Dose rate monitor, system and method

Abstract

The present disclosure relates to a radiotherapy dose rate monitoring system comprising: an emission electrode configured to be impinged by radiotherapy radiation; a collection electrode configured to form an electrical circuit with the emission electrode; a current measurement device configured to measure a current through the emission and collection electrodes, the current being indicative of a dose of the radiotherapy radiation; and a chamber enclosing a gas. Secondary electrons emitted from the emission electrode provide a majority of the current.

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of medical devices. More specifically, embodiments of the present invention relate to systems and methods for measuring and monitoring the dose rate of therapeutic radiation. Background Technology

[0002] External beam radiotherapy can be used to treat a variety of cancers and non-malignant conditions. Typically, ionizing radiation, including photons (such as X-rays and gamma rays) and charged particles (such as protons and electrons), is directed to the region of interest. In many cases, this ionizing radiation is generated by linear or cyclotron accelerators.

[0003] Accurately measuring the dose of radiation during treatment is crucial. For example, radiation therapy is typically planned very precisely based on many factors, including tumor type, location and stage, and the patient's overall health. Generally, too much radiation can harm the patient, while too little radiation may fail to achieve the desired therapeutic effect.

[0004] Typically, ionization chambers can be used to measure radiation dose and / or dose rate based on radiation-induced ionization in a gas. A sample gas is enclosed in an ionization chamber between two electrodes. A radiation “beam” is directed through the ionization chamber before impacting the patient, causing some of the sample gas to ionize. Ionization typically produces negatively charged electrons and positively charged ions. A voltage applied to the electrodes, such as 500 volts, collects electrons at the positive electrode and positive ions at the negative electrode. The current collected by these electrodes is typically proportional to the radiation dose rate and can be measured to create a dose monitor. As long as the radiation ionizes only a small fraction of the gas, the current will be linearly related to the dose rate.

[0005] FLASH radiotherapy is an emerging radiotherapy regimen that appears to reduce radiation-induced toxicity while maintaining a tumor response similar to more conventional radiotherapy regimens. FLASH radiotherapy can be characterized by delivering a high radiation rate, such as greater than approximately 40 Gy / s, which allows the total radiotherapy treatment dose, or a large portion of the total radiation dose, to be delivered within a fraction of a second, compared to the several minutes required for conventional radiotherapy. For example, a conventional radiotherapy treatment might involve delivering a total dose of 12–25 Gy at a rate up to 0.4 Gy / s, requiring several minutes of treatment time. In contrast, FLASH radiotherapy can deliver a similar total dose at a rate of 40 Gy / s in just a fraction of a second of treatment time.

[0006] However, when the radiation dose rate is very high, as in the case of FLASH radiotherapy, conventional dose monitoring equipment becomes less accurate than expected. Due to the high radiation intensity, a large number of electron / ion pairs are generated, meaning electrons and ions constitute a significant portion of the sample gas, and ions / electrons from different orbits encounter each other on their way to the (multiple) collection electrodes. As a result, recombination between electrons and ions occurs at a high rate that varies with the dose rate, and the measured current no longer corresponds linearly to the radiation dose rate. Therefore, conventional dose monitoring equipment is generally not accurate enough for use with FLASH radiotherapy. Summary of the Invention

[0007] Therefore, what is needed are systems and methods for radiotherapy dose rate monitoring. Systems and methods for radiotherapy dose rate monitoring are also needed for accurately measuring the radiotherapy dose in FLASH radiotherapy. Furthermore, systems and methods for radiotherapy dose rate monitoring are needed for accurately measuring the radiotherapy dose in both conventional and FLASH radiotherapy. Systems and methods for radiotherapy dose rate monitoring that provide an external ionization chamber for dose verification and quality assurance are also needed. Systems and methods for radiotherapy dose rate monitoring that are compatible with and complementary to existing systems and methods for implementing radiotherapy are also required.

[0008] According to one embodiment of the present invention, a radiotherapy dose rate monitoring system includes: a emitting electrode configured to be struck by radiotherapy radiation; a collecting electrode configured to form a circuit with the emitting electrode; a current measuring device configured to measure a current passing through the emitting electrode and the collecting electrode, the current indicating the dose of the radiotherapy radiation; and a chamber enclosed by gas. Secondary electrons emitted from the emitting electrode provide the majority of the current.

[0009] According to another embodiment, the radiotherapy dose rate monitoring system includes a gas enclosed between a pair of complementary electrodes. The dose rate monitoring system is operable to measure a current corresponding to the radiation dose rate. The dose rate monitoring system is operable in either a first mode or a second mode. In the first mode, which can correspond to the dose rate characteristics of FLASH radiotherapy, less than 20% of the current is due to the collection of electron / ion pairs caused by gas ionization. In the second mode, less than 20% of the current is due to the collection of secondary electrons.

