Patent Publication Number: US-2010119443-A1

Title: Radiotherapeutic system and method performed by non-invasive and real-time tumor position tracking

Description:
CROSS-REFERENCE TO RELATED PATENT APPLICATION 
     This application claims the benefit of Korean Patent Application No. 10-2008-0111866, filed on Nov. 11, 2008, in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a radiotherapeutic system and method of precisely irradiating radioactive rays to a tumor site of moving internal organs while tracking the tumor site in real time when radiotherapy is performed. 
     The present invention is as a result of research performed as part of the atomic power research and development project of the Ministry of Education, Science, and Technology [Project Number: M20702000001-08N0200-00110, Project title: Medical and Physics Technique Development for Radiotherapy while Tracking Movement of Internal Organs Radioactive Rays] 
     2. Description of the Related Art 
     Modern people living in complicated societies are under a great deal of stress and have irregular eating habits. Thus, it is more difficult to stay in good shape. In particular, vicious tumors, that is, cancer is the leading cause of death for modern people. In today&#39;s society, the number of cancer cases is increasing and thus national-scale solutions to cope with the increasing trend are urgently is needed. Thus, various cancer therapies, in particular, radiotherapy are receiving more attention as possible solutions. 
     In general, tumor radiotherapy is performed to kill a tumor (or cancer) alone by intensely irradiating radioactive rays only to a tumor site while minimizing irradiation to normal tissues surrounding the tumor. 
     However, according to conventional radiotherapy, radioactive rays are irradiated to the entire moving site to kill the tumor of moving internal organs. However, this method has low therapeutic efficiency and also leads to the destruction of normal cells. 
     Meanwhile, the movement of a target site can be preciously tracked by inserting metal or a RF radio frequency coil into the body by surgery. This method, however, causes additional pain and discomfort to patients. 
     These problems may also be solved by indirectly tracking the movement of a tumor while therapy is performed, where the indirect tracking method includes labeling the tissue of a target tumor with a label, photographing the label using a camera, and tracking the movement of the obtained image of the label. 
     However, this method also has a low degree of precision because the tumor site is indirectly tracked, not directly tracked. 
     SUMMARY OF THE INVENTION 
     The present invention provides a radiotherapeutic system and method of irradiating radioactive rays to a tumor while detecting relatively strong radioactive rays emitted from a tumor through which radioactive medical supplies(radiopharmaceutical), which have been used only for diagnosis, are administered and adsorbed to a patient are adsorbed and tracking the position of the tumor in real time. 
     According to an aspect of the present invention, there is provided a radiotherapeutic system including non-invasive and real-time tumor tracking, wherein the radiotherapeutic system includes: a signal detector for detecting radioactive rays emitted from a tumor to which the radioactive medical supply is adsorbed and generating an electrical signal; a signal processor for converting the generated electrical signal into a three-dimensional (3D) coordinate signal; a controller for generating a control signal in conjunction with the 3D coordinate signal output by the signal processor; and a radioactive-ray irradiation device for emitting radioactive rays to the tumor, wherein the amount of the radioactive rays is controlled by the controller. 
     The signal detector may include at least two gamma-ray detectors that are disposed to be perpendicular to each other near the tumor. 
     The radioactive-ray irradiation device may include a multileaf collimator device for emitting radioactive rays in an amount that is continuously controlled by the controller. 
     The multileaf collimator device may include a body that is movable according to the position of the tumor. 
     The radioactive-ray irradiation device may include a switch that is intermittently opened or closed by the controller to irradiate radioactive rays. 
     According to another aspect of the present invention, there is provided a radiotherapeutic method including: injecting a radioactive medical supply to a human body; emitting radioactive rays by a tumor to which the radioactive rays are adsorbed; detecting radioactive rays emitted from the tumor; tracking the position of the tumor using the detected radioactive rays; and irradiating radioactive rays to the tumor while tracking the position of the tumor in real time. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The above and other features and advantages of the present invention will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings in which: 
         FIG. 1  is a schematic view of a radiotherapeutic system including non-invasive and real-time tumor tracking, according to an embodiment of the present invention; 
         FIG. 2  is a schematic diagram for explaining a signal detector; 
         FIGS. 3 through 5  are diagrams for explaining a radioactive-ray irradiation device; and 
         FIG. 6  is a flowchart of a radiotherapeutic method performed by non-invasive and real-time tumor tracking, according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Hereinafter, embodiments of the present invention will be described in detail with reference to the attached drawings. 
       FIG. 1  is a schematic view of a radiotherapeutic system  10  including non-invasive and real-time tumor tracking, according to an embodiment of the present invention,  FIG. 2  is a schematic diagram for explaining a signal detector  20 ,  FIGS. 3 through 5  are diagrams for explaining a radioactive-ray irradiation device  50 , and  FIG. 6  is a flowchart of a radiotherapeutic method performed by non-invasive and real-time tumor tracking, according to an embodiment of the present invention. 
