Abstract:
Devices and methods are disclosed which relate to the calibration and quality assurance of motion tracking enabled radiation therapy machines. A phantom, capable of mimicking human breathing through inflation and deflation of the lungs, houses an independently moving target (tumor) that detects the amount of radiation received from the radiation therapy machine. This amount can be compared with a desired amount to determine if adjustment or repositioning is necessary. The servo-mechanism(s) of the motion tracking enabled radiation therapy machine(s) are adjusted in comparison of detected versus programmed motion of the respiring phantom having incorporated independently moving target that incorporated radiation dose detector(s). In the invention, motion tracking and irradiation mechanisms of the radiation therapy machine are adjusted to calibrate with reference to performance specifications of the radiation therapy machine.

Description:
This application is a continuation of U.S. patent application Ser. No. 12/957,370, filed Nov. 30, 2010, now U.S. Pat. No. 8,110,811; which is a continuation of U.S. patent application Ser. No. 11/924,712, filed Oct. 26, 2007, now U.S. Pat. No. 7,842,929; the contents of which are hereby incorporated by reference herein in their entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to radiation therapy. More particularly, the present invention relates to the calibration and quality assurance of radiation delivery. 
     2. Background of the Invention 
     Cancer is a group of diseases in which abnormal cells divide without control, often invading other tissues. According to the American Cancer Society, in 2007 in the United States alone there will have been an estimated 1,444,920 new cases of cancer. It is estimated that in that same period 559,650 people will die in the United States due to various forms of cancer. Many forms of treatment are available and continue to be discovered. One of these forms of treatment is radiation therapy which is used, often in combination with other types of treatment, on roughly half of all cancer sufferers. 
     Radiation is often utilized in the treatment of cancer in order to control malignant cells and shrink tumors. Due to its harmful effects, physicians often attempt to limit the radiation to other parts of the body. This is accomplished by focusing the radiation on the tumor itself. However, the radiation field often may include normal tissue around the tumor to allow for uncertainties in the position of the tumor. One cause of these uncertainties is the natural movement of organs in the body which cause the position and shape of the tumor to change. Unfortunately, by increasing the field of the radiation, the normal tissue can also be affected. Radiation to these areas may cause side effects during treatment, in a period of time after the treatment, or cumulative side effects from re-treatment. To avoid this result, shaped radiation beams are often aimed from several angles to intersect at the tumor. Because these beams do not change direction with the movement of the tumor, excess radiation is received in a marginal volume around and including the tumor and its possible spatial deformation and positions. 
     Newer techniques allow for radiation to be aimed such that it follows the movement of the tumor and synchronizes the delivery of the radiation with this movement to limit the excess radiation. The equipment for this process is very complex and even small deviations can have large repercussions. To avoid these deviations, the equipment must frequently be calibrated and the quality of the results must be assured. 
     In radiation protection, or health physics, a phantom is a device that simulates the human body or part of the human body and is used to calibrate or test the calibration of a detector that measures radiation emanating from within the body. Phantoms can be used in the calibration of radiation delivery devices. However, most phantoms do not provide an accurate representation of the movements internal to the human body and the movement of a tumor within the body. Thus, the calibrations of these radiation delivery devices are not as accurate as they might be particularly with regard to the calibration of systems and methods employed and embodied in these devices to track patient, organ, and tumor/target motions. 
     In a living human patient, such motions may not always be predictable, having apparently spontaneous variation in rate, depth, etc., due to complex physiological, somatic, and psychological controls. A phantom that can simulate organ and tumor/target movement within the moving body in a more lifelike manner allows the proper calibration and quality assurance of such radiation delivery devices that track organ, tumor/target, and body motion and consequently and programmatically adjust radiation delivery. Furthermore, the organ, tumor/target, and body motion should include both predictable and spontaneous movements to accurately mimic the s of same of an actual human patient. 
