CN116943050A - Terminal detector signal generating device and method for particle therapy - Google Patents
Terminal detector signal generating device and method for particle therapy Download PDFInfo
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- A61N5/00—Radiation therapy
- A61N5/10—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy
- A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head
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- A61N5/1001—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy using radiation sources introduced into or applied onto the body; brachytherapy
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- A61N5/1042—X-ray therapy; Gamma-ray therapy; Particle-irradiation therapy with spatial modulation of the radiation beam within the treatment head
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Abstract
The application provides a terminal detector signal generating device and a method for particle therapy, wherein the device comprises the following components: the core control module is used for analyzing the lattice scanning file to obtain the position of the beam spot in the beam to be simulated, the half-width of the beam and the beam dose, and calculating a first current value and a second current value of the beam to be simulated; the dose signal generation module is used for generating a first current signal according to the first current value; the strip position signal generation module is used for generating second current signals of different channels according to the second current value; the dose electronics module is used for converting the first current signal into a frequency signal and determining the beam dose of the actually generated beam according to the frequency signal; the stripe electronics module is used for converting second current signals of different channels into voltage signals, fitting the voltage signals and determining the position of the actually generated beam spot and the half-width of the beam; the data acquisition module is used for feeding back the position of the beam spot actually generating the beam, the half-width of the beam and the beam dose.
Description
Technical Field
The application relates to the technical field of particle therapy, in particular to a terminal detector signal generating device and method for particle therapy.
Background
In the particle therapy process, in order to irradiate a tumor focus according to a preset position and dose, a pencil beam scanning (Pencil Beam Scanning, PBS) system is required to accurately control the beam scanning process, so that the beam is deflected to a specified position, and the beam intensity is required to be adjusted to accurately control the irradiation dose, thereby ensuring the effectiveness and safety of the therapy.
At present, the following problems exist in the processes of debugging, commissioning and upgrading and reforming of a pencil beam scanning system: the above work must be performed depending on the existence of the actual beam, but in practice, whether the Treatment Control System (TCS), the treatment head electronics, and other related software and hardware systems are debugged, commissioned, or upgraded, is only related to the information fed back by the beam, and has no direct relation with the existence or non-existence of the beam itself.
The scheme of the prior art is as follows: and (3) monitoring the beam current in real time through a terminal detector striping ionization chamber and a dose ionization chamber, and determining the current beam spot position, half-width and dose of the beam current. After the beam passes through the strip ionization chamber, the strip electronic unit acquires signals of the strip ionization chamber, and the beam center position coordinate and the beam spot size are obtained through fitting and operation. Similarly, dose information may be obtained by integrating the signal from the dose ionization chamber by dose electronics.
However, the solution based on the prior art may limit the debugging and commissioning of the whole set of treatment head electronics and treatment control system, that is, when no actual beam exists, the pen-shaped beam scanning system cannot be operated, and the joint debugging with the Treatment Control System (TCS) cannot be performed, and since no feedback of beam position and dose information is provided after the treatment instruction is issued, the scanning process cannot be performed.
Disclosure of Invention
In view of the above, the present application provides a device and a method for generating a signal of a terminal detector for particle therapy, which are used for solving the technical problem that the pencil beam scanning system and the TCS system can only be modulated by an actual carrier beam in the prior art.
A first aspect of an embodiment of the present application provides a terminal detector signal generating apparatus for particle therapy, comprising: the core control module is used for analyzing the lattice scanning file issued by the particle therapy control system to obtain a first position, a first beam half-width and a first beam dose corresponding to each beam spot in the lattice, and calculating a first current value required by the beam generating the first beam dose and a second current value required by the beam generating the first position and the first beam half-width; the dose signal generation module is used for generating a first current signal according to the first current value; the strip position signal generation module is used for generating second current signals of different signal channels according to the second current value; the dose electronics module is used for converting the first current signal into a frequency signal and determining a second beam dose of the actually generated beam according to the frequency signal; the stripe electronics module is used for respectively converting second current signals of different signal channels into voltage signals, performing Gaussian fitting on the voltage signals and determining a second position of an actually generated beam spot and a second beam half-width; and the data acquisition module is used for feeding back the second position, the second beam half-width and the second beam dose to the particle therapy control system.
According to an embodiment of the present disclosure, a dose signal generating module comprises: a first current preset unit for inputting a current equal to the first current value; a first control unit for converting a current equal to the first current value from an analog quantity to a digital quantity and generating a first control instruction according to the current equal to the first current value; a first reference voltage source for generating a first reference value; the first digital-to-analog conversion unit is used for comparing the first reference value with the digital quantity and outputting a first analog quantity; the first high common mode differential amplifying unit is used for amplifying the first analog quantity; the first voltage-current conversion unit is used for performing voltage-current conversion on the amplified first analog quantity to generate a second current signal; the first negative feedback unit is used for sampling the first voltage of the output end of the first voltage-current conversion unit and feeding back the first voltage to the input end of the first high common mode differential amplification unit to control the first voltage-current conversion unit to output a first current signal of constant current.
