Abstract:
A system and method of evaluating dose delivered by a radiation therapy system using a marker that indicates motion. The marker is associated with the patient. In one method of operation, the method includes delivering radiation to the patient, monitoring motion of the marker during the delivering radiation, and evaluating a dose delivered to the patient based at least in part on the motion of the marker. In another method of operation, the method includes delivering radiation to the patient, obtaining information relating to the delivery of radiation, estimating dose to the marker based at least in part on the information, acquiring dose received by the marker, and comparing the received dose with the estimated dose.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of U.S. Provisional Patent Application No. 60/701,588; titled SYSTEM AND METHOD OF DETERMINING POSITION OF AN OBJECT AND DELIVERING RADIATION THERAPY TREATMENT; filed on Jul. 22, 2005; and the benefit of U.S. Provisional Patent Application No. 60/701,580; filed Jul. 22, 2005; titled SYSTEM AND METHOD FOR FEEDBACK GUIDED QUALITY ASSURANCE AND ADAPTATIONS TO RADIATION THERAPY TREATMENT; both of which are incorporated herein by reference. 
     
    
     BACKGROUND  
       [0002]     Over the past decades, improvements in computers and networking, radiation therapy treatment planning software, and medical imaging modalities (CT, MRI, US, and PET) have been incorporated into radiation therapy practice. Often, devices are used to track the motion and position of the equipment that is used to deliver a treatment. The amount of radiation that is delivered to a patient during a treatment is also monitored in order to deliver the correct dose (e.g., amount of radiation) to the appropriate target treatment area. Typically, equipment and patient position information is gathered via mechanical sensors that are hard-wired to control computers.  
       SUMMARY  
       [0003]     In one embodiment, the invention provides a local positioning system (“LPS”), to control, verify, synchronize, and/or QA radiation therapy treatment systems or imaging device systems. This can be done in real-time or as a post-process. An aspect of the invention includes an interface between the LPS and other positioning systems, and the use of this information for machine control, synchronization, and/or patient procedures, such as imaging or therapy. In another aspect, the LPS can communicate with other patient monitoring devices to acquire information to use for machine control, synchronization, and/or patient procedures.  
         [0004]     Another embodiment of the invention includes a method for tracking different hardware components in the context of patient imaging or treatment. These components can include gantries, couches, collimators (both the base and/or individual leaves) or other components for which feedback is desired. Sensors for this system could also be affixed to patients.  
         [0005]     One method of positioning feedback utilizes mechanical sensors that are typically hard-wired to control computers. Other methods of feedback focus on patient monitoring, and these include implantable RF devices that can be inserted into the patient. Some of these devices use MOSFET technology to provide feedback on dose received, while others provide readout of location.  
         [0006]     In another embodiment, the invention provides a radiation imaging and/or therapy-treatment system. The system comprises a radiation source, a movable apparatus, a controller configured to control, including moving, the movable apparatus, and a local positioning system. The local position system includes a position verification device directly coupled to the movable apparatus and a system monitoring module in communication with the position verification device. The local positioning system is configured to determine position data for the position verification device.  
         [0007]     In another embodiment, the invention provides a method of evaluating dose delivered by a radiation therapy system using a marker that indicates motion. The marker is associated with the patient. The method comprises the acts of delivering radiation to the patient, monitoring motion of the marker during the delivering radiation, and evaluating a dose delivered to the patient based at least in part on the motion of the marker.  
         [0008]     In another embodiment, the invention provides a method of evaluating dose delivered by a radiation therapy system using a marker associated with the patient. The method comprises the acts of delivering radiation to the patient, obtaining information relating to the delivery of radiation, estimating dose to the marker based at least in part on the information, acquiring dose received by the marker, and comparing the received dose with the estimated dose.  
         [0009]     In another embodiment, the invention proves a method of evaluating dose delivered by a radiation therapy system using a marker that indicates motion. The marker is associated with the patient. The method comprises the acts of delivering radiation to the patient, monitoring motion of the marker during the delivering radiation, estimating a dose delivered to the patient based at least in part on the motion of the marker, acquiring dose received by the marker, and comparing the received dose with the estimated dose.  
         [0010]     Other aspects of the invention will become apparent by consideration of the detailed description and accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a partial perspective view, partial schematic illustration of a radiation therapy treatment system according to one embodiment of the invention.  
