(12) United States Patent
`Whitham
`
`(10) Patent No.:
`(45) Date of Patent:
`
`US 6,445,766 B1
`Sep. 3, 2002
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`US006445766131
`
`(54) SYSTEM AND METHOD FOR IMPROVED
`DIAGNOSTIC IMAGING IN A RADIATION
`TREATMENT SYSTEM
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`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`(75)
`
`Inventor: Kenneth Whitham, Alamo, CA (US)
`
`9.-“I991 Hernandez etal.
`5.046.078 A *
`5,471,516 A * ll,-"1995 Nunan
`5.757.881 A *
`5,-“I998 Hughes
`
`....... ., 378’ll9
`378765
`378,/‘b5
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`(73) Assignee: Siemens Medical Solutions USA, Inc.,
`Iselin, NJ (US)
`
`( * ) Notice:
`
`Subject to any disclaimer, the term of this
`patent is extended or adjusted under 35
`U.S.C. l54(b) by 0 days.
`
`* cited by examiner
`
`Primary Examirter—Robert II. Kim
`Assistnr-it Exr1mt'ner—Hoon K. Song
`
`(57)
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`ABSTRACT
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`(21) Appl. No.: 09/693,702
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`(22)
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`Filed:
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`Oct. 18, 2000
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`Int. Cl? ................................................ .. A61N 5/10
`.... .. 378/65; 3787124
`Field of Search ........................ .. 378,565, 124, 125,
`378.5126
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`A radiation therapy system according to the present inven-
`tion includes a treatment system and an imaging system. The
`treatment system employs a first tungsten target to generate
`high power X-rays for treatment. The imaging system uses
`a second target to generate low power X-rays for imaging.
`The targets are arranged such that the resulting treatment and
`imaging beams are generally collinear.
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`12 Claims, 3 Drawing Sheets
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`23
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`1 Diagnostic
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`Target
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`Page 1 of 7
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`U.S. Patent
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`Sep. 3, 2002
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`Sheet 2 of3
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`US 6,445,766 B1
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`100
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`Q
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`Electron
`Accelerator
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`Guide
`Ma2g3net
`:5"
`t\:v § Scattering
`Q \ Foil 15
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`Measuring
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`Chamber 60
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`Electmn
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`FIG. 2
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`U.S. Patent
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`Sheet 3 of3
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`US 6,445,766 B1
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`jjxug
`e-beam 1 \___
`-—___. “
`e-beam 2 -7" ‘
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`Start
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`Turn Off
`guide magnet
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`Guide e-beam
`to diagnostic
`target
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`Obtain
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`diag. image(s)
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`Turn on
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`Guide e-beam
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`target
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`408
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`Generate
`treatment
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`beam
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`‘E
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`US 6,445,766 B1
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`1
`SYSTEM AND METHOD FOR IMPROVED
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`DIAGNOSTIC IMAGING IN A RADIATION
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`TREATMENT SYSTEM
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`BACKGROUND OF THE INVENTION
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`1. Field of the Invention
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`The present invention relates to X-ray diagnostic imaging
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`and, in particular, to X-ray diagnostic imaging in a radiation
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`therapy treatment system.
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`2. Description of the Related Art
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`The use of linear accelerators in medicine is well known.
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`Such linear accelerators are used for treating patients with
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`radiation therapy, such as X-rays or electron beams. Such
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`X-rays are created when high energy electrons are deceler-
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`ated in a target material such as tungsten.
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`In such radiation therapy systems, it is desirable to obtain
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`X-ray images for treatment diagnosis and treatment plan-
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`ning. Typically, radiation therapy systems use full energy
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`electron beams to produce X-rays for diagnostic imaging.
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`These high energy X-rays (about 2 MeV) produce washed
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`out images that are difficult to interpret.
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`An alternative is to use low voltage sources, but typical
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`low voltage sources are not collinear with the treatment
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`beam. Consequently, the accuracy of the subsequent therapy
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`relies on interpreting the relative position of the two beams.
