Patent Application
20120061581
The invention relates generally to non-invasive imaging such as single photon emission computed tomography (SPECT) imaging. More particularly, the invention relates to imaging systems configured to reconstruct images from projections acquired with a mixture of two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing (projection overlap).
Single photon emission computed tomography (SPECT) is used for a variety of imaging applications, particularly in medical imaging. In general, SPECT systems are imaging systems that are configured to generate an image based upon the interaction of gamma photons (generated by a nuclear decay event) in a gamma-photon detector. In medical and research contexts, these detected gamma photons may be processed to formulate an image of organs or tissues beneath the skin.
To produce an image, one or more detector assemblies may be rotated around a subject. Detector assemblies are typically comprised of various structures working together to receive and process the incoming gamma photons. For instance, the detector assembly may utilize a scintillator assembly (e.g., large sodium iodide scintillator plates) to convert the incoming gamma photons into visible or ultraviolet light photons for detection by an optical sensor. This scintillator assembly may be coupled by a light guide to multiple photomultiplier tubes (PMTs) or other light sensors that convert the light photons from the scintillator assembly into electric signals. In addition to the scintillator assembly-PMT combination, pixilated solid-state direct conversion detectors (e.g., Cadmium-Zinc-Telluride, CZT) may also be used to generate electric signals directly from the impact of the incoming photons. These electric signals can be transferred, converted, and processed by electronic modules in a data acquisition module to facilitate viewing and manipulation by clinicians.
Typically, SPECT systems further include a collimator assembly that may be attached to the front of the gamma-ray detector. In general, the collimator assembly is designed to absorb photons such that only photons traveling in certain directions are allowed to impact the detector assembly. In certain instances, pinhole-aperture collimators may be used. Pinhole-aperture collimators are generally collimators with one or more small pinhole apertures therein. Photons passing through these pinhole apertures generally project an inverted image of at least a portion of the source onto the detector assembly.
In general, the system resolution and geometric efficiency are at least partially based on both the pinhole offset (i.e., the distance from a source to a pinhole aperture) and the focal length (i.e., the distance from a pinhole aperture to the detector assembly). For example, the image may be magnified if the pinhole offset is less than the focal length. In a similar manner, the image may be minified if the pinhole offset is greater than the focal length. The system resolution is based on the size of the pinhole aperture, the magnification, and the intrinsic detector resolution.
Furthermore, the quality of the image reconstruction is at least partially based on the degree of multiplexing (i.e. projection image overlap) on the gamma photon detector. More pinhole apertures may be placed in the collimator assembly to increase the geometric efficiency, but this may also increase the degree of multiplexing. If only multiplexed projections are available from a complex source distribution, then it is likely that the reconstructed image will contain aliasing artifacts, since the reconstruction algorithm cannot determine through which pinhole aperture a particular photon passed. In general, there must be at least some non-multiplexed portions of the projections to enable the image reconstruction algorithm to produce images without aliasing artifacts.
In accordance with one embodiment, the present invention provides an imaging system. The imaging system includes a collimator assembly having one or more apertures therein. The imaging system further includes a detector assembly configured to generate one or more signals in response to gamma photons that pass through the one or more apertures. The imaging system is configured so that two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing are included in the projection data from which images are reconstructed.
In accordance with one embodiment, the present invention provides an imaging system. The imaging system includes a collimator assembly having one or more apertures therein. The imaging system further includes a detector assembly configured to generate one or more signals in response to gamma photons that pass through the one or more apertures. The imaging system is configured so that two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing are included in the projection data from which images are reconstructed. The imaging system is further configured so that a pinhole collimator and a detector are arranged in a combined assembly, such that a pinhole-detector module can be moved with respect to the source.
In accordance with another embodiment, the present invention provides a method of changing collimator performance. The method includes exchanging the one or more pinhole apertures in the collimator assembly.
In accordance with another embodiment, the present invention provides a method of changing collimator performance. The method includes exchanging the mechanical assembly that combines a pinhole collimator and a detector into a pinhole-detector module for an assembly with a different focal length.
In accordance with another embodiment, the present invention provides a method of imaging a volume. The method includes positioning at least a portion of a subject in a field of view of a single photon emission computed tomography system. The method further includes collimating gamma photons emitted from the subject using one or more pinhole-detector modules. Each pinhole-detector module comprises a collimator having one or more pinhole apertures and a detector assembly. The method further includes detecting gamma photons that pass through the one or more pinhole apertures with the corresponding detector assembly. The method further includes generating one or more signals in response to the detected gamma photons. The method further includes selecting a mixture of pinhole-detector modules having two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing.
