Volume intensity modulated radiation therapy plan generation method and volume intensity modulated radiation therapy equipment

Abstract

The invention provides a volume intensity modulated radiation therapy plan generation method, which is characterized by comprising the following steps of: setting a plurality of control points for any irradiation angle of a focus based on focus parameters; for any irradiation angle of the focus, generating a plurality of sub-fields corresponding to each control point in the plurality of control points and composed of the beam dose and the closed state of the multi-leaf grating, and forming an irradiation field corresponding to the irradiation angle by the plurality of sub-fields; generating a sub-field execution sequence file for each sub-field of the irradiation field of any irradiation angle of the focus; and based on the sub-field execution sequence file at each irradiation angle, generating a multi-arc volume intensity modulated radiotherapy plan containing n arcs.

Description

Technical Field

[0001] This application relates to the field of radiotherapy technology, and more specifically, to a method for generating volumetric intensity-modulated radiotherapy (IMRT) plans and an IMRT device. Background Technology

[0002] Radiation therapy for tumors is an important treatment method that uses radiation to kill cancer cells. Its core objective is to deliver a radical dose to the target area while maximally protecting the surrounding normal tissues. Currently, radiation therapy primarily uses high-energy radiation generated by linear accelerators, administered through targeted irradiation or focused irradiation around the tumor in a 360-degree space. With the development of radiation therapy technology, it has gradually evolved from traditional conformal radiotherapy to intensity-modulated radiotherapy (IMRT) and volumetric intensity-modulated rotational radiotherapy (VIMRT).

[0003] Traditional conformal radiotherapy uses a multi-leaf collimator (MLC) as a beam confinement device. In any beam direction, the shape of the irradiation field formed by the MLC adapts to the shape of the lesion (target area), ensuring that the irradiated area covers the target area as much as possible while avoiding surrounding normal tissue. However, maximizing target area coverage and minimizing surrounding normal tissue are contradictory requirements. Maximizing target area coverage may leave surrounding normal tissue at risk of radiation damage. Conversely, minimizing surrounding normal tissue may result in insufficient irradiation of the lesion. Furthermore, the irradiation field shape formed by the MLC only allows high-energy radiation to pass indiscriminately, meaning the radiation intensity is uniform throughout the entire irradiation area. However, radiation intensity decreases with increasing depth of incidence within the object. Cancer cells within the target area receive varying doses due to their different spatial positions relative to the radiation source, becoming a significant factor affecting the effectiveness of radiotherapy.

[0004] Intensity-modulated radiotherapy (IMRT) optimizes conformal radiotherapy by further dividing the multileaf collimator (MLC) irradiation field into a set of MLC subfields based on the spatial relationship between the tumor target area and normal tissue along the beam path for each beam direction. Different irradiation ranges and doses are set for each subfield, achieving intensity modulation of the irradiation dose distribution within the irradiation field. This ensures that the irradiation dose distribution in the target area meets the prescription requirements while keeping the dose to surrounding normal organs within a safe range. However, IMRT can only select a limited number of incident angles for irradiation, meaning it can only perform point irradiation at a few angles. It cannot fully utilize the changes in the spatial relationship between the tumor and normal tissue within 360 degrees to optimize the incident angle and field shape. The freedom in selecting the incident direction is limited, making it difficult to further improve the avoidance effect on normal tissues and the consistency of target dose.

[0005] Volumetric intensity-modulated radiotherapy (IMRT) utilizes a 360-degree rotating irradiation method, simultaneously adjusting the dose rate and the position of the multi-leaf collimator during rotation, achieving better dose distribution optimization and protection of normal tissues. The beam can be focused on the target area from all directions, offering greater flexibility and better results in avoiding functional organs. Simultaneously, the dose rate and rotation speed are adjusted during rotation, changing the incident direction and beam intensity to achieve volumetric intensity modulation. However, this technique only uses 1-2 rotation arcs, and in a specific incident direction during rotation, only one or two MLC conformal irradiation fields can be used, making it impossible to optimize spatial dose distribution using multi-field IMRT along the incident direction. For complex lesions where the tumor is spatially intertwined with surrounding radiation-sensitive functional organs, a dilemma arises: "insufficient tumor dose due to organ avoidance" or "organ damage due to ensuring tumor dose."

[0006] In short, while volumetric intensity-modulated radiotherapy (IMRT) is an optimization compared to traditional conformal radiotherapy, it still has significant limitations: Single-arc or double-arc rotational irradiation can only utilize one or two MLC conformal irradiation fields per incident direction, making multi-field IMRT impossible. This makes it difficult to balance target dose and organ protection in complex cases where the tumor is closely adjacent to sensitive organs. Furthermore, C-arm and ring gantry systems use cables to power and transmit signals to the main unit of the equipment mounted on the rotating gantry. Due to this structure, the gantry cannot rotate continuously; it must pause and reverse rotation at a maximum angle of 180°, requiring multi-arc rotational radiotherapy to be performed in stages. Additionally, due to this structure, the gantry rotation speed is limited to no more than one revolution per minute, which not only reduces irradiation efficiency but also prolongs treatment time due to limitations in rotation speed and direction. These problems severely restrict the application and treatment efficiency of IMRT in clinical practice.

