Abstract:
High intensity x-ray radiation therapy is used in the medical industry to treat tumors. Patients typically receive radiation treatment over a period of time, in which a quality assurance test of the x-ray beam is performed before each treatment. These quality assurance tests are performed by a detection device that receives the x-ray beam and measures the intensity, shape and uniformity of the x-ray beam. The integrated patient positioning and radiation quality assurance system includes recess assemblies into which an x-ray detection device is inserted to fix the location of the x-ray detection device on the board. As a result, the accuracy of the quality assurance test is improved and the set up time is reduced.

Description:
TECHNICAL FIELD 
     This invention relates to radiation therapy, and more particularly this invention relates to a quality assurance device used to calibrate a patient&#39;s radiation treatment dosage. 
     BACKGROUND OF THE INVENTION 
     Radiation therapy is often used in the medical industry as treatment for tumors. Radiation therapy is the process of using high energy x-rays or other energy sources to kill cancer cells and to shrink tumors. 
     In radiation treatment, the radiation beam may be wide with low intensity, resulting in large areas beyond the tumor being exposed to the radiation, or narrowly focused on the tumor with high intensity. For high intensity radiation treatment, the radiation beam is narrowly focused onto the tumor in order to minimize risks to healthy cells. The intensity of the radiation may vary depending on the type and size of the tumor. Therefore, in order to control the patient&#39;s dosage, it is necessary to control the beam&#39;s intensity, shape, and uniformity. 
     Generally, radiation therapy includes multiple treatments over a period of time. In order to maintain control over the dosage, quality assurance tests are performed before each treatment. Because each patient receives multiple treatments over a period of time and each treatment requires a quality assurance test to be performed on the radiation beam prior to exposing the tumor to the radiation, there is a need to maintain repeatability between treatments for each individual patient. 
     Radiation quality assurance tests are performed in the same environment that patients are treated, on patient positioning systems that includes a radiation-transparent board such as Halcyon™ patient positioning systems. Typically, quality assurance tests have been performed by positioning an x-ray detection device, such as the Thebes® and the Double Check Pro® x-ray detection devices sold by Fluke, Inc., into a bracket that is placed at any location onto the board. The table is then moved so that the x-ray detection device is aligned with the beam. At this location the shape, uniformity, and intensity of the beam is calibrated using the x-ray detection device. 
     Once the beam has been calibrated, the x-ray detection device is removed from the table. The patient is then placed on the table, and an attempt is made to position the patient so that the tumor is at the same location on the table at which the x-ray detection device was positioned. However, in order to align the x-ray beam to the tumor, it is necessary to determine the location of the calibration point. Unfortunately, insofar as the x-ray detection device is removed from the table when the patient is placed on the table, it can be difficult to position the patient so the tumor is at the proper location. Furthermore, because the x-ray detection device may be placed at different locations on the board for each calibration, the coordinates of the tumor relative to the calibration point must be calculated during each visit for the same patient. Therefore, it is difficult to ensure repeatability for recurring treatments of each individual patient. Also, the need to recalculate the coordinates of the tumor relative to the calibration point significantly slows the quality assurance process procedures. In addition, there may be less dosage consistency from treatment to treatment because the manual process of recalculating the coordinates of the tumor relative to the calibration point at each visit may result in errors. 
     Therefore, there is a need for a quality assurance system and process that is repeatable for each patient on recurring treatments in order to speed up the process and increase the accuracy of radiation treatments. 
     SUMMARY OF THE INVENTION 
     A quality assurance device used prior to radiation treatment to measure high energy x-rays is integrated with a patient positioning system. The patient positioning system includes at least one recess within a board on which a patient lies when receiving the radiation treatment. The recess is configured to accept an x-ray detection device that is used for quality assurance tests prior to each radiation treatment. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an isometric view of a patient-positioning board that includes a head board positioning system with a cutout showing the recess unit in the first surface of the board. 
         FIG. 2  is a top plan view of the patient positioning board of  FIG. 1  showing one embodiment of a recess in the board for receiving a radiation calibration device. 
         FIG. 3  is a cross sectional view of the patient positioning board, including the recess, taken along the line A-A of  FIG. 2 . 
         FIG. 4  is a top plan view of the first patient positioning board of  FIG. 1  showing another embodiment of a recess in the board for receiving a radiation calibration device. 
         FIG. 5  is a cross sectional view of the patient positioning board, of  FIG. 1 , including the recess, taken along the line A-A of  FIG. 4 . 
