Description:PRIORITY CLAIM
[0001] This is an application for patent of addition for the patent application numbered 4150/CHE/2014 filed with Indian patent Office, Chennai on 25th August 2014entitled “Radiotherapy apparatus to generate photon beam, electron beam and CBCT (Cone Beam Computed Tomography) image with a greater FOV (Field Of View)”, the entirety of which is expressly incorporated herein by reference.
PREAMBLE TO THE DESCRIPTION:
[0002] The following specification particularly describes the invention, and the manner in which it has to be performed:
DESCRIPTION OF THE INVENTION
Technical field of the invention

[0003] The present invention relates generally to a radiotherapy apparatus equipped with a stereotactic imaging system to capture orthogonal images of a patient. The present invention particularly relates to an imaging system, where the captured images are used to validate the positional accuracy of the patient with respect to the treatment planning field.
Background of the invention
[0004] Radiotherapy is a process of using high-energy ionizing radiation to control the growth of malignant or abnormal tissues and treat diseases in patients. Typically, various doses of radiation are delivered to the patient in the form of a beam which is directed towards a target area in order to control and eliminate the growth of abnormal target cells. Radiotherapy is typically characterized by a low dose per fraction (e.g., 100-200 centi-gray), shorter fraction times (e.g., 10 to 30 minutes per treatment) and hyper-fractionation (e.g., 30 to 45 fractions). A ring gantry-based system tends to exhibit relatively high mechanical stability, i.e., less of the deformation problems, and thus can reproducibly and accurately position the radiation source. The ring gantry having radiotherapy apparatus generates stereotactic images and Cone Beam Computed Tomography (CBCT) image. These are the diagnostic tools for providing a type 3-D volumetric image with considerable prospects.
[0005] One of the common practices in the radiotherapy treatment is the Image guided radiotherapy (IGRT), wherein the Image guided radiotherapy (IGRT) can be performed by comparing the 3-dimensional images of the patient acquired when the patient is resting on the couch and the captured images are compared with the Computerized Tomography (CT) images captured before generating a treatment plan. Further, Image guided radiotherapy (IGRT) can also be performed by acquiring at the least two 2-Dimensional images of the patient and comparing the acquired images with the Digitally Reconstructed Radiographs (DRR) acquired from the planning Computerized Tomography (CT). These comparisons provide information of misalignment of the treatment field with respect to the patient in 6 degrees of freedom (DOF) for three dimensional comparisons and 3 degrees of freedom (DOF) for two dimensional comparisons. Another technique used for imaging is the stereotactic imaging, wherein stereotactic imaging facilitates identification of shift corrections using orthogonally placed stereo detectors.
[0006] Further, Image guided radiotherapy (IGRT) based on Cone Beam Computed Tomography (CBCT) can produce shift correction in 6 degrees of freedom (DOF), however the time taken to acquire a Cone Beam Computed Tomography (CBCT) and register requires at least around 60 seconds and if the target area is near to lungs, there is a movement of the other internal organs in the target area along with the breathing, thus the images acquired show a shift in the reference with respect to internal organs. Therefore, this leads to an inaccurate geometry of reconstruction.
[0007] Further, the dose received by the patient during the image acquisition for reconstructing the Cone Beam Computed Tomography (CBCT) is considerably high compared to the dose received during 2D or stereotactic imaging. The Image guided radiotherapy (IGRT) based on 2D imaging acquired in orthogonal planes provide patient shift corrections only in 3 degrees of freedom (DOF). The drawback of this method is that the time interval between capturing the image in various orthogonal planes requires at least 60 seconds and this leads to movement of internal organs as per patient breathing pattern.
[0008] The Patent Application No. US20070003123A1 entitled “Precision registration of X-ray images to cone-beam CT scan for image-guided radiation treatment” discloses a method for precision registration of X-ray images to cone-beam CT scan for image-guided radio surgery includes acquiring 2-D pre-treatment X-ray images of a region of interest, acquiring a 2-D X-ray image of the region of interest at approximately a time of treatment, registering the 2-D X-ray image with a corresponding 2-D pre-treatment X-ray image to obtain a 2-D registration result at approximately the time of treatment, and converting the 2-D registration result into a 3-D tracking result to track the region of interest.
