Method and apparatus for aligning a multi-modality imaging system

A target object for aligning a multi-modality imaging system includes a body having a cavity therein, a first imaging source being disposed within the cavity, the first imaging source including a body having a cavity defined therein and an emission responsive material disposed within the first imaging source cavity, the first imaging source having a first shape, and a second imaging source being disposed within the cavity, the second imaging source including a body having a cavity defined therein and a magnetic resonance responsive material disposed within the second imaging source cavity, the second imaging source having a second shape that is different than the first shape. A method of aligning a multi-modality imaging system is also provided.

BACKGROUND OF THE INVENTION

The subject matter disclosed herein relates generally to imaging systems capable of operation in multiple modalities, and more particularly to an apparatus and method for aligning a multi-modality imaging system.

Multi-modality (also referred to herein as multi-modal) imaging systems are capable of scanning using different modalities, such as, for example, but not limited to, Positron Emission Tomography (PET) and Magnetic Resonance Imaging (MRI). The difference between multi-mode and multi-modality is that in multi-mode systems the same hardware is utilized to perform scans in different modes (e.g., a radiation source and a radiation detector is used in both a flouro mode and a tomosynthesis mode). In a multi-modal system, although some of the same hardware is utilized to perform different scans (e.g., an image produced by PET is processed and displayed respectively, by the same computer and display, as an image produced by MRI), the data acquisition systems (also referred to a modality units) are different. For example, on a PET/MRI system, a radiopharmaceutical is typically employed in tandem with a PET camera to acquire PET data and a radio frequency (RF) coil is used to acquire MRI data.

In multi-modality systems, for example, an integrated PET/MRI system, the PET data and MRI data should be inherently registered with one another. Since the patient lies still on the same table during the PET and MRI portions of the acquisition, the patient should be in a consistent position and orientation during the two acquisitions, greatly simplifying the process of correlating and fusing the PET and MRI images. Inherent registration of the PET images and MRI images assumes a known alignment of the PET and MRI coordinate systems, consisting of at least a known spatial transformation between the two coordinate systems. Misalignment of the coordinate systems can result in a mis-registration of the images between the two imaging modes.

BRIEF DESCRIPTION OF THE INVENTION

In one embodiment, a target object for aligning a multi-modality imaging system is provided. The target object includes a body having a cavity therein, a first imaging source being disposed within the cavity, the first imaging source including a body having a cavity defined therein and an emission responsive material disposed within the first imaging source cavity, the first imaging source having a first shape, and a second imaging source being disposed within the cavity, the second imaging source including a body having a cavity defined therein and a magnetic resonance responsive material disposed within the second imaging source cavity, the second imaging source having a second shape that is different than the first shape.

In another embodiment, an alignment object for aligning a multi-modality imaging system is provided. The alignment object includes a body and a plurality of target objects installed in the body. At least one of the target objects includes a first imaging source being disposed within the cavity, the first imaging source including a body having a cavity defined therein and an emission responsive material disposed within the first imaging source cavity, the first imaging source having a first shape, and a second imaging source being disposed within the cavity, the second imaging source including a body having a cavity defined therein and a magnetic resonance responsive material disposed within the second imaging source cavity, the second imaging source having a second shape that is different than the first shape.

In a further embodiment, a method of aligning a multi-modality imaging system is provided. The method includes imaging a plurality of target objects with the first modality unit to generate an emission image data set. At least one of the target objects includes a body having a cavity therein, a first imaging source being disposed within the cavity, the first imaging source including a body having a cavity defined therein and an emission responsive material disposed within the first imaging source cavity, the first imaging source having a first shape, and a second imaging source being disposed within the cavity, the second imaging source including a body having a cavity defined therein and a magnetic resonance responsive material disposed within the second imaging source cavity, the second imaging source having a second shape that is different than the first shape. The method further includes determining a location of the target objects in the emission image data set to produce emission target object location coordinates, calculating a positional alignment vector for each target object based on the emission target object location coordinates, and aligning the multi-modality imaging system based on the positional alignment vectors.

DETAILED DESCRIPTION OF THE INVENTION

Described herein are various embodiments for aligning a multi-modality imaging system, which in some embodiments is a dual-modality imaging system. Various embodiments utilize an alignment object that includes at least two sources to facilitate aligning the two imaging modalities that form the dual-modality imaging system. The alignment object is reconfigurable to enable the alignment object to be utilized with various imaging systems.

