Patent Description:
Radiation therapy is a localized treatment for a specific target tissue (a planning target volume), such as a cancerous tumor. Ideally, radiation therapy is performed on the planning target volume that spares the surrounding normal tissue from receiving doses above specified tolerances, thereby minimizing risk of damage to healthy tissue. Prior to the delivery of radiation therapy, an imaging system is typically employed to provide a three-dimensional image of the target tissue and surrounding area. From such imaging, the size and mass of the target tissue can be estimated and an appropriate treatment plan generated and planning target volume determined.

So that the prescribed dose is correctly supplied to the planning target volume (i.e., the target tissue) during radiation therapy, the patient should be correctly positioned relative to the linear accelerator that provides the radiation therapy. Typically, dosimetric and geometric data are checked before and during the treatment, to ensure correct patient placement and that the administered radiotherapy treatment matches the previously planned treatment. This process is referred to as image guided radiation therapy (IGRT), and involves the use of an imaging system to view target tissues prior to or while radiation treatment is delivered to the planning target volume. IGRT incorporates imaging coordinates from the treatment plan to ensure the patient is properly aligned for treatment in the radiation therapy device. <CIT> describes a computer-implemented medical data processing method for determining a difference in position of an imaged anatomical body part of a patient, the method comprising executing, on at least one processor of at least one computer, steps of: acquiring, at the at least one processor, first patient image data describing a digital image of a first anatomical body part during a first phase of inspiration and the position of the first anatomical body part during the first phase of inspiration in a first reference system associated with the first image data; acquiring, at the at least one processor, second patient image data different from the first patient image data and describing a digital image of the first anatomical body part during a second phase of inspiration and the position of the first anatomical body part during the second phase of inspiration in a second reference system associated with the second image data; acquiring, at the at least one processor, position transformation data describing a transformation between the first reference system and the second reference system; and determining, by the at least one processor and based on the first patient image data and the second patient image data and the position transformation data, position difference data describing a relative position between the position of the first anatomical body part during the first phase of inspiration and the position of the first anatomical body part during the second phase of inspiration.

According to the invention, there is provided a system for performing a treatment fraction of radiation therapy in accordance with claim <NUM>.

Optional features are defined in the dependent claims.

In accordance with at least some embodiments of the present disclosure and not being part of the claimed subject-matter, a method of breath-hold-based radiation therapy is disclosed in which a modified treatment fraction is generated and implemented when a patient is unable to maintain a threshold inspiration level on which a treatment plan is based. Specifically, prior to performing each treatment fraction of a treatment plan, the breathing capabilities of the patient are determined. When the patient is unable to maintain a breath-hold level that is equal to or greater than the threshold inspiration level, patient anatomy is imaged at an achievable inspiration level and a modified treatment fraction is generated based on the original treatment plan and the images of the patient anatomy at the achievable inspiration level. The modified treatment fraction is then performed while the patient maintains a breath-hold level that is equal to or greater than the achievable inspiration level. Thus, each treatment fraction can be adapted to the breathing capabilities of the patient at the time the treatment fraction is performed. As a result, even patients who cannot maintain the threshold inspiration level on which a treatment plan is based can benefit from deep-inspiration breath-hold treatments.

The foregoing and other features of the present disclosure will become more fully apparent from the following description and appended claims, taken in conjunction with the accompanying drawings. These drawings depict only several embodiments in accordance with the disclosure and are, therefore, not to be considered limiting of its scope. The disclosure will be described with additional specificity and detail through use of the accompanying drawings.

In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, similar symbols typically identify similar components, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from scope of the subject matter presented here. It will be readily understood that the aspects of the disclosure, as generally described herein, and illustrated in the figures, can be arranged, substituted, combined, and designed in a wide variety of different configurations, all of which are explicitly contemplated and make part of this disclosure.

Image guided radiation therapy (IGRT) is used to treat tumors in areas of the body that are subject to voluntary movement, such as the lungs, or involuntary movement, such as organs affected by peristalsis, gas motion, muscle contraction and the like. IGRT involves the use of an imaging system to view target tissues (also referred to as the "target volume") prior to or while radiation treatment is delivered thereto. In IGRT, image-based coordinates of the target volume from a previously determined treatment plan are compared to image-based coordinates of the target volume determined during the application of the treatment beam. In this way, changes in the surrounding organs at risk and/or motion or deformation of the target volume relative to the radiation therapy system can be detected. Consequently, dose limits to organs at risk are accurately enforced based on the daily position and shape, and the patient's position and/or the treatment beam can be adjusted to more precisely target the radiation dose to the tumor. For example, in pancreatic tumor treatments, organs at risk include the duodenum and stomach. The shape and relative position of these organs at risk with respect to the target volume can vary significantly from day-to-day. Thus, accurate adaption to the shape and relative position of such organs at risk enables escalation of the dose to the target volume and better therapeutic results.