According to an embodiment of the present disclosure, a striping position signal generation module includes a plurality of signal generation links and a connector for transmitting an output of each of the signal generation links to a striping electronics module, each of the signal generation links including: the second current preset unit is used for inputting a current with the same magnitude as the second current value; the second control unit is used for converting the current with the same magnitude as the second current value from analog quantity to digital quantity and generating a second control instruction according to the current with the same magnitude as the second current value; a second reference voltage source for generating a second reference value; the second digital-to-analog conversion unit is used for comparing the second reference value with the digital quantity and outputting a second analog quantity; the second high common mode differential amplifying unit is used for amplifying a second analog quantity; the second voltage-current conversion unit is used for carrying out voltage-current conversion on the amplified second analog quantity to generate a second current signal; the second negative feedback unit is used for sampling the second voltage of the output end of the second voltage-current conversion unit and feeding back the second voltage to the input end of the second high common-mode differential amplification unit to control the second voltage-current conversion unit to output a second current signal of constant current.
According to an embodiment of the present disclosure, a stripe electronics module includes a plurality of voltage-to-current conversion channels, each converting a second current signal of one channel into a voltage signal; each voltage-to-current conversion channel includes: a current-to-voltage converter for converting the second current signal into a negative voltage signal; and the inverting amplifying circuit is used for converting the negative voltage signal into a positive voltage signal to obtain a voltage signal.
According to an embodiment of the present disclosure, a current-to-voltage converter includes a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor; one end of the first resistor is connected with the reverse input end of the first operational amplifier, and the other end of the first resistor is used for inputting a second current signal; one end of the fifth resistor is connected with the positive input end of the first operational amplifier, and the other end of the fifth resistor is grounded; one end of the second resistor is connected with the reverse input end of the first operational amplifier, the other end of the second resistor is connected with one end of the third electric group in series, and the other end of the third electric group is connected with the output end of the first operational amplifier; one end of the fourth resistor is connected in parallel between the second resistor and the third resistor, and the other end of the fourth resistor is grounded, so that the T-shaped resistor feedback network is formed by the second resistor, the third resistor and the fourth resistor.
According to an embodiment of the present disclosure, an inverting amplification circuit includes a second operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, and a ninth resistor; one end of the sixth resistor is connected with the output end of the second operational amplifier, and the other end of the sixth resistor is connected with the reverse input end of the second operational amplifier; one end of the seventh resistor is connected with the positive input end of the second operational amplifier, and the other end of the seventh resistor is grounded; one end of the eighth resistor is connected with the reverse input end of the second operational amplifier, and the other end of the eighth resistor is connected with the output end of the second operational amplifier; one end of the ninth resistor is connected with the output end of the second operational amplifier, and the other end of the ninth resistor is used for outputting a positive voltage signal.
According to the embodiment of the disclosure, the current range of the second current signal input by the slitting electronic module is 10 pA-100 nA, and the voltage range of the output voltage signal is-20 mV-2V.
According to an embodiment of the present disclosure, the relative magnitudes of the current values of the second current signals of the different signal channels generated by the stripe position signal generating module satisfy a gaussian function distribution, and the maximum current value among the current values of the second current signals of the different signal channels does not exceed a preset current threshold.
According to an embodiment of the present disclosure, 256 signal channels are distributed at most in a horizontal direction, and 256 signal channels are distributed at most in a vertical direction.
A first aspect of an embodiment of the present application provides a method for generating a terminal detector signal for particle therapy, including: analyzing a dot matrix scanning file issued by a received particle therapy control system to obtain a first position, a first beam half-width and a first beam dose corresponding to each beam spot in a dot matrix, and calculating a first current value required by a beam generating the first beam dose and a second current value required by the beam generating the first position and the first beam half-width; generating a first current signal according to the first current value; generating a second current signal of the different signal channels according to the second current value; converting the first current signal into a frequency signal, and determining a second beam dose of the actually generated beam according to the frequency signal; converting second current signals of different signal channels into voltage signals respectively, performing Gaussian fitting on the voltage signals, and determining a second position of an actually generated beam spot and a second beam half-width; and feeding back the second position, the second beam half-width and the second beam dose to the particle therapy control system.