[0010] According to another embodiment, the radiotherapy dose rate monitoring system includes a monitoring chamber. The monitoring chamber includes an upper mounting base, a first electrode on an inner surface of the upper mounting base, a lower mounting base separate from the upper mounting base, a second electrode on an inner surface of the lower mounting base, sidewalls coupling the upper and lower mounting bases, and a gas contained within the monitoring chamber. The dose rate monitoring system also includes a voltage source functionally coupled to the first and second electrodes, and a current sensor configured to measure the current passing through the first and second electrodes. The current indicates the radiation dose passing through the monitoring chamber. The radiotherapy dose rate monitoring system is configured to measure radiotherapy dose rates greater than or equal to 40 Gy / s with an accuracy better than 98%. Attached Figure Description

[0011] The accompanying drawings, which are incorporated in and form a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention. Unless otherwise stated, the drawings may not be drawn to scale.

[0012] Figure 1 The illustration shows a block diagram of an exemplary radiation processing system that can be used as a platform according to an embodiment of the present invention.

[0013] Figure 2 The illustration shows a schematic diagram of an exemplary beam path within an exemplary radiation processing system according to an embodiment of the present invention.

[0014] Figure 3A and Figure 3B An exemplary monitoring room according to an embodiment of the present invention is illustrated.

[0015] Figure 4 The illustration shows a schematic diagram of an exemplary corresponding electrode pair as part of a monitoring unit according to an embodiment of the present invention.

[0016] Figure 5 This is a simplified flowchart of an exemplary method for measuring radiotherapy dose rate according to an embodiment of the present invention.

[0017] Figure 6 A block diagram of an exemplary electronic system is illustrated, which can be used as a platform for implementing embodiments of the present invention and / or as a control system for embodiments of the present invention. Detailed Implementation

[0018] Various embodiments of the invention will now be described in detail, examples of which are illustrated in the accompanying drawings. Although the invention will be described in conjunction with these embodiments, it should be understood that they are not intended to limit the invention to these embodiments. Rather, the invention is intended to cover alternatives, modifications, and equivalents that may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, numerous specific details are set forth in the following detailed description of the invention to provide a thorough understanding of the invention. However, those skilled in the art will recognize that the invention can be practiced without these specific details. In other instances, well-known methods, processes, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the invention.

[0019] Some parts of the following detailed description (e.g., method 500) are presented according to other symbolic representations of procedures, steps, logic blocks, processes, and operations on data bits that can be executed on computer memory. These descriptions and representations are the means by which those skilled in the art of data processing most effectively communicate the contents of their work to others skilled in the art. Programs, computer-executed steps, logic blocks, procedures, etc., are herein and generally considered to be a self-consistent sequence of steps or instructions that lead to a desired result. These steps are those that require physical manipulation of physical quantities. Typically, although not always necessary, these quantities take the form of electrical or magnetic signals that can be stored, transmitted, combined, compared, and otherwise manipulated in a computer system. Sometimes, primarily for common reasons, it has proven convenient to refer to these signals as bits, values, elements, symbols, characters, items, numbers, data, etc.

[0020] However, it should be remembered that all these and similar terms will be associated with appropriate physical quantities and are merely convenient labels applied to those quantities. Unless explicitly stated otherwise and as will be apparent from the following discussion, it should be understood that throughout this invention, terms such as “apply” or “control” or “generate” or “test” or “heat” or “bring” or “capture” or “store” or “read” or “analyze” or “solve” or “accept” or “select” or “determine” or “display” or “present” or “calculate” or “send” or “receive” or “reduce” or “detect” or “set” or “access” or “place” or “form” or “install” or “remove” or “stop” or “coat” or “process” or “execute” are used. Discussions of terms such as “line”, “adjust”, “create”, “execute”, “continue”, “index”, “convert”, “calculate”, “measure”, “collect”, or “run” refer to the actions and processes of a computer system or similar electronic computing device, or the actions and processes under its control, which manipulate and transform data representing physical (electronic) quantities in the registers and memory of the computer system into other data representing physical quantities similarly represented in the memory or registers of the computer system or other such information storage, transmission or display devices.

[0021] The term “non-transitory computer-readable medium” should be interpreted as excluding only those types of transient computer-readable media found to fall outside the scope of the patentable subject matter, pursuant to Section 101 of Title 35 of the United States Code, Inre Nuijten, 500F.3d 1346, 1356-57 (Fed. Cir. 2007). The use of this term should be understood as removing the propagation of a transient signal itself from the scope of the claims, without waiving the rights to all standard computer-readable media that not only propagate a transient signal itself.

[0022] In the following disclosure, exemplary embodiments of the invention are illustrated in the manner of linear accelerators and radiotherapy photons (e.g., X-rays). However, those skilled in the art will recognize that the same or similar principles apply to other systems, including, for example, cyclotrons and other types of ionizing radiation, including, for example, electrons, protons, and / or other particles. All such systems are well-suited to and fall within the scope of embodiments of the invention.

[0023] In the following description, various elements and / or features according to embodiments of the invention are presented individually in order to better illustrate these features and not unnecessarily obscure aspects of the invention. However, it should be understood that these features, for example, as disclosed with respect to the first drawing, can be combined in various combinations with other features disclosed in other drawings. All such embodiments are contemplated and can represent embodiments according to the invention.

