Imaging system phantom

Abstract: A phantom for a real-time interactive imaging system (10) is described. The phantom includes a plurality of segments (36) having unique identifiers (40), the segments joining together to form a polyhedron around an inner plate (48). In one embodiment, the inner plate has a unique identifier (50) and two inner blocks (52) positioned orthogonally upon it, each inner block also having a unique identifier (54) . The phantom provides a variety of uniquely identified surfaces, angles and edges for scanning practice in a real-time interactive environment, and enables the imaging system user to verify image correctness and annotation.

Description: This invention relates generally to an imaging system and, more particularly, to a phantom for use with an imaging system. Medical imaging systems include a source that emits signals (including but not limited to x-ray, radio frequency, or sonar signals), and the signals are directed toward an object to be imaged. The emitted signals and the interposed object interact to produce a response that is received by one or more detectors. The imaging system then processes the detected response signals to generate an image of the object. With real-time interactive imaging systems, a user controls movement of system components in three-dimensional space while performing scans. Inexperienced operators often have difficulty in visualizing the object in three-dimensional space and maneuvering the system in three dimensions while scanning. In addition, proper verification of image orientation and image annotation is difficult, particularly for double angle oblique scans acquired in real time. An imaging system phantom comprising a plurality of segments coupled to each other to verify image orientation are known from US-A-4,618,978. According to a first aspect of the invention, there is provided a phantom for use with an imaging system, said phantom comprising: a plurality of segments, each said segment coupled to at least one other said segment to enclose a volume, each said segment having a unique segment identifier; and an inner plate positioned within said volume, said inner plate coupled to at least one said segment. The inner plate may comprise a unique plate identifier. The phantom may further comprise at least one inner block positioned within said volume, each said inner block disposed upon said inner plate. Each inner block may comprises a unique block identifier. The plurality of segments may substantially form a polyhedron which may comprise twenty segments. Each segment may be substantially a triangle. Each segment identifier may outline an opening through each corresponding segment. Each said segment identifier may comprise at least one alphanumeric character and may further comprise a period. The segments and the inner plate may comprise a plastic material. The plate identifier may outline an opening through the inner plate and each block identifier may outline an opening through each said corresponding inner block. The plate identifier may comprises at least one alphanumeric character and may further comprises a period. Each block identifier may comprise at least one alphanumeric character and may further comprises a period. The phantom may comprises at least one inner block substantially orthogonal to the inner plate. It may comprise at least two said inner blocks substantially orthogonal to one another. According to a second aspect of the invention, there is provided an imaging object for use with an imaging system, said imaging object comprising: a phantom comprising a plurality of segments, each said segment coupled to at least one other said segment to enclose a volume, each said segment having a unique segment identifier, said phantom further comprising an inner plate positioned within said volume, said inner plate coupled to at least one said segment; and a stand coupled to and supporting said phantom. The stand may comprise a base and a support member. The stand may comprises a plastics material. The imaging system may include a table for supporting objects to be imaged and the stand may be configured to orient the inner plate horizontally as the phantom rests on the table. A container may be configured to receive the phantom and the stand and may comprise a means for sealing liquid inside the container. According to a third aspect of the invention, there is provided a method for verifying correctness of image orientation and image annotation in an imaging system, the imaging system including a source and a detector, said method comprising the steps of: orienting a phantom at a particular location relative to the imaging system, the phantom including a plurality of segments and an inner plate, each segment having a unique segment identifier, the plate having a unique plate identifier; generating an image of the phantom; and comparing the generated image to the configuration and orientation of the phantom. The phantom may include at least one inner block, at least one of the inner blocks being orthogonal to the inner plate, and the step of orienting a phantom at a particular location relative to the imaging system may comprises the step of aligning the inner blocks and the inner