[0007] To address the aforementioned issues, existing technologies urgently need improvement. Summary of the Invention

[0008] The purpose of this invention is to provide a high-resolution volumetric intensity-modulated rotational radiotherapy technique that enables simultaneous intensity-modulated radiotherapy in the incident direction.

[0009] According to one aspect of the present invention, a method for generating a volumetric intensity-modulated radiotherapy plan is characterized by comprising the following steps: Based on the geometric distribution of the lesions and the planning parameters, n control points are set for any irradiation angle of the lesions, n≥3, and each control point specifies the beam dose and the position of the multi-leaf grating blades. For any irradiation angle of the lesion, n subfields are generated corresponding to each of the n control points, and the n subfields constitute the irradiation field corresponding to that irradiation angle; For each subfield of the irradiation field at any irradiation angle of the lesion, a control point execution sequence file is generated, consisting of n arcs executed in a clockwise or counterclockwise direction, each corresponding to a subfield of each irradiation angle, in the order of executing one subfield at a time during the rotational irradiation process. Based on the execution sequence file consisting of subfields at successive irradiation angles in n consecutive rotating arcs, a multi-arc volumetric intensity-modulated radiotherapy plan containing n arcs is generated.

[0010] Preferably, the subfield execution sequence file contains the control point execution sequence of each of the n subfields of the illumination field at the illumination angle.

[0011] Preferably, in the step of generating the subfield execution sequence file, based on the relationship between the beam dose and the position change of the multileaf grating blades of each subfield of the irradiation field at adjacent irradiation angles on each rotating arc, and under the premise of satisfying the constraints of the radiotherapy equipment on the beam dose rate and the movement speed change of the multileaf grating blades, the execution sequence of n subfields corresponding to each irradiation angle is determined.

[0012] Preferably, in the step of generating a multi-arc volumetric intensity-modulated radiotherapy plan containing n arcs, the subfields of the irradiation fields at each irradiation angle to be executed in each of the n arcs are determined according to the execution sequence of the multiple subfields of the irradiation field at each irradiation angle.

[0013] Preferably, each of the n arcs includes an irradiation execution part and an idle part, the execution part and the idle part forming a 360° rotation, and the n arcs are executed continuously.

[0014] Another invention is a volumetric intensity-modulated radiotherapy device, such as... Figure 1 As shown, it is characterized by having: A radiation source that emits radiation used in radiotherapy; The frame, which carries the radiation source, is capable of rotating continuously for multiple cycles; Slip rings are used to transmit power and data to the main unit of the equipment mounted on the rotating frame. Multi-leaf gratings can adjust the shape of the leaves to create windows, or subfields, that allow radiation to pass through; and The control system is used to control the radiotherapy equipment to execute the control point sequence file of the prescribed treatment plan, thereby realizing the irradiation scheme specified in the treatment plan. The volumetric intensity-modulated radiotherapy device performs the volumetric intensity-modulated radiotherapy planning generation method according to any one of claims 1-6.

[0015] According to the present invention, a high-resolution volumetric intensity-modulated rotational radiotherapy technique is provided that enables simultaneous intensity-modulated radiotherapy in the incident direction. Attached Figure Description

[0016] To more clearly illustrate the embodiments of the present invention or the prior art, the accompanying drawings are briefly described below. The drawings are only some embodiments of the present invention; those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0017] Figure 1 This is a structural diagram of a volumetric intensity-modulated radiotherapy device.

[0018] Figure 2 This is a flowchart of High-Resolution Volumetric Modulated Radiation Therapy (HD-VMAT), showing the complete steps from accelerator startup, multi-arc irradiation execution to the end of treatment.

[0019] Figure 3 This is a schematic diagram of high-resolution volumetric intensity-modulated rotational radiotherapy (HD-VMAT) performed on an accelerator, showing the coordinated working state of MLC movement and dose control during gantry rotation.

[0020] Explanation of symbols: 1. Ray generation unit; 2. Irradiation field forming unit; 3. Slide rails; 4 racks; 5 Control System Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are for illustrative purposes only and do not constitute a limitation on the scope of protection of this invention.

[0022] The terms "comprising" or "including" as used in this invention mean that the element preceding the word covers the element listed after the word, and do not exclude the possibility that other elements may also be included.

[0023] All terms used in this invention (including technical or scientific terms) have the same meaning as understood by one of ordinary skill in the art to which this invention pertains, unless otherwise specifically defined. It should also be understood that terms defined in general dictionaries should be interpreted as having meanings consistent with their meanings in the context of the relevant art, and not as being interpreted with idealized or highly formalized meanings, unless expressly defined herein.

[0024] For components, specific model numbers and other parameters of components not described in detail in this section, the interrelationships between components and control circuits, these may be considered as techniques, methods and devices known to those skilled in the art, but where appropriate, such techniques, methods and devices should be considered part of the specification.

[0025] In existing technologies, the field of tumor radiotherapy has evolved from conformal radiotherapy to intensity-modulated radiotherapy (IMRT), and then to volumetric intensity-modulated radiotherapy (VIMRT). Traditional VIM rotary radiotherapy uses single-arc or dual-arc rotational irradiation, forming only a single conformal irradiation field in each incident direction, failing to achieve the dose distribution optimization required for multi-field intensity modulation. When dual-arc treatment is required, C-arm gantry and ring gantry use cables to power and transmit signals to the main unit of the equipment mounted on the rotating gantry. Due to this limitation, a staged rotation method must be adopted, resulting in gantry pauses and reverse rotations, and the gantry rotation speed is only less than 1 revolution per minute, significantly prolonging the treatment time. In clinical scenarios with complex spatial relationships between tumors and sensitive organs, existing technologies struggle to effectively avoid functional organs while ensuring target dose coverage, presenting a technical bottleneck where treatment efficiency and dose distribution are difficult to balance.

