Field of the invention

The present invention relates to the field of preclinical imaging studies of small laboratory animals. More specifically it relates to methods and devices for preparing an animal for in-vivo imaging, e.g. for anatomical and/or functional imaging of the abdominal region.

Background of the invention

Molecular imaging, e.g. positron emission tomography (PET) or single photon emission computed tomography (SPECT), in small animal studies may be hampered by the large accumulation of tracer in the animal's bladder, thereby blinding other signals in the pelvic and/or the abdominal region. Bladder accumulation has been generally recognized as a problem in quantitative molecular imaging for the past 10 years. This makes it impossible to accurately quantify PET and SPECT studies in, for instance, inflammatory bowel disease. For example, it may be impossible to accurately evaluate an inflammation of the colon since the activity of the tracer in the bladder masks all other signals.

The impact of contrast accumulation in the bladder may be reduced by squeezing the bladder to induce excretion thereof. However, this is unpractical and unreliable due to the fast accumulation of tracer in the bladder in small animals, such as mice, rats or other preclinical animal models. Furthermore, squeezing the bladder during imaging may complicate accurate image reconstruction by inducing motion artifacts. Alternatively, the bladder may be emptied by means of suprapubic puncture. However, this may cause inflammation of the punctured tissues, which limits the applicability of this method in longitudinal imaging studies that use a contrast agent sensitive to inflammation, such as ¹⁸ F- fluorodeoxyglucose (FDG). Furthermore, inflammation, tissue damage and an increased risk of mortality may be undesirable in a controlled preclinical study regardless of the used imaging modality and contrast agent.

To overcome bladder accumulation, C. Haney et al., "Reduction of Image Artifacts in mice by bladder flushing with a novel double-lumen urethral catheter," in Molecular Imaging 5(3), pp. 175-179, describe bladder flushing with a double-lumen urethral catheter for electron paramagnetic resonance imaging (EPRI) studies. Although demonstrating the value of bladder flushing in molecular imaging of small animals, the disclosed procedure is non- optimal, and may result in 60% of animal mortality due to punctures in the bladder wall and the urethra. It should be noted that, although a long felt need for methods of compensating contrast accumulation in the bladder is recognized in the field of preclinical imaging, the method disclosed by Haney et al. has found little application due to the associated inhibitively high animal mortality. Hence, there is room for improvement. Summary of the invention

It is an object of embodiments of the present invention to provide efficient means and methods for preparing an animal for in-vivo imaging.

The above objective is accomplished by a method and device according to the present invention.

In a first aspect, the present invention provides a positioning device for preparing a female animal for preclinical in-vivo imaging using a contrast agent. This positioning device comprises a support element for supporting a dorsal trunk region of the female animal in a dorsal recumbent position. The support element is furthermore adapted in shape for posteriorly tilting the pelvis of the female animal.

A positioning device according to embodiments of the present invention may furthermore comprise at least one retaining element for retaining the lower extremities of the female animal in an abducted position.

In a positioning device according to embodiments of the present invention, the support element may comprise a surface for supporting the female animal in a dorsal recumbent position and a protrusion arranged on this surface for contacting the caudal dorsal trunk region of the female animal such that, when the female animal is supported by the surface in a dorsal recumbent position, the caudal dorsal trunk region of the animal is displaced in an anterior direction by this protrusion. This displacement in anterior direction causes the posterior tilting of the pelvis of the female animal.

In a positioning device according to embodiments of the present invention, the support element may comprise a specimen tray adapted for imaging the animal with a preclinical in-vivo imaging apparatus.

In a positioning device according to embodiments of the present invention, the support element may be adapted for cooperating with a specimen tray for imaging the animal with a preclinical in-vivo imaging apparatus.

A positioning device according to embodiments of the present invention may furthermore comprise at least one guiding element for guiding a double-lumen catheter for urethral insertion in said female animal. A positioning device according to embodiments of the present invention may furthermore comprise a reservoir for collecting an effluent from a double-lumen catheter, in which this double-lumen catheter is adapted for extracting the effluent from the urinary system of said female animal.

In a second aspect, the present invention provides a system for preparing a female animal for preclinical in-vivo imaging using a contrast agent. This system comprises a positioning device, which comprises a support element for supporting the caudal dorsal trunk region of the female animal in a dorsal recumbent position. This support element is adapted in shape for posteriorly tilting the pelvis of the female animal. The system furthermore comprises a double-lumen catheter for urethral insertion in said animal body and flushing of the bladder of said animal body with a flushing fluid.

In a system according to embodiments of the present invention the positioning device may comprise at least one retaining element for retaining the lower extremities of the animal body in an abducted position.

A system according to embodiments of the present invention may comprise a pump for pumping said flushing fluid through a first lumen of said double lumen catheter.

A system according to embodiments of the present invention may comprise a reservoir for collecting an effluent from a second lumen of the double-lumen catheter.