According to an embodiment, an imaging system includes a collimator assembly having two or more apertures, and a detector assembly configured to generate two or more signals in response to gamma photons that pass through the two or more apertures. The collimator assembly and the detector assembly are configured to provide two or more different spatial imaging resolutions or two or more different degrees of multiplexing.
According to an embodiment, an imaging system includes first and second pinhole-detector modules arranged about an imaging volume. Each pinhole-detector module includes a collimator having one or more pinhole apertures therein, and a detector assembly configured to generate one or more signals in response to gamma photons that pass through the one or more pinhole apertures. The first pinhole-detector module has a first spatial imaging resolution, and the second pinhole-detector module has a second spatial imaging resolution different from the first spatial imaging resolution.
According to an embodiment, a method of imaging a subject in an imaging volume is provided. The method includes providing a single photon emission computed tomography imaging system with a collimator assembly and a detector assembly arranged about an imaging volume, placing a subject within the imaging volume, collimating gamma photons emitted from the subject through the collimator assembly, detecting the gamma photons with the detector assembly, and generating first and second signals in response to the detected gamma photons The first signal represents a first spatial imaging resolution of the detector assembly configured with the collimator assembly, and the second signal represents a second spatial imaging resolution of the detector assembly configured with the collimator assembly. The method also includes generating an image from the first and second signals.
According to an embodiment, a method of conducting single photon emission computed tomography imaging is provided. The method includes providing a first pinhole collimator and a first detector having a first focal length, providing a second pinhole collimator and a second detector having a second focal length different from the first focal length, focusing the first and second pinhole collimators based on a desired image resolution or sensitivity, and concurrently imaging a subject with the first and second pinhole collimators and detectors.
These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein:
As illustrated, a subject support 24 (e.g. a table) may be moved into position in a field of view of the SPECT system 10. In the illustrated embodiment, the subject support 24 is configured to support a subject 28 (e.g., a human patient, a small animal, a plant, a container, a porous object, etc.) having an imaging volume in a position for scanning. Alternatively, the subject support 24 may be stationary, while the SPECT system 10 may be moved into position around the subject 28 having the imaging volume for scanning. Those of ordinary skill in the art will appreciate that the subject 28 may be supported in any suitable position for scanning. By way of example, the subject 28 may be supported in the field of view in a substantially vertical position, a substantially horizontal position, or any other suitable position (e.g., inclined) for the desired scan. In SPECT imaging, the subject 28 is typically injected in a vein with a solution that contains a radioactive tracer. The solution is distributed and absorbed throughout the subject 28 in different degrees, depending on the tracer employed and, in the case of living subjects, the functioning of the organs and tissues. The radioactive tracer emits electromagnetic quanta (e.g., gamma photons), also known as “gamma rays” during a nuclear decay event, represented on
As previously mentioned, the SPECT system 10 includes collimator assembly 12 that collimates the gamma photons 30 emanating from the subject 28 positioned in the field of view. The collimator assembly 12 may be disposed between the detector assembly 3 and the subject 28 and may contain a shield 7 composed of radiation-absorbent material (or one or more radiation-absorbent panels), such as lead or tungsten, for example. In general, the collimator assembly 12 is configured to limit and define the direction and angular divergence of the gamma photons 30. In accordance with embodiments of the present invention, the collimator assembly 12 includes a pinhole collimator having one or more pinhole apertures therein. The shield 7 and collimator assembly 12 may be composed of the same material and may be continuous or constructed of overlapping pieces.
As will be discussed in more detail with respect to the following figures, at least two different focal lengths (i.e., the length between a pinhole aperture in the collimator assembly 12 and the detector assembly 3) of the pinhole apertures may be employed. This results in at least two different spatial resolutions and/or at least two different degrees of multiplexing for the projection images. In a SPECT system employing a plurality of detectors with other conventional collimator assemblies (i.e., parallel-hole, diverging-hole, converging-hole, slant-hole, etc.), the at least two different spatial resolutions may be accomplished, for example, by attaching a high-resolution collimator to at least one detector head and a high-sensitivity collimator to at least one different detector head (as shown in
In one embodiment, the collimator assembly 12 (or collimator) having the one or more apertures therein and the detector assembly 3 are together referred to as a collimator-detector module, and two or more of the collimator-detector modules are configured to have two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing. When the collimator is a pinhole aperture collimator, the collimator-detector module may be referred to as a pinhole-detector module. In other embodiments, other types of collimators include slit aperture collimators, parallel hole collimators, and converging and diverging collimators.