     SUMMARY OF THE INVENTION 
     The present invention is a phantom that has the ability to mimic the breathing of a living patient by inflating and deflating its lungs. The phantom is realistic in physical and radiographical appearance, action, and composition. A computer hosts control software that communicates with a control interface. This control interface communicates with a pneumatic motion controller. The pneumatic motion controller ultimately controls the moving components of the breathing phantom. The patterns of lung inflation and deflation of the breathing phantom are determined by the control software. The software program generates lung inflation and deflation in simulation of life-like breathing patterns including: coughing, sneezing, singletus, holding breath, and hyperventilation. 
     In one exemplary embodiment, the present invention is an apparatus for calibrating a motion-tracking enabled radiation therapy machine comprising a synthetic skin in the shape of a body, a synthetic inflatable lung within the skin, and a controller connected to the lung. The controller inflates and deflates the lung to mimic the respiratory movement of a living patient. 
     In another exemplary embodiment, the present invention is an apparatus for calibrating a motion-tracking enabled radiation therapy machine comprising a body that has substantially similar radiation attenuation properties to that of living tissue, a radiation detector within the body, an inflatable lung within the body, and an inflator attached to the lung, capable of mimicking the respiratory movement of a living patient. 
     In yet another exemplary embodiment, the present invention is a method of calibrating a motion-tracking enabled radiation therapy machine comprising the steps of testing the radiation therapy machine on a phantom, and adjusting the radiation therapy machine based on the results. The phantom is of the type having an inflatable lung with the ability to mimic respiratory movement of a living patient, and containing a moving target which also may contain a type of device that detects and measures radiation dose and spatial dose distribution. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  shows a schematic of a radiation calibration device according to an exemplary embodiment of the present invention. 
         FIG. 2  shows a schematic of a personal computer according to an exemplary embodiment of the present invention. 
         FIG. 3  shows a schematic view of a control interface according to an exemplary embodiment of the present invention. 
         FIG. 4  shows a schematic view of an electro-pneumatic motion controller according to an exemplary embodiment of the present invention. 
         FIG. 5A  shows a schematic view of a breathing phantom according to an exemplary embodiment of the present invention. 
         FIG. 5B  shows a perspective of a breathing phantom according to an exemplary embodiment of the present invention. 
         FIG. 6A  shows a proportional front view of a breathing phantom according to an exemplary embodiment of the present invention. 
         FIG. 6B  shows a proportional side view of a breathing phantom according to an exemplary embodiment of the present invention. 
         FIG. 6C  shows a proportional bottom view of a breathing phantom according to an exemplary embodiment of the present invention. 
         FIG. 7  shows an X-ray of a breathing phantom according to an exemplary embodiment of the present invention. 
         FIG. 8  shows a flow chart for a radiation calibration method according to an exemplary embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The present invention is a phantom that has the ability to mimic the breathing of a living patient by inflating and deflating its lungs. The phantom is realistic in physical and radiographical appearance, action, and composition. An additional and asynchronous motion is provided for by a target incorporated into the respiring device. Another feature is the application of the invention in the calibration of X-ray and infrared systems used in radiation therapy treatment machines to track the radiation beam with the motion of a target, or tumor, within a moving system. The clinical application of radiation is regional and the present invention is designed to mimic the motion of lung, chest-wall, overlying dermis, and the independent motion of a tumor within a lung. In the invention, these motions are programmatically controlled and may be made similar or dissimilar in predictable fashion. In a living human patient, the motion may not always be predictable, having apparently spontaneous variation in rate, depth, etc., due to complex physiological, somatic, and psychological controls. The invention allows for the predictable simulation of such statistical variations under general program control using standard pseudo-random numerical generation. In the field of radiation use for humans, clinical, research, weapons development, and health physics, such a device is called a phantom, alluding to the mannequin nature of the device. Thus, a feature of this invention is a “breathing phantom.” 
     A “phantom”, as used in this disclosure, refers to a device that simulates the human body or part of the human body and is used to calibrate or test the calibration of a radiation therapy machine. A “target”, as used in this disclosure, refers to the physical volume within the phantom that acts as a tumor. The target reacts in the presence of radiation, whether by housing radiation detectors, having radiation sensitive material, etc. A “radiation detector”, as used in this disclosure, is any device or material that gives a user feedback on the amount of radiation it has received. A radiation detector could be an electronic device that sends readouts to a computer, a material that decays or changes colors when exposed to radiation, or anything else capable of determining levels of radiation. 