plate orthogonally to the imaging system. Each inner block may have a unique block identifier, and the step of generating an image of the phantom may comprises the step of orienting the source relative to the phantom's segment identifiers, plate identifier and block identifiers. Each segment identifier may outline an opening through the corresponding segment, the plate identifier may outline an opening through the inner plate, each block identifier may outline an opening through the corresponding inner block; and the step of orienting the source relative to the phantom's segment identifiers, plate identifier and block identifiers may comprise orienting the source for image projection through one or more of the openings outlined by the segment identifiers, plate identifier and block identifiers in the corresponding segments, plate or blocks. The step of generating an image of the phantom may comprise the steps of: orienting the source for image projection relative to a particular segment, the inner plate or a particular inner block; and generating an image of such segment, inner plate or inner block. The method may further comprise the step of: placing the phantom within a container; and filling the container with a liquid. The imaging system may be a real-time interactive imaging system. Thus, present invention, in one aspect, is a phantom that facilitates training operators with respect to positioning the image system components, and includes an inner plate enclosed and supported by a plurality of segments which join together to form an icosahedron. Each segment includes a unique identifier, for example, an alphanumeric character. Two inner blocks are seated on the inner plate which, together with the inner blocks, indicate orthogonal planes (i.e. axial, sagittal, and coronal). The inner plate and inner blocks have unique identifiers that, together with the segment identifiers, are used to orient the imaging system source during imaging. The invention will now be described in greater detail, by way of example, with reference to the drawings, in which:- Figure 1 is a pictorial view of an MRI imaging system. Figure 2 is an elevational view of an embodiment of a phantom. Figure 3 is an exploded perspective view of the phantom shown in Figure 2. Referring to Figure 1, major components of an MRI imaging system 10 include an operator console 12 from which the operator controls imaging system 10. A system control 14 receives commands from the operator indicating the scan sequence to be performed and transmits imaging control signals to an MRI scanner 16. Within a cylindrical bore 18 of scanner 16, patient or object 20 is positioned on a table 22 and is surrounded by a magnetic coil or detector 24. Magnetic coil 24 is part of a magnet assembly 26, which also includes a polarizing magnet 28. Polarizing magnet 28 subjects object 20 to a uniform magnetic field. A transmitter or source 30 included in system control 14 transmits radio frequency pulses to magnet assembly 26. The resulting signals emitted by the excited spins in object 20 are picked up by magnetic coil 24, transmitted to system control 14 and reconstructed into an image by an image processor 32. The operator of imaging system 10 is able to view the image on console 12. If imaging system 10 is interactive in real time, the operator is able to view images and alter the scan sequence as it progresses. In one embodiment and as shown in Figure 2, a phantom 34 for use with imaging system 10 includes twenty triangular segments or sides 36. Segments 36 are coupled together to form a substantially polyhedral shape enclosing a volume 38. Each segment 36 includes a unique segment identifier 40. Phantom 34 is coupled to and supported by a stand 42, which includes a base 44 and a support member 46. Figure 3 is an exploded view of phantom 34. As shown in Figure 3, phantom 34 includes an inner plate 48 surrounded by and connected to several segments 36. Inner plate 48 includes a unique plate identifier 50. Two inner blocks 52 are positioned over inner plate 48. Each inner block 52 includes a unique block identifier 54. Each segment identifier 40, block identifier 54 and plate identifier 50 includes an alphanumeric character 56 and also includes a period 58. Each segment identifier 40 outlines an opening 62 through the corresponding segment 36. In the same manner, each block identifier 54 outlines an opening 66 through the corresponding inner block 52, and plate identifier 50 outlines an opening 70 through inner plate 48. Imaging quality often is enhanced, particularly in the case of an MRI imaging system, by submerging phantom 34 in liquid, e. g. water. Therefore, in one embodiment, a container (not shown) is configured to receive phantom 34 and stand 42. The container then is filled with a liquid, sealed and placed on table 22 for imaging. Segments 36, inner plate 48, inner blocks 52, and stand 42, in an exemplary embodiment, are fabricated from acrylic sheet and joined together with Weld-On 40 adhesive available from IPS Corporation, Compton, CA 90220. When phantom 34 is in use, openings 62, 66 and 70 are visible from multiple directions and are used to identify the direction from which phantom 34 is being viewed. Inner