In some radiation therapy systems, breath-hold-based radiation therapy is performed, such as deep-inspiration breath hold (DIBH) treatment, in which the patient performs one or more breath holds throughout a particular treatment fraction. DIBH treatment is often employed to separate an organ at risk or other critical anatomical structures from the target volume during the treatment fraction. In addition, DIBH treatment can reduce the motion and/or deformation of a target volume caused by patient respiration, thereby reducing the dose received by non-target tissue.

One drawback to DIBH treatment is that the patient cannot receive a treatment fraction unless able to perform a breath-hold at the same inspiration level that was achieved during the initial acquisition of the planning computed tomography scan. If the patient is unable to perform such a breath-hold at the time of treatment, a free-breathing plan is delivered instead. Generally, a free-breathing plan delivers more dose to the organs at risk (such as the heart in the case of breast cancer radiation therapy) and can have increased short- and long-term treatment side effects for the patient.

According to various embodiments, a modified treatment fraction is generated and implemented when a patient is unable to maintain a threshold inspiration level on which a treatment plan for that patient is based. In some embodiments, the ability for the patient to maintain a particular inspiration level is based on a breathing signal that indicates a current inspiration level of the patient. In such embodiments, the breathing signal can be measured using a fiducial, a marker block or other internal or external marker, and/or a surface recognition system that detects motion of a surface of the patient's body. In some embodiments, the breathing signal of a patient can be represented as a breath-hold curve that indicates the patient inspiration level over time. Embodiments of different breath-hold curves are described below in conjunction with <FIG> and <FIG>.

<FIG> is an illustration of a breath-hold curve <NUM> associated with a treatment planning process, according to various embodiments. Breath-hold curve <NUM> shows variations in a motion signal <NUM> over a time interval <NUM> that includes a patient breath hold. In the embodiment illustrated in <FIG>, time interval <NUM> is associated with a patient breath hold performed during a planning CT scan of patient anatomy and/or during a training session prior to the planning CT scan. Generally, the planning CT scan of the patient involves the acquisition of a set of projection images of the patient anatomy that includes a target volume, such as a tumor. To facilitate DIBH treatment, the patient typically performs a maximum or near-maximum inspiration of breath during the planning CT scan, so that the target volume is separated from organs at risk or other critical anatomical structures during subsequent treatment fractions. Thus, motion signal <NUM> is associated with a maximum or near-maximum inspiration of breath by the patient during time interval <NUM>.

In some embodiments, the specific value of motion signal <NUM> that is associated with breath-hold curve <NUM> is determined based at least in part on a motion trace of a point or points on the surface of the body of the patient and/or one or more internal or external markers (e.g., fiducials, surface markers, and the like). For example, in some embodiments, the measurement of motion signal <NUM> is performed via patient-monitoring optical sensors associated with the system performing the planning CT scan and one or more fiducials, other markers, position sensors, and/or detected locations on the surface of the body of the patient. Generally, the location of the fiducials, markers, position sensors, and/or detected locations on the surface of the body are selected so that said fiducials, markers, position sensors, and/or detected locations move synchronously, or substantially synchronously, with the target volume of the patient. Thus, in such embodiments, motion associated with the respiration cycle of the patient is accurately measured over time interval <NUM>. Such motion may be measured relative to any suitable datum location within or proximate to the anatomy of the patient.

In some embodiments, the value of motion signal <NUM> at each point in time in breath-hold curve <NUM> is based on the detected motion of a single internal or external marker, fiducial, or point on the surface of the body of the patient. In other embodiments, the value of motion signal <NUM> at each point in time in breath-hold curve <NUM> is based on the detected motion of multiple internal or external markers, fiducials, and/or points on the surface of the body of the patient. In such embodiments, the values of motion signal <NUM> may be based on an average of multiple motion values, where each motion value is associated with a different internal or external marker, fiducial, and/or point on the surface of the body of the patient. In such embodiments, the average of the multiple motion values can be a weighted average or a simple average.

In DIBH therapy, a predetermined threshold level <NUM> is determined for the patient, based on motion signal <NUM>. Predetermined threshold level <NUM> indicates a minimum allowable inspiration level to be maintained by the patient during the performance of a DIBH treatment fraction that separates an organ at risk or other critical anatomical structures from the target volume during the treatment fraction. In DIBH therapy, a treatment plan for the patient is generated in a planning treatment process that is based on the patient maintaining an inspiration level that is equal to or greater than predetermined threshold level <NUM> during a treatment fraction. Thus, when the patient cannot maintain an inspiration level equal to or greater than predetermined threshold level <NUM>, allowable movement of patient anatomy relative to the target volume may be exceeded, and the treatment plan cannot be safely performed without modification.

In the embodiment illustrated in <FIG>, predetermined threshold level <NUM> is expressed as an absolute displacement distance that is associated with breath-hold curve <NUM>, for example, <NUM> millimeters less than (and/or greater than) characteristic inspiration level <NUM>. In such embodiments, characteristic inspiration level <NUM> is also expressed as an absolute displacement distance associated with breath-hold curve <NUM>, for example, <NUM>. Alternatively, in some embodiments, predetermined threshold level <NUM> may be expressed as a percentage of a characteristic inspiration level <NUM> that is associated with breath-hold curve <NUM>, for example, <NUM>% of characteristic inspiration level <NUM>.