FIG. 1is an end view of an exemplary alignment object10that may be used to align an exemplary multi-modality imaging system, such as the multi-modality imaging system300shown inFIG. 9.FIG. 2is a side view of the alignment object10shown inFIG. 1.FIG. 3is a top view of the alignment object10shown inFIG. 1.FIG. 4is a bottom view of the alignment object10shown inFIG. 1. In various embodiments, the multi-modality imaging system300includes a magnetic resonance imaging (MRI) system302and a positron emission tomography (PET) imaging system304. It should be realized that other modalities may be utilized with the dual-modality imaging system300. Other modalities include, for example, a computed tomography (CT) imaging system and a single photon emission computed tomography (SPECT) imaging system.

In the exemplary embodiment, the alignment object10includes a partially cylindrical body12and a plurality of target objects14embedded within the body12. The body12has a first end16and an opposite second end18. The alignment object10has an edge surface20that is disposed between the first end16and the second end18. In various embodiments, the edge surface20is defined by a curved upper surface22, a lower surface24, a first side26and a second side28. In various embodiments, the lower surface24may be formed as a curve that has a shape that is substantially similar to the curvature of an imaging table, such as an imaging table312shown inFIG. 9. In operation, the curvature of the body's lower surface24facilitates limiting the movement of the alignment object10when placed on the imaging table312. In the exemplary embodiment, the body12is fabricated from a material that does not produce significant signal loss for either modality, such as attenuation for PET, and hence is made from a foam such as polyurethane material, for example. Specifically, the body12may be fabricated from any material that holds the target objects14in a dimensionally stable position within the body12and does not affect the generation of either the PET emission image data or the MRI image data used to align the multi-modal imaging system300. AlthoughFIGS. 1-4illustrate the alignment object10as having a substantially spherical shape and a curved lower surface, it should be realized that this shape is exemplary only. The alignment object10may have any shape that facilitates aligning the multi-modal imaging system300.

As shown inFIGS. 1-4, the alignment object10also includes the plurality of target objects14embedded in the body12. In the exemplary embodiment, the alignment object10includes five target objects14. Optionally, the alignment object10may include more than five target objects14to increase the accuracy of the data by providing duplicate target objects14within the alignment object10. In another embodiment, the alignment object10may include less than five target objects14.

The target objects14are each located within the body12to enhance the imaging system alignment process. Specifically, each target object14is located over the field of view of the alignment object10along the x-axis, y-axis, and z-axis. For example, referring again toFIGS. 1-4, the target objects14, in one embodiment, are embedded within the alignment object10at predetermined locations that are selected to achieve an optimal measurement between the PET emission data and the MRI data. Accordingly, it should be realized that the target objects14may located at different positions within the alignment object10based on the tradeoffs of the multi-modality imaging system being aligned. For example, the target objects14may be located at different positions within the alignment object10when aligning a CT/PET imaging system.

The arrangement of the target objects14is explained with respect to the x-axis which extends substantially horizontally through the alignment object10from the first side surface26to the second side surface28, the y-axis which extends from the upper surface22to the lower surface24, and the z-axis which extends from the first end16to the second end18. In various embodiments, the alignment object10includes a first target object30that is disposed along the y-axis and is located proximate to the upper surface22of the alignment object10. A second target object32is disposed along the y-axis and is located proximate to the lower surface24. A third target object34is also disposed along the y-axis and is located proximate to the second end18and is also disposed between the first target object30and the second target object32. The alignment object10also includes a fourth target object36that is disposed along the x-axis and is located proximate to the first side26and a fifth target object38that is also disposed along the x-axis and is located proximate to the second side28.

FIG. 5is a side perspective view of an exemplary target object100that may be utilized with the alignment object10shown inFIGS. 1-4. More specifically, the target object100may be embodied as any or all of the target objects14shown inFIGS. 1-4. In various embodiments, the target object100includes a body102having a substantially cylindrical shape. Optionally the body102may have other shapes, such as for example, triangular, square, or any multi-sided shape. Accordingly, and in the exemplary embodiment, the body102is substantially hollow to define a cylindrical cavity104therein. In various embodiments, the body102has a first opening106that is defined at a first end108of the body102and a second opening110that is defined at a second end112of the body102, which are opposite end in this exemplary embodiment.