         [0012]      FIG. 2  is a partial perspective view, partial schematic illustration of a multi-leaf collimator that can be used in the radiation therapy treatment system illustrated in  FIG. 1 .  
         [0013]      FIG. 3  schematically illustrates a local positioning system according to one embodiment of the invention and incorporated with the radiation therapy treatment system of  FIG. 1 .  
         [0014]      FIG. 4  is a block diagram of a plurality of devices that can be used in the local positioning system of  FIG. 3 .  
         [0015]      FIG. 5  is a flow chart of a method of delivering a radiation therapy treatment that utilizes variable intensity seeds according to one embodiment of the invention.  
         [0016]      FIG. 6  is a flow chart of a method of utilizing feedback from a MOSFET type marker implanted in, or near a target according to one embodiment of the invention. 
     
    
     DETAILED DESCRIPTION  
       [0017]     Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the following drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass both direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.  
         [0018]     Although directional references, such as upper, lower, downward, upward, rearward, bottom, front, rear, etc., may be made herein in describing the drawings, these references are made relative to the drawings (as normally viewed) for convenience. These directions are not intended to be taken literally or limit the invention in any form. In addition, terms such as “first”, “second”, and “third” are used herein for purposes of description and are not intended to indicate or imply relative importance or significance.  
         [0019]     In addition, it should be understood that embodiments of the invention include hardware, software, and electronic components or modules that, for purposes of discussion, may be illustrated and described as if the majority of the components were implemented solely in hardware. However, one of ordinary skill in the art, and based on a reading of this detailed description, would recognize that, in at least one embodiment, the electronic based aspects of the invention may be implemented in software. As such, it should be noted that a plurality of hardware and software based devices, as well as a plurality of different structural components may be utilized to implement the invention. Furthermore, and as described in subsequent paragraphs, the specific mechanical configurations illustrated in the drawings are intended to exemplify embodiments of the invention and that other alternative mechanical configurations are possible.  
         [0020]      FIG. 1  illustrates a radiation therapy treatment system  10  that can provide radiation therapy to a patient  14 . The radiation therapy treatment can include photon-based radiation therapy, brachytherapy, electron beam therapy, proton, neutron, or particle therapy, or other types of treatment therapy. The radiation therapy treatment system  10  includes a radiation therapy device having a gantry  18  controlled by to a gantry controller  20 . Though the gantry  18  shown in the drawings is a ring gantry, i.e., it extends through a full 360° arc to create a complete ring or circle, other types of mounting arrangements may also be employed. For example, a C-type, partial ring gantry, or robotic arm could be used.  
         [0021]     The gantry  18  can support a radiation module, having a radiation source  22  and a linear accelerator  26  operable to generate a beam  30  of photon radiation. The radiation module can also include a modulation device  34  operable to modify or modulate the radiation beam  30 . The modulation device  34  provides the modulation of the radiation beam  30  and directs the radiation beam  30  toward the patient  14 . Specifically, the radiation beam  30  is directed toward a portion of the patient. Broadly speaking, the portion may include the entire body, but is generally smaller than the entire body and can be defined by a two-dimensional area and/or a three-dimensional volume. A portion desired to receive the radiation, which may be referred to as a target or target region (shown as  46 ), is an example of a region of interest. Another type of region of interest is a region at risk. If a portion includes a region at risk, the radiation beam is preferably diverted from the region at risk. The patient  14  may have more than one target region  46  that needs to receive radiation therapy. Such modulation is sometimes referred to as intensity modulated radiation therapy (“IMRT”).  
         [0022]     Other frameworks capable of positioning the radiation module at various rotational and/or axial positions relative to the patient  14  may also be employed. In addition, the radiation source  22  may travel in path that does not follow the shape of the gantry  18 . For example, the radiation source  24  may travel in a non-circular path even though the illustrated gantry  18  is generally circular-shaped.  