[0024] Dose rate monitors, systems and methods

[0025] Figure 1 A block diagram of an exemplary radiation processing system 100 is illustrated, which can be used as a platform according to embodiments of the present invention. The radiation processing system 100 may be similar to those commercially available from Varian Medical Systems, Palo Alto, California. Radiation treatment system.

[0026] The support 10 supports a rotatable table 20 with a processing head 30. The processing head 30 can extend into the table 20. A control unit (not shown) is arranged near the support 10, which includes control circuitry for different operating modes of the system 100.

[0027] The radiation treatment system 100 includes, for example, a linear accelerator 40 within a gantry 20, for generating a radiation beam. Typically, the radiation treatment system 100 is capable of generating electron (particle) beams or X-ray (photon) beams for radiation therapy treatment of a patient on a treatment bed 35. Other radiation treatment systems are capable of generating heavy ion particles such as protons. For the purposes of the following disclosure, only X-ray irradiation will be discussed.

[0028] A high-voltage source is provided within the support and / or gantry to supply voltage to an electron gun (not shown) located on an accelerator guide within the gantry 20. Electrons are emitted from the electron gun into the accelerator 40, where they are accelerated. The source supplies radio frequency (microwave) power to generate an electric field within a waveguide. Electrons emitted from the electron gun are accelerated by the electric field in the waveguide and exit the waveguide as a high-energy electron beam 45, for example, with megavolt energies. The electron beam 45 then strikes a suitable metallic target 50, emitting high-energy X-rays 55 in the direction of the patient P.

[0029] like Figure 1 As illustrated, patient P is shown lying on treatment bed 35. The X-rays formed as described above are emitted as a scattered beam 104 from a target in treatment head 30. Typically, the patient plane 116 is located approximately one meter from the X-ray source or target, and the axis of the gantry 20 lies on plane 116 such that the distance between the target and isocenter 178 remains constant as the gantry 20 rotates. Isocenter 178 is located at the intersection of the central axis of patient plane 116 and beam 122. The treatment volume to be irradiated is located around isocenter 178.

[0030] Figure 2A schematic diagram of an exemplary beam path 200 within an exemplary radiation processing system 100 according to an embodiment of the present invention is illustrated. It should be understood that the components shown for the beam path 200 are exemplary and may not be required in all embodiments. Additional components, such as a homogenizer (not shown), may also be included according to embodiments of the present invention. The radiation beam 204 passes through a primary collimator 210, X and Y clamps 230, and a multi-leaf collimator 240. In some embodiments, the primary collimator may include multiple selectable collimators and / or filters. The blades of the primary collimator, X and Y clamps 230, and multi-leaf collimator (MLC) 240 typically comprise X-ray blocking material and are located at the head 30 (…). Figure 1 The X and Y jaws 230 are typically movable and, when fully open, define the width of the X-ray beam in the patient plane 116. Figure 1 The maximum beam width is located at the head 30. The MLC 330 is located at the exit of the head 30 for further shaping of the X-ray beam. An exemplary MLC can use up to 120 individually controllable blades, such as tungsten sheets, which can be moved into or out of the X-ray beam under the control of system software.

[0031] According to an embodiment of the invention, a monitoring chamber 220 is placed within the radiation beam 204. Typically, the monitoring chamber 220 may be positioned between the primary collimator 210 and the X and Y clamps 230, although this is not necessary. The monitoring chamber 220 is used to measure the radiation dose delivered by the radiation beam 204.

[0032] Figure 3A and Figure 3B An exemplary monitoring chamber 220 according to an embodiment of the present invention is illustrated. For example, the monitoring chamber 220 can be used in a radiation processing system 100 to measure, for example, radiation dose and / or dose rate. The monitoring chamber 220 typically supplies radiation to the radiation processing system 100 (… Figure 1 The monitoring room 220 provides closed-loop feedback to control the intensity of beam 204. The monitoring room 220 also typically provides recording of treated doses. If safe and / or prescribed radiation levels are exceeded, the monitoring room 220 can further be used as part of an emergency shutdown capability. Figure 2 As illustrated in the diagram, at least a portion of the monitoring chamber 220 is located within the radiation beam 204. Figure 3A A side sectional view of an exemplary monitoring chamber 220 according to an embodiment of the present invention is illustrated.

[0033] The monitoring chamber 220 can be cylindrical, although this is not mandatory. The monitoring chamber 220 is well-suited to a variety of shapes, including those with regular and irregular cross-sections. For example, in some embodiments, the monitoring chamber 220 may have a square, rectangular, or hexagonal cross-section. Figure 3AAs illustrated, monitoring chamber 220 includes at least one pair of complementary electrodes, such as electrode 320 and electrode 320a. Multiple pairs of complementary electrodes form a circuit. In some embodiments, one or more pairs of complementary electrodes may be mounted on an upper mounting substrate 310 and / or a lower mounting substrate 310a, which are coupled together via multiple sidewalls 315. In some embodiments, one or more of the multiple pairs of complementary electrodes may be formed or mounted to other structures.