     Referring to  FIGS. 1 through 6 , the radiotherapeutic system  10  including non-invasive and real-time tumor tracking, according to the present embodiment (hereinafter, referred to as “radiotherapeutic system”), includes the signal detector  20 , a signal processor  24 , a controller  25 , and the radioactive-ray irradiation device  50 . 
     In order to operate the radiotherapeutic system  10 , a radioactive medical supply needs to be injected to a human body. The radioactive medical supply is selectively adsorbed to a tumor site in the human body and emits radioactive rays. Since more radioactive medical supply is adsorbed more to a tumor site than to normal cells, the tumor site emits more radioactive rays than normal cells. Examples of the radioactive medical supply include 2-[18F]fluoro-2-deoxy-D-glucose (FDG) and L-[11C-methyl]methionine that is useful for diagnosing cancer, in particular, a brain tumor. Meanwhile, examples of an isotope for proton emission tomography include 18F, 11C, 15O, and 13N. 
     The signal detector  20  detects radioactive rays emitted from a tumor to which the radioactive medical supply is adsorbed and generates an electrical signal. The signal detector  20  may include, for example, a gamma-ray detector  22 . The gamma-ray detector  22  detects radioactive rays emitted from a tumor to which the radioactive medical supply is adsorbed and generates an electrical signal. If the gamma-ray detector  22  has high resolution, a detection time for detecting radioactive rays emitted from the tumor is long. On the other hand, if the gamma-ray detector  22  has low resolution, the detection time for detecting radioactive rays emitted from the tumor is short. Since the objective of the present invention includes irradiating radioactive rays to a tumor while tracking a position of the tumor in real time, the resolution of the gamma-ray detector  22  may be controlled to be as low as possible. Thus, when the resolution of the gamma-ray detector  22  is lowered to a predetermined value or less, radioactive rays emitted from the tumor are detected in real time. Thus, the signal processor  24 , which will be described later, calculates a three-dimensional (3D) position of the tumor using the electrical signal generated by the signal detector  20 . When two or more gamma-ray detectors  22  are used, the gamma-ray detectors  22  are disposed perpendicular to each other near the tumor. Each of the gamma-ray detectors  22  includes a plurality of gamma-ray detection cells that are arranged on the same plane. A gamma-ray detector  22  detects a two-dimensional position of the tumor. Thus, when two gamma-ray detectors  22  are placed perpendicular to each other and the generated electrical signals are mathematically processed, three-dimensional coordinates of the tumor are obtained. 
     The signal processor  24  converts the electrical signal generated by the signal detector  20  into a digital signal by using an analog-to-digital converter (ADC), and then mathematically processes the digital signal to obtain the 3D position of the tumor and outputs the obtained 3D position of the tumor. The signal processor  24  tracks the strongest signal among signals detected by the signal detector  20 . The signal processor  24  generates a signal indicating the image of the tumor obtained by Anger Logic, which is a conventionally known image process algorithm. Since the reproduction of an image by converting an analog signal (electrical signal) input to the signal processor  24  into a digital signal is easily performed using a known signal process technique, detailed description thereof will not be presented herein. The position of the tumor may be tracked in real time by tracking a position of a spot emitting the strongest signal in images generated by the signal processor  24 . 
     The controller  25  controls the radioactive-ray irradiation device  50  according to the position of the tumor, which is calculated and processed by the signal processor  24  so that radioactive rays are irradiated to the tumor while the radioactive-ray irradiation device  50  tracks the tumor in real time. That is, the controller  25  generates a control signal in conjunction with a coordinate signal output by the signal processor  24 . Since the controller  25  is easily embodied with a known electronical engineering technique, the detailed description thereof will not be presented herein. 
     The irradiation dose of radioactive rays irradiated to the tumor by the radioactive-ray irradiation device  50  is controlled by the controller  25 . The radioactive-ray irradiation device  50  irradiates therapeutic radioactive rays to a target site in a patient. The radioactive-ray irradiation device  50  is a device that generates radioactive rays by accelerating electrons or particles and irradiates the generated radioactive rays, which is well known in physics and medical fields. Thus, the structure and principal of the radioactive-ray irradiation device  50  will not be described in detail. 
     The radioactive-ray irradiation device  50  includes a control device that directly controls irradiation of radioactive rays to the tumor. The control device may be a multileaf collimator device  40  illustrated in  FIG. 4  or a switch  70  illustrated in  FIG. 5 . Referring to  FIG. 4 , the multileaf collimator device  40  may include a multileaf collimator  363  that includes individual ‘leaves’ each having a flat form and a radioactive-ray permeable portion having the same shape as the target site. The multileaf collimator device  40  is installed in the radioactive-ray irradiation device  50  such that the multileaf collimator device  40  relatively moves with respect to the radioactive-ray irradiation device  50 . That is, the movement of the multileaf collimator device  40  is controlled by a servo motor, as will be described later, and a control signal for controlling the servo motor is transmitted by the controller  25 . 
