Abstract:
A system, method, apparatus, and means for delivering treatment fields includes identifying a sequence group. A type of radiation to be applied in a first field of the sequence group is identified. The type of radiation is selected from among primary photon radiation and primary electron radiation. A radiation therapy treatment device is configured, based at least in part on the type of radiation. The first field is then delivered.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
   This application is related to commonly owned U.S. patent application Ser. No. 09/910,526, filed Jul. 20, 2001 for “VERIFICATION OF ELECTRON TREATMENT FIELDS”, and U.S. patent application Ser. No. 09/909,513, filed Jul. 20, 2001, for “REMOVABLE ELECTRON MULTILEAF COLLIMATOR”, the contents of each of which are incorporated by reference in their entirety for all purposes. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   The present invention relates generally to radiation therapy devices, and more particularly, to the automated delivery of radiation therapy. 
   2. Description of the Related Art 
   Conventional radiation therapy typically involves directing a radiation beam at a tumor in a patient to deliver a predetermined dose of therapeutic radiation to the tumor according to an established treatment plan. This is typically accomplished using a radiation therapy device such as the device described in U.S. Pat. No. 5,668,847 issued Sep. 16, 1997 to Hernandez, the contents of which are incorporated herein for all purposes. 
   The radiotherapy treatment of tumors involves three-dimensional treatment volumes which typically include segments of normal, healthy tissue and organs. Healthy tissue and organs are often in the treatment path of the radiation beam. This complicates treatment, because the healthy tissue and organs must be taken into account when delivering a dose of radiation to the tumor. While there is a need to minimize damage to healthy tissue and organs, there is an equally important need to ensure that the tumor receives an adequately high dose of radiation. Cure rates for many tumors are a sensitive function of the dose they receive. Therefore, it is important to closely match the radiation beam&#39;s shape and effects with the shape and volume of the tumor being treated. 
   Both primary photon and primary electron beams may be used in radiation therapy. Accordingly, many existing radiation therapy devices include the ability to generate and deliver both photon and electron beams. Currently, clinical practice requires substantial manual intervention to use conformal electron treatment. Conformal photon fields typically are shaped using one or more collimating devices positioned between the source and the treatment area. Many of these photon beam collimating devices may be positioned automatically to deliver a desired photon field shape to a treatment area on a patient. Little manual intervention is required to administer photon radiation therapy. 
   Primary electrons are currently used on approximately 30% of all patients who undergo radiation therapy. Electron fields delivered via radiation therapy devices are typically shaped using either an off-the-shelf electron applicator (either rectangular or circular in cross-section) or a custom cutout formed of Cerrobend®. Both of these beam shaping methods have limitations. Off-the-shelf electron applicators often unnecessarily irradiate portions of healthy tissue, since they do not precisely conform to the target. Custom cutouts formed of Cerrobend® are highly conformal, but are costly to make, store and require special quality assurance. The Cerrobend® material may also require special handling because of the potentially toxic metals involved. Each of these approaches to electron field shaping also suffer in that they can be inefficient to use. A radiation therapist delivering a prescribed treatment must repeatedly enter the treatment room during treatment to insert the proper cutout for each field in the therapy. This is not only inefficient, but it effectively precludes the delivery of treatments which require electron field modulation in both intensity and energy at a single gantry position. 
   As described in co-pending and commonly assigned U.S. patent application Ser. Nos. 09/910,526, and 09/909,513 (referenced above), Applicants have developed a radiation therapy device, verification approach, and electron collimator which overcome many of these difficulties associated with delivery of both electron and photon beams from a single radiation therapy device. 
   It would be desirable to provide a system and method for automating the delivery of treatment fields. In particular, it would be desirable to provide a system and method of delivering treatment fields in a radiation therapy device having the ability to deliver both primary photon and primary electron fields. 