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`As such, there is a need for a radiation therapy device that
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`employs low power X-rays for imaging that are substantially
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`aligned with treatment X-rays.
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`SUMMARY OF THE INVENTION
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`These and other drawbacks in the prior art are overcome
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`in large part by a system and method according to the present
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`invention. A diagnostic target is provided substantially adja-
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`cent a treatment target at an X-ray exit window or aperture
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`in a linear accelerator. In a normal or treatment mode, a
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`guide or bending magnet directs an electron beam toward
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`the
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`patient. In a diagnostic mode, the guide magnet is turned off
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`and the electron beam is directed at the diagnostic target
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`such that diagnostic X-rays are directed at the patient. High
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`energy X-rays are absorbed by head shielding. Low energy
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`(about 500 keV) X-rays are used for diagnostic imaging. The
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`high energy treatment beam and the low energy imaging
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`beam are substantially collinear, thereby allowing use of the
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`same beam shielding device hardware in both modes.
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`A radiation therapy system according to the present
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`invention includes a treatment system and an imaging sys-
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`tem. The treatment system employs a first tungsten target to
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`generate high power X-rays for treatment. The imaging
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`system uses a second target to generate low power X-rays
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`for imaging. The targets are arranged such that the resulting
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`treatment and imaging beams are collinear.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`Abetter understanding of the invention is obtained when
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`the following detailed description is considered in conjunc-
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`tion with the following drawings in which:
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`FIG. 1 is a diagram of a prior art radiation therapy system
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`suitable for use with with a system in accordance with an
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`implementation of the invention;
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`FIG. 2 is a block diagram of a radiation therapy system in
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`accordance with an embodiment of the present invention;
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`FIG. 3 is a diagram illustrating beam direction according
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`to an implementation of the invention; and
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`FIG. 4 is a flowchart illustrating a method according to an
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`implementation of the invention.
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`DETAILED DESCRIPTION OF THE
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`INVENTION
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`FIG. 1-4 illustrate an improved radiation therapy system
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`with diagnostic imaging according to an implementation of
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`the invention. A diagnostic target is provided substantially
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`adjacent a treatment target at an X-ray exit window or
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`aperture in a linear accelerator. In a normal or treatment
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`mode, a guide magnet directs an electron beam toward the
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`treatment target, generating X-rays directed at the patient. If
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`electron beam treatment is desired, no treatment target is
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`used in treatment mode. In a diagnostic mode, the guide
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`magnet is turned off and the electron beam is directed at the
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`diagnostic target such that diagnostic X-rays are directed at
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`the patient. High energy X-rays are absorbed by head
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`shielding. Low energy (about 500 keV) X-rays are used for
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`diagnostic imaging. The high energy treatment beam and the
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`low energy imaging beam are substantially collinear,
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`thereby allowing use of the same beam shielding device
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`hardware in both modes.
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`FIG. 1 illustrates a radiation emitting system 11. The
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`radiation emitting system 11 includes a radiation treatment
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`device 2 of common design, which utilizes plates 4 and a
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`control unit in a housing 9 along with a treatment processing
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`unit 100 constructed in accordance with the present inven-
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`tion. The radiation treatment device 2 includes a gantry 6
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`which can be swiveled around a horizontal axis of rotation
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`8 in the course of therapeutic treatment. Plates 4 are fastened
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`to a projection of gantry 6. To generate the high-powered
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`radiation required for the therapy, a linear accelerator is
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`located in gantry 6. The axis of the radiation bundle emitted
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`from the linear accelerator and gantry 6 is designated 10.
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`Electron, photon, or any other detectable radiation can be
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`used for the therapy.
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`During the treatment, the radiation beam is trained on a
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`zone 12 of an object 13, for example, a patient who is to be
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`treated, and who lies at the isocenter of the gantry rotation.
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`The rotational axis 8 of the gantry 6, the rotational axis 14
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`of a treatment table 16, and the beam axis 10 all preferably
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`intersect in the isocenter. In addition, an imaging unit 17
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`may be provided for diagnostic or setup purposes. The
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`construction of such a radiation treatment device is
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`described in general in a brochure “Digital Systems for
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`Radiation Oncology”, Siemens Medical Laboratories, Inc.