In some embodiments, characteristic inspiration level <NUM> is based on an average inspiration level achieved during a time interval <NUM> that is associated with motion signal <NUM>. In the embodiment illustrated in <FIG>, time interval <NUM> corresponds to a time during which the detected patient inspiration level remains substantially constant. In other embodiments, time interval <NUM> corresponds to most or all of time interval <NUM>, or some other time interval associated with breath-hold curve <NUM>, such as a final portion of time interval <NUM>, a middle portion of time interval <NUM>, etc. In some embodiments, characteristic inspiration level <NUM> is based on a lowest inspiration level <NUM> achieved during time interval <NUM>.

In some embodiments, in DIBH therapy, multiple predetermined threshold levels based on motion signal <NUM> are determined for the patient, such as a minimum threshold level and a maximum threshold level. In the embodiment illustrated in <FIG>, predetermined threshold level <NUM> is implemented as the minimum threshold level based on motion signal <NUM>, and predetermined threshold level <NUM> is implemented as the maximum threshold level based on motion signal <NUM>. In the embodiment, predetermined threshold level <NUM> is determined based on a percentage of characteristic inspiration level <NUM> that is associated with breath-hold curve <NUM>, for example, <NUM>% of characteristic inspiration level <NUM>, or <NUM>. In such embodiments, a treatment plan for the patient is generated in a planning treatment process that is based on the patient maintaining an inspiration level that is equal to or greater than predetermined threshold level <NUM> and equal to or less than predetermined threshold level <NUM> during a treatment fraction.

<FIG> is an illustration of a breath-hold curve <NUM> associated with a treatment fraction of a treatment plan, according to various embodiments. Breath-hold curve <NUM> shows variations in a motion signal <NUM> over a time interval <NUM> that includes a patient breath hold. In the embodiment illustrated in <FIG>, time interval <NUM> is associated with a patient breath hold performed in preparation for a treatment fraction to be performed, such as during patient setup for a particular treatment fraction. As such, the patient breath hold associated with breath-hold curve <NUM> is performed immediately prior to treatment, for example after the patient has been positioned on a radiation therapy system couch for treatment and before the treatment fraction has begun to be performed.

Similar to motion signal <NUM> in <FIG>, motion signal <NUM> is determined based at least in part on a motion trace of a point or points on the surface of the body of the patient and/or one or more internal or external markers (e.g., fiducials, surface markers, and the like). For reference, predetermined threshold level <NUM> for the patient is also shown in <FIG>. According to various embodiments, based on motion signal <NUM>, a modified treatment fraction may be generated and implemented while the patient remains positioned on the radiation therapy system couch for treatment. Specifically, when motion signal <NUM> indicates that the patient cannot maintain a suitable inspiration level (for example, an inspiration level greater than or equal to predetermined threshold level <NUM>), a current fraction inspiration threshold <NUM> is determined based on motion signal <NUM>. For example, current fraction inspiration threshold <NUM> can be determined based on motion signal <NUM> and characteristic inspiration level <NUM> in the same way that predetermined threshold level <NUM> is based on motion signal <NUM>. The modified treatment fraction is then generated and implemented, as described below in conjunction with <FIG> and <FIG>.

<FIG> is a perspective view of a radiation therapy system <NUM> that can beneficially implement various aspects of the present disclosure. Radiation therapy (RT) system <NUM> is a radiation system configured to detect intra-fraction motion in near-real time using X-ray imaging techniques. Thus, RT system <NUM> is configured to provide stereotactic radiosurgery and precision radiotherapy for lesions, tumors, and conditions anywhere in the body where radiation treatment is indicated. As such, RT system <NUM> can include one or more of a linear accelerator (LINAC) that generates a megavolt (MV) treatment beam of high energy X-rays, a kilovolt (kV) X-ray source, one or more X-ray imagers, and, in some embodiments, an MV electronic portal imaging device (EPID). By way of example, RT system <NUM> is described herein configured with a circular gantry. In other embodiments, RT system <NUM> can be configured with a C-gantry capable of infinite rotation via a slip ring connection.

Generally, RT system <NUM> is capable of kV imaging of a target volume during application of an MV treatment beam, so that an IGRT and/or an intensity-modulated radiation therapy (IMRT) process can be performed using X-ray imaging. RT system <NUM> may include one or more touchscreens <NUM>, couch motion controls <NUM>, a bore <NUM>, a base positioning assembly <NUM>, a couch <NUM> disposed on base positioning assembly <NUM>, and an image acquisition and treatment control computer <NUM>, all of which are disposed within a treatment room. RT system <NUM> further includes a remote control console <NUM>, which is disposed outside the treatment room and enables treatment delivery and patient monitoring from a remote location. Exemplary embodiments of a computing device that can be implemented as image acquisition and treatment control computer <NUM> and/or remote control console <NUM> is described below in conjunction with <FIG>. Base positioning assembly <NUM> is configured to precisely position couch <NUM> with respect to bore <NUM>, and motion controls <NUM> include input devices, such as button and/or switches, that enable a user to operate base positioning assembly <NUM> to automatically and precisely position couch <NUM> to a predetermined location with respect to bore <NUM>. Motion controls <NUM> also enable a user to manually position couch <NUM> to a predetermined location.

