microwave treatment device according to the present invention has an oscillator for generating microwaves, a transmission unit for supplying the microwaves produced by the oscillator to the antenna unit, and the transmission unit. The antenna is provided with a standing wave ratio measuring means for measuring the standing wave ratio, the antenna uses a semiconductor element for its switching control, and the value of the standing wave ratio obtained by the standing wave ratio measuring means. depending on, within a predetermined frequency range, as well as change its oscillation frequency, arranged said oscillator and the antenna unit in the same housing, and distribution of the cooling means of the semiconductor element between the antenna portion and the oscillator It is made up of.

According to the microwave therapy device according to the present invention, it is possible to provide an excellent frequency drift suppression performance and output stability, and it is possible to realize a microwave therapy device that effectively suppresses unnecessary radiation.

The figure which showed one Embodiment of the microwave therapy apparatus of this invention The figure which showed the antenna used in the same embodiment The figure which showed the arrangement of the heat radiation fin used in the same embodiment Circuit block diagram of microwave therapy device by semiconductor control of one embodiment of the present invention Application circuit configuration diagram of microwave therapy device by semiconductor control of the same embodiment The figure which showed the magnetron oscillation circuit of the conventional example Overview of the magnetron

An embodiment of the present invention will be described with reference to FIGS. 1 to 3. The microwave therapy device of the present invention has a semiconductor oscillator circuit 1, a directional coupler 2 connected to the semiconductor oscillator 1, and an antenna unit 3 for radiation. The semiconductor switching element in the semiconductor oscillator circuit 1 includes
Although it is possible to use Si (silicon) or GaAs (gallium arsenide), it is desirable to use GaN (gallium nitride) for higher efficiency. According to the semiconductor switching, there is no problem such as frequency radiation due to the internal resonator structure peculiar to the magnetron, so that the frequency occupied bandwidth can be suppressed to about one tenth of that of the magnetron method. It can be controlled with a high Q value.

On the other hand, medical microwave therapy equipment is assigned an electromagnetic field in the frequency range of 2400 MHz to 2500 MHz, and according to the JIS standard, for applicators connected by cables or waveguides. , It is stipulated that the voltage standing wave ratio (VSWR) must not exceed 1.5. Under these circumstances, an oscillator circuit using semiconductor switching with excellent Q value characteristics is desirable in order to suppress unnecessary radiation in bands other than 2400 MHz to 2500 MHz and at the same time keep VSWR within the specified value.

Further, in a treatment device in which a patch antenna is used close to the affected area, microwaves radiated to areas other than the affected area can be suppressed, but when semiconductor switching is used, it is relatively easy to change the frequency. Therefore, in the range of a predetermined frequency (2400 to 2500 MHz), the width and diameter of the patch antenna are roughly adjusted, and the frequency is actually changed so that the standing wave ratio etc. becomes the best. It is possible to make fine adjustments (following), and it is also possible to improve the productivity.

Specifically, the appropriate size of the patch electrode will have an outer diameter related to λ (wavelength) / 2, and in reality, the effective relative permittivity of the equipment (dielectric between the patch electrode and ground) will be determined. As ε, it will be designed with a size of λ / (ε1 / 2.2). Since the frequency range that can be used as a medical device is 2400 to 2500 MHz, if equipment with ε = 3 is used, the range from λ = 3.0 * 108 / f (frequency) to 34.64 to 36.09 mm. The patch electrode that best fits the outer diameter will be adjusted.
In addition, if the conventional magnetron method is used, unnecessary harmonics may be generated. Therefore, depending on the performance of the magnetron, electromagnetic waves may reach an unintended depth of the human body. By using it, the defect is corrected and the affected area can be treated correctly.

The efficiency loss of the semiconductor element is dissipated through the heat radiation fins 5 and the like attached to the semiconductor element. As shown in FIG. 3, the heat radiation fins 5 are arranged in the semiconductor element 1 and the antenna 3. By physically arranging them in between, it is possible to suppress the noise generated by switching from reaching the antenna, and it is possible to further improve the suppression of unnecessary radiation.

Hereinafter, an embodiment of the present invention will be described. In this embodiment, as shown in FIG. 4, in the microwave semiconductor oscillation circuit, the semiconductor switching element 13 serving as an amplifier and the signal generation unit 11 (VCO) capable of generating a signal and varying the signal with respect to the semiconductor switching element 13 : Voltage control oscillator), an amplifier 12 that adjusts the output of the signal generator 11, a gate voltage control circuit 16 provided on the input side of the semiconductor switching element, and a gate voltage control circuit 16 provided on the output side of the semiconductor switching element 13 for reflection and the like. It is composed of an isolator 14 for prevention, a directional coupler 15 (or a return loss bridge) for extracting reflected waves from a traveling wave, and a power supply circuit 17 for supplying power to the semiconductor switching element 13.

