WO2012171538A1

WO2012171538A1 - Radiotherapy management system and methods

Info

Publication number: WO2012171538A1
Application number: PCT/EP2011/002945
Authority: WO
Inventors: Timothy PROSSER
Original assignee: Elekta Ab (Publ)
Priority date: 2011-06-15
Filing date: 2011-06-15
Publication date: 2012-12-20

Abstract

The present invention provides methods and apparatus for safely managing the provision of radiotherapy treatment potentially in many different locations around the world. A database is formed comprising allowable ranges for each of a plurality of parameters in a radiotherapy treatment plan. Prior to treatment, the parameters of a proposed treatment plan are compared to these allowable ranges to see whether the treatment should be allowed to continue. If one or more of the proposed parameters falls outside the allowable ranges, the therapy session may be stopped or prevented altogether.

Description

Radiotherapy management system and methods

FIELD OF THE INVENTION

The present invention relates to systems and methods for the management of radiotherapy treatment delivery.

BACKGROUND ART

Prior to beginning a course of radiotherapy, a plan for the treatment is constructed. The aim of the treatment plan is to establish how to apply the radiotherapy to the patient so that the target region receives the desired, lethal dose, whilst the surrounding healthy tissue receives as little dose as possible.

Radiotherapy is often delivered by a linear accelerator-based system, which produces a beam of high-energy x-rays and directs this toward a target area in a patient. The patient typically lies on a couch or patient support, and the beam is directed toward the patient from an offset location. During treatment, the beam source is rotated around the patient while keeping the beam directed toward the target point. The result is that the target remains in the beam at all times, but areas immediately around the target are only irradiated briefly by the beam during part of its rotation. By positioning (for example) a tumour at the isocentre of the beam, the dose to the tumour is maximised whilst the dose to surrounding healthy tissue is reduced. In addition, the cross-section of the beam can be varied by way of a range of types of collimator, such as the so-called "multi-leaf collimator" (MLC) illustrated in EP 0,214,314. These can be adjusted during treatment so as to create a beam whose cross-section varies dynamically as it rotates around the patient.

Other aspects of the radiotherapy apparatus can also be varied during treatment, such as the speed of rotation of the source and the dose rate. Thus, there are a large number of variables offered by the apparatus in order to tailor the radiation dose that is delivered to the patient.

Volumetric images are then analysed to identify a target region into which a minimum dose is to be delivered, any sensitive regions such as functional organs for which a maximum dose must be observed, and other non-target regions into which the dose is to be generally minimised. This three-dimensional map must then be used to guide a treatment plan, i.e. a sequence of source movements, collimator movements, and dose rates which result in a three-dimensional dose distribution that (a) meets the requirements as to maximum and minimum doses (etc) and (b) is physically possible, e.g. does not require the source to rotate around the patient faster than it is physically capable. This can be expressed as a mathematical problem in which the overall dose to healthy tissue must be minimised, subject to constraints as to the maximum dose to sensitive regions, the minimum dose to the target, and the various machine constraints such as the maximum rotation speeds, possible MLC shapes, etc. Although complex, the mathematical problem can be solved by one of a range of techniques (with varying efficiency) but this does require significant computing resources.

When treating a patient with radiation therapy, safety is of paramount importance. As mentioned previously, it is unavoidable that both the target region and healthy tissue are exposed to radiation during the treatment. However, if the user incorrectly sets up the machine/treatment parameters, it is possible that more healthy tissue is exposed to higher radiation levels than is necessary for effective treatment. In cases where the user has incorrectly configured the machine or treatment plan, it is harder for the system's own hardware/software interlocks to catch the error, as it was the user who directed the system to perform in such a way. SUMMARY OF THE INVENTION

In one aspect of the present invention, there is provided a method of radiotherapy management, comprising: forming a database of treatment plans, each treatment plan comprising a plurality of machine parameters, and deriving therefrom an allowable range for each of said machine parameters; receiving a proposed treatment plan for execution on a radiotherapy apparatus, said proposed treatment plan comprising a plurality of proposed machine parameters; comparing said plurality of proposed machine parameters to said allowable ranges for each of said machine parameters; and if one or more of the proposed machine parameters falls outside said allowable ranges, transmitting an alert message to a user of the radiotherapy apparatus.