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`A91004-M2630-B358-01 -4A00, September 1991. An
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`exemplary radiation treatment system is the Primus system,
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`available from Siemens Medical Systems, Inc., Concord,
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`Calif. The imaging unit may be the Beamview system, also
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`available from Siemens Medical Systems, Inc., Concord,
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`Calif.
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`FIG. 2 shows a portion of an illustrative radiation treat-
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`ment device 2 and portions of treatment processing unit 100
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`in more detail. An electron beam 1 is generated in an
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`electron accelerator 20. The accelerator 20 includes an
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`electron gun 21, a wave guide 22, and an evacuated envelope
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`or guide magnet housing 23. A trigger system 3 generates
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`injector trigger signals and supplies them to injector 5.
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`Based on these injector trigger signals, injector 5 generates
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`injector pulses which are fed to electron gun 21 in accel-
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`erator 20 for generating electron beam 1. Electron beam 1 is
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`accelerated and guided by wave guide 22. For this purpose,
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`a high frequency
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`supplies radio frequency (RF) signals for the generation of
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`an electromagnetic field supplied to wave guide 22. The
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`3
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`21 are accelerated by this electromagnetic field in wave
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`guide 22 and exit at the end opposite to electron gun 21 as
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`electron beam 1. Electron beam 1 then enters a guide magnet
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`23, and from there is guided through a window 7 along axis
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`10. After passing through a first scattering foil 15, the beam
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`goes through a passageway 51 of a shield block 50 and
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`encounters a second scattering foil 17. Next, the beam is sent
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`through a measuring chamber 60,
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`ascertained. If the scattering foils are replaced by a target,
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`the radiation beam is an X-ray beam. Finally, aperture plate
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`arrangement 4 includes a pair of plates 41 and 42. Of course,
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`this is just one example of a beam-shielding arrangement
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`that can be used in the invention. The invention is suitable
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`in other arrangements, as is well appreciated by those skilled
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`in the art. For example, the beam shielding arrangement may
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`be a multi-leaf collimator employing a plurality of thin
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`leaves.
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`Plate arrangement or beam shielding device 4 may be
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`embodied as one or more pairs of aperture plates 41 and 42
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`and additional pairs of aperture plates (not shown) arranged
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`perpendicular to plates 41 and 42. in order to change the size
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`of the irradiated field, the aperture plates can be moved with
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`respect to axis 10 by a drive unit 43 which is indicated in
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`FIG. 2 only with respect to plate 41. Drive unit 43 comprises
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`an electric motor which is coupled to plates 41 and 42 and
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`which is controlled by a motor controller 40. Position
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`sensors 44 and 45 are also coupled to plates 41 and 42,
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`respectively, for sensing their positions. The plate arrange-
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`ment 4 is employed both in the treatment mode and in the
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`imaging mode, as will be explained in greater detail below.
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`The area of a patient that is irradiated is known as the
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`field. As is well known, plates 4 are substantially impervious
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`to the emitted radiation. They are mounted between the
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`radiation source and patient in order to delimit the field.
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`Areas of the body, for example, healthy tissue, are therefore
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`subjected to as little radiation as possible, and preferably to
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`none at all. Preferably, with at least one of the plate movable,
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`the distribution of radiation over the field need not be
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`uniform (one region can be given a higher dose than
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`another); further, with the gantry able to be rotated, different
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`beam angles and radiation distributions are allowed without
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`having to move the patient around.
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`The central treatment processing or control unit 100 (FIG.
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`1) is usually located apart from radiation treatment device 2
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`in a different room to protect the therapist from radiation.
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`Treatment processing unit 100 includes an output device,
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`such as at least one visual display unit or monitor 70, and an
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`input device, such as a keyboard 19, although data can be
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`input also through data carriers, such as data storage devices.