         [0023]     In one construction, and illustrated in  FIG. 2 , the modulation device  34  includes a collimation device. The collimation device includes the primary collimator having a set of jaws  39 . The jaws define and adjust the size of an aperture  40  through which the radiation beam  30  may pass. The jaws  39  include an upper jaw and a lower jaw controlled by an actuator  41 . The upper jaw and the lower jaw are moveable to adjust the size of the aperture  40 . The collimation device further includes a multi-leaf collimator (MLC)  38 , which includes a plurality of interlaced leaves  42  operable to move from position to position. The movement of the leaves  42  and jaws  39  can be tracked with positioning devices (as described in greater detail below). It is also noted that the leaves  42  can be moved to a position anywhere between a minimally and maximally-open position. The plurality of interlaced leaves  42  modulates the strength, size, and shape of the radiation beam  30  before the radiation beam  30  reaches the target  46  on the patient  14 . Each of the leaves  42  is independently controlled by an actuator  50 , such as a motor or an air valve so that the leaf  42  can open and close quickly to permit or block the passage of radiation. The actuators  50  can be controlled by a MLC computer and/or controller  54 .  
         [0024]     The radiation therapy treatment system  10  ( FIG. 1 ) can also include a detector  58  (e.g., a kilovoltage or a megavoltage detector) operable to receive a radiation beam from the treatment radiation source  22  or from a separate radiation source. The linear accelerator  26  and the detector  58  can also operate as a computed tomography (“CT”) system to generate CT images of the patient  14 . The linear accelerator  26  emits the radiation beam  30  toward the target  46  in the patient  14 . The CT images can be acquired with a radiation beam  30  that has a fan-shaped geometry, a multi-slice geometry, or a cone-beam geometry. In addition, the CT images can be acquired with the linear accelerator  26  delivering megavoltage energies or kilovoltage energies. The target  46  and surrounding tissues absorb some of the radiation. The detector  58  detects or measures the amount of radiation absorbed by the target  46  and the surrounding tissues. The detector  58  collects the absorption data from different angles as the linear accelerator  26  rotates around and emits radiation toward the patient  14 . The collected absorption data is transmitted to the computer  54  to process the absorption data and to generate cross-sectional images or “slices” of the patient&#39;s body tissues and organs. The images can also illustrate bone, soft tissues and blood vessels.  
         [0025]     The radiation therapy treatment system  10  can also include a patient support, such as a couch  62  (illustrated in  FIG. 1 ), which supports the patient  14 . The couch  62  moves along at least one axis in the x, y, or z directions. In other constructions, the patient support can be a device that is adapted to support any portion of the patient&#39;s body, and is not limited to having to support the entire patient&#39;s body. The system  10  also can include a drive system  66  operable to manipulate the position of the couch  70 . The drive system  66  can be controlled by a couch computer and/or controller  70 . Alternatively, the drive system  66  can be controlled using another computer and/or controller of the treatment system  10 .  
         [0026]     The radiation therapy treatment system  10 , as described above, includes many components and mechanisms (e.g., the couch  62 , the MLC  38 , the gantry  18 , etc.) that can move from one position to another in order to deliver a desired dose (e.g., a predetermined amount of radiation) to the patient  14 . For example, the leaves  42  of the MLC  38  can move in order to modulate the intensity of radiation that is being delivered to the patient  14 . Additionally, the couch  62  can move in order to properly position the target  46 . The motion of each of the components of the treatment system  10 , therefore, can be precisely controlled to deliver the proper dose to the patient  14 . The motions (as well as operations) of the components and mechanisms of the treatment system  10  can be controlled with a plurality of computers and/or controllers (e.g., the gantry controller  20 , the couch controller  70 , the MLC controller  54 , etc.). Other controllers, such as a dose controller  75  (shown in  FIG. 3 ), can also be implemented to deliver the proper dose to the patient  14  during the treatment. The dose controller  75  can receive signals from a plurality of positioning and dose verification devices (as described in greater detail below) in order to determine the proper dose that is to be delivered to the patient  14 .  
         [0027]     Alternatively, a single system computer (not shown) can be used to control the entire treatment system  10 , which incorporates the processes and operations of all of the separate controllers and/or computers.  
         [0028]      FIG. 3  illustrates an embodiment of a LPS  100 , having links to multiple radiation therapy treatment system components, as well as their respective controllers. The LPS  100  can also be used to track the movement of the patient  14  and target  46  (as described with respect to  FIG. 4 ). In other embodiments, the LPS  100  can be implemented in other types of imaging equipment (e.g., CT, MRI, PET, etc.), and is not limited to the radiation therapy treatment system  10  that is shown in  FIG. 1 . In the embodiment shown in  FIG.3 , the LPS  100  includes an integration computer  105 , a system monitoring module  110 , and a plurality of position verification devices  125 .  