blocks 52 and inner plate 48 are orthogonal to one another, thereby providing orthogonal axes for imaging system alignment purposes. For example, as shown in Figure 3, block identifiers 54 and plate identifier 50 are denoted as "A.", "S." and "C." respectively, to indicate axial, sagittal and coronal planes. Stand 42 is configured to orient inner plate 48 horizontally when phantom 34 is positioned on table 22. An imaging system user prepares for imaging by orienting phantom 34 on table 22 at a particular location relative to imaging system 10. Specifically, inner blocks 52 and inner plate 48 are aligned orthogonally to imaging system 10. In generating an image of phantom 34, an imaging system user orients source 30 relative to a particular segment 36, inner plate 48, and/or a particular inner block 52. The user then generates an image of segment 36, inner plate 48, and/or inner block 52 for comparison with the known configuration and orientation of phantom 34. In orienting source 30 to produce an image, the imaging system operator uses segment identifiers 40, plate identifier 50, and (if present in the particular embodiment) block identifiers 54 as guides in maneuvering in three dimensions. Based on the image generated, the operator can ascertain whether the desired positioning was achieved. The above described phantom facilitates and shortens time needed for training imaging system operators, particularly for interactive real-time imaging systems. Specifically, the phantom provides a variety of surfaces, angles and edges in scanning locations known to the imaging system operator. The phantom enables an operator to practice scanning from many directions, or alternatively to generate images to verify an imaging system's image correctness and annotation. Alternative embodiments of the phantom include segments 36, inner plate 48 and inner blocks 52 of shape and number other than those described above and that join together to form a polyhedron other than an icosahedron. Segment, plate and block identifiers other than alphanumeric characters followed by periods also can be used. Further, the phantom and stand can be fabricated from materials other than acrylic, such as other plastics. In addition, although the invention has been described occasionally with reference to a MRI system, the invention is not limited to use with MRI systems, and may be used with other types of imaging systems.

Claims: A phantom (34) for use with an imaging system (10), said phantom comprising: a plurality of segments (36), each of said segments coupled to at least one the other said segments to enclose a volume (38), each of said segments having a unique segment identifier (40); and an inner plate (48) positioned within said volume, said inner plate coupled to at least one of said segments. A phantom (34) in accordance with Claim 1 wherein said inner plate (48) comprises a unique plate identifier (50). A phantom (34) in accordance with Claim 2 further comprising at least one inner block (52) positioned within said volume (38), each of said inner blocks disposed upon said inner plate (48). A phantom (34) in accordance with Claim 3 wherein each of said inner blocks (52) comprises a unique block identifier (54). An imaging object for use with an imaging system (10), said imaging object comprising: a phantom (34) in accordance with Claim 1 and a stand (42) coupled to and supporting said phantom. A imaging object in accordance with Claim 5 wherein said stand (42) comprises a base (44) and a support member (46). An imaging object in accordance with Claim 5 wherein said stand (42) comprises a plastics material. A method for verifying correctness of image orientation and image annotation in an imaging system (10), the imaging system including a source (30) and a detector (24), said method comprising the steps of: orienting a phantom (34) at a particular location relative to the imaging system, the phantom including a plurality of segments (36) enclosing a volume (38) and an inner plate (48) positioned within said volume, each segment having a unique segment identifier (40), the plate having a unique plate identifier (50); generating an image of the phantom; and comparing the generated image to the configuration and orientation of the phantom. A method in accordance with Claim 8 wherein the phantom (34) includes at least one inner block (52), at least one of the inner blocks being orthogonal to the inner plate (48), and wherein the step of orienting a phantom at a particular location relative to the imaging system (10) comprises the step of aligning the inner blocks and the inner plate orthogonally to the imaging system. A method in accordance with Claim 8 wherein each inner block (52) has a unique block identifier (54), and wherein the step of generating an image of the phantom (34) comprises the step of orienting the source (30) relative to the phantom's segment identifiers (40), plate identifier (50) and block identifiers (54).

Inventors: KOSAK DONALD E, LIGHTFOOT LANCE L, PERSOHN JAMES L, KOSAK, DONALD E., LIGHTFOOT, LANCE L., PERSOHN, JAMES L.
Applicants: GEN ELECTRIC, GENERAL ELECTRIC COMPANY
Application year: 2000
Main classification: A61B6
IPC codes: G09B23, G01R33, A61B5, A61B6