In a third aspect, the present invention provides a method for preparing a female animal for preclinical in-vivo imaging using a contrast agent. This method comprises the steps of positioning the female animal in a dorsal recumbent position, and tilting the pelvis of the female animal in a posterior tilt.

Furthermore, a method according to embodiments of the present invention may comprise the steps of inserting a double-lumen catheter into the urethra of the female animal, and introducing an imaging contrast agent into the body of the female animal.

The present invention also provides a method for preclinical in-vivo imaging of a female animal, in which this method comprises the steps of positioning the female animal in a dorsal recumbent position, tilting the pelvis of the female animal in a posterior tilt, inserting a double-lumen catheter into the urethra of the female animal, introducing an imaging contrast agent into the body of the female animal, imaging the female animal by applying a preclinical in-vivo imaging technique to obtain data representative of a spatial and/or spatiotemporal distribution of said imaging contrast agent in the animal body, and flushing the bladder of the female animal while imaging. This flushing comprises injecting a flushing fluid into the bladder through a first lumen of said double-lumen catheter and collecting an effluent from the bladder through a second lumen of said double-lumen catheter.

In further aspects, the present invention provides in the use of a positioning device according to the first aspect of the present invention for assisting in urethral catheterization of a female animal, and in the use of a positioning device according to the first aspect of the present invention for imaging a female animal while flushing the bladder of this female animal with a double-lumen catheter.

It is an advantage of embodiments of the present invention that a low risk of damaging the urinary tract of the animal may be obtained. It is a further advantage of embodiments of the present invention that thus low animal mortality may be achieved.

It is an advantage of embodiments of the present invention that continuous flushing of the bladder of an animal may be obtained during imaging.

It is an advantage of embodiments of the present invention that high reproducibility of imaging may be achieved.

It is an advantage of embodiments of the present invention that reproducible and accurate imaging of the pelvic and abdominal region of animals may be achieved.

Particular and preferred aspects of the invention are set out in the accompanying independent and dependent claims. Features from the dependent claims may be combined with features of the independent claims and with features of other dependent claims as appropriate and not merely as explicitly set out in the claims.

These and other aspects of the invention will be apparent from and elucidated with reference to the embodiment(s) described hereinafter.

Brief description of the drawings

FIG. 1 shows a schematic illustration of a first embodiment of a positioning device according to a first aspect of the present invention.

FIG. 2 shows a horizontal projection (top view) of a second embodiment of a positioning device according to the first aspect of the present invention.

FIG. 3 shows a vertical projection (side view) of the positioning device illustrated in

FIG. 2.

FIG. 4 shows a perspective view of the positioning device illustrated in FIG. 2 and

FIG. 3. FIG. 5 shows a detail view of guiding elements for guiding a catheter according to embodiments of the first aspect of the present invention.

FIG. 6 shows a double-lumen catheter for use with devices and systems according to embodiments of the present invention.

FIG. 7 shows a cross-section of a double-lumen catheter for use with devices and systems according to embodiments of the present invention.

FIG. 8 shows an overview of a system for preparing a female animal for preclinical in- vivo imaging according to an embodiment of a second aspect of the present invention.

FIG. 9 illustrates an exemplary method for preparing a female animal for preclinical in-vivo imaging according to an embodiment of a third aspect of the present invention.

FIG. 10 illustrates an exemplary method for pre-clinical in-vivo imaging of a female animal according to an embodiment of a fourth aspect of the present invention.

FIG. 11 shows an example of an application of embodiments of the present invention, in which arrows indicate the colon of a mouse with distal colon inflammation.

FIG. 12 shows an example of an application of embodiments of the present invention.

FIG. 13 shows, in an example of an application of embodiments of the present invention, contrast agent accumulation in the bladder when no bladder flushing is applied.

FIG. 14 shows, in an example of an application of embodiments of the present invention, lack of contrast agent accumulation in the bladder when continuous bladder flushing is applied in accordance with embodiments of the present invention.

FIG. 15 shows a 3D reconstruction of a bowel inflammatory disease imaging study according to embodiments of the present invention.

FIG. 16 shows a photograph of positioning a mouse according to embodiments of the present invention.

FIG. 17 shows a photograph of a mouse positioned and having an urethral catheter introduced according to embodiments of the present invention.

FIG. 18 shows a photograph of a mouse prepared for imaging according to embodiments of the present invention.

FIG. 19 shows a photograph and schematic overview of a double-lumen catheter setup according to embodiments of the present invention.

FIG. 20 shows exemplary results of a longitudinal bowel inflammation study carried out according to embodiments of the present invention. FIG. 21 shows exemplary results of a bowel inflammation versus control study carried out according to embodiments of the present invention.

FIG. 22 shows exemplary quantitative results obtained in a longitudinal study carried out according to embodiments of the present invention.

FIG. 23 shows an exemplary ex-vivo validation of a study carried out according to embodiments of the present invention.

The drawings are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes.

