Patent Description:
A radiation therapy device typically includes, among other components, a platform (e.g., a table or couch) to support the patient and a nozzle that emits the radiation beam. The patient is positioned in a supine position, for example, and the nozzle directs the beam into the target (e.g., the tumor being treated).

During treatment, it is important to keep the patient as stationary (immobilized) as possible, so that the beam remains pointed at the target and at the proper place within the target. Otherwise, the radiation beam may miss parts of the target or might land on normal (healthy) tissue outside the target. Fixation or immobilization devices are used to secure a patient's position and keep the patient stationary during radiotherapy.

A standard treatment process includes scanning and imaging the patient prior to treatment to detect internal organs and accurately locate the target (e.g., the tumor). Immobilization devices customized for the patient are designed and a treatment plan is generated. The designs for the immobilization devices are sent to a manufacturer. The manufactured immobilization devices are delivered to the treatment center, where they are tested prior to beginning radiotherapy. If changes are needed, then the process of interacting with the manufacturer is repeated. The patient then returns and treatment can begin. An exemplary immobilization device for patient's head which comprises a plurality of material inserts having regular shape is described in publication <CIT>.

The conventional approach to providing the immobilization device described above is problematic for a variety of reasons. First, multiple patient visits are required - at least one visit is required prior to treatment in order to design the immobilization devices. Also, the need to involve a manufacturer increases costs. Furthermore, time may be lost while the immobilization devices are shipped from and perhaps back to the manufacturer.

Also during treatment, the beam nozzle and/or the patient are typically moved relative to one another so that the beam can be directed into the target from different directions/angles (beam geometries). The target may have an irregular shape and/or the amount (depth) of normal, healthy tissue on the beam path may vary depending on the beam geometry. In general, it may be necessary to shape the dose distribution delivered by a beam according to the shape and depth of the target and the beam geometry.

A range compensator is used to change (e.g., decrease) the energies of particles in a beam to affect the distance that the beam penetrate into the target. The range compensator may be located downstream of the particle accelerator before the nozzle or in the nozzle itself.

A recent radiobiology study has demonstrated the effectiveness of delivering an entire, relatively high therapeutic radiation dose to a target within a single, short period of time. This type of treatment is referred to generally herein as FLASH radiation therapy (FLASH RT). Evidence to date suggests that FLASH RT advantageously spares normal, healthy tissue from damage when that tissue is exposed to only a single irradiation for only a very short period of time. In general, because of the higher dose rates associated with FLASH RT, it is desirable to minimize the amount of time that normal, healthy tissue outside the target is irradiated. A means of achieving that is to produce a radiation treatment plan in which multiple beams do not overlap, or overlap as little as possible, outside the target. With FLASH RT, the direction/angle of the nozzle is set so that the nozzle is aimed at the target; the range compensator is adjusted to account for the beam energy, the distance to the target, and the shape of the target (the distance across the target); and then the beam is turned on and quickly turned off. The process is repeated for the next beam geometry. To reduce overall treatment time for the comfort of the patient, it is desirable to be able to quickly adjust the range compensator for the different beam geometries.

In one aspect the present invention provides an immobilization device for use in treating a patient during radiation therapy as defined in claim <NUM>. Optional features are defined in the claims dependent thereon. In another aspect the present invention provides a computer-implemented method of radiation treatment planning as defined in claim <NUM>. Optional features are defined in the claims dependent thereon. There is also described a computer-implemented radiation treatment method which does not form part of the invention.

Embodiments of the present invention describe systems for providing radiation therapy treatment using an immobilization device, e. g a cranial immobilization device. The immobilization device may cover a patient's head during radiation treatment and includes a material insert disposed within a shell of the immobilization device. The shell can be made of a high Z material to degrade the energy of a beam applied to the patient, and the range compensator fine tunes the depth and range of the beam so that the Bragg peak is located within a target of the patient. The range compensator is secured and supported by a scaffolding disposed in the shell so that the range compensator is located immediately before the patient.

According to one embodiment, an immobilization device for use in treating a patient during radiation therapy is disclosed. The device includes a shell, a plurality of different shaped and sized material inserts disposed in the shell, where each material insert of the plurality of material inserts respectively, and specifically shapes a distribution of a dose delivered to the patient by a respective beam of a plurality of beams emitted from a nozzle of a radiation treatment system in accordance with a treatment plan, and a scaffold component disposed in the shell operable to hold the plurality material inserts in place relative to the patient, wherein each material insert lies on a path of at least one of the plurality of beams. Each material insert has an irregular shape for shaping the respective beam to correspond to a shape or region of a target in the patient and a non-uniform thickness in accordance with a treatment plan.

According to another embodiment, a computer-implemented method of radiation treatment planning is disclosed. The method includes accessing, from a memory of a computer system, parameters for a radiation treatment plan, the parameters comprising a number of beams and beam paths relative to a position of a patient, and identifying locations on the patient for a plurality of material inserts disposed in an immobilization device (e.g. a cranial immobilization device), where each material insert of the plurality of material inserts lies on at least one of the beam paths and respectively shapes a distribution of a dose to be delivered to the patient by at least one of the beams in accordance with a treatment plan. Each material insert has an irregular shape for shaping the respective beam to correspond to a shape or region of a target in the patient and a non-uniform thickness in accordance with a treatment plan.

A computer-implemented radiation treatment method not forming part of the invention is also disclosed. The method includes accessing, from a memory of a computer system, a radiation treatment plan that prescribes a distribution of a dose to be delivered to a target in a patient by a plurality of beams emitted from a nozzle of a radiation treatment system, and controlling the nozzle to aim the plurality of beams at a plurality of material inserts positioned at different locations in an immobilization device (e.g. a cranial immobilization device), where each material insert of the plurality of material inserts is supported by a scaffold disposed in the immobilization device and respectively shapes a distribution of a respective dose delivered to the patient by a respective beam of the plurality of beams. The controlling includes aiming the nozzle at a first material insert of the plurality of material inserts and then turning on and emitting a first beam at the first material insert, and turning off the first beam and aiming the nozzle at a second material insert of the plurality of material inserts and turning on and emitting a second beam at the second material insert.