[0026] To address these issues, the research team believes that the limited number of subfields in single-arc or dual-arc irradiation modes is the core factor affecting dose distribution optimization, while the low execution efficiency in dual-arc irradiation mode stems from the physical limitations of the gantry movement pattern. Single or dual-arc irradiation modes cannot easily achieve dose distribution optimization with only one or two conformal irradiation fields. However, if the physical limitations of the gantry movement pattern can be overcome to achieve continuous gantry rotation, and dose distribution optimization can be achieved using a multi-arc irradiation mode, it can effectively supplement single-arc or dual-arc irradiation modes.

[0027] By analyzing the dynamic characteristics of subfield formation during rotational irradiation, this study attempts to introduce a multi-subfield mode of intensity-modulated radiotherapy (IMRT) into the rotational irradiation framework. During continuous multi-arc rotation, the beam dose and multi-leaf grating morphology are simultaneously adjusted for each gantry angle (beam direction), ultimately leading to the formation of an IMRT multi-subfield mode at each irradiation angle. Furthermore, by investigating the timing control mechanism required for continuous multi-arc execution, a method is proposed to coordinate the connection between different rotational arcs by optimizing the subfield execution sequence file.

[0028] Next, refer to Figure 1 The overall structure of the volumetric intensity-modulated radiotherapy device of the present invention is described below. For ease of explanation, minor components are omitted, and only the major components are shown schematically.

[0029] like Figure 1 As shown, the volumetric intensity-modulated radiotherapy (IMRT) device includes: a radiation generation unit 1, an irradiation field forming unit 2, a slide rail 3, a gantry 4, and a control system 5.

[0030] The radiation generating unit 1 generates high-energy rays, which directly act on tumor cells, destroying their genetic material and thus inhibiting their growth and proliferation, achieving the therapeutic goal. Examples of high-energy rays include X-rays, gamma rays, and high-energy photon beams.

[0031] The irradiation field forming unit 2, for example using a multi-leaf grating (MLC) as a beam confining device, adapts the shape of the irradiation field formed by the MLC to at least a portion of the shape of the lesion (target area) in any beam direction of any arc, thereby forming a subfield. Here, "arc" or "rotation arc" refers to the fact that, as the gantry rotates a predetermined distance, the radiation generating unit 1 rotates around the lesion along a predetermined arc, thereby performing radiotherapy on the lesion along the arc. In conventional volumetric intensity-modulated radiotherapy (IMRT), due to the structural limitations of the C-arm, the gantry cannot rotate continuously and must pause at a maximum angle of 180° and rotate in the opposite direction, i.e., the gantry performs a reciprocating rotation. Therefore, in this case, "arc" refers to the individual arcs (including single arcs with only one stroke) in multiple round trips of an arc.

[0032] In this invention, although details are left for later description, a gantry structure capable of continuous rotation around a complete circle is employed. This means that it does not need to turn back after reaching a certain position, but rather rotates continuously in the same direction. Therefore, the "arc" referred to in this invention can be any of multiple continuous complete circles. It is worth noting that although the gantry of this invention can rotate around a complete circle, the "arc" may not be a complete circle. For example, during radiotherapy for breast cancer, since the lesion is only located in the anterior chest, high-energy radiation may not be administered when the gantry rotates to the back of the body. That is, in this case, the "arc" is part of a complete circle. In other words, the "continuous rotation" referred to in this invention is not limited to the continuous arc itself used for radiotherapy; it can also include arcs not used for radiotherapy (idling arcs). As long as the gantry rotates continuously in the same direction without stopping or turning back, it falls under the category of continuous rotation as defined in this invention.

[0033] like Figure 1 As shown, the illumination field (subfield) formed by the multi-leaf collimator is simply illustrated by the diamond-shaped notch drawn on the illumination field forming unit 2.

[0034] The slip ring 3 is a multi-channel conductive slip ring fixed on the ring frame 4. It is responsible for transmitting power and data between the rotating part of the frame body and the stationary part connected to it. The stationary part is connected to the power supply cable and data cable. The use of slip ring to replace the power supply cable avoids the cable tangling during the frame rotation process, thus allowing the frame to rotate continuously.

[0035] The frame 4 is a continuously rotatable annular frame, and all or part of the stroke of the frame rotating to complete a circle constitutes an arc. In an arc, the irradiation field under any beam direction constitutes a subfield under that beam direction.

[0036] Understandably, within an arc, similar to the irradiation plan of a single arc in traditional volumetric modulated radiotherapy (VMR), as the gantry 4 rotates one arc, the subfield changes according to the shape of the lesion under that beam direction. However, traditional VMR cannot achieve continuous rotation and has pauses during re-entry, thus it can only rotate at a speed of 1 revolution (1 arc) / minute, making it impractical to plan radiation for too many arcs. In other words, traditional VMR requires planning the largest possible subfield area under any beam direction to avoid an excessive number of arcs.