Any reference signs in the claims shall not be construed as limiting the scope.

In the different drawings, the same reference signs refer to the same or analogous elements.

Detailed description of illustrative embodiments

The present invention will be described with respect to particular embodiments and with reference to certain drawings but the invention is not limited thereto but only by the claims. The drawings described are only schematic and are non-limiting. In the drawings, the size of some of the elements may be exaggerated and not drawn on scale for illustrative purposes. The dimensions and the relative dimensions do not correspond to actual reductions to practice of the invention.

The terms first, second and the like in the description and in the claims, are used for distinguishing between similar elements and not necessarily for describing a sequence, either temporally, spatially, in ranking or in any other manner. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other sequences than described or illustrated herein.

Moreover, the terms top, under and the like in the description and the claims are used for descriptive purposes and not necessarily for describing relative positions. It is to be understood that the terms so used are interchangeable under appropriate circumstances and that the embodiments of the invention described herein are capable of operation in other orientations than described or illustrated herein.

It is to be noticed that the term "comprising", used in the claims, should not be interpreted as being restricted to the means listed thereafter; it does not exclude other elements or steps. It is thus to be interpreted as specifying the presence of the stated features, integers, steps or components as referred to, but does not preclude the presence or addition of one or more other features, integers, steps or components, or groups thereof. Thus, the scope of the expression "a device comprising means A and B" should not be limited to devices consisting only of components A and B. It means that with respect to the present invention, the only relevant components of the device are A and B.

Reference throughout this specification to "one embodiment" or "an embodiment" means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrases "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment, but may. Furthermore, the particular features, structures or characteristics may be combined in any suitable manner, as would be apparent to one of ordinary skill in the art from this disclosure, in one or more embodiments.

Similarly it should be appreciated that in the description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together in a single embodiment, figure, or description thereof for the purpose of streamlining the disclosure and aiding in the understanding of one or more of the various inventive aspects. This method of disclosure, however, is not to be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as the following claims reflect, inventive aspects lie in less than all features of a single foregoing disclosed embodiment. Thus, the claims following the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of this invention.

Furthermore, while some embodiments described herein include some but not other features included in other embodiments, combinations of features of different embodiments are meant to be within the scope of the invention, and form different embodiments, as would be understood by those in the art. For example, in the following claims, any of the claimed embodiments can be used in any combination.

In the description provided herein, numerous specific details are set forth. However, it is understood that embodiments of the invention may be practiced without these specific details. In other instances, well-known methods, structures and techniques have not been shown in detail in order not to obscure an understanding of this description. Where the description refers to "anterior," or "ventral," reference is made to toward the front of the body, while reference in the description to "posterior" or "dorsal," refers to a direction toward the back of the body. For example, the spine is on the posterior or dorsal, i.e. the back, side of the body, while the sternum is on the anterior or ventral, i.e. the front, side of the body.

Where the description refers to "inferior" or "caudal," reference is made to toward the lower part of the body, i.e. towards the feet, while where the description refers to "superior," "rostral" or "cranial," reference is made to toward the top of the body, i.e. toward the head. For example, the pelvis is located on the inferior or caudal, i.e. the bottom, side of the trunk, while the neck and head are on the superior or cranial, i.e. the top, side of the body.

Where the description refers to "the longitudinal axis of the body," reference is made to the central line stretching from points on the opposite ends of the body, i.e. from the superior aspect to the inferior aspect.

Where the description refers to "proximal," reference is made to toward the trunk of the body, while where the description refers to "distal," reference is made to away from the trunk, i.e. the torso. Where the description refers to "medial," reference is made to toward the midline of the body, i.e. the longitudinal axis, while where the description refers to "lateral", reference is made to away from that longitudinal axis, e.g. away from the median plane. The median plane is a midsagittal plane which bisects the body vertically, dividing the body exactly in a left and a right side.

Where the description refers to "abducted position", reference is made to a position away from the midline of the body, i.e. the longitudinal axis.

Where the description refers to a "dorsal recumbent position," reference is made to the body lying in a supine position, e.g. stretched out on the back. Where the description refers to "posteriorly tilting the pelvis," reference is made to positioning the caudal aspect of the pelvic girdle in an anterior direction with respect to the rostral aspect of the pelvic girdle.

Where the description refers to "preclinical imaging," reference is made to a technique for acquiring spatial information, e.g. 2D images or volumetric image data, pertaining to internal anatomy, internal structure and/or internal biochemical, cellular or tissue function of animals. Such preclinical imaging may comprise a medical imaging technique applied to laboratory animals, e.g. for preclinical studies in a model organism. Preclinical imaging may comprise an anatomical or functional imaging method such as known in the art as a conventional medical or veterinary imaging technique, an imaging technique specifically adapted for small animal imaging, or an experimental animal research imaging technique. For example, imaging may be performed on the animal using: nuclear imaging, e.g. positron emission tomography (PET) or single photon emission computed tomography (SPECT); X-ray imaging, e.g. planar X-ray radiography or X-ray computed tomography (CT); optical imaging, e.g. bioluminescence or fluorescence imaging; acoustic imaging, e.g. high- frequency ultrasound imaging (US) or photoacoustic tomography (PAT); or magnetic resonance imaging, e.g. magnetic resonance imaging (MRI) or electron paramagnetic resonance imaging (EPR).