The accompanying drawings, which are incorporated in and form a part of this specification and in which like numerals depict like elements, illustrate embodiments of the present disclosure and, together with the detailed description, serve to explain the principles of the disclosure.

Reference will now be made in detail to the various embodiments of the present disclosure, examples of which are illustrated in the accompanying drawings. While described in conjunction with these embodiments, it will be understood that they are not intended to limit the disclosure to these embodiments. On the contrary, the disclosure is intended to cover alternatives, modifications and equivalents, which may be included within the scope of the disclosure as defined by the appended claims. Furthermore, in the following detailed description of the present disclosure, numerous specific details are set forth in order to provide a thorough understanding of the present disclosure. However, it will be understood that the present disclosure may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail so as not to unnecessarily obscure aspects of the present disclosure.

Some portions of the detailed descriptions that follow are presented in terms of procedures, logic blocks, processing, and other symbolic representations of operations on data bits within a computer memory. These descriptions and representations are the means used by those skilled in the data processing arts to most effectively convey the substance of their work to others skilled in the art. In the present application, a procedure, logic block, process, or the like, is conceived to be a self-consistent sequence of steps or instructions leading to a desired result. The steps are those utilizing physical manipulations of physical quantities. Usually, although not necessarily, these quantities take the form of electrical or magnetic signals capable of being stored, transferred, combined, compared, and otherwise manipulated in a computing system. It has proven convenient at times, principally for reasons of common usage, to refer to these signals as transactions, bits, values, elements, symbols, characters, samples, pixels, or the like.

Unless specifically stated otherwise as apparent from the following discussions, it is appreciated that throughout the present disclosure, discussions utilizing terms such as "accessing," "controlling," "identifying," "aiming," "turning on," "turning off," or the like, refer to actions and processes (e.g., the flowcharts of <FIG>, <FIG>, <FIG>, and <FIG>) of a computing system or similar electronic computing device or processor (e.g., the computing system <NUM> of <FIG>). The computing system or similar electronic computing device manipulates and transforms data represented as physical (electronic) quantities within the computing system memories, registers or other such information storage, transmission or display devices. Terms such as "dose" or "energy" generally refer to a dose or energy value; the use of such terms will be clear from the context of the surrounding discussion.

Portions of the detailed description that follows are presented and discussed in terms of a method. Although steps and sequencing thereof are disclosed in figures herein (e.g., <FIG>, <FIG>, <FIG>, and <FIG>) describing the operations of this method, such steps and sequencing are exemplary. Embodiments are well suited to performing various other steps or variations of the steps recited in the flowchart of the figure herein, and in a sequence other than that depicted and described herein.

Embodiments described herein may be discussed in the general context of computer-executable instructions residing on some form of computer-readable storage medium, such as program modules, executed by one or more computers or other devices. By way of example, and not limitation, computer-readable storage media may comprise non-transitory computer storage media and communication media. The functionality of the program modules may be combined or distributed as desired in various embodiments.

Computer storage media includes volatile and nonvolatile, removable and non-removable media implemented in any method or technology for storage of information such as computer-readable instructions, data structures, program modules or other data. Computer storage media includes, but is not limited to, random access memory (RAM), read only memory (ROM), electrically erasable programmable ROM (EEPROM), flash memory or other memory technology, compact disk ROM (CD-ROM), digital versatile disks (DVDs) or other optical storage, magnetic cassettes, magnetic tape, magnetic disk storage or other magnetic storage devices, or any other medium that can be used to store the desired information and that can accessed to retrieve that information.

Communication media can embody computer-executable instructions, data structures, and program modules, and includes any information delivery media. By way of example, and not limitation, communication media includes wired media such as a wired network or direct-wired connection, and wireless media such as acoustic, radio frequency (RF), infrared and other wireless media. Combinations of any of the above can also be included within the scope of computer-readable media.

<FIG> shows a block diagram of an example of a computing system <NUM> upon which the embodiments described herein may be implemented. In a basic configuration, the system <NUM> includes at least one processing unit <NUM> and memory <NUM>. This most basic configuration is illustrated in <FIG> by dashed line <NUM>. The system <NUM> may also have additional features and/or functionality. For example, the system <NUM> may also include additional storage (removable and/or non-removable) including, but not limited to, magnetic or optical disks or tape. Such additional storage is illustrated in <FIG> by removable storage <NUM> and non-removable storage <NUM>. The system <NUM> may also contain communications connection(s) <NUM> that allow the device to communicate with other devices, e.g., in a networked environment using logical connections to one or more remote computers.

The system <NUM> also includes input device(s) <NUM> such as keyboard, mouse, pen, voice input device, touch input device, etc. Output device(s) <NUM> such as a display device, speakers, printer, etc., are also included.

In the example of <FIG>, the memory <NUM> includes computer-readable instructions, data structures, program modules, and the like. Depending on how it is to be used, the system <NUM> - by executing the appropriate instructions or the like - can be used to implement a planning system used to create immobilization devices using a three-dimensional (3D) printer, as a control system to implement a radiation treatment plan in a radiation treatment system, or to implement a system for radiation treatment planning. More generally, system <NUM> can be used to create immobilization devices in accordance with the present invention.

<FIG> is a block diagram showing selected components of a radiation treatment system <NUM> upon which embodiments according to the present invention can be implemented. In the example of <FIG>, the system <NUM> includes an accelerator and beam transport system <NUM> that generate and/or accelerate a beam <NUM>. Embodiments according to the invention can generate and deliver beams of various types including, for instance, proton beams, electron beams, neutron beams, photon beams, ion beams, or atomic nuclei beams (e.g., using elements such as carbon, helium, or lithium). The operations and parameters of the accelerator and beam transport system <NUM> are controlled so that the intensity, energy, size, and/or shape of the beam are dynamically modulated or controlled during treatment of a patient according to a radiation treatment plan.

