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  • 1
    Keywords: Germany ; LUNG ; CT ; imaging ; SYSTEM ; VOLUME ; NEW-YORK ; HEART ; RESOLUTION ; MICE ; NUCLEAR-MEDICINE ; QUALITY ; RAT ; animals ; RATS ; CONTRAST ; SIMULATION ; SIGNAL ; PRESSURE ; MOTION ; nuclear medicine ; DERIVATION ; radiology ; RE ; methods ; NUCLEAR ; IMAGE QUALITY ; flat-panel detector ; rodents ; USA ; SCANS ; animal ; respiratory gating ; MEDICINE ; comparison ; VALUES ; CONE-BEAM-CT ; intrinsic gating ; MICRO-COMPUTED-TOMOGRAPHY ; SCAN ; small-animal imaging
    Abstract: Gating in small-animal CT imaging can compensate artefacts caused by physiological motion during scanning. However, all published gating approaches for small animals rely on additional hardware to derive the gating signals. In contrast, in this study a novel method of intrinsic respiratory gating of rodents was developed and tested for mice (n=5), rats (n=5) and rabbits (n=2) in a flat-panel cone-beam CT system. In a consensus read image quality was compared with that of non-gated and retrospective extrinsically gated scans performed using a pneumatic cushion. In comparison to non-gated images, image quality improved significantly using intrinsic and extrinsic gating. Delineation of diaphragm and lung structure improved in all animals. Image quality of intrinsically gated CT was judged to be equivalent to extrinsically gated ones. Additionally 4D datasets were calculated using both gating methods. Values for expiratory, inspiratory and tidal lung volumes determined with the two gating methods were comparable and correlated well with values known from the literature. We could show that intrinsic respiratory gating in rodents makes additional gating hardware and preparatory efforts superfluous. This method improves image quality and allows derivation of functional data. Therefore it bears the potential to find wide applications in small-animal CT imaging
    Type of Publication: Journal article published
    PubMed ID: 18431578
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  • 2
    Keywords: GROWTH ; tumor ; PERFUSION ; CT ; HIGH-RESOLUTION CT ; imaging ; SPIRAL CT ; VOLUME ; NEW-YORK ; TISSUE ; computed tomography ; RESOLUTION ; NUCLEAR-MEDICINE ; TISSUES ; CONTRAST ; tomography ; STEM-CELLS ; COMPUTED-TOMOGRAPHY ; nuclear medicine ; radiology ; review ; NUCLEAR ; TECHNOLOGY ; USA ; BONE ; SCAFFOLDS ; radiography ; pediatric ; MEDICINE ; DETECTORS ; MDCT ; SCANNER ; HIGH-RESOLUTION MRI ; dynamic ; Flat-panel volume computed tomography ; FUNDAMENTAL PRINCIPLES ; High-resolution imaging ; Musculoskeletal applications ; SCAPHOID FRACTURE ; Trabecular imaging
    Abstract: Flat-panel volume computed tomography (fpVCT) is a recent development in imaging. We discuss some of the musculoskeletal applications of a high-resolution flat-panel CT scanner. FpVCT has four main advantages over conventional multidetector computed tomography (MDCT): high-resolution imaging; volumetric coverage; dynamic imaging; omni-scanning. The overall effective dose of fpVCT is comparable to that of MDCT scanning. Although current fpVCT technology has higher spatial resolution, its contrast resolution is slightly lower than that of MDCT (5-10HU vs. 1-3HU respectively). We discuss the efficacy and potential utility of fpVCT in various applications related to musculoskeletal radiology and review some novel applications for pediatric bones, soft tissues, tumor perfusion, and imaging of tissue-engineered bone growth. We further discuss high-resolution CT and omni-scanning (combines fluoroscopic and tomographic imaging)
    Type of Publication: Journal article published
    PubMed ID: 18443787
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  • 3
    Keywords: IN-VITRO ; AGENTS ; IN-VIVO ; PERFUSION ; THERAPY ; CT ; HEPATOCELLULAR-CARCINOMA ; liver ; TISSUE ; MRI ; CATHETER ; embolization ; X-RAY ; ARTERIOVENOUS-MALFORMATIONS ; MICROSPHERES ; ARTERY EMBOLIZATION ; ENDOVASCULAR EMBOLIZATION ; multimodal ; THERAPEUTIC EMBOLIZATION ; UTERINE FIBROID EMBOLIZATION
