U.S. patent application number 13/016718 was filed with the patent office on 2012-04-26 for method and apparatus for reconstructing image projections.
This patent application is currently assigned to Medtronic Navigation, Inc.. Invention is credited to Patrick A. Helm, Shuanghe Shi.
Application Number | 20120099768 13/016718 |
Document ID | / |
Family ID | 44906430 |
Filed Date | 2012-04-26 |
United States Patent
Application |
20120099768 |
Kind Code |
A1 |
Helm; Patrick A. ; et
al. |
April 26, 2012 |
Method and Apparatus for Reconstructing Image Projections
Abstract
A method and system is disclosed for acquiring image data of a
subject. The image data can be collected with an imaging system
having a detector able to move relative to the subject. A contrast
agent can be injected into the subject and image data can be
acquired with the contrast agent in various phases of the subject.
A volumetric model of multiple phases can be reconstructed selected
reconstruction techniques.
Inventors: |
Helm; Patrick A.; (Milton,
MA) ; Shi; Shuanghe; (Southborough, MA) |
Assignee: |
Medtronic Navigation, Inc.
Louisville
CO
|
Family ID: |
44906430 |
Appl. No.: |
13/016718 |
Filed: |
January 28, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
12908189 |
Oct 20, 2010 |
|
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|
13016718 |
|
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Current U.S.
Class: |
382/128 ; 378/87;
600/431 |
Current CPC
Class: |
A61B 6/4405 20130101;
A61B 6/4476 20130101; A61B 6/507 20130101; G06T 11/005 20130101;
A61B 6/481 20130101; G06T 2211/412 20130101; G01N 2223/419
20130101; A61B 6/02 20130101; A61B 6/4085 20130101; A61B 6/504
20130101; G06T 2211/404 20130101; A61B 6/469 20130101; A61B 6/545
20130101; G06T 2207/10081 20130101; G06T 2207/30048 20130101; G16H
30/40 20180101; A61B 6/482 20130101; A61B 6/486 20130101; A61B
6/503 20130101; A61B 6/5288 20130101; A61B 2576/023 20130101; A61M
5/007 20130101; A61B 34/20 20160201 |
Class at
Publication: |
382/128 ;
600/431; 378/87 |
International
Class: |
A61B 6/00 20060101
A61B006/00; G01N 23/20 20060101 G01N023/20; G06K 9/00 20060101
G06K009/00 |
Claims
1. A system to reconstruct multiple phases of a subject,
comprising: an imaging system having: an energy source operable to
emit energy in a selected direction; a detector positioned opposite
the energy source to detect the emitted energy; a gantry operable
to be positioned around the subject such that the detector and the
source are able to move around the subject in response to an
imaging system instruction; a pump operable to inject a contrast
agent into the subject in response to a pump instruction; a
controller in communication with the imaging system and the pump
operable to provide the imaging system instruction to the imaging
system and the pump instruction to the pump; wherein the controller
is operable to at least one of control or record timing of
acquisition of image data with the imaging system and timing of the
injection of the contrast agent into the subject; wherein the
controller is further operable to acquire the image data based upon
the timing of the injection of the contrast agent.
2. The system of claim 1, further comprising: a pump timer operable
to determine an amount of time that has passed since the beginning
of the injection of the contrast agent by the pump; and an imaging
system timer operable to determine an amount of time that has
passed since the beginning of the injection of the contrast agent
by the pump and generated an index time for the image data.
3. The system of claim 2, further comprising: an image data
indexer, wherein the image data includes a plurality of image data
frames collected of the subject over time and time stamped by the
imaging system timer and the image data indexer is operable to
execute instructions to determine whether a selected portion of the
image data is regarding a first anatomical phase or a second
anatomical phase based on at least one of the indexed time of the
image data and input constraints.
4. The system of claim 3, further comprising: a memory system that
stores the input constraints that are input to the image data
indexer based on prior knowledge of a physiology of the subject,
anatomy of the subject, and number of anatomical phases.
5. The system of claim 3, further comprising: a three-dimensional
model reconstruction system operable to execute instructions to
reconstruct a first model of the first anatomical phase and a
second model of the second anatomical phase.
6. The system of claim 5, further comprising: a tracking system
operable to track an instrument in a navigation space; and a
display device operable to display at least one of the first model
of the first anatomical phase or the second model of the second
anatomical phase and an instrument icon representing a location of
the instrument relative to the phase in the navigation space.
7. The system of claim 2, wherein the imaging system further
comprises: a cart having a set of wheels operable to allow the cart
to move the gantry and the attached detector and source from a
first operating room to a second operating room.
8. A method reconstructing multiple phases of a subject,
comprising: injecting a contrast agent into the subject at a
selected injection start time, wherein the contrast agent injected
into the subject has a x-ray scattering pattern different than that
of an anatomy of the subject; powering a x-ray source to emit
x-rays to be detected by a detector at a selected imaging start
time; moving the x-ray source and the detector relative to the
subject; and acquiring image data of a selected portion of the
subject over time while moving the x-ray source and the detector,
wherein the image data includes a plurality of image frames of the
subject acquired over the time and at different positions relative
to the subject based on the moving of the x-ray source and the
detector; correlating the plurality of image frames over time to a
position of the contrast agent in the subject over time; selecting
a first phase of the subject; determining a first phase
sub-plurality of the plurality of image frames that relate to the
first phase in the subject; and reconstructing a model of the first
phase of the subject based on the determined first phase
sub-plurality of the plurality of image frames.
9. The method of claim 8, further comprising: moving the single
x-ray source tube to the first selected position relative to the
subject in a selected operating theater.
10. The method of claim 9, further comprising: wherein
reconstructing a model of the first phase of the subject includes
executing instructions with a processor to determine a model of the
first phase of the subject based on the determined first phase
sub-plurality of the plurality of image frames.
11. The method of claim 10, further comprising: selecting a second
phase of the subject; determining a second phase sub-plurality of
the plurality of image frames that relate to the second phase in
the subject; and reconstructing a model of the second phase of the
subject based on the determined second phase sub-plurality of the
plurality of image frames.
12. The method of claim 11, wherein executing instructions with the
processor to reconstruct a model of the selected portion of the
subject includes reconstructing a multi-phase model of the selected
portion of the subject including both the first phase and the
second phase.
13. The method of claim 12, wherein reconstructing a multi-phase
model of the selected portion of the subject includes constructing
the multi-phase model to illustrate a first phase of physiological
action and anatomical location and a second phase of physiological
action and anatomical location.
14. A method reconstructing multiple phases of a subject,
comprising: selecting a first phase of the subject to be
reconstructed; receiving image data of a selected portion of the
subject over time while a contrast agent is moving through the
selected portion of the subject, wherein the image data includes a
plurality of image frames of the selected portion of the subject
acquired over time; correlating each of the plurality of image
frames to a position of the contrast agent in the subject;
determining a first phase sub-plurality of image frames of the
plurality of image frames that relate to the selected first phase
in the subject; and reconstructing a first phase model of the
selected first phase of the subject based on the determined first
phase sub-plurality of the plurality of image frames.
15. The method of claim 14, wherein the received image data
includes image frames at different perspectives relative to the
subject.
16. The method of claim 15, further comprising: inputting
constraints to a processor systems regarding the selected first
phase; executing instructions with the processor system to perform
the determining the first phase sub-plurality of image frames of
the plurality of image frames that relate to the selected first
phase in the subject is based on the input constraints; and
executing instructions with the processor system to reconstruct the
first phase model based on the determined first phase sub-plurality
of image frames.
