Radiation Therapy Treatment Planning and Delivery Vehicles

Abstract

The radiation therapy treatment plan is constructed to take into account geometric changes in the heart that occur during the heartbeat, to define the treatment phases in which radiation should be delivered during each heartbeat, and to ensure that the radiation hits the intended target. The plan is optimized using an optimization problem setup to include information about the treatment phases and to define the planning objectives.

Description

[Technical field]

[0001] Technical Field

[0001] The present invention relates to radiotherapy treatment planning involving any type of radiotherapy treatment involving photons or charged particles such as electrons, photons or other ions, and to an apparatus and computer program for such treatment planning. The present invention also relates to an apparatus and computer program for delivering the radiotherapy treatment. [Background technology]

[0002] background

[0002] The main objective of radiation therapy treatment planning is to devise a plan that ensures a desired dose to a target, such as a tumor, and a low dose to healthy tissue. At the same time, any particular susceptible organ or tissue near the target may require zero dose, or as close to zero dose as possible. Typically, radiation therapy involves administering a total dose that is divided into several parts, often called fractions. When delivering the dose by conventional techniques, the delivery of one fraction takes, for example, on the order of one minute.

[0003]

[0003] In some cases, the patient side under treatment will move during the treatment fraction. For example, treatment of the chest will be affected by the patient's breathing. Various techniques exist to deal with this, including robust planning, following the target's motion, or restricting breathing for a certain period of time. A breathing cycle usually takes on the order of magnitude of 10 seconds. Another method involves gating the beam in view of the motion, so that it is on only during periods when the target and any organs at risk are in a well-defined position, for example at the end of each exhalation or while the patient is holding his breath.

[0004]

[0004] In radiotherapy treatments, the heart can be either side of the treatment volume or organ at risk, e.g. in the treatment of lung or thoracic tumors or breast cancer. In both these cases, the motion of the heart poses particular problems. In the former case, calculating the cumulative dose to a particular part of the heart means tracking that part throughout each heartbeat. In the latter case, the heart as an organ at risk should be avoided as much as possible, ideally not receiving any dose at all.

[0005]

[0005] A typical frequency of the heart is approximately 1 Hz, meaning that the dose to a particular location in the heart is a cumulative result of the details of the delivery timing and the cardiac motion of the heart. Any point in the heart can move on the order of magnitude of a few centimetres over a heartbeat. Traditionally, the effects of this motion are addressed in one of the following ways:

[0006]

[0006] One way to take cardiac motion into account is as follows: the heart is imaged by cardiac CT and a series of images are acquired over the cardiac cycle. Typically there is one image every 100 ms over a 2 second cycle. This is similar to the standard 4dCT image series used in treatment planning, for example in the thoracic region (lungs), where each image covers a 1 second interval and there are a total of 10 such phases. This complex accumulation can be analyzed through a so-called interplay evaluation. Alternatively or additionally, the influence of cardiac motion delivery dynamics can be reduced by robust optimization techniques. Both are complex and time consuming. Summary of the Invention [Problem to be solved by the invention]

[0007] Summary of the Invention

[0007] An object of the present disclosure is to provide a radiation therapy treatment planning method and system that generates plans that compensate for heart rate related motion with lower complexity than the prior art. [Means for solving the problem]

[0008]

[0008] One aspect of the present disclosure is a computer-implemented method for obtaining a radiation therapy treatment plan for a patient, the method comprising: - obtaining a 4D image of the heartbeat; - deriving from the 4D image a treatment phase of the heartbeat during which radiation should be delivered to the patient; - obtaining an optimization problem, said optimization problem defining a planning objective including information about a treatment phase; optimizing values ​​of a set of planning parameters to achieve a planning objective such that radiation is delivered only during the treatment phase; Includes.

[0009]

[0009] The planning parameters typically also include standard planning parameters that will depend on the treatment modality. For example, in proton-based pencil beam scanning (PBS), the planning parameters also include standard planning parameters such as spot weights. The planning objective is typically defined to ensure a uniform dose to the target while avoiding other tissues, especially organs at risk. The step of obtaining the optimization problem may include formulating the optimization problem based on the current patient anatomy or using a previously formulated optimization problem.