In some embodiments, RT system <NUM> further includes one or more patient-monitoring optical sensors <NUM>. Patient-monitoring optical sensors <NUM> are configured as a patient position-monitoring system that generates an external motion signal indicating a specific magnitude of respiratory motion by a patient on couch <NUM>. Thus, patient-monitoring sensors <NUM> can obtain a motion trace of one or more points on a surface of the body of the patients, for example based on the motion of a fiducial or other internal or external marker (or markers) or location(s) on the surface of the patient that is/are positioned to move synchronously with a target volume of the patient. In some embodiments, patient-monitoring optical sensors <NUM> include one or more cameras, surface scanners, and/or the like.

<FIG> schematically illustrates a drive stand <NUM> and gantry <NUM> of RT system <NUM>, according to various embodiments. Covers, base positioning assembly <NUM>, couch <NUM>, and other components of RT system <NUM> are omitted in <FIG> for clarity. Drive stand <NUM> is a fixed support structure for components of RT treatment system <NUM>, including gantry <NUM> and a drive system <NUM> for rotatably moving gantry <NUM>. Drive stand <NUM> rests on and/or is fixed to a support surface that is external to RT treatment system <NUM>, such as a floor of an RT treatment facility. Gantry <NUM> is rotationally coupled to drive stand <NUM> and is a support structure on which various components of RT system <NUM> are mounted, including a linear accelerator (LINAC) <NUM>, an MV electronic portal imaging device (EPID) <NUM>, an imaging X-ray source <NUM>, and an X-ray imager <NUM>. During operation of RT treatment system <NUM>, gantry <NUM> rotates about bore <NUM> when actuated by drive system <NUM>.

Drive system <NUM> rotationally actuates gantry <NUM>. In some embodiments, drive system <NUM> includes a linear motor that can be fixed to drive stand <NUM> and interacts with a magnetic track (not shown) mounted on gantry <NUM>. In other embodiments, drive system <NUM> includes another suitable drive mechanism for precisely rotating gantry <NUM> about bore <NUM>. LINAC <NUM> generates an MV treatment beam <NUM> of high energy X-rays (or in some embodiments electrons, protons, and/or other heavy charged particles, ultra-high dose rate X-rays (e.g., for FLASH radiotherapy) or microbeams for microbeam radiation therapy) and EPID <NUM> is configured to acquire X-ray images with treatment beam <NUM>. Imaging X-ray source <NUM> is configured to direct a conical beam of X-rays, referred to herein as imaging X-rays <NUM>, through an isocenter <NUM> of RT system <NUM> to X-ray imager <NUM>, and isocenter <NUM> typically corresponds to the location of a target volume <NUM> to be treated. In the embodiment illustrated in <FIG>, X-ray imager <NUM> is depicted as a planar device, whereas in other embodiments, X-ray imager <NUM> can have a curved configuration.

X-ray imager <NUM> receives imaging X-rays <NUM> and generates suitable projection images therefrom. According to certain embodiments, such projection images can then be employed to construct or update portions of imaging data for a digital volume that corresponds to a three-dimensional (3D) region that includes target volume <NUM>. That is, a 3D image of such a 3D region is reconstructed from the projection images. In some embodiments, cone-beam computed tomography (CBCT) and/or digital tomosynthesis (DTS) can be used to process the projection images generated by X-ray imager <NUM>. CBCT is typically employed to acquire projection images over a relatively long acquisition arc, for example over a rotation of <NUM>° or more of gantry <NUM>. As a result, a high-quality 3D reconstruction of the imaged volume can be generated. CBCT is often employed at the beginning of a radiation therapy session to generate a set-up 3D reconstruction. For example, CBCT may be employed immediately prior to application of treatment beam <NUM> to generate a 3D reconstruction confirming that target volume <NUM> has not moved or changed shape. Alternatively or additionally, in some embodiments, partial-data reconstruction is performed by RT system <NUM> during portions of an IGRT or IMRT process in which partial image data is employed to generate a 3D reconstruction of target volume <NUM>. For example, as treatment beam <NUM> is directed to isocenter <NUM> while gantry <NUM> rotates through a treatment arc, DTS image acquisitions can be performed to generate image data for target volume <NUM>. Because DTS image acquisition is performed over a relatively short acquisition arc, for example between about <NUM>° and <NUM>°, near real-time feedback for the shape and position of target volume <NUM> can be provided by DTS imaging during the IGRT process.

In the embodiment illustrated in <FIG>, RT system <NUM> includes a single X-ray imager and a single corresponding imaging X-ray source. In other embodiments, RT system <NUM> can include two or more X-ray imagers, each with a corresponding imaging X-ray source. One such embodiment is illustrated in <FIG>.