[0034] The monitoring chamber 220 is typically gas-sealed. For example, a volume 316 surrounded by an upper mounting base 310, a lower mounting base 310a, and sidewalls 315 includes gas 350. In some embodiments, gas 350 may be sealed within volume 316, for example, gas 350 is restricted from exchanging with the atmosphere outside volume 316. In some embodiments, volume 316 is not sealed in this way. It is generally desirable that the mounting bases 310, 310a, and associated electrodes are highly transparent to the radiation beam 204. For example, these components may be characterized as thin and having limited mechanical strength. This mechanical constraint may limit the pressure range of gas 350 and / or facilitate the requirements for mounting electrodes on the bases. In some embodiments, gas 350 may be below, equal to, or above ambient atmospheric pressure.

[0035] Figure 3B The illustration shows a plan view of an exemplary arrangement of four electrodes on the inner surface of a mounting substrate 310 according to an embodiment of the present invention. Embodiments of the present invention are well-suited for more or fewer electrodes, and electrodes(s) of different shapes and orientations. The electrodes need not be substantially planar in shape, such as... Figure 3B As illustrated in the figure. For example, according to embodiments of the invention, one or more electrodes may include three-dimensional structures, including, for example, wire, rod, strip, cup, cone, and / or mesh shapes. It will be understood that in some embodiments, not all electrodes need to have the same shape.

[0036] The plan view of the electrodes(s) of the lower mounting substrate 310a is not shown, but it can be mirrored with the electrodes of the upper mounting substrate 310. As will be further described below, the electrodes of the upper mounting substrate 310 are paired with corresponding electrodes of the lower mounting substrate 310a (or elsewhere) to form a circuit. For example, electrode 320 of the upper mounting substrate 310 and electrode 320a of the lower mounting substrate 310a (… Figure 3A They are paired to form a circuit.

[0037] The exemplary upper mounting substrate 310 and the exemplary lower mounting substrate 310a can be configured to be perpendicular to and intersect with the radiation beam 204, but this is not required. For example, in some embodiments, one or more substrates 310, 310a and / or electrodes 320, 320a, 325, 325a, 330, 330a, 335, 335a ( Figure 3A The beam may not be perpendicular to the radiation beam 204. Furthermore, in some embodiments, one or more substrates 310, 310a and / or electrodes 320, 320a, 325, 325a, 330, 330a, 335, 335a ( Figure 3A They do not need to be parallel to each other. For example, sidewall 315 ( Figure 3A The collecting electrode may not be perpendicular to the radiation beam 204 and may not be parallel to another electrode. The sidewall 315 may form or support the electrode. Furthermore, in some embodiments, the collecting electrode does not need to be located within the radiation beam 204. Generally, the radiation beam 204 may be configured to pass through at least a portion of the volume 316.

[0038] An exemplary mounting substrate 310 includes four electrodes: an inner electrode 320, an inner electrode 325, an outer electrode 330, and an outer electrode 335. The inner electrodes 320 and 325 can be configured to be entirely within the incident radiation beam 204. The inner electrodes 320 and 325 are configured to measure the total dose rate of the incident radiation beam 204. Any dose rate difference between the inner electrodes 320 and 325 can reveal an angular symmetry error in the beam 204.

[0039] External electrodes 330 and 335 can be configured partially within beam 204, for example, at the edge of beam 204. Any dose rate difference between external electrodes 330 and 335 can reveal positional symmetry errors in beam 204.

[0040] Figure 4 The illustration shows a schematic diagram of an exemplary corresponding complementary electrode pair as part of a monitoring unit 220 according to an embodiment of the present invention. The monitoring unit 220 includes a positive electrode 455, which may also be known as or referred to as a collecting electrode, such as electrode 320a on the lower mounting substrate 310a. Figure 3A The monitoring unit 220 also includes a negative electrode 465, which may also be known as or referred to as a transmitting electrode, such as electrode 320 on the mounting substrate 310. Figure 3A The terms positive and negative electrodes refer to the relative potentials of the electrodes with respect to each other. Only one pair of complementary electrodes is shown in the figure, such as electrodes 320 and 320a. Other complementary electrode pairs, such as electrode pairs 325 and 325a, electrode pairs 330 and 330a, and / or electrode pairs 335 and 335a, are also shown. Figure 3A (If it exists) is configured similarly and works in a similar way.

[0041] In some embodiments, voltage source 450 applies a potential difference +V across positive electrode 455 and negative electrode 465. In some embodiments, the potential difference can be offset; for example, -V can be applied to negative electrode 465 relative to positive electrode 455 when positive electrode 455 is at ground potential. In some embodiments, the potential difference can be divided between the electrodes; for example, +V / 2 is applied to positive electrode 455 and -V / 2 is applied to negative electrode 465. In some embodiments, the voltage split may be non-uniform.

[0042] It should be understood that the radiation beam 204 will typically have a larger range than illustrated. For example, in some embodiments, the radiation beam 204 may be as wide as or wider than electrodes 455 and 465. The radiation beam 204 passing through the gas 350 ionizes some of the gas 350, generating positive ions 420 and negative electrons 430. Furthermore, the radiation beam 204 generates secondary electrons 410 via interaction with the conductive material of the negative electrode 465, and secondary electrons 440 via interaction with the conductive material of the positive electrode 455.