[0010]

[0010] The set of planning parameters may also include model parameters that specify the nature of a modulation device to be used to modulate the beam during delivery. Such a modulation device is configured to modulate the beam energy differently in different sub-areas across the beam area, thus enabling conformal treatment while using only one energy layer.

[0011]

[0011] In some preferred embodiments, the optimization step is performed such that radiation is delivered during a treatment phase of only one heartbeat. Due to the short delivery times involved, this would typically require higher dose rates than those typically used today, but such high dose rates are achievable with standard equipment. Due to the short delivery times, interplay effects and other problems associated with organ motion are eliminated or greatly reduced.

[0012]

[0012] In other preferred embodiments, the optimization step is performed such that radiation is delivered during treatment phases of two or more heartbeats. This allows for changes between treatment phases, such as changes in energy layers and / or gantry angles, which typically cannot be done within one heartbeat. Thus, treatment can be delivered from one direction or from more than one direction.

[0013]

[0013] Obtaining a suitable optimization problem and using it to optimize the compensation device allows for a fast and reliable design of the compensation device as specified, which also allows other advantageous aspects to be taken into account in the design process, such as robustness, linear energy transfer (LET)-based objectives or relative biological effectiveness (RBE)-based objectives.

[0014]

[0014] The present disclosure also relates to a computer program product comprising computer readable code means which, when executed on a computer, causes the computer to carry out the planning method as discussed above, and a computer system for executing such a computer program. The computer program product may comprise non-transitory storage means in which the code means are stored.

[0015]

[0015] The present disclosure also relates to a computer program product comprising a radiation therapy delivery system and computer readable code means for controlling such a delivery system. The computer program product may comprise non-transitory storage means in which the code means are stored.

[0016]

[0016] Such a computer program product for controlling delivery of fractions of a radiation therapy treatment plan to a patient is configured to perform the following steps: - receiving heart rate data relating to the patient's heart rate rhythm; - identifying a period of time within a heartbeat as a treatment phase during which radiation should be delivered based on said heartbeat data; - Controlling delivery such that radiation is delivered to the patient only during an identified treatment phase of one or more heartbeats.

[0017]

[0017] The computer program product may be configured to control the delivery of the fraction during an identified treatment phase at one heartbeat or during treatment phases at two or more heartbeats. If radiation is delivered at a treatment phase at only one heartbeat, the dose rate must be adapted so that the entire fractional dose can be delivered within a very short time, on the order of magnitude of 1 / 10th of a second.

[0018]

[0018] The methods according to the present disclosure are applicable to any radiotherapy treatment modality, including photons or charged particles. The charged particles may be electrons or ions. The most common form of ion-based radiotherapy is proton therapy.

[0019]

[0019] The present disclosure also relates to a radiation therapy delivery system for delivering a radiation therapy treatment plan, the radiation therapy delivery system comprising a data memory for holding the treatment plan obtained in accordance with the method defined above, and a control unit configured to control the radiation therapy delivery system in accordance with the treatment plan.

[0020] BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0021] [Figure 1] 1 is a flow chart of a method of delivering therapy according to the present disclosure. [Diagram 2] 1 is a flow chart of a treatment planning method according to the present disclosure. [Diagram 3] FIG. 2 is a schematic diagram of a beam modulation device that may be used in connection with the methods described herein. [Figure 4] FIG. 1 is a schematic diagram of a computer system that may be used for treatment planning. [Diagram 5] FIG. 1 is a schematic diagram of a therapeutic delivery system that may be used in connection with the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Detailed Description of the Embodiments

[0020] The method according to the present disclosure is based on the use of ECG data or other suitable data related to the heart rhythm to gate the beam delivery to the patient. This means that each beam must be delivered in a short time period, much shorter than one second. Different ways of accomplishing this are discussed below. Some embodiments of the method rely on the beam being delivered at a dose rate that is much higher than conventional dose rates, so that the entire fractional dose can be delivered in a fraction of a second.

