Patent ID: 12189006

DETAILED DESCRIPTION

Although various embodiments that incorporate the teachings of the present disclosure have been shown and described in detail herein, those skilled in the art can readily devise many other varied embodiments that still incorporate these teachings. The scope of the disclosure is not limited in its application to the exemplary embodiment details of construction and the arrangement of components set forth in the description or illustrated in the drawings. The disclosure encompasses other embodiments and of being practiced or of being carried out in various ways. Also, it is to be understood that the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of “including,” “comprising,” or “having” and variations thereof herein is meant to encompass the items listed thereafter and equivalents thereof as well as additional items. Unless specified or limited otherwise, the terms “mounted,” “connected,” “supported,” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Further, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings.

Referring toFIG.4, a front view of a gantry tube44used to form a PET gantry in accordance with an aspect of the invention is shown. The gantry tube44is part of an imaging system such as a magnetic resonance/positron emission tomography (MR/PET) imaging system90(seeFIG.8). The gantry tube44includes a first tube46located within a second tube48. The first tube46is positioned about the longitudinal axis40. The gantry tube44further includes a plurality of wall elements50connected between the first46and second48tubes. Each wall50extends between an outer surface52of the first tube46and an inner surface54of the second tube48to form a plurality of channels56between the first46and second48tubes. In accordance with an aspect of the invention, each channel56holds an associated PET detector74of the system90(FIG.8). Further, each channel56is configured to receive an associated PET detector74in an axial direction as will be described in connection withFIGS.7A-7B.

FIG.5depicts an enlarged view of an exemplary channel56. A size or width W of each wall50gradually increases as the wall50extends from the first tube outer surface52toward the second tube inner surface54to form a substantially triangularly or wedge-shaped wall50. This forms a channel56having a substantially rectangular shape suitable for receiving a single PET detector74. Alternatively, the channel56may have other shapes suitable for receiving a corresponding PET detector shape such as square shape, for example. An inner surface58(seeFIG.4) of the first tube46defines the patient bore12that receives a patient to be scanned.

Referring toFIG.6, a segment60of the gantry tube44is shown. In an embodiment, the segment60has a substantially curved shape and includes first62, second64, third66and fourth68channels. The gantry tube44may be formed by joining several segments60. For example, the segments60may be joined on a mandrel using adhesives and mechanical locking features. In aspect of the invention, assembly of the segments60on a mandrel provides a uniform and repeatable surface for the RF screen22(seeFIG.8). In particular, the RF screen22is placed on the mandrel before the segments60are bonded together and to the RF screen22.

The segment60may be fabricated using a polymer material and is formed by a pultrusion process that enables formation of thin walls suitable for forming the channels56. It has been found by the inventors herein that the pultrusion technique may be used to form a segment60having a single channel56although the formation of additional channels56, such as three or more channels56, has been found to provide more suitable results. Further, a segment60that includes a channel56that is not desired may be removed by machining away the channel56. For example, a single channel56may be machined away from a segment60having an odd number of channels56. In an alternative method of fabrication, a large autoclave is used to join segments60that are made from pre-impregnated materials. The segments60are then cured under the vacuum and heat of the autoclave to form the gantry tube44.

Referring toFIGS.7A and7B, perspective patient70and service72end views of the gantry tube44are shown. The gantry tube44and channels56are oriented in a longitudinal direction about the longitudinal axis40. In accordance with an aspect of the invention, the longitudinal orientation of each channel56enables insertion of a PET detector74(exemplary PET detector74is shown inFIGS.7A and7B) in each channel56, or the removal of a PET detector74from a channel56, in an axial direction (i.e., as shown by arrow76) substantially parallel to the longitudinal axis40. The gantry tube44is stationary and thus the PET detectors74are inserted or removed without moving or extending the gantry tube44relative to a remaining portion of the system90.

A patient is received into the patient bore12via the patient end70(FIG.7A). Servicing of the gantry tube44may be performed via the service end72(FIG.7B) which is opposite the patient end70. The channels56extend between the patient70and service72ends. In accordance with an aspect of the invention, each PET detector74may be inserted into an associated channel56in the axial direction76via the patient end70or the service end72.