Where the description refers to "contrast agents," reference is made to any medium that is suitable for administering to an animal, e.g. by injection into the blood circulation, ingestion or inhalation, in order to produce an enhanced or purposefully adapted contrast in images which are acquired by means of a preclinical imaging technique. This includes, but is not limited to, for example, radio-opaque contrast agents for use in X-ray imaging, e.g. iodine contrast agents, magnetic contrast agents, e.g. gadolinium contrast agents, and radiotracers, e.g. functionalized radioisotopic agents, for example ¹⁸ F-fluorodeoxyglucose (FDG).

Embodiments of the present invention may assist in flushing accumulated contrast agents, e.g. tracers, from the bladder of a female animal, e.g. a mouse, rat,.... By putting the animal in a gynaecological position, e.g. a lithotomy position, a device, system or method according to embodiments of the present invention may reduce damage to the urinary tract. Moreover, an urethral catheter used for this flushing may be further optimized to limit the risk of puncturing the bladder wall and/or the urethra of the animal. Such devices may be used in positron emission tomography (PET) and single photon emission computed tomography (SPECT) imaging, but also in magnetic resonance imaging (MRI) and computed tomography (CT) acquisitions or any other small animal imaging technique where a radiotracer or a contrast agent are used.

In a first aspect, the present invention relates to a positioning device 20 for preparing a female animal 10, such as for example a rodent, for preclinical in-vivo imaging using a contrast agent. Such positioning device 20 comprises a support element 22 for supporting a dorsal trunk region 23, e.g. a caudal dorsal trunk region, of the female animal in a dorsal recumbent position. The support element 22 is adapted in shape for posteriorly tilting the pelvis of this female animal. The positioning device 20 may further comprise a retaining element 24 for retaining the lower extremities of the female animal in an abducted position. FIG. 1 shows a schematic illustration of a first embodiment of such positioning device 20 according to the first aspect of the invention. The positioning device 20 may be colloquially referred to as a gynaecological positioning frame. The positioning device 20 is suitable for preparing a female animal for imaging. Particularly, the female animal may be a laboratory animal, e.g. a preclinical animal model, for example a rodent, such as a mouse or a rat. The positioning device may assist in preparing the animal for a preclinical in-vivo imaging method. Contrast enhancement may be obtained in such imaging by introduction, e.g. injection into the cardiovascular circulatory system of the animal, of a contrast agent suitable for the particular imaging modality, for example ¹⁸ F-fluorodeoxyglucose (FDG), iodine, gadolinium or fluorescent contrast agents. Such contrast agents may serve the purpose of merely providing a contrast-enhanced anatomical image, e.g. to provide visualisation of tissues which are otherwise transparent with respect to the imaging technique and/or which are generally poorly discernible from adjacent structures by this imaging technique. Such contrast agents may also provide a more complex visualisation of specifically selected features of interest, e.g. by using radiotracers selected for a specific cellular or biochemical target. Therefore, where the present description refers to contrast agents, it should be noted that this may refer to media for administration to animals for the purpose of improved imaging, either by passive enhancement, e.g. by using a iodine or barium contrast agent for improved X-ray absorption, or by active enhancement, e.g. providing imaging of a specific molecular or biological target, for example a tracer, e.g. a radioactive label for localizing a specific target compound and/or for tracing the path of a target compound through a series of chemical reactions.

These contrast agents may have in common that they are typically cleared from the circulatory system by the kidneys and thus may accumulate in the bladder. This may be particularly disadvantageous for imaging small homeothermic animals, since the higher metabolic rate, e.g. as required for homeostasis at a larger surface area to volume ratio, causes fast accumulation of contrast agent in the bladder, e.g. on a time scale much smaller than or comparable to the time required for imaging. This accumulation may saturate images and obscure anatomical or functional features of interest, particularly for such features in the pelvic and abdominal region.

The positioning device 20 comprises a support element 22 for supporting a dorsal trunk region 23, e.g. a caudal dorsal trunk region, of the female animal. This support element 22 is adapted in shape for posteriorly tilting the pelvis of the female animal. For example, positioning the dorsal trunk region 23, e.g. the lower back of the animal, on the support element 22 while the animal is oriented in a dorsal recumbent position, e.g. lying in a supine position on the support element 22, may displace the caudal aspect of the sacrum, ischium and pubis in an anterior direction with respect to the rostral aspect of the sacrum and the iliac crest.