[0023]

[0021] As discussed below, the method is based on determining a treatment phase for each heartbeat, which is the time window in which radiation should be delivered to the patient. This treatment phase can be selected so that the radiation avoids the heart or treats a specific part of the heart. In both cases, the motion of the heart must be taken into account.

[0024]

[0022] In some embodiments, delivery may be completed within a time frame of just one heartbeat. In that case, delivery must be at a dose rate high enough to deliver the entire fractional dose within just one treatment phase. One complete heartbeat is typically on the order of magnitude of 1 second, and a suitable phase for delivering the dose is a fraction of that, e.g., 1 / 10, or on the order of magnitude of 1.0 second. If the desired fractional dose is 2 Gy, this means that the dose rate must be 20 Gy / s.

[0025] Alternatively, the fractional dose may be delivered in several portions and gated to be delivered during the treatment phase of two or more heartbeats, with the beam being turned off during the remaining phases of the heartbeat.

[0026]

[0024] Some embodiments employ a means to ensure a conformal single energy layer dose distribution if the dose is to be delivered in one go. This may not be necessary if the delivery machine can change the energy layer within the time frame of the treatment phase, which is on the order of magnitude of 1 / 10th of a second. It may also not be necessary if the dose is distributed over several heartbeats so that the energy layers can be changed in between. In ion therapy, such a means can be, for example, a modulation device such as that disclosed in European Patent No. 20192106.1 by the same applicant. Such a modulation device is configured to adapt the beam to the target without the need to change the energy level of the beam.

[0027]

[0025] In most cases, information about chest motion is also required, since the heart moves with the patient's breathing. If the treatment is delivered over a very short period of time where the position of the heart relative to the beam does not change significantly, then information about the position of the heart at the time of treatment is required, but not about the motion of the heart.

[0028]

[0026] Figure 1 shows a possible method for delivering a treatment plan according to the present invention. Input data S11 includes a treatment plan configured to be delivered within a treatment phase of one or more heart beats. In step S12, the patient's heart beats are registered, for example using an ECG. This is performed continuously. In the ECG signal, the points in time when the heart is in the correct phase to deliver the beam are detected in step S13.

[0029] In step S14, gating is performed on the beam based on the detected time point to ensure beam delivery to the patient at the correct phase of the heartbeat.

[0030]

[0028] Delivery in several portions over several heartbeats can be performed from the same direction, but typically involves more than one beam angle. Radiation is usually delivered from more than one beam angle to reduce damage to healthy tissue. In proton therapy or other radiation therapy treatments involving charged particles that stop and deposit energy at a desired location within the patient, the full fractional dose can be delivered from fewer beam angles.

[0031]

[0029] Thus, the planning is based on one or more cardiac CT images. A phase during the heartbeat suitable for delivery of the beam is identified and is called the treatment phase. This is usually when the myocardium contracts so that the geometric expansion of the heart is small enough that the heart does not block the tissue that is to receive the beam. Beam gating is a well-known feature in other areas, for example based on the patient's breathing pattern. Gating may also be performed to ensure that radiation reaches certain parts of the heart instead of avoiding them.

[0032]

[0030] When the radiation modality is proton or other ionizing radiation, it is possible to deliver the entire dose within the treatment phase of one heartbeat. This requires a dose rate that is higher than conventional dose rates, which are usually around 1 Gy / s or less. A typical fractional dose is 2 Gy with a conventional delivery time of around 30-60 s, which means that the average dose rate across the treatment volume is on the order of magnitude of 0.03 Gy / s to 0.07 Gy / s. To deliver such a dose in 1 / 10 s, an average dose rate of 20 Gy / s is required. This is unconventional, but achievable with available delivery systems.

[0033]

[0031] With most prior art proton delivery devices, it takes approximately 0.5-1 s to charge the energy layer, meaning that it is not possible to charge the energy layer during delivery within one heartbeat. In such cases, an energy modulation device can be used to modulate the energy of the beam over the entire field so that the target is covered with the desired dose. An example of such an energy modulation device is described below with reference to FIG. 3. Another option is to split the fraction over several heartbeats and gate the delivery so that the beam is on only during a suitable part of each heartbeat (the "treatment phase"), and change the energy layer while the beam is off. That way, several energy layers can be delivered over a short period of time, taking into account the heart motion that occurs with every heartbeat. The gated delivery may be delivered from the same beam angle at each heartbeat or the beam angle may be changed so that at least some beams are delivered from different beam angles.