[0037] In contrast, in this invention, because the gantry 4 rotates continuously, it can rotate at extremely high speeds. Thus, even with a large number of planned arcs, the irradiation time will not be excessively prolonged, thus not burdening the patient. Based on this, more arcs can be planned in this invention, and the subfields under any beam direction of each arc can be planned to have smaller areas.

[0038] Furthermore, for any beam direction, the subfields of each arc collectively constitute the irradiation field under that beam direction. That is, the subfields in this invention are different from the subfields in intensity-modulated radiotherapy. They are not composed of multiple subfields executed at the same time (at the same angle), but rather of multiple subfields executed in different time sequences (different arcs).

[0039] The control system 5 generates various commands for controlling the radiation generation unit 1, the irradiation field forming unit 2, and the frame 4, indicating the rotation of the frame 4, as well as the radiation dose generated by the radiation generation unit 1 and the size and shape of the subfield formed by the irradiation field forming unit 2 at each rotation angle (beam direction).

[0040] Based on the above structure, this application proposes a method for generating volumetric intensity-modulated radiotherapy (IMRT) plans, comprising the following steps: setting multiple control points for any irradiation angle of the lesion based on lesion parameters; generating multiple subfields corresponding to the closed state of the multi-leaf grating corresponding to each of the multiple control points for any irradiation angle of the lesion, wherein the multiple subfields constitute the irradiation field corresponding to the irradiation angle; generating a subfield execution sequence file for each subfield of the irradiation field at any irradiation angle of the lesion; and generating a multi-arc IMRT plan containing n arcs based on the subfield execution sequence files at each irradiation angle.

[0041] In this context, control points refer to a set of dose projection parameters set at a specific irradiation angle based on the three-dimensional morphology of the lesion and dose distribution requirements. These can be determined using medical imaging data combined with dose calculation algorithms, guiding the dynamic adjustment of beam dose and multi-leaf grating blade morphology. Multiple subfields in a closed state refer to multiple independent and overlapping irradiation areas formed by multi-leaf grating blades at the same irradiation angle. This is achieved through the coordinated movement of the multi-leaf grating blades during multi-arc rotation, ensuring each subfield has a clearly defined dose contribution area. The subfield execution sequence file is a set of timing control instructions recording the subfield execution order and corresponding beam parameters. It can be stored in XML or binary format and used to coordinate the synchronous control of the radiation source beam and the multi-leaf grating blade movements. A multi-arc volumetric intensity-modulated radiotherapy (IMRT) plan refers to a treatment plan containing multiple continuous rotating arcs. This is achieved by the control system sequentially executing subfield sequences corresponding to the gantry angles during continuous gantry rotation, with each rotating arc corresponding to a complete 360-degree gantry rotation cycle.

[0042] Specifically, this method first acquires the spatial location and dose requirements of the lesion through medical imaging, and sets multiple control point parameters at each gantry angle. Based on the control point parameters, the corresponding multi-leaf grating leaf closure shape is generated, forming multiple independent subfields. The beam dose parameters and MLC execution sequence of each subfield are encoded into a timing control file, which is executed in real time by the control system during irradiation to ensure precise synchronization between subfield switching and dose delivery during gantry rotation. By integrating the subfield sequence files of all irradiation angles, a multi-arc continuous execution scheme is constructed, enabling continuous irradiation of multiple rotating arcs without gantry interruption. During implementation, the multi-leaf grating dynamically adjusts its shape according to the preset sequence, coordinating with the gantry rotation speed to achieve a multi-subfield intensity-modulated dose delivery mode.

[0043] Compared with existing technologies, this solution achieves breakthrough multi-field intensity modulation during rotating irradiation, obtaining more precise dose distribution control by dynamically adjusting the multi-leaf grating morphology. Simultaneously, the innovative multi-arc continuous execution mechanism eliminates gantry downtime, transforming the traditional staged execution method into a seamless continuous irradiation mode. This combination of technologies effectively overcomes the dual technical obstacles of insufficient dose modulation in single-arc irradiation and low efficiency in multi-arc execution.

[0044] Through the above technical solutions, this application can significantly improve the conformity and uniformity of dose distribution while maintaining the efficiency of rotational irradiation. For tumor target areas with complex anatomical structures, effective avoidance of sensitive organs can be achieved through multi-field combination. The continuous multi-arc execution mode reduces gantry movement time loss and lowers the risk of patient positional movement during treatment, providing a safer and more efficient treatment plan for clinical practice.

[0045] This application further proposes a subfield execution sequence file containing the beam dose and execution sequence of each of the multiple subfields of the irradiation field at the irradiation angle.

[0046] Among them, beam dose refers to the radiation intensity that each subfield needs to apply during irradiation, which can be achieved through dose rate modulation or rotational irradiation time control to precisely regulate the dose contribution of different subfields to the target area. Execution sequence refers to the activation order of multiple subfields during irradiation, which can be determined through preset timing logic or dynamic adjustment algorithms to ensure that the multi-leaf grating switches subfield morphologies in a predetermined order.