The support element 22 may comprise, as shown in the first embodiment illustrated in FIG. 1, a surface 25 for supporting the female animal in a dorsal recumbent position. Such surface 25 may be an elongate flat couch, or may be shaped for improved accommodation of the back of the trunk of the animal, e.g. forming an elongate surface with a concave curvature in the lateral direction, for example shaped as a part of a cylindrical hull, e.g. as shown in FIG. 4 for a second embodiment. Furthermore, the positioning device 20 may comprise at least one additional positioning element 27 for constraining the female animal on the support element 22 in a dorsal recumbent position, e.g. a strap for securing the animal to the support element 22.

The support element 22 may comprise a specimen tray 30 adapted for imaging the female animal with a preclinical in-vivo imaging apparatus, e.g. a tray adapted for insertion into an in-vivo imaging apparatus. For example, in specific embodiments of the present invention, this support element 22 may be adapted for use as a specimen tray 30 for insertion in an imaging scanner, e.g. a micro-CT, micro-PET or micro-SPECT scanning apparatus. In other embodiments, the support element 22 may be adapted for cooperating with a specific tray design, e.g. a specimen tray, cradle or imaging couch, for imaging the animal with a preclinical in-vivo imaging apparatus, e.g. adapted for mounting onto or fitting into a tray for an imaging scanner. For example, the positioning device 20 may be adapted for cooperating with a tray for imaging the animal in a preclinical or medical in-vivo imaging scanner.

This support element 22 may comprise a protrusion 26 arranged on this surface 25 for contacting, e.g. supporting, the caudal dorsal trunk region 23 of the animal body such that, when the animal body is supported by the surface 25 in a dorsal recumbent position, the caudal dorsal trunk region of the animal is displaced in an anterior direction by said protrusion 26. For example, this protrusion 26 may be convex shaped in a longitudinal direction, the longitudinal direction corresponding to the longitudinal anatomical axis of the animal when positioned on the surface 25. While in embodiments of the present invention the protrusion 26 may comprise a separate component, e.g. a cushion, such as a closed-cell foam pad, attached to or placed on the supporting surface 25, in other embodiments the protrusion 26 may be formed as an elevated section of the surface 25. The protrusion 26 may extend in transversal direction, the transversal direction corresponding to a direction transversal to the longitudinal anatomical axis of the animal when positioned on the surface 25, over the full width of the supporting surface 25, or only over a part of the width thereof.

The positioning device 20 may further comprise at least one retaining element 24, e.g. a pair of retaining elements, for retaining the lower extremities of the female animal in an abducted position. This retaining element 24 may comprise straps, clamps or tensioning elements. For example a pair of clamps or straps may hold the legs of the animal in a spread- out position. In particular embodiments, the retaining element 24 may comprise the protrusion 26 shaped such as to extend between the lower extremities of the animal from a dorsal to ventral direction in order to contact and separate these lower extremities. The retaining element 24 may be arranged on the surface 25 and may extend between the lower extremities of the animal from a dorsal to ventral direction in order to contact and separate these lower extremities. Thus, the positioning device 20 may be adapted for positioning and constraining the female animal in a position which is similar to a conventional gynaecological or lithotomy position.

In FIG. 2 to FIG. 4, a second exemplary embodiment of a positioning device 20 according to this first aspect of the invention is shown. This embodiment may comprise a support element 22 that is mountable to a specimen tray 30. The positioning device 20 may also comprise means for adjusting the position of the support element 22, e.g. for adapting the positioning device to the physical dimensions of the female animal, for example by means of a screw 31 and a slot 32 for adjusting the position of the support element 22, for example by selection of an appropriate position for securing the screw 31 in the corresponding slot 32.

The specimen tray 30 may be adapted for a specific imaging modality, e.g. may be shaped to cooperate with a specific type and/or model of imaging scanner. Furthermore, the support element 22 may be removably mountable to any of a plurality of such specimen trays 30, e.g. each specimen tray 30 being adapted for a corresponding imaging modality, e.g. shaped to cooperate with a specific type and/or model of imaging scanner.

Embodiments of positioning devices according to the first aspect of the present invention may comprise at least one additional positioning element 27 for constraining the female animal on the support element 22 in a dorsal recumbent position. For example, such additional positioning element may comprise a head constraint 33, e.g. an element shaped for receiving and constraining the head of the female animal, and/or flanges arranged on the support element 22 for laterally constraining and/or supporting the female animal along the dorsal trunk region 23. Furthermore, the positioning device 20 may comprise reference elements for providing reference indicators in images obtained by imaging the animal while positioned in the device 20, for example, drilled holes 34 to receive fiducial markers, e.g. for aiding in fusion of images obtained by different imaging modalities, e.g. CT and PET.