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`The treatment processing unit 100 is typically operated by
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`the therapist who administers actual delivery of a radiation
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`treatment as prescribed by an oncologist. By utilizing key-
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`board 19, or other input device, the therapist enters into a
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`control unit 76 of the treatment processing unit 100 the data
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`that defines the radiation to be delivered to the patient, for
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`example, according to the prescription of the oncologist. The
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`program can also be input via another input device, such as
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`a data storage device, through data transmission. On the
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`screen of a monitor 70, various data can be displayed before
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`and during the treatment.
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`Central processing unit 18 (FIG. 2), included in treatment
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`processing unit 100, is connected with the input device, e.g.,
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`keyboard 19, for inputting the prescribed delivery of the
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`radiation treatment and with a dose control unit 61 that
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`generates the desired values of radiation for the controlling
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`trigger system 3. Trigger system 3 suitably adapts the pulse
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`Page 6 of 7
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`4
`repetition frequency or other parameters to change the
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`radiation output. A digital dosimetry system is particularly
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`advantageous in order to more easily control the digital
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`output of central processing unit 18. Central processing unit
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`18 suitably includes a control unit 76 for controlling execu-
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`tion of the treatment program in conjunction with memory
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`77 and a combination circuit 78 which suitably receives
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`signals from the control unit 76 and memory 77 for com-
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`bination to produce a set signal, S, that identifies a dose rate
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`for dose rate control unit 61 in accordance with the present
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`invention.
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`In addition, as will be explained in greater detail below,
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`the CPU 18 generates control signals to turn off the guide
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`magnet and redirect the electron beam using in-plane steer-
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`ing coils (not shown) through a diagnostic target 102 for
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`diagnostic imaging using the imaging unit 17.
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`More particularly, an imaging unit 17 is provided such
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`that an image detector 69 is positioned in opposition to the
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`treatment head and the diagnostic target 102. The image
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`detector is coupled to an imaging station 80, which includes
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`a video control unit 71 for capturing video images and
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`controlling imaging operation, and a display 72 for display-
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`ing the resulting images. In one implementation, the video
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`control unit 71 is implemented as a video camera, video
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`capture board, and various processing circuitry.
`In this
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`implementation, the image detector 69 is a metal foil scin-
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`tillation detector. Alternatively, the image detector 69 may
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`be implemented as a flat panel detector comprising one or
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`more arrays of photosensitive cells.
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`The use of the diagnostic target is illustrated in greater
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`detail with reference to FIG. 3. As shown, the guide magnet
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`housing 23 includes the guide magnet 300, and the diag-
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`nostic target 102. In a first mode,
`the CPU 18 supplies
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`control signals to cause the guide magnet 300 to be activated
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`and the X-ray beam 100 to be generated, as described above.
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`In a diagnostic mode, the CPU 18 generates control signals
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`to turn off the guide magnet 300 and engage in-plane
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`steering coils (not shown) the steer the beam 200 into the
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`diagnostic target 102. Forward or high energy X-rays area
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`absorbed by the head shielding. Ninety degree, 500 keV
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`X-rays are used to obtain clearer pictures.
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`Turning now to FIG. 4, a flowchart illustrating operation
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`of an implementation of the invention is shown. In a step
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`400, the CPU 18 sends control signals to turn off the guide
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`magnet 300. In a step 402, the in-plane steering coils are
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`used to guide the electron beam 200 to the diagnostic target.
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`The diagnostic target, which may be formed of copper or
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`tungsten, for example, is positioned such that low energy 90
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`degree X-rays are provided for imaging. In a step 404, the
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`resulting 90 degree X-rays are used to obtain one or more
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`images. Once the desired images have been obtained, the
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`CPU sends control signals to turn on the guide magnet 300,
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`in a step 406. In a step 408, the electron beam 100 is guided
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`to impinge on a treatment target (if desired) and the treat-
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`ment beam is generated in step 410.
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`The invention described in the above detailed description
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`is not intended to be limited to the specific form set forth
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`herein, but is intended to cover such alternatives, modifica-
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`tions and equivalents as can reasonably be included within
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`the spirit and scope of the appended claims.