In embodiments of the present invention, the actual machine parameters continue to be monitored during treatment. Thus, in these embodiments the method further comprises: during ensuing treatment, receiving a plurality of actual machine parameters; comparing said plurality of actual machine parameters to said allowable ranges for each of said machine parameters; and if one or more of the actual machine parameters falls outside said allowable ranges, transmitting an alert message to a user of the radiotherapy apparatus, or suspending operation of the radiotherapy apparatus.

In another aspect of the present invention, there is provided a method of preparing for radiotherapy, comprising: formulating a proposed treatment plan for execution on a radiotherapy apparatus for at least one session of radiotherapy, the treatment plan comprising a plurality of proposed machine parameters; sending the proposed treatment plan to a management apparatus comprising a database of treatment plans, each treatment plan comprising a plurality of machine parameters, and allowable ranges for said plurality of machine parameters; and receiving an alert message from said management apparatus if one or more of said proposed machine parameters falls outside said allowable ranges.

This aspect therefore relates to the user of the radiotherapy apparatus. Similarly, embodiments of the invention allow the method to continue during treatment. The method may therefore further comprise: during ensuing treatment, sending a plurality of actual machine parameters to said management apparatus; and receiving an alert message from said management apparatus or suspending operation of the radiotherapy apparatus if one or more of said proposed machine parameters falls outside said allowable ranges. The method according to any one of the preceding claims, wherein said plurality of machine parameters comprises one or more parameters selected from: an angle of rotation of a gantry of the radiotherapy apparatus, positions of leaves in a multi-leaf collimating apparatus, a position of a collimating wedge, an energy of the beam of radiation, the radiative dose to be delivered.

In embodiments of either aspect mentioned above, a set of allowable ranges is provided for each of a plurality of different forms of radiotherapy. Thus, an allowable range for a machine parameter in one form of radiotherapy may differ from the allowable for the same machine parameter in a different form of radiotherapy. Although the term "range" has been used above, in embodiments of the present invention this can comprise whether or not said machine parameters are present in said proposed treatment plan. In this context, the absence of a machine parameter from a treatment plan may constitute a parameter which is outside an allowable range (if the treatment plan should be present according to the database). If the machine parameter is non-essential to the treatment plan, its absence may not be considered as outside the allowable range.

In a yet further aspect of the present invention, there is provided a radiotherapy treatment management apparatus, comprising: a database comprising a plurality of treatment plans, each treatment plan comprising a plurality of machine parameters, and allowable ranges derived therefrom for said machine parameters; an input, for receiving from a user of a radiotherapy apparatus a proposed treatment plan for execution on that radiotherapy apparatus, said proposed treatment plan comprising a plurality of proposed machine parameters; comparison logic, for comparing said plurality of proposed machine parameters to said allowable ranges for each of said machine parameters; and an output, for transmitting an error message to the user of the radiotherapy apparatus if one or more of the proposed machine parameters falls outside said allowable ranges.

BRIEF DESCRIPTION OF THE DRAWINGS

An embodiment of the present invention will now be described by way of example, with reference to the accompanying figures in which; Figure 1 shows a system according to embodiments of the present invention; Figure 2 shows a flowchart of a method according to embodiments of the present invention, as performed in a radiotherapy management apparatus; and

Figure 3 shows a flowchart of a method according to embodiments of the present invention, as performed by a user of a radiotherapy apparatus. DETAILED DESCRIPTION OF THE EMBODIMENTS