According to the terminal detector signal generating device and the terminal detector signal generating method for particle therapy, provided by the embodiment of the application, at least the following technical effects can be realized:
the terminal detector signal generating device is used for simulating the output of the analog beam current and adjusting other related systems, so that the problem that the current pencil beam scanning control system and the TCS system are debugged under the beam loading condition is solved, and the two systems can be debugged under the off-line condition. In addition, other related systems are regulated through the simulated beam current, so that inconvenience caused by the reasons of the beam current (such as the influence of unstable beam current on a test result and incapability of simultaneously constructing the dose in a factory) can be eliminated, and the whole debugging process is more convenient and flexible.
Drawings
The above and other objects, features and advantages of the present application will become more apparent from the following description of embodiments of the present application with reference to the accompanying drawings, in which:
fig. 1 schematically illustrates a block diagram of a terminal detector signal generating device for particle therapy according to an embodiment of the present disclosure.
Fig. 2 schematically illustrates a circuit schematic of a high-precision weak current source according to an embodiment of the present disclosure.
Fig. 3 schematically illustrates a block diagram of a dose signal generating module according to an embodiment of the present disclosure.
Fig. 4 schematically illustrates a block diagram of a split position signal generation module according to an embodiment of the present disclosure.
Fig. 5 schematically illustrates a circuit configuration diagram of a striping electronics module according to an embodiment of the present disclosure.
Fig. 6 schematically illustrates a flow chart of a terminal detector signal generation method for particle therapy, according to an embodiment of the present disclosure.
Fig. 7 schematically illustrates a flowchart of a method of commissioning and operation of a pencil beam scanning system employing a terminal detector signal generating device in accordance with an embodiment of the present disclosure.
Fig. 8 schematically illustrates a high precision weak range constant current source circuit diagram according to an embodiment of the present disclosure.
Detailed Description
The present application will be further described in detail below with reference to specific embodiments and with reference to the accompanying drawings, in order to make the objects, technical solutions and advantages of the present application more apparent. It will be apparent that the described embodiments are some, but not all, embodiments of the application. All other embodiments, which can be made by those skilled in the art based on the embodiments of the application without making any inventive effort, are intended to be within the scope of the application.
The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The terms "comprises," "comprising," and/or the like, as used herein, specify the presence of stated features, steps, operations, and/or components, but do not preclude the presence or addition of one or more other features, steps, operations, or components.
In the present application, unless explicitly specified and limited otherwise, the terms "mounted," "connected," "secured," and the like are to be construed broadly and include, for example, either permanently connected, removably connected, or integrally formed therewith; may be mechanically connected, may be electrically connected or may communicate with each other; can be directly connected or indirectly connected through an intermediate medium, and can be communicated with the inside of two elements or the interaction relationship of the two elements. The specific meaning of the above terms in the present application can be understood by those of ordinary skill in the art according to the specific circumstances.
In the description of the present application, it should be understood that the terms "longitudinal," "length," "circumferential," "front," "rear," "left," "right," "top," "bottom," "inner," "outer," and the like indicate an orientation or a positional relationship based on that shown in the drawings, merely for convenience in describing the present application and simplifying the description, and do not indicate or imply that the subsystem or element in question must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present application.
Like elements are denoted by like or similar reference numerals throughout the drawings. Conventional structures or constructions will be omitted when they may cause confusion in the understanding of the application. And the shape, size and position relation of each component in the figure do not reflect the actual size, proportion and actual position relation. In addition, in the present application, any reference signs placed between parentheses shall not be construed as limiting the claim.
Similarly, in the foregoing description of exemplary embodiments of the application, various features of the application are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various disclosed aspects. The description of the terms "one embodiment," "some embodiments," "example," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the application. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiments or examples. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.
Furthermore, the terms "first," "second," and the like, are used for descriptive purposes only and are not to be construed as indicating or implying a relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defining "a first" or "a second" may explicitly or implicitly include one or more such feature. In the description of the present application, the meaning of "plurality" means at least two, for example, two, three, etc., unless specifically defined otherwise.
Fig. 1 schematically illustrates a block diagram of a terminal detector signal generating device for particle therapy according to an embodiment of the present disclosure.
As shown in fig. 1, the terminal detector signal generating device comprises a core control module, a dose signal generating module, a stripe position signal generating module, a dose electronics module, a stripe electronics module and a data acquisition module. The input ends of the slitting position signal generating module and the dosage signal generating module are connected with the core control module, and the respective output ends are respectively connected with the slitting electronics module and the dosage electronics connecting module; the output ends of the slitting electronic module and the dosage electronic module are directly connected with the treatment control system.
The core control module is used for analyzing the lattice scanning file issued by the particle therapy control system to obtain a first position, a first beam half-width and a first beam dose corresponding to each beam spot in the lattice, and calculating a first current value required by the beam generating the first beam dose and a second current value required by the beam generating the first position and the first beam half-width.
The dose signal generation module is used for generating a first current signal according to the first current value.
And the striping position signal generation module is used for generating second current signals of different signal channels according to the second current value.