[0047] Specifically, during rotational irradiation, the irradiation field at each irradiation angle is divided into multiple subfields with different shapes and dose parameters. The beam dose parameters provide a quantitative benchmark for the radiation intensity of each subfield; for example, a gradient dose allocation strategy is employed, ensuring that high-dose subfields cover the tumor core region and low-dose subfields cover the peripheral region. The execution sequence for multi-arc irradiation is arranged and combined along the time axis, using alternating switching or progressive transitions, to ensure the continuity of subfield morphological changes at adjacent angles. The multi-leaf grating dynamically adjusts the leaf positions according to the execution order in the sequence file, achieving continuous switching between different subfields during rotation, thereby completing multi-subfield intensity-modulated irradiation within multiple rotational arcs.

[0048] Compared to existing technologies, traditional single-arc or dual-arc volumetric intensity-modulated radiotherapy (IMRT) can only use one or two subfields for irradiation at each incident angle, and cannot optimize dose distribution through multi-subfield stacking. This approach dynamically switches multiple subfields and independently controls their dose parameters during multi-arc rotational irradiation, enabling multi-subfield dose modulation similar to IMRT at each incident angle. This allows for a more precise balance between target dose coverage and normal tissue avoidance in complex anatomical structures.

[0049] Through the above technical solution, this application can realize multi-subfield intensity modulation function during rotational irradiation, solve the problem of insufficient tumor target dose or excessive irradiation of normal tissue caused by the inability to perform subfield-level dose modulation in single-arc or double-arc irradiation mode, and improve the conformity and safety of radiotherapy planning in complex cases.

[0050] This application further proposes that, in the step of generating the subfield execution sequence file, the execution sequence of multiple subfields of the irradiation field at each irradiation angle is determined based on the beam dose of each subfield of the irradiation field at adjacent irradiation angles.

[0051] Among them, the beam dose of each subfield of the irradiation field at adjacent irradiation angles refers to the radiation dose parameters corresponding to each subfield at the rotation angle of adjacent gantry. Specifically, it can be quantified by combining the dose calculation model with the spatial position relationship, and is used to characterize the correlation of dose distribution between adjacent angles.

[0052] The execution sequence refers to the order in which subfields are executed during gantry rotation. Specifically, the execution order of subfields can be arranged and combined using optimization algorithms to eliminate abrupt changes in dose delivery between adjacent angles.

[0053] Specifically, during the continuous rotation of the gantry, subfield beam dose data from adjacent irradiation angles are simultaneously collected and correlated. By establishing a dynamic mapping model of dose parameters for adjacent subfield angles, the dose parameters of the current subfield angle are compared and calculated with the dose values ​​of the corresponding subfield angles from the previous angle. When a situation is detected where the dose gradient change between adjacent angles is too large, the sequence generation module will prioritize the arrangement of subfield combinations with dose continuity, for example, alternating between subfield groups with dose increment patterns and subfield groups with dose decrement patterns. For adjacent subfields with dose abrupt changes, the system will automatically insert transitional dose subfields or adjust the execution order to ensure a smooth transition in dose delivery at each angle during gantry rotation.

[0054] Compared to existing technologies, traditional volumetric intensity-modulated radiotherapy (IMRT) only considers dose parameters for a single angle during subfield sequence generation, leading to the risk of dose jumps between adjacent angles. This approach introduces an adjacent angle dose correlation mechanism to achieve pre-control of dose continuity during sequence generation, effectively avoiding tomographic distribution of actual irradiated dose caused by mismatch between gantry rotation speed and dose delivery rate.

[0055] Through the above technical solution, this application can ensure that the dose distribution of each irradiation angle is naturally connected during the multi-arc continuous rotation process, significantly reduce the probability of dose hotspots and colds in the target area, and effectively avoid the problem of gantry rotation pause due to dose projection deviation exceeding the threshold during rotation irradiation, thereby improving the accuracy and efficiency of radiotherapy equipment plan execution.

[0056] This application further proposes that, during the process of generating subfield execution sequence files, the execution sequence of multiple subfields of the irradiation field at each irradiation angle is determined based on the morphology of each subfield of the irradiation field at adjacent irradiation angles.

[0057] The morphology of a subfield refers to its geometric shape features, which can be described using the position coordinates of multi-leaf grating blades. Morphological differences between adjacent subfields are extracted using parametric models or image processing techniques to optimize the execution sequence.

[0058] The execution sequence refers to the order in which subfields are executed during rotational irradiation, which can be generated using a sorting algorithm based on morphological similarity. By comparing the morphological parameters of adjacent angular subfields, subfields with smaller morphological differences are executed first, thereby reducing the mechanical adjustment range of the multi-leaf grating blades, improving the blade positioning accuracy, and effectively avoiding the problem of gantry rotation pause due to multi-leaf grating blade positioning deviations exceeding the threshold during rotational irradiation, thus improving the accuracy and efficiency of radiotherapy plan execution.

[0059] Specifically, when switching between subfields at adjacent illumination angles, the subfield with the highest similarity to the candidate subfield at the next angle is selected as the next target for execution by calculating the morphological similarity between the current subfield and the next candidate subfield. The morphological similarity can be calculated based on the Euclidean distance of the blade position coordinates. When the morphological differences between adjacent subfields are small, the multi-leaf grating blades only need to make a small adjustment to complete the switching, without the need for acceleration by the blade drive motor, thereby reducing blade positioning error and mechanical movement delay. At the same time, the continuous and gradual change in subfield morphology ensures a smooth transition in the spatial distribution of beam dose, avoiding dose hotspots or colds caused by abrupt shape changes.