Figure 1 shows a system 10 according to embodiments of the present invention. The system comprises a radiotherapy management apparatus 12 and a plurality of radiotherapy systems 18a, 18b. Each radiotherapy system is located in its operative environment, for example in the oncology department of a hospital. Each hospital may possess more than one radiotherapy system, but in general it is assumed the radiotherapy systems are in separate hospitals, potentially distributed around the world. It is further to be understood that, although only two radiotherapy systems are illustrated in Figure 1, the system according to embodiments of the present invention may (and generally will) comprise many such radiotherapy systems. The management apparatus 12 is able to communicate with each radiotherapy system 18a, 18b, either by wired or wireless communications, or by a combination of both wired and wireless. The apparatus 12 comprises an input 13, for receiving communications from the radiotherapy systems 18a, 18b, and an output 16, for sending communications to the radiotherapy systems 18a, 18b. Comparison logic 14 connects the two, and further has access to a database 15. The operation of the management apparatus 12 will be described in greater detail below. However, it will be apparent to those skilled in the art that the comparison logic 14 may be implemented using hardware or software as appropriate. The database 15 will generally be stored on non-volatile memory.

The management apparatus 12 itself may be local or remote to the radiotherapy systems 18a, 18b. For example, as illustrated, the system 10 may comprise a single management apparatus 12 with which each radiotherapy system communicates as necessary. Alternatively, the system may comprise a plurality of such management apparatuses, each able to access a central database (or periodically updating the contents of a local database based on the contents of a central database). The radiotherapy system assigned reference numeral 18a is generally indicative of the type of radiotherapy apparatus which may be employed in methods according to the present invention. The system 18a comprises a radiotherapy apparatus 20 in which a patient is supported by a suitable support apparatus 22. A radiation head 24 comprises a source of ionizing radiation having sufficient energy to produce a therapeutic effect in the patient (i.e. generally in the megavoltage range), and a collimating device to collimate that radiation into a beam of desired shape. In operation, the radiation head 24 is able to rotate around the patient such that the radiation beam is directed towards a target region in the patient as from a number of different angles. By positioning the target region at or near the rotation axis of the head 24, the radiation beam intersects the target region throughout rotation of the head, but passes through the surrounding tissue only momentarily. In this way, collateral damage to health tissue as a result of the treatment can be reduced.

The dashed-line projection in Figure 1 shows a beam's eye view of the collimating device in operation. A housing 26 defines a radiation field through which the radiation beam passes. In the illustrated embodiment, two banks of opposing leaves 28 are coupled to the housing 26 and extend across the radiation field to a greater or lesser extent as required. Each leaf is relatively thin in one direction, but relatively long in its direction of travel across the radiation field, and relatively deep in a direction parallel to the radiation beam axis (i.e. into the page in Figure 1). The depth of the leaf, together with the choice of a manufacturing material having high atomic number (such as tungsten), acts to effectively block that part of the radiation field, preventing radiation from passing through. Each leaf is individually controllable to take any position in the range from falling outside the radiation field to extending fully across the radiation field, and thus the plurality of leaves can be controlled to define collectively a radiation beam having a desired cross-sectional shape (for example, to match the shape of a tumour or other target within the patient). This type of device is known as a multi-leaf collimator (MLC). Other collimating devices are known, however (such as binary collimators and block collimators), and the present invention is equally applicable to radiotherapy systems employing these types of devices.

It will be apparent to the reader and to those skilled in the art that each course of radiotherapy involves control of a huge number of variables. Depending on the type of radiotherapy system employed, the variables may include: rotation angle of the radiation head; positions of the MLC leaves (or other collimating elements); energy of the beam; overall amount of radiation dose being delivered (i.e. the number of monitor units); rate of delivery of that dose; position of the "wedge" (an absorptive collimating element used to reduce skin dose in some methods of treatment); the type of treatment being delivered (e.g. electron therapy or x-ray therapy, etc); and the patient position. Thus, there are a large number of variables offered by the apparatus in order to tailor the radiation dose that is delivered to the patient. A treatment planning apparatus 30 (in practice a computing device implemented in hardware, software, or a combination of the two) is therefore provided, to generate a treatment plan and so control the radiotherapy apparatus 20 to provide a desired level of radiation dose to the patient. Volumetric images of the patient are analysed to identify a target region into which a minimum dose is to be delivered, any sensitive regions such as functional organs for which a maximum dose must be observed, and other non-target regions into which the dose is to be generally minimised. This three-dimensional map is then used to develop a treatment plan, i.e. a sequence of source movements, collimator movements, and dose rates which result in a three-dimensional dose distribution that (a) meets the requirements as to maximum and minimum doses (etc) and (b) is physically possible, e.g. does not require the source to rotate around the patient faster than it is physically capable.