<FIG> schematically illustrates a drive stand <NUM> and gantry <NUM> of RT system <NUM>, according to various embodiments. Drive stand <NUM> and gantry <NUM> are substantially similar in configuration to drive stand <NUM> and gantry <NUM> in <FIG>, except that the components of RT system <NUM> that are mounted on gantry <NUM> include a first imaging X-ray source <NUM>, a first X-ray imager <NUM>, a second imaging X-ray source <NUM>, and a second X-ray imager <NUM>. In such embodiments, the inclusion of multiple X-ray imagers in RT system <NUM> facilitates the generation of projection images (for reconstructing the target volume) over a shorter image acquisition arc. For instance, when RT system <NUM> includes two X-ray imagers and corresponding X-ray sources, an image acquisition arc for acquiring projection images of a certain image quality can be approximately half that for acquiring projection images of a similar image quality with a single X-ray imager and X-ray source.

The projection images generated by X-ray imager <NUM> (or by first x-ray imager <NUM> and second X-ray imager <NUM>) are used to construct imaging data for a digital volume of patient anatomy within a 3D region that includes the target volume. Alternatively or additionally, such projection images can be used to update portions of an existing imaging data for the digital volume corresponding to the 3D region. One embodiment of such a digital volume is described below in conjunction with <FIG>.

<FIG> schematically illustrates a digital volume <NUM> that is constructed based on projection images generated by one or more X-ray imagers included in RT system <NUM>, according to various embodiments. For example, in some embodiments, the projection images can be generated by a single X-ray imager, such as X-ray imager <NUM>, and in other embodiments the projection images can be generated by multiple X-ray imagers, such as first x-ray imager <NUM> and second X-ray imager <NUM>.

Digital volume <NUM> includes a plurality of voxels <NUM> (dashed lines) of anatomical image data, where each voxel <NUM> corresponds to a different location within digital volume <NUM>. For clarity, only a single voxel <NUM> is shown in <FIG>. Digital volume <NUM> corresponds to a 3D region that includes target volume <NUM>. In <FIG>, digital volume <NUM> is depicted as an 8x8x8 voxel cube, but in practice, digital volume <NUM> generally includes many more voxels, for example orders of magnitude more than are shown in <FIG>.

For purposes of discussion, target volume <NUM> can refer to the gross tumor volume (GTV), clinical target volume (CTV), or the planning target volume (PTV) for a particular treatment. The GTV depicts the position and extent of the gross tumor, for example what can be seen or imaged; the CTV includes the GTV and an additional margin for sub-clinical disease spread, which is generally not imagable; and the PTV is a geometric concept designed to ensure that a suitable radiotherapy dose is actually delivered to the CTV without adversely affecting nearby organs at risk. Thus, the PTV is generally larger than the CTV, but in some situations can also be reduced in some portions to provide a safety margin around an organ at risk. The PTV is typically determined based on imaging performed prior to the time of treatment, and alignment of the PTV with the current position of patient anatomy at the time of treatment is facilitated by X-ray imaging of digital volume <NUM>.

In some embodiments, image information associated with each voxel <NUM> of digital volume <NUM> is constructed via projection images generated by single or multiple X-ray imagers via a CBCT process. For example, such a CBCT process can be employed immediately prior to delivering treatment beam <NUM> to target volume <NUM>, so that the location and shape of target volume <NUM> can be confirmed before treatment begins. In addition, in some embodiments, image information associated with some or all of voxels <NUM> of digital volume <NUM> is updated via projection images generated by the single or multiple X-ray imagers. In this way, the location and shape of target volume <NUM> can be confirmed while the treatment is underway. Thus, if a sufficient portion of the target volume <NUM> is detected to be extending outside a threshold region, the treatment can either be aborted or modified.

According to various embodiments, a modified treatment fraction is generated and/or implemented when a patient is unable to maintain the threshold inspiration level on which a treatment plan for that patient is based. In some embodiments, the ability of the patient to maintain the threshold inspiration level is checked prior to beginning each treatment fraction of a treatment plan. In such embodiments, when the determination is made that the patient can maintain the threshold inspiration level, a normal treatment fraction is implemented, and when the determination is made that the patient cannot maintain the threshold inspiration level, a modified treatment fraction is generated and/or implemented. One such embodiment is described below in conjunction with <FIG>.

<FIG> sets forth a flowchart of a radiation therapy process <NUM>, according to one or more embodiments. Radiation therapy process <NUM> may include one or more operations, functions, or actions as illustrated by one or more of blocks <NUM> - <NUM>. Although the blocks are illustrated in a sequential order, these blocks may be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or eliminated based upon the desired implementation. Although radiation therapy process <NUM> is described in conjunction with the systems of <FIG>, persons skilled in the art will understand that any suitably configured radiation therapy system is within the scope of the present embodiments.

