Combined tomography scanner

A combined tomography scanner is disclosed, having at least two imaging modalities. In at least one embodiment, the scanner includes a first tomography modality having an essentially annular or tubular measurement area opening formed by an inner perimeter; an annular or cylindrical PET component as a second tomography modality having an outer perimeter, which allows insertion into the measurement area opening, and having an inner opening which forms a patient tunnel; and at least one insulation mat which can be inserted into an annular gap between the inner perimeter of the first modality and the outer perimeter of the PET component.

PRIORITY STATEMENT

The present application hereby claims priority under 35 U.S.C. §119 on German patent application number DE 10 2007 009 180.1 filed Feb. 26, 2007, the entire contents of which is hereby incorporated herein by reference.

FIELD

Embodiments of the present invention generally relate to an imaging device. In one example embodiment, the present invention relates to an integrated measuring device having a magnetic resonance scanner and a positron emission tomograph.

BACKGROUND

Magnetic resonance scanners (MRI) use the physical principle that atomic nuclei in magnetic fields experience a precession movement of the nuclear spin of these atomic nuclei which can be measured and whose characteristic depends on the type of atomic nucleus. Magnetic resonance imaging uses this phenomenon for imaging by magnets, which are usually arranged in the form of a tube or annulus around a patient couch, inducing reactions of the atomic nuclei within the body of the patient, in which case these reactions can be detected by way of detectors and evaluated. Processing of the acquired data results in three dimensional images of the examined body; the images depend on the location within the body and the type of tissue.

Gradient coils (GC) which additionally modulate the applied magnetic field are used in MRIs. These GCs are usually arranged concentrically to a permanent-magnet field ring and generate temporary magnetic fields, developing noise and vibrations in the process. Furthermore, body coils (BC), a specific type of measurement receiver, are also often present and are also arranged concentrically to the other coils. This thus results in a concentric configuration of an MRI comprising a plurality of layers. The configuration of an MRI is known to a person skilled in the art.

Positron emission tomographs (PET) use a different physical principle for imaging inside the patient's body. In this case, a radiopharmaceutical is introduced into the body and can be stored in the most diverse organs and tissues of the body, depending on its respective metabolism. In the decay processes of the respective radionuclide (inter alia, PET uses18F,11C,13N or15O which emit positrons as they decay) used in the radiopharmaceutical, positrons are emitted which collide with electrons while they are still in the patient's body and are thus annihilated, releasing gamma radiation as secondary radiation in the form of two photons in the process. These photons move apart from each other at an angle of approximately 180°. This secondary radiation can be measured by suitable receivers. These receivers also surround the patient's body in the form of a tube or annulus, similar to the MRI. Generally, PET images lack anatomical information due to the display of metabolic processes or the information is very limited and restricted by the limited spatial resolution (approximately 4-5 mm). For a while, different manufacturers (inter alia General Electric) have been offering appliances, which combine a PET scanner with a computed tomography scanner (CT) as two “modalities”. Such a combination of PETs with MRI appliances is also planned for the near future.

This raises the question of the spatial arrangement of these two modalities. It is possible to arrange the two gantries in series and move the patient through the two detectors, one after the other. However, such an arrangement allows only time delayed acquisition of those body parts and is thus undesirable. For simultaneous operation of both modalities, closer spatial coupling of both modalities is required. One possible system component arrangement is to fit the PET detectors effectively within the other appliance, that is to say within the MRI for example, for instance between the GC and BC. However, such installation is complicated. A separate PET tube or PET ring offers great advantages with respect to maintainability and production. However, the main difficulties with such an approach are:Only very limited space is available for attaching the tube, moreover “radial installation space” is very expensive in MRIs.There is little space for a heat shield within the PET component; however, said heat shield is required due to the adjacently arranged GC, whose surface temperature can reach up to 80° C.The proximity of the PET component to the oscillating GC leads to vibrational coupling between the two via airborne sound and/or structure-borne sound; this not only causes a noise problem, but can also lead to a reduced service life of the PET component and impairment of its operation.There is thermal coupling to the GC, which can moreover be subject to surface temperature fluctuations. The PET electronics react sensitively to both temperature fluctuations and excessive temperature increases. Temperature fluctuations result in the deterioration of the signal and in noise.

