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`Jaffray et al.
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`(10) Patent N0.:
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`(45) Date of Patent:
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`US 6,842,502 B2
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`Jan. 11, 2005
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`US006842502B2
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`7/1999 Huang ................. .. 250/370.09
`5,929,449 A
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`9/1999 Baba et al.
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`5,949,811 A
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`3/2000 Roosetal.
`6,041,097 A *
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`6,148,058 A * 11/2000 Dobbs .. .......... ..
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`.i.i.N378/197
`6,318,892 B1 * 11/2001 s::ui<ia:fai............
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`378/65
`6,385,286 B1 *
`5/2002 Fitchard et al.
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`6,385,288 B1 *
`5/2002 Kanematsu ................ .. 378/65
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`OTHER PUBLICATIONS
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`Edmon (Readlnga MAI Add1S0H‘We51eY> 1978), P- 6‘12-*
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`Jaffray et al., “Exploring ‘Target of the Day’ Strategies for
`a Medical Linear Accelerator with Conebeam—CT Scanning
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`Capability,” XIIth ICCR held in Salt Lake City, Utah, May
`27-30, 1997, pp. 172-174.
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`Jaffray et al., “Conebeam Tomographic Guidance of Radia-
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`tion Field Placement for Radiotherapy of the Prostate,
`Manuscript accepted for publication in the International
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`Journal of Radiation Oncology, Biology, date unknown, 32
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`pages.
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`(List continued on next page.)
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`Primary Examiner—Allen C. Ho
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`eA”°’”ey’ Agem’ 0’ Fm" Brmks’ Hofer’ G115“ &
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`(57)
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`ABSTRACT
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`A radiation therapy system that includes a radiation source
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`that moves about a path and directs a beam of radiation
`towards an object and a cone-beam computer tomography
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`system. The cone-beam computer tomography system
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`mcludes an Hay 50”“ that ‘°1m“S an Xiray beam 1“ a
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`C0He'beam £99“ towards an Pblect to b‘? mlaged and an
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`amorphous silicon flat-panel imager receiving x-rays after
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`they pass through the object, the imager providing an image
`of the object. A computer is connected to the radiation
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`source and the cone beam computerized tomography
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`system, wherein the computer receives the image of the
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`76 Claims, 26 Drawing Sheets
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`(54) CONE BEAM COMPUTED TOMOGRAPHY
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`WITH A FLAT PANEL IMAGER
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`(75)
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`Inventors: David A. Jaifray, Windsor (CA); John
`w- Wong,
`M1 «or
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`Jeflrey H‘ Siewerdesen’ Ann Arbor’ MI
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`(US)
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`(73) Assignee: Dilliam Beaumont Hospital, Royal
`Oak, MI (US)
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`( * ) Notice:
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`Subject to any disclaimer, the term of this
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`patent is extended or adjusted under 35
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`USC, 154(b) by 0 days,
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`(21) Appl. N0.: 09/788,335
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`E11993
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`(22)
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`(65)
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`Eeb- 16: 2001
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`Prior Publication Data
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`US 2003/0007601 A1 Jan. 9, 2003
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`(60)
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`Related U.S. Application Data
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`Provisional application No. 60/183,590, filed on Feb. 18,
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`2000.
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`(51)
`Int. Cl.7 ........................... .. A61N 5/10; H05G 1/60
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`(52) U.s. Cl.
`............................... 378/65; 378/9; 378/19;
`378/196; 378/197; 378/198
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`(58) Field of Search ............................ .. 378/4, 8, 9, 11,
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`378/19, 20, 64, 65, 195, 196, 197, 198
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`(56)
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`References Cited
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`U~S~ PATENT DOCUMENTS
`4,547,892 A * 10/1985 Richey et al.
`............... .. 378/8
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`5,157,707 A
`10/1992 Ohlson ............ ..
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`5,394,452 A
`2/1995 swerdloff et a1.
`373/65
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`5,411,026 A
`5/1995 Carol
`.................. ..
`.. 600/439
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`5,661,773 A
`8/1997 Swerdloff et a1.
`378/65
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`5,663,995 A *
`9/1997 Hu ............... ..
`. 378/15
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`2 * 13; Eédéseiseln --
`,
`,
`an eta.
`. . . . .
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`5/48/00 A
`5/1998 Shepherd 9 a1~
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`
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`5,751,781 A
`5/1998 Brown et al.
`.... ..
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`5,848,126 A * 12/1998 Fujita et al.
`
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`5,912,943 A
`6/1999 Deucher et al.
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`378/65
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`378/65
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`378/195
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`......... .. 378/98.8
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`--
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`Elekta Exhibit 1014
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`US 6,842,502 B2
`Page 2
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`OTHER PUBLICATIONS
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`Jaffray et al., “Managing Geometric Uncertainty in Confor-
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`
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`mal Intensity-Modulated Radiation Therapy,” Seminars in
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`Radiation Oncology, Vol. 9, No. 1, Jan., 1999 pp. 4-19.
`
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`Jaffray et al., “Performance of a Volumetric CT Scanner
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`Based Upon a Flat—Panel Imager,” SPIE Physics of Medical
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`Imaging, Vol. 3659, Feb., 1999, pp. 204-214.
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`Jaffray et al., “A Ghost Story: Spatio—temporal Response
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`Characteristics of an Indirect—Detection Flat—Panel Imager.”
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`Med. Phys., Vol. 26, No. 8, Aug., 1999, pp. 1624-1641.
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`Jaffray et al., “Cone-Beam Computed Tomography with a
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`Flat—Panel Imager: Initial Performance Characterization,”
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`Submission to the Medical Physics Journal for publication
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`on Aug., 1999, 36 pages.
`
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`Siewerdsen et al., “Cone-Beam Computed Tomography
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`with a Flat—Panel Imager: Effects of Image Lag,” Med.
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`Phys., Vol. 26, No. 12, Dec., 1999, pp. 2635-2647.
`
`
`
`
`
`
`
`
`
`in
`Jaffray
`et
`al., Cone-Beam CT: Applications
`
`
`
`
`
`
`
`Image-Guided External Beam Radiotherapy and Brachy-
`
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`
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`therapy, publication source unknown, date unknown, one
`
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`
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`page.
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`
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`Siewerdsen et al., “Cone-Beam CT with a Flat—Panel
`
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`Imager: Noise Consideration for Fully 3-D Computed
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`Tomography,” SPIE Physics of Medical Imaging, Vol. 3336,
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`Feb., 2000, pp. 546-554.
`
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`
`
`Jaffray et al., Cone-Beam Computed Tomography with a
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`
`
`Flat—Panel Imager:
`Initial Performance Characterization,
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`Med. Phys., Vol. 27, No. 6, Jun. 2000, pp. 1311-1323.
`
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`Siewerdsen et al., “Optimization of X-Ray Imaging Geom-
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`etry (with Specific Application to Flat—Panel Cone-Beam
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`
`
`Computed Tomograpyhy),” Non-Final Version of Manu-
`script to be published in Med. Phys., Vol. 27, No. 8, Aug.,
`
`
`
`
`
`
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`
`
`2000, pp. 1-12.
`
`
`
`Dieu et al., “Ion Beam Sputter-Deposited SiN/TiN Attenu-
`
`
`
`
`
`
`
`ating Phase-Shift Photoblanks,” publication source and date
`
`
`
`
`
`
`
`unknown, 8 pages.
`
`
`for
`Jaffray
`al.,
`“Flat-Panel Cone-Beam CT
`et
`
`
`
`
`
`
`
`
`
`
`
`
`Image-Guided External Beam Radiotherapy,” publication
`source unknown, Oct., 1999, 36 pages.
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`* cited by examiner
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`Page 13 of 46
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`Page 13 of 46
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`US 6,842,502 B2
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`1
`CONE BEAM COMPUTED TOMOGRAPHY
`WITH A FLAT PANEL IMAGER
`
`Applicants claim, under 35 U.S.C. § 119(e), the benefit
`of priority of the filing date of Feb. 18, 2000, of U.S.
`Provisional Patent Application Ser. No. 60/183,590, filed on
`the aforementioned date, the entire contents of which are
`incorporated herein by reference.
`BACKGROUND OF THE INVENTION
`1. Field of the Invention
`
`The present invention relates generally to a cone-beam
`computed tomography system and, more particularly, to a
`cone-beam computed tomography system that employs an
`amorphous silicon fiat-panel imager for use in radiotherapy
`applications where the images of the patient are acquired
`with the patient in the treatment position on the treatment
`table.
`2. Discussion of the Related Art
`
`Radiotherapy involves delivering a prescribed tumorcidal
`radiation dose to a specific geometrically defined target or
`target volume. Typically, this treatment is delivered to a
`patient in one or more therapy sessions (termed fractions). It
`is not uncommon for a treatment schedule to involve twenty
`to forty fractions, with five fractions delivered per week.
`While radiotherapy has proven successful
`in managing
`various types and stages of cancer, the potential exists for
`increased tumor control
`through increased dose.
`Unfortunately, delivery of increased dose is limited by the
`presence of adjacent normal structures and the precision of
`beam delivery. In some sites, the diseased target is directly
`adjacent to radiosensitive normal structures. For example, in
`the treatment of prostate cancer, the prostate and rectum are
`directly adjacent. In this situation, the prostate is the targeted
`volume and the maximum deliverable dose is limited by the
`wall of the rectum.
`
`In order to reduce the dosage encountered by radiosensi-
`tive normal structures,
`the location of the target volume
`relative to the radiation therapy source must be known
`precisely in each treatment session in order to accurately
`deliver a tumorcidal dose while minimizing complications in
`normal tissues. Traditionally, a radiation therapy treatment
`plan is formed based on the location and orientation of the
`lesion and surrounding structures in an initial computerized
`tomography or magnetic resonance image. However,
`the
`location and orientation of the lesion may vary during the
`course of treatment from that used to form the radiation
`
`in each treatment
`therapy treatment plan. For example,
`session, systematic and/or random variations in patient setup
`(termed interfraction setup errors) and in the location of the
`lesion relative to surrounding anatomy (termed interfraction
`organ motion errors) can each change the location and
`orientation of the lesion at the time of treatment compared
`to that assumed in the radiation therapy treatment plan.
`Furthermore, the location and orientation of the lesion can
`vary during a single treatment session (resulting in intrafrac-
`tion errors) due to normal biological processes, such as
`breathing, peristalsis, etc. In the case of radiation treatment
`of a patient’s prostate, it is necessary to irradiate a volume
`that is enlarged by a margin to guarantee that the prostate
`always receives a prescribed dose due to uncertainties in
`patient positioning and daily movement of the prostate
`within the patient. Significant dose escalation may be pos-
`sible if these uncertainties could be reduced from current
`
`levels (~10 mm) to 2-3 mm.
`Applying large margins necessarily increases the volume
`of normal
`tissue that
`is irradiated,
`thereby limiting the
`
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`maximum dose that can be delivered to the lesion without
`resulting in complication in normal structures. There is
`strong reason to believe that increasing the dose delivered to
`the lesion can result in more efficacious treatment. However,
`it is often the case that the maximum dose that can be safely
`delivered to the target volume is limited by the associated
`dose to surrounding normal structures incurred through the
`use of margins. Therefore, if one’s knowledge of the loca-
`tion and orientation of the lesion at the time of treatment can
`
`be increased, then margins can be reduced, and the dose to
`the target volume can be increased without increasing the
`risk of complication in normal tissues.
`A number of techniques have been developed to reduce
`uncertainty associated with systematic and/or random varia-
`tions in lesion location resulting from interfraction and
`intrafraction errors. These include patient immobilization
`techniques (e.g., masks, body casts, bite blocks, etc.), off-
`line review processes (e.g., weekly port films, population-
`based or individual-based statistical approaches, repeat com-
`puterized tomography scans, etc.), and on-line correction
`strategies (e.g., pre-ports, MV or kV radiographic or fluo-
`roscopic monitoring, video monitoring, etc.).
`It is believed that the optimum methodology for reducing
`uncertainties associated with systematic and/or random
`variations in lesion location can only be achieved through
`using an on-line correction strategy that involves employing
`both on-line imaging and guidance system capable of detect-
`ing the target volume, such as the prostate, and surrounding
`structures with high spatial accuracy.
`An on-line imaging system providing suitable guidance
`has several requirements if it is to be applied in radiotherapy
`of this type. These requirements include contrast sensitivity
`sufficient to discern soft-tissue; high spatial resolution and
`low geometric distortion for precise localization of soft-
`tissue boundaries; operation within the environment of a
`radiation treatment machine;
`large field-of-view (FOV)
`capable of imaging patients up to 40 cm in diameter; rapid
`image acquisition (within a few minutes); negligible harm to
`the patient from the imaging procedure (e.g., dose much less
`than the treatment dose); and compatibility with integration
`into an external beam radiotherapy treatment machine.
`Several examples of known on-line imaging systems are
`described below. For example, strategies employing x-ray
`projections of the patient (e.g., film, electronic portal imag-
`ing devices, kV radiography/fluoroscopy, etc.)
`typically
`show only the location of bony anatomy and not soft-tissue
`structures. Hence, the location of a soft-tissue target volume
`must be inferred from the location of bony landmarks. This
`obvious shortcoming can be alleviated by implanting radio-
`opaque markers on the lesion; however, this technique is
`invasive and is not applicable to all treatment sites. Tomo-
`graphic imaging modalities (e.g., computerized tomography,
`magnetic resonance, and ultrasound), on the other hand, can
`provide information regarding the location of soft-tissue
`target volumes. Acquiring computerized tomography images
`at the time of treatment is possible, for example, by incor-
`porating a computerized tomography scanner into the radia-
`tion therapy environment (e.g., with the treatment table
`translated between the computerized tomography scanner
`gantry and the radiation therapy gantry along rails) or by
`modifying the treatment machine to allow computerized
`tomography scanning. The former approach is a fairly
`expensive solution, requiring the installation of a dedicated
`computerized tomography scanner in the treatment room.
`The latter approach is possible, for example, by modifying
`a computer tomography scanner gantry to include mecha-
`nisms for radiation treatment delivery, as in systems for
`
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`US 6,842,502 B2
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`3
`tomotherapy. Finally, soft-tissue visualization of the target
`volume can in some instances be accomplished by means of
`an ultrasound imaging system attached in a well-defined
`geometry to the radiation therapy machine. Although this
`approach is not applicable to all treatment sites, it is fairly
`cost-effective and has been used to illustrate the benefit of
`on-line therapy guidance.
`As illustrated in FIGS. 1(a)—(c), a typical radiation
`therapy system 100 incorporates a 4-25 MV medical linear
`accelerator 102, a collimator 104 for collimating and shap-
`ing the radiation field 106 that is directed onto a patient 108
`who is supported on a treatment
`table 110 in a given
`treatment position. Treatment involves irradiation of a lesion
`112 located within a target volume with a radiation beam 114
`directed at the lesion from one or more angles about the
`patient 108. An imaging device 116 may be employed to
`image the radiation field 118 transmitted through the patient
`108 during treatment. The imaging device 116 for imaging
`the radiation field 118 can be used to verify patient setup
`prior to treatment and/or to record images of the actual
`radiation fields delivered during treatment. Typically, such
`images suffer from poor contrast resolution and provide, at
`most, visualization of bony landmarks relative to the field
`edges.
`Another example of a known on-line imaging system used
`for reducing uncertainties associated with systematic and/or
`random variations in lesion location is an X-ray cone-beam
`computerized tomography system. Mechanical operation of
`a cone beam computerized tomography system is similar to
`that of a conventional computerized tomography system,
`with the exception that an entire volumetric image is
`acquired through a single rotation of the source and detector.
`This is made possible by the use of a two-dimensional (2-D)
`detector, as opposed to the 1-D detectors used in conven-
`tional computerized tomography. There are constraints asso-
`ciated with image reconstruction under a cone-beam geom-
`etry. However, these constraints can typically be addressed
`through innovative source and detector trajectories that are
`well known to one of ordinary skill in the art.
`As mentioned above, a cone beam computerized tomog-
`raphy system reconstructs three-dimensional (3-D) images
`from a plurality of two-dimensional (2-D) projection images
`acquired at various angles about the subject. The method by
`which the 3-D image is reconstructed from the 2-D projec-
`tions is distinct from the method employed in conventional
`computerized tomography systems. In conventional com-
`puterized tomography systems, one or more 2-D slices are
`reconstructed from one-dimensional (1-D ) projections of
`the patient, and these slices may be “stacked” to form a 3-D
`image of the patient.
`In cone beam computerized
`tomography, a fully 3-D image is reconstructed from a
`plurality of 2-D projections. Cone beam computerized
`tomography offers a number of advantageous
`characteristics, including: formation of a 3-D image of the
`patient from a single rotation about the patient (whereas
`conventional computerized tomography typically requires a
`rotation for each slice); spatial resolution that is largely
`isotropic (whereas in conventional computerized tomogra-
`phy the spatial resolution in the longitudinal direction is
`typically limited by slice thickness); and considerable flex-
`ibility in the imaging geometry. Such technology has been
`employed in applications such as micro-computerized
`tomography, for example, using a kV x-ray tube and an x-ray
`image intensifier tube to acquire 2-D projections as the
`object to be imaged is rotated, e.g., through 180° or 360°.
`Furthermore, cone beam computerized tomography has been
`used successfully in medical applications such as comput-
`
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`erized tomography angiography, using a kV x-ray tube and
`an x-ray image intensifier tube mounted on a rotating C-arm.
`The development of a kV cone-beam computerized
`tomography imaging system for on-line tomographic guid-
`ance has been reported. The system consists of a kV x-ray
`tube and a radiographic detector mounted on the gantry of a
`medical linear accelerator. The imaging detector is based on
`a low-noise charge-coupled device (CCD) optically coupled
`to a phosphor screen. The poor optical coupling efficiency
`(-104) between the phosphor and the CCD significantly
`reduces the detective quantum efficiency (DQE) of the
`system. While this system is capable of producing cone
`beam computerized tomography images of sufficient quality
`to visualize soft
`tissues relevant
`to radiotherapy of the
`prostate, the low DQE requires imaging doses that are a
`factor of 3-4 times larger than would be required for a
`system with an efficient coupling (e.g. -50% or better)
`between the screen and detector.
`
`Another example of a known auxiliary cone beam com-
`puterized tomography imaging system is shown in FIG. 2.
`The auxiliary cone beam computerized tomography imaging
`system 200 replaces the CCD-based imager of FIGS. 1(a)
`—(c) with a fiat-panel imager. In particular,
`the imaging
`system 200 consists of a kilovoltage x-ray tube 202 and a flat
`panel imager 204 having an array of amorphous silicon
`detectors that are incorporated into the geometry of a
`radiation therapy delivery system 206 that includes an MV
`x-ray source 208. A second fiat panel
`imager 210 may
`optionally be used in the radiation therapy delivery system
`206. Such an imaging system 200 could provide projection
`radiographs and/or continuous fluoroscopy of the lesion 212
`within the target volume as the patient 214 lies on the
`treatment table 216 in the treatment position. If the geometry
`of the imaging system 200 relative to the system 206 is
`known, then the resulting kV projection images could be
`used to modify patient setup and improve somewhat the
`precision of radiation treatment. However, such a system
`200 still would not likely provide adequate visualization of
`soft-tissue structures and hence be limited in the degree to
`which it could reduce errors resulting from organ motion.
`Accordingly, it is an object of the present invention to
`generate KV projection images in a cone beam computer-
`ized tomography system that provide adequate visualization
`of soft-tissue structures so as to reduce errors in radiation
`
`treatment resulting from organ motion.
`
`BRIEF SUMMARY OF THE INVENTION
`
`One aspect of the present invention regards a radiation
`therapy system that includes a radiation source that moves
`about a path and directs a beam of radiation towards an
`object and a cone-beam computer tomography system. The
`cone-beam computer tomography system includes an x-ray
`source that emits an x-ray beam in a cone-beam form
`towards an object to be imaged and an amorphous silicon
`fiat-panel imager receiving x-rays after they pass through the
`object,
`the imager providing an image of the object. A
`computer is connected to the radiation source and the cone
`beam computerized tomography system, wherein the com-
`puter receives the image of the object and based on the
`image sends a signal to the radiation source that controls the
`path of the radiation source.
`Asecond aspect of the present invention regards a method
`of treating an object with radiation that includes moving a
`radiation source about a path, directing a beam of radiation
`from the radiation source towards an object and emitting an
`x-ray beam in a cone beam form towards the object. The
`
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`US 6,842,502 B2
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`5
`method further includes detecting x-rays that pass through
`the object due to the emitting an x-ray beam with an
`amorphous silicon fiat-panel imager, generating an image of
`the object from the detected x-rays and controlling the path
`of the radiation source based on the image.
`Each aspect of the present invention provides the advan-
`tage of generating KV projection images in a cone beam
`computerized tomography system that provide adequate
`visualization of soft-tissue structures so as to reduce errors
`
`in radiation treatment resulting from organ motion.
`Each aspect of the present invention provides an appara-
`tus and method for improving the precision of radiation
`therapy by incorporating a cone beam computerized tomog-
`raphy imaging system in the treatment room, the 3-D images
`from which are used to modify current and subsequent
`treatment plans.
`Each aspect of the present invention represents a signifi-
`cant shift in the practice of radiation therapy. Not only does
`the high-precision,
`image-guided system for radiation
`therapy address the immediate need to improve the prob-
`ability of cure through dose escalation, but it also provides
`opportunity for broad innovation in clinical practice.
`Each aspect of the present invention may permit alterna-
`tive fractionation schemes, permitting shorter courses of
`therapy and allowing improved integration in adjuvant
`therapy models.
`Each aspect of the present invention provides valuable
`imaging information for directing radiation therapy also
`provides an explicit 3-D record of intervention against
`which the success or failure of treatment can be evaluated,
`offering new insight into the means by which disease is
`managed.
`Additional objects, advantages and features of the present
`invention will become apparent from the following descrip-
`tion and the appended claims when taken in conjunction
`with the accompanying drawings.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`FIGS. 1(a)—(c) schematically show the geometry and
`operation of a conventional radiation therapy apparatus;
`FIG. 2 schematically shows a perspective view of a
`known radiation therapy apparatus including an auxiliary
`apparatus for cone beam computerized tomography imag-
`ing;
`FIG. 3 is a diagrammatic view of a bench-top cone beam
`computerized tomography system employing a fiat-panel
`imager, according to a first embodiment of the present
`invention;
`FIG. 4 is a schematic illustration of the geometry and
`procedures of the cone beam computerized tomography
`system shown in FIG. 3;
`FIGS. 5(a)—5(LO are graphs depicting the fundamental
`performance characteristics of the fiat-panel imager used in
`the cone beam computerized tomography system of FIG. 3;
`FIGS. 6(a)—6(LO show various objects used in tests to
`investigate the performance of the cone beam computerized
`tomography system of