The positioning device 20 may comprise at least one guiding element 29 for guiding and/or supporting a double-lumen catheter 42 for urethral insertion in said female animal. Such a double-lumen catheter 42 for urethral insertion may typically comprise a first lumen 43, e.g. a small-diameter tube, for example a polyethylene tube such as PE-10 tubing, arranged inside a second lumen 44, for example a standard intravenous catheter. The at least one guiding element 29 may for example comprise vertically arranged elements, e.g. plates, having an indent or perforation for supporting and guiding a double-lumen catheter 42 in a substantially parallel orientation relative to the longitudinal anatomical axis of the animal when positioned on the surface 25. In FIG. 5, a detail view of an exemplary arrangement for guiding a double-lumen catheter 42 by means of such guiding elements 29 is shown. The double-lumen catheter 42 may furthermore be advantageously shaped to provide better access, e.g. to the tail or rectum, for additional drug or contrast agent administration. For example, the catheter 42 may be provided with a pair of perpendicular corners, such as two 90° corners as shown in FIG. 5 and FIG. 6, in order to laterally displace the catheter over a short distance. This may provide better access for, for instance, administering a rectal contrast agent. In embodiments according to the first aspect of the present invention, the positioning device 20 may comprise a reservoir 35 for collecting an effluent from a double- lumen catheter 42, in which this double-lumen catheter 42 is adapted for extracting said effluent from the urinary system of said female animal. For example, one lumen of the double-lumen catheter 42, e.g. the second lumen 44, may be arranged to expel fluids therefrom into the reservoir 35. This reservoir 35 may be arranged on the support element 22, e.g. in a caudal direction relative to the dorsal trunk region of the female animal when positioned on the support element 22, e.g. as shown in FIG. 2 to 5. The reservoir 35 may be removable to allow easy disposal of effluent and cleaning of the reservoir. Furthermore, the reservoir may be disposable, e.g. provided in the form of a consumable product. The at least one retaining element 24 may comprise a pair of laterally positioned elements, e.g. hooks, such as the cranially oriented hooks shown in FIG. 2 to FIG. 4, for engaging the lower extremities of the female animal, for example for medially contacting and retaining the upper legs, in order to retain these lower extremities in an abducted position. However, this at least one retaining element 24 may comprise, as will be evident to the person skilled in the art, additional or alternative means for retaining the lower extremities of the female animal, e.g. a clamps, a clip, a strap or a resilient tensioning element.

Furthermore, the positioning device 20 may comprise additional elements for administering a contrast agent to the female animal, e.g. an intravenous injection system for injecting a contrast agent, e.g. FDG, into the blood circulation of the animal. The positioning device 20 may also comprise means for anesthetizing the animal, e.g. through injection or inhalation of an anesthetising agent, such as by inhalation of isoflurane, and/or means for monitoring vital functions, e.g. blood pressure, heart rate, respiration or function of the nervous system. The positioning device 20 may comprise additional elements for administering other drugs or further contrast agents, for example tubing for rectally administering a contrast agent, such as diatrizoic acid, e.g. gastrografin, to the colon.

In a second aspect, the present invention relates to a system 40 for preparing a female animal for preclinical in-vivo imaging using a contrast agent. This system 40 comprises a positioning device 20 which comprises a support element 22 for supporting the caudal dorsal trunk region of the female animal in a dorsal recumbent position. This support element 22 is adapted in shape for posteriorly tilting the pelvis of the female animal. The positioning device 20 may further comprise at least one retaining element 24 for retaining the lower extremities of the animal body in an abducted position. Particularly, the positioning device 20 may be an embodiment of a positioning device according to the first aspect of the present invention.

The system 40 furthermore comprises a double-lumen catheter 42 for urethral insertion in the animal body and flushing of the bladder of the animal body with a flushing fluid, e.g. pure water or a saline solution. For example, the double-lumen catheter 42 may comprise a first lumen 43, and a second lumen 44, for example both coaxially arranged. The first lumen 43 may be a polyethylene tube, e.g. a PE-10 tubing, e.g. having a 0.28 mm inside diameter (i.d.) and 0.61 mm outside diameter, while the second lumen 44 may be a tube of larger diameter, e.g. a silicone tube, for example a standard 20 G IV catheter, e.g. 1.1 mm i.d.. The first lumen 43 may be stretched before insertion, causing it to curl within the bladder and reducing the risk of impingement of the catheter against the bladder wall. Furthermore, the catheter 42 may be lubricated, e.g. by applying a lubricant or gel to the catheter, in order to reduce friction and reduce the risk of tissue damage. An exemplary double-lumen catheter 42 is shown in FIG. 6 and FIG. 7. The head 41 of the catheter may comprise the first lumen 43 extending further than the second lumen 44, such that, for example, the first lumen 43 may extend further into the bladder in order to inject a flushing fluid, while the second lumen 44 may end in the bladder or even in the urethra, e.g. tightly fitting into the urethra without extending into the bladder. The first lumen 43 may also extend further than the second lumen 44 on the distal end, i.e. at the tail of the catheter, e.g. in order to allow the bladder effluent to drip from the distal end into a reservoir 35. Furthermore, for insertion, a wider catheter may be used for guiding the double-lumen catheter into the distal end of the urethra, for example a 24 G IV catheter.