         [0029]     Before proceeding further, it should be understood that the plurality of position verification devices  125  may also be referred to herein as the plurality of motion verification devices  125 . As discussed herein, the position verification devices  125  can be used to acquire a velocity (or speed), an acceleration, or a time series for the devices  125 . The position information, velocity information, acceleration information, and time series information can be collectively referred to herein as motion information, hence the possible use of the term “motion verification device” in alternative to “position verification device.” Also as discussed herein, the position verification devices  125  (or motion verification devices  125 ) can be used to monitor radiation to the position verification devices  125 .  
         [0030]     As shown in  FIG. 3 , each of the controllers of the treatment system  10  (e.g., the gantry controller  20 , the couch controller  70 , the MLC controller  54 , the dose controller  75 , etc.) can transmit signals to each of their respective treatment system components in order to control their motion and operation. It should be understood that signals, such as those being received and transmitted in  FIG. 3 , can be sustained with wired and wireless communication components (e.g., a copper wire, a coaxial cable, a radio frequency (“RF”), an infrared (“IR”) signal, a Wi-Fi signal, etc.). The treatment system components also transmit signals to the system monitoring module  110 . Those signals can correspond to the actual position and operation of the components. The system monitoring module  110  can also receive signals from the position verification devices  125 .  
         [0031]     Referring still to  FIG. 3 , the position verification devices  125  of the LPS  100  can be coupled to various components of the treatment system  10 . The position verification devices  125  can be used to gather relative and absolute position data from the components of the treatment system  10 , which can aid in optimizing the delivery of a radiation therapy treatment. For example, a position verification device  125  can be coupled to the couch  62  to provide a position, speed, and/or sag of the couch  62 . As other examples, the position verification devices  125  can be strategically located to detect gantry position, speed, and sag and leaf position and speed.  
         [0032]     The position verification device  125  can also supply position data that is relative to other components, for example, the couch position relative to the gantry position. Similarly, position verification devices  125  can be coupled to various other components (e.g., the leaves  42  of the MLC  38 , the gantry  18 , the linear accelerator  26 , etc) of the treatment system  10  in order to provide other position data. Additionally, in some embodiments, positioning devices and beacons can be coupled to, or implanted in patients  14  to provide patient  14  and target position information (as described in greater detail with respect to  FIG. 4 ).  
         [0033]     In some embodiments, the LPS  100  can also be used to track the speed at which the components of the treatment system  10  are moving. More specifically, the speed of the components can be determined in a variety of methods by using the signals of the position verification devices  125 . In one embodiment, the Doppler Effect is used to track the speed of each of moving components. In another embodiment, a position/time comparison calculation can be completed to determine the speed of each component of the treatment system  10 . For example, the speed with which the linear accelerator  26  moves from one position to another around the gantry  18  can be tracked using the Doppler Effect by tracking a position verification device  125  fixed to the linear accelerator.  
         [0034]     In order to track the position and speed of each of the verification devices  125 , the signals that are received by the system monitoring module  110  are relayed to the integration computer  105 . In some embodiments, the signals that are transmitted to the integration computer  105  from the system monitoring module  110  are relayed directly and without alteration. In other embodiments, the signals that are transmitted from the system monitoring module  110  to the integration computer  105  are modulated or altered prior to being sent. Alternatively, the system monitoring module  110  can be incorporated directly into the integration computer  105 .  
         [0035]     Upon receiving the signals from the system monitoring module  110 , the integration computer  105  can complete the control loop that is created by the LPS  100 , and transmit signals back to each of the plurality of system controllers (i.e., the gantry controller  20 , the couch controller  70 , the MLC controller  54 , the dose controller  75 , etc.). The signals that are transmitted from the integration computer  105  to each of the system controllers can then be used to alter the position and operation of the system components. Therefore, the integration computer  105  can effectively control the entire treatment system  10 .  
         [0036]     In one embodiment, the integration computer  105  of the LPS  100  can be used to compare the signals (e.g., motion signals such as position signals, velocity signals, acceleration signals, etc.) of each of the treatment system components to the signals of the position verification devices  125 . For example, the position signal of a position verification device  125  that is coupled to the couch  62  can be cross-checked with a hard-wired position signal that is transmitted directly from the couch  62 . If the position verification device signal differs from the signal produced by the couch  62 , the integration computer  105  can determine if an alteration to the couch position needs to be made. The integration computer  105  can then transmit a correction signal to the couch controller  70  in order to move the couch  62  to the proper position.  