This can be expressed as a mathematical problem in which the overall dose to healthy tissue must be minimised, subject to constraints as to the maximum dose to sensitive regions, the minimum dose to the target, and the various machine constraints such as the maximum rotation speeds, possible MLC shapes, etc. Although complex, the mathematical problem can be solved by one of a range of techniques (with varying efficiency) but this does require significant computing resources.

The detail of system 18b is not shown for clarity, but will be generally similar or the same as that of system 18a. That is, it will have a treatment planning apparatus and a radiotherapy apparatus comprising a source of radiation and some collimating device.

The method of operation of the system 10 and the management apparatus 12 will now be described with reference to Figure 2, which shows a flowchart according to embodiments of the present invention. In step 100, a database 15 is formed of treatment plans which have been found to deliver acceptable treatments, i.e. the levels of radiation dose generated with the treatment plans have been found to fall within the clinically acceptable limits. As explained above, each treatment plan comprises values for a number of parameters, including one or more of: rotation angle of the radiation head; positions of the MLC leaves (or other collimating elements); energy of the beam; overall amount of radiation dose being delivered (i.e. the number of monitor units); rate of delivery of that dose; position of the "wedge" (an absorptive collimating element used to reduce skin dose in some methods of treatment); the type of treatment being delivered (e.g. for treatment of breast cancer, prostate cancer, etc); the type of ionizing radiation used (e.g. electron therapy or x-ray therapy, etc); and the patient position.

The database 15 can thus be used to derive allowable ranges of values for each of the parameters of the treatment plan. An allowable range in some contexts may simply be the presence of values for a particular parameter. For example, if a treatment plan failed to include any MLC leaf positions, no collimation will take place and an excessive dose of radiation is likely to result. Thus an allowable range for MLC leaf positions may be simply the presence of values for the MLC leaf positions in the treatment plan. For other parameters, the allowable range may be a range of values. For example, an upper limit may be placed on the energy of the radiation beam. The allowable ranges may be derived relative to average values for the parameters in question. For example, each treatment plan in the database 15 will specify a radiation dose X for the treatment. If the average radiation dose across all treatment plans in the database is Y, the allowable range may be defined as Y - 50% < X < Y + 50%. Alternatively, absolute values may be used to define the allowable range relative to the average value.

A different set of allowable ranges of values may be derived for each type of treatment (e.g. which body part the therapy is planned for). For example, in the treatment of breast cancer, the vast majority of radiotherapy treatment plans will include placement of a "wedge" to reduce skin dose. If the treatment is specified as being for breast cancer, therefore, an allowable range may require the presence of values for the positioning of the wedge. For other types of treatment, the wedge may not be required and thus the allowable ranges may differ for different types of treatment.

The database 15 may be formed and updated over a period of time, in a manner to be explained below, or generated by an appropriately trained and qualified clinician. In step 102, the management apparatus 12 receives at its input 13 a proposed treatment plan from a radiotherapy system 18a, 18b. Thus, a patient has been admitted to hospital for radiotherapy. Various images of the treatment area have been acquired and a proposed treatment plan has been drawn up using the treatment planning apparatus 30. The treatment plan may be transmitted to the management apparatus at any point after it has been drawn up. However, in embodiments of the present invention, the treatment plan is transmitted to the management apparatus 12 as the plan is loaded into the radiotherapy apparatus for execution, i.e. in real time, just before the patient is to undergo therapy.

The proposed treatment plan comprises values for a plurality of parameters, and thus in step 104, the comparison logic 14 compares the values for each parameter to the corresponding allowable range derived in step 100.