SUMMARY

The inventors, in at least one embodiment, have discovered that it would therefore be desirable to find an approach for close spatial arrangement between both modalities without having to accept thermal or vibrational impairment of the PET measurement by the other modality, such as an MRI or CT.

At least one embodiment of the invention is based on the principle of fixing a PET component, which can be inserted into the tube or ring of the outer modality (for example, a CT or an MRI), with an insulation mat between both components.

Correspondingly, at least one embodiment of the invention relates to a combined tomography scanner having at least two imaging modalities, with a first tomography modality having an essentially annular or tubular measurement area opening formed by an inner perimeter; an annular or cylindrical PET component being the second tomography modality having an outer perimeter, which allows insertion into the measurement area opening, and having an inner opening which forms a patient tunnel; and having at least one insulation mat which can be inserted into an annular gap between the inner perimeter of the first modality and the outer perimeter of the PET component.

In one example embodiment, the first modality is a magnetic resonance scanner (MRI) or a computed tomography scanner (CT); the use of an MRI seeming more appropriate on account of the physical properties.

The term “insulation” in the insulation mat simultaneously refers to different types of insulation, in particular spatial isolation (separation), thermal insulation, acoustic insulation and vibrational insulation. It is self-evident that not all insulating functions have to be present in all embodiments of the invention at the same time.

The insulation mat preferably forms a complete ring or cylinder between inner perimeter and outer perimeter. It can be composed of a plurality of segments or a single piece (even if composed of a plurality of components).

In one example embodiment, the insulation mat provides essentially complete spatial fixing for the PET component in the measurement area opening. This fixes the PET component in its allotted position in the combined tomography scanner without further fastenings, in particular screw connections or holders made from metal, etc.

In one example embodiment, the insulation mat is intended for vibrational insulation.

Additionally, the insulation mat is preferably intended as an alternative to or addition to thermal insulation.

The volume of the insulation mat can be variable; this both modifies its insulating properties and also allows its removal from the device, and simple insertion and removal of the PET component, which is fixed by the insulation mat.

The volume can preferably be varied by inflating the insulation mat with a fluid. The fluid can be a liquid, for example a cooling liquid pumped into the mat, and/or a gas, for example compressed air or cooling air.

In one particularly example embodiment of the invention, the fluid is compressed air, which for example particularly fixes the PET components or presses them against specific areas of the mat.

The insulation mat may have a plurality of cells with a variable volume, which are distributed over the insulation mat. These vary in volume of the mat and can, for instance, be inflated with the abovementioned compressed air.

Furthermore, the insulation mat may have areas through which a coolant can flow. This can be any typically used coolant, including cold gases and specific liquids, or else simply water.

Furthermore, the insulation mat preferably has areas with vibration-isolating properties. These areas with vibration-isolating properties include, for example, vibration-damping materials which are inserted into the insulation mat.

The vibration-damping materials can be caoutchouc products and/or silicone rubbers.

The areas having vibration-isolating properties are preferably arranged in the lower half of the annular gap, to additionally use or compensate for gravitation acting on the PET component.

In one example embodiment, the variable-volume chambers, which can press the PET component onto the areas with vibration-isolating properties when their volume increases, are arranged in the upper area of the annular gap.

Furthermore, the insulation mat can comprise two sheets which are fused together, between which other elements can be arranged. This allows simple and economic production of the insulation mat from low-cost components.

In one example embodiment, the coefficient of friction of the surface of the insulation mat allows insertion into the annular gap.

DETAILED DESCRIPTION OF THE EXAMPLE EMBODIMENTS

Referencing the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, example embodiments of the present patent application are hereafter described. Like numbers refer to like elements throughout. As used herein, the terms “and/or” and “at least one of” include any and all combinations of one or more of the associated listed items.