   SUMMARY OF THE INVENTION 
   To alleviate the problems inherent in the prior art, and to allow the accurate, efficient and effective delivery of photon, electron, and mixed beam radiation therapy, embodiments of the present invention provide a system and method for the automated delivery of treatment fields. 
   According to one embodiment of the present invention, a system, method, apparatus, and means for delivering treatment fields includes identifying a sequence group. A type of radiation to be applied in a first field of the sequence group is identified. The type of radiation is selected from among primary photon radiation and primary electron radiation. A radiation therapy treatment device is configured, based at least in part on the type of radiation. The first field is then delivered. In some embodiments, a determination is made whether the sequence group is to be applied with radiation or not. A sequence without applied radiation may be performed for testing purposes. 
   In some embodiments, a sequence group may include a number of fields. For each field, the type of radiation is identified, the radiation therapy device is configured, and the field is delivered. In some embodiments, configuration of the radiation therapy device includes positioning elements of a photon collimator and elements of an electron collimator. 
   The present invention is not limited to the disclosed preferred embodiments, however, as those skilled in the art can readily adapt the teachings of the present invention to create other embodiments and applications. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The exact nature of this invention, as well as its objects and advantages, will become readily apparent from consideration of the following specification as illustrated in the accompanying drawings, in which like reference numerals designate like parts throughout the figures thereof, and wherein: 
       FIG. 1  is diagram illustrating a radiation therapy device; 
       FIG. 2  is a block diagram illustrating portions of the radiation therapy device of  FIG. 1  according to one embodiment of the present invention; 
       FIG. 3  is a diagram illustrating portions of the radiation therapy device of  FIG. 1  according to one embodiment of the present invention; and 
       FIG. 4  is a flow diagram illustrating an automated process for the delivery of treatment fields using the radiation therapy device of  FIG. 1  according to one embodiment of the present invention. 
   

   DETAILED DESCRIPTION 
   The following description is provided to enable any person skilled in the art to make and use the invention and sets forth the best modes contemplated by the inventor for carrying out the invention. Various modifications, however, will remain readily apparent to those skilled in the art. 
   Turning now to the drawings and, with particular attention to  FIG. 1 , a radiation therapy device  10  pursuant to embodiments of the present invention is shown. According to one embodiment of the present invention, radiation therapy device  10  includes a beam shielding device (not shown) within a treatment head  24 , a control unit in a housing  30  and a treatment unit  32 . An accessory tray  25  is mounted to an exterior of treatment head  24 . Accessory tray  25 , in one embodiment, is configured to receive and securely hold attachments used during the course of treatment planning and treatment (such as, for example, reticles, wedges, or the like). 
   Radiation therapy device  10  includes a gantry  26  which can be swiveled around a horizontal axis of rotation  20  in the course of a therapeutic treatment. Treatment head  24  is fastened to a projection of the gantry  26 . A linear accelerator (not shown) is located inside gantry  26  to generate the high energy radiation required for the therapy. The axis of the radiation bundle emitted from the linear accelerator and the gantry  26  is designated by beam path  12 . Electron, photon or any other detectable radiation can be used for the therapy. Embodiments of the present invention permit the controlled delivery of both primary electron and primary photon beams to a treatment zone  18  during the course of a prescribed treatment. Embodiments of the present invention also permit the automated control of elements of radiation therapy device  10  during testing or quality assurance cycles, allowing the verification of a prescribed course of treatment. 
   During a course of treatment, the radiation beam is trained on treatment zone  18  of an object  22 , for example, a patient who is to be treated and whose tumor lies at the isocenter of the gantry rotation. The plates or leaves of the beam shielding device within the treatment head  24  are substantially impervious to the emitted radiation. The collimator leaves or plates are mounted between the radiation source and the patient in order to delimit (conform) the field. Areas of the body, for example, healthy tissue, are therefore subject to as little radiation as possible and preferably to none at all. The plates or leaves are movable such that the distribution of radiation over the field need not be uniform (one region can be given a higher dose than another). Furthermore, the gantry can be rotated so as to allow different beam angles and radiation distributions without having to move the patient. 