     The invention is comprised of four interacting, communicating systems. A computer  120  hosts control software that communicates with a control interface  140 . Control interface  140  communicates with a motion controller  160 . Motion controller  160  ultimately controls the moving components of the breathing phantom  180 . The patterns of lung inflation and deflation of the breathing phantom is determined by the control software. 
       FIG. 1  shows a schematic of an exemplary embodiment of the present invention. In this embodiment the control computer  120  contains software ultimately used to create movement in the phantom  180 . This control computer  120  is connected to a control interface  140  by a connection, such as a USB digital connection, and sends signals through this connection. Alternatively, the connection could be made utilizing any standard or purpose-designed computer digital signaling interface that is capable of maintaining data integrity and communication rates appropriate to the connection. The control interface  140  communicates with an electro-pneumatic motion controller  160 , in a feedback control system. This communication includes sending an analog signal to the motion controller  160  in order to create movement in the lungs  183 . The control interface&#39;s communication with the motion controller  160  also includes sending a signal through the motion actuator  186  to control the target  184 . The motion controller  160  provides feedback on the movement of the target  184 . The electro-pneumatic motion controller  160  provides regulated air pressure to the lungs  183  of the breathing phantom  180 . This is accomplished through a conduit  166 , such as an air hose, that is connected to the base of the lungs  183 . The motion controller  160  also provides regulated air pressure to the target motion actuator  186 . This actuator  186  moves the target  184  in a rectilinear motion. In other embodiments, the actuator  186  also moves the target  184  in rotational or asymmetric or random directions. 
       FIG. 2  shows an exemplary embodiment of the control computer. In this embodiment, the operating system  221  controls software  222  on the control computer  220 . This software  222  creates a chest motion waveform  223  and target waveform  224  which will create the desired motions in the phantom. The inputs  225  and outputs  226  allow the control computer  220  to communicate with the control interface. 
     The personal computer control software includes several components. The operating system  221  of the computer is commercially (or otherwise) available software enabling the discrete and integrated logic of an electronic computer circuit and ancillary systems to perform computational and data processing functions. In the present embodiment, common systems software  221  includes MICROSOFT WINDOWS, LINUX (versions of UNIX), and APPLE COMPUTER CORP′S MAC OS, which provide the platform for an engineering and automation development system  222 , such as NATIONAL INSTRUMENTS LABVIEW, in which custom Virtual Instrumentation software is devised for the purpose of automating and controlling the breathing phantom. 
       FIG. 3  shows an exemplary embodiment of the control interface of the present invention. The control interface  340  may be a hardware electronic device that provides signals  344 / 346  representing the temporal pressure waves that translate into motion of the breathing phantom and target subsystem. The control interface  340  translates, with an onboard Digital to Analog (D/A) converter  341 , the programmed digitized waveforms  326  into analog voltage signals. These analog voltage signals  344 / 346  are interpreted within the electro-pneumatic motion controller sub-system and translated into pneumatic pressure patterns applied to the breathing phantom. The control interface  340  generates control signals for each component, target  344  and lung  346 , allowing for independent and uncoupled motion. In practice, these motions will be coupled to simulate a target that is attached to the pleura or chest wall. The control interface  340  provides for the real-time read-back of achieved pressure waveforms from the electro-pneumatic motion controller, allowing servo control. The control interface  340  is realized in an integrated product such as MEASUREMENT COMPUTING CORPORATION, model USB-1208LS, that is comprised of a USB interface (digital Universal Serial Bus standard), digital Input/Output logic, eight channels of Analog to Digital voltage input, and two channels of Digital to Analog conversion for voltage output. The inputs are used to sense and convert signals read-back from the motion controller and the outputs are applied to the motion controller to control pressures applied to the breathing phantom. Analog input and output connections have a range of 0 to 5V direct current. These signals are communicated via standard network cable of Category 5e/6 specification over distances of up to 150 feet. 