Certain blocks <NUM> - <NUM> can be performed by a single computing device or by multiple computing devices. For example, in some embodiments, blocks <NUM> - <NUM> are performed by one or more computing devices associated with a radiation therapy system, such as image acquisition and treatment control computer <NUM> and/or remote control console <NUM> of <FIG>. Further, in some embodiments certain blocks <NUM> - <NUM> can be performed by multiple systems. For example, in some embodiments, block <NUM> is performed by an imaging CT system, block <NUM> is performed by one or more treatment planning systems, and blocks <NUM> - <NUM> are performed a radiation therapy system.

In step <NUM>, a treatment planning CT scan is performed on a region of patient anatomy around a target volume (e.g., a tumor or other target tissue) and a 3D treatment planning CT image is generated. Generally, the treatment planning CT image is generated by scanning the patient (for example, acquiring a set of projection images of a target volume), such as during a clinical visit. The treatment planning CT image is a treatment planning digital volume that includes the target volume and is generated based on the projection images acquired in step <NUM>. The treatment planning CT scan is performed while the patient maintains an inspiration level that is equal to or greater than predetermined threshold level <NUM>. Any technically feasible CT scanning process can be employed to generate the treatment planning CT, such as spiral CT or CBCT.

In step <NUM>, a treatment plan is generated for the patient. Generally, the process of generating the treatment plan involves multiple treatment planning steps. For example, the process typically includes specifying target tissue structures and normal tissue structures in the treatment planning CT image, such as the GTV, the CTV, the internal target volume (ITV), the PTV, organs at risk (OAR), a planning organ at risk volume (PRV), and/or the like. In some embodiments, the process further includes steps such as target segmentation, OAR segmentation, plan optimization, and/or the like. Typically, the treatment plan is based on the treatment planning CT image that is generated in step <NUM>, and includes one or more beam geometries for implementing the planned treatment and an optimized dose distribution for each beam geometry.

In step <NUM>, implementation of a treatment fraction begins. Generally, a radiation therapy process includes multiple treatment fractions that are each performed by a radiation therapy system on a different clinical visit. For example, in some embodiments, each treatment fraction is performed on a different day. Thus, in the embodiment illustrated in <FIG>, multiple iterations of steps <NUM> - <NUM> are performed in the course of completing a planned radiation therapy process.

For a particular treatment fraction, in step <NUM> a patient is precisely positioned relative to the radiation therapy system at a treatment position. For example, in some embodiments, when the patient is disposed at the treatment position, an isocenter of the radiation therapy system coincides with the target volume associated with the patient, such as target volume <NUM>. In some embodiments, the patient is precisely positioned at the treatment position via a couch of the radiation therapy system, such as couch <NUM>, and/or via one or more patient-monitoring optical sensors, such as patient-monitoring optical sensors <NUM>. In some embodiments, the patient is positioned via external markings on the body of the patient. Alternatively or additionally, in some embodiments, the patient is positioned based on X-ray imaging performed in step <NUM>.

In step <NUM>, breathing cycle data is collected for the patient while the patient is disposed at the treatment position. For example, in some embodiments, the radiation therapy system performing the current treatment fraction receives a breathing signal that indicates an inspiration level of the patient. In some embodiments, a breath-hold curve is generated based on the breathing signal. In such embodiments, the breath-hold curve can indicate whether the inspiration level that the patient can maintain at the time of the current treatment fraction meets or exceeds the predetermined threshold inspiration level, such as predetermined threshold level <NUM>.

In step <NUM>, the radiation therapy system performing the current treatment fraction determines whether the patient can maintain an inspiration level that is equal to or greater than predetermined threshold level <NUM>. In some embodiments, the determination is made based on the breath-hold curve and/or other breathing cycle data collected in step <NUM>. For example, in some embodiments, breathing cycle data collected in step <NUM> is compared to predetermined threshold level <NUM>. When the patient can maintain such an inspiration level, radiation therapy process <NUM> proceeds to step <NUM>; when the patient cannot maintain such an inspiration level, radiation therapy process <NUM> proceeds to step <NUM>.

In step <NUM>, a normal treatment fraction from the treatment plan is performed. In some embodiments, performance of the normal treatment fraction includes applying beam parameters and dose distributions determined for the patient based on the treatment plan generated for the patient in step <NUM>. In some embodiments, performance of the normal fraction includes additional X-ray imaging of the patient while the patient is disposed at the treatment position and modification of one or more beam parameters and/or dose distributions based on the additional X-ray imaging. For example, changes in patient anatomy that have occurred since the treatment planning CT scan was performed in step <NUM> can be compensated for at this time. Alternatively, in some embodiments, performance of the normal fraction does not include additional X-ray imaging of the patient. In either case, in step <NUM>, the current treatment fraction is performed without modifications to the treatment plan that are based on a different inspiration level than maintained by the patient when the treatment planning CT scan was performed. After completion of the treatment fraction, radiation therapy process <NUM> proceeds to step <NUM>.