   According to one embodiment of the present invention, several beam shaping devices are used to shape radiation beams directed toward treatment zone  18 . In one embodiment, a photon collimator and an electron collimator are provided. Each of these collimators, as will be described further below, may be separately controlled and positioned to shape beams directed at treatment zone  18 . According to one embodiment, the photon collimator (not shown in  FIG. 1 ) is contained within treatment head  24  and the electron collimator (not shown in  FIG. 1 ) is removably mounted on accessory tray  25 . 
   According to one embodiment of the present invention, radiation therapy device  10  includes a detector  34  which is used, as will be described further below, to perform portal imaging for both photon treatments and electron treatments. Detector  34  may be attached to gantry  26  via an arm structure  35 . In some embodiments, arm structure  35  may be remotely operated by an operator to position detector  34  in a desired position. 
   Detector  34 , in one currently-preferred embodiment, is a flat panel imaging device using solid state amorphous silicon sensors. The RID 1640, offered by PerkinElmer®, Inc. of Fremont Calif., is one suitable device. In one embodiment, the imaging device used as detector  34  is formed with a plurality of detector elements formed in a two dimensional array. In one embodiment, each detector element (or “pixel”) in the array is a solid state sensor, such as a solid state amorphous silicon sensor. Operation of detector  34  may result in the capture of a two dimensional image. In one embodiment, computer  40  and detector control  49  operate to control detector  34  to capture an image and map the signal detected by each of the detector elements to a gray scale value, providing a graphical depiction of the captured image. Preferably, the imaging device used as detector  34  has sufficient sensitivity and dynamic range to detect low signals or amounts of photons. 
   Detector  34  may be attached to gantry  26  via arm structure  35  or in some other manner which allows it to be removably placed under patient  22 . In other embodiments, detector  34  may be permanently attached to table  16 , or movably attached to table  16  such that it may be selectively moved into imaging position as desired. In some embodiments, detector  34  may be used only to verify electron treatment fields. In other embodiments, detector  34  is used to verify both electron and photon treatment fields. 
   Radiation therapy device  10  also includes a central treatment processing or control unit  32  which is typically located apart from radiation therapy device  10 . Radiation therapy device  10  is normally located in a different room to protect the therapist from radiation. Treatment unit  32  includes a processor  40  in communication with an operator console  42  (including one or more visual display units or monitor) and an input device such as a keyboard  44 . Data can be input also through data carriers such as data storage devices or a verification and recording or automatic setup system. More than one control unit  32 , processor  40 , and/or operator console  42  may be provided to control radiation therapy device  10 . 
   Treatment processing unit  32  is typically operated by a therapist who administers actual delivery of radiation treatment as prescribed by an oncologist. Therapist operates treatment processing unit  32  by using keyboard  44  or other input device. The therapist enters data defining the radiation dose to be delivered to the patient, for example, according to the prescription of the oncologist. The program can also be input via another input device, such as a data storage device. Various data can be displayed before and during the treatment on the screen of operator console  42 . According to one embodiment of the present invention, treatment processing unit  32  receives imaging information from detector  34 , allowing the radiation therapist to make any necessary pre-treatment beam or positioning adjustments. 
   Embodiments of the present invention permit the delivery of both primary electron and primary photon beams to treatment zone  18  during the course of a prescribed treatment. Embodiments of the present invention permit the creation and control of both photon and electron radiation beams which closely match the shape and size of treatment zone  18 . Further, embodiments of the present invention permit the verification of both electron and photon treatment fields. 