A recent radiobiology study has demonstrated the effectiveness of delivering an entire, relatively high therapeutic radiation dose to a target within a single, short period of time. This type of treatment is referred to generally herein as FLASH radiation therapy (FLASH RT). Evidence to date suggests that FLASH RT advantageously spares normal, healthy tissue from damage when that tissue is exposed to only a single irradiation for only a very short period of time. For FLASH RT, the accelerator and beam transport system <NUM> can generate beams that can deliver at least four (<NUM>) grays (Gy) in less than one second, and may deliver as much as <NUM> Gy or <NUM> Gy or more in less than one second.

The nozzle <NUM> is used to aim the beam toward various locations (a target) within a patient supported on the patient support device <NUM> (e.g., a chair, couch, or table) in a treatment room. A target may be an organ, a portion of an organ (e.g., a volume or region within the organ), a tumor, diseased tissue, or a patient outline, for instance.

The nozzle <NUM> may be mounted on or may be a part of a gantry (<FIG>) that can be moved relative to the patient support device <NUM>, which may also be moveable. In embodiments, the accelerator and beam transport system <NUM> are also mounted on or are a part of the gantry; in another embodiment, the accelerator and beam transport system are separate from (but in communication with) the gantry.

The control system <NUM> of <FIG> receives and implements a prescribed treatment plan. In embodiments, the control system <NUM> includes a computing system having a processor, memory, an input device (e.g., a keyboard), and perhaps a display; the system <NUM> of <FIG> is an example of such a platform for the control system <NUM>. The control system <NUM> can receive data regarding the operation of the system <NUM>. The control system <NUM> can control parameters of the accelerator and beam transport system <NUM>, nozzle <NUM>, and/or patient support device <NUM>, including parameters such as the energy, intensity, size, and/or shape of the beam, direction of the nozzle, and position of the patient support device (and the patient) relative to the nozzle, according to data the control system <NUM> receives and according to the radiation treatment plan.

<FIG> illustrates elements of a radiation treatment system <NUM> for treating a patient <NUM>. The system <NUM> is an example of an implementation of the radiation treatment system <NUM> of <FIG>, for example. In embodiments, the gantry <NUM> and nozzle <NUM> can be moved up and down the length of the patient <NUM> and/or around the patient, and the gantry and nozzle can move independently of one another. In embodiments, the patient support device <NUM> can be moved to different positions relative to the gantry <NUM> and nozzle <NUM>, rotated about its longitudinal axis, rotated about a central (normal) axis, and/or tilted back and forth about a transverse axis. While the patient <NUM> is supine in the example of <FIG>, the invention is not so limited. For example, the patient <NUM> can instead be seated in a chair.

In embodiments according to the invention, an immobilization device <NUM> can be placed next to and against the patient <NUM> on the patient support device <NUM> during radiation therapy. The placement of the immobilization device <NUM> and the shape and relative size of the device shown in the example of <FIG> are examples only. In embodiments, the immobilization device <NUM> is worn by the patient <NUM>. The immobilization device <NUM> can be custom-designed to fit the contours of the body of the patient <NUM>. In general, the immobilization device <NUM> is a patient-specific device. That is, the immobilization device <NUM> is designed for and used by a single patient.

The immobilization device <NUM> helps to establish a fixed, defined location for the patient <NUM> on the patient support device <NUM> and also helps to establish a position (e.g., posture) for the patient. An immobilization device also helps to maintain the patient in the established location and position during the course of a radiation treatment session and to re-establish and maintain the patient's location and position in subsequent treatment sessions. In embodiments according to the invention, the immobilization device <NUM> has a shape that provides these functionalities. Such shapes are known in the art.

Conventionally, an immobilization device is placed so that it does not obstruct the path of the beam. In contrast, in embodiments according to the invention, the immobilization device <NUM> is placed in the beam path, between the nozzle <NUM> and a target in the patient <NUM>, so that the beam passes through the immobilization device on its way to the target.

Thus, in embodiments, another purpose of the immobilization device <NUM> is to ensure that any path of a radiation beam from the nozzle <NUM> to a target inside the patient <NUM> will travel through substantially the same effective thickness of matter. That is, depending on the shape of the patient's body, the location of the target in the patient, and the shape of the target, a beam may pass through different amounts (depths) of tissue if those variables are not compensated for. Similarly, two or more beams that have parallel paths may each pass through different amounts of tissue. The shape of the immobilization device <NUM> can be designed to compensate for these types of differences. Thus, for beams such as proton beams, electron beams, neutron beams, photon beams, ion beams, and atomic nuclei beams, a uniform (or nearly uniform) dose can be delivered across the length (depth) of the target using a beam or beams that pass through the immobilization device <NUM>.

Also, for proton beams and ion beams, the immobilization device <NUM> can be designed to locate the Bragg peak of the beam inside the target. Specifically, the Bragg peak can be located at the distal portion or edge of the target, and then moved along the beam path toward the proximal edge of the target by changing the beam energy to achieve a Spread Out Bragg Peak (SOBP). Also, as will be described (see <FIG>), the shape of the immobilization device <NUM> can be designed to achieve an SOBP.

The immobilization device <NUM> of <FIG> can be advantageously utilized with FLASH RT, although the embodiments of the present invention are not so limited. In general, because of the higher dose rates associated with FLASH RT as mentioned above, it is desirable to minimize the amount of time that normal, healthy tissue outside the target is irradiated. A means of achieving that is to produce a radiation treatment plan in which beams do not overlap, or overlap as little as possible, outside the target. Another means of achieving that is to specify, during radiation treatment planning, limits for a maximum irradiation time and a minimum dose rate for normal, healthy tissue outside the target. However, it is still necessary to deliver the prescribed dose into and uniformly across the target. Immobilization devices in embodiments according to the present invention can provide a uniform dose into and across a target and thus can facilitate radiation treatment planning using FLASH RT by resolving or contributing to the resolution of that aspect of the planning.

As mentioned above, immobilization devices can be created by 3D-printing using a 3D printer. <FIG> is a block diagram illustrating components in a process <NUM> for creating immobilization devices in embodiments according to the present invention.