17. The method of claim 16, wherein the input constraints include
at least one of a time constraint, a number of phases constraint, a
timing of an injection of the contrast constraint, and a perfusion
rate constraint.
18. The method of claim 16, further comprising: determining a time
of injection of the contrast agent into the subject relative to an
initial image frame acquisition of the plurality of image frames of
the received image data.
19. The method of claim 14, further comprising: selecting a second
phase of the subject to be reconstructed; determining a second
phase sub-plurality of image frames of the plurality of image
frames that relate to the selected second phase in the subject; and
reconstructing a second phase model of the selected second phase of
the subject based on the determined second phase sub-plurality of
the plurality of image frames.
20. The method of claim 19, further comprising: inputting
constraints to a processor systems regarding both of the selected
first phase and the selected second phase.
21. The method of claim 20, wherein the first phase is different
than the second phase.
22. The method of claim 21, wherein selecting a first phase
includes selecting an arterial phase of the subject and selecting
the second phase includes selecting a venous phase of the
subject.
23. The method of claim 22, further comprising: tracking an
instrument relative to at least one of the arterial phase of the
subject or the venous phase of the subject; and displaying a
location of the tracked instrument relative to the at least one of
the arterial phase of the subject or the venous phase of the
subject as an instrument icon on a display device superimposed on
at least one of the reconstructed first phase model or
reconstructed second phase model.
24. The method of claim 14, wherein selecting a first phase
includes selecting a portion of a vasculature of the subject less
than a complete vasculature of the subject within the selected
portion of the subject to be reconstructed as the first phase
model.
25. The method of claim 14, further comprising: injecting the
contrast agent into the subject; and moving an imaging portion of
an imaging device relative to the subject at a rate to collect less
than a complete 360 degree rotation of the subject while the
contrast agent is in the selected first phase.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of U.S. patent
application Ser. No. 12/908,189 filed on Oct. 20, 2010. The entire
disclosure of the above application is incorporated herein by
reference.
FIELD
[0002] The present disclosure relates to imaging a subject, and
particularly to determining and performing an optimal image data
acquisition of the subject to model various physiological
characteristic and anatomical features of the subject.
BACKGROUND
[0003] This section provides background information related to the
present disclosure which is not necessarily prior art.
[0004] A subject, such as a human patient, may select or be
required to undergo a surgical procedure to correct or augment an
anatomy of the patient. The augmentation of the anatomy can include
various procedures, such as movement or augmentation of bone,
insertion of implantable devices, or other appropriate procedures.
A surgeon can perform the procedure on the subject with images of
the patient that can be acquired using imaging systems such as a
magnetic resonance imaging (MRI) system, computed tomography (CT)
system, fluoroscopy (e.g. C-Arm imaging systems), or other
appropriate imaging systems.
[0005] Images of a patient can assist a surgeon in performing a
procedure including planning the procedure and performing the
procedure. A surgeon may select a two dimensional image or a three
dimensional image representation of the patient. The images can
assist the surgeon in performing a procedure with a less invasive
technique by allowing the surgeon to view the anatomy of the
patient without removing the overlying tissue (including dermal and
muscular tissue) when performing a procedure.
SUMMARY
[0006] This section provides a general summary of the disclosure,
and is not a comprehensive disclosure of its full scope or all of
its features.
[0007] According to various embodiments, a system to acquire image
data of a patient with an imaging system using enhanced contrast
imaging can include an imaging system having a first energy source
with a first energy parameters and a second energy source with a
second energy parameters. The imaging system can also include a
pump operable to inject a contrast agent into the patient with an
instruction. A controller can be in communication with both the
imaging system and the pump. The imaging system can communicate
with the pump through the controller regarding timing of the
injection of a contrast agent into the patient and is further
operable to acquire image data based upon the timing of the
injection of the contrast agent and/or the clinical procedure.
[0008] Further areas of applicability will become apparent from the
description provided herein. The description and specific examples
in this summary are intended for purposes of illustration only and
are not intended to limit the scope of the present disclosure.
DRAWINGS
[0009] The drawings described herein are for illustrative purposes
only of selected embodiments and not all possible implementations,
and are not intended to limit the scope of the present
disclosure.
[0010] FIG. 1 is an environmental view of an imaging system in an
operating theatre;
[0011] FIG. 2 is a detail view of an imaging system with a dual
energy source system;
[0012] FIG. 3A is a schematic representation of non-contrast
enhanced image data;
[0013] FIG. 3B is a schematic representation of a contrast enhanced
image data;
[0014] FIG. 4 is a flowchart of a method of reconstruction of a
volume with acquired image data;
[0015] FIG. 5A-5C illustrate images and a contrast agent flowing
through a portion of a subject;
[0016] FIGS. 6A and 6B illustrate reconstructions of two different
phases of the subject; and
[0017] FIG. 7 illustrates a view of an instrument icon superimposed
on a reconstruction of one of the phases from FIGS. 6A and 6B.
[0018] Corresponding reference numerals indicate corresponding
parts throughout the several views of the drawings.
DETAILED DESCRIPTION
[0019] Example embodiments will now be described more fully with
reference to the accompanying drawings.
[0020] With reference to FIG. 1, in an operating theatre or
operating room 10, a user, such as a surgeon 12, can perform a
procedure on a patient 14. In performing the procedure, the user 12
can use an imaging system 16 to acquire image data of the patient
14 for performing a procedure. A model can be generated using the
image data and displayed as image data 18 on a display device 20.
The display device 20 can be part of a processor system 22 that
includes an input device 24, such as a keyboard, and a processor 26
which can include one or more processors or microprocessors
incorporated with the processing system 22. A connection 28 can be
provided between the processor 26 and the display device 20 for
data communication to allow driving the display device 20 to
illustrate the image data 18.
[0021] The imaging system 16 can include an O-Arm.RTM. imaging
system sold by Medtronic Navigation, Inc. having a place of
business in Louisville, Colo., USA. The imaging system 16,
including the O-Arm.RTM. imaging system, or other appropriate
imaging systems in use during a selected procedure are also
described in U.S. patent application Ser. No. 12/465,206 filed on
May 13, 2009, incorporated herein by reference.
[0022] The O-Arm.RTM. imaging system 16 includes a mobile cart 30
that includes a control panel or system 32 and an imaging gantry 34
in which is positioned a source unit 36 and a detector 38. The
mobile cart 30 can be moved from one operating theater to another
and the gantry 34 can move relative to the cart 30, as discussed
further herein. This allows the imaging system 16 to be mobile thus
allowing it to be used in multiple locations and with multiple
procedures without requiring a capital expenditure or space
dedicated to a fixed imaging system.