The system 40 may comprise a pump 45, e.g. a perfusion pump, for pumping the flushing fluid through the first lumen 43 of the double lumen catheter 42. The system 40 may comprise a manually operated or automated plunger for injecting fluid into this first lumen 43, e.g. a syringe. For example, the pump 45 may be an automated syringe pump.

The system 40 may comprise a reservoir for collecting an effluent from a second lumen 44 of the double-lumen catheter 42. In embodiments of the present invention, this reservoir 35 may be integrated in the positioning device 20, e.g. as discussed in relation to embodiments of the first aspect of the present invention. Alternatively, not illustrated in the drawings, this reservoir may be a part of the system 40 separate from the positioning device 20. The reservoir 35 may be a disposable reservoir 35 adapted for cooperating with the positioning device 20, for example, the positioning device 20 may comprise a reservoir holder for receiving such a disposable reservoir. The reservoir may comprise a disposable bag for connecting to the double-lumen catheter 42. In other embodiments according to the second aspect of the present invention, the reservoir may be integrated in the perfusion pump 45.

Furthermore, the system 40 may comprise additional elements for administering a contrast agent to the female animal, e.g. an intravenous injection system for injecting a contrast agent, e.g. FDG, into the blood circulation of the animal. The system 40 may comprise means for anesthetizing the animal, e.g. through injection or inhalation of an anesthetising agent, and/or means for monitoring vital functions, e.g. blood pressure, heart rate, respiration or function of the nervous system. Such means for anesthetizing, monitoring and/or administering contrast agent may be fully or partially integrated in the positioning device 20. FIG. 8 shows an exemplary embodiment of a system 40 according to this second aspect of the present invention, comprising a positioning device 20, a pump 45, and a double- lumen catheter 42.

In a third aspect, the present invention relates to a method 1 for preparing a female animal, for example a rodent, for preclinical in-vivo imaging using a contrast agent. Such method comprises the steps of positioning 3 the female animal in a dorsal recumbent position and tilting 5 the pelvis of the female animal in a posterior tilt. Furthermore, such method may comprise the steps of inserting 7 a double-lumen catheter into the urethra of the female animal, and introducing 9 an imaging contrast agent into the body of the female animal, e.g. through injection, for example by injecting into the tail vein of the female animal. For example, the method 1 may be a method for preparing a female animal for imaging assisted by a device or system according to the first and second aspects of the present invention. Particularly, this imaging may comprise imaging of the pelvic and/or abdominal region of the animal, for example for imaging studies of diseases inflicting the bowels, e.g. inflammatory bowel disease, or of primary and/or metastatic cancers, e.g. in the intestinal tract; the invention, however, not being limited to these applications.

An exemplary method 1 for preparing a female animal body for imaging using a contrast agent according to the first aspect of the invention is schematically illustrated in FIG. 9. The animal may typically be small laboratory animal, e.g. a rodent such as a mouse. Imaging may be performed on such animal using any conventional medical or veterinary imaging technique, such as positron emission tomography (PET), single photon emission tomography (SPECT), X-ray imaging, X-ray computed tomography (CT), optical computed tomography (OCT), ultrasound imaging (US) or magnetic resonance imaging (MRI). Contrast enhancement may be obtained in such imaging by injection, e.g. introduction in the cardiovascular circulatory system of the animal body, of a contrast agent suitable for the particular imaging modality, for example Fluor-18 desoxyglucose (FDG), iodine, gadolinium or fluorescent contrast agents.

The method 1 comprises positioning 3 the animal body in a dorsal recumbent position, e.g. a supine position, for example by placing the animal on its back on a support structure. This positioning may comprise constraining the animal in the recumbent position, for example by closing a releasable strap around the trunk of the animal in order to secure the animal to a support structure. This positioning 3 may be assisted by a positioning device 20 according to embodiments of the first aspect of the present invention, for example in a system 40 according to embodiments of the second aspect of the present invention.

The method 1 further comprises tilting 5 the pelvis of the animal body in a posterior tilt. For example, the animal may be positioned in a dorsal recumbent position on a support structure which is adapted in shape to elevate the lower torso of the animal relative to the upper torso of the animal, e.g. such that the lower spine and pelvis are displaced in an anterior direction and the pelvis is thereby posterior tilted. This positioning will cause the urethra of the animal to straighten in order to prepare the animal for urethral catheterization.

In a further aspect, the present invention relates to a method 2 for preclinical in-vivo imaging of a female animal. Such method 2, for example the exemplary method 2 shown in FIG. 10, comprises the steps of positioning 3 the female animal in a dorsal recumbent position, tilting 5 the pelvis of the female animal in a posterior tilt, inserting 7 a double-lumen catheter into the urethra of the female animal and introducing 9 an imaging contrast agent into the body of the female animal.