         FIG. 6  is an isometric view showing one example of an x-ray detection device that may be used with a patient position board according to various embodiments of the invention. 
         FIG. 7  is a side plan view showing the x-ray detection device of  FIG. 6  located in a recess in the patient positioning board of  FIGS. 4 and 5 . 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments of the present invention are directed toward providing repeatability to a quality assurance system and method for radiation treatment. Certain details are set forth below to provide a sufficient understanding of the invention. However, it will be clear to one skilled in the art that the invention may be practiced without these particular details. 
     A quality assurance radiation treatment system and method according to one embodiment of the invention includes a patient positioning board  10  as shown in  FIG. 1 . The board  10  has an opposing first side and second side  12 ,  14 , respectively, that are substantially parallel with one another. The first side  12  of the board  10  provides a surface for the patient to lie down upon when receiving radiation treatment. The board  10  is made from a radiation-transparent material and is generally metal free in order to minimize scattering of the x-rays. In one embodiment, the board  10  is made from carbon fiber, but it may be made from other translucent materials. In one embodiment, the thickness of the board  10  may be from 0.75 inches to 1.5 inches. In another embodiment, the board  10  is of a preferred thickness of 0.9 inches±0.06 inches. 
     When the patient lies on the first side  12  of the board  10 , the patient may be held in position by a positioning system. In one embodiment, as shown in  FIG. 1 , the positioning system is a head board  18 . In that embodiment a shoulder depression system  16  is used to stabilize the position of the upper body of the patient. In addition, in order to hold the patient&#39;s head in position, a perforated head mask (not shown) may be placed over the patient&#39;s face and attached to the head board  18 . Other positioning systems may be used, such as breast board positioning system, a pelvis board positioning system, or some other patient positioning system. 
     As shown in  FIGS. 2 and 3 , a recess assembly  20  is formed in the first side  12  of the board  10 . Each recess assembly  20  includes a first recess  22  and a second recess  24  each of which is configured to accept an x-ray detection device (not shown in  FIGS. 2 and 3 ). The location of the recess assembly  20  on the board  10  may be at any location on the first side  12  of the board  10 . In one embodiment, the recess assembly  20  is located in the center of the first side  12  of the board  10 . In another embodiment, a plurality of recess assemblies  20  are at different positions on the first side  12  of the board  10  so that a detection device could be placed into any one of the plurality of positions. 
     The first recess  22  holds the detection device in a position so that a detection device is perpendicular with the first side  12  of the board  10 . The second recess  24  holds a detection device in a position so that the detection device is at an angle of 45° with the first side  12  of the board  10 . The location of the first recess  22  relative to the second recess  24  may be of a variety of different configurations. In the embodiment shown in  FIGS. 2 and 3 , the first recess  22  is adjacent to the second recess  24 . In another embodiment shown in  FIGS. 4 and 5 , the first recess  22  is positioned at a distance from the second recess  24 . Although only two configurations are shown, many other configurations may be used. 
     As shown in  FIG. 4 , the first recess  22  is defined by first and second opposing long sides  26 ,  28 , respectively, and first and second opposing short sides  30 ,  32 , respectively. The first long side  26  is substantially parallel with the second long side  28 , and the first short side  30  is substantially parallel with the second short side  32 . In addition, the first and second long sides  26 ,  28  are substantially at right angles with the first and second short sides  30 ,  32 . In one embodiment, each recess  22 ,  24  extends into the board  10  to a depth less than the thickness of the board. The base of the recess  42  is shown in  FIG. 5  as being flat; however, the base can be configured to other shapes, such as curved. 
     Similarly, the second recess  24  of the recess unit  20  is defined by a first and second opposing long side  34 ,  36 , respectively, and a first and second opposing short side  38 ,  40 , respectively. The first long side  34  is substantially parallel with the second long side  36 , and the first short side  38  is substantially parallel with the second short side  40 . In addition, the first and second long sides  34 ,  36  are substantially at right angles with the first and second short sides  38 ,  40 . The first and second long side  34 ,  36  and the first and second short side  38 ,  40  extend into the board  10  at approximately a 45° angle measured from the first side  12  of the board  10  to a depth less than the thickness of the board. The base of the recess  44 , as shown in  FIG. 5 , may be at an angle of 45° or less with the first side  12  of the board  10 , parallel with the first side  12  of the board  10 , concave in shape, or any other configuration. 
