Image-guided radiotherapy
Patent Information
- Authority / Receiving Office
- DE · DE
- Patent Type
- Patents
- Current Assignee / Owner
- ELEKTA AB
- Filing Date
- 2014-04-28
- Publication Date
- 2026-07-23
Smart Images
Figure 00000000_0000_ABST
Abstract
Description
AREA OF INVENTION
[0001] The present invention relates to image-guided radiotherapy. STATE OF THE ART
[0002] Radiation therapy is the procedure for treating a tumor or other lesion (hereinafter referred to as "tumor") by directing a beam of harmful radiation, usually ionizing radiation such as an X-ray or electron beam, onto the lesion. The beam can be generated by an electron gun, such as a linear accelerator, which produces a beam of high-energy electrons (typically in the range of 2–5 MeV) that can be directed at the patient or at an X-ray target to generate an X-ray beam. A flattening filter can be inserted into the beam to produce more uniform illumination across the beam cross-section.
[0003] The beam clearly has the potential to damage the normal, healthy tissue surrounding the lesion as well as the tumor itself. Therefore, it is common practice to focus the beam so that the dose delivered to healthy tissue is minimal, while the dose delivered to the tumor is maximized—or at least optimized, since it may be necessary to limit the total dose delivered in any one session to avoid necrosis or other potential complications. The direction from which the beam is delivered to the tumor can also be varied by positioning the source on a frame that rotates around the patient, ensuring that different amounts of healthy tissue are in front of or behind the tumor at any given time, and minimizing the duration for which the additional dose is delivered to any given region of healthy tissue.
[0004] Many types of collimators are available, notably the "multi-lamella collimator," which has a large number (typically 40, 80, or 160) of lamellae, each long and thin but relatively deep in the direction of the beam. These are arranged side by side, with their longitudinal edges projecting into the beam from one side, and they can be moved independently into and out of the beam field. The tips of the lamellae thus form an edge whose shape can be arbitrarily configured by moving individual lamellae into and out of the beam.
[0005] There are various methods for delivering a beam using the aforementioned arrangements. Conformal rotation therapy, for example, involves rotating the radiation source around the tumor during treatment, with the multi-lamella collimator being adjusted so that the cross-sectional shape of the beam corresponds to the projected shape of the tumor along the beam's current direction.In intensity-modulated radiotherapy, mathematical methods are used that start with a segmented volume, which determines regions that are inside the tumor (along with a desired dose), regions that are outside the lesion, and regions where the dose needs to be minimized, and defines the device possibilities and derives a treatment plan that includes the rotation of the frame, collimator shapes and dose rates, resulting in a three-dimensional dose distribution that takes the different conditions into account.
[0006] All delivery procedures share the same requirement: the current shape and location of the lesion must be known. However, this changes over time and between treatments. As the tumor shrinks in size as a result of treatment, it may shift, and other organs that were displaced by it may return to their normal position. Generally, abdominal organs also tend to shift over time in any case, especially those below the diaphragm. In the simplest case, the patient may move during treatment, or they may be positioned slightly differently on the device.
[0007] Typically, radiotherapy is administered in a series of individual doses on a regular (i.e., daily) basis—usually referred to as "treatment fractions" or simply "fractions." To detect changes in tumor position or shape between fractions, i.e., "fractional movement," a diagnostic image is taken immediately before treatment to determine the current position and / or shape of the tumor. This is then used to adjust the treatment plan accordingly. The diagnostic image may be one or more X-ray images or a computed tomography (CT) scan.This diagnostic imaging technique requires a lower-energy X-ray source to produce high-quality images, typically in the range up to 125 keV, instead of the high-energy beam (5 MeV) used for treatment, which, while suitable for imaging, provides very poor contrast between human tissue types. Often, a low-energy diagnostic source is mounted on the same rack as the therapeutic source to facilitate this. Because the rack can be rotated around the patient to allow irradiation from different directions, this rotation can be used to enable the diagnostic source to generate a digital volume tomography (cone-beam CT) reconstruction.Typically, the diagnostic source is located on the rack at 90 degrees to the therapeutic source, so that with the corresponding imaging plates for each source, the individual elements on the rack are spaced apart from each other and access is maximized.