    Abstract: Objectives: Embolization therapy is gaining importance in the treatment of malignant lesions, and even more in benign lesions. Current embolization materials are not visible in imaging modalities. However, it is assumed that directly visible embolization material may provide several advantages over current embolization agents, ranging from particle shunt and reflux prevention to improved therapy control and follow-up assessment. X-ray-as well as magnetic resonance imaging (MRI)-visible embolization materials have been demonstrated in experiments. In this study, we present an embolization material with the property of being visible in more than one imaging modality, namely MRI and x-ray/computed tomography (CT). Characterization and testing of the substance in animal models was performed. Materials and Methods: To reduce the chance of adverse reactions and to facilitate clinical approval, materials have been applied that are similar to those that are approved and being used on a routine basis in diagnostic imaging. Therefore, x-ray-visible Iodine was combined with MRI-visible Iron (Fe3O4) in a macroparticle (diameter, 40-200 mu m). Its core, consisting of a copolymerized monomer MAOETIB (2-methacryloyloxyethyl [2,3,5-triiodobenzoate]), was coated with ultra-small paramagnetic iron oxide nanoparticles (150 nm). After in vitro testing, including signal to noise measurements in CT and MRI (n = 5), its ability to embolize tissue was tested in an established tumor embolization model in rabbits (n = 6). Digital subtraction angiography (DSA) (Integris, Philips), CT (Definition, Siemens Healthcare Section, Forchheim, Germany), and MRI (3 Tesla Magnetom Tim Trio MRI, Siemens Healthcare Section, Forchheim, Germany) were performed before, during, and after embolization. Imaging signal changes that could be attributed to embolization particles were assessed by visual inspection and rated on an ordinal scale by 3 radiologists, from 1 to 3. Histologic analysis of organs was performed. Results: Particles provided a sufficient image contrast on DSA, CT (signal to noise [SNR], 13 +/- 2.5), and MRI (SNR, 35 +/- 1) in in vitro scans. Successful embolization of renal tissue was confirmed by catheter angiography, revealing at least partial perfusion stop in all kidneys. Signal changes that were attributed to particles residing within the kidney were found in all cases in all the 3 imaging modalities. Localization distribution of particles corresponded well in all imaging modalities. Dynamic imaging during embolization provided real-time monitoring of the inflow of embolization particles within DSA, CT, and MRI. Histologic visualization of the residing particles as well as associated thrombosis in renal arteries could be performed. Visual assessment of the likelihood of embolization particle presence received full rating scores (153/153) after embolization. Conclusions: Multimodal-visible embolization particles have been developed, characterized, and tested in vivo in an animal model. Their implementation in clinical radiology may provide optimization of embolization procedures with regard to prevention of particle misplacement and direct intraprocedural visualization, at the same time improving follow-up examinations by utilizing the complementary characteristics of CT and MRI. Radiation dose savings can also be considered. All these advantages could contribute to future refinements and improvements in embolization therapy. Additionally, new approaches in embolization research may open up
    Type of Publication: Journal article published
    PubMed ID: 21263332
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  • 4
  • 5
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    Methods 50 (1), 42-49 
    Keywords: LUNG ; thorax ; VISUALIZATION ; TUMORS ; computed tomography ; HEART ; RESOLUTION ; CONTRAST AGENT ; CYCLE ; MOTION ; rodents ; prospective ; retrospective ; MICROCOMPUTED TOMOGRAPHY ; gating ; MICRO-COMPUTED-TOMOGRAPHY ; SCAN ; 4D ; Extrinsic ; Intrinsic ; Small-animal
    Abstract: Gating is necessary in cardio-thoracic small-animal imaging because of the physiological motions that are present during scanning. In small-animal computed tomography (CT), gating is mainly performed on a projection base because full scans take much longer than the motion cycle. This paper presents and discusses various gating concepts of small-animal CT, and provides examples of concrete implementation. Since a wide variety of small-animal CT scanner systems exist, scanner systems are discussed with respect to the most suitable gating methods. Furthermore, an overview is given of cardio-thoracic imaging and gating applications. The necessary contrast media are discussed as well as gating limitations. Gating in small-animal imaging requires the acquisition of a gating signal during scanning. This can