   Referring now to  FIG. 2 , a block diagram is shown depicting portions of a radiation therapy device  10  and treatment unit  32  according to one embodiment of the present invention. In particular, treatment delivery elements of a radiation therapy device are shown, which may be configured in radiation therapy device  10  and treatment unit  32  as depicted in FIG.  1 . The treatment delivery elements include a computer  40 , operatively coupled to an operator console  42  for receiving operator control inputs and for displaying treatment data to an operator. Operator console  42  is typically operated by a radiation therapist who administers the delivery of a radiation treatment as prescribed by an oncologist. Using operator console  42 , the radiation therapist enters data that defines the radiation to be delivered to a patient. 
   Mass storage device  46  stores data used and generated during the operation of the radiation therapy device including, for example, treatment data as defined by an oncologist for a particular patient. This treatment data is generated, for example, using a treatment planning system  60  which may include manual and computerized inputs to determine a beam shape prior to treatment of a patient. Treatment planning system  60  is typically used to define and simulate a beam shape required to deliver an appropriate therapeutic dose of radiation to treatment zone  18 . 
   Data defining the beam shape and treatment are stored, e.g., in mass storage device  46  for use by computer  40  in delivering treatment. According to one embodiment of the present invention, treatment planning may include activities which occur prior to the delivery of the treatment, such as the generation of treatment data defining a photon treatment, an electron treatment, and/or a mixed beam treatment. Embodiments of the present invention permit the use of mixed beam treatments without the need for extended disruptions to install electron applicators or other shielding devices. Further, embodiments of the present invention permit field shaping of electron beams during a treatment in a device which also permits field shaping of photon beams during a treatment. Embodiments of the present invention also permit the verification of photon, electron, and mixed beams. 
   Mass storage device  46  may also store other information and programs used to operate radiation therapy device  10 . For example, mass storage device  46  may store one or more interlock libraries, each defining one or more interlocks to be used in the operation of radiation therapy device  10  in a particular operation mode (e.g., different interlocks may be used depending on whether the treatment uses primary electrons, primary photons, or mixture of primary electrons and primary photons). 
   Although a single computer  40  is depicted in  FIG. 2 , those skilled in the art will appreciate that the functions described herein may be accomplished using one or more computing devices operating together or independently. Those skilled in the art will also appreciate that any suitable general purpose or specially programmed computer may be used to achieve the functionality described herein. 
   Computer  40  is also operatively coupled to various control units including, for example, a gantry control  44  and a table control  48 . In operation, computer  40  directs the movement of gantry  26  via gantry control  44  and the movement of table  16  via table control  48 . These devices are controlled by computer  40  to place a patient in a proper position to receive treatment from the radiation therapy device. In some embodiments, gantry  26  and/or table  16  may be repositioned during treatment to deliver a prescribed dose of radiation. 
   According to one embodiment of the present invention, computer  40  is operatively coupled to a detector control  49 . Detector control  49  is used to control the operation of detector  34  to perform treatment field verifications pursuant to embodiments of the present invention. Embodiments of the present invention permit the accurate and efficient verification of electron treatment fields, as well as photon and mixed beam fields. The result is a radiation therapy device that allows accurate and verifiable delivery of a wide variety of radiation treatments. In some embodiments, detector control  49  may also be used to control the positioning of detector  34 . In other embodiments, detector  34  may be positioned manually. In one embodiment, computer  40  operates detector control  49  prior to delivery of a planned treatment protocol to allow the verification of a treatment field. 
   According to one embodiment of the present invention, computer  40  and detector control  49  perform processing to enhance or manipulate the image captured by detector  34  (e.g., as described in the co-pending U.S. patent application for “VERIFICATION OF TREATMENT FIELDS” referred to above). As a result, processing performed by computer  40  and detector control  49  may be used to generate a portal image depicting the patient anatomy and the electron collimator field edge. 
   Computer  40  and detector control  49  may also be used to capture multiple electron fields, each of which may be added to each other to depict a relative display of intensity. In such an application, each of the images are compiled separately. Embodiments of the present invention may also be used to capture photon treatment images immediately subsequent to the capture of electron treatment images, thereby allowing the verification of mixed beam treatments. 