The dose electronics module is used for converting the first current signal into a frequency signal and determining a second beam dose of the actually generated beam according to the frequency signal.
The stripe electronic module is used for respectively converting second current signals of different signal channels into voltage signals, performing Gaussian fitting on the voltage signals and determining the second position of the actually generated beam spot and the second beam half-width.
And the data acquisition module is used for feeding back the second position, the second beam half-width and the second beam dose to the particle therapy control system.
According to the embodiment of the disclosure, the terminal detector belongs to a gas detector, and the basic principle is that when a beam vertically strikes an ionization chamber, the beam passing through a split ionization chamber and a dose ionization chamber collides with gas in the ionization chamber, so that gas molecules are ionized to generate electron-ion pairs, negative high pressure applied to a cathode plate belt of the ionization chamber attracts positive ions, the electron-ion pairs are rapidly separated, and an anode plate serving as a position strip absorbs electrons. The more gas molecules are ionized at the position close to the beam, the stronger the current amplitude signal is induced on the strip at the corresponding position, and the current amplitude signal amplitude on the strip is also Gaussian distributed on the X-Y plane because the beam is enveloped into Gaussian distribution. The current induced on each position strip has limited amplitude, basically within the range of 10 pA-100 nA, belonging to weak current. Therefore, the current signals output by the slitting position signal generating module and the dosage signal generating module are weak current signals.
Based on this, embodiments of the present disclosure design a high-precision weak current source.
Fig. 2 schematically illustrates a circuit schematic of a high-precision weak current source according to an embodiment of the present disclosure.
As shown in fig. 2, according to the properties of the operational amplifier, it is possible to ignore the effect of the operational amplifier on the circuit itself:
from the above, it can be seen that the output current and the resistance R, R 1 、R 2 、R 4 、R 6 、R 8 、R 10 、R 11 The reference voltage source Vref and the load resistor Rload, so that constant current can be realized by selecting proper resistors and a reference source.
The operational amplifiers U1 and U2 form a high common mode input differential proportional amplifier, U3 is a voltage follower, U4 is an inverting amplifier, when the load is increased or the offset voltage of a detected instrument is increased, the voltage drop generated by the output current at the output end is increased, the output current is reduced, at the moment, the detection circuit detects the voltage drop of the output end, the circuit formed by U3 and U4 regulates the output voltage Vout according to the voltage drop, and the voltage on the precision resistor R is always equal to the reference voltage, namely Vout-vload=Vref, so that the output current is equal to Vref/R, and the constant current purpose is achieved.
Therefore, the dosage signal generation module and the striping position signal generation module are both modules comprising high-precision weak current sources.
Fig. 3 schematically illustrates a block diagram of a dose signal generating module according to an embodiment of the present disclosure.
As shown in fig. 3, the dose signal generating module includes a first current presetting unit, a first control unit, a first reference voltage source, a first digital-to-analog conversion unit, a first high common mode differential amplifying unit, a first voltage-to-current conversion unit and a first negative feedback unit.
The first current presetting unit is used for inputting a current with the same magnitude as the first current value.
The first control unit is used for converting the current with the same magnitude as the first current value from analog quantity to digital quantity and generating a first control instruction according to the current with the same magnitude as the first current value.
The first reference voltage source is used for generating a first reference value.
The first digital-to-analog conversion unit is used for comparing the first reference value with the digital quantity and outputting a first analog quantity.
The first high common mode differential amplifying unit is used for amplifying the first analog quantity.
The first voltage-current conversion unit is used for performing voltage-current conversion on the amplified first analog quantity to generate a second current signal.
The first negative feedback unit is used for sampling a first voltage at the output end of the first voltage-current conversion unit and feeding back the first voltage to the input end of the first high common mode differential amplification unit to control the first voltage-current conversion unit to output a first current signal of constant current. The first current signal is transmitted to the dose electronics through the coaxial connector for integral analysis of the beam dose signal.
In an embodiment of the disclosure, the control unit in the dose signal generating module may be a single chip microcomputer, and the differential amplifying unit of the first high common mode may be a precision operational amplifier. The input end of the first voltage-current conversion unit is connected with the first control unit, and the first control unit controls and selects the range output of the first voltage-current conversion unit.
With continued reference to fig. 2, specifically, according to the control command of the first control unit, the multiplexer ADG1206 is controlled to select the high-precision resistor for voltage-current conversion to realize current output of different ranges. The output end of the first voltage-current conversion unit is used for carrying out constant current output on one hand and is also connected with the input end of the first negative feedback unit. The first negative feedback unit is used for sampling the voltage of the output end of the first voltage-current conversion unit and is overlapped at the input end of the differential amplification unit of the first high common mode, so that a preset current value is accurately output.