In the example of <FIG>, a patient (e.g., the patient <NUM>) is imaged using an image system <NUM> that uses, for example, x-rays, magnetic resonance imaging (MRI), and/or computed tomography (CT). When CT or MRI imagery, for example, is used, a series of two-dimensional (2D) images are taken from a 3D volume. Each 2D image is an image of a cross-sectional "slice" of the 3D volume. The resulting collection of 2D cross-sectional slices can be combined to create a 3D model or reconstruction of the patient's anatomy (e.g., internal organs). The 3D model will contain organs of interest, which may be referred to as structures of interest. Those organs of interest include the organ targeted for radiation therapy (a target), as well as other organs that may be at risk of radiation exposure during treatment.

One purpose of the 3D model is the preparation of a radiation treatment plan. To develop a patient-specific radiation treatment plan, information is extracted from the 3D model to determine parameters such as organ shape, organ volume, tumor shape, tumor location in the organ, and the position or orientation of several other structures of interest as they relate to the affected organ and any tumor. The radiation treatment plan can specify, for example, how many radiation beams to use and which angle each of the beams will be delivered from.

In embodiments according to the present invention, the images from the image system <NUM> are input to a planning system <NUM>. In embodiments, the planning system <NUM> includes a computing system having a processor, memory, an input device (e.g., a keyboard), and a display. The system <NUM> of <FIG> is an example of a platform for the planning system <NUM>.

Continuing with reference to <FIG>, the planning system <NUM> executes software that is capable of producing printing plans for an immobilization device or devices customized to the patient <NUM> and to the treatment plan devised for the patient. The software may itself translate the output of the image system <NUM> (e.g., the 3D model) into files that can be used by the 3D printer <NUM>. Alternatively, software may be used by a designer to produce such files based on the output of the image system <NUM> and also based on the treatment plan. The printing plans may be a design for an immobilization device, or it may be a design for a mold that can be used to fabricate the immobilization device. The planning system <NUM> outputs the files to the 3D printer <NUM>, which produces the immobilization device(s) and/or mold(s).

The immobilization device <NUM> can be produced by the 3D printer <NUM> using a range of different materials suitable for such a device; that is, using materials that have the necessary radiological properties. If the 3D printer <NUM> is not capable of using such materials, then it can instead produce a mold that can be used to produce an immobilization device made of suitable materials. The immobilization device <NUM> can be 3D-printed as a single piece, or it can be 3D-printed as multiple pieces that are subsequently assembled.

The immobilization device <NUM> so produced can be inspected and tested as part of a quality assurance plan before the device is used with a patient. If the immobilization device <NUM> is deficient in some aspect, the printing plans can be adjusted to correct the deficiency before the immobilization device is used.

Some or all of the process <NUM> can be implemented on-site (e.g., at the treatment center). Accordingly, patient-specific devices can be readily, quickly, inexpensively, effectively produced on-site without an external manufacturer, and avoiding shipping from and perhaps back to the manufacturer. The number of patient visits can be reduced because, for example, the immobilization device can be fabricated when the patient arrives for a treatment and/or because the immobilization device can be quickly modified on-site after testing for fit and/or function or while the radiation therapy is being performed. Furthermore, the immobilization devices can be recycled and do not need to be stored.

<FIG> illustrates an immobilization device <NUM> that can be 3D-printed in embodiments according to the present invention. The immobilization device <NUM> is an example of the immobilization device <NUM> of <FIG>. The immobilization device <NUM> includes a range compensator <NUM> and a positioning component <NUM>. The immobilization device <NUM> in general, and the range compensator <NUM> and positioning component <NUM> in particular, can be made of any suitable material or combination of materials including metal or plastic.

As discussed above, the immobilization device <NUM> is a patient-specific device designed or configured to hold a patient in place. The immobilization device <NUM> can also be designed or configured to compensate for differences in the amount of tissue that different beams may travel through, to provide a uniform dose across a target in the patient. In addition, in embodiments, the immobilization device <NUM> (specifically, the range compensator <NUM>) is designed or configured to shape the distribution of the dose delivered to a patient. In embodiments, the treatment beam is a proton beam or an ion beam and the range compensator <NUM> is configured to locate the Bragg peak of the beam inside the target in the patient. In one such embodiment, the range compensator <NUM> is configured to locate the Bragg peak at the distal portion or edge of the target.

The shape of the range compensator <NUM> can be designed so that the Bragg peak of a proton beam or an ion beam can be moved within the target by directing the beam through different parts of the range compensator. For example, as shown in the example of <FIG>, the range compensator <NUM> has a non-uniform surface facing the incoming beam. Thus, the thickness of the range compensator <NUM> (where thickness is measured in the direction of the beam path) is not uniform. Consequently, by aiming the beam at one part of the range compensator <NUM>, then another, and so on, the location of the Bragg peak in the target can be moved along the beam path between the distal and proximal portions of the target to create an SOBP. That is, different thicknesses of material can be placed in the path of the beam by aiming the beam at different parts of the range compensator <NUM>, thus affecting the energies of the particles in the beam, thereby affecting the distance the particles penetrate into the target and moving the location of the Bragg peak in the target to create an SOBP. An SOBP can also be achieved by varying the energy of the incident beam using the accelerator and beam transport system <NUM> (<FIG>).

Continuing with reference to <FIG>, the positioning component <NUM> holds the immobilization device <NUM> in place relative to the patient. That is, the positioning component <NUM> holds the immobilization device <NUM> on the patient in a manner such that, if the patient moves, then the immobilization device also moves so that it is in the same location on the patient.

In embodiments, the positioning component <NUM> fastens the immobilization device <NUM> to the patient. For example, as shown in <FIG>, the positioning component <NUM> may consist of or include straps that can be extended around the patient (not shown) to hold the immobilization device <NUM> (specifically, the range compensator <NUM>) in place against the patient. The surface of the immobilization device <NUM> that faces the patient can be contoured to match the contours of the patient's body.