[0034]

[0032] In the case of photon radiation, it is usually necessary to deliver each fraction as several beams from different angles that intersect at the target, preferably an odd number of beams such as 3, 5, or 7 beams. That way, the dose to the target can be high enough while avoiding the surrounding tissue. In this case, the delivery can be gated so that each beam is delivered during the appropriate part of the heartbeat.

[0035]

[0033] The present disclosure is applicable to electron radiation as well as to ions as discussed above. Electrons are typically used to treat targets placed on the skin or up to 4-5 cm into the patient's body.

[0036]

[0034] Figure 2 is a flow chart of a method that may be used to optimize a treatment plan. Input data S21 to the method includes a set of planning parameters for the plan and an optimization problem S22. The input data includes standard planning parameters such as spot weights. The planning objective of the optimization problem is typically defined as ensuring a uniform dose to the target while avoiding other tissues, especially risk tissues.

[0037]

[0035] First, an optimization problem S22 to be used for optimizing the modulation device is also obtained. The optimization problem includes an objective function and / or constraints on how the input radiation should be affected by the modulation device. Obtaining the optimization problem may include formulating an optimization problem based on the current patient anatomy or using a previously formulated optimization problem. The optimization problem may be set up to include a modulation device of the design as described in the above-mentioned EP 20192106.1.

[0038] In step S23, optimization is performed based on the optimization problem to result in a treatment plan S24.

[0039]

[0037] The final optimization is performed with a single energy layer per beam. The final optimization can include one or more beams and any type of advanced objective function, such as a function related to RBE dose, LET, or robustness.

[0040]

[0038] An energy modulation device is included to ensure that the entire dose per beam can be delivered by one single energy layer. As mentioned above, in that case, the entire fraction can be delivered using only one beam during one treatment phase of a heartbeat, but may be distributed over several heartbeats and gated to provide radiation only during the treatment phase of each heartbeat. Alternatively, if the delivery system to be used when delivering the treatment to the patient is capable of switching between energy layers very quickly, optimization can be performed using two or more energy layers in each beam.

[0041]

[0039] Figure 3 discloses a passive modulation device 10 that can be used as an energy modulation device in the context of the present disclosure. The device 10 comprises a compensation element 11, which is basically a disk with a variable thickness over the area. The thickness is designed so that the input radiation field matches the tip of the target. On the disk are arranged several protrusions, typically in the form of spike-shaped structures 13 of the same material as the compensation element. The protrusions 13 are typically placed in a grid pattern on the disk, each of which is e.g. 1.5 x 1.5 mm in diameter. 2 The protrusions 13 have different heights and shapes selected so that the beam passing through the device is desirably modulated to have a Bragg peak that covers the entire target. Of course, the size, shape, and thickness of the compensating element, the arrangement of the protrusions on the compensating element as well as their size and height should be selected to suit the target.

[0042]

[0040] Further information on how to design and use such passive modulation devices can be found in European Patent No. 20192106.1.

[0043]

[0041] Figure 4 is a schematic overview of a computer system on which the optimization according to the invention can be carried out. The computer 41 comprises a processor 43, a data memory 44 and a program memory 45. Preferably, one or more user input means 47, 48 are also present in the form of a keyboard, a mouse, a joystick, voice recognition means and / or any other available user input means. The user input means may be arranged to receive data from an external memory unit.

[0044]

[0042] The treatment plan is found in the data memory 44. The treatment plan may be generated in the computer 41 or may be received from another storage means in any manner known in the art. The data memory also contains the characteristics of the dose delivery beams to be used in the actual treatment of the patient, i.e. the beams to be modulated by the compensation device.

[0045]

[0043] The data memory 44 also holds properties of the energy modulation device 10, such as the material composition of the energy modulation device 10, if a modulation device is to be used. If the material is known, its properties can be stored. As will be understood, the data memory 44 is shown only diagrammatically. There may be several data memory units, each data memory unit holding one or more different types of data, for example, there may be one data memory for the design of the compensation device, etc.