In order to prevent noise from being introduced during measurement of weak current signals, the principle of frequency conversion of charge is generally purchased in the dose electronics, the input weak current signals are converted into frequency signals and then collected and analyzed, and a fixed charge quantity delta Q is discharged by an integrator every time a pulse is output by a monostable circuit in the electronics, so that the total pulse count N obtained by a counter is proportional to the input charge signals, namely, the relationship between the input charge quantity and the input current is as follows:
Q＝N×ΔQ
and also (b)
Q＝I×t
The input current is proportional to the frequency of the output pulse:
thus, for dose electronics the input current I and the output frequency F are proportional, with a proportionality coefficient Δq.
For example, C at a dose of 1Gy +6 The electron ion pairs excited by the particles through the dose ionization chamber generate 0.5X10 s at 300V corresponding electric field strength b pC charge amounts, for a dose electronics with a ΔQ of 0.5pC, yield 1×10 b Number of pulses, dose 1GyC assuming that the process is completed in unit time +6 The output frequency of the particle beam corresponding to the dose electronics is 1×10 b Hz. The input current of the corresponding dose ionization chamber is 500nA; therefore, the input current corresponding to the dose signal generating module can be reversely deduced according to the preset dose.
Fig. 4 schematically illustrates a block diagram of a split position signal generation module according to an embodiment of the present disclosure.
As shown in fig. 4, the principle of the stripe position signal generating module is consistent with that of the dose signal generating module, and the stripe position signal generating module comprises multiple signal generating links and connectors, wherein the connectors are used for transmitting the output of each signal generating link to the stripe electronic module to perform fitting analysis on beam position coordinates and half-width height.
Each signal generation link comprises a second current presetting unit, a second control unit, a second reference voltage source, a second digital-to-analog conversion unit, a second high common mode differential amplifying unit, a second voltage-current conversion unit and a second negative feedback unit.
And the second current presetting unit is used for inputting a current with the same magnitude as the second current value.
And the second control unit is used for converting the current with the same magnitude as the second current value from an analog quantity to a digital quantity and generating a second control instruction according to the current with the same magnitude as the second current value.
And a second reference voltage source for generating a second reference value.
And the second digital-to-analog conversion unit is used for comparing the second reference value with the digital quantity and outputting a second analog quantity.
And the second high common mode differential amplifying unit is used for amplifying the second analog quantity.
And the second voltage-current conversion unit is used for carrying out voltage-current conversion on the amplified second analog quantity to generate the second current signal.
The second negative feedback unit is used for sampling the second voltage of the output end of the second voltage-current conversion unit and feeding back the second voltage to the input end of the second high common-mode differential amplification unit to control the second voltage-current conversion unit to output a second current signal of constant current.
In an embodiment of the present disclosure, the stripe electronics module includes a plurality of voltage-to-current conversion channels, each converting a second current signal of one channel to a voltage signal. Each voltage-to-current conversion channel includes: the current-voltage converter is used for converting the second current signal into a negative voltage signal, and the inverting amplification circuit is used for converting the negative voltage signal into a positive voltage signal to obtain a voltage signal.
Fig. 5 schematically illustrates a circuit configuration diagram of a striping electronics module according to an embodiment of the present disclosure.
As shown in fig. 5, the current-to-voltage converter includes a first operational amplifier U1, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, and a fifth resistor R5. One end of the first resistor R1 is connected with the reverse input end of the first operational amplifier U1, and the other end of the first resistor R1 is used for inputting a second current signal. One end of the fifth resistor R5 is connected with the positive input end of the first operational amplifier U1, and the other end of the fifth resistor R is grounded. One end of the second resistor R2 is connected with the reverse input end of the first operational amplifier U1, the other end of the second resistor R2 is connected with one end of the third electric group R3 in series, and the other end of the third electric group R3 is connected with the output end of the first operational amplifier U1. One end of the fourth resistor R4 is connected in parallel between the second resistor R2 and the third resistor R3, and the other end of the fourth resistor R4 is grounded, so that the T-shaped resistor feedback network is formed by the second resistor R2, the third resistor R3 and the fourth resistor R4.
The inverting amplifier circuit includes a second operational amplifier U2, a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, and a ninth resistor R9. One end of the sixth resistor R6 is connected with the output end of the second operational amplifier U2, and the other end of the sixth resistor R6 is connected with the inverting input end of the second operational amplifier U2. One end of the seventh resistor R7 is connected with the positive input end of the second operational amplifier U2, and the other end of the seventh resistor R is grounded. One end of the eighth resistor R8 is connected with the reverse input end of the second operational amplifier U2, and the other end of the eighth resistor R8 is connected with the output end of the second operational amplifier U2. One end of the ninth resistor R9 is connected with the output end of the second operational amplifier U2, and the other end of the ninth resistor R is used for outputting a positive voltage signal Vout.