       FIG. 3  illustrates the radioactive-ray irradiation device  50  and the multileaf collimator device  40  installed in the radioactive-ray irradiation device  50 .  FIG. 4  illustrates the multileaf collimator device  40  in more detail than in  FIG. 3 . Referring to  FIG. 4 , the multileaf collimator device  40  includes a body  32 , a sliding member  34 , a frame  36 , a first servo motor  323 , and a second servo motor  341 . 
     The body  32  is fixed with respect to the radioactive-ray irradiation device  50 . The body  32  includes a first through-hole (not shown). The first through-hole is disposed in a pathway of high-energy radioactive rays that are accelerated and moved toward the target site in the radioactive-ray irradiation device  50 . Two guide rails  321  are mounted on the body  32 . The body  32  may include metal such as carbon steel or aluminum alloys. However, the body  32  may also include materials other than metal, and may include any material that allows the body  32  to support the frame  36  as will be described later. The first servo motor  323  may be installed on the body  32 . 
     The sliding member  34  is installed such that the sliding member  34  is movable with respect to the body  32  in one direction. The sliding member  34  is, as illustrated in  FIG. 4 , installed such that the sliding member  34  is able to slide with respect to the body  32  along the guide rail  321  on the body  32  in a first direction X. The sliding member  34  may include a second through-hole (not shown) corresponding to the first through-hole of the body  32 . In the present embodiment, the sliding member  34  is connected to the first servo motor  323  by a ball screw  325  and a ball nut  365 , which are widely used to transform rotational motion to linear motion, such that the first servo motor  323  provides power to the sliding member  34 . That is, the ball screw  325  is fixed to an output shaft of the first servo motor  323 , and the ball nut  365 , which is screw-coupled to the ball screw  325 , is fixed to the sliding member  34 . Thus, when the first servo motor  323  rotates, the ball screw  325  rotates and thus, the sliding member  34  fixed to the ball nut  365  slides in the first direction X. Meanwhile, instead of the ball screw  325  and the ball nut  365 , a rack and a pinion may also be used. 
     The second servo motor  341  is disposed to be perpendicular to the first servo motor  323  and is fixed to the sliding member  34 . 
     The frame  36  is, as illustrated in  FIG. 4 , installed such that the frame  36  is able to slide with respect to the sliding member  34  along guide rails  331  in a second direction Y. The frame  36  may include a through-hole  361  through which radioactive rays irradiated by the radioactive-ray irradiation device  50  pass. The through-hole  361  may be located to correspond to the first through-hole. The through-hole  361  is defined by the multileaf collimator  363 . The multileaf collimator  363  is constructed using individual leaves that are able to slide with respect to each other, thereby forming a corrugated structure. Also, the multileaf collimator  363  is able to slide with respect to the frame  36 . The frame  36  has an open surface so that an end of the multileaf collimator  363  is pushed or pulled. The multileaf collimator  363  may include carbon steel or a tungsten alloy, each of which is capable of shielding radioactive rays so that the radioactive rays irradiated by the radioactive-ray irradiation device  50  are allowed or not allowed to pass through according to need. The multileaf collimator  363  may be manually manipulated. Meanwhile, the multileaf collimator device  40  may further include a template  465  for setting the shape of a region through which radioactive rays pass and which is determined by the shape of the opening of the multileaf collimator  363 . The template  465  may include an acrylic material. Various templates  465  having shapes corresponding to the shape of the target site of a patient may be manufactured in advance. In a state in which the multileaf collimator  363  is manipulated to have the through-hole  361 , the template  465  is disposed on the through-hole  361  and then, a sliding manipulation is performed such that the multileaf collimator  363  only opens a portion of the through-hole  361  corresponding to the template  465  while shielding the other portion of the through-hole  361 . Thus, radioactive rays pass through in the shape of the template  465  corresponding to the target site of a patient. 
     The first direction X is perpendicular to the second direction Y. Thus, the frame  36  is disposed such that the frame  36  two-dimensionally moves on the sliding member  34  with respect to the body  32 . The frame  36  is connected to the second servo motor  341  such that the second servo motor  341  provides power to the frame  36 , and according to the present embodiment, like the sliding member  34  and the first servo motor  323 , the frame  36  is connected to the second servo motor  341  by a ball screw  326  and a ball nut  367  such that the second servo motor  341  provides power to the frame  36 . 