In another embodiment, with reference to <FIG>, the positioning component <NUM> attaches to an item <NUM> worn by the patient (not shown). For example, the patient may wear a garment that includes fasteners (e.g., snaps or VELCRO®) that mate with corresponding fasteners of the positioning component <NUM> to hold the immobilization device <NUM> (specifically, the range compensator <NUM>) in place.

In embodiments, with reference to <FIG>, the range compensator <NUM> and the positioning component <NUM> are fabricated as a single piece.

<FIG> is a flowchart <NUM> of an example of computer-implemented operations for producing an immobilization device for limiting movement of a patient on a patient support device during radiation therapy in embodiments according to the present invention. The flowchart <NUM> can be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., using the computing system <NUM> of <FIG>).

In block <NUM> of <FIG>, a printing plan for an immobilization device is accessed from a memory of the computing system. The immobilization device includes features such as those described above in conjunction with <FIG> and <FIG>. Additional information is provided with reference to <FIG>.

In block <NUM> of <FIG>, a 3D printer is controlled using the printing plan to fabricate the immobilization device. Additional information is provided with reference to <FIG>.

<FIG> is a flowchart <NUM> of an example of computer-implemented operations for performing radiation treatment not forming part of the present invention. The flowchart <NUM> can be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., using the computing system <NUM> of <FIG>).

In block <NUM> of <FIG>, a radiation treatment plan is accessed from a memory of the computing system. The radiation treatment plan prescribes the dose or dose distribution to be delivered to a target in a patient by an incident beam emitted from a nozzle of a radiation treatment system.

Dose threshold curves are used to specify limits for the radiation treatment plan. A dose threshold curve provides a normal (healthy) tissue sparing-dose as a function of dose rate or irradiation time. The dose threshold curves can be tissue-dependent. For instance, the dose threshold curve for the lungs may be different from that for the brain. The appropriate dose threshold curve(s) can be to establish dose limits for radiation treatment planning. For example, the appropriate (e.g., tissue-dependent) dose threshold curve can be used to determine beam directions (gantry angles).

Dose limits can include, but are not limited to: a limit on irradiation time for each sub-volume (voxel) in the target (e.g., for each voxel of target tissue, treatment time less than x1 seconds); a limit on irradiation time for each sub-volume (voxel) outside the target (e.g., for each voxel of normal tissue, treatment time less than x2 seconds; x1 and x2 may be the same or different); a limit on dose rate for each sub-volume (voxel) in the target (e.g., for each voxel of target tissue, dose rate greater than y1 Gy/sec); and a limit on dose rate for each sub-volume (voxel) outside the target (e.g., f or each voxel of normal tissue, dose rate greater than y2 Gy/sec; y1 and y2 may be the same or different). In general, the limits are intended to minimize the amount of time that normal tissue is irradiated.

In block <NUM>, the nozzle is controlled according to the treatment plan to aim the beam at an immobilization device like that of <FIG> and <FIG>.

In summary, embodiments according to the present invention provide an improved immobilization device that is multi-functional. In addition to immobilizing a patient, the device can be used to shape the dose distribution within a target in the patient. In embodiments, the immobilization device includes a range compensator. In effect, in embodiments, the range compensator is moved from the nozzle of a radiation treatment system to the immobilization device. The multi-functional aspect of the immobilization device can improve radiation treatments and reduce costs. The immobilization device can be 3D-printed, which provides a number of benefits as well as explained above.

<FIG> is a system <NUM> for treating a patient <NUM> during radiation therapy. The system <NUM> includes one or more range compensators (exemplified by the range compensator <NUM>) and one or more positioning components (exemplified by the positioning component <NUM>). In practice, each range compensator is located on the patient <NUM>. The positioning component <NUM> holds the range compensator <NUM> in place relative to the patient <NUM> such that the range compensator lies on a path of a beam emitted from a nozzle of a radiation treatment system during radiation therapy.

Each of the range compensators shapes a distribution of a dose delivered to the patient <NUM> by the beam. The dose distribution may be relatively uniform across the target, or it may be non-uniform (e.g., the distribution may include a Bragg peak). Each range compensator can produce a different dose distribution in the target. In effect, the range compensator that conventionally is in, for example, the nozzle of a radiation treatment system is moved to locations on the patient <NUM>. The range compensators described in conjunction with <FIG>, <FIG> are examples of the range compensator <NUM>. One or more of the range compensators and one or more of the positioning components can be parts of an immobilization device as previously described herein. The range compensators and positioning components can be 3D-printed as previously described herein.

In embodiments, all of the range compensators are held in place on the patient <NUM> with a single positioning component. For example, the positioning component may be a belt worn by the patient <NUM>, and each of the range compensators could be fastened to the belt. In another embodiment, the range compensators are held in place individually by a respective positioning component as described in conjunction with <FIG>, <FIG>.

In operation, the nozzle is aimed at a first one of the range compensators and the beam is turned on, delivering a distributed dose to the target along the beam path. That is, the path of the beam passes through the first range compensator, which affects the beam to produce a particular dose distribution in the target according to the design of the first range compensator. The first range compensator may have a non-uniform surface facing the beam as described above. In that case, the beam can be scanned across the surface of the range compensator to change the shape of the dose distribution within the target. The nozzle can be aimed at the first range compensator by moving the nozzle or by moving the patient <NUM> or by doing both (the patient is moved by moving the patient support device <NUM> of <FIG>). After the beam is turned on for the time period specified by the radiation treatment plan (see, for example, the discussion of <FIG>), the beam is turned off. The nozzle is then aimed at a second one of the range compensators (by moving the patient or the nozzle or both) and the beam is turned on again. Thus, the path of the beam now passes through the second range compensator, which affects the beam to produce a particular dose distribution in the target according to the design of the second range compensator. Like the first range compensator, the second range compensator can have a non-uniform surface facing the incoming beam and the beam can be scanned across the surface of the second range compensator. The energy or intensity of the beam transmitted through the second range compensator can be different from that transmitted through the first range compensator. The beam is turned off again after the time period specified by the radiation treatment plan. This process can be repeated for each of the range compensators. In this manner, different beam geometries are readily accommodated.