[0008] It is possible to use the therapeutic beam to take images of the patient during treatment, a so-called "portal image." However, as already mentioned, the image quality is poor due to a pronounced lack of contrast. This is generally only sufficient to confirm the rough positioning of the patient.
[0009] To control patient movement during a fraction, i.e., for "in-fraction motion management" ("IFMM"), it is more common to attempt to fix the patient in position. The patient can be placed in a custom-made cushion of an appropriate shape, ensuring consistent positioning on the treatment table and limiting movement during the treatment fraction, as disclosed, for example, in our application WO2009 / 006925. Fixations may be provided to limit patient movement and / or to force internal organs into a fixed position, as shown, for example, in our application WO2008 / 040379. For radiotherapy of the head region, a frame can be attached directly to the skull and used to fix the head in a reproducible position.Molded face masks can also be used to position the patient's head in a reproducible position; although this is less precise than a frame, it is much less invasive.
[0010] Some efforts are made to detect and respond to any changes in the patient's position, such as using reflective markers attached to the outside of the patient that are optically detectable. However, these provide an indirect measure of tumor position and are therefore less precise.
[0011] US7227925 discloses a radiotherapy treatment machine that includes a stereoscopic imaging system comprising a rotatable open frame on which a therapeutic radiation source is positioned between two diagnostic radiation sources, each with an associated diagnostic imager. The images from the two diagnostic sources are combined to produce a stereoscopic image that includes position and depth information used to guide the therapeutic source. To produce a good stereoscopic image, two diagnostic sources are required, ideally positioned symmetrically on either side of the therapeutic source. SUMMARY OF THE INVENTION
[0012] In a first embodiment, the present invention thus provides a radiotherapy device comprising a rotatable frame supporting a therapeutic radiation source and a diagnostic radiation source, wherein the two sources are rotationally (or angularly) spaced apart from each other about a rotational axis of the frame, wherein at least one collimator is connected to and arranged with the therapeutic radiation source to limit the cross-sectional area of a beam generated by that source, and a control device arranged to perform a treatment fraction using the device by causing the device to: i. take pictures of a patient using the diagnostic radiation source, ii. store these images at least temporarily, iii.iv. then, after further rotation of the frame, to select a stored image that was taken when the diagnostic radiation source was in a rotation position corresponding to the current rotation position of the therapeutic radiation source, and iv. to control the beam relative to the patient (such as by adjusting the collimator or moving a patient support) using the information obtained from the selected image.
[0013] The appropriate rotational position is ideally one in which the therapeutic radiation source is in the same or substantially the same rotational position as the diagnostic radiation source was in when the image was taken.
[0014] In a second embodiment, the invention provides a radiotherapy device comprising a rotatable frame supporting a therapeutic radiation source and a diagnostic radiation source, at least one collimator connected to the therapeutic radiation source and arranged to limit the cross-sectional area of a beam generated by that source, and a reconstruction device arranged to: i. acquire two-dimensional images of a patient using the diagnostic radiation source, ii. store these images at least temporarily, and iii. apply a recency threshold to the stored images in order to exclude images older than the threshold, iv.to select at least three such stored images corresponding to the recency threshold and to reconstruct a CT volume using the selected images, and to have a control device arranged to perform a treatment fraction or treatment session using the device and to control the collimator using the information obtained from the CT volume.
[0015] The recency threshold can be applied by deleting images beyond the threshold, either by discarding them or ignoring them. An example of a suitable threshold is a maximum value for the time elapsed since the image was received. Another example is a maximum value for the angle the rack has rotated since the image was received. A further example of a suitable threshold is one that is satisfied by an image if the image is one of the n most recent images, where n is a pre-selected number.