     The controller  25  generates a signal for controlling driving of the first servo motor  323  and the second servo motor  341 . The controller  25  is electrically connected to the first servo motor  323  and the second servo motor  341  through an electrical wire. The controller  25  receives from the signal processor  24  position data according to the movement of a tumor and then based on the position data, generates a signal for controlling driving of the first servo motor  323  and the second servo motor  341  so that radioactive rays are continuously irradiated to the target site while the multileaf collimator  363  follows the tumor. Thus, in the multileaf collimator device  40 , the body  36  moves according to the position of the tumor. 
     Meanwhile, like an opening and closing driver disclosed in Korean Registration Patent Publication No. 0740430, the switch  70  illustrated in  FIG. 5  may be used instead of the multileaf collimator device  40 . Referring to Korean Registration Patent Publication No. 0740430, the switch  70  is installed in the radioactive-ray irradiation device  50  in such a manner as illustrated in  FIG. 5  so that the switch  70  is intermittently opened or closed by the controller  25  to irradiate radioactive rays. 
     As described above, the radioactive-ray irradiation device  50  includes the multileaf collimator device  40  or the switch  70 , each of which controls the irradiation dose of radioactive rays irradiated to the tumor by the radioactive-ray irradiation device  50 . 
     As described above, in the radiotherapeutic system  10 , a radioactive medical supply injected in a human body is adsorbed to a tumor, radioactive rays emitted from the tumor are detected by the signal detector  20 , and then the signal processor  24 , the controller  25 , and the radioactive-ray irradiation device  50  sequentially operate to precisely irradiate radioactive rays to the tumor. In particular, the radiotherapeutic system  10  is characterized in that a tumor is treated while the position of the tumor is tracked in real time. In addition, unlike conventional tumor tracking methods, the radiotherapeutic system  10  uses non-invasive tumor tracking without additional pain and discomfort. 
     A tumor radiotherapy using the radiotherapeutic system  10  including non-invasive and real-time tumor tracking will be described. 
     The tumor radiotherapy sequentially includes a first operation (S 1 ), a second operation (S 2 ), a third operation (S 3 ), a fourth operation (S 4 ), and a fifth operation (S 5 ). 
     In the first operation (S 1 ), a radioactive medical supply is provided to the body of a patient by injection. 
     In the second operation (S 2 ), the radioactive medical supply is adsorbed to a tumor and radioactive rays are emitted therefrom. From the time when radioactive rays are emitted, the radiotherapeutic system  10  is used. In the third operation (S 3 ), the signal processor  24  of the radiotherapeutic system  10  detects radioactive rays emitted from the tumor. The gamma-ray detectors  22  installed in the signal detector  20  are disposed to be perpendicular to each other and generate an electrical signal for calculating 3D position data of the tumor. 
     In the fourth operation (S 4 ), the position of the tumor is tracked using the radioactive rays detected in the third operation (S 3 ). That is, the signal processor  24  converts an electrical signal generated by the signal detector  20  into a digital signal by using an ADC, and then mathematically processes the digital signal to obtain 3D position data of the tumor. As described above, the connection between the signal detector  20  and the signal processor  24  enables real-time tracking of the position of the tumor. In the fifth operation (S 5 ), while tracking the position of the tumor obtained in the fourth operation (S 4 ), radioactive rays are irradiated to the tumor in real time. In the fifth operation (S 5 ), an accurate irradiation dose of radioactive rays are irradiated to the tumor while the multileaf collimator device  40  of the radioactive-ray irradiation device  50  moves according to the position of the tumor in response to a control signal of the controller  25 . 
     As described above, a radiotherapeutic system and method according to embodiments of the present invention provide tumor radiotherapy that is performed while tracking the position of a tumor in the body of a patient in real time without additional pain and discomfort. 
     Although according to the present embodiment, the signal detector  20  includes two gamma-ray detectors disposed to be perpendicular to each other near the tumor, three or more gamma-ray detectors may also be used. 
     Although according to the present embodiment, the radioactive-ray irradiation device  50  includes the multileaf collimator device  40  that through the controller  25  continuously controls the irradiation dose of radioactive rays, other devices, such as the switch  70  illustrated in  FIG. 5 , which controls the radiation dose of radioactive rays may also be used instead of the multileaf collimator device  40 . 
     Although according to the present embodiment, the multileaf collimator device  40  includes the body  32  that is movable according to the position of the tumor, a bed on which a patient lies is moved while the body  32  is fixed. 
     A radiotherapeutic system and method which are performed by non-invasive and real-time tumor tracking, according to embodiments of the present invention, are non-invasive so that a patient does not suffer from additional pain and discomfort, and uses real-time tracking according to the position of the tumor. In addition, according to the radiotherapeutic system and method, the position of the tumor is directly tracked in real time and thus radiotherapy can be precisely performed on the tumor. 
     While the present invention has been particularly shown and described with reference to exemplary embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the present invention as defined by the following claims.