The current range of the second current signal input by the slitting electronic module is 10 pA-100 nA, and the voltage range of the output voltage signal is-20 mV-2V.
Further, since the beam envelope is gaussian, the current amplitude signal amplitude across the strip is also gaussian in the X-Y plane.
Providing voltage amplitude data (X) in the X direction of the striped ionization chamber i ，y i ) (i=1, 2,3, … n) can be described by a gaussian function (where X is the position of the X-direction stripe and y is the voltage amplitude induced on the corresponding stripe):
in which the sign parameter y max 、x max And S is the peak value, the peak position and the half-width of the Gaussian curve respectively, and the natural logarithm is taken for the two passes of the above formula, and is as follows:
order the
And considering all data, the above formula can be expressed in a matrix form as:
can be abbreviated as:
Z＝XB
according to the least square principle, the generalized least square solution of the matrix B is:
B＝(X Γ X) -1 X 1 Z
then, the parameter y to be estimated is obtained according to the above method max 、x max And S, obtaining characteristic parameters of the Gaussian function.
And carrying out fitting treatment on the position of the beam by adopting a Gaussian fitting method, and obtaining beam information such as the position of the beam spot, the size of the beam spot and the like according to 256 position signal fitting, wherein the beam information is in the range of 200mm multiplied by 200mm, 256 position signal channels are distributed in the horizontal direction, 256 position signal channels are distributed in the vertical direction, the position accuracy of the beam can reach +/-0.5 mm through Gaussian fitting, and the accuracy requirement can be completely met due to the fact that the error allowable range is 1 mm.
Similarly, the characteristic parameter y can be known from the Gaussian function L max 、x max S and x i The relative voltage amplitude and the relative current intensity corresponding to 256 paths of strips are obtained according to the beam spot position, the beam spot size and other beam current information of the target beam.
According to the Gaussian function, current signals corresponding to different strips are obtained by reverse thrust, and are input to a current preset unit in the strip position signal generation module, so that the strip position signal generation module divides according to GaussianDistributing an output current signal; for the stripe electronics, as long as the relative magnitude of the output current values of each channel of the stripe position signal generating module only meets the distribution of a Gaussian function, the absolute magnitude of the output current value of each channel is not required, because the absolute magnitude of the current has no influence on the beam spot position and the half-width of the beam spot given by the final Gaussian fitting, only the maximum value y is required to be set max The preset current threshold is a default value and is not exceeded, and may be 2V, for example.
Based on the same inventive concept, embodiments of the present disclosure also provide a terminal detector signal generation method for particle therapy.
Fig. 6 schematically illustrates a flow chart of a terminal detector signal generation method for particle therapy, according to an embodiment of the present disclosure.
As shown in fig. 6, the terminal detector signal generation method for particle therapy may include operations S610 to S660, for example.
In operation S610, the lattice scan file issued by the received particle therapy control system is parsed to obtain a first position, a first beam half-width and a first beam dose corresponding to each beam spot in the lattice, and a first current value required by the beam generating the first beam dose and a second current value required by the beam generating the first position and the first beam half-width are calculated.
In operation S620, a first current signal is generated according to a first current value;
in operation S630, a second current signal of a different signal path is generated according to the second current value.
In operation S640, the first current signal is converted into a frequency signal, and a second beam dose of the actually generated beam is determined according to the frequency signal.
In operation S650, the second current signals of the different signal channels are respectively converted into voltage signals, and the voltage signals are subjected to gaussian fitting to determine the second position of the actually generated beam spot and the second beam half width.
In operation S660, the second position, the second beam half-width and the second beam dose are fed back to the particle therapy control system.
Fig. 7 schematically illustrates a flowchart of a method of commissioning and operation of a pencil beam scanning system employing a terminal detector signal generating device in accordance with an embodiment of the present disclosure.
As shown in fig. 7, the debugging and operation flow of the pencil beam scanning system by using the terminal detector signal generating device is as follows:
the first step, a Treatment Control System (TCS) sends the set lattice scanning file to an accelerator control system and a terminal detector signal generating device at the same time, the accelerator control system does not do any operation, namely no beam is led out to a treatment head, and a core control module of the terminal detector signal generating device analyzes after receiving the scanning file to obtain information such as the position, the half-width of the beam, the dosage and the like corresponding to each point in a lattice.
And secondly, the core control module calculates current signals required by each channel of the dose signal generating module and the striping position generating module according to the dot matrix scanning file data, and transmits the analyzed current signals to current presetting units of the two modules.
And thirdly, the dose signal generating module and the slitting position generating module generate current signals which are identical to the set values according to the set current preset values, and send the generated current signals to the dose electronics and the slitting electronics.