Referring again to
The gamma photons 30 that pass through the pinhole apertures in the collimator assembly 12 impact the detector assembly 3. Due to the collimation of the gamma photons 30 by the collimator assembly 12, the detection of the gamma photons 30 may be used to determine the line of response along which each of the gamma photons 30 traveled before reaching, impacting, and interacting inside the detector assembly 3, allowing localization of each gamma photon's origin to that line. In general, the detector assembly 3 may include a plurality of detector elements configured to detect the gamma photons 30 emanating from the subject 28 in the field of view and passing through one or more pinhole apertures through the collimator assembly 12. In exemplary embodiments, each detector element produces an electrical signal in response to the impact of the gamma photons 30.
As will be appreciated by those of ordinary skill in the art, the detector elements of the detector assembly 3 may include any of a variety of suitable materials and/or circuits for detecting the impact and interaction of the gamma photons 30. By way of example, the detector elements may include a plurality of solid-state detector elements, which may be provided as one-dimensional or two-dimensional arrays. In another embodiment, the detector elements of the detector assembly 3 include a scintillation assembly and PMTs or other light sensors.
Moreover, the detector elements may be arranged in the detector assembly 3 in any suitable manner. By way of example, multiple detector assemblies 3 may extend at least partially around the field of view. In certain embodiments, the multiple detector assemblies 3 include modular-detector elements arranged around the field of view. Alternatively, the detector assemblies 3 may be arranged in a ring that may extend up to about 360° around the field of view. In certain exemplary embodiments, the multiple detector assemblies 3 extend from about 180° to about 360° around the field of view. The ring of detector elements may include flat panels or curved detector surfaces (e.g., a NaI annulus). In one exemplary embodiment, the ring includes in the range from 8-50 solid-state detector modules. Those of ordinary skill in the art will appreciate that the ring need not be circular, for example, the detector elements may be arranged in an elliptical ring or be contoured to the body profile of the subject 28. In addition, in certain exemplary embodiments, the detector assembly 3 is gimbaled on its support base, e.g., so that suitable arbitrary slice angles can be acquired.
In another exemplary embodiment, a ring of solid-state detectors is deployed within the magnetic field of an MRI system. The collimator assembly may be integrated with the RF transmit/receive coil (e.g., the collimator assembly is integrally provided with the RF transmit/receive coil). Also, the SPECT and MR images may be acquired sequentially or simultaneously.
In another exemplary embodiment as shown in
To acquire multiple lines of response emanating from the subject 28 in the field of view during a scan, the collimator assembly 12 may be configured to rotate about the subject 28 positioned within the field of view. In accordance with exemplary embodiments, the collimator assembly 12 is configured to rotate with respect to the detector assembly 3. By way of example, the detector assembly 3 may be stationary while the collimator assembly 12 may be configured to rotate about the field of view. Alternatively, the detector assembly 3 may rotate while the collimator assembly 12 is stationary. In certain exemplary embodiments, the collimator assembly 12 and the detector assembly 3 are both configured to rotate, either together or independent of one another. Alternatively, if sufficient pinhole apertures are provided in the collimator assembly 12, then no rotation may be required for image reconstruction.
As illustrated, SPECT system 10 further includes a control module 16. In the illustrated embodiment, the control module 16 includes one or more motor controllers 32 and a data-acquisition module 34. In general, the motor controller 32 may control the rotational speed and position of the detector assembly 3, the collimator assembly 12, and/or the position of the subject support 24. In addition, the motor controllers 32 may control position and orientation of individual detectors 3 which may move independently or in combination with sections of the collimator assembly 12. The data-acquisition module 34 may be configured to obtain the signals generated in response to the impact of the gamma photons 30 with the detector assembly 3. For example, the data-acquisition module 34 may receive sampled electrical signals from the detector assembly 3 and convert the data to digital signals for subsequent processing by the image reconstruction and processing module 18. Alternatively, the detector module 3 may directly generate digital signals that are transmitted to the data-acquisition module 34.
Those of ordinary skill in the art will appreciate that any suitable technique for data acquisition may be used with the SPECT system 10. By way of example, the data needed for image reconstruction may be acquired in a list or a frame mode. In one exemplary embodiment of the present invention, gamma photon events (e.g., the impact of gamma photons 30 on the detector assembly 3), gantry 26 motion (e.g., collimator assembly 12 motion, detector assembly 3 position, and subject support 24 position), and physiological signals (e.g., heart beat and respiration) are acquired in a list mode. List mode is suitable in exemplary embodiments where the count rate is relatively low and many pixels record no counts at each gantry position or physiological gate. Alternatively, frames and physiological gates may be acquired by moving the gantry in a step-and-shoot manner and storing the number of events in each pixel during each frame time and heart or respiration cycle phase. Frame mode may be suitable, for example, where the count rate is relatively high and most pixels are recording counts at each gantry position or physiological gate.
In the illustrated embodiment, the image reconstruction and processing module 18 is coupled to the data-acquisition module 34. The signals acquired by the data-acquisition module 34 may be provided to the image reconstruction and processing module 18 for image reconstruction. The image reconstruction and processing module 18 may include electronic circuitry to receive acquired signals, and electronic circuitry to condition the acquired signals received from the data-acquisition module 34. Further, the image reconstruction and processing module 18 may include processing to coordinate functions of the SPECT system 10 and implement reconstruction algorithms suitable for reconstruction of the acquired signals. The image reconstruction and processing module 18 may include a digital-signal processor, memory, a central-processing unit (CPU) or the like, for processing the acquired signals. As will be appreciated, the processing may include the use of one or more computers. The addition of a separate CPU may provide additional functions for image reconstruction, including, but not limited to, signal processing of data received, and transmission of data to the operator workstation 20 and image display workstation 22. In one embodiment, the CPU is confined within the image reconstruction and processing module 18, while in another embodiment a CPU includes a stand-alone device that is separate from the image reconstruction and processing module 18.
The reconstructed image may be provided to the operator workstation 20. The operator workstation 20 may be utilized by a system operator to provide control instructions to some or all of the described components and for configuring the various operating parameters that aid in data acquisition and image generation. An image display workstation 22 coupled to the operator workstation 20 may be utilized to observe the reconstructed image. It should be further noted that the operator workstation 20 and the image-display workstation 22 may be coupled to other output devices, which may include printers and standard or special purpose computer monitors. In general, displays, printers, workstations and similar devices supplied with the SPECT system 10 may be local to the data-acquisition components, or may be remote from these components, such as elsewhere within the institution or hospital, or in an entirely different location, linked to the image acquisition system via one or more configurable networks, such as the Internet, virtual private networks, and so forth. By way of example, the operator workstation 20 and/or the image reconstruction and processing module 18 may be coupled to a remote-image display workstation 36 via a network (represented on
Furthermore, those of ordinary skill in the art will appreciate that any suitable technique for image reconstruction may be used with the SPECT system 10. In one exemplary embodiment, iterative reconstruction (e.g., ordered subsets expectation maximization, OSEM) is used. Iterative reconstruction may be suitable for certain implementations of the SPECT system 10 due, for example, to its speed and the ability to tradeoff reconstruction resolution and noise by varying the convergence and number of iterations.
While in the illustrated embodiment, the control module 16 (including the data-acquisition module 34 and the motor controller 32) and the image reconstruction and processing module 18 are shown as being outside the detector assembly 3 and the operator workstation 20. In certain other implementations, some or all of these components are provided as part of the detector assembly 3, the operator workstation 20, and/or other components of the SPECT system 10.
Referring now to
By way of illustration, two exemplary lines of response 6 are shown connecting the field-of-view 1 to the detector 3 through the pinhole aperture 4. These limiting lines of response 6 define an opening angle 5. It will be understood that a pinhole aperture is generally a three-dimensional opening in an attenuating plate or cylinder, for example, which stops gamma photons that do not pass through a pinhole aperture 4. The three-dimensional shape of the aperture physically defines the opening angle. It will be appreciated by those of ordinary skill in the art that the cross-section of the pinhole aperture 4 may be circular or elliptical or polygonal and that the narrowest portion of the pinhole aperture may have a knife-edge or a keel-edge or a rounded edge. Each choice of shape and edge of the pinhole aperture 4 will affect the gamma photon projections and, hence, the resolution and geometric efficiency. If the image reconstruction faithfully represents the physics of gamma photon transmission and scatter through the pinhole aperture, then a faithful image can be formed from the projected data.
The geometric efficiency of a number N of pinhole apertures identical to the one illustrated in
G=N d
2 cos3(θ/2)/(4 b2), Eqn. [1]
where G is the geometrical efficiency in dimensionless units, N is the number of pinhole apertures 4, d is the effective diameter of the circular pinhole apertures 4, θ is the opening angle 5, and b is the distance from the subject (or the axis-of-rotation, as a representative fiducial) to the pinhole aperture 4. In a system that rotates about the axis of rotation 2 of
d=d
0+tan(θ/2) ln(2)/μ, Eqn. [2]
where d0 is the nominal diameter and μ is the linear attenuation coefficient of the collimator material (e.g., tungsten, lead, tantalum, gold, etc.) for gamma photons of the photopeak energy being imaged. The term ln(2)/μ will be recognized as the mean free path for gamma photons. It will be appreciated that the addition to the nominal diameter represents penetration of the knife edge by a portion of the gamma photons striking the region near the edge of the pinhole aperture 4.
With regard to Eqn. [1], it will be appreciated that the geometric efficiency G may be increased by modifying one or more parameters, including increasing the number of pinholes N, increasing the effective diameter of the pinholes d, increasing the opening angle θ, and/or decreasing the source-collimator distance b.
The system resolution of a pinhole aperture as illustrated in
R
det
=p/M, Eqn. [3]
where Rdet is the resolution due to the size of detector pixels p and the pinhole collimator magnification M:
M=f/b, Eqn. [4]
where the focal distance f is the distance between the pinhole and the detector and b, as above, is the source-collimator distance. The second component of resolution RPH depends upon the effective pinhole aperture 4:
R
PH
=d (1+1/M). Eqn. [5]
The system resolution Rsys is a quadrature sum of the detector and pinhole resolutions:
R
sys =√{square root over (Rdet2+RPH2)}. Eqn. [6]
It will be apparent to those of ordinary skill in the art that geometric efficiency, system resolution, and field-of-view can be traded off by varying one or more of the system design parameters (N, d, b, f p, θ, μ). This invention goes beyond the conventional trade-off choices that result in task-specific collimator designs (e.g., high resolution or general purpose or high sensitivity). This invention mixes together collimator assemblies 12 and detector assemblies 3 with two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing, resulting in an image featuring both the highest resolution and a higher geometric efficiency. It should be understood that to obtain an image featuring this high resolution and high geometric efficiency, sufficient spatial sampling of the subject should be acquired with both the high resolution and high sensitivity components. Sufficient sampling will depend on the particular subject, the dose given, the duration of imaging, the imaging task, and other variables, in order to acquire sufficient counts to create an image.
Refer now to
It will be appreciated that for the configuration of
Continuing with the discussion of the preferred embodiment, consider
Those with ordinary skill in the art will appreciate that only the central circular pinhole aperture 4, which has a central line of response 6 that is normally incident on the detector 3, will project a circle. The peripheral circular pinhole apertures 4, which have central lines of response 6 that are obliquely incident on the detector 3, will actually project ellipses. For simplicity of this particular illustration, circles 43 have been used.
It will be appreciated by those skilled in the art that the projection patterns shown in
Statistical image reconstruction, such as ML-EM (maximum-likelihood expectation-maximization) or OSEM (ordered subset expectation maximization), with full physics modeling of the pinhole collimators and detectors enables accurate image reconstruction of the data acquired by the system illustrated in
In another exemplary embodiment of this invention, the collimator assembly 12 consists of multiple pinhole apertures with a mixture of two or more different aperture sizes, and thus, two or more different spatial resolutions and efficiencies. If the number of higher-resolution/lower efficiency pinhole apertures is approximately or substantially the same as the number of lower-resolution/higher-efficiency pinhole apertures, then the reconstructed image resolution can be predominantly determined by the higher-resolution apertures and the system efficiency (and contrast) can be significantly increased by the higher-efficiency apertures. In one embodiment, the number of higher-resolution/lower efficiency pinhole apertures is the same as the number of lower-resolution/higher-efficiency pinhole apertures. In other embodiments the number of higher-resolution/lower efficiency pinhole apertures and the number of lower-resolution/higher-efficiency pinhole apertures are substantially the same, within about a factor of 2. In other embodiments, the numbers may differ within about a factor of 3, or up to a factor of 5.
In another exemplary embodiment of this invention, the mixing of two different degrees of multiplexing is achieved in time rather than in space. That is, the two data sets are acquired sequentially rather than simultaneously. In particular, during a portion of the acquisition time highly multiplexed projection data is acquired and during the remainder of the acquisition time only minimally multiplexed projection data is acquired. This reduction in multiplexing may be achieved mechanically by covering a portion of the pinhole apertures, thus decreasing both the degree of multiplexing and the system efficiency in order to provide the minimally-multiplexed portion of the data required for non-aliased image reconstruction.
In another exemplary embodiment of this invention, the mixing of two or more different spatial resolutions is achieved by adjusting the pinhole aperture sizes during the acquisition. In particular, during a portion of the acquisition time projections with a first characteristic resolution are acquired, then the pinhole aperture sizes are adjusted and the remainder of the projections is acquired. This change in aperture size may be achieved by using mechanically adjustable pinhole apertures, as taught in U.S. Pat. Nos. 7,723,690 and 7,439,514, which are incorporated by reference in their entity and attached herewith. Alternatively, the collimator assembly 12 may be fabricated with two or more pinhole aperture sizes and may be provided with a shutter mechanism that can alternately expose the first group and cover the second group of the apertures and then, in the midst of the acquisition time the shutter can be moved to expose the second group and cover the first group of the apertures.
In another exemplary embodiment of the invention, the mixing of two or more different spatial resolutions and two or more different degrees of multiplexing is achieved by moving the collimator assembly 12 and/or the detector assembly 3 after a portion of the acquisition time such that the magnification M (Eqn. [4]) is adjusted. This may be accomplished in the system of
Refer now to
In view of the above and according to one embodiment, the collimator assembly and the detector assembly are configured to have two or more different magnifications to achieve a mixture of two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing.
In one embodiment, the collimator assembly is configured to adjust the number of open apertures to achieve a mixture of two or more different degrees of multiplexing.
In one embodiment, the collimator assembly is configured to adjust the size of open apertures to achieve a mixture of two or more different spatial imaging resolutions.
In one embodiment, the collimator assembly and/or the detector assembly are/is configured to move to achieve a mixture of two or more different spatial imaging resolutions and/or two or more different degrees of multiplexing.
In one embodiment, two or more different focal lengths between a detector assembly and a pinhole collimator assembly are predetermined and fixed in a plurality of pinhole-detector modules. Here, the two or more different focal lengths may be predetermined based on image magnification and/or minification, or the two or more different focal lengths may be predetermined based on use of detector area for the pinhole apertures of the pinhole collimator, or the two or more different focal lengths may be predetermined based on size of an image field of view.
When the mixed resolution-efficiency projection data is reconstructed, the higher-resolution/lower-efficiency collimator will predominantly determine the reconstructed system resolution and the additional event counts provided by the higher-efficiency/lower-resolution collimator will improve the image contrast and, hence, the detectability of small features or small lesions. As noted before, the projection data for this mixed collimator pair should be acquired over a 180 degree range. If a 1/2-time acquisition is desired, the angular view sampling interval should be doubled and the 180 degree range should be maintained.
It will be appreciated by those skilled in the art that many alternative approaches may be taken to reconstruct images using the mixed resolution/multiplexing data. By way of illustration, one successful approach consists of statistical iterative image reconstruction using an ML-EM or OSEM approach. The lower resolution, minimally multiplexed (lower magnification) projection data subsets may be reconstructed first to form a lower resolution image. Then the data from the higher resolution, more multiplexed (higher magnification) projection data subsets may be added to the iterative reconstruction, using the lower resolution image as a starting point. In the experience of the inventive entity, this approach yields a final reconstructed image that combines the high spatial resolution of the higher magnification projections and the higher efficiency enabled by the lower magnification projections.
According to an embodiment, a method of imaging a subject is provided, as shown for example in
While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the following claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
This application claims priority to and the benefit of U.S. Provisional Application No. 61/381,276, filed Sep. 9, 2010, the entire content of which is expressly incorporated herein by reference.
| Number | Date | Country | |
|---|---|---|---|
| 61381276 | Sep 2010 | US |