       FIG. 4  shows an exemplary embodiment of an electro-pneumatic motion controller of the present invention. This motion controller  460  is generally comprised of an air pump  461 , power supply  462 , target pressure regulator  463 , and chest motion pressure regulator  464 . The motion controller  460  receives signals  444 / 446  from the control interface. Signals are received for both lung control  446  and target control  444 . When these signals  444 / 446  are received, the power supply  462  supplies power to the air pump  461 , chest motion pressure regulator  464 , and target pressure regulator  463 . The air pump  461  produces air which is regulated by the pressure regulators  463 / 464 . The target pressure regulator  463  sends air pressure through a conduit  465 , such as a hose, to the target actuator. The chest motion pressure regulator  464  sends air through a conduit  466 , such as a hose, into the lungs of the phantom. The motion controller  460  sends both target feedback  443  and chest motion feedback  445  to the control interface. 
     In one exemplary embodiment, the electro-pneumatic motion controller  460  is comprised of standard industrial components: a pressurizing air-pump, a 25 Watt, 24 Volt (DC) power supply that powers both electro-pneumatic air pressure regulators for target motion and for lung respiration motion, hose connections communicating pressures controlled by regulators to the breathing phantom target and lung subsystems. The motion controller also has a provision for power inlet from building power at 115 VAC nominal, signal input/output via a Category 5e/6 connector, and pressurized air source ports. 
       FIG. 5A  shows an exemplary embodiment of a breathing phantom according to an exemplary embodiment of the present invention. In this embodiment, the phantom  580  is generally comprised of a torso with a skin  581 , lungs  583 , and a target  584 . A target motion actuator  586  receives air pressure through a hose  565  from the target pressure regulator. This air pressure is converted to linear motion in an actuator rod  585  which is connected to the target  584  and can move the target  584  within the phantom  580 . In other embodiments the air pressure may also be converted to rotational or other desired motion of the actuator rod  585 , allowing the target  584  to rotate or perform other motion in addition to the linear movement. The air pressure from the chest motion pressure regulator travels through a hose  566  and into the base of the lungs  583 . This air pressure allows the lung  583  to be inflated and deflated to simulate breathing motion. 
     In one exemplary embodiment of the breathing phantom, the torso mannequin  580  is comprised of a complex plastic simulation of a humanoid torso including lungs  583 , ribcage/chest-wall bone  582 , skin and sub-dermis  581 , and a target  584  within one lung volume. The target  584  is comprised of a sensor holder. This allows for the measurement of radiation using various measuring tools including but not limited to TLD (thermo-luminescent detectors), radiochromic film(s), and telemetric MOSFET detectors which can be positioned within target assemblies of various geometries. With respect to the target actuator  586 , the target  584  is attached to the end of the linear actuator moving rod  585 . Regulated pressure acts against a return spring to move the target in a nonlinear rate of motion along the axis of the actuator motion. In one embodiment, this is accomplished using an electrically operated linear actuator in which an electrical solenoid acts against a return spring in a similar fashion. 
     Under the programmed application of increasing and decreasing air pressure, the phantom lungs  583  inflate with air and deflate to replicate human lung respiratory function. As the lungs expand and contract, the simulated ribcage bones  582  also move as does the anterior and antero-lateral skin surface  581 . Under the independent programmed application of air pressure to one of several industry standard pneumatic motion actuators  586 , target motion within one phantom lung is accomplished in linear, rotational, or combined motions. In one embodiment, the actuator is an SMC CORPORATION model NCQ8B065-125S linear cylinder with pneumatic extension and spring return. In this embodiment, the target motion is linear. Further embodiments utilize an actuator capable of rotating the target or multiple actuators to accomplish both linear and rotational motion. The materials and composition of the phantom are devised to be a faithful simulation of the physical form of a human thorax and to the radiological image properties, such as plastic or elasto-plastic. The particular type of material to be used in this invention would be apparent to one having ordinary skill in the art after consideration of the present disclosure. 