[0023] The source unit 36 can emit x-rays through the patient 14 to
be detected by the detector 38. As is understood by one skilled in
the art, the x-rays emitted by the source 36 can be emitted in a
cone and detected by the detector 38. The source/detector unit
36/38 is generally diametrically opposed within the gantry 34. The
detector 38 can move in a 360.degree. motion around the patient 14
within the gantry 34 with the source 36 remaining generally
180.degree. opposed to the detector 38. Also, the gantry 34 can
move isometrically relative to the subject 14, which can be placed
on a patient support or table 15, generally in the direction of
arrow 40 as illustrated herein. The gantry 34 can also tilt
relative to the patient 14 illustrated by arrows 42, move
longitudinally along the line 44 relative to a longitudinal axis
14L of the patient 14 and the cart 30, can move up and down
generally along the line 46 relative to the cart 30 and
transversely to the patient 14, to allow for positioning of the
source/detector 36/38 relative to the patient 14. The O-Arm.RTM.
imaging device 16 can be precisely controlled to move the
source/detector 36/38 relative to the patient 14 to generate
precise image data of the patient 14. The imaging device 16 can be
connected with the processor 26 via connection 50 which can include
a wired or wireless connection or physical media transfer from the
imaging system 16 to the processor 26. Thus, image data collected
with the imaging system 16 can be transferred to the processing
system 22 for navigation, display, reconstruction, etc.
[0024] Briefly, according to various embodiments, the imaging
system 16 can be used with an unnavigated or navigated procedure.
In a navigated procedure, a localizer, including either or both of
an optical localizer 60 and an electromagnetic localizer 62 can be
used to generate a field or receive or send a signal within a
navigation domain relative to the patient 14. The navigated space
or navigational domain relative to the patient 14 can be registered
to the image data 18 to allow registration of a navigation space
defined within the navigational domain and an image space defined
by the image data 18. A patient tracker or dynamic reference frame
64 can be connected to the patient 14 to allow for a dynamic
registration and maintenance of registration of the patient 14 to
the image data 18.
[0025] A patient tracking device or dynamic registration device 64
and an instrument 66 can then be tracked relative to the patient 14
to allow for a navigated procedure. The instrument 66 can include
an optical tracking device 68 and/or an electromagnetic tracking
device 70 to allow for tracking of the instrument 66 with either or
both of the optical localizer 60 or the electromagnetic localizer
62. The instrument 66 can include a communication line 72 with a
navigation interface device 74 as can the electromagnetic localizer
62 with communication line 76 and/or the optical localizer 60 with
communication line 78. Using the communication lines 74, 78
respectively, the probe interface 74 can then communicate with the
processor 26 with a communication line 80. It will be understood
that any of the communication lines 28, 50, 76, 78, or 80 can be
wired, wireless, physical media transmission or movement, or any
other appropriate communication. Nevertheless, the appropriate
communication systems can be provided with the respective
localizers to allow for tracking of the instrument 66 relative to
the patient 14 to allow for illustration of the tracked location of
the instrument 66 relative to the image data 18 for performing a
procedure.
[0026] It will be understood that the instrument 66 being any
appropriate instrument, such as a ventricular or vascular stent,
spinal implant, neurological stent or stimulator, ablation device,
or the like. The instrument 66 can be an interventional instrument
or can include or be an implantable device. Tracking the instrument
66 allows for viewing the instrument's 66 location relative to the
patient 14 with use of the registered image data 18 without direct
viewing of the instrument 66 within the patient 14.
[0027] Further, the gantry 34 can include an optical tracking
device 82 or an electromagnetic tracking device 84 to be tracked
with a respective optical localizer 60 or electromagnetic localizer
62. Accordingly, the imaging device 16 can be tracked relative to
the patient 14 as can the instrument 66 to allow for initial
registration, automatic registration or continued registration of
the patient 14 relative to the image data 18. Registration and
navigated procedures are discussed in the above incorporated U.S.
patent application Ser. No. 12/465,206.
[0028] With reference to FIG. 2, according to various embodiments,
the source 36 can include a single x-ray tube 100 that can be
connected to a switch 102 that can interconnect a power source A
104 and a power source B 106 with the x-ray tube 100. X-rays can be
emitted generally in a cone shape 108 towards the detector 38 and
generally in the direction of the vector 110. The switch 102 can
switch between the power source A 104 and the power source B 106 to
power the x-ray tube 100 at different voltages and amperages to
emit x-rays at different energies generally in the direction of the
vector 110 towards the detector 38. It will be understood, however,
that the switch 102 can also be connected to a single power source
that is able to provide power at different voltages and amperages
rather than the 102 switch that connects to two different power
sources A 104, and B 106. Also, the switch 102 can be a switch that
operates to switch a single power source between different voltages
and amperages. The patient 14 can be positioned within the x-ray
cone 108 to allow for acquiring image data of the patient 14 based
upon the emission of x-rays in the direction of vector 110 towards
the detector 38.
[0029] The two power sources A and B 104, 106 can be provided
within the source housing 36 or can be separate from the source 36
and simply be connected with the switch 102 via appropriate
electric connections such as a first cable or wire 112 and a second
cable or wire 114. The switch 102 can switch between the power
source A 104 and the power source B 106 at an appropriate rate to
allow for emission of x-rays at two different energies through the
patient 14 for various imaging procedures, as discussed further
herein. The differing energies can be used for material separation
and/or material enhanced reconstruction or imaging of the patient
14.
[0030] The switching rate of the switch 102 can include about 1
millisecond to about 1 second, further including about 10 ms to 500
ms, and further including about 50 ms. Further, the power source A
104 and the power source B 106 can include different power
characteristics, including different voltages and different
amperages, based upon selected contrast enhancement requirements.
For example, as discussed further herein, it can be selected to
allow for contrast enhancement between soft tissue (e.g. muscle or
vasculature) and hard tissue (e.g. bone) in the patient 14 or
between a contrast agent injected in the patient 14 and an area
without a contrast agent injected in the patient 14.
[0031] As an example, the power source A 104 can have a voltage of
about 75 kV and can have an amperage of about 50 mA, which can
differ from the power source B which can have a voltage of 125 kV
and 20 mA. The selected voltages and amperages can then be switched
with the switch 102 to power the x-ray tube 100 to emit the
appropriate x-rays generally in the direction of the vector 110
through the patient 14 to the detector 38. It will be understood
that the range of voltages can be about 40 kV to about 140 kV
(including about 40 kV to about 120 kV, and including about 50 kV
to about 80 kV) and the amperages can be about 10 mA to about 500
mA. Generally, the power characteristics differences between the
first power source A 104 and the second power source B 106 can be
about 40 kV to about 60 k V and about 20 mA to about 150 mA.
[0032] The dual power sources allow for dual energy x-rays to be
emitted by the x-ray tube 100. As discussed above, the two or dual
energy x-rays can allow for enhanced and/or dynamic contrast
reconstruction of models of the subject 14 based upon the image
data acquired of the patient 14. Generally an iterative or
algebraic process can be used to reconstruct the model of at least
a portion of the patient 14 based upon the acquired image data. It
will be understood, however, that any appropriate number of power
sources or switching possibilities can be provided. Two is included
in the subject disclosure merely for clarity of the current
discussion.
[0033] The power sources can power the x-ray tube 100 to generate
two dimension (2D) x-ray projections of the patient 14, selected
portion of the patient 14, or any area, region or volume of
interest. The 2D x-ray projections can be reconstructed, as
discussed herein, to generate and/or display three-dimensional (3D)
volumetric models of the patient 14, selected portion of the
patient 14, or any area, region or volume of interest. As discussed
herein, the 2D x-ray projections can be image data acquired with
the imaging system 16, while the 3D volumetric models can be
generated or model image data.