[0060] Compared to existing technologies, traditional methods do not consider the morphological correlation between adjacent angles when determining the subfield execution sequence. This leads to frequent large-scale position adjustments and acceleration movements of multi-leaf grating blades, resulting in positioning accuracy deviations and dose distribution fluctuations. This proposed solution introduces morphological similarity as a basis for sequence arrangement, resulting in shorter blade movement paths and fewer adjustments during adjacent subfield switching, thereby improving mechanical positioning accuracy and execution efficiency. Furthermore, the execution sequence based on morphological continuity maintains spatial coherence of dose delivery, improving dose uniformity in radiotherapy planning.

[0061] Through the above technical solution, this application solves the problems of blade mechanical positioning error, low motion efficiency, and uneven dose distribution caused by large differences in the shape of adjacent subfields during volumetric intensity-modulated rotary radiotherapy. By optimizing the subfield execution sequence, reducing the ineffective motion time of multi-leaf grating blades, and ensuring a smooth transition of field shape changes, the synergistic optimization of efficient mechanical execution and precise dose delivery is ultimately achieved.

[0062] This application further proposes that when generating a multi-arc volumetric intensity-modulated radiotherapy plan containing multiple arcs, the subfield to be executed in each arc is determined according to the execution sequence of multiple subfields of the irradiation field at each irradiation angle.

[0063] Here, multiple arcs refer to multiple complete circular motion trajectories formed by the continuous rotation of the radiotherapy equipment gantry. Each arc includes an execution section and an idle section. The execution section is used to complete subfield irradiation at the corresponding angle according to the subfield execution sequence, while the idle section is used to adjust the gantry position without irradiation. Specifically, this can be achieved by dynamically switching subfield parameters during the continuous rotation of the gantry. By matching the subfield execution sequence with the gantry rotation angle in real time, seamless connection between different arcs is ensured.

[0064] Among them, the subfield execution sequence refers to the pre-established subfield execution order and parameter set corresponding to the irradiation angle. Specifically, it can be achieved by optimizing the subfield morphology and beam dose of adjacent irradiation angles to match and associate them, so that the corresponding subfield parameters can be automatically called when the gantry is rotated to a specific angle, avoiding dose discontinuity or shape abrupt change during execution.

[0065] Specifically, during the continuous rotation of the gantry, each arc is assigned a sub-field sequence within a specific angular range. When the gantry rotates clockwise, the control system executes the sub-field sequence corresponding to the first arc; after completing one revolution, the gantry can continue rotating clockwise to begin the second arc without stopping, and execute the sub-field sequence assigned to that arc. The sub-field parameters are dynamically retrieved from the preset execution sequence based on the real-time rotation angle of the gantry, allowing for switching of rotating arcs without stopping the machine to change direction during multi-arc execution. By binding the sub-field execution sequence with the rotation direction and angle, the automatic execution of the multi-arc irradiation plan is achieved during continuous gantry rotation.

[0066] Compared to existing technologies, traditional dual-arc volumetric modulated radiotherapy (IMRT) requires pausing gantry rotation and reversing it after each arc is completed, leading to prolonged treatment time. Furthermore, deviations in gantry angle positioning occur during deceleration and acceleration, reducing the accuracy of rotational irradiation. This proposed solution dynamically allocates subfield execution sequences to multiple arcs, enabling the slip-ring gantry to automatically switch between different arc subfields during continuous rotation, eliminating the time loss and angle deviations caused by shutdowns and reversals.

[0067] Through the above technical solution, this application achieves continuous rotational irradiation of the gantry during multi-arc volumetric intensity-modulated radiotherapy, avoiding treatment interruptions caused by performing two rotational arcs in stages as in traditional methods. This solution effectively shortens the overall treatment time, improves the operating efficiency and execution accuracy of radiotherapy equipment, and is particularly suitable for scenarios requiring multi-arc irradiation in tumor cases with complex spatial structures.

[0068] This application further proposes that each arc includes an execution part and an idle part, the execution part and the idle part constituting a 360° rotation, and multiple arcs are executed continuously.

[0069] The execution section refers to the segment during gantry rotation where radiation is actually delivered. This is achieved by controlling the radiation source's output dose rate and the multi-leaf grating's subfield formation through a control system, ensuring precise delivery of the therapeutic dose within a specific angular range. The idling section refers to the segment during gantry rotation where radiation is not delivered. This is achieved by shutting down the radiation source or maintaining complete shielding of the multi-leaf grating, maintaining the continuity of gantry rotation and connecting the execution flow of adjacent arcs.

[0070] Specifically, upon completing a full 360° rotation, the gantry first performs radiation irradiation within a preset angle range. During this time, the multi-leaf grating dynamically adjusts its window shape according to the subfield execution sequence file, and the radiation source outputs a beam at a predetermined dose rate. When the gantry rotates to a non-irradiation angle range, the radiation source stops outputting, the multi-leaf grating leaves remain closed, and the gantry continues to rotate but does not perform any treatment operations. By alternately setting the rotation ranges of the execution and idle sections, multiple arcs allow the gantry to continuously complete multiple rotational treatments without changing its rotation direction or pausing midway.