         [0037]     In another embodiment, the speed of a component can be corrected with the LPS  100  using the integration computer  105 . For example, the speed that is monitored with the position verification devices  125  can be compared to a speed signal that is produced from a hard-wired component of the linear accelerator  26 . If the speed that is monitored with the position verification device  125  differs from that of a hard-wired connection, an alteration to the motion of the linear accelerator  26  can be made using the integration computer  105 .  
         [0038]     The LPS  100 , therefore, can be used to gather a plurality of information from components of the treatment system  10  in order to temporally and spatially monitor and correct the motion of each component using absolute and relative reference points. In doing so, each of the components of the treatment system  10  that are being tracked by the position verification devices  125  can be coordinated and synchronized with each other to deliver the proper dose and treatment to the patient  14 . For example, the couch  62 , the linear accelerator  26 , and the MLC  42  can all be synchronized, and have their motions verified in real-time by the integration computer  105  to deliver a treatment to the patient  14 . Corrections to speed and position of the components of the treatment system  10  can be made as needed.  
         [0039]     In another embodiment, the LPS  100  and/or other object positioning systems can interface and/or communicate with the treatment system  10  to conduct post-processing verification operations. It is noted that patient monitoring devices could also interface and/or communicate with the treatment system  10  to perform post-processing verification operations. After a treatment is completed, the signals of the position verification devices  125  can be reviewed. The hard-wired signals of each of the components of the treatment system  10  can also be reviewed. The signals from the position verification devices  125  can then be compared to the corresponding hard-wired signals. The results of the comparison can be used as a quality assurance check to verify that all of the components of the treatment system  10  have operated correctly. Faulty components and components that need to be replaced can potentially be identified using this comparison.  
         [0040]     The position verification devices  125  (described above) of the LPS  100  are not limited to monitoring mechanical devices and components (i.e., the gantry  18 , the MLC  38 , the couch  62 , etc.). Also, the verification aspects of this invention are not limited to the LPS devices described above. In another embodiment, a plurality of position monitoring devices can be coupled to, or implanted in the patient  14  in order to monitor, detect, and/or alter the dose  115  that is delivered during a treatment.  FIG. 4  illustrates a group  200  of exemplary position devices that can aid in the delivery of a radiation therapy treatment. The position devices can include a reflector marker  205 , a transmitter marker  210 , a variable intensity seed  215 , and a transistor marker  220 . Other types of position devices can include a radio-frequency seed and a variable frequency seed. Each of the position devices included in the group  200  can be incorporated into the LPS  100 . In other embodiments, the position devices  205 - 220  need not be included in the LPS  100 , and can be implemented in a separate, stand-alone monitoring system. Before proceeding further, it should be understood that the term “marker” is used broadly herein to encompass the term seed. For example, the variable intensity seed  215  may also be referred to herein as the variable intensity marker  215 .  
         [0041]     In some embodiments, reflector markers  205  are implanted near the target  46  of a patient  14 , and used as a passive tracking and positioning beacon. The reflector markers  205  can also be positioned in a location that approximates the patient  14  (such as the couch  62 ). When the reflector marker  205  is excited by a trigger source, such as a radiation source, the position of the reflector marker  205  can be used to “localize” the position of the target  46 . In some embodiments, the reflector markers are used in combination with CT imaging prior to, or during radiation treatment. The position data that is gained using the reflector markers  205  can confirm the patient  14  and target  46  locations with respect to the patient&#39;s anatomy. Therefore, the reflector markers can aid in directing the radiation therapy treatment toward the target  46 . The reflector markers  205  can also be implanted in (or positioned near) other areas of the patient  14 . For example, markers  205  can be implanted near an identified region at risk (“RAR”) in order to avoid exposing a particularly vulnerable area to radiation.  
         [0042]     Transmitter markers  210  are another type of localizer, and can be used similarly to the reflector markers  205 . However, the transmitter markers  210  do not require a trigger source to be activated. Therefore, depending on the configuration, the transmitter marker  210  can be located at any time during a treatment (and not only when the patient is being exposed to radiation). Transmitter markers  210  can transmit a variety of signals (e.g., RF, Bluetooth, WiFi, IEEE 802.15.4, and the like), which are received by a corresponding receiver.  