     The recess unit  20  is configured to accept a variety of different types of x-ray detection devices. The detection device may be fully integrated, including a sensor and a display panel, it may be wireless in which signals corresponding to measurements are transmitted to a remote device, or it may have some other configuration. Furthermore, the detection device may measure radiation in one or two dimensions.  FIG. 6  shows a generic fully integrated detection device  50  that measures radiation in two dimensions. The detection device  50  includes a base  52 , a top  54 , a sensor  56  that intercepts the x-ray beam, and a display  58  that indicates the output. However, many other detection devices may be used. Example detection devices  50  include the previously-mentioned Thebes® device, which measures the beam linearly, the previously-mentioned Double Check Pro® Daily Check Device, and a INRTLog 2D Array, which is also available from Fluke, Inc., which measures the beam in a two dimensional array. However, many other types of radiation detection devices may be used. 
     As shown in  FIG. 7 , the x-ray detection device  50  is placed into a recess  22  with the top  54  of the detection device  50  extending into the recess  22 . The detection device  50  rests in the recess  22  so that the sensors  56  are generally aligned with the surface of the board  10 . Once the x-ray detection device  50  is in position, it may be used to calibrate an x-ray beam. In one embodiment, the detection device  50  contains a sensor  56  made up of an ion chamber; however other detection devices  50  may use different types of sensors. Generally, the detection device  50  measures the x-ray beam&#39;s intensity, shape, uniformity, consistency, flatness, and/or total dosage; however, many other measurements may be obtained. 
     The detection devices  50  may measure the beam linearly or in two dimensions. A linear detection device  50  measures the beam intensity at multiple locations. When a linear detection device  50  is placed horizontally with the board  10 , the detection device  50  measures the beam intensity linearly in the XY plane as shown in  FIG. 2 . When a linear detection device  50  is placed in first recess  22 , the detection device  50  measures the beam intensity in the Z direction. Correspondingly, when a linear detection device  50  is placed in the second recess  24 , the detection device  50  measures the beam intensity linearly in the XZ plane. 
     A two dimensional detection device  50  measures the beam intensity at multiple locations in a two dimensional array. When the two dimensional detection device  50  is placed horizontal with the board  10 , the detection device  50  measures in the XY plane in both the X and Y direction. When the two dimensional detection device  50  is placed in the first recess  22 , the detection device  50  measures the beam intensity in the XZ plane in both the X and Z direction. Correspondingly, when the two dimensional detection device  50  is placed in the second recess  24 , the two dimensional detection device  50  measures in the XZ and YZ plane. 
     The detection device  50  uses each point measured on a particular plane, such as the XY plane, to calculate beam intensity, shape and uniformity. It is reasonably known in the art that uniformity remains fairly constant in parallel planes. Therefore, once multiple measurements have been made in a first plane, such as XY, only one measurement point is needed in a second parallel plane in the Z direction. From the measurements of a first XY plane and each individual measurement in a parallel plane in the Z direction, the uniformity in each parallel plane can be calculated. For example, if two measurements on the XY plane are XY 1 =1 and XY 2 =2, and a measurement on a second parallel plane in the Z direction is XYZ 1 =3, wherein XYZ 1  is a point parallel to XY 1 , then XYZ 2 =6, wherein XYZ 2  is a point parallel to XY 2 . Each point on the second parallel plane may be calculated to determine the uniformity on that plane. Based on the measurements taken, the beam is calibrated to the desired parameters. 
     Once the quality assurance test has been completed, the patient is placed onto the first side  12  of the board  10  in the appropriate positioning system. After the patient is secured into their position, the board  10  is moved to align the x-ray beam with the patient&#39;s tumor. Because the detection device is integrated into the board, the location of the beam during the quality assurance test is already predetermined. Typically, each patient receives repeated radiation treatments. Because the quality assurance tests are generally conducted at a fixed location and the tumor generally remains at a fixed location, the coordinates of the patient&#39;s tumor relative to the test location remains relatively constant. Therefore, for each patient receiving multiple treatments, the coordinates of the tumor relative to the quality assurance test location will generally only need to be calculated for the first treatment. Consequently, the test set up time is minimized for each subsequent treatment after the first treatment, and the repeatability between each treatment results in higher accuracy from treatment to treatment. 
     Although the present invention has been described with reference to the disclosed embodiments, persons skilled in the art will recognize that changes may be made in form and detail without departing from the spirit and scope of the invention. Such modifications are well within the skill of those ordinarily skilled in the art. Accordingly, the invention is not limited except as by the appended claims.