<FIG> is a perspective view of an example of a beam geometry. In the example of <FIG>, the beams (exemplified by beam <NUM>) are in the same plane. The beams originate from a nozzle (not shown). Each beam can deliver a relatively high dose in a relatively short period of time. For example, each beam can deliver at least <NUM> Gy in less than one second, and may deliver as much as <NUM> Gy or <NUM> Gy or more in less than one second. In this example, the beams' paths overlap only within the target <NUM>, and do not overlap outside the target in the surrounding tissue.

<FIG> shows the range compensator <NUM> in the path of the beam <NUM>. The shape of the beam <NUM> and the shape of the range compensator <NUM> shown in the figure are for illustration purposes only. In general, the range compensator <NUM> is located on the outside of the patient (referred to as the patient outline), either on the patient's skin or on an article of clothing or the like worn by the patient. The beam <NUM> is aimed so that it passes through the range compensator <NUM>. The other beams shown in the figure can pass through other range compensators (not shown).

Although all beams are shown in <FIG>, this does not mean that all beams are necessarily delivered at the same time or in overlapping time periods, although they can be. The number of beams delivered at any one time depends on the number of gantries or nozzles in the radiation treatment system and on the treatment plan.

<FIG> illustrates a perspective view of an example of a beam geometry. In the example of <FIG>, the beams (exemplified by beam <NUM>) are in different planes. In this example, the beams' paths overlap only within the target <NUM>, and do not overlap outside the target in the surrounding tissue. Although all beams are shown in the figure, all beams are not necessarily delivered at the same time or in overlapping time periods as mentioned above.

<FIG> shows the range compensator <NUM> in the path of the beam <NUM>. The shape of the beam <NUM> and the shape of the range compensator <NUM> shown in the figure are for illustration purposes only. In general, the range compensator <NUM> is located on the outside of the patient (the patient outline) as described above. The beam <NUM> is aimed so that it passes through the range compensator <NUM>. The other beams shown in the figure can pass through other range compensators (not shown).

Thus, range compensators are placed at locations on the patient <NUM> such that each of the beams shown in <FIG> and <FIG> passes through a respective range compensator. In general, the surface of a patient can be viewed as having a number of discrete facets through which a beam may pass. From this perspective, for beams other than photon beams, each incident beam is orthogonal to a facet. A range compensator can be located on each facet.

<FIG> is a flowchart <NUM> of an example of computer-implemented operations for radiation treatment planning in embodiments according to the present invention. The flowchart <NUM> can be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., using the computing system <NUM> of <FIG>).

In block <NUM> of <FIG>, parameters for a radiation treatment plan are accessed from memory of the computing system. The parameters include, for example, the number of beams and paths of the beams relative to a position of a patient on a patient support device.

In block <NUM>, locations on the patient for range compensators are identified. Each range compensator is strategically located on the patient so that each range compensator lies on at least one of the beam paths. Each range compensator shapes a distribution of a dose to be delivered to the patient by at least one of the beams.

<FIG> is a flowchart <NUM> of an example of computer-implemented operations for radiation treatment not forming part of the present invention. The flowchart <NUM> can be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., using the computing system <NUM> of <FIG> to implement the control system <NUM> of <FIG>).

In block <NUM> of <FIG>, a radiation treatment plan is accessed from memory of the computing system. The radiation treatment plan prescribes a distribution of a dose to be delivered to a target in a patient by a number of beams emitted from a nozzle of a radiation treatment system.

In block <NUM>, the nozzle is controlled to aim the beams at range compensators positioned at different locations on the patient. Each range compensator shapes a distribution of a dose delivered to the patient by a respective beam. The nozzle is aimed at a first range compensator, and then a first beam is turned on and emitted at the first range compensator. The first beam is then turned off, the nozzle is aimed at a second range compensator, and a second beam is turned on and emitted at the second range compensator. This process can be repeated for each of the number of beams.

Proton radiotherapy takes advantage of the physics of how protons deposit their energy to target tumors with high precision. As opposed to photons, which deposit their energy almost uniformly with depth, protons deposit most of the dose at the end of their path forming the so-called Bragg Peak. The depth of the Bragg Peak is proportional to the energy of the proton beam, the higher the energy, the deeper in tissue. This characteristic offers a huge dosimetric advantage in radiotherapy allowing dose deposition primarily in the tumor while preserving critical organs at risk distal to the beam. Since depth is proportional to energy, it is possible to vary the energy and determine which is required to place the Bragg Peak in the tumor.

Currently two types of accelerators are in clinical practice, cyclotrons and synchrotrons. Energy modulation is achieved directly in synchrotrons whereas cyclotrons require a separate energy selection mechanism in which material (or degrader) is placed into the proton beam path thereby reducing the beam energy to the desired range. This process also introduces lateral scatter thereby causing significant beam divergence. If the patient is far from the degrader, beam shaping elements are required to maintain beam sizes suitable for pencil beam treatment. Some beam shaping elements, such as collimators, remove particles resulting in reduced proton current thereby precluding ultra-high dose rate FLASH therapy. Therefore, ultra-high dose rate Bragg peak targeting benefits from beam degradation as close to the patient as possible where proton loss is minimized.

<FIG> is a diagram of a top-view of an exemplary immobilization device <NUM> for providing cranial radiation therapy including layers of materials for degrading the energy of a field or beam depicted according to embodiments of the present invention. Removable material insert <NUM> can be a range compensator, range modulator, or a collimator to provide patient and beam specific depth and range modulation to shape the dose delivered to a specific target. As describe below, the scaffold <NUM> accommodates material inserts. <FIG> shows a side-view of the exemplary cranial immobilization device <NUM>. The shell <NUM> and material insert <NUM> of the immobilization device <NUM>, as shown in <FIG> and <FIG>, can provide a uniform dose into and across a target and thus can facilitate radiation treatment planning using FLASH RT by resolving or contributing to the resolution of that aspect of the planning. Although, in the embodiment, a cranial immobilization device <NUM> for use in cranial radiation therapy is described, it should be understood that the invention is applicable to immobilization devices for various patient body parts other than the cranium or head - such as parts of the patient torso - for use in other types of radiation therapy.