[0009] The Patent Application No. US9218643B2 entitled “Method and system for registering images” discloses a system for registering images includes an image registration unit. The image registration unit is configured to receive first image data for a first image in an N-dimensional space, receive second image data for a second image in the N-dimensional space, calculate a field of update vectors that maps the first image into a moving image, and map the first image into the moving image using the field of update vectors such that the moving image more closely matches the second image. The field of update vectors includes a plurality of N+M dimensional update vectors, each update vector having N spatial components and M extra components. N is a number greater than zero, and M is a number greater than zero. The M extra components of the plurality of update vectors identify portions of the first image that are assigned external values during the mapping the first image into the moving image.
[0010] The Patent Application No. US20050080332A1 entitled “Near simultaneous computed tomography image-guided stereotactic radiotherapy” discloses a targeting system for administering radiation to a patient and methods therefore are provided. The targeting system includes a stereotactic frame system for immobilizing the patient; an imaging scanner for acquiring images of a patient's anatomy, wherein at least one image is acquired during a planning phase, and at least one image is acquired during a pretreatment phase; a processor for fusing the planning image to the pretreatment image and for determining a shift, for example, translation and rotation, between the images to locate a predetermined portion of the patient's anatomy; and a radiation source for delivery of radiation to the predetermined portion of the patient's anatomy.
[0011] Hence, there is a need for a radiotherapy apparatus for stereotactic imaging facilitating validation of the positional accuracy of the patient with respect to the treatment planning field in Image guided radiotherapy (IGRT).
Summary of the invention
[0012] The present invention overcomes the drawbacks of the prior art by providing a radiotherapy apparatus facilitating patient positioning during Image guided radiotherapy (IGRT), wherein the radiotherapy apparatus validates the positional accuracy of a patient with respect to the treatment planning field. The radiotherapy apparatus comprises a rotational ring gantry including at least one X-ray tube to generate the X-rays for imaging the patient. The radiotherapy apparatus further comprises a detector located on opposite side of each KV X-ray source, facilitating image capture of the patient. The rotational ring gantry further comprises a LINAC (Linear Accelerator) X-ray tube to generate a high energy X-rays used for radiation treatment.
[0013] The present invention facilitates patient positioning by aligning the patient’s body with the KV X-ray source in 6 degrees of freedom (DOF). The radiotherapy apparatus uses an Oncology Information System (OIS) application to enable demarcation of the area of interest during planning of the Computerized Tomography (CT) through contouring prior to treatment of the patient.
[0014] Further, the rotating ring gantry includes at least one KV X-ray source, wherein the KV X-ray source facilitates generation of beam of imaging radiation directed towards the patient on the treatment table. The detectors mounted on the rotating ring gantry includes a first movable detector and second movable detector, wherein the first movable detector and the second movable detector facilitates detection of the beam of imaging radiation after it has passed through the patient treatment table. The first movable detector facilitates generation of a full fan X-ray beam or a half fan X-ray beam of imaging radiation for small field of view, wherein the full fan beam is generated without moving the first detector. The second movable detector facilitates generation of full fan X-ray beam or a half fan X-ray beam of imaging radiation for small field of view. The first movable detector and the second movable detector are located on the inner periphery of the rotating ring gantry to capture the stereotactic images.
[0015] The present invention facilitates utilizing the first movable detector and the second movable detector along with the Linear Accelerator (LINAC) X-ray tube placed orthogonally or separated by a significant angle on the rotating ring gantry, in order to capture the images of the patient. The acquired images of the patient are compared with the Digitally Reconstructed Radiograph (DRR) images to validate the positional accuracy of the patient with respect to the treatment planning field.
[0016] According to the present invention, the stereotactic imaging with at least one detector is used to capture an image of the patient orthogonally, wherein the images are captured with a time difference of less than a second. The system of the present invention facilitates selecting a region of interest to register the patient while planning the Computerized Tomography (CT) in a 3-Dimensional plane, wherein the region of interest is further converted into a 2-Dimensional area on the Digitally Reconstructed Radiograph (DRR) generated prior to treatment. Further, the said region of interest is considered as a reference with respect to the image of the patient acquired during the initiation of the treatment.