[0016] The therapeutic and diagnostic radiation sources can be located in the same head. Ideally, the therapeutic and diagnostic radiation sources are fed by the same linear accelerator, maintained by making different adjustments to it. Our previous applications WO1999 / 040759, WO2001 / 011929 and WO2001 / 011928 (which are incorporated herein by reference) show how this can be done.
[0017] Alternatively, the therapeutic radiation source and the diagnostic radiation source can be provided in separate heads. The resulting two sources are then preferably arranged radially apart from each other around a rotational axis of the frame – ideally at an acute angle, preferably of less than 45 degrees.
[0018] The therapeutic radiation source typically emits focused radiation with an energy of at least 1 MeV. Similarly, the diagnostic radiation source typically emits focused radiation with an energy of at least 50 keV, typically up to 150 keV.
[0019] The collimator is preferably a multi-lamella collimator, but can be of any design suitable for limiting the therapeutic beam. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] One embodiment of the present description is described below by way of example with reference to the accompanying figures. These show:
[0021] Fig. 1 the arrangement of a radiotherapy device according to a first embodiment; and
[0022] Fig. 2 the arrangement of a radiotherapy device according to a second embodiment. DETAILED DESCRIPTION OF THE EXECUTION FORM
[0023] To ensure the patient is correctly positioned before treatment and to detect any changes in tumor position, shape, and / or patient anatomy between fractions, a cone-beam CT scan (“CBCT”) is typically performed before treatment begins, and the patient's position is adjusted so the dose can reach the desired target. Sometimes, one or more intermediate CBCT scans are performed during the treatment fraction, pausing the treatment and then repositioning the patient to further improve treatment accuracy.
[0024] The inherent problem is that perfect patient fixation during treatment is difficult. When a frame is attached to the skull, patient movement is typically very small, for example, less than 0.5 mm. However, with other fixation techniques, such as a face mask, patient movement tends to be significantly greater. Extracranial treatments present greater challenges in target fixation, with correspondingly problematic outcomes. Meanwhile, accuracy of delivery is critical because lower accuracy necessitates a larger treatment volume around the tumor (the so-called planning target volume or PTV) to ensure that the entire tumor is treated, thereby increasing the dose delivered to healthy tissue and potentially endangering nearby delicate structures.
[0025] The embodiments of the present invention are particularly suitable for managing slow to medium IFMM (Internal Functional Microwave Mastication) rates, such as in treatments of the cranial cavity, skull, soft tissue, spine, cervical spine, and prostate, where the target is normally completely still during treatment, and where non-periodic spontaneous movement can occur at any time, or a slower deviation of the target position at a rate that is normally several seconds per millimeter (although individual faster movements could also occur). However, the total dose to the planned target volume must be controlled so that spontaneous rapid movements can also be tolerated, provided that they are very few and are compensated for within a few seconds of their occurrence, thus limiting the overall dose error.There are two operating modes provided by the invention, a first one which is based on the in . Fig. 1 embodiment shown is applicable, and a second embodiment which is applicable to the embodiment of the Fig. 1 and the embodiment of the Fig. 2 is applicable.
[0026] With reference to Fig. 1, which shows the first embodiment, has a radiotherapy device 10 a bracket 12 a bracket that is rotatable around a central horizontal axis. Usually, the majority of the bracket is 12 behind a wall or a false wall or coverings 14 hidden, through which the bracket protrudes. From the bracket 12 A frame protrudes from it and supports a therapeutic head. 16 , which generates a high-energy beam suitable for therapeutic purposes and directed along the central horizontal axis. A linear accelerator is housed in the mount to generate the beam.12 and placed on the frame that goes into the therapeutic head 16 The process involves directing a relativistic electron beam from the accelerator onto an X-ray target to generate a beam of high-energy X-rays in the appropriate direction. If necessary, this beam is then filtered, for example using a flattening filter, and collimated by block collimators and multi-blade collimators to produce a therapeutically usable beam.
