United States Patent
`US 6,600,810 B1
`(10) Patent No.:
`(12)
`Hughes
`(45) Date of Patent:
`Jul. 29, 2003
`
`
`US006600810B1
`
`(54) MULTIPLE LAYER MULTILEAF
`COLLIMATOR DESIGN TO IMPROVE
`RESOLUTION AND REDUCE LEAKAGE
`
`5,619,042 A
`5,748,703 A *
`* cited b
`:
`y examiner
`
`4/1997 Hughes... 250/492.3
`5/1998 Cosmam oe 378/152
`
`(75)
`
`Inventor:
`
`John H. Hughes, Martinez, CA (US)
`
`.
`(*) Notice:
`
`(56)
`
`References Cited
`U.S. PATENT DOCUMENTS
`
`Primary Examiner—Robert H. Kim
`Assistant Examiner—Hoon K. Song
`(73) Assignee: Siemens Medical Solutions USA,Inc.,
`67)
`ABSTRACT
`Malvern, PA (US)
`Aspects of a multiple layer multileaf collimator capable of
`.
`.
`oo,
`improving resolution for coverage ofa target during radia-
`Subjectto any disclaimer, the term of this
`tion therapy are described. A multiple layer multileaf colli-
`patent is extended or adjusted under 35
`mator includesa first layer of multiple elongated radiation
`US.C, 154(b) by 0 days.
`blocking leaves supported byafirst frame for individual leaf
`(21) Appl. No.: 09/131,177
`positioningin a first direction. The multiple layer multileaf
`“44.
`collimator further includes a to second layer of multiple
`(22)
`Filed:
`Aug. 10, 1998
`elongated radiation blocking leaves supported by a second
`(SL) Unt. C0 eee ecccccccsecseeseeseeseereeseeseeneesees G21K 1/04_frame for individual leaf positioning in a seconddirection,
`(52) US. C1. cece cneeeneeecscteneseneenees 378/152; 378/147
`the second direction offset at a desired anglerelative to the
`(58) Field of Search ......ce 378/65, 145, 147
`first direction, wherein the individual leaves ofthe first and
`378/149 150 151 152
`second layers conform more closely with a target shape to
`,
`,
`,
`improve resolution. Further, the second layer is positioned
`abovethe first layer and provides leakage coverage for the
`multiple elongated radiation blocking leaves of the first
`layer. The multiple layer multileaf collimator is not limited
`to a single type of multileaf collimator and thus is suitable
`for use in a variety of multileaf collimator designs, including
`single focus and double focus multileaf collimators.
`
`4,463,266 A
`4,987,309 A *
`5,166,531 A
`5,297,037 A *
`5,591,983 A
`
`7/1984 Brahme ..........c. 250/505.1
`1/1991 Klasen et al.
`.
`we 250/492.1
`
`. 250/505.1
`
`11/1992 Huntzinger ...
`.
`
`3/1994 Ifuku oe 378/05 X
`T/1997 Yao wee eee eeeeee ee 250/505.1
`
`17 Claims, 6 Drawing Sheets
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`U.S. Patent
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`Jul. 29, 2003
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`1
`MULTIPLE LAYER MULTILEAF
`COLLIMATOR DESIGN TO IMPROVE
`RESOLUTION AND REDUCE LEAKAGE
`
`US 6,600,810 B1
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`2
`SUMMARYOF THE INVENTION
`
`The present invention provides aspects of a multiple layer
`multileaf collimator capable of improving resolution for
`coverage of a target during radiation therapy. A multiple
`layer multileaf collimator includesafirst layer of multiple
`FIELD OF THE INVENTION
`elongated radiation blocking leaves supported by a first
`frame for individual leaf positioning inafirst direction. The
`The present invention relates to collimators in radiation
`multiple layer multileaf collimator further includes a second
`therapy devices, and more particularly to multiple layer
`layer of multiple elongated radiation blocking leaves sup-
`multileaf collimator design to improve resolution and reduce
`ported by a second frame for individual leaf positioning in
`leakage.