[0034] Appropriate algebraic techniques include Expectation
maximization (EM), Ordered Subsets EM (OS-EM), Simultaneous
Algebraic Reconstruction Technique (SART) and Total Variation
Minimization (TVM), as generally understood by those skilled in the
art. The application to performing a 3D volumetric reconstruction
based on the 2D projections allows for efficient and complete
volumetric reconstruction. Generally, an algebraic technique can
include an iterative process to perform a reconstruction of the
patient 14 for display as the image data 18. For example, a pure or
theoretical image data projection, such as those based on or
generated from an atlas or stylized model of a "theoretical"
patient, can be iteratively changed until the theoretical
projection images match the acquired 2D projection image data of
the patient 14. Then, the stylized model can be appropriately
altered as the 3D volumetric reconstruction model of the acquired
2D projection image data of the selected patient 14 and can be used
in a surgical intervention, such as navigation, diagnosis, or
planning. The theoretical model can be associated with theoretical
image data to construct the theoretical model. In this way, the
model or the image data 18 can be built based upon image data
acquired of the patient 14 with the imaging device 16.
[0035] The 2D projection image data can be acquired by
substantially annular or 360.degree. orientation movement of the
source/detector 36/38 around the patient 14 due to positioning of
the source/detector 36/38 moving around the patient 14 in the
optimal movement. Also, due to movements of the gantry 34, the
detector need never move in a pure circle, but rather can move in a
spiral helix, or other rotary movement about or relative to the
patient 14. Also, the path can be substantially non-symmetrical
and/or non-linear based on movements of the imaging system 16,
including the gantry 34 and the detector 38 together. In other
words, the path need not be continuous in that the detector 38 and
the gantry 34 can stop, move back the direction from which it just
came (e.g. oscillate), etc. in following the optimal path. Thus,
the detector 38 need never travel a full 360.degree. around the
patient 14 as the gantry 34 may tilt or otherwise move and the
detector 38 may stop and move back in the direction it has already
passed.
[0036] In acquiring image data at the detector 38, the dual energy
x-rays generally interact with a tissue and/or a contrast agent in
the patient 14 differently based upon the characteristics of the
tissue or the contrast agent in the patient 14 and the energies of
the two x-rays emitted by the x-ray tube 100. For example, the soft
tissue of the patient 14 can absorb or scatter x-rays having an
energy produced by the power source A 104 differently than the
x-rays having energy produced by the power source B 106. Similarly,
a contrast agent, such as iodine, can absorb or scatter the x-rays
generated by the power source A 104 differently from those
generated by the power source B 106. Switching between the power
source A 104 and the power source B 106 can allow for determination
of different types of material properties (e.g. hard or soft
anatomy), or contrast agent, implants, etc. within the patient 14.
By switching between the two power sources 104, 106 and knowing the
time when the power source A 104 is used to generate the x-rays as
opposed to the power source B 106 to generate the x-rays the
information detected at the detector 38 can be used to identify or
segregate the different types of anatomy or contrast agent being
imaged.
[0037] A timer can be used to determine the time when the first
power source A 104 is being used and when the second power source B
106 is being used. This can allow the images to be indexed and
separated for generating different models of the patient 14. Also,
as discussed herein, the timer, which can be a separate system or
included with the imaging system 16 or the processor system 26, can
be used to index image data generated with the contrast agent
injected into the patient 14.
[0038] With reference to FIG. 3A, image data acquired when powering
the x-ray tube 100 with the power source 104 is schematically
illustrated. As illustrated in FIG. 3A, the image data can include
image data of soft tissue, such as surrounding tissues 150 that
surround a vasculature 152. As illustrated in FIG. 3A, the power
source A 104 can generate x-rays of the x-ray tube 100 that provide
substantially little contrast between the vasculature 152 and the
surrounding tissue 150, even if a contrast agent is present in the
vasculature agent 152, such as iodine. With reference to FIG. 3B,
however, the second power source B 106 can be used to generated
second energy x-rays to acquire image data that illustrates the
surrounding tissue 150' relative to the vasculature 152'. This can
be further enhanced with a contrast agent that can be injected into
the patient 14. As is understood in the art, the two power levels
have different attenuations based on the materials in the patient
14. This differing attenuation can be used to differentiate
materials, e.g. vasculature 152 and the surrounding tissue 150, in
the patient 14.
[0039] With the acquisition of the image data illustrated in FIG.
3A and FIG. 3B, a reconstruction can be made to clearly identify
the vasculature 152 of the patient 14 separate from the surrounding
tissue 150 of the patient 14. The dual energy system can be used to
reconstruct a model of the vasculature 152 of the patient 14 to
discriminate the vasculature 152 from the surrounding tissue 150 of
the patient 14. In identifying the vasculature 152, the imaging
system 16, including the O-Arm.RTM. imaging system, can be used to
efficiently image the vasculature 152 of the patient 14 in the
operating theatre 10 during a procedure, such as a valve
replacement procedure, a stent procedure, an inclusion ablation
procedure, or an angioplasty procedure.
[0040] At least because the x-ray tube 100 is in a moveable imaging
system, such as the imaging system 16, it can be moved relative to
the patient 14. Thus, the x-ray tube 100 may move relative to the
patient 14 while the energy for the x-ray tube 100 is being
switched between the first power source 104 and the second power
source 106. Accordingly, an image acquired with the first power
source 104 may not be at the same pose or position relative to the
patient 14 as the second power source 106. If a model is desired or
selected to be formed of a single location in the patient 14,
however, various interpolation techniques can be used to generate
the model based on the amount of movement of the x-ray tube 100
between when the projection with the first power source 104 and the
projection with the second power source 106 was acquired.
[0041] The dual energy of the x-rays emitted by the x-ray tube 100
due to the two power sources 104, 106 can allow for substantially
efficient and enhanced contrast discrimination determination
between the vasculature 152 and the musculature 150 of the patient
14. Moreover, the switching by a switch 102 between the power
source A 104 and the power source B 106 allows for an efficient
construction of the source 36 where the single x-ray tube 100 can
allow for the generation of x-rays at two different energies to
allow for enhanced or dynamic contrast modeling of the patient 14,
such as modeling the vasculature of the patient 14 including a
contrast agent therein.
[0042] The patient 14 can also be imaged with the injected contrast
agent by gating the acquisition of the image data of the patient 14
based upon the injection of the contrast agent. According to
various embodiments, a contrast agent, such as iodine, can be
injected into the patient 14 to provide additional contrast in the
image data acquired of the patient 14 with the imaging system 16.
During the image acquisition, however, the contrast agent flows
through the vasculature of the patient 14 from an artery phase to a
venous phase. For example, the contrast agent can be injected into
the patient 14 into an artery where the contrast agent can flow
through the vasculature of the patient 14 to the heart, through the
heart, to the lungs through the venous system, back through the
heart, and out into the arterial portion of the vasculature of the
patient 14.
[0043] When acquiring image data of the patient 14 to identify or
reconstruct the vasculature of the patient 14, knowing the timing
of when image data is acquired relative to the timing of the
injection of the contrast agent can allow for a reconstruction of
the various phases based on the known movement of the contrast
agent through structures of the patient 14. In other words, it is
generally understood that the contrast agent will flow through the
patient 14 as described above at a known or generally known rate.
As illustrated in FIG. 3B, the dual energy x-rays, generated with
the x-ray tube 100 based upon the power source A 104 and the power
source B 106, can be used to generate image data of any portion of
the vasculature of the patient 14.