[0071] Through the above technical solution, this application realizes the continuous operation of the gantry during multi-arc volumetric intensity-modulated radiotherapy, avoiding the invalid waiting time caused by mechanical limitations of traditional equipment, thus improving the time efficiency of the treatment process, reducing the risk of discomfort to patients due to prolonged treatment time, and improving the accuracy of gantry rotation into position.

[0072] This application also includes a volumetric intensity-modulated radiotherapy device, which has a radiation source that emits radiation, a slip ring gantry that carries the radiation source and can rotate continuously for multiple cycles, and a multi-leaf grating that can adjust the shape of the shielding to form a subfield window. The device executes a subfield sequence file containing set control points through a control system to realize the irradiation of the designed multi-arc radiotherapy plan.

[0073] The multi-rotation gantry refers to a support structure capable of completing multiple 360-degree rotations in the same direction. This can be achieved using a circular track and a drive motor, with power and signal transmission to the main unit mounted on the rotating gantry via a slip ring assembly. The rotation direction does not need to be reversed after each rotation. This feature allows the equipment to continuously execute multiple rotational arcs without pausing, solving the problem of non-continuous rotation caused by traditional C-arm and circular gantry gantry systems that use cables for power and signal transmission to the main unit. The multi-leaf collimator forming subfield window refers to creating transmission areas of different shapes along the radiation path by dynamically adjusting the position of the multi-leaf collimator blades. This can be achieved using an electrically driven blade array combined with real-time control signals. This feature allows for dynamic adjustment of the beam shape during continuous rotation, enabling precise control of dose distribution in conjunction with subfield sequences.

[0074] Specifically, during continuous rotation, the gantry drives the radiation source along a circular trajectory. The multi-leaf grating adjusts its leaf positions in real time according to a pre-set subfield execution sequence, forming a subfield window corresponding to the current rotation angle. Radiation irradiates the lesion through the dynamically changing subfield window, while the gantry continues to rotate to complete multiple arcs of irradiation. During the rotation of each arc, the shape of the subfield window and the beam dose are dynamically adjusted according to control point parameters. The dose distributions of multiple arcs are superimposed to form an optimized treatment plan. Through the synergistic effect of the gantry's uninterrupted rotation capability and the dynamic control of the subfield sequence, continuous execution of multi-arc volumetric modulated radiotherapy is achieved.

[0075] Compared to existing technologies, traditional C-arms and ring gantry systems, due to mechanical limitations, require a single rotation followed by a stop and reverse rotation, necessitating phased execution of multi-arc processes. This solution utilizes a gantry structure capable of continuous multi-rotation, allowing multiple rotational arcs to be performed continuously without interruption. Existing equipment requires re-acceleration and position recalibration during reverse rotation, leading to prolonged treatment time and angular deviations during gantry acceleration. This solution eliminates the rotation direction switching step, directly reducing gantry idle time and avoiding positioning deviations caused by gantry acceleration. Furthermore, traditional equipment, limited by unidirectional rotation capabilities, cannot superimpose multi-field dose distributions across multiple arcs during continuous rotation. This solution, through the coordination of continuous gantry rotation and dynamic subfield adjustment, achieves continuous accumulation of multi-arc, multi-field dose distributions, further optimizing dose distribution in the target area and surrounding normal tissues.

[0076] Through the above technical solution, this application solves the problem of low multi-arc execution efficiency caused by the limited rotation of the gantry in traditional radiotherapy equipment, realizing continuous execution of multi-arc volumetric intensity-modulated radiotherapy, avoiding time loss and positioning errors caused by gantry pauses and reverse rotation, shortening the overall treatment time and improving irradiation accuracy. At the same time, through the coordinated control of dynamic subfield windows and continuous rotation, the precise superposition of multi-arc dose distribution is ensured, improving the dose optimization capability in complex lesion conditions.

[0077] Next, refer to Figure 2 Flowcharts and Figure 3 The schematic diagram of the radiotherapy plan illustrates the volumetric intensity-modulated radiotherapy plan generation method of the present invention.

[0078] like Figure 2 As shown, this embodiment takes "high-resolution volumetric intensity-modulated rotational radiotherapy for abdominal tumors" as an example to simulate the specific implementation process on an accelerator. The steps are as follows: Step S1: Equipment and Phantom Preparation. Using a 6MV ring linear accelerator equipped with slip ring technology that enables continuous rotation, the simulated abdominal tumor phantom (including the target area and surrounding normal organ simulation structures) is placed at the designated position on the treatment bed to complete the phantom positioning and calibration.

[0079] Step S2, Multi-arc scheme setting. A multi-arc rotation irradiation scheme is composed of four 360° rotating arcs (Arci, i=1,…,4). The rotation direction of the four arcs is consistent to ensure that the beam can cover the abdominal tumor target area from different angles, while avoiding sensitive organs such as the spinal cord and kidneys.

[0080] Step S3, Control Point Parameter Configuration. For each rotation arc, with each 1° angle as a control node, control files for each node are pre-generated. The files contain the accelerator output dose rate at that angle (range: 100-1400 MU / min, dynamically adjusted according to the target depth and thickness) and the MLC blade position (calculated based on the projected shape of the target area and organs at risk at that angle).