[0017] There are several advantages of the present invention, including significant reduction in the dose received by the patient during the Image Guided Radiotherapy (IGRT) without compromising on the accuracy of positioning in 6 degrees of freedom (DOF). The system enables the healthcare practitioner to perform the Image Guided Radiotherapy (IGRT) before every field of treatment. Further, the system significantly reduces the time taken to set up the patient for treatment. The system ensures the accuracy in patient positioning in 6 degrees of freedom (DOF) with a minimum dose and in a short interval of time.
[0018] It is to be understood that both the foregoing general description and the following details description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
Brief description of the drawings
[0019] The foregoing and other features of embodiments will become more apparent from the following detailed description of embodiments when read in conjunction with the accompanying drawings. In the drawings, like reference numerals refer to like elements.
[0020] Figure 1 illustrates a perspective view of the radiotherapy apparatus disclosing the rotating ring gantry with X ray sources and detectors for stereotactic imaging of the patient to capture orthogonal images.
[0021] Figure 2 illustrates a flow diagram disclosing the method to validate the positional accuracy of the patient with respect to the treatment planning field.
Detailed description of the invention
[0022] Reference will now be made in detail to the description of the present subject matter, which is shown in the illustrations. Various changes and modifications obvious to one skilled in the art to which the invention pertains are deemed to be within the scope, and contemplation of the invention.
[0023] The present invention discloses a radiotherapy apparatus to facilitate patient positioning using stereotactic imaging with at least one detector to capture images of a patient orthogonally, wherein the acquired images of the patient are compared with the Digitally Reconstructed Radiograph (DRR) images of the patient to validate the positional accuracy of the patient with respect to the treatment planning field.
[0024] Figure 1 illustrates a perspective view of the radiotherapy apparatus (100) disclosing the rotating ring gantry (101) with KV X-ray sources and detectors for stereotactic imaging of the patient to capture orthogonal images, wherein the rotating ring gantry (101) comprises at least one KV X-ray source (102a and 102b)to generate X-rays for imaging the patient. The rotating ring gantry (101) has a wide central opening (more than 700 mm) to accommodate the body of the patient positioned along a longitudinal axis and extending there through.
[0025] The rotating ring gantry (101) further comprises at least one detector including a first movable detector (104) and a second movable detector (103) located on opposite side of each KV X-ray source (102a and 102b) to detect the beam of imaging radiation after it has passed through the patient’s table. The first movable detector (104) and the second movable detector (103) are located on the inner periphery of the rotating ring gantry (101) to capture the stereotactic images. The first movable detector (104) and the second movable detector (103) are mounted ISO centrically (105) on the rotating ring gantry (101) which are located at orthogonal angle apart from each other. The beam of imaging radiation is said to be used forImage Guided Radiotherapy (IGRT) based CBCT (Cone Beam Computed Tomography) imaging and stereotactic imaging.
[0026] The rotating ring gantry (101) further comprises a LINAC (Linear Accelerator) X-ray tube (106) facilitating generation of high energy X rays used for radiation treatment. The LINAC (Linear Accelerator) X-ray tube (106) is mounted on the rotating ring gantry (101) to produce high energy X-rays for radiation treatment.
[0027] The rotating ring gantry (101) generates orthogonal images of the patient with full fan mode of X-ray at ISO center (105). The rotating ring gantry (101) generates the stereotactic image of the patient using at least one movable detector (103 and 104) and at least one KV X-ray source (102a and 102b). The first movable detector (104) and the second movable detector (103) capture a full fan mode or a half fan mode of X-ray beam (107) of imaging radiation for small field of view. The full fan mode mode of X-ray beam (107) is captured without moving the first movable detector (104) or the second movable detector (103). The radiotherapy apparatus (100) uses an Oncology Information System (OIS) application to facilitate demarcation of the area of interest during planning of the Computerized Tomography (CT) through contouring prior to treatment of the patient. The radiotherapy apparatus (100) facilitates positioning of the patient, wherein the patient is aligned with the KV X-ray source in 6 degrees of freedom (DOF).