[0044] The acquisition of the image data, therefore, can be gated
relative to the injection of the contrast agent into the patient
14. For example, the controls 32 of the imaging system 16 can be
associated or communicate with a control of a pump 170 (illustrated
in FIG. 1) through a communication line 172 (illustrated in FIG. 1)
that pumps or injects the contrast agent into the patient 14. The
communication 172 between the pump 170 and the imaging device
control 32 can be any appropriate communication such as a wired,
wireless, or other data communication system. Also, the control 170
for the pump can be incorporated into the controls 32 of the
imaging system 16 or the processor system 26.
[0045] According to various embodiments, the control system 32 for
the imaging system 16 can control the pump 170 to initiate
injection of the contrast agent into the patient 14. The imaging
system 16 can then acquire image data of the patient 14 over a set
period of time to identify the difference between an arterial phase
and a venous phase in the patient 14. For example, the imaging
system can control the pump 170 to inject the contrast agent and
then acquire image data for approximately 10 seconds to
approximately 20 second including approximately 13 seconds. The
imaging system 16 can identify or separate a first portion of the
image data, such as about 5 second to about 7 seconds, including
about 6 seconds as an arterial phase and a second phase of the
image data, such as image data acquired after about 6 second to
about 8 seconds, including about 7 seconds as a venous phase. In
other words, the control system 32, or other appropriate processor
system, can index the image data to determine when the image data
was acquired. Also, it will be understood that the image data can
be acquired at the two energies. Thus, the controls 32 or other
appropriate processing system (e.g. a timer) can index the image
data based on which of the two power sources 104, 106 were used to
power the x-ray tube 100.
[0046] After the acquisition of the image data and determining a
segregation of time of image data acquisition, a reconstruction of
the vasculature of the patient 14 can then be made to illustrate or
identify or reconstruct an arterial phase of the patient 14 and
separately a venous phase of the patient 14. Accordingly, the
imaging system 16 controlled with the controller 32 can be used to
acquire image data of both a venous phase and an arterial phase of
the patient 14 in a single image data acquisition sweep or period.
In other words, the phase determination and reconstruction of an
arterial phase and a venous phase of the vasculature of the patient
14 can be based on a single image data acquisition phase of the
patient 14. Again, this can minimize or limit the exposure of the
patient 14 and operating room staff to x-rays emitted from the
x-ray tube 100 by requiring only a single image data acquisition
phase. It will be understood, however, that a plurality of image
data acquisition phases can be acquired of the patient 14.
[0047] The control system 32 of the imaging system 16 can be used
to gate acquisition of the image data in addition to or with timing
of the pump 170. For example, it can be selected to acquire image
data of the vasculature of the patient 14 during diastole of the
heart. During diastole of the heart of the patient 14, the heart
generally does not move and blood in the vasculature is also
relatively still. Accordingly, the image data can be acquired of
the patient 14 by gating the acquisition of the image data relative
to the heart movement of the patient 14. The generation of the
x-rays with the x-ray tube 100 can be switched with the switch 102
to allow for time emission of x-rays from the x-ray tube 100.
[0048] The image data can be acquired by emitting x-rays from the
x-ray tube 100 substantially sequentially such that at a selected
period of time no x-rays are emitted by the x-ray tube 100 and at a
different or second selected time x-rays are emitted from the x-ray
tube 100. The x-rays emitted from one period to another can be at
either of the two energies allowed by the power source A 104 or the
power source B 106. Accordingly, at various times no x-rays can be
emitted from the x-ray tube 100, but at other times x-rays can be
emitted from the x-ray tube at a selected energy.
[0049] In being able to control the image system to emit or not
emit x-rays image data acquisition can be gated relative to a
physiological event of the patient 14. It will be further
understood that gating of the image acquisition can be based upon
respiration of the patient 14, physical movement of the patient 14,
and other physiological events. The control system 32 can also be
used to index the image data regarding whether acquired during a
physiological event or not. The physiological event can be
determined with an appropriate system, such as an
electrocardiogram, or based on a regular rate of image acquisition
(e.g. diastole occurs about 2 seconds in the patient 14).
[0050] Also, due to gating of the imaging system 16 relative to the
patient 14, the control system 32 can also be used to control the
imaging system 16 to control the speed of the detector 38 relative
to the patient 14. As discussed above, the detector 38 of the
imaging system can translate within the gantry 34 of the imaging
system 16 to acquire image data of the patient 14. Further as
discussed above, image data can be selected to be acquired of the
patient 14 during only selected physiological events, such as
diastole of the heart. To generate or form a three-dimensional
model of at least a portion of the patient 14, it can be selected
to have separation of a selected amount between acquisitions of
images of the patient 14.
[0051] The detector 38 can be moved at a selected speed and change
speeds to ensure appropriate separation of the images during the
selected physiological events. The detector 38 can move at a first
speed during a first physiological event such as systole of the
heart, and at a second speed, such as a greater speed, during
diastole of the heart to ensure appropriate separation of
acquisition of images of the patient 14 during the selected
physiological event.
[0052] In generating the 3D volumetric reconstruction to form the
model, as discussed above, the model may be multi-phase to
illustrate a selected portion of the patient to illustrate a first
phase of physiological action and anatomical location and a second
phase of physiological action and anatomical location. Thus, the
model, or more than one model, can be used to illustrate a first
phase (e.g. an arterial phase) and a second phase (e.g. venous
phase) of the patient 14. Also, due to gating and movement of the
detector 38 a first position of the detector 38 during image data
acquisition and a second position of the detector 38 during image
data acquisition can be used in the generating the first model and
generating the second model to illustrate more than one phase of a
physiological action of the patient 14. Additionally, the anatomy
of the patient 14 and the physiology of the patient 14 can be used
to form the 3D reconstruction. For example, the configuration of a
bone of the patient 14 or a phase of a heart beat of the patient 14
can be used as a priori knowledge to assist in model
reconstruction.
[0053] Also, the controller 32 of the imaging system 16 can be used
to "rewind" or move the detector 38 back over the same path just
traversed by the detector 38. Even while moving in a selected
single path or direction, the detector 38 can be stopped and
started, for example for gating or acquiring additional image data
(e.g. x-ray projections) at a selected location. Accordingly, the
controller 32 can control the imaging system 16 to achieve a
selected separation of images relative to the patient 14 for
reconstruction of an appropriate or selected model of the patient
14 based upon the required image data.
[0054] The reconstruction based on the image data or the raw image
data can be used to perform a procedure on the patient 14. As
discussed above selected navigation or tracking systems can be
associated with the imaging system 16. Accordingly, the patient 14
can be registered to the image data and a navigation procedure can
be performed. The navigated procedure can include placement of a
stent in the patient's 14 heart, brain, or other vasculature,
ablation procedures, angioplasty, implant placement or bone
resection. Navigation can include tracking or determining
automatically a location of an instrument positioned in a
navigation field relative to a selected reference frame, such as in
patient space, during a surgical procedure. The location of the
instrument 66 can be illustrated on the display device 20 with an
icon 174 that can be superimposed on the image data or the
reconstructed model or image data 18.
[0055] In a subject, such as in the anatomy of the patient 14,
various structures exist. Some structures can be imaged with
various imaging modalities, for example x-ray imaging modalities,
such as the O-Arm.RTM. imaging device 16. Some structures include
the vasculature 152 of the patient 14. The vasculature 152 is
generally not be imageable without the use of a contrast agent that
is injected into the patient 14. The vasculature 152 also includes
several phases or portions. As discussed in greater detail herein,
the vasculature can include an arterial phase including arteries
and a venous phase including veins. The two phases are
distinguished by the purpose of the particular portion of the
vasculature 152. In brief, the two phases can relate to one another
regarding blood that has been oxygenated by traversing relative to
the lungs in the arterial phase and the blood that is returning to
the heart to be transferred to the lungs in the venous phase.