[0027] A patient table 18 It is positioned directly below the central horizontal axis to position a patient, with the target or tumor site located at the intersection of the central horizontal axis and the central axis of the therapeutic beam – this point is typically referred to as the “isocenter”. The in Fig. The patient table, shown schematically, is typically driven by suitable motors to allow adjustment in all six degrees of freedom (three translational and three rotational) in order to position the patient precisely at the isocenter. The treatment room is usually equipped with weak laser markers that converge at the isocenter from a number of directions, such as the three orthogonal directions, to assist this procedure.
[0028] A diagnostic head 20 is mounted on a second frame that is positioned a few degrees away from the therapeutic head. 16 , for example, at an angle of 10–45°. This emits a low-energy diagnostic beam of up to approximately 125 keV towards the isocenter, which is suitable for generating high-contrast images of human tissue. Fig. Figure 1 shows the diagnostic head 20at the preferred upper limit at an angle of 45° to the therapeutic head 16 The two heads should be mounted on the holder relative to the direction of rotation. 22 be positioned in such a way that the diagnostic head 20 during rotation in front of the therapeutic head 16 is located on the bracket. 12 A flat-plate imager can also be used. 24 directly opposite the diagnostic head 20 It is intended to obtain a two-dimensional X-ray image of the patient. A second flat-plate imaging system can also be positioned opposite the therapeutic head. 16 It is intended to be provided; however, this image source is not shown.
[0029] Control units are for the two radiation heads. 16 , 20 and for the flat plate imager 24 provided. They feature a control unit. 26for the therapeutic head, which controls the therapeutic beam and the collimators, and a control unit 28 for the diagnostic head, which controls and activates the diagnostic beam, an image sensor control unit 30 , which is the flat plate imager 24 activated and reads the image together with the frame angle and links them together, and a frame control unit 32 , which hold the motors in the bracket 12 controls the bracket 12 and to rotate the racks as needed. All four control units generate a report for a central control and process computer. 34 . Of course, the control functions can also be designed differently, for example by further subdividing different functions and / or by combining functions.
[0030] According to the first mode of operation, the device delivers a treatment fraction, alternating between emitting one or more pulses of the therapeutic beam and emitting one or more pulses of the diagnostic beam (and capturing the corresponding images), while the holder 12 to place a patient on the patient table 18 It is rotated. Each 2D image is generated by the computer. 34 together with the rotation angle at which the recording was made, derived from the frame control unit 32 , saved. The images are from the computer 34 The system analyzes to identify positioning errors and adjust the collimator settings required when the therapeutic beam is emitted from this rotation angle. Then, the mount is adjusted to a further angle corresponding to the angular difference between the two heads. 16 , 20Once the rotation has begun, the set collimator settings are sent to the control unit. 26 passed on for the therapeutic head.
[0031] In other words, as the fixture rotates during treatment, a continuous series of diagnostic images is acquired and inspected for movement. The therapeutic beam is guided by an image previously acquired by the diagnostic system while it was at the same angle as the therapeutic beam. When the therapeutic beam is at the same angle as the diagnostic beam, the 2D information contains all the data necessary to precisely target the patient—provided that target is visible in the 2D image (e.g., via bone anatomy, markings, and the like). Although the target may have shifted from its previous position in any direction along the beam axis, such movements only marginally affect the dose delivered to the target, and within acceptable limits.
[0032] For an angular velocity of (for example) 30 degrees per second, the treatment error (or delay) is approximately one second, and it will be possible to track the target with a delay of one second. This is acceptable for spinal or intracranial treatments using a facial fixation mask, and the resulting dosimetric error would be very small. The main controllable factor is, of course, the chosen angle between the two heads, with a smaller angle allowing the use of a more current image and thus a smaller error. In practice, however, the lower limit of the angle will very likely be constrained by spatial limitations and (possibly) by the minimum processing time required for each image.