[0081] Step S4: Multi-arc continuous irradiation is performed. The accelerator is started, and the control system continuously executes the irradiation task of four rotating arcs in a preset sequence. During the irradiation process, the accelerator control system reads the parameter files of each control node in real time and synchronously adjusts the dose and MLC shape to ensure that the irradiation at each angle meets the dose and shape requirements.

[0082] Step S5, Treatment End and Verification. After all four rotation arcs have been completed, the accelerator is stopped, the simulation phantom is removed, and the actual radiation dose to the target area and normal organs within the phantom is detected using a dose verification device to confirm that the dose distribution meets the preset requirements, thus completing one simulated treatment.

[0083] It is worth noting that the above example uses four 360° arcs, but the number of arcs and the angle range of each arc are not limited to this and can be flexibly set as needed.

[0084] The result, such as Figure 3 As shown, intensity-modulated radiotherapy (IMRT) with multiple subfields can be achieved through the combination of multiple consecutive arcs. The figure illustrates the gantry rotation trajectory, the position of the MLC blades, and a schematic diagram of target dose modulation displayed on the body surface, where the dark gray area represents the high-dose region and the light gray area represents the low-dose region.

[0085] Compared with the prior art, the beneficial effects of the present invention include at least the following: Complementary advantages: It fully integrates the advantages of "precise target dose modulation" of intensity-modulated radiotherapy (IMRT) and "flexible organ avoidance under all-round irradiation" of volumetric intensity-modulated rotational radiotherapy (VMAT), thus solving the limitations of the single mode of existing technologies.

[0086] Strong adaptability to complex target areas: By superimposing and modulating multiple subfields in the incident direction, it can accurately address complex lesions in which the tumor and surrounding sensitive organs are closely intertwined, effectively balancing the clinical needs of "sufficient tumor dose" and "protection of normal tissue".

[0087] Wide clinical applicability: It does not rely on new linear accelerator hardware as a radiation source. It can be achieved through multi-arc optimization combination based on existing known accelerator irradiation technology and gantry structure design (continuous rotation of slip ring gantry, MLC intensity modulation, dose rate adjustable VMAT, etc.), which reduces the cost of clinical promotion and facilitates the upgrade and application of existing radiotherapy equipment.

[0088] Better dose distribution: By simultaneously regulating the dose rate and MLC shape in the incident direction, the uniformity and conformity of the dose in the target area are significantly improved, while further reducing the radiation dose to surrounding normal tissues and reducing the toxic side effects of radiotherapy.

[0089] The above description is merely an embodiment of this application and is not intended to limit the scope of protection of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for generating volumetric intensity-modulated radiotherapy plans, characterized in that, The steps include the following: Based on the lesion parameters, multiple control points are set for any irradiation angle of the lesion; For any irradiation angle of the lesion, multiple subfields are generated corresponding to each of the multiple control points, consisting of beam dose and multileaf grating closure state. These multiple subfields constitute the irradiation field corresponding to the irradiation angle. For each subfield of the irradiation field at any irradiation angle of the lesion, generate a subfield execution sequence file; Based on the subfield execution sequence files at each irradiation angle, a multi-arc volumetric intensity-modulated radiotherapy plan containing n arcs is generated.

2. The method for generating volumetric intensity-modulated radiotherapy plans according to claim 1, characterized in that, The subfield execution sequence file contains the beam dose and execution sequence for each of the multiple subfields of the irradiation field at that irradiation angle.

3. The method for generating volumetric intensity-modulated radiotherapy plans according to claim 2, characterized in that, In the step of generating subfield execution sequence files, the execution sequence of multiple subfields of the illumination field at each illumination angle is determined based on the morphology of each subfield of the illumination field at adjacent illumination angles.

4. The method for generating volumetric intensity-modulated radiotherapy plans according to claim 2, characterized in that, In the step of generating subfield execution sequence files, under the premise that the morphological change of each subfield of the irradiation field at adjacent irradiation angles is not large, the execution sequence of multiple subfields of the irradiation field at each irradiation angle is further optimized and determined based on the beam dose change of each subfield of the irradiation field at adjacent irradiation angles.

5. The method for generating a volumetric intensity-modulated radiotherapy plan according to any one of claims 1-4, characterized in that, In the step of generating a multi-arc volumetric intensity-modulated radiotherapy plan containing n arcs, the subfields of the irradiation fields at each irradiation angle to be executed for each arc are determined according to the execution sequence of multiple subfields of the irradiation field at each irradiation angle.

6. The method for generating volumetric intensity-modulated radiotherapy plans according to claim 5, characterized in that, Each of the n arcs includes an execution part and an idle part, the execution part and the idle part forming a 360° rotation, and the n arcs are executed continuously.

7. A volumetric intensity-modulated radiotherapy device, characterized in that, have: A radiation source that emits radiation used in radiotherapy; The frame, which carries the radiation source, is capable of rotating continuously for multiple cycles; Slip rings are used to transmit power and signals to the main unit of the equipment mounted on the rotating frame. Multileaf gratings can adjust the shape of the occlusion to form a window, or subfield, that allows radiation to pass through; as well as The control system is used to control the radiotherapy equipment to execute the control point sequence file of the prescribed treatment plan, thereby realizing the irradiation scheme specified in the treatment plan. The volumetric intensity-modulated radiotherapy device performs the volumetric intensity-modulated radiotherapy planning generation method according to any one of claims 1-6.

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