In some embodiments, the normal treatment fraction is performed over a single rotational arc of a gantry of the radiation therapy system. Alternatively, in some embodiments, the normal treatment fraction is performed over multiple rotational arcs of a gantry of a radiation therapy system. Alternatively, in some embodiments, the normal treatment fraction is performed over a fraction of a rotational arc of a gantry of a radiation therapy system or over multiple separate fractions of a rotational arc of the gantry. Alternatively, in some embodiments, the normal treatment fraction is performed in a static-gantry radiation therapy process, such as an IMRT or a 3D-conformal radiation therapy process.

In step <NUM>, the radiation system performing the current treatment fraction determines the current fraction inspiration threshold, such as current fraction inspiration threshold <NUM>, based on the breathing signal received in step <NUM>.

In step <NUM>, the radiation therapy system performing the current treatment fraction acquires projection images of the patient. For example, in some embodiments, the projection images are acquired via a CBCT scan of the patient. In step <NUM>, the projection images of the patient are acquired while the patient remains disposed in the treatment position set up in step <NUM>. Further, the projection images of the patient are acquired while the patient maintains the current fraction inspiration threshold determined in step <NUM>.

In step <NUM>, a synthetic CT image that includes the target volume is generated. The synthetic CT image is based on the treatment planning digital volume associated with the radiation therapy process, such as the treatment planning CT image generated in step <NUM>. The synthetic CT image is further based on the projection images of the patient acquired in step <NUM>. In some embodiments, the synthetic CT image is generated by deformably registering image data within the treatment planning digital volume onto corresponding image data associated with the set of projection images. For example, in some embodiments, a digital volume is generated based on the set of projection images of the patient acquired in step <NUM>, and this digital volume captures the current anatomy of the patient when maintaining the current fraction inspiration threshold. In such embodiments, image data within the treatment planning digital volume is deformably registered onto corresponding image data included in the digital volume that captures the current anatomy of the patient when maintaining an inspiration level that meets or exceeds the current fraction inspiration threshold. Thus, in such embodiments, in step <NUM> the synthetic CT image is generated by modifying the treatment planning digital volume based on the anatomy of the patient when maintaining an inspiration level that meets or exceeds the current fraction inspiration threshold but does not meet or exceed predetermined threshold level <NUM>.

In step <NUM>, a modified treatment fraction is generated based on the synthetic CT image generated in step <NUM> and the treatment plan generated in step <NUM>. For example, in some embodiments, generating the modified treatment fraction includes detecting anatomical structures within the synthetic CT image. In such embodiments, such anatomical structures include one or more of the GTV, the CTV, the ITV, the PTV, one or more organs at risk (OAR), a PRV, and/or the like. In some embodiments, a conventional autosegmentation process or autosegmentation software application is employed to detect one or more such anatomical structures. Alternatively or additionally, in some embodiments, an artificial intelligence algorithm is employed to detect one or more such anatomical structures.

In some embodiments, generating the modified treatment fraction includes determining one or more treatment beam parameters for the modified treatment fraction based on the anatomical structures detected within the treatment planning digital volume. Thus, in such embodiments, one or more treatment beam parameters associated with the treatment plan generated in step <NUM> are modified based on the current anatomy of the patient when maintaining the current fraction inspiration threshold.

In step <NUM>, the radiation therapy system performs the modified treatment fraction while the patient remains in the treatment position and maintains an inspiration level that meets or exceeds the current fraction inspiration threshold, such as current fraction inspiration threshold <NUM>. Similar to step <NUM>, in step <NUM>, the modified treatment fraction can be performed over a single rotational arc, multiple rotational arcs, a fraction of a rotational arc, multiple separate fractions of a rotational arc of a gantry of the radiation therapy system, or via multiple static IMRT fields.

In step <NUM>, the radiation therapy system performing the current treatment fraction determines whether any treatment fractions remain to be performed. If yes, radiation therapy process <NUM> returns to step <NUM>; if no, radiation therapy process <NUM> proceeds to step <NUM> and terminates.

According to various embodiments, a modified treatment fraction is generated and implemented for each treatment fraction of a treatment plan. In such embodiments, for each treatment fraction, a modified treatment fraction is generated based on the inspiration level that can be maintained by the patient on the day of the treatment fraction. One such embodiment is described below in conjunction with <FIG>.

As shown, radiation therapy process <NUM> is substantially similar to radiation therapy process <NUM> of <FIG>, except that steps <NUM>, <NUM>, and <NUM> of radiation therapy process <NUM> are not included in radiation therapy process <NUM>. Instead, the same process flow is performed for each treatment fraction, and there is no check to confirm that the patient can maintain an inspiration level that is equal to or greater than predetermined threshold level <NUM>. In <FIG>, each of blocks <NUM> - <NUM> of radiation therapy process <NUM> is substantially the same as a corresponding step in radiation therapy process <NUM>, and therefore is numbered accordingly.

<FIG> is an illustration of computing device <NUM> configured to perform various embodiments of the present disclosure. For example, in some embodiments, computing device <NUM> can be implemented as image acquisition and treatment control computer <NUM> and/or remote control console <NUM> in <FIG>. Computing device <NUM> may be a desktop computer, a laptop computer, a smart phone, or any other type of computing device suitable for practicing one or more embodiments of the present disclosure. In operation, computing device <NUM> is configured to execute instructions associated with radiation therapy process <NUM> and/or radiation therapy process <NUM>, as described herein. It is noted that the computing device described herein is illustrative and that any other technically feasible configurations fall within the scope of the present disclosure.