   Computer  40  is also operatively coupled to a dose control unit  50  which includes a dosimetry controller and which is designed to control a beam source  52  to generate a desired beam achieving desired isodose curves. Beam source  52  may be one or more of, for example, an electron, and/or photon beam source. Beam source  52  may be used to generate radiation beams in any of a number of ways well-known to those skilled in the art. For example, beam source  52  may include a dose control unit  50  used to control a trigger system generating injector trigger signals fed to an electron gun in a linear accelerator (not shown) to produce en electron beam as output. Beam source  52  is typically used to generate a beam of therapeutic radiation directed along an axis (as shown in  FIG. 1  as item  12 ) toward treatment zone  18  on patient  22 . 
   According to one embodiment of the invention, the beam generated by beam source  52  is shaped using one or more collimator assemblies, depending on the type of beam generated. For example, in one embodiment, a photon beam produced by beam source  52  is shaped by manipulating a photon collimator  64 , while an electron beam produced by beam source  52  is shaped by manipulating an electron collimator  62 . According to one embodiment, photon collimator  64  and electron collimator  62  are multi-leaf collimators having a plurality of individually-movable radiation blocking leaves. The leaves of each such collimator are individually driven by a drive unit  58 ,  59  and are positioned under the control of electron collimator control  54 , photon collimator control  55  and sensor(s)  56  and  57 . 
   Drive units  58 ,  59  move the leaves of each collimator in and out of the treatment field to create a desired field shape for each type of beam. In one embodiment, where an electron beam is to be generated and primary electrons are to be used in a treatment, photon collimator control  55  operates to retract individual leaves of photon collimator  64 , while electron collimator control  54  operates to position individual leaves of electron collimator  62  across the path of the electron beam to generate a desired electron field shape at the isocenter. Similarly, in one embodiment, where a photon beam is to be generated and primary photons are to be used in a treatment, electron collimator control  54  operates to retract individual leaves of electron collimator  62  while photon collimator control  55  operates to position individual leaves of photon collimator  64  across the path of the photon beam to generate a desired photon beam field shape at the isocenter. In other embodiments, both collimators  62 ,  64  may be controlled in concert during the course of a treatment to generate a desired field shape at the isocenter. 
   Referring now to  FIG. 3 , a perspective view of portions of radiation therapy device  10  is shown. In particular,  FIG. 3  depicts portions of treatment head  24  as well as elements along a beam path  12 . According to one embodiment of the present invention, treatment head  24  includes an accessory tray  25  or other mounting device positioned between treatment head  24  and treatment area  18 . Components of a photon collimator (item  64  of  FIG. 2 ) are shown as collimator blocks  90 ,  92  in FIG.  3 . Collimator blocks  90 ,  92  are positioned within treatment head  24  and may include a number of individual elements or “leaves” which may be independently controlled to create a desired field shape at the isocenter. Any of a number of known collimators and shaping devices may be used as photon collimator (item  64  of  FIG. 2 ) in conjunction with embodiments of the present invention. 
   According to one embodiment of the present invention, a separate electron collimator  62  is provided. According to one embodiment of the present invention, components of electron collimator  62  are removably mounted on accessory tray  25 , allowing electron collimator  62  to be quickly installed and removed by radiation therapists or other technicians in order to add or remove electron field shaping capabilities to a radiation therapy device. According to one embodiment, individual leaf beds consisting of a number of individual collimator leaves  70   a-n  are mounted on accessory tray  25  such that they can be moved in a direction  72  across beam path  12 . In one embodiment, the individual leaves  70   a-n  are formed of radiation attenuating materials. For example, brass or tungsten are currently preferred materials, although other materials with similar radiation attenuating characteristics may be used. In one embodiment, individual leaves  70   a-n  have a width of approximately 1-2 cm. Those skilled in the art will recognize that other shapes and sizes of individual leaves  70   a-n  may be selected to produce different field shapes at treatment zone  18 . 