[0056] The contrast agent moves through the vasculature 152, due to
flow of blood, and the imaging device 14 captures images over time
as image frames as the contrast agent is moving. The contrast agent
moves from one phase to another in sequence, as defined by the
anatomy and physiology of the patient 14. Thus, the sequence of
images includes images that relate only or substantially only to
one phase in each image frame. In other words, if an image is taken
when the contrast agent is in an artery then the image is from the
arterial phase. Similarly, if an image is taken when the contrast
agent is in a vein then the image is from the venous phase.
[0057] The acquired image data can be used to reconstruct a model,
including a three-dimensional (3D) volumetric model of the various
phases. The image data and/or reconstructed model can be used to
plan or confirm a result of a procedure without requiring or using
navigation and tracking. The image data can be acquired to assist
in a procedure, such as an implant placement. Also, the image data
can be used to identify blockages in the vasculature of the patient
14, such as with the contrast agent. Thus, navigation and tracking
are not required to use the image data in a procedure. Also, the
image data can relate to multiple different phases of the subject.
The different phases can include an artificial phase (i.e. an
arterial portion at the vasculature 152) or a venous phase (i.e. a
venous portion at the vasculature 152).
[0058] With reference to FIG. 4 a flowchart 200 illustrates a
method of acquiring image data of a subject, such as the patient
14, to allow for reconstruction of multiple phases of various
portions of the patient 14. As discussed herein, the vasculature
152 can include various phases and can be imaged particularly with
a contrast agent. It will be understood, however, that other phases
can also be determined based upon the region of the anatomy and the
desire of viewing different portions or phases of the anatomy.
[0059] According to various embodiments, the imaging device 16 is
operable to acquire image data of the patient 14 in a selected
manner. For example, the image acquisition portion can move around
the patient 14 generally in a circle or in various configurations
of a helix, spiral, and other configurations relative to the
patient 14. Due to the speed of material flowing through the
vasculature 152 of the patient 14, however, the imaging system 16
may not be able to make an entire circle of the patient 14 while
the contrast agent is in a single selected phase in the patient 14
(e.g. in an arterial phase, as discussed herein). Accordingly, it
can be selected to determine in which phase a selected portion of
the image data, such as a frame of image, is acquired of the
patient 14.
[0060] According to the flowchart 200, particular phases of the
patient 14 can be determined or reconstructed based upon acquired
image data. Generally, the number of phases can be determined by a
user, such as the user 12, and by the position of the contrast
agent within the patient 14 over time. Image data acquired with the
contrast agent allows for the acquisition of distinguishable or
usable image data for forming a reconstruction of the patient 14,
or a portion of the patient 14. For example, various soft tissue
portions and vasculature may not generally be distinguishable using
certain imaging modalities without a contrast agent. The
reconstruction can be a volumetric or three-dimensional (3D)
reconstruction or model of the patient 14. The 3D model can be used
for various purposes, as discussed herein, such as to illustrate
the position of the instruments (e.g. an ablation catheter)
relative to the patient 14.
[0061] With continuing reference to FIG. 4 the flowchart 200 can
begin at start block 202. A subject can be positioned for imaging
in block 204. It is understood, that the subject 14 can be
maintained in the same or generally same position for a navigated
procedure as well. As illustrated in FIG. 1, the subject, which can
include the patient 14, can be positioned relative to the imaging
system 16. The patient 14 can be positioned on the table 15 and
held in place with straps, or other holding systems. It is not
required to fix the patient to the table 15 or provide any specific
support of the patient 14. As discussed herein, the imaging system
16 can acquire image data of the patient 14. A selected image
acquisition method can include acquiring a frame of image data at a
selected point in space and at a selected point in time relative to
the patient 14. The image frame can generally relate to a single
instance of image acquisition and can form a portion of a
collection of image data of the patient 14 where multiple image
frames can be collected over time. In other words, the image frame
can include a complete view by the image system 16 at one selected
time and location.
[0062] Once the patient 14 has been positioned relative to the
imaging system 16, in block 204, a contrast agent can be injected
with the pump 170 in block 206. The contrast agent can be any
appropriate contrast agent, including iodine or other contrast
agents, which is operable to allow for a contrast between the
vasculature 152 of the patient 14 and surrounding tissue 150 in the
patient 14. Generally, soft tissue may not be substantially or
adequately opaque when acquiring image data with x-rays. Thus, to
acquire appropriate image data of the soft tissue or the
vasculature 152 a contrast agent can allow for an appropriate
opacity of the vasculature 152. The contrast agent can flow through
the vasculature 152 being carried via the bloodstream. The opacity
in the vasculature generates the appropriate contrast relative to
the surrounding soft tissue for x-ray image acquisition. The pump
170 can be used to inject the contrast agent into the patient 14.
The contrast agent then traverses the patient's vasculature 152
over time and, as such, moves through the various phases of the
vasculature over time.
[0063] As discussed above, the pump 170 can be controlled relative
to the imaging system 16, either directly with imaging system 16 or
with the processor 28 to inject the contrast agent into the patient
14. The communication line 172 can be used to control the pump 170
for the injection of contrast agent. The time of the injection of
the contrast agent can therefore be determined in block 208. The
time of the injection of the contrast agent can be a selected
absolute time (e.g. a particular hour, minute, and second) or can
be a time relative to the acquisition of image data. For example,
image data can be collected of the subject with a contrast agent
injected in block 210. Accordingly the determination of time of
injection in block 208 can correspond to the initiation of the
image acquisition of the patient in block 210. In other words, the
start of the injection of the contrast agent could be at time
T.sub.0 which could relate to a first image frame acquired with the
imaging system 16. The initiation of the injection of the contrast
agent could also be at time T.sub.0. Time could then progress
forward in selected steps (such as one second, two seconds, etc.)
for image data acquisition and time from the initiation of the
contrast agent injection. Therefore, the determination of time of
injection of the contrast agent in block 208 can be either a
relative time (e.g. relative to the acquisition of image data) or
absolute time. Additionally, the time of acquisition of image data
can also be determined.
[0064] As will be discussed in detail below, the contrast agent is
injected into the patient 14 to allow for appropriate contrast that
allows imaging of the vasculature of the patient 14. As discussed
above, and illustrated in FIG. 3A, the vasculature 152 may
generally be relatively indistinguishable relative to the soft
tissue 150 surrounding the vasculature 152 using various imaging
modalities, such as x-ray imaging. However, acquiring x-ray images
in the operating theater 10 can be selected based upon costs,
efficiency of image data acquisition, user selection, or the like.
It can be selected, however, to attempt to minimize contrast agent
injection into the patient 14 by acquiring substantially all
necessary image data during one injection and image data
acquisition cycle.
[0065] As illustrated in FIGS. 5A-5C, however, the contrast agent
generally washes or passes through different phases of the
vasculature, such as an arterial phase and a venous phase, and
collecting an appropriate amount of image data of the selected
phases may be difficult. For example, a 360.degree. collection of
image data of a particular phase can be used to generate a
three-dimensional reconstruction of the selected phase. If the
imaging device 16 is unable to rotate fast enough relative to the
patient 14, then a full 360.degree. rotation of the patient 14
while the contrast agent is in a single phase, then one set of
image data from a complete 360.degree. rotation relative to the
patient 14 will include multiple phases, as illustrated in FIGS.