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`What is claimed is:
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`1. A radiation therapy device operable in a first mode and
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`a second mode, comprising:
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`a control unit for controlling application of radiation in
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`said first mode and said second mode; and
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`an electron accelerator, said electron accelerator includ-
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`ing:
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`Page 6 of 7
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`US 6,445,766 B1
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`5
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`6
`resulting treatment beam and a resulting imaging beam
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`are substantially collinear.
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`8. A radiation therapy device according to claim 7:
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`said imaging unit and said treatment unit adapted to
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`employ a same beam shielding device for imaging and
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`treatment.
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`9. A radiation therapy method, comprising:
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`providing a radiation beam source
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`providing a radiation therapy unit having a first target for
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`generating treatment beams from said radiation beam
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`source;
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`providing an imaging unit having a second target for
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`generating imaging beams from said radiation beam
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`source;
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`wherein said first target and said second target are posi-
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`tioned such that resulting treatment and imaging beams
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`are substantially collinear.
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`10. A method according to claim 9, further comprising
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`providing one or more plate arrangements suitable for use
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`for imaging and treatment.
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`11. A radiation treatment method, comprising:
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`generating low power X-rays using a first target, said low
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`power X-rays being used for diagnostic imaging;
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`generating high power X-rays using a second target, said
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`high power X-rays being used for treatment, wherein
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`said low power X-rays and said high power X-rays are
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`generated generally collinearly and wherein said gen-
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`erating said high power X-rays comprises activating a
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`guide magnet and directing an electron beam at said
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`second target;
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`said generating low power X-rays comprising deactivat-
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`ing said guide magnet and directing said electron beam
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`at said first target.
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`12. An electron accelerator, comprising:
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`an electron gun;
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`a waveguide for receiving an electron beam from said
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`electron gun;
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`a guide magnet for directing said electron beam to a
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`desired target via a window in a first mode; and
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`a diagnostic target, wherein said electron beam is directed
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`at said diagnostic target in a second mode, said electron
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`beam in said first mode and said second mode being
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`generally collinear.
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`an electron gun;
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`a waveguide for receiving an electron beam from said
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`electron gun;
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`a guide magnet for directing said electron beam to a
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`desired target via a window in said first mode; and
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`a diagnostic target, wherein said electron beam is
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`directed at said diagnostic target
`in said second
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`mode.
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`2. A radiation therapy device in accordance with claim 1,
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`said electron beam adapted to undergo 90 degree Compton
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`scattering in said diagnostic target.
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`3. A radiation therapy device in accordance with claim 2,
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`further including an imaging unit adapted to receive result-
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`ing scattered radiation for diagnostic imaging.
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`4. A radiation therapy device operable in a first mode and
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`a second mode, comprising:
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`a control unit for controlling application of radiation in
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`said first mode and said second mode; and
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`an electron accelerator, said electron accelerator includ-
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`ing:
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`an electron gun;
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`a waveguide for receiving an electron beam from said
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`electron gun;
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`a guide magnet housing having a guide magnet for
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`directing said electron beam to a desired target via a
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`window in said guide magnet housing in said first
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`mode; and
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`a diagnostic target, positioned substantially adjacent
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`said window, wherein said electron beam is directed
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`at said diagnostic target in said second mode.
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`5. A radiation therapy device in accordance with claim 4,
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`said electron beam adapted to undergo 90 degree Compton
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`scattering in said diagnostic target.
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`6. A radiation therapy device in accordance with claim 5,
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`further including an imaging unit adapted to receive result-
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`ing scattered radiation for diagnostic imaging.
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`7. A radiation therapy device comprising:
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`a radiation beam source;
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`an imaging unit employing a first target for generating low
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`energy imaging beams from said radiation beam
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`source;
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`a treatment unit employing a second target for generating
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`high energy treatment beams from said radiation beam
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`source;
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`wherein said first target and said second target are posi-
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`tioned substantially adjacent one another such that a
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