[0033] In the second mode of operation, instead of being guided using a single, most recent 2D image, the therapeutic beam is guided according to a CBCT image generated from a rotating selection of the most recent 2D images. Thus, the device is controlled during treatment to continuously generate images timed between pulses of the therapeutic beam for minimal interference. A CBCT image stack is maintained, to which new images are added, and images older than a defined threshold are deleted. Alternatively, all or substantially all images can be retained, and a selection filter can be applied to choose those images that meet a recency criterion for use by the CT reconstruction algorithm.This generates a continuous volumetric image that follows the movements of the patient's anatomy, averaged over the relevant most recent period. The algorithm could also be improved to give more weight to newer images in determining position.
[0034] A preferred image freshness criterion is simply to retain (or select) the images acquired during the last 180° rotation of the frame. This has the advantage of allowing for high-quality reconstruction, as all perspectives are taken into account. At a rotation rate of (for example) 30° / s, this corresponds to 6 seconds, meaning it can respond well to patient movement. However, other angle values, such as 90°, could be chosen, or other freshness criteria could be used. For example, a predefined time limit could be used, where images "expire" after a predetermined time (e.g., 5 seconds). Alternatively, a predetermined number of images could be stored, effectively creating a simple FIFO buffer for the images, where with each new image, the oldest image remaining in the buffer is overwritten or expires.One advantage of using volumetric images is that they increase visibility and the ability to track soft tissue movements.
[0035] The second operating mode could be implemented using the method described with reference to Fig. The device described in point 1 can be implemented. Alternatively, it could be the device described in point 1. Fig. Use the second embodiment shown in section 2. This radiotherapy device 100 has a bracket 112 on, which rotates around a central horizontal axis, which is generally the same as the bracket 12 the Fig. 1. A single head. 116It generates either a high-energy beam suitable for therapeutic purposes or (selectably) a low-energy diagnostic beam of up to approximately 125 keV, suitable for producing high-contrast images of human tissue. Both beams are emitted along the same axis towards the isocenter.
[0036] A linear accelerator is in the mount. 112 and placed on the frame that goes into the head 116The process involves directing a relativistic electron beam, with its energy adjustable, from the accelerator onto an X-ray target to generate a beam of high-energy X-rays in the appropriate direction. If necessary, this beam is then filtered, for example by means of a flattening filter, and collimated by block collimators and multi-blade collimators to produce a therapeutically usable beam. The emitted energy of the X-ray beam can be controlled by adjusting the energy of the electron beam, as explained in our earlier applications WO1999 / 040759, WO2001 / 011929 and WO2001 / 011928 (all of which are incorporated into this description by reference).
[0037] A patient table 118 is also planned, which the table 18 according to Fig. 1 corresponds to.
[0038] A flat-plate imaging device 124 is also related to storage 112directly opposite the single head 116 designed to capture a two-dimensional X-ray image of the patient. This can be processed by an image sensor control unit. 130 can be controlled to capture only diagnostic images or both diagnostic and portal images.
[0039] For the radiation head 116 and for the flat plate imager 124 Control units are provided. These feature a radiation head control unit. 126 , which controls the therapeutic beam, the diagnostic beam and the collimators, an imaging sensor control unit 130 (as mentioned), which is the flat plate imager 124 controls and reads the image, and a frame control unit 132 on, which holds the motors in the bracket 112 steers to adjust the bracket 112 and to rotate the racks as needed. All four control units generate a report for a central control and process computer.134 . Of course, the control functions can also be designed differently, for example by further subdividing different functions and / or by combining functions.