Fourth, the dose electronics converts the input current signals into frequency signals, the stripe electronics converts the input current signals of different channels into voltage signals, gaussian fitting analysis is carried out on the voltage signals, information such as the position, half-width and the like of beam spots is given, and the information is fed back to a Treatment Control System (TCS).
Fifthly, the treatment control system compares the fed back beam information with the preset beam demand in real time, if the position and the half-width of the beam spot are in an error range compared with the preset value, the flow is continued until the dose of the point reaches a set value, and the next point is switched to continue until all lattice programs are executed; and if the fed back position and half-width of the beam spot exceed the error range of the preset value, the flow is automatically ended in linkage response.
It should be noted that, where the method embodiment portion is not fully detailed, please refer to the apparatus embodiment portion, and no further description is given here.
Fig. 8 schematically illustrates a high precision weak range constant current source circuit diagram according to an embodiment of the present disclosure.
In a typical embodiment of the present disclosure, the precision operational amplifier employs ICL7650, and an integrating capacitance with a 1pF accuracy of ±0.1 pF. The circuit diagram of the comparator is shown in fig. 8, and the high-precision digital-to-analog converter chip AD9744 and the reference voltage source ADR130BUJZ, the multiplexer ADG1206 are adopted to ensure the stability of the high-precision weak range constant current source.
According to the terminal detector signal generating device and the terminal detector signal generating method for particle therapy, which are provided by the embodiment of the disclosure, the problem that the current pencil beam scanning control system and the TCS system are debugged under the beam loading condition is solved by designing the pencil beam scanning beam current terminal detector signal generating device, so that the two systems can be debugged under the off-line condition; the terminal detector signal generating device is used for simulating the output of the analog beam and adjusting other related systems, so that inconvenience caused by the reasons of the beam itself (such as the influence of the unstable beam on the test result and the incapability of simultaneous construction of doses in a factory) can be eliminated, and the whole debugging process is more convenient and flexible. The designed high-precision weak current source can accurately generate current smaller than 100nA, and can simulate the whole flow generated by the beam flow more truly, so that the off-line debugging of a related system is more practical and reliable; at most 256 position signals (512 can be generated in one-dimensional direction and two-dimensional direction), the 512 position signals can cover the whole beam scanning space, and beam information of each position can be simulated more comprehensively and accurately; through Gaussian fitting reverse calculation, current signals on different channels on the strip ionization chamber are given, and the current signals enter the strip electronics and then can be subjected to Gaussian fitting or gravity center method to obtain the designated beam position coordinates and half-width, so that the setting information and calculation result of the simulated beam are more approximate. The simulation beam current of the corresponding position and dose can be generated in real time according to the beam current irradiation position and dose instruction given by the treatment control system, the whole test flow can be automatically executed according to the actual beam current switch signal and the linkage system, and the whole process is completely consistent with the carrier beam debugging process, so that the joint debugging efficiency of the whole system is higher.
The foregoing is merely a specific embodiment of the present application, and the scope of the present application is not limited thereto. Any changes or substitutions made within the spirit and principles of the present application should be construed as falling within the scope of the present application. Therefore, the protection scope of the application is subject to the protection scope of the claims.
Claims (10)
1. A terminal detector signal generating device for particle therapy, comprising:
the core control module is used for analyzing a dot matrix scanning file issued by the particle therapy control system to obtain a first position, a first beam half-width and a first beam dose corresponding to each beam spot in a dot matrix, and calculating a first current value required by a beam generating the first beam dose and a second current value required by the beam generating the first position and the first beam half-width;
the dose signal generation module is used for generating a first current signal according to the first current value;
the strip position signal generation module is used for generating second current signals of different signal channels according to the second current values;
the dose electronics module is used for converting the first current signal into a frequency signal and determining a second beam dose of the actually generated beam according to the frequency signal;
the stripe electronics module is used for respectively converting the second current signals of different signal channels into voltage signals, performing Gaussian fitting on the voltage signals and determining the second position of the actually generated beam spot and the second beam half-width;
and the data acquisition module is used for feeding back the second position, the second beam half-width and the second beam dose to the particle therapy control system.
2. The terminal detector signal generating device for particle therapy of claim 1, wherein the dose signal generating module comprises:
a first current preset unit for inputting a current equal to the first current value;
a first control unit for converting a current equal to the first current value from an analog quantity to a digital quantity and generating a first control instruction according to the current equal to the first current value;
a first reference voltage source for generating a first reference value;
the first digital-to-analog conversion unit is used for comparing the first reference value with the digital quantity and outputting a first analog quantity;
the first high common mode differential amplifying unit is used for amplifying the first analog quantity;
the first voltage-current conversion unit is used for performing voltage-current conversion on the amplified first analog quantity to generate the second current signal;
and the first negative feedback unit is used for sampling the first voltage of the output end of the first voltage-current conversion unit and feeding back the first voltage to the input end of the first high common mode differential amplification unit to control the first voltage-current conversion unit to output the first current signal of constant current.