The specific number, shape, size, and type of material of the material inserts (e.g., material insert <NUM>) can be determined according to a treatment plan, and the treatment plan can be generated using an image system as described above with respect of <FIG>, for example. Although the immobilization device <NUM> depicted in <FIG> and <FIG> is illustrated using a single material insert <NUM>, embodiments of the cranial immobilization device described herein can accommodate up to <NUM> material inserts simultaneously (see <FIG>). By using a number of different material inserts disposed in the immobilization device <NUM>, the target can be treated using a number of non-coplanar gantry angles and the Bragg peak can be located at different depths according to the gantry angle and the location of the target. For example, different materials with different densities can be utilized to control the depth of the Bragg peak according to a treatment plan.

A patient-specific scaffold or support material <NUM> is disposed between the outer layer or "shell" <NUM> and the head of the patient. The shell has a helmet shape and encloses the scaffold <NUM> and the material inserts <NUM>. To improve the comfort of the patient while wearing the cranial immobilization device <NUM>, the scaffold <NUM> includes openings located near the patient's nose to facilitate breathing during treatment while the cranial immobilization device is worn by the patient, and includes holes near the patient's eyes so that the patient's eyes are not contacted or covered by the scaffold <NUM>. Moreover, the scaffold <NUM> includes holes for accommodating and supporting the material inserts (e.g., material insert <NUM>) used to provide patient and beam specific depth and range modulation according to the treatment plan.

The cranial immobilization device <NUM> in general, including the shell <NUM> and the material insert <NUM>, can be made of any suitable material or combination of materials including metal or plastic. For example, the shell <NUM> can be made of a hard plastic, and the material insert <NUM> can be made of high atomic number (Z) materials, such as brass or boron. The shell <NUM> provides an initial layer of material for degrading the energy of field <NUM> applied to the patient for range compensation, and removable material insert <NUM> fine tunes the energy of field <NUM> to provide patient and beam specific depth and range modulation to shape the dose delivered to the target. Moreover, the shell <NUM> and/or the scaffold <NUM> advantageously limit the movement of the patent (e.g., the patient's head) during treatment. The shell <NUM> and/or the scaffold <NUM> may help to establish a fixed, defined location for the patient (or part of the patient, such as the head) on a patient support device (e.g. a patient support device like that shown at <NUM> in <FIG>) and also helps to establish a position (e.g., posture) for the patient. An immobilization device also may help to maintain the patient in the established location and position during the course of a radiation treatment session and to re-establish and maintain the patient's location and position in subsequent treatment sessions. In embodiments according to the invention, the shell <NUM> and/or the scaffold <NUM> may have a shape that provides these functionalities.

The scaffold <NUM> is made of a rigid material for supporting relatively heavy material inserts and can be made, for example, by a 3D printer or by any other suitable means. For example, the scaffold <NUM> can be made of a 3D printed mesh that can support and secure heavy material inserts made of brass or boron.

The material insert <NUM> can be made from different materials depending on the density required by the treatment plan. For example, the material inserts can be made of plastic, ridge filters, or a 3D printed material (filament), or acrylic. The material inserts can also be formed by pouring a fluid material into a support hole or mold and allowing the fluid material to solidify in the shape of the mold. In some cases, the density of air may be sufficient to fine tune the beam energy, and therefore a hole can be provided in the scaffold <NUM> without a corresponding insert, in some cases. The material insert <NUM> can be enclosed or surrounded with a high Z material (e.g., an aperture) to provide additional range modulation. Moreover, the material insert <NUM> can include a collimator to sharpen the lateral penumbra of the beam.

The scaffold <NUM> and the material insert <NUM> in accordance with embodiments of the present invention are customized for the patient according to the treatment plan. In general, the immobilization device <NUM> is customized according to a 3D model of a patient's head and accounts for the location and shape of the target, the shape and dimensions of the patient's head, and the distance each beam applied to target must travel to reach the target. The shape of the material insert <NUM> is an irregular/complex shape for shaping the beam to correspond to a shape or region of the target (e.g., an edge), and the material insert <NUM> has a non-uniform thickness according to the treatment plan. The scaffold <NUM> is fabricated or modified accordingly with holes for accommodating the shape of the material insert <NUM>. The scaffold <NUM> and the material insert <NUM> are fabricated for the patient according to the treatment plan. The shell <NUM> can be a modified as needed, or can be constructed generically in different sizes, such as a "large" size and a "small" size that will accommodate most patients.

<FIG> depicts an exemplary cranial immobilization device <NUM> for providing radiation therapy treatment using a plurality of beams depicted according to embodiments of the present invention. Beam fields <NUM>, <NUM>, and <NUM> are applied to a target located within the head of the patient (e.g., a brain tumor), and each beam field corresponds to a material insert (e.g., a range compensator, range modulator, or a collimator) disposed on/in the immobilization device <NUM>. Each material insert (not pictured) can be made of different materials having a broad range of densities. Advantageously, the radiation therapy treatment can apply the beam fields <NUM>, <NUM>, and <NUM> without requiring machine changes between treatments. And because the positioning of the patient and the immobilization device <NUM>, including the material inserts, can be performed pre-treatment, therefore the patient does not need to be repositioned during treatment, thereby increasing the efficiency of the treatment compared to existing techniques that re-position the patient multiple times during treatment. Moreover, by performing energy degradation immediately at the patient surface using the material inserts for each beam field <NUM>, <NUM>, and <NUM>, beam spreading is significantly reduced compared to existing treatment systems that degrade the beam energy immediately after the nozzle emitting the beam.

The immobilization device <NUM> of <FIG> can be advantageously utilized with FLASH RT, although embodiments of the present invention are not so limited. In general, because of the higher dose rates associated with FLASH RT as mentioned above, it is desirable to minimize the amount of time that normal, healthy tissue outside the target is irradiated. A means of achieving that is to produce a radiation treatment plan in which beams do not overlap, or overlap as little as possible, outside the target. Another means of achieving that is to specify, during radiation treatment planning, limits for a maximum irradiation time and a minimum dose rate for normal, healthy tissue outside the target. However, it is still necessary to deliver the prescribed dose into and uniformly across the target. Therefore, the shell and material inserts of the immobilization device <NUM> can perform energy modulation/compensation to provide a uniform dose into and across a target and thus can facilitate radiation treatment planning using FLASH RT by resolving or contributing to the resolution of that aspect of the planning. In this way, very high energy (e.g., <NUM> MeV) can be applied to the target and the immobilization device performs range modulation to stop the Bragg peak at the desired position.

<FIG> depicts an exemplary cranial immobilization device <NUM> for providing radiation therapy treatment to a patient using a variety of material inserts <NUM>, <NUM>, <NUM>, <NUM>, <NUM>, and <NUM> according to embodiments of the present invention. Each material insert has a specific size and shape and is made from different materials with different densities according to a treatment plan. The material inserts have an irregular shape to produce a beam shape corresponding to a region or edge of a target. When a beam is applied to the various material inserts at a specific gantry angle, the material inserts perform range compensation/modulation based on the size, shape, and density of the respective material insert. The scaffold <NUM> is customized to accommodate the material inserts so that the inserts are supported securely between the patient and the shell <NUM>. For example, the scaffold can be manufactured by a 3D printer to include support holes corresponding to the shape of each material insert, or a mesh can be manufactured and support holes corresponding to each material inserts are cut out or drilled out of the scaffold <NUM>.

Each material insert is irradiated by a beam at a corresponding beam angle defined in the treatment plan. The beams can deliver a relatively high dose in a relatively short period of time. For example, each beam can deliver at least <NUM> Gy in less than one second, and may deliver as much as <NUM> Gy or <NUM> Gy or more in less than one second.

<FIG> depicts a patient-specific scaffold <NUM> according to embodiments of the present invention. The scaffold <NUM> is disposed between a hollow helmet shaped shell and the head of the patient and includes holes <NUM> located in front of the patient's eyes and holes <NUM> located near the patient's nose. The holes <NUM> and <NUM> improve the comfort of the patient while wearing a cranial immobilization device. Moreover, the scaffold <NUM> includes support holes <NUM> and <NUM> for accommodating material inserts used to provide patient and beam specific depth and range modulation according to the treatment plan. The scaffold <NUM> is made of a rigid material for supporting relatively heavy material inserts and can be made by a 3D printer. For example, the scaffold <NUM> can be made of a 3D printed mesh that can support and secure heavy material inserts made of brass or boron.

<FIG> is a flowchart <NUM> of an example of computer-implemented operations for producing an immobilization device (e.g., a cranial immobilization device) according to embodiments of the present invention. The flowchart <NUM> can be implemented as computer-executable instructions residing on some form of computer-readable storage medium (e.g., using the computing system <NUM> of <FIG>).

In block <NUM> of <FIG>, parameters for a radiation treatment plan are accessed from memory of the computing system. The parameters include, for example, the number of beams and paths of the beams relative to a position of a patient.

In block <NUM> of <FIG>, material inserts are fabricated that provide depth and range modulation for the immobilization device according to the treatment plan. The material inserts are supported by the scaffold fabricated in step <NUM> and can have a non-uniform shape in order to provide the desired range modulation and depth modulation of the treatment plan. Moreover, the material inserts can be made from high Z materials, such as brass and boron. The size, shape, and density of the material insert can be determined according to the radiation treatment plan which can include 3D imaging. The material insert can be a range compensator, range modulator, or a collimator. According to some embodiments, the material inserts are printed using a 3D printer according to a printing plan (e.g., the printing plan accessed in block <NUM>).

In block <NUM> of <FIG>, a printing plan for an immobilization device (e.g., a cranial immobilization device) is accessed from a memory of the computing system. The immobilization device includes features such as those described above in conjunction with <FIG>. Additional information is provided with reference to <FIG> and <FIG>.

In block <NUM> of <FIG>, a 3D printer is controlled using the printing plan to fabricate a scaffold to support and secure the material inserts. The scaffold can be made from a 3D printed mesh and can be fabricated with holes corresponding to the material inserts to support and secure the material inserts at a location close to the patient. In this way, the beam is degraded immediately at the patient surface to advantageously reduce lateral beam spreading.

In summary, range compensators in embodiments according to the invention can be used to shape dose distribution in the target in lieu of, but also in combination with, a conventional range compensator. By strategically locating different sized and shaped range compensators or material inserts on the patient, different beam geometries are readily accommodated. For radiation therapy including FLASH RT, it is not necessary to wait until a range compensator is adjusted when the beam geometry changes; instead, a properly configured range compensator is already in place in accordance with the treatment plan. Thus, radiation therapy including FLASH RT can be quickly performed, thereby facilitating patient comfort. Range compensators or material inserts as inserts into the scaffold in embodiments according to the present invention also can be used to provide the prescribed dose inside the target and thus can facilitate radiation treatment planning using FLASH RT by making it easier to address that aspect of the planning.

Claim 1:
An immobilization device for securing a patient's position for use in treating the patient during radiation therapy, the device comprising:
a shell component (<NUM>);
a plurality of material inserts (<NUM>) disposed in the shell component (<NUM>), wherein each material insert of the plurality of material inserts (<NUM>) is disposed in the shell component (<NUM>) to lie on a path of at least one of a plurality of beams emitted from a nozzle of a radiation treatment system and is configured to respectively shape a distribution of a dose delivered to the patient by a respective beam of the plurality of beams; and
a scaffold (<NUM>) component disposed in the shell component and operable to hold the plurality material inserts in place relative to the patient;
the immobilization device being characterized by each material insert having an irregular shape for shaping the respective beam to correspond to a shape or region of a target in the patient and a non-uniform thickness in accordance with a treatment plan.