[0040] It is naturally assumed that many modifications to the embodiment described above can be made without deviating from the scope of the present invention. Likewise, the technique can also be applied to radiotherapy designs other than those disclosed in the present description. Such alternative forms may include different radiation forms, such as electron or proton beams, or other forms of collimation, or other delivery methods, such as those employing a second angle of the treatment head for (for example) non-coplanar treatment geometries. QUOTES INCLUDED IN THE DESCRIPTION
[0041] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature
[0042] WO 2009 / 006925
[0009] WO 2008 / 040379
[0009] US 7227925
[0011] WO 1999 / 040759 [0016, 0036] WO 2001 / 011929 [0016, 0036] WO 2001 / 011928 [0016, 0036]
Claims
[1] Radiotherapy device comprising the following: a rotatable frame that supports a therapeutic radiation source and a diagnostic radiation source, wherein both sources are spaced apart from each other with respect to rotation about an axis of rotation of the frame; at least one collimator connected to the therapeutic radiation source, arranged to limit the cross-sectional area of a beam produced by that source; a control device arranged to perform a treatment fraction using the device by causing the device to do the following: i. To take pictures of a patient using the diagnostic radiation source, ii. to store these images at least temporarily and iii. subsequently, after further rotation of the frame, to select a stored image that was taken when the diagnostic radiation source was in a rotational position corresponding to the current rotational position of the therapeutic radiation source; and iv. to control the beam relative to the patient using the information obtained from the selected image. [2] Radiotherapy device according to claim 1, wherein the beam is controlled relative to the patient by adjusting the collimator. [3] Radiotherapy device according to claim 1 or claim 2, which furthermore includes a patient holder for the patient and in which the beam is controlled relative to the patient by adjusting the patient holder. [4] Radiotherapy device according to one of the preceding claims, wherein the corresponding rotation position is a position in which the therapeutic radiation source is in the same rotation position as the diagnostic radiation source was when the image was taken. [5] Radiotherapy device comprising the following: a rotatable frame that supports a therapeutic radiation source and a diagnostic radiation source; at least one collimator connected to the therapeutic radiation source, arranged to limit the cross-sectional area of a beam produced by that source; a reconstruction device arranged to: i. to take two-dimensional images of a patient using the diagnostic radiation source, ii. to store these images at least temporarily and iii. to apply a recency threshold to the stored images in order to exclude images that are older than the threshold, iv. to select at least three such stored images that meet the recency threshold and to reconstruct a CT volume using the selected images; and a control device arranged to perform a treatment fraction using the device and to control the collimator using the information obtained from the CT volume. [6] Radiotherapy device according to claim 5, wherein the recency threshold is applied by deleting images beyond the threshold. [7] Radiotherapy device according to claim 5 or claim 6, wherein the recency threshold is met by an image if the image was taken less than a preselected time ago. [8] Radiotherapy device according to claim 5 or claim 6, wherein the recency threshold is met by an image when the rotatable frame has rotated by less than a preselected angle since the image was taken. [9] Radiotherapy device according to claim 5 or claim 6, wherein the recency threshold is met by an image when the image is one of the most recent n images, where n is a preselected number. [10] Radiotherapy device according to one of the preceding claims, wherein the therapeutic radiation source and the diagnostic radiation source are provided in the same head. [11] Radiotherapy device according to one of the preceding claims, in which the therapeutic radiation source and the diagnostic radiation source are supplied by the same linear accelerator, obtained by making different adjustments to it. [12] Radiotherapy device according to any one of claims 1 to 9, wherein the therapeutic radiation source and the diagnostic radiation source are provided in separate heads. [13] Radiotherapy device according to claim 12, in which the two sources are arranged radially apart from each other about an axis of rotation of the frame. [14] Radiotherapy device according to one of claims 12 or 13, wherein the two sources are spaced radially apart at an angle of less than 90 degrees. [15] Radiotherapy device according to one of claims 12, 13 or 14, wherein the two sources are spaced radially apart at an angle of less than 45 degrees. [16] Radiotherapy device according to one of the preceding claims, wherein the therapeutic radiation source emits a focused radiation with an energy of at least 1 MeV. [17] Radiotherapy device according to one of the preceding claims, wherein the diagnostic radiation source emits a focused radiation with an energy of at least 50 keV. [18] Radiotherapy device according to one of the preceding claims, wherein the collimator is a multi-lamella collimator.