   Collimator drives  58   a-n  and other control circuitry are also removably mounted on accessory tray  25 . In one embodiment, collimator drives  58   a-n  and other control circuitry are mounted on an exterior surface of accessory tray, away from beam path  12 , providing greater durability and length of service for the electrical components used to operate electron collimator  62 . 
   According to one embodiment of the present invention, a container  80  (such as a balloon or the like) filled with helium is positioned along a portion of beam path  12  to reduce the amount of free air along beam path  12 . In one embodiment, container  80  is removably mounted to accessory tray  25 . By replacing some of the air in the air column with helium (or another gas having a low density), the penumbra of the electron beam is reduced, allowing greater control over the shape and effect of the beam at the isocenter. In particular, use of helium along beam path  12  maintains the electron beam spread at a clinically acceptable level by decreasing the number of scattering interactions the electrons experience before they reach treatment zone  18 . In operation, a shaped electron field may be delivered to treatment zone  18  by retracting leaves of photon collimator blocks  90 ,  92 , passing the electron beam through helium-filled container  80 , and selectively shaping the beam by manipulating electron collimator  62 . Multiple fields can thus be delivered to treatment zone  18  during the course of a treatment without manual intervention. Further, embodiments of the present invention support mixed beam treatments by selectively switching between electron and photon beams. According to embodiments of the present invention, manual intervention and equipment set-up is reduced or eliminated. 
   Applicants have found that mounting components of electron collimator  62  on accessory tray  25  provides several desirable benefits. For example, during most types of treatments, electron collimator  62  provides sufficient patient clearance in all gantry and table positions. Further, electronic components, such as collimator drives  58   a-n , will enjoy greater longevity because they are positioned away from beam path  12 . Additionally, greater accuracy is provided during treatment because the overall swing weight of treatment head  24  and accessory tray  25  are minimized. The inventive configuration also enjoys the advantage of allowing ready removal and replacement of components. Accessory tray  25 , in some embodiments, includes one or more accessory slots (not shown) into which components of electron collimator  62  may fit. In some embodiments, components of electron collimator  62  are installed by simply inserting the components into one or more accessory slots of accessory tray  25 . As a result, for treatments that require greater clearance (e.g., such as photon treatments of breast cancer, etc.), components of electron collimator  62  may be readily removed, and then re-installed as needed. 
   Placement of components of electron collimator  62  on accessory tray  25  also serves to reduce the electron penumbra at the isocenter, providing greater accuracy in the delivery of electron treatments. Those skilled in the art will recognize that the electron penumbra can be reduced further by positioning components of electron collimator  62  closer to the isocenter; however, this increases problems with collision. In some embodiments, additional collision detection and avoidance components may be utilized in radiation therapy device  10  to reduce collisions and to allow closer positioning of components of electron collimator  62 . 
   Beam source  52  directs a beam of therapeutic radiation through treatment head and past collimators  62 ,  64  towards treatment zone  18  on patient  22 . According to one embodiment of the present invention, detector  34  may be positioned downstream of patient  22  to perform field verification pursuant to embodiments of the present invention. As described above, embodiments of the present invention permit field verification for both photon and electron beams. When the beam generated by beam source  52  is an electron beam, bremsstrahlung photons are created in treatment head  24 . These photons (represented in  FIG. 3  as item  13 ) pass through patient  22  and are detected by detector  34 . 
   Referring now to  FIG. 4 , a flow diagram is shown depicting one embodiment of an automated process  100  for delivering treatment fields using embodiments of the present invention. This processing may be performed under the control of computer program code stored at, or accessible by, computer  40  of treatment processing unit  32 . The particular arrangement of elements in the flow chart of  FIG. 4  is not meant to imply a fixed order to the steps; embodiments of the present invention can be practiced in any order that is practicable. 