An embodiment of the invention places an essentially cylindrical PET detector inside the tube or the ring of a further modality such as an MRI and fixes/insulates the PET detector by way of an insulation mat.

The PET tube is preferably arranged within the GC tube. The annular gap between both components required for tolerance compensation and play for installation is used both for a vibration-decoupled fixing and for the thermal decoupling between the two components. This function therefore does not require the provision of additional radial space in the components.

In this case, an insulation mat or a plurality of partial segments of an insulation mat, which is for example inserted into the remaining annular gap between the MR tube and the PET tube after the positioning of the PET component, implements all the required functions.

The insulation mat is welded together in suitable form, for example from two polyurethane sheets or similar materials, so that zones with channels having coolant flowing though them; zones to which compressed air can be applied; and zones for the vibrational decoupled fixing of the PET component are formed on the inner perimeter of the MRI tunnel.

One example of such a design is shown inFIG. 1. This shows, in a cross section in the direction of the patient tunnel, the layered structure of a device according to one exemplary embodiment one the invention in. An outer ring1schematically shows a first modality, for example an MRI ring. A PET component2, which is also annular, is inserted into this MRI ring and is fixed and insulated from the outer ring by means of an insulation mat3. There is enough space within the PET component for a patient tunnel4.

The shaded zones5of the insulation mat3represent a system of channels, which is supplied with fluid from the line6and where the line7removes the fluid again after it has flowed through the system of channels. These zones5including channels with coolant flowing through them serve as a heat shield against the temperature fluctuations on the surface of the generator coil.

Furthermore, at least one zone8is provided, whose volume can be varied. This is effected by means of pressurized-air channels9, which can be inflated via compressed air lines10. This zone or these zones8, which can be expanded using air pressure, result in transmission of force over an area between the two tubes1and2, even when the cooling is switched off. It is most advantageous for these zones to be arranged in the area of the side of or on the top of the annular gap, in order to exert a downward pressure to press the PET tube2against the generator coil1via incorporated rubber plates11, or similar, having a high coefficient of friction to prevent a displacement of the PET component2. Furthermore, the advantage of this arrangement is that in the case of the channels9not being filled with air and the cooling (which also contributes to the volumetric expansion of the insulation mat) being switched off, the height of the cushioning and of the insulation is considerably reduced and thus allowing the insulation mat to be inserted into the device. It may be necessary to lift the PET tube2above the concentric centre of the inventive device, in particular of the patient tunnel4, during the insertion of the insulation mat3, in order to be able to insert the rubber mats11. Once these have been moved into position, the PET tube2can be lowered.

The zones with the incorporated vibration-isolating materials11for vibration-damped positioning of the PET tube2in the GC1are preferably arranged in the lower area (around 270°). The weight of the PET tube2then prevents its displacement, even without additional pressure cushioning. Caoutchouc products or silicone rubbers are suitable materials for welding into the insulation mat. Since the coefficient of friction of the material of the mat should be low to ease insertion, and the coefficient of friction of the vibration-damping materials should be high to prevent a displacement of the components, the insulation mat can be segmented, so that the materials come into direct contact with the tube surfaces.

FIG. 2shows a longitudinal section through the embodiment fromFIG. 1. In this case, the same elements are referred to by the same reference symbols. Additionally, the figure shows that the insulation mat3does not have to fill the entire annular gap3ain the longitudinal direction, provided sufficient insulation and fixing of the PET tube2in the device are ensured. The inner perimeter la of the first modality1and the outer perimeter of the PET component2aare also shown.

FIG. 3shows a developed view of the insulation mat according to the described exemplary embodiment of the invention. The angular references correspond to those inFIG. 1, to ease association of the individual mat components.

At least one embodiment of the present invention allows the integration of various functions in a fixture assembly (insulation mat) which uses the annular gap required anyhow in the chosen configuration, without requiring additional expensive installation space within the components.

The device can be fitted and removed quickly and easily by activation of the pressure zones and inserting or removing the insulation mat. The production of the insulation mat can be implemented cost-effectively and is an easily replaceable component during servicing. However, the fixing effected is robust.