[0028] The present invention discloses the method of positioning the patient in the radiotherapy apparatus (100) to validate the positional accuracy of the patient with respect to the patient planning field during Image guided radiotherapy (IGRT), wherein the method (200) comprises the steps of generating at least one set of Digitally Reconstructed Radiograph (DRR) images of the patient generated with 90 degrees apart using Computerized Tomography (CT) scanning by placing the first movable detector (104) and the second movable detector (103) along with the KV X-ray sources (102a and 102b) placed orthogonally on the rotating ring gantry (101), in step (201). The Computerized Tomography (CT) scanning facilitates generation of orthogonal images of the patient. Subsequently, in step (202), the radiotherapy apparatus (100) facilitates capturing of at least one stereotactic image of the patient using the KV X-ray sources (102a and 102b), wherein the first X-ray beam generated by the first KV X-ray source (102b) and the second X-ray beam generated by the second KV X-ray source (102a) at an angle defined from the Digitally Reconstructed Radiograph (DRR) image.
[0029] Further, in step (203), the stereotactic images captured by the first X-ray beam and the second KV X-ray beam generated by the KV X-ray sources (102a and 102b) are compared with their respective Digitally Reconstructed Radiograph (DRR) images of the patient, and in step (204), the shift between the Digitally Reconstructed Radiograph (DRR) image and the stereotactic image is identified in a two-dimensional plane, in their respective plane of projections. In step (205), the identified shift is transforming into machine coordinates in order to derive the linear shifts in 6 degrees of freedom (DOF) including X, Y and Z plane and rotational shifts in pitch and yaw directions.
[0030] Subsequently, in step (206), the determined linear and rotational shifts are applied to the reference Computerized Tomography (CT) scan and a set of Digitally Reconstructed Radiograph (DRR) containing at least one set of Digitally Reconstructed Radiograph (DRR) images generated with 90 degrees apart by the first movable detector (104) and the second movable detector (103) on either side of the predefined angle of the KV X-Ray tube. Further, in step (207), the set of Digitally Reconstructed Radiograph (DRR) images are compared with the stereotactic images of the patient at various angles, in order to identify the optimal angle to determine the roll shift. In step (208), the shift correction is determined by using at least two images in all 6 Degrees of Freedom (DOF) including X, Y, Z axis in linear direction and pitch, yaw and roll in rotational directions.
[0031] The present invention provides a radiotherapy apparatus with significantly reduced dose received by the patient during the Image Guided Radiotherapy (IGRT) without compromising on the accuracy of positioning in 6 degrees of freedom (DOF). Further, the radiotherapy apparatus enables the healthcare practitioner to perform the Image Guided Radiotherapy (IGRT) in every field of treatment. The radiotherapy apparatus significantly reduces the time taken to set up the patient for treatment and ensures the accuracy in patient positioning in 6 degrees of freedom (DOF) with a minimum dose and in a short interval of time.
[0032] The system facilitates selecting a region of interest to register the patient while planning the Computerized Tomography (CT) in a 3-Dimensional plane, wherein the region of interest is further converted into a 2-Dimensional area on the Digitally Reconstructed Radiograph (DRR) generated prior to treatment. Further, the said region of interest is considered as a reference with respect to the image of the patient acquired during the initiation of the treatment.
[0033] It is to be understood, however, that even though numerous characteristics and advantages of the present invention have been set forth in the foregoing description, together with details of the structure and function of the invention, the disclosure is illustrative only. Changes may be made in the details, especially in matters of shape, size, and arrangement of parts within the principles of the invention to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed.
Reference numbers
Components Reference Numbers
Radiotherapy apparatus 100
Rotating ring gantry 101
Second KV X-ray source 102 a
First KV X-ray source 102 b
Second movable detector 103
First movable detector 104
Iso center 105
LINAC X-ray tube 106
Full fan mode or half fan mode of X-ray beam from the first movable detector for small field of view 107
Full fan mode or half fan mode of X-ray beam from the second movable detector for small field of view 108
, Claims:We Claim:
1. Image guided radiotherapy by in-gantry stereotactic imaging for radiotherapy apparatus, wherein the apparatus (100) comprises:
a. a rotating ring gantry (101) having a central opening to accommodate the body of a patient positioned along the longitudinal axis and extending there through;
b. at least two KV X-ray source including a first KV X-ray source (102b) and a second KV X-ray source (102a) mounted on the rotating ring gantry (101), wherein the first KV X-ray source (102b) and the second KV X-ray source (102a) facilitate generation of a beam of imaging radiation directed towards the patient’s table used for stereotactic imaging;
the apparatus (100), characterized in that, at least one movable detector including:
i. a first movable detector (104) mounted on the rotating ring gantry (101) to detect the beam of imaging radiation after it has passed through the patient table, wherein the first movable detector (104) captures a full fan mode X ray beam (108) of imaging radiation with a small field of view of at least 250*250 mm or a half fan mode X ray beam (108) of imaging radiation with a small field of view of at least 250*450 mm without moving the first movable detector (104);
ii. a second movable detector (103) mounted on the rotating ring gantry (101) to detect the beam of imaging radiation after it has passed through the patient table, wherein the second movable detector (103) captures a full fan mode X ray beam (107) of imaging radiation with a small field of view of at least 250*250 mm or a half fan mode X ray beam (107) of imaging radiation with a small field of view of at least 250*450 mm without moving the second movable detector (103), wherein the full fan mode X ray beam of imaging radiation facilitate head scans and the half-fan mode mode X ray beam facilitate scanning of body parts.