       FIG. 5B  shows a perspective view of an exemplary embodiment of the breathing phantom. From this view, one can see the skin  581  and sub-dermis. The skin  581  covers the ribcage and chest wall, which house the lungs  583  and target. The air hose  566  can be seen running into the base of the right lung  583 , where it delivers air into the lung. 
       FIG. 6A  shows a proportional front view of an exemplary embodiment of the phantom. In this embodiment, the lungs  683  are a single structure. An air port  667  allows the lungs  683  to be inflated and deflated to simulate human breathing. At the same time, an actuator rod (not shown) inserted through the tumor port  687  allows for a target volume to be moved independent of the rest of the phantom  680 . In this embodiment, the phantom  680  is covered in a synthetic skin  681  which has similar radiation attenuation properties to that of human skin. 
       FIG. 6B  shows a proportional side view of an exemplary embodiment of the phantom. In this embodiment, the ribs  682  are located adjacent to the lungs  683  and above the air port  667  and tumor port  687 . The air port  667  and tumor port  687  are approximately centered with respect to the side of the lungs  683 . 
       FIG. 6C  shows a proportional bottom view of an exemplary embodiment of the phantom. In this embodiment, the tumor port  687  and air port  667  are approximately centered on the bottom of the lungs  683 . The ribs  682  and spinal column  688  allow for a more human like simulation as they will affect the travel of radiation into the phantom  680 . 
       FIG. 7  shows a transmission radiograph x-ray examination of an embodiment of the present invention. This x-ray shows a device that looks similar to a human thorax. A cross-sectional image set using x-ray computed tomography provides the same result. This remains true during programmed motion(s). From the x-ray, one can see the lung volumes  783 , as well as the air port  767  at the bottom of one lung (e.g., right lung) where it connects to the air hose. The springs and metal pieces from the target actuator  786  can be seen towards the bottom of the other lung (e.g., left)  783 . The ribcage  782  and a backbone can be seen as well. 
       FIG. 8  shows a method of using the phantom to calibrate a radiation therapy machine according to one exemplary embodiment. The method first entails loading a breathing phantom  890  onto a radiation therapy machine. Radiation is then delivered  891  to a target within the phantom. This could be accomplished using respiration guided radiation delivery  893  or image guided radiation delivery  892 . During the radiation delivery, the lungs of the phantom inflate and deflate  894 , mimicking the breathing of a human. This will cause movement in the target. However, at this same time, the user can choose whether to independently move the target  895 . During radiation delivery, the radiation therapy machine systems and methods track phantom respiratory and target motions to provide servo-controlled adaptation of radiation delivery to the motion(s). During the radiation delivery and during phantom and target motions, the radiation therapy machine servo mechanisms are adjusted  896  to match the known phantom and target motions and predictions of expected radiation dose measures. If the radiation delivery performance is within performance expectations  897 , the process terminates. If radiation delivery performance specifications are not met, however, the radiation delivery system is re-calibrated  898 . After re-calibration  898 , the sequence of events will start again, with delivery of radiation  891 . 
     The described four component system is but one exemplary embodiment of the breathing phantom invention. Other embodiments would be identifiable by one versed in the field of humanoid simulation for radiological applications and in the allied fields of industrial and laboratory control and automation. 
     The foregoing disclosure of the exemplary embodiments of the present invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Many variations and modifications of the embodiments described herein will be apparent to one of ordinary skill in the art in light of the above disclosure. The scope of the invention is to be defined only by the claims appended hereto, and by their equivalents. 
     Further, in describing representative embodiments of the present invention, the specification may have presented the method and/or process of the present invention as a particular sequence of steps. However, to the extent that the method or process does not rely on the particular order of steps set forth herein, the method or process should not be limited to the particular sequence of steps described. As one of ordinary skill in the art would appreciate, other sequences of steps may be possible. Therefore, the particular order of the steps set forth in the specification should not be construed as limitations on the claims. In addition, the claims directed to the method and/or process of the present invention should not be limited to the performance of their steps in the order written, and one skilled in the art can readily appreciate that the sequences may be varied and still remain within the spirit and scope of the present invention.