Step 106 is a decision step of whether the parameters of the proposed treatment plan fall outside the allowable ranges. In an embodiment of the present invention, the decision step may result in a positive determination if just one of the parameters of the proposed treatment plan falls outside the corresponding allowable ranges. In other embodiments, the decision step may result in a positive determination if a subset of the parameters falls outside the allowable ranges.

If one or more of the proposed parameters falls outside its allowable range, the comparison logic generates an appropriate message and transmits it to the radiotherapy system 18a via the output 16. The message may be an alert for display to the user (i.e. a technician) of the radiotherapy apparatus (step 108), or an instruction to the radiotherapy apparatus itself to suspend operation (step 110), or both. In this way, either the technician is warned of a potentially harmful treatment plan, or the treatment is proactively stopped without technician input. Patient safety is enhanced in either case.

If the decision step 106 results in a negative determination (i.e. the parameters are all within the allowable ranges or a subset of the parameters are within the allowable ranges), the treatment is allowed to proceed (step 112). The comparison logic 14 generates an appropriate message, and transmits it to the radiotherapy system 18a via output 16.

According to embodiments of the present invention, once the proposed treatment plan has been deemed safe in this way, its parameters may be added to the database 15 such that the allowable ranges can be updated if necessary. In this way, the database 15 can constantly evolve as new treatments are deemed safe and as technology progresses.

In embodiments of the present invention, the management apparatus 12 continues to check the parameters of the radiotherapy treatment whilst therapy is ongoing. That is, during treatment, the radiotherapy apparatus 18a measures and transmits the current values of parameters to the management apparatus 12. The comparison logic 14 accesses the database 15 and compares the values for each parameter to the allowable range for that parameter (step 114).

The decision step 116 is therefore similar to the decision step 106 described above (but comparing measured values for the parameters, rather than the proposed values). In an embodiment of the present invention, therefore, the decision step may result in a positive determination if just one of the measured parameters falls outside its corresponding allowable range. In other embodiments, the decision step may result in a positive determination if a subset of the parameters falls outside the allowable ranges.

If the decision step 106 results in a negative determination (i.e. the parameters are all within the allowable ranges or a subset of the parameters are within the allowable ranges), the treatment is allowed to proceed and the process loops back to step 112.

The above description focuses on the aspects of the present invention as performed by the management apparatus 12. However, it will be apparent to those skilled in the art that corresponding novel and inventive aspects of the invention are performed at the "user" end of the radiotherapy system 10. Figure 3 is a flowchart of a method according to embodiments of the present invention as performed by a user of a radiotherapy apparatus (i.e. a technician). The method begins in step 200, where a proposed treatment plan is formed by treatment planning apparatus 30. As described above, this involves the steps of acquiring one or more images of the target region in the patient (i.e. the region incorporating the target for radiotherapy as well as surrounding tissue). The images are then analysed to identify a target region into which a minimum dose is to be delivered, any sensitive regions such as functional organs for which a maximum dose must be observed, and other non- target regions into which the dose is to be generally minimised. This three-dimensional map is then used to develop a treatment plan, i.e. a sequence of source movements, collimator movements, and dose rates which result in a three-dimensional dose distribution that (a) meets the requirements as to maximum and minimum doses (etc) and (b) is physically possible, e.g. does not require the source to rotate around the patient faster than it is physically capable.

In step 202, prior to treatment, the proposed treatment plan is sent to the management apparatus 12. This step may take place at any time after the proposed treatment plan is generated, but in one particular embodiment the proposed treatment plan is sent just prior to treatment, i.e. once loaded into the radiotherapy apparatus.

The management apparatus 12 compares the parameters of the treatment plan to the allowable ranges defined in its database 15, and transmits a message back to the radiotherapy system 18a. If one or more of the proposed parameters falls outside its allowable range, an alert message is received in step 204 and the further operation of the radiotherapy system may be suspended in step 206. Otherwise, the treatment is allowed to proceed (step 208). The radiotherapy system 18a may receive a message to this effect from the management apparatus 12.

In an embodiment of the present invention, the radiotherapy system 18a continues to monitor its machine parameters during treatment, and sends the measured values to the management apparatus 12 (step 210). As described above, the management apparatus compares the measured values to the allowable ranges stored in its database 15 and transmits an alert message if one or more of the parameters falls outside the allowable range. If an alert message is received in step 212, the further operation of the radiotherapy system 18a shall be suspended (step 206); otherwise, treatment is allowed to continue and the method loops back to step 208. The present invention thus provides methods and apparatus for safely managing the provision of radiotherapy treatment potentially in many different locations around the world. A database is formed comprising allowable ranges for each of a plurality of parameters in a radiotherapy treatment plan. Prior to treatment, the parameters of a proposed treatment plan are compared to these allowable ranges to see whether the treatment should be allowed to continue. If one or more of the proposed parameters falls outside the allowable ranges, the therapy session may be stopped or prevented altogether.

It will of course be understood that many variations may be made to the above- described embodiment without departing from the scope of the present invention.

Claims

A method of radiotherapy management, comprising:

forming a database of treatment plans, each treatment plan comprising a plurality of machine parameters, and deriving therefrom an allowable range for each of said machine parameters;

receiving a proposed treatment plan for execution on a radiotherapy apparatus, said proposed treatment plan comprising a plurality of proposed machine parameters;

comparing said plurality of proposed machine parameters to said allowable ranges for each of said machine parameters; and

if one or more of the proposed machine parameters falls outside said allowable ranges, transmitting an alert message to a user of the radiotherapy apparatus.

The method as claimed in claim 1, further comprising:

during ensuing treatment, receiving a plurality of actual machine parameters; comparing said plurality of actual machine parameters to said allowable ranges for each of said machine parameters; and

if one or more of the actual machine parameters falls outside said allowable ranges, transmitting an alert message to a user of the radiotherapy apparatus, or suspending operation of the radiotherapy apparatus.

A method of preparing for radiotherapy, comprising:

formulating a proposed treatment plan for execution on a radiotherapy apparatus for at least one session of radiotherapy, the treatment plan comprising a plurality of proposed machine parameters;

sending the proposed treatment plan to a management apparatus comprising a database of treatment plans, each treatment plan comprising a plurality of machine parameters, and allowable ranges for said plurality of machine parameters; and

receiving an alert message from said management apparatus if one or more of said proposed machine parameters falls outside said allowable ranges.

The method as claimed in claim 3, further comprising: during ensuing treatment, sending a plurality of actual machine parameters to said management apparatus; and

receiving an alert message from said management apparatus or suspending operation of the radiotherapy apparatus if one or more of said proposed machine parameters falls outside said allowable ranges.

The method according to any one of the preceding claims, wherein said plurality of machine parameters comprises one or more parameters selected from: an angle of rotation of a gantry of the radiotherapy apparatus, positions of leaves in a multi-leaf collimating apparatus, a position of a collimating wedge, an energy of the beam of radiation, the radiative dose to be delivered.

The method according to any one of the preceding claims, wherein a set of allowable ranges is provided for each of a plurality of different forms of radiotherapy.

The method according to any one of the preceding claims, wherein said allowable ranges comprise whether or not said machine parameters are present in said proposed treatment plan.

A radiotherapy treatment management apparatus, comprising:

a database comprising a plurality of treatment plans, each treatment plan comprising a plurality of machine parameters, and allowable ranges derived therefrom for said machine parameters;

an input, for receiving from a user of a radiotherapy apparatus a proposed treatment plan for execution on that radiotherapy apparatus, said proposed treatment plan comprising a plurality of proposed machine parameters;

comparison logic, for comparing said plurality of proposed machine parameters to said allowable ranges for each of said machine parameters; and an output, for transmitting an error message to the user of the radiotherapy apparatus if one or more of the proposed machine parameters falls outside said allowable ranges.