   Processing begins at  102  where equipment, including radiation therapy device  10  and treatment processing unit  32 , are powered on or otherwise enabled for use. Processing continues at  104  where a sequence group is retrieved. According to one embodiment, treatment processing unit  32  may store one or more courses of treatment prescribed for patients by oncologists. These courses of treatment may be stored as one or more sequence groups associated with each patient. This information may be stored at, or accessible to, computer  40 . Processing at  104  may involve data entry by a radiation therapist operating operator console  42  to select a particular sequence group. In some embodiments, a particular sequence group is selected by computer  40  once patient information has been selected or entered. According to embodiments of the present invention, each sequence group may be comprised of primary photon treatments, primary electron treatments, or a mixture of both primary photon and primary electron treatments. 
   Processing continues at  106  where appropriate libraries are retrieved or otherwise identified. Mass storage device  46  (or other devices in communication with computer  40 ) may store or have accessible to it, one or more interlock, or safety libraries which define permissible control sequences for each treatment type (e.g., different interlocks may be defined for primary photon fields that for primary electron fields). Other libraries and/or data files may also be retrieved at  106 , including, for example configuration files defining one or more configurable features of components of radiation therapy device  10 . In one embodiment, appropriate libraries and other data files are selected at  106  based on the sequence group retrieved at  104 . These libraries will be used to configure and control components of radiation therapy device  10  during delivery of each field of the sequence. 
   Processing continues at  108  where the configuration of the radiation therapy device  10  is verified. This processing may include polling various components of radiation therapy device  10  to determine if the device is properly configured for the selected sequence group (e.g., if the sequence group defines one or more electron fields to be delivered, processing at  108  may ensure that an electron collimator is installed in an accessory tray of the radiation therapy device  10 ). If the configuration is not correct, or if there appear to be configuration problems, the operator may be informed at  110  (e.g., by an appropriate display on operator console  42 ). The operator may be directed to correct the configuration problem before processing proceeds. 
   Processing continues at  111  where an instruction of the sequence group retrieved at  104  is loaded for processing. Each sequence group may include one or more individual instructions, each defining radiation fields to be delivered by radiation therapy device  10 . Each instruction may be separately parsed by computer  40  and used to position components of radiation therapy device  10  to deliver the prescribed field. At  111 , the instruction is loaded for processing. 
   Processing continues at  112  where a determination is made whether radiation is to be applied in the delivery of the field defined in the instruction. In some embodiments, sequencing may include one or more fields which do not require the application of radiation. If the field does not require application of radiation, processing continues to  140  where the instruction is carried out without radiation. In some embodiments, a radiation therapist or operator may select to run a sequence, or individual instructions, without radiation. This selection may be identified at  112 . In this manner, embodiments of the present invention may permit a radiation therapist to run through an entire course of treatment without a patient or phantom in place, thereby allowing the radiation therapist to better prepare for an actual treatment. 
   If radiation is not to be applied, processing continues at  140  where the instruction loaded at  111  is used to configure or position components of radiation therapy device  10  (including, for example, the gantry position, the table position, etc.). For example, the instruction loaded at  111  may include positional instructions for each affected controller. At  140  these positional instructions are forwarded to each affected controller and are used to reorient or position the affected components. Processing at  142  includes receiving feedback from each of the controllers and determining whether the components are properly positioned (e.g., within a predetermined tolerance). 
   Processing continues at  144  where a determination is made whether any further instructions are contained within the sequence retrieved at  104 . If further instructions are in the sequence, processing reverts to  111  and the next instruction is loaded for processing. If no further instructions are in the sequence, processing continues to  146  where the treatment is recorded in a quality assurance chart. In one embodiment, data generated and recorded during the course of a non-clinical or test treatment are stored and recorded in a quality assurance chart associated with the patient&#39;s chart. In this manner, radiation therapy device  10  may be operated to run sequence groups for quality assurance testing and measurement before applying the sequence group to the patient. 