5A-5C. Accordingly, the determination of input parameters including
which frames belong to which phases, parameters regarding a peak
and decrease of pixel intensity within the selected phases, and
other parameters, including position of the imaging device 16
relative to the patient 14, can be used for an appropriate
three-dimensional reconstruction.
[0066] As discussed above, the three-dimensional reconstruction can
be based upon selected reconstruction algorithms. The
reconstruction algorithms can include generating a model and
reducing error between projections based on the acquired image data
and an ideal model projection, as discussed above. Generally, the
reconstruction uses the acquired two-dimensional image data to
determine a theoretical projection based on the acquired images.
Error is reduced between the theoretical projection and the model
projection being made to reconstruct the reconstruction to a
selected accuracy based on the acquired image data.
[0067] The image data, once collected or during collection, after
injecting the contrast agent can be correlated in time to the
injection or perfusion time of the contrast agent in the patient
14. A correlation can be made between the image frames and the time
since injection as indicated in block 212. The correlation between
the time since injection and the image frame can be based upon the
determination of the time of injection in block 208 and the
determination of the beginning of the image acquisition in block
214. For example, images can be collected at various time
intervals, such as about one second apart. The timeline of the
image frames collected with the imaging of system 16, therefore,
can be correlated with perfusion (e.g. the time since contrast
agent injection) time as determined in the series of images. The
correlation of each image frame to a time of perfusion can be used
to determine the phase for which the image was collected, including
image data with the contrast agent injected into the patient 14 in
that phase. Accordingly, an image frame that is taken after 30
seconds or after about 30 frames can be determined along with each
of the other frames in the series of collected image data. In other
words, each frame can be correlated to a specific time or to a
relative time regarding the injection of the contrast agent. A
timer can be provided with the pump and the imaging device 16 to
record times relating to imaging time and perfusion time.
[0068] A determination of a region of interest can be made in block
214. The determination of the region of interest can be made prior
to acquisition of the image data or at any selected time. Regions
of interest can include cranial regions, abdominal regions, cardiac
regions, peripheral regions, or any other appropriate region of the
patient 14. The region can generally relate to a portion of the
subject, such as a portion of the patient 14, that can be imaged in
order to acquire image data of a vasculature within the region of
interest.
[0069] After the determination of the region of interest is made in
block 214, a determination of phases in the region of interest can
be made in block 216. Again, the determination of the phases of
interest can be made either prior to, during, or after the
acquisition of the image data. The phases can include determining a
number and/or determining or identifying the position of the
contrast agent within the vasculature 152 of the patient 14. For
example, as discussed above, an arterial phase and a venous phase
can be two phases of the vasculature. It will be understood,
however, that other phases can also be determined such as both
early and late arterial phases and both early and late venous
phases. Accordingly, the determination of phases can be made to
allow for reconstruction of selected phases, such as reconstruction
of only an arterial and only a venous phase or the reconstruction
of an early arterial and a late arterial phases. The selection of
phases is also used to determine which phases to reconstruct and
assists in later correlation of image frames for
reconstruction.
[0070] The determination of the number of phases in the region of
interest can be based upon the parameters of the imaging system 16,
such as the speed of acquisition of image data and the positions of
the imaging device 16 relative to the patient 14. Regarding the
speed of the imaging device 16, if the injection of the contrast
agent into the patient 14 is made and the imaging system 16 is only
able to collect 10 frames per second then collecting enough image
data to reconstruct a large number of phases may not be possible.
If the imaging device 16, however, is operable to collect 30 or 40
frames per second, then it may be possible to reconstruct a greater
number of phases.
[0071] Generally, to reconstruct a three-dimensional model with a
selected degree of accuracy it can be selected to acquire image
data including at least an arc of at least about 150 degrees
(.degree.) to about 230.degree., including about 180.degree. to
about 210.degree., and further including about 200.degree. of a
single phase. Accordingly, the speed of movement of the imaging
device 16 relative to the patient 14 can also limit or be used to
determine the number of phases to be imaged. For example, if the
imaging device 16 is able to move to acquire image data in at least
a 200.degree. arc relative to the patient 14 while the contrast
agent is within the arterial phase then an arterial phase can be
reconstructed. However, if the imaging device 16 is able to move in
a 360.degree. arc during the arterial phase then at least two
phases of the arterial phase can be made, such as an early and the
late arterial phase.
[0072] The imaging system 16 or other processing systems such as
the processor system 26 of the modeling system, can be used to
generate the reconstruction, as discussed above. In block 218 the
image frames, the correlated time of contrast injection of agent in
the frames, the region of interest and the number of phases of
reconstruction can be input into the selected processor.
Essentially, the frames of image data can be provided to the
appropriate processor system along with a related time relative to
the injection of the contrast agent and other parameters or
constraints (including the region to be reconstructed and the
phases in the region to be reconstructed). The parameters or
constraints of the determined phases may also be recalled from a
memory system and can be input in block 220.
[0073] Parameters or constraints can include time constraints
regarding when a particular phase will have the contrast agent
present for imaging. For example, the arterial phase can be
constrained to the image frames between a first time point and a
second time point. Accordingly, the correlated image frames can be
broken into the particular time frames that would relate to be
selected phases. Additionally timing of the contrast can be used to
determine when the contrast may have moved from one phase to
another phase in the image data. The number of phases can also be a
constraint and used to determine which frames belong to which
phase. Additionally, the perfusion or wash of the contrast agent
through the selected regions, as illustrated by the selected phase
pixels 240, 242 can be used to determine which pixels have an
intensity relating to a presence of the contrast agent. The
perfusion is based on the flow of material (e.g. blood) through the
vasculature that is carrying the contrast agent.
[0074] The input of the determined parameters can be input by the
user 12 during the procedure, such as with the input device 24, or
can be recalled from a selected memory system based upon the
determined region of interest and phases of interest. The
parameters, as discussed herein, can be used to allow for the
reconstruction of a three-dimensional volume based upon the
plurality of image frames collected of the patient 14 during the
image acquisition phase.
[0075] The model can be reconstructed in block 222 based upon the
image data acquired at the patient 14 and the input parameters from
block 220. As exemplary illustrated in FIGS. 5A-5C, frames of image
data can be collected of the patient 14. As discussed above, the
vasculature 152 of the patient 14 can include various phases which
denote different physical anatomical locations within the patient
14. Exemplary phases can include an early arterial phase 230 and a
late arterial phase 232, early venous phase 234 and the late venous
phase 236. As discussed above, the early and late portions of the
different phases may not be distinguishable with the image data,
but are illustrated here for the following discussion as an example
of various parameters that can be input into the system. The
imaging device 16 would need to acquire the image data at an
appropriate rate to be able to determine or reconstruct both an
early and late phase of a particular phase, such as an arterial and
venous phase.
[0076] As illustrated in FIG. 5A, an arterial pixel or region 240
can be selected or determined that is within the arterial phase and
a venous pixel or region 242 can be chosen that is within the
venous phase. As illustrated by the cross-hatching in FIG. 5A, the
contrast agent is within the early arterial phase 230 and FIG. 5A
illustrates image data able to be captured due to the presence of
the contrast agent in the vasculature 152. In FIG. 5B the contrast
agent has passed into the late arterial phase 232, as shown by the
cross-hatching in the late arterial phase region 232. Also, as
illustrated in FIG. 5B, the contrast agent is illustrated as it
begins to move into the early arterial phase 234, illustrated by
the dotted region in the early venous phase 234.