be done extrinsically (additional hardware, e.g. electrocardiogram) or intrinsically from the projection data itself. The gating signal is used retrospectively during CT reconstruction, or prospectively to trigger parts of the Gating can be performed with respect to the phase or the amplitude of the gating signal, providing scan. different advantages and challenges. Gating methods should be optimized with respect to the diagnostic question, scanner system, animal model, type of narcosis and actual setup. The software-based intrinsic gating approaches increasingly employed give the researcher independence from difficult and expensive hardware changes. (C) 2009 Elsevier Inc. All rights reserved
    Type of Publication: Journal article published
    PubMed ID: 19651213
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  • 6
    Keywords: Germany ; ALGORITHM ; CT ; segmentation ; SYSTEM ; HEART ; MICE ; QUALITY ; RAT ; REGION ; MOTION ; ORGAN MOTION ; motion gating ; gating ; MICRO-COMPUTED-TOMOGRAPHY ; SCAN ; 4D ; Extrinsic ; Intrinsic ; Small-animal ; cardiac ; FREE-BREATHING RODENTS
    Abstract: A fully automated, intrinsic gating algorithm for small animal cone-beam CT is described and evaluated. A parameter representing the organ motion, derived from the raw projection images, is used for both cardiac and respiratory gating. The proposed algorithm makes it possible to reconstruct motion-corrected still images as well as to generate four-dimensional (4D) datasets representing the cardiac and pulmonary anatomy of free-breathing animals without the use of electrocardiogram ( ECG) or respiratory sensors. Variation analysis of projections from several rotations is used to place a region of interest (ROI) on the diaphragm. The ROI is cranially extended to include the heart. The centre of mass (COM) variation within this ROI, the filtered frequency response and the local maxima are used to derive a binary motion-gating parameter for phase-sensitive gated reconstruction. This algorithm was implemented on a flat-panel-based cone-beam CT scanner and evaluated using amoving phantom and animal scans ( seven rats and eight mice). Volumes were determined using a semiautomatic segmentation. In all cases robust gating signals could be obtained. The maximum volume error in phantom studies was less than 6%. By utilizing extrinsic gating via externally placed cardiac and respiratory sensors, the functional parameters ( e. g. cardiac ejection fraction) and image quality were equivalent to this current gold standard. This algorithm obviates the necessity of both gating hardware and user interaction. The simplicity of the proposed algorithm enables adoption in a wide range of small animal cone-beam CT scanners
    Type of Publication: Journal article published
    PubMed ID: 20299735
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  • 7
    Keywords: WORLD ; imaging ; molecular ; FRANCE ; molecular imaging
    Type of Publication: Meeting abstract published
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  • 8
    Keywords: tumor ; AGENTS ; Germany ; IN-VIVO ; LUNG ; PERFUSION ; CT ; FOLLOW-UP ; imaging ; INFORMATION ; SYSTEM ; SYSTEMS ; TISSUE ; TUMORS ; RESOLUTION ; TIME ; PATIENT ; animals ; TISSUES ; CONTRAST ; CONTRAST AGENT ; MORPHOLOGY ; COMPUTED-TOMOGRAPHY ; VESSELS ; computed tomography (CT) ; development ; flat-panel detector ; function ; animal ; retrospective ; BLOOD-POOL ; BONE ARCHITECTURE ; FLAT-PANEL DETECTORS ; GATED MICRO-CT ; micro-CT ; MICROCOMPUTED TOMOGRAPHY ; mini-CT ; motion gating ; OVARIECTOMIZED RATS ; small animal imaging ; VOLUME CT SCANNER ; X-RAY MICROTOMOGRAPHY
    Abstract: Micro Computed Tomography (micro-CT) was suggested in biomedical research to investigate tissues and small animals. Its use to characterize bone structures. vessels (e.g. tumor vascularization), tumors and soft tissues such as lung parenchyma has been shown. When co-registered, micro-CT can add structural information to other small animal imaging modalities. However, due to fundamental CT principles, high-resolution imaging with micro-CT demands for high x-ray doses and long scan times to generate a sufficiently high signal-to-noise ratio. Long scan times in turn make the use of extravascular contrast agents difficult. Recently introduced flat-panel based mini-CT systems offer a valuable trade-off between resolution (similar to 200 mu m), scan time (0.5 s), applied x-ray dose and scan field-of-view. This allows for angiography scans and follow-up examinations using iodinated contrast agents having a similar performance compared to patient scans. Furthermore, dynamic examinations such as perfusion studies as well as retrospective motion gating are currently implemented using flat-panel CT. This review summarizes applications of experimental CT in basic research and provides an overview of current hardware developments making CT a powerful toot to stud), tissue morphology and function in small laboratory animals such as rodents