The target object100further includes a first end cap120that is configured to be removably coupled to the first end108and seal the first opening106. In operation, the first end cap120is configured to form a substantially fluid-tight seal of the first opening106such that various imaging sources, discussed in more detail below, that are placed within the target object100are sealed within the cavity104. In other embodiments, the target object100may also include a second end cap122that is configured to be removably coupled to the second end112and seal the second opening110such that the various imaging sources that are disposed within the target object100are sealed within the cavity104. In various other embodiments, the target object100does not include the second end cap122. Rather, the second end112is formed from a substantially solid material and is fabricated unitarily with the body102such that no removable end cap is utilized. More specifically, the body102may be fabricated to include only the one opening, i.e., the first opening106, such that only one end cap, i.e. the end cap120, is utilized to seal the various imaging sources within the cavity104.

As described above, the target object100is configured to retain a plurality of imaging sources within the cavity104. More specifically, and in various embodiments, the target object100includes at least a first imaging source130and a second different imaging source132. Imaging source, as used herein, is defined as an object that includes an imaging medium that is scannable by the multi-modality imaging system to generate information that is utilized to align the multi-modality imaging system. In various embodiments, the first imaging source130is a radioactive imaging source130that is scannable by the PET imaging modality to generate PET alignment information. Moreover, the second imaging source132is a MR imaging source132that is scannable by the MR imaging modality to generate MR alignment information. In various embodiments, and as shown inFIG. 5, the target object100also includes a third imaging source134that in the exemplary embodiment, is a second emission source132that is scannable by the PET imaging system to generate additional PET alignment information. In various embodiments, the first imaging source130is disposed between the second and third imaging sources132and134within the cavity104.

FIG. 6is an exploded view of a portion of the target object100shown inFIG. 5. More specifically,FIG. 6is an exploded view of the first, second and third imaging sources130,132and134shown inFIG. 5. Referring again toFIG. 6, the first imaging source130has a first shape. In various embodiments, the first imaging source130has a spherical shape. More specifically, the first imaging source130has a body140that is formed as a sphere. The body140has an outer diameter142that, in the exemplary embodiment, is substantially equal to an inner diameter144of the target object body102shown inFIG. 5. In various embodiments, the outer diameter142of the first imaging source130may be slightly less than the inner diameter144of the target object cavity104to enable the first imaging source130to be inserted into the target object cavity104. Moreover, the outer diameter142may be slightly less than the inner diameter144to enable the first imaging source130to be friction fit within the target object cavity104to substantially prevent the first imaging source130from moving after being positioned within the target object cavity104.

The first imaging source body140defines a cylindrical or spherical, cavity146therein. The body140may be fabricated using a plastic material, such as for example, a clear polyvinylchloride material. Optionally, the body140may be fabricated from any other material suitable for performing PET imaging. In various embodiments, the first imaging source130is filled with a substantially solid radioactive imaging source material148that is scannable by the PET imaging modality to generate PET alignment information. In one embodiment, the source material148is a germanium isotope, such as for example, Ge-68. Optionally, the source material148may be other isotopes utilized to perform PET imaging procedures. Accordingly, the combination of the body140and the source material148form the substantially solid spherical imaging source130that facilitates reducing and/or eliminating any potential source material leakage that may occur if a liquid source material is utilized.

In various embodiments, the second imaging source132has a second shape that is different than the shape of the first imaging source130. In the exemplary embodiment, the second imaging source132has a cylindrical shape. The second imaging source132includes a body150having a substantially cylindrical shape. Optionally the body150may have other shapes, such as for example, triangular, square, or any multi-sided shape. In the exemplary embodiment, the shape of the body150is substantially the same as the shape of the target object body102to enable the second imaging source132to be inserted within the target object body102. Accordingly, the body150is substantially hollow to define a cylindrical cavity152therein. In various embodiments, the body150has a first opening154that is defined at a first end156of the body150and an opposing second opening158that is defined at a second end160of the body150.

The second imaging source132includes a first end cap162that is configured to be removably coupled to the first end156to form a substantially fluid-tight seal of the first opening154. In operation, the first end cap162is configured to seal the first opening154such that an MR source material170is sealed within the cavity152. In various embodiments, the second imaging source132may also include a second end cap164that is configured to be removably coupled to the second end160and seal the second opening158such that the source material170is sealed within the cavity152. In various other embodiments, the second imaging source132does not include the second end cap164. Rather, the second end160is formed from a substantially solid material and is fabricated unitarily with the body150such that no removable end cap is utilized. More specifically, the body150may be fabricated to include only the one opening, i.e., the first opening154such that only one end cap, i.e. the end cap162is utilized to seal the source material170within the cavity152.