First78and second80support rings are located on the patient70and service72ends, respectively, of the gantry tube44. The support rings78,80may be removably attached to the gantry tube44and serve as an anchor point for the body coil14of the MRI portion of the system90. In an embodiment, the first78and second80support rings are attached to an outer diameter82of the second tube48at the patient end70and an inner diameter84of the first tube46at the service end72, respectively, of the gantry tube44. This enables mounting of the gantry tube44inside the gradient coil18while still allowing access to the PET detectors74positioned in the channels56and shims that are used to adjust a position the gradient coil18. Further, the support rings78,80provide additional stiffness to the gantry tube44.

The support rings78,80are located outside of a field of view of the PET detectors74such that they do not attenuate a PET signal generated by the PET portion of the system90. The support rings78,80are optimally placed for mounting the gantry tube44to the system90. In accordance with an aspect of the invention, the body coil14, a component that is easily damaged in service, may be exchanged without removing the gantry tube44.

Each segment60may be fabricated from a polymer enhanced with glass fiber such as glass reinforced plastic. Alternative materials having slight to moderate electrical conductivity, such as carbon fiber, polymers enhanced with copper or metallic additives and metallic meshes may be used to provide both structural strength and shielding against electromagnetic interference (EMI) generated during operation of the system90. In particular, a balance must be achieved between providing proper shielding and the effects of eddy current heating on a conductive structure. In accordance with an aspect of the invention, a metallic surface86may be formed on an inside surface88of at least one channel56to form a waveguide. For example, the metallic surface86may be a metallic coating that is applied to the inside surface88or a metallic foil that is laminated on to the inside surface88.

It has been found by the inventors herein that the pultrusion process produces segments60that are highly stable and precise. The geometry and reproducibility of the inner surface58of the first tube46is acceptable when a mandrel is used. A shape of an RF screen carrier should be precise and the inner surface of the segment60provides a suitable surface for the screen while adding no extra supporting features. Further, gaps between PET detectors74are minimized and the polymer profile in front of the PET detectors74has low attenuation. For example, the gaps may be approximately 1-3 mm in size.

Referring toFIG.8, a front view of an MR/PET imaging system90is shown that includes the gantry tube44of the invention. The system90includes the patient bore12that receives a patient to be scanned, body coil14, gantry tube44that forms a part of a PET gantry92, gradient coil18, superconducting magnet20and the RF screen22located on the first tube inner surface58.

In an aspect of the invention, a gantry tube44for a system90is disclosed that enables insertion or removal of PET detectors74in and out of associated channels56of the gantry tube44by sliding the PET detectors74in and out of the associated channels56in an axial direction76at either the patient end70or service72end of the gantry tube44. Access to the PET detectors74is provided without removing the gantry tube44from the magnet20, thus reducing system downtime and the risk of damage to equipment. Since the gantry tube44does not move and remains inside the gradient coil18, only a simple attachment to the magnet20is needed thus simplifying the mechanical structure of the system90(i.e., no rails, bearing, backplanes, etc. are needed). The risk of injury from moving a heavy gantry is substantially reduced and specialty tools are not required for performing service. In addition, the invention provides a known and reproducible surface to attach an RF shield of the body coil14. Further, the RF cabin (i.e., a scan room wherein system90is located) may be optimized and reduced in size since the gantry tube44does not extend from the system90and thus an extended PET gantry length does not factor into room size requirements. In addition, the material used to fabricate the gantry tube44has low attenuation for the PET signal and gantry fabrication is very precise allowing for the accurate location of each PET detector74in the gantry tube44.

In an alternative embodiment, the PET gantry92including gantry tube44may be integrated directly into the gradient coil18. In this embodiment, the effects of vibration and heat on the PET detectors74should be minimized since both are detrimental to the associated electronics and operation of the PET detector74.

Another embodiment would convolve the body coil14and PET gantry92. In this embodiment, the PET detectors74reside within a radio frequency alternating field (B1) reflow space generated by the system90and would require significantly higher levels of EMI shielding. In addition, associated cabling may cause an antenna effect (due to currents on the cable shields). Further, shielded structures in this volume would be parasitic and require more power to offset the effect.

While particular embodiments of the present disclosure have been illustrated and described, it would be obvious to those skilled in the art that various other changes and modifications can be made without departing from the spirit and scope of the disclosure. It is therefore intended to cover in the appended claims all such changes and modifications that are within the scope of this disclosure.