    Type of Publication: Journal article published
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  • 9
    Keywords: analysis, animal, animals, ARCHITECTURE, BEAM COMPUTED-TOMOGRAPHY, BINARIES, blood pool, BLOOD-POOL,
    Abstract: Objectives: Implementation and evaluation of retrospective respiratory and cardiac gating of mice and rats using a flat-panel volume-CT prototype (fpVCT). Materials and Methods: Respiratory and cardiac gating was implemented by equipping a fpVCT with a small animal monitoring unit. ECG and breathing excursions were recorded and 2 binary gating signals derived. Mice and rats were scanned continuously over 80 seconds after administration of blood-pool contrast media. Projections were chosen to reconstruct volumes that fall within defined phases of the cardiac/respiratory cycle. Results: Multireader analysis indicated that in gated still images motion artifacts were strongly reduced and diaphragm, tracheobronchial tract, heart, and vessels sharply delineated. From 4D series, functional data such as respiratory tidal volume and cardiac ejection fraction were calculated and matched well with values known from literature. Discussion: Implementation of retrospective gating in tpVCT improves image quality and opens new perspectives for functional cardiac and lung imaging in small animals
    Type of Publication: Journal article published
    PubMed ID: 17984768
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  • 10
    Keywords: SURVIVAL ; BLOOD ; human ; PERFUSION ; CT ; imaging ; SYSTEM ; SYSTEMS ; VISUALIZATION ; VOLUME ; computed tomography ; RESOLUTION ; SURGERY ; NUCLEAR-MEDICINE ; radiation ; TIME ; COMPLEX ; COMPLEXES ; BLOOD-FLOW ; CONTRAST ; FLOW ; ACQUISITION ; DESIGN ; tomography ; COMPUTED-TOMOGRAPHY ; nuclear medicine ; ARCHITECTURE ; radiology ; GUIDANCE ; TEMPORAL BONE ; NUCLEAR ; TECHNOLOGY ; flat-panel detector ; multidetector CT ; USA ; BONE ; SPECIMENS ; animal ; PREDICT ; MEDICINE ; small animal imaging ; neuroradiology ; RATIO ; SCANNER ; small-animal imaging ; dynamic ; ARM ; CONE-BEAM CT ; DETECTOR COMPUTED-TOMOGRAPHY ; Flat-panel volume computed tomography ; FUNDAMENTAL PRINCIPLES ; PREOPERATIVE ANATOMY ; radiation dose
    Abstract: Flat-panel volume computed tomography (CT) systems have an innovative design that allows coverage of a large volume per rotation, fluoroscopic and dynamic imaging, and high spatial resolution that permits visualization of complex human anatomy such as fine temporal bone structures and trabecular bone architecture. In simple terms, flat-panel volume CT scanners can be thought of as conventional multidetector CT scanners in which the detector rows have been replaced by an area detector. The flat-panel detector has wide z-axis coverage that enables imaging of entire organs in one axial acquisition. Its fluoroscopic and angiographic capabilities are useful for intraoperative and vascular applications. Furthermore, the high-volume coverage and continuous rotation of the detector may enable depiction of dynamic processes such as coronary blood flow and whole-brain perfusion. Other applications in which flat-panel volume CT may play a role include small-animal imaging, nondestructive testing in animal survival surgeries, and tissue-engineering experiments. Such versatility has led some to predict that flat-panel volume CT will gain importance in interventional and intraoperative applications, especially in specialties such as cardiac imaging, interventional neuroradiology, orthopedics, and otolaryngology. However, the contrast resolution of flat-panel volume CT is slightly inferior to that of multidetector CT, a higher radiation dose is needed to achieve a comparable signal-to-noise ratio, and a slower scintillator results in a longer scanning time
    Type of Publication: Journal article published
    PubMed ID: 19001655
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