The body150has an outer diameter172that, in the illustrated embodiment, is substantially equal to the inner diameter144of the target object body102shown inFIG. 5. More specifically, the outer diameter172of the second imaging source132may be slightly less than the inner diameter144of the target object cavity104to enable the second imaging source132to be inserted into the target object cavity104. Moreover, the outer diameter142may be slightly less than the inner diameter144to enable the second imaging source132to be friction fit within the target object cavity104to substantially prevent the second imaging source132from moving after being positioned within the target object cavity104.

In use, the opening154or the opening158may be utilized by a user to access the interior volume152of the second imaging source132to facilitate filling the cavity152with the MR source material170. In the exemplary embodiment, the MR source material170is a liquid MR-visible contrast medium. Accordingly, the body150forms the hollow cavity152that is configured to store the MR contrast medium170. Moreover, once the MR contrast medium170is disposed within the cavity152, the lid162may be secured to the body150to substantially seal the MR contrast medium170within the cavity152. Moreover, the removable lid162enables the user to remove the MR contrast medium170and replace the MR contrast medium with a different source material to align different MR imaging systems or other imaging modalities.

As described above, and in various embodiments, the target object100may also include the third imaging source134. The third imaging source134also has a shape that is substantially the same as the shape of the second imaging source132and thus is different than the shape of the first imaging source130. In the exemplary embodiment, the third imaging source134has a cylindrical shape. The third imaging source134includes a body180having a substantially cylindrical shape. Optionally the body180may have other shapes, such as for example, triangular, square, or any multi-sided shape. In the exemplary embodiment, the shape of the body180is substantially the same as the shape of the target object body102to enable the third imaging source134to be inserted within the target object body102. Accordingly, and in the exemplary embodiment, the body180is substantially hollow to define a cylindrical cavity182therein.

In various embodiments, the body180has a first opening184that is defined at a first end186of the body180and an opposing second opening188that is defined at a second end190of the body180. The third imaging source134also includes a first end cap192that is configured to be removably coupled to the first end186and seal the first opening184. In operation, the first end cap192is configured to seal the first opening184such that a MR source material194is sealed within the cavity182. In various embodiments, the MR source material194is the same as the MR source material170in the second imaging source132. In other embodiments, the MR source material194may be different than the MR source material170. In various embodiments, the third imaging source134may also include a second end cap196that is configured to be removably coupled to the second end190and seal the second opening188such that the source material194is sealed within the cavity182. In various other embodiments, the third imaging source134does not include the second end cap196. Rather, the second end190is formed from a substantially solid material and is fabricated unitarily with the body180such that no removable end cap is utilized. More specifically, the body180may be fabricated to include only the one opening, i.e., the first opening184such that only one end cap, i.e. the end cap192is utilized to seal the source material194within the cavity182.

The body180has an outer diameter198that, in the exemplary embodiment, is substantially equal to the inner diameter144of the target object body102shown inFIG. 5. More specifically, the outer diameter198of the third imaging source134may be slightly less than the inner diameter144of the target object cavity104to enable the third imaging source134to be inserted into the target object cavity104. Moreover, the outer diameter198may be slightly less than the inner diameter144to enable the third imaging source134to be friction fit within the target object cavity104to substantially prevent the third imaging source134from moving after being positioned within the target object cavity104.

In use, the opening184or the opening188may be utilized by a user to access the cavity182of the third imaging source134to facilitate filling the cavity182with the MR source material194. In the exemplary embodiment, the MR source material194is also a liquid MR-visible contrast medium. Accordingly, the body180forms the hollow cavity182that is configured to store the MR contrast medium194. Moreover, once the MR contrast medium194is disposed within the cavity182, the lid192may be secured to the body180to substantially seal the MR contrast medium194within the cavity182. Moreover, the removable lid192enables the user to remove the MR contrast medium194and replace the MR contrast medium with a different source material to align different MR imaging systems or other imaging modalities.