[0043] Radiation therapy is typically delivered in very short pulses. For example, a conventional radiation therapy system can deliver 360 pulses per second, each pulse having a duration of approximately 4 μs. Each pulse can deliver a dose of approximately 1 mGy, for example. This exemplary protocol delivers approximately 0.4 Gy / s on a time-averaged basis. FLASH radiation therapy can be characterized by delivering a radiation dose of greater than or equal to 40 Gy per second on a time-averaged basis.

[0044] Under conventional techniques, when electrodes 455 and 465 are separated by a gap d of approximately 1.0 mm, the potential difference between the electrodes can be approximately 500 volts, generating an electric field of approximately 500,000 volts / meter. When such a voltage is applied, the current passing through the monitoring unit, for example, as measured by current sensor 460, is dominated by the ionization of gas 350. For example, negative electrons 430 are collected on the positive electrode or collecting electrode 455, and positive ions 420 are collected on the negative electrode 465. Under conventional techniques, secondary electrons 410 and 440 essentially do not contribute to the current. For example, the contribution of secondary electrons 410 and 440 to the current is less than 10%.

[0045] At high radiation intensities, such as pulses equal to or greater than approximately 2 mGy / 4 μs, a large number of electron 430 / ion 420 pairs are generated, such that electrons 430 and ions 420 constitute a significant portion of the sample gas. As a result, recombination between electrons 430 and ions 420 occurs at a high rate, and the measured current no longer corresponds linearly to the radiation dose rate. Therefore, conventional dose monitoring equipment is generally insufficiently accurate for use with high-intensity and / or FLASH radiotherapy. For example, such conventional dose monitoring equipment typically does not achieve an accuracy greater than or equal to 98% when reporting dose rates for high-intensity and / or FLASH radiotherapy. Accuracy can be determined by comparison with other well-known dosimeter devices that are not typically used during treatment, including, for example, external probes and / or thin-film dosimeters.

[0046] According to an embodiment of the invention, voltage source 450 can generate a voltage between electrodes 455 and 465 that is sufficient to prevent secondary electrons emitted from the electrodes from being collected on the electrodes, and that the voltage is low enough to allow ion pairs to recombine in gas 350 and not be collected on the electrodes.

[0047] According to an embodiment of the invention, voltage source 450 can generate a voltage of 10-100 volts, for example 40 volts, across electrodes 455, 465 spaced apart by a gap d of approximately 1.0 mm. This combination of voltage and spacing results in an electric field strength of 10,000 volts / meter to 100,000 volts / meter. In some embodiments, other combinations of voltage and spacing can be utilized to generate such a range of electric field strengths. It should be understood that such voltages and / or field strengths are approximately an order of magnitude smaller than those typically applied for similar spacing between electrodes under conventional techniques. At this reduced voltage, according to an embodiment of the invention, the ionization of the monitoring chamber filling gas 350 does not significantly contribute to the collected charge. For an electric field strength of approximately 40,000 volts / meter between electrodes 455 and 465, a low bias voltage of +V, for example, approximately 40 volts for a 1.0 mm gap, results in and / or allows ions 420 and electrons 430 to recombine almost immediately. Therefore, ions 420 and electrons 430 are typically not collected on electrodes 465 and / or 455, resulting in near-zero ion collection efficiency. For example, ions 420 and electrons 430 contribute less than half of the current.

[0048] According to embodiments of the invention, the ideal repulsion of secondary electrons emitted from the electrodes is primarily a function of the voltage applied between the electrodes. Therefore, a higher voltage promotes greater repulsion of secondary electrons from the electrodes. In contrast, a lower electric field favors the ideal rapid recombination of ionized gas molecules, resulting in rapid electron / ion pair recombination and no contribution to the current. Therefore, according to embodiments of the invention, it may be beneficial to increase the gap dimension between complementary electrode pairs to reduce the electric field between the electrodes while maintaining the desired high potential between them; for example, increasing the gap size to approximately 4 millimeters for a 40-volt bias voltage.

[0049] According to embodiments of the invention, it may be advantageous to use a gas 350 with a higher ionization recombination coefficient and / or higher electronegativity than ordinary air in the dose monitoring system 220, such as a gas containing a higher concentration of oxygen (O2) than air, including pure oxygen, and / or a fluorine-containing gas (including, for example, sulfur hexafluoride SF6). This higher ionization recombination coefficient and / or higher electronegativity facilitates faster recombination of separated ions, advantageously further reducing the contribution of positive ions 420 and negative electrons 430 to the current.