[0077] The arterial pixel 240 in the arterial phase can be input as
a parameter that is expected to have a peak of contrast (or a peak
image intensity or darkness) at a certain time after the injection
of the contrast agent. Accordingly, the image frames that include
high contrast in the selected region at the parameter time for the
arterial phase can be included for the reconstruction of the
arterial phase. In other words, the arterial pixel 240 will have
high contrast during the arterial phase. Thus, any pixel in the
image data with high contrast during the selected time or selected
image frames of the arterial phase will be used in the
reconstruction of the arterial phase. It will be understood, that
the arterial region 240 in the arterial phase can be a single pixel
or group of pixels selected either prior to the reconstruction
determination or during the reconstruction determination that meets
the contrast or position parameter. Various parameters can also
include the speed of wash or change in intensity of the selected
region, such as at the arterial pixel 240, which is known based
upon speed of movement of the contrast agent through the
vasculature 152 of the patient 14. Thus, the change in the arterial
pixel intensity can be used to confirm that a pixel, such as the
arterial pixel 240, is an arterial phase pixel that should be
selected for performing the reconstruction in block 222 of the
arterial particular phase.
[0078] Another input parameter can include constraining which image
frames relate to selected phases. For example, that image frames 5
through 95 of a series of image frames, based upon a speed of the
image data acquisition and speed of movement of the imaging device
16, can include the arterial phase. If a pixel shows a high
contrast during these frames, particularly when compared to other
frames, that pixel (e.g. the arterial pixel 240) can be determined
to be in the arterial phase. Accordingly, the time of injection of
the contrast agent and the time of the frames collected after the
injection of the contrast agent can be used for the determination
of the phase that is imaged in the selected frame and this
determination is used for determining which phase should be
reconstructed with image data from that frame.
[0079] Similarly, the venous phase pixel 242 can have similar wash
or selected wash parameters to determine that the venous pixel 242
is within the venous phase. The wash parameters of selected frames
can be based on the speed of movement of the contrast agent with
the patient 14. For example, it can be determined that image frames
110 through 220, of a series of frames, of the acquired image data
can be those that relate to the venous phase based upon the speed
of wash of the contrast agent through the vasculature 152 of the
patient 14. The change in intensity of the venous pixel 242 within
the image data over time can be used to identify a venous phase. As
illustrated in FIG. 5C, by the dotted portion in the late venous
phase 236, the contrast agent is washing through or past the venous
pixel 242. The timing associated with the image frame illustrated
in FIG. 5C can be used to determine that the contrast agent (and
thus image data due to the presence of the contrast agent) is
within the venous phase or some portion of the venous phase.
[0080] Once the image data is collected with the contrast agent
injected, the image data is correlated, as discussed above, and a
reconstruction of the vasculature can occur. Regardless of the
reconstruction method used, a display of selected vasculature
phases can be made on the display device 20 as illustrated in FIGS.
6A and 6B. The reconstruction can be a volumetric or
three-dimensional reconstruction. Due to the determination of
specific phases and the parameters discussed above, the
reconstruction algorithm can be used to reconstruct separate and
distinct phases of the anatomy. For example, the early and late
arterial phase 230, 234 can be illustrated together as a single
arterial phase 245 based upon the parameters discussed above,
including the limitations of the imaging device 16. The arterial
phase model 245 can include a volumetric display of the entire
arterial phase within the region of interest selected in block 214.
Additionally, as illustrated in FIG. 6B, a venous phase model can
include both the early and late venous phases 234, 236 and can be
illustrated as a single venous phase model 247. Again, the number
of phases can be selected by the user 12 or be based upon
limitations of the imaging device 16. Nevertheless, the display
device 20 can display either or both of the phases or any of the
phases selected for the region of interest.
[0081] Once the reconstruction of the models is made in block 222,
it can be displayed in block 260, and a determination of whether a
procedure is to be performed can be made in block 266. If no
procedure is to be performed, then the NO path 268 can be followed
to the end block 270. When no procedure is to be performed the
image data, including the reconstructed models from block 222, can
be used for analysis of the patient 14. For example, the structure
of the vasculature can be determined based upon the
three-dimensional models including any blockages, embolisms, or the
like.
[0082] If it is determined that a procedure is to be performed in
block 266, then a YES path 276 can be followed to register the
three-dimensional model to the subject in block 278. The
registration of the model to the subject in block 278 can be based
upon the registration techniques discussed above. For example, the
image data is acquired with the imaging system 16 and the position
of the imaging device 16 relative to the patient 14 can be known
based upon the movement of the imaging device 16 relative to the
patient 14 and/or tracking the imaging device 16 and the patient
14. The known position of the imaging device 16 relative to the
patient 14 can be used to register the models that are generated
with the image data frames acquired of the patient at the known
locations. Additionally, reference devices or fiducials can be
positioned in the patient 14 to determine registration of known
locations relative to the generated models.
[0083] Once the image data and the models are registered, an
instrument can be tracked in block 280. The instrument can be any
appropriate instrument, such as an ablation catheter or other
selected instrument. An icon 284 can be displayed on the display
device 22 to represent the location of the instrument relative to
the model, as illustrated in FIG. 7 in block 282. The icon 284 can
illustrate the location of the tracked instrument relative to the
reconstruction of the selected phase, such as, for example, the
arterial phase 230, 232. Accordingly, tracking the instrument
within the patient 14 can be made and displayed on the display
device to allow the user 12 to determine a location of the
instrument relative to the vasculature 152 of the patient 14. A
procedure can be performed in block 284 and the method can then end
in block 270. The procedure can be any appropriate procedure such
as an ablation near a heart, a stent placement, an embolism repair,
etc.
[0084] Accordingly, a reconstruction of various phases of the
vasculature 152 of the patient 14 can be made based upon the
selected parameters of the image data acquisition and contrast
agent within the patient 14, as discussed above. This can allow for
reconstruction of portions of the patient 14 that are generally
indistinguishable or not easily distinguished based on various
imaging modalities. This can allow for reconstruction of models,
including three-dimensional volumetric models, based upon acquired
serial image frames of the patient 14. The parameters of the
perfusion of the contrast agent within the patient 14 and
properties of the imaging device 16 can be used for determination
and selection of frames of the image data and portions of the
phases that can be reconstructed. Thus, even if a single phase can
not be imaged by an entire 360 degree rotation of an imaging device
relative to the patient 14, a single phase can still be
reconstructed using the parameters and constraints discussed above.
The reconstruction can be based upon parameters of time, movement
of the contrast agent, and the like, and can be used to
substantially volumetrically generate three-dimensional
reconstructions based upon the limited acquired image data.
[0085] The foregoing description of the embodiments has been
provided for purposes of illustration and description. It is not
intended to be exhaustive or to limit the invention. Individual
elements or features of a particular embodiment are generally not
limited to that particular embodiment, but, where applicable, are
interchangeable and can be used in a selected embodiment, even if
not specifically shown or described. The same may also be varied in
many ways. Such variations are not to be regarded as a departure
from the invention, and all such modifications are intended to be
included within the scope of the invention.
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