FIG. 7is a flow chart illustrating an exemplary method200of determining component misalignment in a multi-modality imaging system including a first modality unit and a second modality unit.FIG. 8is a flowchart illustrating detailed portions of the method200shown inFIG. 7. As shown inFIG. 7, the method200includes imaging at202the plurality of target objects14with the first modality unit302to generate an MR image data set and imaging at204the plurality of target objects14with the second modality unit304to generate an emission image data set. A location of the target objects14is then determined at206in the MR image data set and also determined at208in the emission image data set to produce emission target object location coordinates and MR target object locations. The method200also includes calculating at210a transformation matrix using the locations of the target objects14based on the emission target object location coordinates and the MR target object coordinates, and using at212, the transformation matrix as the definition of the coordinate system alignment between the two modalities in the system. The transformation serves as the mechanism to align images from one system to the other.

Referring toFIG. 8, the aligning at212of the multi-modality imaging system300based on the positional alignment vectors includes performing at220a software alignment of the multi-modality imaging system300when at least one of the positional displacement vectors is greater than or equal to the predetermined tolerance value. In the exemplary embodiment, the predetermined tolerance value, may be for example, greater than approximately five millimeters.

To perform the method200, the alignment object10is positioned within the multi-modality imaging system300(shown inFIG. 9). In various embodiments, the portion of the multi-modality imaging system300that lies generally outside the field of view (FOV) of the alignment object10may be masked to reduce noise in the generated image data sets.

The alignment object10is then scanned using the MR imaging system302to generate the MR image data set380(shown inFIG. 10). The alignment object10is also scanned with the PET imaging system304(shown inFIG. 9) to generate an emission image data set382(shown inFIG. 10) which may both form part of the same multi-modality imaging system300. A location of the target objects14in the MR image data set is determined. A location of the target objects14is also determined in the emission image data set. In the exemplary embodiment, the alignment object10includes five target objects14. The location or position of the five target objects14in the MR image data set is determined at206to generate the MR target object location coordinates. The location or position of the same five target objects14in the emission image data set is determined at208to generate the emission target object location coordinates. A single emission target object coordinate represents a location of a single target object14in 3D space in the emission image data set. Moreover, a single MR target object coordinate represents a location of the same target in 3D space in the MR image data set. In the exemplary embodiment, assuming five target objects14are imaged, method200includes determining a location of the five target objects14in the emission image data set and producing a single object location coordinate for each target object14in the emission image data set. Additionally, method200includes determining a location of the five target objects in the MR image data set and producing a single object location coordinate for each target object in the MR image data set.

The location of the features within the emission image data set is then determined. The location of the same features within the MR image data is also determined. A transformation is then determined based upon the offset (x,y,z) and rotation (α, β, γ) as determined from the difference in locations of the same features within the two image sets. A set of positional displacement vectors represent the spatial difference of the target objects14in three-dimensional space between the target object14located in the emission image data set and the same target object14located in the MR image data set. For example, calculating at210a positional alignment vector for each target object14based on the emission target object location coordinates and the MR data target object location coordinates. In the exemplary embodiment, the positional alignment vector is calculated by determining the special location difference by subtracting an emission object location coordinates from the respective MR object locations coordinates, for example, to generate a single positional displacement vector for each target object14observed in both the emission image data set and the MR image data set.

In the exemplary embodiment, since the alignment object10includes five target objects14, five positional displacement vectors, one for each target object14is calculated. The positional displacement vectors are then used to calculate a misalignment of the imaging table312relative to the PET imaging system304or the MR imaging system302, and/or to calculate a misalignment between the PET imaging system304and the MR imaging system302.

In one embodiment, if at least one of the calculated positional displacement vectors is greater than a predetermined tolerance value, the method200includes performing at220the software alignment. It should be realized that predetermined tolerance value is exemplary only and may be either increased or decreased based on the sensitivity of the imaging systems being aligned. For example, a software alignment may be performed when the predetermined tolerance value is equal to ten, i.e. the displacement in 3D space between a target object14located in the emission image data set is less than ten millimeters from the same target object14located in the MR image data set. The predetermined tolerance value may be selected between a range of approximately 3 millimeters and approximately 15 millimeters.

To perform the software alignment, the positional displacement vectors are stored in a computer, such as the computer320shown inFIG. 9, for example, of the multi-modality imaging system300. During patient scanning, if the patient is scanned with both the PET imaging system304and the MR imaging system302, the computer320utilizes the positional displacement vectors to properly align the emission image data set with the MR image data set during the registration process.

Optionally, if at least one of the calculated positional displacement vectors is greater than the predetermined tolerance value, a hardware or mechanical alignment may be performed, such as, for example, the mechanical alignment procedure described in U.S. Pat. No. 7,103,233 which is commonly owned.

The software and/or mechanical alignment inform a user or an installer of the system300as to a table alignment status (i.e., whether or not the table is misaligned with either the first modality unit302or the second modality unit304, or more typically, both units because the units are substantially aligned to each other). Specifically, both the αTand βTparameters are utilized to align the imaging table312, and the other six parameters are used to align the PET unit304with the MM unit302. The installer can then re-align the table (adjust the axis of the table) with the gantry of the imaging system and repeat the herein described methods to verify if the re-aligned system is misaligned or not. Additionally, as discussed above, the installer may perform a software alignment after the above described hardware alignment is completed. For example, the PET gantry roll can be corrected in the reconstruction software.

There is therefore provided efficient and cost effective methods and apparatus for determining component misalignment in multi-modal imaging systems. The herein described methods utilize both the PET emission data and the MR image data to generate the positional displacement vectors. The positional displacement vectors are the utilized to calculate various table alignment parameters, such as the αTand βTparameters while simultaneously determining gantry alignment through parameters Px, Py, Pz, αP, βP, and γP. More specifically, the alignment object10described herein may be utilized to align a multi-modality imaging system, such as the imaging system300shown inFIG. 9. The alignment object10is simple and robust. At least some of the imaging sources within the alignment object10may be filled or refilled with an MR contrast agent that is tailored to a specific MR system. Moreover, in some embodiments, at least one imaging source is solid such that the imaging source does not leak. Accordingly, the alignment object10may be readily extended and customized to differing MR configurations.

In various embodiments, the alignment object10and the methods described herein may be implemented with a multi-modality imaging system. For example,FIGS. 9,10, and11illustrate embodiments of a multi-modality imaging system300that may be aligned using the method200and the alignment object10. The multi-modality imaging system300may be any type imaging system, for example, different types of medical imaging systems, which in various embodiments, is an MRI system in combination with one of, for example, a PET system or a SPECT system capable of generating diagnostic images. Moreover, the various embodiments are not limited to medical imaging systems for imaging human subjects, but may include veterinary or non-medical systems for imaging non-human objects, etc., as well as non-imaging applications, such as radiation therapy.

Referring toFIG. 9, the multi-modality imaging system300includes a first modality unit302and a second modality unit304. The two modality units enable the multi-modality imaging system300to scan an object or patient305in a first modality using the first modality unit302, which in this embodiment is MR and to scan the patient305in a second modality using the second modality unit304, which in this embodiment is PET. The multi-modality imaging system300allows for multiple scans in different modalities to facilitate an increased diagnostic capability over single modality systems. In one embodiment, the multi-modality imaging system300is an MR/PET imaging system and in another embodiment the multi-modality imaging system300is an MR/SPECT imaging system.

The imaging system300is shown as including a gantry306that is associated with the first modality unit302, which is an MR scanner, and a gantry308that is associated with the second modality unit304which is the PET scanner. During operation, the patient305is positioned within a central opening310, defined through the imaging system300, using, for example, a motorized table312.

The gantry306includes MR imaging components, for example, one or more magnets as described in more detail herein. The gantry308includes imaging components for example, at least one gamma detector or camera. The imaging system300also includes an operator workstation316. During operation, the motorized table312moves the patient305into the central opening310of the gantry306and/or308in response to one or more commands received from the operator workstation316. The workstation316then operates the first and second modality units302and304to, for example, both scan the patient305in MR and acquire MR data and/or acquire emission data of the patient305. The workstation316may be embodied as a personal computer (PC) that is positioned near the imaging system300and hard-wired to the imaging system300via a communication link318. The workstation316may also be embodied as a portable computer such as a laptop computer or a hand-held computer that transmits information to, and receives information from, the imaging system300. Optionally, the communication link318may be a wireless communication link that enables information to be transmitted to or from the workstation316to the imaging system300wirelessly. In operation, the workstation316is configured to control the operation of the imaging system300in real-time. The workstation316is also programmed to perform medical image diagnostic acquisition and reconstruction processes described herein.

The operator workstation316includes a central processing unit (CPU) or computer320, a display322, and an input device324. In the exemplary embodiment, the computer320executes a set of instructions that are stored in one or more storage elements or memories, in order to process information received from the first and second modality units302and304. For example, in various embodiments, the computer316may include a set of instructions to implement the method100described herein. The storage elements may also store data or other information as desired or needed. The storage element may be in the form of an information source or a physical memory element located within the computer320. The set of instructions may include various commands that instruct the computer320as a processing machine to perform specific operations such as the methods and processes of the various embodiments described herein.