The signal generation unit 11 outputs a fundamental frequency in the microwave band, for example, 2.45 GHz, and the output is adjusted by the amplifier 12. The signals of the signal generator 11 and the amplifier 12 are switched and controlled by the semiconductor switching element 13 to amplify the electric power. FETs such as LD MOSFETs, GaAs FETs, and GaN FETs are used as the semiconductor switching element 13. The 2.45 GHz signal output from the signal generation unit 11 is applied to the gate of the FET, the drive voltage from the voltage supply unit is applied to the drain, and the amplified 2.45 GHz microwave is output from the antenna.

Further, the directional coupler 15 can take out a signal flowing on the transmission path separately as a traveling wave and a reflected wave. A directional coupler 15 is inserted into the transmission line between the antenna and the semiconductor oscillator, the voltage and current are taken out, the traveling wave power and the reflected wave power are measured respectively, and the power actually supplied to the antenna is calculated from the difference. Ask. The power of the traveling wave and the reflected wave taken out from the directional coupler 15 is converted by the analog-digital conversion circuit 18. The power is compared by the control circuit 16, and when the reflection is large, the voltage of the signal generation unit 11 is controlled so that the power of the reflected wave becomes small, and the oscillation frequency is in the range of 2.4 GHz to 2.5 GHz. Select the frequency at which VSWR is 1.5.

In addition, the good center frequency of VSWR in the distance between the antenna part and the human body is effective at an integral multiple of the antenna length (λ / 2) in the near field, and approaches the aerial radiation in the far field away from the human body. Stable around 2450MHz. The distance between the antenna and the affected area is λ / 4, λ / 2 (30 mm, 60 mm), which is an integral multiple of the antenna length, with the intention of suppressing unnecessary radiation as much as possible. Further, it is desirable that the antenna has a shape that takes into consideration the relative permittivity of the human body, and it is necessary to have an antenna shape that assumes the skin tissue. Therefore, a radiation plate with a relative permittivity of 61 mm, which is λ / 2 with an antenna wavelength of 122 mm, is used. The relative permittivity of fat etc. is 5.5, and 61 mm, which is λ / 2, is divided by the square root of this value to make one side, so the antenna is a radiation plate with a side of 26 mm. When adjusting VSWR, if necessary, 0.9% saline solution should be placed in a cylindrical container made of a low-loss material (for example, methacrylic resin) with a diameter of 20 cm and a length of 50 cm at a position assuming the affected area. A method of measuring various data using a state filled with water as a phantom is used.

In order to obtain the best VSWR value, it is desirable to connect the transmission line (coaxial cable) as short as possible, but when a magnetron is used, the drive circuit etc. is large, so the coaxial cable that is the transmission line Is required, and it is difficult to connect the magnetron directly to the antenna. In this regard, in this embodiment, by using the semiconductor switching element 13, the microwave output is stabilized and unnecessary radiation is reduced, and at the same time, miniaturization is possible. Therefore, it is possible to arrange the drive unit in the vicinity of the human body, and it is also possible to integrate the antenna unit and the drive unit, reduce the size, and enhance the mobility.

In addition, by adjusting the shape of the antenna and the distance between the antenna and the affected area, VSWR can be improved and unnecessary radiation can be reduced. When a patch antenna having a three-layer structure of plate-dielectric-conductor base plate is used, the radiation plate uses air as the dielectric, so the relative permittivity ε = 1 and the dimension is 61 mm, which is λ / 2. And. The distance between the antenna and the affected area is an integral multiple of the antenna length, but the distance is λ / 4 or λ / 2 with the intention of suppressing unnecessary radiation as much as possible. Specifically, it is set to 30 mm or 60 mm from Table 1. Table 1 shows how VSWR changes according to the distance from the antenna to the human body (10 mm to 60 mm) when the frequency is changed from 2200 to 2900 MHz.

In addition, the microwave therapy device is a hyperthermia device that radiates microwaves to living tissue to heat it, but when it is irradiated with low-power (10W) microwaves, it emits high-power (200W) microwaves. It is considered that there is a different effect on the living tissue (protein, etc.) as compared with the case of output. In this respect, the semiconductor oscillation method enables duty control by high-speed switching, and it is relatively easy to perform low output control and output control according to the patient's condition while suppressing ripple to 0.1% or less. .. Further, according to the semiconductor oscillation method, it is possible to switch between high output and low output alternately, for example, while controlling mainly low output, temporarily high output control at a desired time zone. It is also possible to control such as mixing, and more detailed output control is possible according to the patient's condition.

1 Semiconductor oscillator circuit 2 Directional coupler 3 Antenna 11 Signal generator 13 Semiconductor switching element 15 Directional coupler

Claims (1)

It is provided with an oscillator that generates microwaves, a transmission unit for supplying the microwaves produced by the oscillator to the antenna unit, and a standing wave ratio measuring means for measuring the standing wave ratio in the transmission unit. the oscillator uses a semiconductor element to the switching control, the according to the value of the standing wave ratio obtained by the standing wave ratio measuring means, within a predetermined frequency range, to change its oscillation frequency together with the oscillator and arranged in the same housing the antenna unit, a microwave treatment apparatus comprising a cooling unit of the semiconductor device in coordination between the antenna unit and the oscillator.

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