[0050] According to an embodiment of the invention, the current through the current sensor 460 is primarily caused by the interaction between the high-intensity radiation beam 204 and the conductive material of the negative electrode or emitting electrode 465. The radiation beam 204 knocks out some secondary electrons (SE) 410 with an energy of approximately 40 eV from the negative electrode 465. Therefore, the negative potential of approximately 40 volts is sufficient to repel these electrons from the negative electrode 465. Due to the negative potential of electrode 465, the emitted electrons are repelled and do not return to the negative electrode 465, but are replaced by a current in the circuit. This current I represents the total electron charge released from the surface of the negative electrode 465, which is proportional to the beam dose rate. Electrons 440 knocked out from the positive electrode 455 will combine with ions 420 and / or return to the positive electrode or collecting electrode 455, and do not constitute a significant portion of the current. In electrotherapy, the measured current is related to the electron beam current and energy. The total electron charge can be used to measure the electron beam current with a well-defined electron beam energy. Therefore, the total secondary electron charge can be used to measure the dose delivered to the patient at any depth.

[0051] Compared to conventional techniques, embodiments of the invention utilize much lower transelectrode voltages and / or much lower electric fields in the dose monitoring system, and employ a different mechanism for generating current through such electrodes. For example, current generation under conventional techniques is dominated by ionized gas. In contrast, embodiments of the invention govern current generation by the emission of secondary electrons from the negative or emitting electrode. In this novel manner, embodiments of the invention enable accurate measurement of high radiation dose rates, such as dose rates equal to or greater than approximately 2 mGy per 4 μs pulse or approximately 0.7 Gy / s on a time-averaged basis, including FLASH radiotherapy dose rates. For example, embodiments of the invention can achieve an accuracy greater than or equal to 98% for high-intensity and / or FLASH radiotherapy dose rates.

[0052] Refer again Figure 1 Many conventional radiotherapy systems are designed to rotate around an isocenter 178 of the patient P in order to distribute the radiation dose across all surrounding tissues while delivering the full dose to the target tissue. One potential benefit of FLASH radiotherapy is that it appears to reduce radiation-induced damage to surrounding tissues while maintaining a tumor response comparable to more conventional radiotherapy protocols. This benefit of FLASH radiotherapy may diminish the benefits of rotation(s). Embodiments of the invention provide systems and methods for accurately measuring the dose and / or dose rate of FLASH radiotherapy. Therefore, embodiments of the invention can facilitate non-rotating FLASH radiotherapy, advantageously reducing the cost, complexity, and room size requirements of such radiotherapy systems.

[0053] Figure 5 This is a simplified flowchart of an exemplary method 500 for measuring radiotherapy dose rate according to an embodiment of the present invention. It can be implemented wholly or partially using a computer system (e.g., Figure 6 The computer system 600) executes method 500.

[0054] In 510, a voltage is applied to a pair of complementary electrodes, such as electrodes 455 and 465. Figure 4 These are dose rate measurement chambers (e.g., dose rate measurement chamber 220) Figure 2 It is part of a radiation therapy. Radiation therapy can be a dose rate intensity corresponding to FLASH radiation therapy. In some embodiments, a voltage may be applied during the pulse of radiation therapy. In some embodiments, the voltage may be changed and / or removed when radiation therapy is not present (e.g., between radiation pulses).

[0055] According to embodiments of the invention, a voltage source can be configured to apply a potential difference between complementary electrode pairs sufficient to repel secondary electrons. In some embodiments, the applied voltage can be between 30 and 100 volts. In some embodiments, the voltage source can be configured to generate an electric field between the complementary electrode pairs such that electrons and ions in the gas ionized by radiotherapy radiation in the dose rate measurement chamber recombine and do not contribute to the current between the complementary electrode pairs. In some embodiments, the electric field strength can be between 10,000 and 100,000 volts per meter.

[0056] In step 520, secondary electrons emitted from the electrodes are collected by the electrodes. It can be understood that electrons and ions in the gas ionized by the radiotherapy radiation in the dose rate measurement chamber recombine and are not collected at the complementary electrode pair. In step 530, the current induced by the secondary electron emission is measured to indicate the dose rate of the radiotherapy radiation.

[0057] In option 540, dose rate indication is used as feedback to control the dose rate of FLASH radiotherapy.

[0058] Figure 6 A block diagram of an exemplary electronic system 600 is illustrated, which can be used as a platform for implementing embodiments of the present invention and / or as a control system for embodiments of the present invention. In some embodiments, the electronic system 600 may be a "server" computer system. The electronic system 600 includes an address / data bus 650 for transmitting information and a central processing unit complex 605 functionally coupled to the bus for processing information and instructions. The bus 650 may include, for example, a Peripheral Component Interconnect High Speed ​​(PCIe) computer expansion bus, an Industry Standard Architecture (ISA), an Extended ISA (EISA), Microchannel, multiple buses, IEEE 796, IEEE 1196, IEEE 1496, PCI, Computer Automation Measurement and Control (CAMAC), MBus, runway bus, Compute Fast Link (CXL), etc.

[0059] In some embodiments, the central processing unit (CPU) complex 605 may include a single processor or multiple processors, such as a multi-core processor or multiple separate processors. The CPU complex 605 may include any combination of various types of well-known processors, including, for example, digital signal processors (DSPs), graphics processing units (GPUs), complex instruction set (CISC) processors, reduced instruction set (RISC) processors, and / or very long word (VLIW) processors. In some embodiments, the exemplary CPU complex 605 may include, for example, a finite state machine implemented in one or more field-programmable gate arrays (FPGAs), which may be combined with and / or replaced by other types of processors for control according to embodiments of the invention.