         [0043]     In another embodiment, variable intensity seeds  215  can be used to track both the position of the patient  14  and the dose that is delivered to the patient  14 . For example, an RF localization seed can be configured to produce a specific signal, which corresponds to a certain predetermined dose that is to be delivered to the patient  14 . The configured RF seed can then be implanted into or near the target  46  of the patient  14 . Each time the RF seed is exposed to a radiation treatment, the RF signal that is transmitted from the seed can become weaker. After the entire predetermined dose has been delivered, the seed will stop transmitting signal.  
         [0044]     For radiation treatments that require multiple delivery sessions, the variable intensity seeds  215  can be probed for information prior to every treatment. In doing so, the amount of radiation that has been delivered to the patient prior to that delivery session can be verified. Additionally, the amount of radiation that has been received by the seed  215  can be verified with the amount of radiation that has been delivered by the treatment system  10 . Those values can then be compared, and the operation of the treatment system  10  can be verified. In other embodiments, the seeds  215  can transmit their variable signal using a plurality of other techniques (including wireless and wired connections), such as WiFi, signals included in the IEEE 802.15 family, fiber optic connections, or traditional wire connections. Additionally, the seeds  215  can be varied in alternative ways in order to determine the dose that is delivered to the patient  14 . For example, in some embodiments, the signal that is transmitted from the seeds  215  can increase, or get stronger, according to the amount of radiation that is received.  
         [0045]     In some embodiments, the variable intensity seeds  215  can aid in determining deformation of the target  46  (e.g., how the target  46  reacts to the radiation treatment). For example, the markers, such as the variable intensity seeds  215 , can be used as fiduciary points for deformation calculations. Deformation calculations can be made initially using a CT image, or by tracking the target  46  with one or more markers. An example deformation calculation is described in U.S. Provisional Patent Application No. 60/701,580; filed Jul. 22, 2005; titled SYSTEM AND METHOD FOR FEEDBACK GUIDED QUALITY ASSURANCE AND ADAPTATIONS TO RADIATION THERAPY TREATMENT, the entire content of which is incorporated herein by reference. The deformation of the target  46  can then be compared to the amount of radiation that is delivered to the patient  14 , which can be calculated using the seeds  215 . Radiation treatment strategies may be altered according to the amount of radiation that is received when compared to the amount of deformation that has occurred.  
         [0046]      FIG. 5  illustrates a flow chart of a method of delivering a radiation therapy treatment that utilizes variable intensity seeds  215 . The patient  14  is first registered by the treatment system  10  (block  250 ). To do so, the variable intensity seeds  215  can transmit registration signals that are unique to the patient  14  and the target  46 , which can help ensure that the correct treatment is being delivered. Once registered, the dose that is to be delivered to the patient  14  can be determined (block  255 ). The intensity of the signal that is being transmitted from the seed(s)  215  may be adjusted according to the dose that is determined. The amount of radiation that is delivered in a dose can depend on the patient  14 , the target  46 , and the deformation of the target  46 . After determining the dose that is to be delivered to the patient  14 , the position of the target  46  can be determined (block  260 ). In some embodiments, the signal that is being transmitted from the seed  215  can be used to calculate the position of the target  46 . In other embodiments, markers (such as markers  205  and  210 ) can be used to determine the location of the target  46 . Additionally, the positions of other areas (e.g., the position of the patient&#39;s body on the couch  62 ) can also be tracked, as described above.  
         [0047]     Once the position data has been collected, the predetermined dose can be delivered to the patient  14  (block  265 ). During delivery, the seeds  215  can be used to calculate the dose that is being received by the patient  14  (block  270 ). In some embodiments, the signal that is being transmitted from the seeds  215  is tracked continuously so that the amount of radiation that is being received by the patient can be tracked throughout a treatment. In other embodiments, the signal from the seeds  215  is read or polled at predetermined intervals. In order to verify that the correct dose is being received by the patient, the dose that is being delivered can be compared to the dose that is being received according to the seed  215  (block  275 ). If the amount of radiation that is being received by the patient  14  is relatively equal to the amount of radiation that is being delivered, a determination can be made whether or not to continue the treatment (block  280 ). The treatment can be ended (block  285 ) if the signal from the seed  215  is no longer present. However, if additional treatment is required, the process can return to block  255  in order to determine the proper dose to be delivered to the patient  14 .  