`a second direction, the second direction offset at a desired
`angle relative to the first direction, wherein the individual
`leaves of the first and second layers conform more closely
`with a target shape to improve resolution. Further,
`in a
`preferred aspect, the second layer is positioned above the
`first layer and provides leakage coverage for the multiple
`elongated radiation blocking leaves of the first layer.
`Throughthe present invention, more precision in blocking
`radiation from healthy tissue and organs during radiation
`therapy is achieved. Such benefits are particularly significant
`to provide more effective treatment in the elimination of
`unhealthy target areas. Thus, the present invention allows
`one to increase the dose delivered while not exceeding
`healthy tissue constraints. These and other advantagesof the
`aspects of the present invention will be more fully under-
`stood in conjunction with the following detailed description
`and accompanying drawings.
`
`BACKGROUND OF THE INVENTION
`
`During conventional radiation therapy treatment, a beam
`of radiation, varying in angles and intensities, is directed at
`an area of a patient, e.g., at a tumor. Typical treatment field
`shapes, square, rectangular, or a modification thereof, result
`in a three-dimensional treatment volumethat, unfortunately,
`may include healthy tissue and organs. For obvious safety
`reasons, the dose capable of being delivered to the tumoris
`limited by the healthy tissue and organs in the path of the
`radiation beam. Since cure rates for many tumors are a
`sensitive function of the dose they receive, reducing the
`amount of exposed healthy tissue and organs is highly
`desirable in order to be able to increase the dose delivered
`
`to the tumor. Methods of making the treatment volume
`correspond more closely with a tumor include moving
`solid-jaw blocks during treatment, scanning the radiation
`beam over the volumeto be treated, and using a multileaf
`collimator to create an irregularly shaped field related to the
`shape of the tumor.
`
`An example of a multileaf collimator arrangementposi-
`tioned about the central axis of a radiation-emitting head for
`shaping an irradiated beam is disclosed in U.S. Pat. No.
`5,166,531,
`issued to Hunzinger on Nov. 24, 1992. Two
`opposingarrays of side-by-side elongated radiation blocking
`collimator leaves act in place of opposing solid jaw blocks.
`Each leaf in each opposing array can be moved longitudi-
`nally towards or away from the central axis of the beam,thus
`defining a desired shape through which the radiation beam
`will pass.
`
`An enhancement on the multileaf collimator approach is
`described in U.S. Pat. No. 5,591,983, issued to Yao on Jan.
`7, 1997. In Yao, a multiple layer multileaf collimator design
`is formed through first and second layers of a plurality of
`elongated radiation blocking leaves. The leaves of each layer
`are arranged adjacent one anotherso as to form two opposed
`rows of adjacently positioned leaves and are movable in a
`longitudinal direction which can be either generally trans-
`verse to or in the samedirection of the beam. Thelayers are
`arranged one above anotherin the beam direction and offset
`in a lateral direction, so that spaces between adjacent leaves
`of the first and second layers are positioned over and under,
`respectively, leaves of the respective first and second layers.
`The arrangementof the leaves allows a reduction in prob-
`lems of radiation leakage between leaves of a multileaf
`collimator. However, the arrangement does not provide as
`fine a resolution as desired to allow more accurate block
`positioning for creating a block volumein correspondence
`with a tumor shape.
`
`Accordingly, what is needed is a system and method for
`utilizing a multiple layer multileaf collimator arrangement
`that improves resolution and reduces leakage for radiation
`delivery. The present invention addresses such a need.
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`BRIEF DESCRIPTION OF THE DRAWINGS
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`FIG. 1 illustrates a radiation treatment device including a
`multiple layer multileaf collimator in accordance with the
`present invention.
`FIGS. 2a and 2b illustrate a multiple layer multileaf
`collimator arrangementof the prior art.
`FIG. 3 illustrates a partial
`top view of the multileaf
`collimator arrangementofthe prior art of FIG. 2b in greater
`detail.
`
`FIG. 4 illustrates a three-dimensional view of a multiple
`layer multileaf collimator in accordance with an embodi-
`ment of the present invention.
`FIG. 5 illustrates a partial top view of the multiple layer
`multileaf collimator in accordance with the present inven-
`tion.