[0060] The electronic system 600 may further include: a volatile memory 615 (e.g., random access memory RAM) coupled to a bus 650 for storing information and instructions for the central processing unit complex 605; and a non-volatile memory 610 (e.g., read-only memory ROM) coupled to the bus 650 for storing static information and instructions for the processor complex 605. Optionally, the electronic system 600 may also include a variable non-volatile memory 620 (e.g., NOR flash memory) for storing information and instructions for the central processing unit complex 605 that can be updated after the system 600 has been manufactured. In some embodiments, only one of ROM 610 or flash memory 620 may be present.

[0061] Figure 6 The electronic system 600 also includes an optional input device 630. Device 630 can selectively transmit information and commands to the central processing unit 600. Input device 630 can be any suitable device for transmitting information and / or commands to the electronic system 600. For example, input device 630 can take the form of a keyboard, buttons, joystick, trackball, audio transducer (e.g., microphone), touch-sensitive digitizer panel, eye scanner, etc.

[0062] Electronic system 600 may include display unit 625. Display unit 625 may include liquid crystal display (LCD), cathode ray tube (CRT), field emission device (FED, also known as flat panel CRT), light-emitting diode (LED), plasma display device, electroluminescent display, electronic paper, electronic ink (e-ink), or other display devices suitable for creating user-recognizable graphic images and / or alphanumeric characters. In some embodiments, display unit 625 may have associated lighting devices.

[0063] Optionally, the electronic system 600 also includes an expansion interface 635 coupled to the bus 650. The expansion interface 635 can implement many well-known standard expansion interfaces, including but not limited to a Secure Digital Card interface, a Universal Serial Bus (USB) interface, a Compact Flash memory interface, a Personal Computer (PC) Card interface, a Card Bus, a Peripheral Component Interconnect (PCI) interface, a Peripheral Component Interconnect Passthrough (PCI Express), a Mini PCI interface, IEEE 1394, a Small Computer System Interface (SCSI), a Personal Computer Memory Card International Association (PCMCIA) interface, an Industry Standard Architecture (ISA) interface, an RS-232 interface, etc. In some embodiments of the invention, the expansion interface 635 may include signals substantially corresponding to the signals of the bus 650.

[0064] A variety of well-known devices can be attached to the electronic system 600 via bus 650 and / or expansion interface 635. Examples of such devices include, but are not limited to, rotating magnetic storage devices, flash memory devices, digital cameras, wireless communication modules, digital audio players, and global positioning system (GPS) devices.

[0065] Optionally, system 600 also includes a communication port 640. Communication port 640 can be implemented as part of expansion interface 635. When implemented as a separate interface, communication port 640 can typically be used to exchange information with other devices via communication-oriented data transmission protocols. Examples of communication ports include, but are not limited to, RS-232 ports, Universal Asynchronous Receiver Transmitter (UART), USB ports, infrared transceivers, Ethernet ports, IEEE 1394, and synchronous ports.

[0066] Optionally, system 600 includes a network interface 660, which can implement a wired or wireless network interface. In some embodiments, electronic system 600 may include additional software and / or hardware features (not shown).

[0067] Various modules of System 600 can access computer-readable media, and the term is known or understood to include removable media, such as Security Digital (“SD”) cards, CDs and / or DVD ROMs, floppy disks, etc., as well as non-removable or internal media, such as hard disk drives, solid-state drives (SSDs), RAM, ROM, flash memory, etc.

[0068] According to embodiments of the present invention, systems and methods for monitoring radiotherapy dose rates are provided. Furthermore, according to embodiments of the present invention, systems and methods for monitoring radiotherapy dose rates for accurately measuring the radiotherapy dose of FLASH radiotherapy are provided. Additionally, according to embodiments of the present invention, systems and methods for monitoring radiotherapy dose rates for accurately measuring the radiotherapy dose of conventional radiotherapy and FLASH radiotherapy are provided. According to further embodiments of the present invention, systems and methods for monitoring radiotherapy dose rates in an external ionization chamber for dose verification and quality assurance are provided. Furthermore, according to embodiments of the present invention, systems and methods for monitoring radiotherapy dose rates that are compatible with and complementary to existing systems and methods for implementing radiotherapy are provided.

[0069] Although the invention has been shown and described with respect to one or more exemplary embodiments, equivalent changes and modifications will occur to those skilled in the art upon reading and understanding this specification and the accompanying drawings. In particular, with respect to the various functions performed by the aforementioned components (assemblies, devices, etc.), the terminology used to describe such components (including references to “part”) is intended, unless otherwise stated, to correspond to any component performing the specified function of said component (e.g., functionally equivalent), even if it is not structurally equivalent to the disclosed structure performing the functions of the exemplary embodiments of the invention illustrated herein. Furthermore, while specific features of the invention may have been disclosed with respect to only one embodiment among several embodiments, such features may be combined with one or more features of other embodiments, which may be necessary and advantageous for any given or particular application.