2. The apparatus (100) as claimed in claim 1, wherein the beam of imaging radiation generated by the first KV X-ray source (102b) and the second KV X-ray source (102a) facilitates capturing of at least one stereotactic image of the patient using a minimum dose of radiation.
3. The apparatus (100) as claimed in claim 1, wherein the first movable detector (104) and the second movable detector (103) along with the KV X-ray sources (102a and 102b) facilitates capturing of at least one set of Digitally Reconstructed Radiograph (DRR) image of the patient generated with 90 degrees apart.
4. The apparatus (100) as claimed in claim 1, wherein the apparatus (100) comprises a LINAC (Linear Accelerator) X-ray tube (106) mounted on the rotating ring gantry (101) to produce high energy X-rays for radiation treatment.
5. The apparatus (100) as claimed in claim 1, wherein the first movable detector (104) and the second movable detector (103) are mounted orthogonally to the Linear Accelerator (LINAC) X-ray tube (106) on the rotating ring gantry (101).
6. The apparatus (100) as claimed in claim 1, wherein the method (200) for stereotactic imaging with a smaller field of view in Image guided radiotherapy (IGRT) using the radiotherapy apparatus (100) comprises the steps of:
a. generating at least one set Digitally Reconstructed Radiograph (DRR) image of the patient with 90 degrees apart using Computerized Tomography (CT) scanning by placing the first movable detector (104) and the second movable detector (103) along with the KV X-ray sources (102a and 102b) placed orthogonally on the rotating ring gantry (101);
b. capturing at least one stereotactic image of the patient using the KV X-ray sources (102a and 102b) at an orthogonal angle defined from the Digitally Reconstructed Radiograph (DRR) image;
c. comparing the stereotactic images captured by the first X-ray beam and the second KV X-ray beam generated by the KV X-ray sources (102a and 102b) with their respective Digitally Reconstructed Radiograph (DRR) images of the patient, wherein the time taken to acquire the image and register with the reference image from Computerized Tomography (CT) scanning is in the range of 4-5 seconds;
d. identifying the shift between the Digitally Reconstructed Radiograph (DRR) image and the stereotactic image in a two-dimensional plane, in their respective plane of projections;
e. transforming the identified shift is into machine coordinates in order to derive the shifts in 6 degrees of freedom (DOF) including X, Y and Z plane and rotational shifts in pitch and yaw directions;
f. applying the determined linear and rotational shifts to the reference Computerized Tomography (CT) scan and a set of Digitally Reconstructed Radiograph (DRR) containing at least one Digitally Reconstructed Radiograph (DRR) image generated by the first movable detector (104) and the second movable detector (103) on either side of the predefined angle of the KV X-Ray tube;
g. comparing the set of Digitally Reconstructed Radiograph (DRR) images with the stereotactic images of the patient at various angles to identify the optimal angle to determine the roll shift; and
h. determining the shift correction by using at least two images in all 6 Degrees of Freedom (DOF) including X, Y, Z axis in linear direction and pitch, yaw and roll in rotational directions.

7. The apparatus (100) as claimed in claim 1, wherein the de-markation of the area of interest in the patient’s body in 3-Dimensional mode is converted into 2-Dimensional mode on the Digitally Reconstructed Radiograph (DRR) to achieve optimum results.