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`DETAILED DESCRIPTION OF THE
`INVENTION
`
`The present invention relates to a multiple layer multileaf
`collimator with improved resolution. The following descrip-
`tion is presented to enable one of ordinary skill in theart to
`make and use the invention and is provided in the context of
`a patent application and its requirements. Various modifica-
`tions to the preferred embodimentwill be readily apparent to
`those skilled in the art and the generic principles herein may
`be applied to other embodiments. Thus, the present inven-
`tion is not intended to be limited to the embodiment shown
`but is to be accorded the widest scope consistent with the
`principles and features described herein.
`FIG. 1 illustrates a radiation treatment device 2 which
`utilizes a multiple layer multileaf collimator 4 in accordance
`with the present invention along with a treatment processing
`unit 100. The radiation treatment device 2 comprises a
`gantry 6 which can be swiveled around a horizontal axis of
`rotation 8 in the course of therapeutic treatment. Collimator
`4 is fastened to a projection of gantry 6. To generate the
`high-powered radiation required for the therapy, a linear
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`US 6,600,810 B1
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`accelerator is located in gantry 6. The axis of the radiation
`bundle emitted from the linear accelerator and gantry 6 is
`designated 10. Electron, photon, or any other detectable
`radiation can be used for the therapy. During the treatment,
`the radiation beam is trained on a zone 12 of an object 13,
`for example, a patient whois to be treated, and wholies at
`the isocenter of the gantry rotation. The rotational axis 8 of
`the gantry 6, the rotational axis 14 of a treatmenttable 16,
`and the beam axis 10 all preferably intersect in the isocenter.
`The multiple layer multileaf collimator 4 in accordance
`with the present invention suitably comprises two pairs of
`opposing elongated radiation blocking leaves, the pairs in
`separate planes and offset at a desired angle relative to one
`another. As mentioned above, a prior art approach to mul-
`tiple multileaf collimator design is described in U.S. Pat. No.
`5,591,983 (hereinafter Yao). FIG. 2aillustrates a side view
`of a prior art multiple layer collimator 4' as presented in Yao.
`Twoidentical layers, an upper layer 20 and a lowerlayer 22,
`of pairs of opposed leaves are shown. The top layer 20
`comprises a middle section having a plurality of relatively
`narrow leaves 24 positioned in a side-by-side relationship,
`whichis flanked onits left side by a relatively wide trimmer
`leaf 26 and on its right side by a relatively wide endleaf 28.
`The construction of bottom layer 22 is a mirror image of
`layer 20 and therefor common reference numbers are used
`for leaves 26 and 28. However, since in the middle section
`of layers 20 and 22,
`the narrow leaves are physically
`overlapping, the narrow leaves of layer 22 are referred by
`reference 30. It should also be noted that although wide and
`narrow leaves are shown in this embodiment, the leaves can
`all be of substantially the same widths or can be different
`widths and they could still be utilized within the spirit and
`scope of the present invention.
`As shown in a top view of collimator 4' in FIG. 2b, top
`layer 20 being shown in solid lines and bottom layer 22
`being shown in dashed lines, frame 32 supports each of the
`leaves 24 and 28 of the top layer 20 and each of leaves 30
`and 28 of lower layer 22 in a paired opposedrelationship, so
`that they are independently movable in their longitudinal
`dimension into and out of beam axis 10 (the Y direction
`shown in FIG. 25). In general, the maximum size field is a
`rectangle of dimension WxL.Forthe illustration of FIG. 2b,
`the leaves 24 and 30 are shownin various positions to create
`shape 34. The operation of the leaves of layer 20 and layer
`22 for creating a treatmentfield is as is conventional in prior
`art single layer multileaf collimator arrangements, which are
`well understood by those skilled in theart.
`FIG. 3 illustrates a portion of the top view of FIG. 2b in
`greater detail. As functionally shown therein, frame 32
`includesa plurality of motors 40 mounted thereon which are
`used in a conventional manner to individually position the
`leaves, e.g, 24, and 30, of the collimator 4' into and out of
`the radiation beam for controllably defining the treatment
`field. One example of drive means (not shown) suitable for
`this is an individually driven worm gear for individually
`engaging a toothed track or floating nut mounted on each
`leaf. Details of one such prior art leaf driving means are
`provided in U.S. Pat. No. 5,160,847, issued to Leavitt, et al.,
`on Nov. 3, 1992.
`While providing a reduction in leakage through the
`arrangement of one layer over another and a shift of the
`blades in a lateral direction to cover gaps between blades in
`a lowerlayer, the prior art multiple layer multileaf collimator
`lacks preferred resolution in isolating the treatment area and
`avoiding undue exposure of healthy tissue or organs to the
`radiation therapy. The present invention improvesresolution
`in a multiple layer multileaf collimator by providing a
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`multiple layer multileaf collimator 4 comprising two layers
`of opposing pairs of elongated radiation blocking leaves,
`wherethe layers are not linked and can be rotated to within
`a desired angle, e.g., approximately between 0° and 90°, of
`one another. In a preferred embodiment, a top layer is
`capably positioned substantially between about 0° and 90°
`relative to a bottom layer. FIG. 4 illustrates a three-
`dimensional view of two multileaf layers, 22 and 50, in
`accordance with a preferred embodiment of the present
`invention. For convenience of illustration,
`layer 22 is
`described as being provided in a manner equivalent to layer
`22 of the prior art shown in FIG. 2a. As shown in the
`example configuration of FIG. 4, multileaf layer 50 is
`positioned to be substantially perpendicular to multileaf
`layer 22. Layer 50 suitably comprises a multileaf collimator
`that functions similarly to multileaf layer 22 as described
`above, however, the positioning of the multileaf layer 50 to
`a desired angle through a conventional motor/control
`mechanism (not shown) allows greater resolution of cover-
`age for targets than typical sold block arrangements or even
`the parallel multiple multileaf arrangement of Yao. Further,
`it should be appreciated that while in the arrangement of Yao
`differing widths are used for the end and trimmerleafs as
`compared with the middle section leaves, this serves as one
`example of a suitable leaf set. Of course,
`the present
`invention is capably achieved with other leaf arrangements,
`including those having leaves of substantially equivalent
`widths.
`
`FIG. 5 illustrates more particularly coverage capabilities
`for a multiple layer multileaf collimator arrangement in
`accordance with the present invention. In FIG. 5, a partial
`top view of one-half of each multileaf layer 22 and 50 is
`shown, where a top multileaf layer 50 is positioned at a
`preferred angle of about 90° (i.e., substantially
`perpendicular) relative to a bottom multileaf layer 22. As
`further shown in FIG. 5, the individual leaves of each layer,
`30 in layer 22 and 24'in layer 50, are separately movable via
`motors 40 attached to frame means 32 and 32', respectively,
`operating as described above. The placement of multileaf
`layer 50 at an angularoffset, e.g., of about 90°, allows the
`individual leaves 24' to be moved in close proximity to and
`in a close correspondence with a target 60, e.g., a tumor,
`from multiple directions rather than being limited to merely
`equivalent directions as in the layer arrangement of Yao.
`Thus, the resolution of coverage for targets is improved, as
`well as gaining the advantage that because there is crossing
`over between the top and bottom layer, the leakage areas
`between leaves are protected.
`the multiple multileaf
`It should be appreciated that
`arrangement in accordance with the present invention is
`suitable for use with any type of multileaf design type or
`beam defining system, as is known and/or in use in theart.
`For example, the present invention is applicable in single
`focus and double focus multileaf collimators. An example of
`a single focus multileaf collimator is provided in the afore-
`mentioned U.S. Pat. No. 5,166,531, while an example of a
`double focus multileaf collimator is provided in U.S. Pat.
`No. 4,463,263 issued Jul. 31, 1984 to Brahme. Thus, the
`present
`invention is suitable with multileaf collimator
`designs that employ blades/leaves of varying thickness, size,
`depth,etc.
`Although the present invention has been described in
`accordance with the embodiments shown, one of ordinary
`skill in the art will readily recognize that there could be
`variations to the embodiments and those variations would be
`within the spirit and scope of the present
`invention.
`Accordingly, many modifications may be made by one of
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`ordinary skill in the art without departing from the spirit and
`scope of the appended claims.