The computer320connects to the communication link318and receives inputs, e.g., user commands, from the input device324. The input device324may be, for example, a keyboard, mouse, a touch-screen panel, and/or a voice recognition system, etc. Through the input device324and associated control panel switches, the operator can control the operation of the first and second modality units302and304and the positioning of the patient305for a scan. Similarly, the operator can control the display of the resulting image on the display322.

Referring toFIG. 10, the imaging system300includes the imaging portion302and a processing portion344that may also include a processor or other computing or controller device, such as illustrated inFIG. 9. The imaging system300includes within a helium vessel351a superconducting magnet348formed from coils, which may be supported on a magnet coil support structure. The helium vessel351surrounds the superconducting magnet348and is filled with liquid helium.

Thermal insulation352is provided surrounding all or a portion of the outer surface of the helium vessel351. A plurality of magnetic gradient coils354, such as the x, y, and z gradient coils described above, are provided inside the superconducting magnet348and an RF transmit coil356is provided within the plurality of magnetic gradient coils354. In some embodiments, the RF transmit coil356may be replaced with a transmit and receive coil. The components within the gantry306generally form the imaging portion302. It should be noted that although the superconducting magnet348is a cylindrical shape, other shapes of magnets can be used.

The processing portion344generally includes a controller358, a main magnetic field control360, a gradient field control362, a memory364, a display device, embodied as the monitor366, a transmit-receive (T-R) switch368, an RF transmitter370and a receiver372.

In operation, a body of an object, such as a patient or a phantom to be imaged, is placed in the bore310on a suitable support, for example, a patient table. The superconducting magnet348produces a uniform and static main magnetic field Boacross the bore310. The strength of the electromagnetic field in the bore310and correspondingly in the patient, is controlled by the controller358via the main magnetic field control360, which also controls a supply of energizing current to the superconducting magnet348.

The magnetic gradient coils354, which include one or more gradient coil elements, are provided so that a magnetic gradient can be imposed on the magnetic field Boin the bore310within the superconducting magnet348in any one or more of three orthogonal directions x, y, and z. The magnetic gradient coils354are energized by the gradient field control362and are also controlled by the controller358.

The RF transmit coil356, which may include a plurality of coils, is arranged to transmit magnetic pulses and/or optionally simultaneously detect MR signals from the patient if receive coil elements are also provided, such as a surface coil configured as an RF receive coil. The RF receive coil may be of any type or configuration, for example, a separate receive surface coil. The receive surface coil may be an array of RF coils provided within the RF transmit coil356.

The RF transmit coil356and the receive surface coil are selectably interconnected to one of the RF transmitter370or receiver372, respectively, by the T-R switch368. The RF transmitter370and T-R switch368are controlled by the controller358such that RF field pulses or signals are generated by the RF transmitter370and selectively applied to the patient for excitation of magnetic resonance in the patient. While the RF excitation pulses are being applied to the patient, the T-R switch368is also actuated to disconnect the receive surface coil from the receiver372.

Following application of the RF pulses, the T-R switch368is again actuated to disconnect the RF transmit coil356from the RF transmitter370and to connect the receive surface coil to the receiver372. The receive surface coil operates to detect or sense the MR signals resulting from the excited nuclei in the patient and communicates the MR signals to the receiver372. These detected MR signals are in turn communicated to the controller358. The controller358includes a processor (e.g., image reconstruction processor), for example, that controls the processing of the MR signals to produce signals representative of an image of the patient.

The processed signals representative of the image are also transmitted to the monitor366to provide a visual display of the image. Specifically, the MR signals fill or form a k-space that is Fourier transformed to obtain a viewable image. The processed signals representative of the image are then transmitted to the monitor366.

FIG. 11is a diagram of an exemplary PET imaging system400that may form one of the modalities of the multi-modality imaging system300described above. More specifically, the second modality unit304may be the PET imaging system400. The PET imaging system400includes a detector ring assembly430including a plurality of detector scintillators. The detector ring assembly430includes the central opening410, in which an object or patient, such as the patient305may be positioned, using, for example, the motorized table. The scanning operation is controlled from the operator workstation416through a PET scanner controller436. A communication link438may be hardwired between the PET scanner controller436and the workstation416. Optionally, the communication link438may be a wireless communication link that enables information to be transmitted to or from the workstation416to the PET scanner controller436wirelessly. In the exemplary embodiment, the workstation416controls real-time operation of the PET imaging system400. The workstation416is also programmed to perform medical image diagnostic acquisition and reconstruction processes described herein. The operator workstation416includes the central processing unit (CPU) or computer420, the display422and the input device424. As used herein, the term “computer” may include any processor-based or microprocessor-based system configured to execute the methods described herein.

The methods described herein may be implemented as a set of instructions that include various commands that instruct the computer or processor420as a processing machine to perform specific operations such as the methods and processes of the various embodiments described herein.

During operation of the exemplary detector430, when a photon collides with a scintillator on the detector ring assembly430, the absorption of the photon within the detector produces scintillation photons within the scintillator. The scintillator produces an analog signal that is transmitted on a communication link446when a scintillation event occurs. A set of acquisition circuits448is provided to receive these analog signals. The acquisition circuits448produce digital signals indicating the 3-dimensional (3D) location and total energy of each event. The acquisition circuits448also produce an event detection pulse, which indicates the time or moment the scintillation event occurred.

The digital signals are transmitted through a communication link, for example, a cable, to a data acquisition controller452that communicates with the workstation416and the PET scanner controller436via a communication link454. In one embodiment, the data acquisition controller452includes a data acquisition processor460and an image reconstruction processor462that are interconnected via a communication link464. During operation, the acquisition circuits448transmit the digital signals to the data acquisition processor460. The data acquisition processor460then performs various image enhancing techniques on the digital signals and transmits the enhanced or corrected digital signals to the image reconstruction processor462as discussed in more detail below.

In the exemplary embodiment, the data acquisition processor460includes at least an acquisition CPU or computer470. The data acquisition processor460also includes an event locator circuit472and a coincidence detector474. The acquisition CPU470controls communications on a back-plane bus476and on the communication link464. During operation, the data acquisition processor460periodically samples the digital signals produced by the acquisition circuits448. The digital signals produced by the acquisition circuits448are transmitted to the event locator circuit472. The event locator circuit472processes the information to identify each valid event and provide a set of digital numbers or values indicative of the identified event. For example, this information indicates when the event took place and the position of the scintillator that detected the event. The events are also counted to form a record of the single channel events recorded by each detector element. An event data packet is communicated to the coincidence detector474through the back-plane bus476.

The coincidence detector474receives the event data packets from the event locator circuit472and determines if any two of the detected events are in coincidence. Coincident event pairs are located and recorded as a coincidence data packets by the coincidence detector474. The output from the coincidence detector474is referred to herein as image data. In one embodiment, the image data may be stored in a memory device that is located in the data acquisition processor460. Optionally, the image data may be stored in the workstation416.

The image data subset is then transmitted to a sorter/histogrammer480to generate a data structure known as a histogram. The image reconstruction processor462also includes a memory module482, an image CPU484, an array processor486, and a communication bus488. During operation, the sorter/histogrammer480performs the motion related histogramming described above to generate the events listed in the image data into 3D data. This 3D data, or sinograms, is organized in one exemplary embodiment as a data array490. The data array490is stored in the memory module482. The communication bus488is linked to the communication link476through the image CPU484. The image CPU484controls communication through communication bus488. The array processor486is also connected to the communication bus488. The array processor486receives the data array490as an input and reconstructs images in the form of image arrays492. Resulting image arrays492are then stored in the memory module482. The images stored in the image array492are communicated by the image CPU484to the operator workstation416. In the illustrated embodiment, the PET imaging system400also includes a memory494that may be utilized to store a set of instructions to implement the various methods described herein.

The various embodiments and/or components, for example, the modules, or components and controllers therein, such as of the imaging system400, also may be implemented as part of one or more computers or processors. The computer or processor may include a computing device, an input device, a display unit and an interface, for example, for accessing the Internet. The computer or processor may include a microprocessor. The microprocessor may be connected to a communication bus. The computer or processor may also include a memory. The memory may include Random Access Memory (RAM) and Read Only Memory (ROM). The computer or processor further may include a storage device, which may be a hard disk drive or a removable storage drive such as an optical disk drive, solid state disk drive (e.g., flash RAM), and the like. The storage device may also be other similar means for loading computer programs or other instructions into the computer or processor.