   The data generated during the quality assurance testing may be stored in a manner which does not disrupt, overwrite, or modify data in the patient&#39;s chart. In one embodiment, the quality assurance mode may provide the option to rescale the total monitor units of radiation delivered (including the option to set the total monitor units to zero). If a non-zero number of monitor units is selected, embodiments of the present invention redistribute the monitor units to each sequence group and to each field within the group, proportional to the original treatment. Some embodiments of the present invention permit the operator to toggle all gantry and collimator angles and positions to a reference position (e.g., zero) during a quality assurance mode. Applicants have found such a feature useful to measure total dose to a detector placed inside a phantom. 
   If processing at  112  indicated that radiation is to be applied, processing continues at  114  where a determination of the type of radiation to be applied is made. According to embodiments of the present invention, individual instructions of a sequence group may require the application of different types of radiation (e.g., both primary photons and primary electrons may be delivered in a given sequence). If the loaded instruction requires the application of primary photon radiation, processing continues to  116  where data from the loaded instruction is forwarded to control elements of radiation therapy device  10  to cause the controllers to position their respective components. For example, the loaded instruction may include specific positional information for gantry  26 . This positional information may be forwarded from computer  40  to gantry control  44  to cause gantry control  44  to reposition gantry  26  in the desired position for delivery of the field identified by the instruction. Processing at  116  may also include verification that components are properly positioned (e.g., positioned within a desired tolerance). 
   Once each of the affected components has been moved into position (and verified if appropriate), processing continues to  118  where data of the loaded instruction is used to cause the retraction of electron collimator (element  62  of FIG.  2 ). Electron collimator  62  may be fully or partially retracted to avoid disruption of the delivery of the desired photon field. Processing at  118  may also include the verification that electron collimator  62  has been properly retracted. 
   Processing continues at  120  where data of the loaded instruction is used to cause the positioning of photon collimator  64  to form the desired field shape. Processing at  120  may also include the verification that the collimator has been properly positioned. 
   Processing continues at  122  where radiation therapy device  10  is operated to deliver a dose of photon radiation of the desired intensity and duration (as defined by the instruction loaded at  111 ). Processing continues at  124  where some verification or adjustment of the dosage applied at  122  occurs. For example, dosimetry devices and techniques may be used to detect, monitor, and measure the amount of radiation delivered at  122 . In particular, the radiation delivered at  122  is compared to the prescribed dose defined in the loaded instruction from the sequence group retrieved at  104 . In some embodiments, processing at  124  may involve adjusting the dose applied at  122 . 
   Once the prescribed dose for the field has been applied, processing continues at  126  where a determination is made whether any further field(s) are to be delivered (e.g., whether any further instructions of the sequence group remain to be loaded). If so, processing reverts to  111  where the next instruction of the group is loaded. 
   If processing at  114  indicates that electron radiation, rather than photon radiation, is to be delivered in the field defined by the loaded instruction, processing continues to  130 - 138  where processing similar to  116 - 124  occurs, with the exception that photon collimator  64  is partially or fully retracted and electron collimator  62  is moved into a position to properly shape the required field, and a prescribed dose of electron radiation is delivered. 
   If a determination is made at  126  that no further instructions are to be loaded (i.e., all fields of the sequence group retrieved at  104  have been delivered), processing continues at  128  where data generated and recorded during the course of the treatment are stored and recorded in the patient&#39;s chart. In some embodiments, a phantom may be in position during process  100 . In such embodiments, data generated during the treatment are recorded and stored in a quality assurance chart rather than the patient&#39;s chart. 
   Those skilled in the art will appreciate that various adaptations and modifications of the just described preferred embodiments can be configured without departing from the scope and spirit of the invention. Although a preferred embodiment utilizing removable electron collimator components has been described, in one embodiment, the electron collimator components may be mounted in a manner that does not facilitate ready removal. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein.