(19) United States
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`(12) Patent Application Publication (10) Pub. No.: US 2004/0116804 A1
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`Mostafavi
`(43) Pub. Date:
`Jun. 17, 2004
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`US 20040116804A1
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`(76)
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`(54) METHOD AND SYSTEM FOR RADIATION
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`APPLICATION
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`Inventor: Hassan Mostafavi, Los Altos, CA (US)
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`Correspondence Address:
`BINGHAM, MCCUTCHEN LLP
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`THREE EMBARCADERO, SUITE 1800
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`SAN FRANCISCO, CA 94111-4067 (US)
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`which is a continuation of application No. 09/178,
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`384, filed on Oct. 23, 1998, now abandoned.
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`(60) Provisional application No. 60/415,992, filed on Oct.
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`5, 2002.
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`Publication Classification
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`(51)
`Int. Cl.7 ..................................................... .. A61B 5/05
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`(52) U.S.Cl.
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`ABSTRACT
`(57)
`A method for generating one or more images includes
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`collecting data samples representative of a motion of an
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`object, acquiring image data of at least a part of the object
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`over a time interval, synchronizing the data samples and the
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`image data to a common time base, and generating one or
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`more images based on the synchronized image data. A
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`method for generating one or more images includes acquir-
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`ing image data of at least a part of an object over a time
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`interval, associating the image data with one or more phases
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`of a motion cycle, and constructing one or more images
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`using the image data that are associated with the respective
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`one or more phases.
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`(21) Appl. No.:
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`10/678,741
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`(22)
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`Filed:
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`Oct. 3, 2003
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`Related U.S. Application Data
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`(63) Continuation-in-part of application No. 09/893,122,
`filed on Jun. 26, 2001, which is a continuation-in-part
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`of application No. 09/178,383, filed on Oct. 23, 1998,
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`now Pat. No. 6,621,889, and which is a continuation-
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`in-part of application No. 09/178,385, filed on Oct.
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`23, 1998, now Pat. No. 6,279,579, and which is a
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`continuation-in-part of application No. 09/712,724,
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`filed on Nov. 14, 2000, now Pat. No. 6,690,965,
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`Page 1 of 41
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`Elekta Exhibit 1036
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`Jun. 17, 2004 Sheet 2 of 22
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`300
`\\
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`BEAM ON
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`BEAM HOLD
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`4
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`TIME
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`20
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`FIG. 3
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`START
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`402
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`DEFINE BOUNDARIES OF
`TREATMENT INTERVALS
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`MEASURE PATIENT
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`MOTION
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`OUTSIDE BOUNDARIES
`OF TREATMENT
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`INTERVALS?
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`Page 4 of 41
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`SET GATING SIGNAL
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`THRESHOLD TO
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`I3 RADIATION BEAM
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`BEING APPLIED?
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`SET GATING SIGNAL
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`THRESHOLD TO
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`473
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`IS RADIATION BEAM NOT
`BEING APPLIED?
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`YES
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`HOLD RADIATION
`BEAM SOURCE
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`4 7 4
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`APPLY RADIATION
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`FIG. 4
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`Jun. 17, 2004 Sheet 4 of 22
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`FIG. 5
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`502
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`GENERATE DATA FOR
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`PHYSIOLOGICAL
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`504“
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`MATCHING ON DATA
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`DEGREE OF MATCH
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`POINT OF MATCH
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`REPETITIVENESS
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`DEVIATION DETECTED
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`DOES PREDICTED
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`VALUE MATCH ACTUAL DATA
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`VALUE WITHIN A THRESHOLD
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`DEVIATION NOT
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`DETECTED
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`Jun. 17, 2004 Sheet 5 of 22
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`708
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`502 FIG. 6a
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`””\
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`mg
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`FIG. 7a
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`FIG 7b
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`Jun. 17, 2004 Sheet 6 of 22
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`Jun. 17, 2004 Sheet 7 of 22
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` FIG.123
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`Jun. 17, 2004 Sheet 8 of 22
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`Patent Application Publication
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`Jun. 17, 2004 Sheet 9 of 22
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`7302
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`FIG. I133
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`Jun. 17, 2004 Sheet 10 of 22
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`1360
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`Jun. 17, 2004 Sheet 11 of 22
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`Jun. 17, 2004 Sheet 12 of 22
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`Page 15 of 41
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`FIG. 15
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`Jun. 17, 2004 Sheet 15 of 22
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`3D POSITION INDICATOR
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`2012
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`Page 20 of 41
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`Page 20 of 41
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`

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`Patent Application Publication
`
`Jun. 17, 2004 Sheet 20 of 22
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`US 2004/0116804 A1
`
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`Page 21 of 41
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`Page 21 of 41
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`

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`Patent Application Publication
`
`Jun. 17, 2004 Sheet 21 of 22
`
`US 2004/0116804 A1
`
`Page 22 of 41
`
`Page 22 of 41
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`

`
`Patent Application Publication
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`Jun. 17, 2004 Sheet 22 of 22
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`US 2004/0116804 A1
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`Page 23 of 41
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`Page 23 of 41
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`

`
`US 2004/0116804 A1
`
`Jun. 17, 2004
`
`METHOD AND SYSTEM FOR RADIATION
`APPLICATION
`
`RELATED APPLICATION DATA
`
`[0001] This application claims priority to U.S. Provisional
`Patent Application Serial No. 60/415,992 filed Oct. 5, 2002,
`the entire disclosure of which is hereby expressly incorpo-
`rated by reference, and is a continuation-in-part of U.S.
`patent application Ser. No. 09/893,122 filed Jun. 26, 2001,
`which is a continuation-in-part of U.S. patent application
`Ser. No. 09/178,383 filed Oct. 23, 1998, 09/178,385 filed
`Oct. 23, 1998, and 09/712,724 filed Nov. 14, 2000, which is
`a continuation of U.S. patent application Ser. No. 09/178,
`384 filed Oct. 23, 1998, the disclosures of all of which are
`hereby expressly incorporated by reference in their entirety.
`
`BACKGROUND OF THE INVENTION
`
`[0002]
`
`1. Field of the Invention
`
`[0003] The present invention relates to medical methods
`and systems. More particularly, the invention relates to a
`method and system for physiological gating.
`
`[0004]
`
`2. Background of the Invention
`
`[0005] Many types of medical procedures involve devices
`and machines that act upon a particular portion of a patient
`body. For example, radiation therapy involves medical pro-
`cedures that selectively expose certain areas of a human
`body, such as cancerous tumors, to high doses of radiation.
`The intent of the radiation therapy is to irradiate the targeted
`biological tissue such that the harmful tissue is destroyed. In
`certain types of radiotherapy, the irradiation volume can be
`restricted to the size and shape of the tumor or targeted tissue
`region to avoid infiicting unnecessary radiation damage to
`healthy tissue. Conformal therapy is a radiotherapy tech-
`nique that is often employed to optimize dose distribution by
`conforming the treatment volume more closely to the tar-
`geted tumor.
`
`[0006] Other medical procedures are also directed to spe-
`cific portions of a patient body. For example, radiation
`imaging typically directs radiation only to the portion of a
`patient body to be imaged. 3-dimensional imaging applica-
`tions such as computed topography (CT), PET, and MRI
`scans also are directed to specific portions of a patient body.
`
`[0007] Normal physiological movement represents a limi-
`tation in the clinical planning and delivery of medical
`procedures to a patient body. Normal physiological move-
`ment, such as respiration or heart movement, can cause a
`positional movement of the body portion undergoing treat-
`ment, measurement, or imaging. With respect to radiation
`therapy, if the radiation beam has been shaped to conform
`the treatment volume to the exact dimensions of a tumor,
`then movement of that tumor during treatment could result
`in the radiation beam not being sufficiently sized or shaped
`to fully cover the targeted tumoral
`tissue. For imaging
`applications, normal physiological movement could result in
`blurred images or image artifacts.
`
`[0008] One approach to this problem involves physiologi-
`cal gating of the medical procedure, such as gating of a
`radiation beam during treatment, with the gating signal
`synchronized to the movement of the patient’s body. In this
`approach,
`instruments are utilized to measure the physi-
`
`Page 24 of 41
`
`ological state and/or movement of the patient. Respiration
`has been shown to cause movements in the position of a lung
`tumor in a patient’s body; if radiotherapy is being applied to
`the lung tumor, then a temperature sensor, strain gauge,
`preumotactrograph, or optical imaging system can be uti-
`lized to measure the patient during a respiration cycle. These
`instruments can produce a signal indicative of the movement
`of the patient during the respiratory cycle. The radiation
`beam can be gated based upon certain threshold amplitude
`levels of the measured respiratory signal, such that
`the
`radiation beam is disengaged or stopped during particular
`time points in the respiration signal
`that correspond to
`excessive movement of the lung tumor.
`
`[0009] Many approaches to physiological gating are reac-
`tive, that is, these approaches utilize gating methods that
`slavishly react to measured levels of physiological move-
`ments. One drawback to reactive gating systems is that the
`measured physiological movement may involve motion that
`that is relatively fast when compared to reaction time of the
`imaging or therapy device that is being gated. Thus, a purely
`reactive gating system may not be able to react fast enough
`to effectively gate the applied radiation. For example, the
`gating system may include a switch or trigger for gating
`radiation which requires a given time period At to fully
`activate. If the delay period At is relatively long compared
`to the measured physiological motion cycle, then a system
`employing such a trigger in a reactive manner may not be
`able to effectively gate the radiation at appropriate time
`points to minimize the effect of motion.
`
`[0010] Therefore, there is a need for a system and method
`to address these and other problems of the related art. There
`is a need for a method and system for physiological gating
`which is not purely reactive to measure physiological move-
`ment signals.
`SUMMARY OF THE INVENTION
`
`In accordance with one embodiment of the inven-
`[0011]
`tion, a method for generating one or more images includes
`collecting data samples representative of a motion of an
`object, acquiring image data of at least a part of the object
`over a time interval, synchronizing the data samples and the
`image data to a common time base, and generating one or
`more images based on the synchronized image data.
`
`In accordance with another embodiment of the
`[0012]
`invention, a method for generating one or more images
`includes acquiring image data of at least a part of an object
`over a time interval, associating the image data with one or
`more phases of a motion cycle, and constructing one or more
`images using the image data that are associated with the
`respective one or more phases.
`
`[0013] Other aspects and features of the invention will be
`evident from reading the following detailed description of
`the preferred embodiments, which are intended to illustrate,
`not limit, the invention.
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0014] The accompanying drawings are included to pro-
`vide a further understanding of the invention and, together
`with the Detailed Description, serve to explain the principles
`of the invention.
`
`[0015] FIG. 1 depicts the components of a system for
`physiological gating according to an embodiment of the
`invention.
`
`Page 24 of 41
`
`

`
`US 2004/0116804 A1
`
`Jun. 17, 2004
`
`[0016] FIG. 2 depicts an example of a respiratory motion
`signal chart.
`
`[0040] FIG. 25 shows several graphs illustrating a method
`of sorting image data.
`
`[0017] FIG. 3 depicts a motion signal chart and a gating
`signal chart.
`
`[0041] FIG. 26 is a flow chart illustrating a method of
`sorting image data.
`
`[0018] FIG. 4 is a flowchart showing process actions
`performed in an embodiment of the invention.
`
`[0019] FIG. 5 is a flowchart showing process actions for
`detecting and predicting regular physiological movements.
`
`[0020] FIG. 6a depicts a side view an embodiment of a
`camera and illuminator that can be utilized in the invention.
`
`[0021] FIG. 6b depicts a front view of the camera of FIG.
`6a.
`
`[0022] FIG. 7a depicts a retro-reflective marker according
`to an embodiment of the invention.
`
`[0023] FIG. 7b depicts a cross-sectional view of the
`retro-reflective marker of FIG. 7a.
`
`[0024] FIG. 8 depicts an apparatus for making a retro-
`reflective marker.
`
`[0025] FIG. 9 depicts a phase chart synchronized with a
`gating signal chart.
`
`[0026] FIG. 10 depicts an embodiment of a hemispherical
`marker block.
`
`[0027] FIG. 11 depicts an embodiment of a cylindrical
`marker block.
`
`[0028] FIG. 12a depicts a system for physiological gating
`according to an embodiment of the invention.
`
`[0029] FIG. 12b illustrates an interface for viewing, con-
`trolling, and/or planning a gating plan.
`
`[0030] FIG. 13a shows a flowchart of a process for
`detecting periodicity or lack of periodicity according to an
`embodiment of the invention.
`
`[0031] FIG. 13b illustrates sample trains according to an
`embodiment of the invention.
`
`[0032] FIG. 13c is an example chart of showing phase and
`amplitude for a periodic signal.
`
`[0033] FIG. 13d shows an example of a periodic signal
`amplitude-phase histogram chart.
`
`[0034] FIGS. 14a, 14b, and 14c depict embodiments of a
`marker block.
`
`[0035] FIG. 15 shows a flowchart of a process for esti-
`mating position and orientation of a marker block according
`to an embodiment of the invention.
`
`[0036] FIGS. 16 and 17 show embodiments of slider
`interfaces according to embodiments of the invention.
`
`[0037] FIG. 18 shows a system for positioning a patient
`among multiple devices according to an embodiment of the
`invention.
`
`[0038] FIG. 19 is a diagram of a computer hardware
`system with which the present
`invention can be imple-
`mented.
`
`[0039] FIGS. 20-24 show interfaces for controlling, dis-
`playing, and planning according to embodiments of the
`invention.
`
`Page 25 of 41
`
`DESCRIPTION OF THE ILLUSTRATED
`EMBODIMENTS
`
`[0042] An aspect of an embodiment of the present inven-
`tion comprises a method for detecting and predictively
`estimating regular cycles of physiological activity or move-
`ment. Also disclosed are embodiments of systems and
`devices for patient positioning, positioning monitoring,
`motion monitoring, and physiological gating of medical
`procedures such as imaging and radiation therapy. The
`systems and methods of the invention can be employed for
`any regular physiological activity, including for example,
`the respiratory or cardiac cycles, and for monitoring tem-
`porary breath-hold state of the patient.
`
`[0043] System for Patient Position Monitoring and Physi-
`ological Gating
`
`[0044] FIG. 1 depicts the components of an embodiment
`of a system 100 for physiological gating, position monitor-
`ing, and motion monitoring, in which data representative of
`physiological activity is collected with an optical imaging
`apparatus. For the purposes of illustration, system 100 is
`particularly described with reference to physiological gating
`of radiation therapy. Thus, system 100 comprises a radiation
`beam source 102 such as a conventional linear accelerator
`
`which is positionally configured to direct a radiation beam at
`a patient 106 located on treatment table 104. It is noted,
`however, that system 100 can also be applied to gate other
`medical procedures, such as gating for CT imaging appli-
`cations or non-radioactive imaging applications such as
`MRI.
`
`In system 100 for physiological gating, a switch
`[0045]
`116 is operatively coupled to the radiation beam source 102.
`Switch 116 can be operated to suspend the application of the
`radiation beam at patient 106. In an embodiment, switch 116
`is part of the mechanical and electrical structure of radiation
`beam source 102. Alternatively, switch 116 comprises an
`external apparatus that is connected to the control electron-
`ics of radiation beam source 102. Switch 116 may also
`comprise a software-based control mechanism.
`
`[0046] An optical or video image apparatus, such as video
`camera 108, is aimed such that at least part of the patient 106
`is within the camera’s field of view. Camera 108 monitors
`
`patient 106 for motion relating to the particular physiologi-
`cal activity being measured. By way of example, if respi-
`ration movements of the patient are being monitored, then
`camera 108 is configured to monitor the motion of the
`patient’s chest. According to an embodiment, camera 108 is
`placed on the ceiling, wall, or other support structure with its
`axis tilted down between 20 and 70 degrees relative to the
`horizontal longitudinal axis of the patient 106. For measure-
`ment of respiration motion, the video image field of view is
`preferably set to view an approximately 30 cm by 30 cm area
`of the patient’s chest. For purposes of illustration only, a
`single camera 108 is shown in FIG. 1. However, the number
`of cameras 108 employed in the present
`invention can
`exceed that number, and the exact number to be used in the
`invention depends upon the particular application to which
`it is directed.
`
`Page 25 of 41
`
`

`
`US 2004/0116804 A1
`
`Jun. 17, 2004
`
`In an embodiment, one illumination source per
`[0047]
`camera (which is an infrared source in the preferred embodi-
`ment) projects light at the patient 106 on treatment table 104.
`The generated light is reflected from one or more landmarks
`on the patient’s body. The camera 108, which is directed at
`patient 106, captures and detects the reflected light from the
`one or more landmarks. The landmarks are selected based
`
`upon the physiological activity being studied. For respira-
`tion measurements, the landmarks are preferably located on
`one or more locations on the patient’s chest.
`
`[0048] The output signals of camera 108 are sent to a
`computer 110 or other type of processing unit having the
`capability to receive video images. According to a particular
`embodiment, computer 110 comprises an Intel Pentium-
`based processor running Microsoft Windows NT or 2000
`and includes a video frame grabber card having a separate
`channel for each video source utilized in the system. The
`images recorded by camera 108 are sent to computer 110 for
`processing. If camera 108 produces an analog output, the
`frame grabber converts the camera signals to a digital signal
`prior to processing by computer 110. Based upon the video
`signals received by computer 110, control signals can be sent
`from computer 110 to operate switch 116.
`
`[0049] According to one embodiment, one or more pas-
`sive markers 114 are located on the patient in the area to be
`detected for movement. Each marker 114 preferably com-
`prises a reflective or retro-reflective material that can reflect
`light, whether in the visible or invisible wavelengths. If the
`illumination source is co-located with camera 108,
`then
`marker 114 preferably comprises a retro-reflective material
`that reflects light mostly in the direction of the illumination
`source. Alternatively, each marker 114 comprises its own
`light source. The marker 114 is used in place of or in
`conjunction with physical landmarks on the patient’s body
`that is imaged by the camera 108 to detect patient move-
`ment. Markers 114 are preferably used instead of body
`landmarks because such markers 114 can be detected and
`
`tracked more accurately via the video image generated by
`camera 108. Because of the reflective or retro-reflective
`
`the markers 114
`qualities of the preferred markers 114,
`inherently provide greater contrast in a video image to a light
`detecting apparatus such as camera 108, particularly when
`the camera 108 and illumination source are co-located.
`
`[0050] Utilizing a video or optical based system to track
`patient movement provides several advantages. First, a
`video or optical based system provides a reliable mechanism
`for repeating measurement results between uses on a given
`patient. Second, the method of the invention is noninvasive,
`and even if markers are used, no cables or connections must
`be made to the patient. Moreover, if the use of markers is
`impractical, the system can still be utilized without markers
`by performing measurements of physiological activity
`keyed to selected body landmarks. Finally, the method of the
`invention is more accurate because it is 110 based upon
`absolute measurement of external anatomical physical
`movement. The present patient monitoring system is par-
`ticularly suitable to track motion and position of patients for
`which intrusive/cumbersome equipment cannot or should
`not be used. For example, the present optical-based system
`is suitable for monitoring the movement and position of
`infants.
`
`[0051] Apossible inefficiency in tracking the markers 114
`is that the marker may appear anywhere on the video frame,
`
`Page 26 of 41
`
`and all of the image elements of the video frame may have
`to be examined to determine the location of the marker 114.
`Thus, in an embodiment, the initial determination of loca-
`tions for the marker 114 involves an examination of all of the
`
`image elements in the video frame. If the video frame
`comprise 640 by 480 image elements,
`then all 307200
`(640*480) image elements are initially examined to find the
`location of the markers 114.
`
`[0052] For real-time tracking of the marker 114, examin-
`ing every image element for every video frame to determine
`the location of the marker 114 in real-time could consume a
`
`significant amount of system resources. Thus, in an embodi-
`ment, the real-time tracking of marker 114 can be facilitated
`by processing a small region of the video frame, referred to
`herein as a “tracking gate”, that is placed based on estima-
`tion of the location of the already-identified marker 114 in a
`previous video frame. The previously determined location of
`a marker 114 defined in the previous video frame is used to
`define an initial search range (i.e., the tracking gate) for that
`same marker in real-time. The tracking gate is a relatively
`small portion of the video frame that, in one embodiment, is
`centered at the previous location of the marker 114. The
`tracking gate is expanded only if the tracking algorithm can
`not locate the marker 114 within the gate. As an example,
`consider the situation when the previously determined loca-
`tion of a particular marker is image element (50, 50) in a
`video frame. If the tracking gate is limited to a 50 by 50 area
`of the video frame, then the tracking gate for this example
`would comprise the image elements bound within the area
`defined by the coordinates (25,25), (25, 75), (75, 25), and
`(75, 75). The other portions of the video frame are searched
`only if the marker 106 is not found within this tracking gate.
`
`[0053] The video image signals sent from camera 108 to
`computer 110 are used to generate and track motion signals
`representative of the movement of marker 114 and/or land-
`mark structures on the patient’s body. FIG. 2 depicts an
`example of a motion signal chart 200 for respiratory move-
`ment that contains information regarding the movement of
`marker 114 during a given measurement period. The hori-
`zontal axis represents points in time and the vertical axis
`represents the relative location or movement of the marker
`114. According to an embodiment, the illustrated signal in
`FIG. 2 comprises a plurality of discrete data points plotted
`along the motion signal chart 200.
`
`[0054] FIGS. 6a and 6b depict an embodiment of a
`camera 108 that can used in the present invention to opti-
`cally or visually collect data representative of physiological
`movement. Camera 108 is a charge-couple device (“CCD”)
`camera having one or more photoelectric cathodes and one
`or more CCD devices. A CCD device is a semiconductor
`
`device that can store charge in local areas, and upon appro-
`priate control signals,
`transfers that charge to a readout
`point. When light photons from the scene to be imaged are
`focussed on the photoelectric cathodes, electrons are liber-
`ated in proportion to light intensity received at the camera.
`The electrons are captured in charge buckets located within
`the CCD device. The distribution of captured electrons in the
`charge buckets represents the image received at the camera.
`The CCD transfers these electrons to an analog-to-digital
`converter. The output of the analog-to-digital converter is
`sent to computer 410 to process the video image and to
`calculate the positions of the retro-reflective markers 406.
`According to an embodiment of the invention, camera 108
`
`Page 26 of 41
`
`

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`US 2004/0116804 A1
`
`Jun. 17, 2004
`
`is a monochrome CCD camera having RS-170 output and
`640x480 pixel resolution. Alternatively, camera 408 can
`comprise a CCD camera having CCIR output and 756x567
`pixel resolution.
`
`In a particular embodiment of the invention, an
`[0055]
`infra-red illuminator 602 (“IR illuminator”) is co-located
`with camera 108. IR illuminator 602 produces one or more
`beams of infrared light that is directed in the same direction
`as camera 108. IR illuminator 602 comprises a surface that
`is ringed around the lens 606 of camera body 608. The
`surface of IR illuminator 602 contains a plurality of indi-
`vidual LED elements 604 for producing infrared light. The
`LED elements 604 are organized as one or more circular or
`spiral patterns on the IR illuminator 602 surrounding the
`camera lens 606. Infrared filters that may be part of the
`camera 108 are removed or disabled to increase the camera’s
`
`sensitivity to infrared light.
`
`[0056] According to an embodiment, digital video record-
`ings of the patient in a session can be recorded via camera
`108. The same camera 108 used for tracking patient move-
`ment can be used to record video images of the patient for
`future reference. A normal ambient light image sequence of
`the patient can be obtained in synchronization with the
`measured movement signals of markers 114.
`[0057] FIGS. 7a and 7b depict an embodiment of a
`retro-reflective marker 700 that can be employed within the
`present invention. Retro-reflective marker 700 comprises a
`raised reflective surface 702 for reflecting light. Raised
`reflective surface 702 comprises a semi-spherical shape such
`that light can be reflected regardless of the input angle of the
`light source. A flat surface 704 surrounds the raised reflec-
`tive surface 702. The underside of flat surface 704 provides
`a mounting area to attach retro-reflective marker 700 to
`particular locations on a patient’s body. According to an
`embodiment, retro-reflective marker 700 is comprised of a
`retro-reflective material 3M#7610WS available from 3M
`
`Corporation. In an embodiment, marker 700 has a diameter
`of approximately 0.5 cm and a height of the highest point of
`raised reflective surface 702 of approximately 0.1 cm.
`Alternatively, a marker can comprise a circular, spherical, or
`cylindrical shape.
`[0058] FIG. 8 depicts an apparatus 802 that can be
`employed to manufacture retro-reflective markers 700.
`Apparatus 802 comprises a base portion 804 having an
`elastic ring 806 affixed thereto. Elastic ring 806 is attached
`to bottom mold piece 808 having a bulge protruding from its
`center. A control lever 810 can be operated to move top
`portion 812 along support rods 814. Top portion 812 com-
`prises a spring-loaded top mold piece 814. Top mold piece
`814 is formed with a semi-spherical cav