3. The terminal detector signal generating device for particle therapy of claim 1, wherein the stripe location signal generating module comprises a plurality of signal generating links and a connector for transmitting an output of each of the signal generating links to the stripe electronics module, each of the signal generating links comprising:
a second current preset unit for inputting a current equal to the second current value;
a second control unit for converting the current equal to the second current value from an analog quantity to a digital quantity and generating a second control instruction according to the current equal to the second current value;
a second reference voltage source for generating a second reference value;
the second digital-to-analog conversion unit is used for comparing the second reference value with the digital quantity and outputting a second analog quantity;
the second high common mode differential amplifying unit is used for amplifying the second analog quantity;
the second voltage-current conversion unit is used for carrying out voltage-current conversion on the amplified second analog quantity to generate a second current signal;
and the second negative feedback unit is used for sampling the second voltage of the output end of the second voltage-current conversion unit and feeding back the second voltage to the input end of the second high common-mode differential amplification unit to control the second voltage-current conversion unit to output the second current signal of constant current.
4. The end detector signal generating device for particle therapy of claim 1, wherein said stripe electronics module comprises a plurality of voltage-to-current conversion channels, each converting said second current signal of one channel into a voltage signal;
each voltage-to-current conversion channel includes:
a current-to-voltage converter for converting the second current signal into a negative voltage signal;
and the inverting amplifying circuit is used for converting the negative voltage signal into a positive voltage signal to obtain the voltage signal.
5. The end detector signal generating device for particle therapy of claim 4, wherein the current to voltage converter comprises a first operational amplifier, a first resistor, a second resistor, a third resistor, a fourth resistor, and a fifth resistor;
one end of the first resistor is connected with the reverse input end of the first operational amplifier, and the other end of the first resistor is used for inputting the second current signal;
one end of the fifth resistor is connected with the positive input end of the first operational amplifier, and the other end of the fifth resistor is grounded;
one end of the second resistor is connected with the reverse input end of the first operational amplifier, the other end of the second resistor is connected with one end of the third electric group in series, and the other end of the third electric group is connected with the output end of the first operational amplifier;
one end of the fourth resistor is connected in parallel between the second resistor and the third resistor, the other end of the fourth resistor is grounded, and the second resistor, the third resistor and the fourth resistor form a T-shaped resistor feedback network.
6. The end detector signal generating device for particle therapy of claim 5, wherein the inverting amplification circuit comprises a second operational amplifier, a sixth resistor, a seventh resistor, an eighth resistor, and a ninth resistor;
one end of the sixth resistor is connected with the output end of the second operational amplifier, and the other end of the sixth resistor is connected with the reverse input end of the second operational amplifier;
one end of the seventh resistor is connected with the positive input end of the second operational amplifier, and the other end of the seventh resistor is grounded;
one end of the eighth resistor is connected with the reverse input end of the second operational amplifier, and the other end of the eighth resistor is connected with the output end of the second operational amplifier;
and one end of the ninth resistor is connected with the output end of the second operational amplifier, and the other end of the ninth resistor is used for outputting the positive voltage signal.
7. The terminal detector signal generating apparatus for particle therapy as claimed in any one of claims 4 to 6, wherein the second current signal inputted from the stripe electronic module has a current range of 10pA to 100nA and the voltage signal outputted from the stripe electronic module has a voltage range of-20 mV to 2V.
8. The terminal detector signal generating apparatus for particle therapy as claimed in claim 1, wherein the relative magnitudes of the current values of the second current signals of the different signal channels generated by the strip position signal generating module satisfy a gaussian function distribution, and a maximum current value among the current values of the second current signals of the different signal channels does not exceed a preset current threshold.
9. The terminal detector signal generating apparatus for particle therapy as claimed in claim 1, wherein 256 signal channels are distributed at maximum in a horizontal direction and 256 signal channels are distributed at maximum in a vertical direction.
10. A terminal detector signal generation method for particle therapy, comprising:
analyzing a dot matrix scanning file issued by a received particle therapy control system to obtain a first position, a first beam half-width and a first beam dose corresponding to each beam spot in a dot matrix, and calculating a first current value required by generating a beam of the first beam dose and a second current value required by generating the beam of the first position and the first beam half-width;
generating a first current signal according to the first current value;
generating second current signals of different signal channels according to the second current value;
converting the first current signal into a frequency signal, and determining a second beam dose of the actually generated beam according to the frequency signal;
converting the second current signals of different signal channels into voltage signals respectively, performing Gaussian fitting on the voltage signals, and determining a second position of an actually generated beam spot and a second beam half-width;
and feeding back the second position, the second beam half-width and the second beam dose to the particle therapy control system.
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