[0046]

[0044] The program memory 45 holds a computer program configured to control the processor to carry out the optimization procedure according to the invention. Like the data memory 44, the program memory may be implemented as one or several units as seen appropriate.

[0047]

[0045] Figure 5 is a schematic diagram of a delivery system that can be used according to the present invention, typically but not necessarily adapted to provide radiation to a patient from different directions. As will be appreciated, such a system can be designed in any suitable manner, and the design shown in Figure 5 is only one example. A patient 111 is positioned on a treatment couch 113. The system comprises a treatment unit 110, which is mounted on a gantry 117 and has a radiation source 115 that emits radiation towards the patient positioned on the couch 113. Typically, the couch 113 and the gantry 117 are movable in several dimensions relative to each other, thereby providing radiation to the patient as flexibly and precisely as possible. The gantry can be configured to rotate around the couch, either between specific angles or a full 360° rotation. Alternatively, the gantry can be fixed and the couch with the patient can rotate instead. Another alternative is to have the patient seated in a chair position. Arc treatment in this case can be performed by changing the beam direction or by rotating the chair. These parts are well known to those skilled in the art. The system also comprises a computer 121, which may be used for planning the radiation therapy treatment and / or for controlling the radiation therapy treatment. As will be appreciated, the computer 121 may be a separate unit that is not connected to the imaging unit.

[0048]

[0046] The computer 121 comprises a processor 123, a data memory 124 and a program memory 126. Preferably, one or more user input means 128, 129 are also present in the form of a keyboard, a mouse, a joystick, a voice recognition means or any other available user input means. The user input means may be arranged to receive data from an external memory unit.

[0049]

[0047] The data memory 124 contains data such as clinical data and / or other information used to obtain the treatment plan, including a set of clinical targets used in the plan. The data memory 124 also contains one or more dose maps for one or more patients to be used in the treatment plan according to an embodiment of the present invention. The program memory 126 holds computer programs, known per se, configured for treatment plan optimization. The program memory 126 also holds computer programs configured to cause a computer to control the treatment of a patient according to the present invention.

[0050]

[0048] It is understood that the data memory 124 and the program memory 126 are shown and discussed only generally. There may be several data memory units, each data memory unit holding one or more different types of data, or there may be one data memory that holds all data in a suitably structured manner, and the same is true for the program memory. One or more memories may be stored in another computer. For example, a computer may be configured to perform only one of the methods, and there may be another computer that performs the optimization.

Claims

1. 1. A computer-implemented method for obtaining a radiation therapy treatment plan for a patient, comprising: acquiring a 4D image of the heartbeat; deriving from the 4D image a treatment phase of the cardiac cycle during which radiation should be delivered to the patient; obtaining an optimization problem, the optimization problem defining a planning objective including information about the treatment phase; optimizing values ​​of a set of planning parameters to achieve the planning objective such that the radiation is delivered only during the treatment phase; 23. A computer-implemented method comprising:

2. The computer-implemented method of claim 1 , wherein the set of planning parameters includes model parameters that define properties of an energy modulation device to be used to modulate beam energy during delivery.

3. The computer-implemented method of claim 1 or 2, wherein the optimizing step is performed such that the radiation is delivered during the treatment phase for only one heartbeat.

4. The computer-implemented method of claim 1 or 2, wherein the optimizing step is performed such that the radiation is delivered during the treatment phase for two or more heartbeats.

5. The computer-implemented method of claim 5 , wherein the optimizing step is performed such that the radiation is delivered from two or more directions.

6. A computer program product comprising computer readable code means which, when executed on a computer, causes said computer to carry out the method of any one of claims 1 to 5.

7. 10. A computer system for optimizing a radiation therapy treatment plan, said computer system comprising: a program memory holding a computer program product according to claim 6; and a processor configured to execute said program.

8. A radiation therapy delivery system for delivering a radiation therapy treatment plan, said radiation therapy delivery system comprising a data memory for holding a treatment plan obtained according to the method of any one of claims 1 to 5, and a control unit configured to control said radiation therapy delivery system according to said treatment plan.

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