         [0048]     Referring again to block  275 , if the amount of radiation that is being received by the patient  14  is not relatively equal to the amount of radiation that is being delivered by the treatment system  10 , a determination whether or not to continue the treatment can be made (block  290 ). In some embodiments, a difference between the amount of radiation that is delivered to the patient  14  and the amount of radiation that is received by the patient  14  can signal a treatment system malfunction. Such a discrepancy may also be an indication that the improper area is being treated. In such embodiments, the treatment may be terminated (block  295 ). However, in some embodiments, adjustments can be made to alter the dose that is delivered, change position of the components of the treatment system  10 , or change the position of the patient  14  (block  300 ). Such alterations can correct the delivery of the treatment so that the delivery can continue. After adjusting the necessary components, the process can return to block  255  so that the dose calculation can be completed for the subsequent delivery. An example dose calculation is also described in U.S. Provisional Patent Application No. 60/701,580.  
         [0049]     In one embodiment, the process shown in  FIG. 5  can be carried out using the dose controller  75  (illustrated in  FIG. 3 ) that is included in the LPS  100 . In another embodiment, the process shown in  FIG. 5  can be implemented using a separate, stand-alone system. The speed with which the process steps are completed can depend on the capabilities of the system that is completing it. In some embodiments, the process is virtually continually updated so that the treatment system alterations to the dose and delivery can be made during a treatment.  
         [0050]     Referring back to  FIG. 4 , transistor markers  220  can also be used to track the position of the patient  14 , and the dose that is received by the patient  14 . However, unlike the variable intensity seeds  215 , the signal of the transistor markers  220  can be used to monitor the intensity of the dose, as well as the amount of radiation that has been received by the patient. More specifically, the intensity signals from the transistor markers  220  can be compiled to provide an indication of the dose that has been received by the patient  14 .  
         [0051]     In one embodiment, a metal-oxide-semiconductor field effect transistor (“MOSFET”) marker  220 , such as sensors or markers from Sicel Technologies, Inc. in Morrisville, N.C., can be used in combination with other localizer markers (such as markers  205  and  210 ) to aid in the optimized delivery of a dose to the patient  14 . The localizer markers can be used to determine the location and deformation characteristics of the target  46 , and the MOSFET marker  220  can be used to monitor the dose that is being received by the patient  14 . The dose that is received by the patient  14 , and tracked by the MOSFET marker  220 , can then be compared to the dose that is actually delivered from the treatment system  10 . The comparison of doses after a treatment can be used to detect systematic or random errors in treatment, and prepare for future remedial treatments or treatment modification. In other embodiments, the dose can be monitored by the MOSFET marker  220  throughout the treatment in real-time, and alterations can be made to the delivery strategy during the same treatment.  
         [0052]      FIG. 6  illustrates a flow chart of a method of utilizing feedback from a MOSFET type marker  220  implanted in, or near the target  46 . In the embodiment shown in  FIG. 6 , the process is completed in combination with a daily CT scan, which is completed prior to the treatment being delivered. However, in other embodiments, the markers  220  can be used at any time prior to, during, or after the treatment, and in combination with a variety of other treatments (MRI, PET, etc.).  
         [0053]     As shown in  FIG. 6 , the location of the markers  220  is first determined (block  350 ). Other beacons and seeds (e.g., the markers  205 - 215 ) can also be located to provide a complete set of positional data for the patient  14  and target  46 . After locating the markers  205 - 220 , a comparison of their current location can be made to the marker location of past treatments (block  355 ). In doing so, a migration of the marker  220  (if any) can be tracked. The marker  220  may migrate from one location to another due to outside forces or movement of the target  46 . In either case, adjustment may be required if the marker has substantially migrated from one position to another in subsequent treatments. After determining the position of the marker (block  355 ) the dose that has been delivered by the treatment system  10  can be recorded, and the predicted amount of radiation that was actually received by the patient  14  can be calculated (block  360 ). The amount and intensity of radiation that has actually been received by the marker  200  can also be measured (block  365 ).  