As shown, computing device <NUM> includes, without limitation, an interconnect (bus) <NUM> that connects a processing unit <NUM>, an input/output (I/O) device interface <NUM> coupled to input/output (I/O) devices <NUM>, memory <NUM>, a storage <NUM>, and a network interface <NUM>. Processing unit <NUM> may be any suitable processor implemented as a central processing unit (CPU), a graphics processing unit (GPU), an application-specific integrated circuit (ASIC), a field programmable gate array (FPGA), any other type of processing unit, or a combination of different processing units, such as a CPU configured to operate in conjunction with a GPU or digital signal processor (DSP). In general, processing unit <NUM> may be any technically feasible hardware unit capable of processing data and/or executing software applications, including radiation therapy process <NUM> and/or radiation therapy process <NUM>.

I/O devices <NUM> may include devices capable of providing input, such as a keyboard, a mouse, a touch-sensitive screen, and so forth, as well as devices capable of providing output, such as a display device and the like. Additionally, I/O devices <NUM> may include devices capable of both receiving input and providing output, such as a touchscreen, a universal serial bus (USB) port, and so forth. I/O devices <NUM> may be configured to receive various types of input from an end-user of computing device <NUM>, and to also provide various types of output to the end-user of computing device <NUM>, such as displayed digital images or digital videos. In some embodiments, one or more of I/O devices <NUM> are configured to couple computing device <NUM> to a network.

Memory <NUM> may include a random access memory (RAM) module, a flash memory unit, or any other type of memory unit or combination thereof. Processing unit <NUM>, I/O device interface <NUM>, and network interface <NUM> are configured to read data from and write data to memory <NUM>. Memory <NUM> includes various software programs that can be executed by processor <NUM> and application data associated with said software programs, including radiation therapy process <NUM> and/or radiation therapy process <NUM>.

<FIG> is a block diagram of an illustrative embodiment of a computer program product <NUM> for implementing a method for radiation therapy, according to one or more embodiments of the present disclosure. Computer program product <NUM> may include a signal bearing medium <NUM>. Signal bearing medium <NUM> may include one or more sets of executable instructions <NUM> that, when executed by, for example, a processor of a computing device, may provide at least the functionality described above with respect to <FIG>.

In some implementations, signal bearing medium <NUM> may encompass a non-transitory computer readable medium <NUM>, such as, but not limited to, a hard disk drive, a Compact Disc (CD), a Digital Video Disk (DVD), a digital tape, memory, etc. In some implementations, signal bearing medium <NUM> may encompass a recordable medium <NUM>, such as, but not limited to, memory, read/write (R/W) CDs, R/W DVDs, etc. In some implementations, signal bearing medium <NUM> may encompass a communications medium <NUM>, such as, but not limited to, a digital and/or an analog communication medium (e.g., a fiber optic cable, a waveguide, a wired communications link, a wireless communication link, etc.). Computer program product <NUM> may be recorded on non-transitory computer readable medium <NUM> or another similar recordable medium <NUM>.

Aspects of the present disclosure may be embodied as a system, method or computer program product. Accordingly, aspects of the present disclosure may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, micro-code, etc.) or an embodiment combining software and hardware aspects that may all generally be referred to herein as a "circuit," "module" or "system. " Furthermore, aspects of the present disclosure may take the form of a computer program product embodied in one or more computer readable medium(s) having computer readable program code embodied thereon.

Claim 1:
A system (<NUM>) for performing a treatment fraction of radiation therapy, the system (<NUM>) comprising:
an X-ray imager (<NUM>);
a treatment-delivering X-ray source (<NUM>) configured to direct treatment X-rays (<NUM>) to a target volume (<NUM>) of patient anatomy;
an imaging X-ray source (<NUM>) configured to direct imaging X-rays (<NUM>) through the target volume (<NUM>) and toward the X-ray imager (<NUM>); and
a processor (<NUM>);
a signal bearing medium (<NUM>) including one or more sets of executable instructions (<NUM>) that, when executed by said processor (<NUM>), provide the functionality of:
while a patient is disposed in a first position and maintains a first inspiration level, acquire (<NUM>) a set of projection images, generated by the X-ray imager(<NUM>), of the target volume (<NUM>) associated with the patient;
characterized by further providing the functionality of:
based on a treatment planning digital volume associated with the radiation therapy process (<NUM>, <NUM>) and the set of projection images, generate (<NUM>) a synthetic digital volume that includes the target volume (<NUM>);
based on a treatment plan associated with the treatment planning digital volume and on the synthetic digital volume, generate (<NUM>) a modified treatment fraction; and
while the patient remains in the first position and maintains at least the first inspiration level, cause the modified treatment fraction to be performed (<NUM>) by the treatment-delivering X-ray source (<NUM>).