The method 2 furthermore comprises imaging 11 the female animal by applying a preclinical in-vivo imaging technique to obtain data representative of a spatial and/or spatiotemporal distribution of said imaging contrast agent in the animal body, and flushing 13 the bladder of said female animal while imaging 11, in which said flushing 13 comprises injecting a flushing fluid into the bladder through a first lumen 43 of a double-lumen catheter 42 and collecting an effluent from the bladder through a second lumen 44 of the double- lumen catheter 42.

In yet a further aspect, the present invention relates to the use of a positioning device according to embodiments of the first aspect of the present invention for assisting in urethral catheterization of a female animal. In another further aspect, the present invention relates to the use of a positioning device according embodiments of the first aspect of the present invention for imaging a female animal while flushing the bladder of said female animal with a double-lumen catheter.

As an example, an application of methods and devices according to embodiments of the present invention is described hereinbelow and in the accompanying figures. Accurate quantification of PET or SPECT studies in bowel inflammatory disease as illustrated in FIG. 11 to FIG. 15 was carried out using a device, system and method according to embodiments of the present invention. These images were obtained from the colonic region of a small animal. FIG. 11 shows an example of an application of embodiments of the present invention, in which arrows indicate the colon of a mouse with distal colon inflammation. FIG. 12 shows an example of an application of embodiments of the present invention. FIG. 13 shows the accumulation of FDG in the bladder when, contrary to embodiments of the present invention, no bladder flushing is performed. For comparison, FIG. 14 shows the image obtained while continuously flushing the bladder as described in description provided hereinabove.

FIG. 14 and FIG. 15 illustrate the ability to image the colonic region of the small animal for evaluation without substantive quality degradation due to contrast accumulation in the bladder. The chronology of this setup is illustrated by FIG. 16 to FIG. 18, i.e. positioning of the animal and injection of contrast agent in FIG. 16; insertion of a urethral catheter 42 with reservoir 35 for collection of effluent from the urinary tract of the animal in FIG. 17; and pumping of flushing fluid into the bladder through a first lumen 43 of the urethral catheter 42 by means of an infusion pump 45 while collecting effluent through the second lumen 44 of the urethral catheter 42 in the reservoir in FIG. 18. FIG. 19 shows the tubing structure. The first lumen 43, e.g. a PE10 tube, is connected to the infusion pump 45 and flushes the bladder at a predetermined rate, e.g. 10 ml/hour. This PE10 tubing is inserted in a modified catheter, i.e. forming the second lumen 44, having a larger diameter than the PE10 tubing, which is also inserted in the bladder. Through the use of this double lumen setup the urine/water mix may thus be drained. The effluents then reach a further tubing, e.g. silicon tubing 47, which is merely used to transport the flux to the collection syringe 35 which is tilted to prevent contamination of the surface 25 by the extracted fluids.

In particular experiments, acute distal colon damage was induced by administering dextran sodium sulphate (DSS) through the drinking-water of four CD-I mice. These animals were scanned with μΡΕΤ/CT at day 0, 3, 5, 7, 11 and 14 with 0.5mCi FDG. During each scan the animals' bladders were continuously flushed using the urethral catheter and the gynaecological frame according to embodiments of the present invention. The comparison with the histological inflammation score shows that the evolution over time (day 0-14) is well reproduced by μΡΕΤ/CT, as shown in FIG. 20, and the evaluation versus the immunohistochemical MPO analysis at the final timepoint (not shown) confirmed an accurate relative quantification.

For any quantitatively accurate PET exam in the pelvic region continuous flushing of the bladder in small animals may be required. Using a device according to embodiments of the present invention, testing of the efficacy of a drug that treats for colitis (cfr. also Chron's disease) has been achieved. Mice were treated with DMOG (Dimethyloxallyl Glycine, curative drug) or placebo (consisting of vehicle alone) during DSS administration. DMOG is known to protect against colitis. A baseline scan was performed at day 0, with a follow-up scan at day 7. In strong contrast to placebo-treated mice, DMOG-treated mice did not show an increased distal colonic PET-signal at day 7 of DSS-treatment compared to the baseline scan. FIG. 21 shows representative images for both the histology and for the PET data. Hence it may be concluded that for quantitatively accurate molecular imaging exams in the pelvic or abdominal region continuous flushing of the bladder in small animals may be mandatory. This may only be feasible with a low mortality if the urethral catheter is optimized for molecular imaging and is combined with a gynaecological positioning frame according to embodiments of the present invention. It should be noted that using μΡΕΤ/μΟΤ for studies such as described in the example hereinabove may have been previously impossible.

In FIG. 22, a time course of the inflammatory-induced colonic FDG signal after DSS administration is shown as measured by the ratio between the colon and the brain as reference region in a longitudinal experiment. As a further example, FIG. 23 shows an ex-vivo validation of the micro-PET quantification at day 14, whereupon the animals were sacrificed. In this example, measured myeloperoxidase (MPO) activity in the distal colon and the histological inflammation score at end-of-life were used as gold standards.