[0070] Therefore, various embodiments of the invention have been described. Although the invention has been described in particular embodiments, it should be understood that the invention should not be construed as limited to these embodiments, but rather as interpreted in accordance with the appended claims.

Claims

1. A radiotherapy dose rate monitoring system, comprising: The emitting electrode is configured to be struck by radiation from radiotherapy. A collecting electrode is configured to form a circuit with the emitting electrode; A current measuring device is configured to measure the current passing through the emitting electrode and the collecting electrode, the current indicating the dose of radiation from the radiotherapy. A chamber, enclosed by gas, and The secondary electrons emitted from the emitting electrode provide the majority of the current.

2. The radiotherapy dose rate monitoring system according to claim 1, wherein the ionization contribution of the gas is less than 20% of the current.

3. The radiotherapy dose rate monitoring system according to claim 1, wherein the gas is characterized by having a larger ionization recombination coefficient than air.

4. The radiotherapy dose rate monitoring system according to claim 3, wherein the gas comprises oxygen at a concentration higher than that of air.

5. The radiotherapy dose rate monitoring system according to claim 3, wherein the gas comprises fluorine.

6. The radiotherapy dose rate monitoring system according to claim 1 further includes: A voltage source coupled between the emitting electrode and the collecting electrode. The voltage source is configured to apply a potential difference between the emitting electrode and the collecting electrode sufficient to repel the secondary electrons.

7. The radiotherapy dose rate monitoring system of claim 1, wherein the radiotherapy dose rate monitoring system is configured to generate an electric field between the emitting electrode and the collecting electrode such that electrons and ions from the ionized gas recombine and do not contribute to the current between the emitting electrode and the collecting electrode.

8. A radiotherapy dose rate monitoring system, comprising: The gas enclosed between pairs of complementary electrodes. The radiotherapy dose rate monitoring system is operable to measure the current corresponding to the radiation dose rate. The radiotherapy dose rate monitoring system described herein can operate in either a first mode or a second mode. In the first mode, less than 20% of the current is due to the collection of electron / ion pairs at the electrode, which is caused by the ionization of the gas. In the second mode, less than 20% of the current is due to the collection of secondary electrons.

9. The radiotherapy dose rate monitoring system according to claim 8, wherein the first mode corresponds to the dose rate characteristics of FLASH radiotherapy.

10. The radiotherapy dose rate monitoring system of claim 8, wherein the second mode corresponds to a dose rate of less than 40 Gy / s.

11. The radiotherapy dose rate monitoring system of claim 8, wherein the first mode is configured to place a potential equal to or less than 100 volts across the pair of complementary electrodes.

12. The radiotherapy dose rate monitoring system of claim 11, wherein the first mode is configured to have a potential greater than 10 volts across the pair of complementary electrodes.

13. The radiotherapy dose rate monitoring system of claim 8, wherein the first mode is configured to generate an electric field strength equal to or less than 100,000 volts per meter in the region between the pairs of complementary electrodes.

14. The radiotherapy dose rate monitoring system of claim 13, wherein the first mode is configured to generate an electric field strength greater than 10,000 volts / meter in the region between the pairs of complementary electrodes.

15. A radiotherapy dose rate monitoring system, comprising: The monitoring room includes: First electrode; Second electrode; The sidewalls that couple the first electrode and the second electrode; The gas contained within the monitoring chamber; A voltage source that is functionally coupled to the first electrode and the second electrode; A current sensor is configured to measure the current passing through the first electrode and the second electrode. The current indicates the radiation dose passing through the monitoring room, and The radiotherapy dose rate monitoring system is configured to measure a radiotherapy dose rate greater than or equal to 40 Gy / s during patient treatment with an accuracy better than 98%.

16. The radiotherapy dose rate monitoring system of claim 15, wherein the current is primarily caused by the collection of secondary electrons on one of the first and second electrodes.

17. The radiotherapy dose rate monitoring system of claim 15, wherein the gas is characterized by having a greater electronegativity than air.

18. The radiotherapy dose rate monitoring system of claim 15, wherein the gas is characterized by having a larger ionization recombination coefficient than air.

19. The radiotherapy dose rate monitoring system of claim 15, wherein the radiotherapy dose rate monitoring system is configured to generate an electric field between the first electrode and the second electrode such that electrons and ions of the gas ionized by the radiotherapy recombine and do not contribute to the current between the first electrode and the second electrode.

20. The radiotherapy dose rate monitoring system of claim 15, wherein the voltage source is configured to apply a potential difference between the first electrode and the second electrode sufficient to repel secondary electrons from one of the first electrode and the second electrode.

21. The radiotherapy dose rate monitoring system of claim 20, wherein the radiotherapy dose rate monitoring system is configured to apply the potential difference during the pulse of the radiation dose.

22. The radiotherapy dose rate monitoring system of claim 15, wherein the first electrode is mounted on a first mounting substrate.

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