         [0054]     The predicted dose calculation (block  360 ) can be compared to the dose that was monitored with the marker  220  (block  365 ) in order to verify that the dose that was received was equal or near to the dose that was delivered (block  370 ). After determining whether or not the treatment that was delivered to the patient  14  was equal to the treatment that was received by the patient  14  (block  370 ) the location of the target  46  can be considered (block  375 ). The conduciveness of a target  46  to be treated by radiation therapy can vary throughout the body. Therefore, in some cases, the amount of radiation that is delivered by the treatment system  10  can be greater than the dose that is received by the target  46 . A report can be generated (block  380 ) that can indicate, based on prior knowledge of a target  46  and past treatments, the dose that should be received by the patient for a particular delivery. The deformation effects that are likely to occur can also be considered. Using the information of the certainty report and the dose data from the marker  220 , the decision can be made whether or not a subsequent treatment is required (block  385 ). Using the markers  220  in this way can improve deformation calculations and validate projected deformation maps. The process ends if subsequent treatments are not needed (block  390 ). If another treatment is needed, the settings of the treatment system  10  can be adjusted (block  395 ) and the process can return to block  360 . The position of the components of the treatment system  10  and the dose that is delivered may need to be adjusted based on the type of treatment, deformation, or patient position.  
         [0055]     Referring back to  FIG. 4 , in another embodiment, a set of markers and seeds of the group  200  can be chosen and used to deliver a treatment to a target  10  that is in motion (e.g., a lung, a digestive tract, etc.). The combination of markers and seeds  205 - 220  that are chosen from the group  200  can be determined according to treatment system  10 , the type of treatment that is being delivered, and the patient  14 .  
         [0056]     In one embodiment, the motion of the target  46  can be tracked using both the group  200  of markers and seeds, as well as with other devices (e.g., fluoroscopy, MVCT, kVCT, and the like). Then, during the delivery of a dose the treatment can be adapted or interrupted depending on the position of the target. For example, the lung of a patient  14  may need to be radiated. Due to the patient&#39;s need to breathe during treatment, the target  46  (i.e., the lung) may be in relatively constant motion. To track the motion of the lung, markers and seeds of the group  200  can be implanted in, or positioned proximate to the lung. The motion of the lung can also be monitored by other devices, such as those listed above. By tracking the motion of the lung the treatment that is being delivered can be adapted to include different doses according to the type of motion that is occurring. More specifically, the dose that is being delivered when the patient is breathing in may be different from the dose that is being delivered when the patient is breathing out. Additionally, the motion of the lung and the treatment that is delivered can be verified by comparing the signals of the markers and seeds of the group  200  to the signals of the other devices. If the results of the comparison are not consistent with each other, an error in treatment or an equipment malfunction can be identified. Erratic behavior of the lung (e.g., couching) can also be identified by the markers and seeds of the group  200  so that treatment can be paused or interrupted until the motion becomes more stable.  
         [0057]     In another embodiment, the entire collection of devices that are used to track the components of the treatment system  10  and the group  200  of seeds and markers can be used to deliver a treatment to the patient  14 . In one such embodiment, the motion of the components of the treatment system  10  and the target  46  are used to provide an optimized treatment using four dimensional, computed tomography (4D CT) images. 4D CT images can refer to a collection of 3D image volumes that each represents a “phase” of a motion pattern, such as breathing. These 4D CT images can be used for contouring, as well as for generating treatment plans that anticipate a certain cycle of phases. However, a patient&#39;s motion pattern can often deviate from the ideally reproducible pattern indicated by a 4D CT image set. The seeds and markers of the group  200  can be used to more accurately calculate dose for each of the volumes by monitoring the motion of the patient and/or system components during treatment. The motion that is tracked using the seeds and markers can be irregular or unexpected, and need not follow a smooth or reproducible trajectory. The position of each of the components of the treatment system  10  can also be verified during delivery. Using the measurements acquired by the various devices, an optimal dose can be recalculated for the patient&#39;s actual motion pattern. In another embodiment, the motion of the patient  14 , the target  46 , and the components of the treatment system  10  can be used to recalculate the dose for each phase of the 4D CT in real-time during a treatment. Deformation monitoring techniques (as described above) could also be used as a parameter to calculate and alter the dose between the different phases. Utilizing all of the data sources available can allow an optimized treatment.  
         [0058]     Thus, the invention provides, among other things, new and useful systems and methods of determining position of an object and delivering radiation therapy treatment. Various features and advantages of the invention are set forth in the following claims.