`Whatis claimedis:
`
`1. A multiple layer multileaf collimator capable of
`improving resolution for coverage of a target during radia-
`tion therapy, the multiple layer multileaf collimator com-
`prising:
`layer of multiple elongated radiation blocking
`a first
`leaves supported by a first frame for individual leaf
`positioning in a first direction; and
`a second layer of multiple elongated radiation blocking
`leaves supported by a second frame for individualleaf
`positioning in a second direction, the second direction
`offset at a desired angle x, where 0°=x5 90°, relative to
`the first direction to achieve an arrangementofthefirst
`layer and second layer that ranges from parallel to
`perpendicular through rotation of the second layer
`relative to the first layer, wherein the individual leaves
`of the first and second layers conform more closely
`with a target shape to improve resolution.
`2. The multiple layer multileaf collimator of claim 1
`wherein the second layer is positioned abovethefirst layer.
`3. The multiple layer multileaf collimator of claim 2
`wherein the second layer provides leakage coverage for the
`multiple elongated radiation blocking leaves of the first
`layer.
`4. The multiple layer multileaf collimator of claim 1
`wherein the desired angle comprises an angle of about 90°.
`5. The multiple layer multileaf collimator of claim 1
`further comprising a plurality of motor means with thefirst
`and second framesfor the individual leaf positioning of the
`first and second layers.
`6. The multiple layer multileaf collimator of claim 1
`whereinthefirst layer further comprises two opposing arrays
`of elongated radiation blocking leaves.
`7. The multiple layer multileaf collimator of claim 1
`wherein the second layer further comprises two opposing
`arrays of elongated radiation blocking leaves.
`8. A radiation emitting device with improved resolution
`coverage for a target during radiation therapy, the radiation
`emitting device comprising:
`a radiation source for providing a radiation beam; and
`a collimator for shaping the radiation beam,the collimator
`comprising a first layer of multiple elongated radiation
`blocking leaves supported by a first frame for indi-
`vidual leaf positioning in a first direction, and a second
`layer of multiple elongated radiation blocking leaves
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`supported by a second frame for individual leaf posi-
`tioning in a second direction, the second direction offset
`at a desired angle x, where 0°Sx=90°, relative to the
`first direction to achieve an arrangement ofthe first
`layer and second layer that ranges from parallel to
`perpendicular through rotation of the second layer
`relative to the first layer, wherein the individual leaves
`of the first and second layers conform more closely
`with a target shape to improve resolution.
`9. The radiation emitting device of claim 8 wherein the
`second layer is positioned abovethefirst layer.
`10. The radiation emitting device of claim 9 wherein the
`second layer provides leakage coverage for the multiple
`elongated radiation blocking leaves of the first layer.
`11. The radiation emitting device of claim 8 wherein the
`desired angle comprises an angle of about 90°.
`12. The radiation emitting device of claim 8 further
`comprising a plurality of motor means with the first and
`second framesfor the individual positioning of the multiple
`elongated radiation blocking leaves of the first and second
`layers.
`13. The radiation emitting device of claim 8 wherein the
`first layer further comprises two opposing arrays of elon-
`gated radiation blocking leaves.
`14. The radiation emitting device of claim 8 wherein the
`second layer further comprises two opposing arrays of
`elongated radiation blocking leaves.
`15. A method for improving resolution of coverage of a
`target during radiation therapy by a radiation emitting
`device, the method comprising:
`providing a first pair of opposing multiple elongated
`radiation blocking leaves in a first plane within a
`collimator of the radiation emitting device; and
`providing a second pair of opposing multiple elongated
`radiation blocking leaves in a second plane within the
`collimator, the second pair being rotatable to within a
`desired angularoffsetrelative to the first pair to achieve
`an arrangement of the first pair and second pair that
`ranges from parallel to perpendicular, wherein thefirst
`and second pairs more closely conform with a target
`shape while avoiding leakage between the multiple
`elongated radiation blocking leaves.
`16. The method of claim 15 wherein the second pair is
`rotatable to within approximately 0° and 90° ofthefirst pair.
`17. The method of claim 15 wherein the first plane is
`below the second plane.
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