Thomas Rodt

Publications of Thomas Rodt

• Lung tumour growth kinetics in SPC-c-Raf-1-BB transgenic mice assessed by longitudinal in-vivo micro-CT quantification.

  Authors: Thomas Rodt, Christian von Falck, Sabine Dettmer, Katja Hueper, Roman Halter, Ludwig Hoy, Matthias Luepke, Juergen Borlak, Frank Wacker

  Journal of experimental & clinical cancer research : CR. 02/2012; 31(1):15.

  ABSTRACT: SPC-c-Raf-1-BxB transgenic mice develop genetically induced disseminated lung adenocarcinoma allowing examination of carcinogenesis and evaluation of novel treatment strategies. We reportABSTRACT: SPC-c-Raf-1-BxB transgenic mice develop genetically induced disseminated lung adenocarcinoma allowing examination of carcinogenesis and evaluation of novel treatment strategies. We report on assessment of lung tumour growth kinetics using a semiautomated region growing segmentation algorithm. 156 non contrast-enhanced respiratory gated micro-CT of the lungs were obtained in 12 SPC-raf transgenic (n = 9) and normal (n = 3) mice at different time points. Region-growing segmentation of the aerated lung areas was obtained as an inverse surrogate for tumour burden. Time course of segmentation volumes was assessed to demonstrate the potential of the method for follow-up studies. Micro-CT allowed assessment of tumour growth kinetics and semiautomated region growing enabled quantitative analysis. Significant changes of the segmented lung volumes over time could be shown (p = 0.009). Significant group differences could be detected between transgenic and normal animals for time points 8 to 13 months (p = 0.043), when marked tumour progression occurred. The presented region-growing segmentation algorithm allows in-vivo quantification of multifocal lung adenocarcinoma in SPC-raf transgenic mice. This enables the assessment of tumour load and progress for the study of carcinogenesis and the evaluation of novel treatment strategies.

• PET/CT imaging of c-Myc transgenic mice identifies the genotoxic N-nitroso-diethylamine as carcinogen in a short-term cancer bioassay.

  Authors: Katja Hueper, Mahmoud Elalfy, Florian Laenger, Roman Halter, Thomas Rodt, Michael Galanski, Juergen Borlak

  PloS one. 01/2012; 7(2):e30432.

  More than 100,000 chemicals are in use but have not been tested for their safety. To overcome limitations in the cancer bioassay several alternative testing strategies are explored. The inability toMore than 100,000 chemicals are in use but have not been tested for their safety. To overcome limitations in the cancer bioassay several alternative testing strategies are explored. The inability to monitor non-invasively onset and progression of disease limits, however, the value of current testing strategies. Here, we report the application of in vivo imaging to a c-Myc transgenic mouse model of liver cancer for the development of a short-term cancer bioassay. μCT and ¹⁸F-FDG μPET were used to detect and quantify tumor lesions after treatment with the genotoxic carcinogen NDEA, the tumor promoting agent BHT or the hepatotoxin paracetamol. Tumor growth was investigated between the ages of 4 to 8.5 months and contrast-enhanced μCT imaging detected liver lesions as well as metastatic spread with high sensitivity and accuracy as confirmed by histopathology. Significant differences in the onset of tumor growth, tumor load and glucose metabolism were observed when the NDEA treatment group was compared with any of the other treatment groups. NDEA treatment of c-Myc transgenic mice significantly accelerated tumor growth and caused metastatic spread of HCC in to lung but this treatment also induced primary lung cancer growth. In contrast, BHT and paracetamol did not promote hepatocarcinogenesis. The present study evidences the accuracy of in vivo imaging in defining tumor growth, tumor load, lesion number and metastatic spread. Consequently, the application of in vivo imaging techniques to transgenic animal models may possibly enable short-term cancer bioassays to significantly improve hazard identification and follow-up examinations of different organs by non-invasive methods.

• Influence of multiplanar reformations on low-contrast performance in thin-collimated multidetector computed tomography.

  Authors: Christian von Falck, Patrick Hollmann, Thomas Rodt, Stephan Waldeck, Bernhard Meyer, Frank Wacker, Hoen-Oh Shin

  Investigative radiology. 05/2011; 46(10):632-8.

  : To analyze the influence of multiplanar reformations of thin-collimated multidetector computed tomography datasets on low-contrast performance. : A low-contrast phantom simulating focal hypodense: To analyze the influence of multiplanar reformations of thin-collimated multidetector computed tomography datasets on low-contrast performance. : A low-contrast phantom simulating focal hypodense lesions (-20 HU object contrast) was scanned on a 64-slice spiral CT scanner at 4 different dose levels (25 mAs, 50 mAs, 100 mAs, 200 mAs, and no dose modulation). Other scanner parameters were as follows: tube voltage = 120 kVp, rotation time = 0.8 s, reconstructed slice thickness = 0.625 mm, reconstruction interval = 0.5 mm, reconstruction kernel = standard. Coronal reformations were created using the open-source software OsiriX. A sliding-thin-slab (STS) averaging algorithm was applied to each axial and each reformatted dataset with an increasing slab thickness from 1 to 20 slices. The low-contrast performance of all datasets was calculated semiautomatically using a reader-independent, statistical approach and is expressed as the visibility index. The results were analyzed for differences between the coronal reformations and the original axial datasets. In addition, the statistical approach used herein was validated against a reader study. : The visibility index of the coronal reformatted datasets over all lesion sizes was inferior when compared with the original axial datasets and reached 75.4% (±11.7%), 79.9% (±16.3%), 79.4% (±5.5%), and 93.7% (±14.6%) for dose levels of 25, 50, 100, and 200 mAs, respectively. The overall mean low-contrast performance was 82.1% of the axial dataset (P < 0.05, except for 200 mAs). The deterioration of low-contrast performance was inversely correlated with lesion size (R = 0.91). The use of the STS averaging algorithm significantly improved image quality for all datasets (112.6%-180.2%) with the beneficial effect being stronger for the coronal reformations. There was no statistically significant difference in the evaluation of low-contrast performance between the statistical approach and the ready study. : Coronal reformations of thin-collimated multidetector computed tomography datasets show a significant reduction of low-contrast performance when compared with the original axial dataset, especially in high noise data. The use of an STS averaging algorithm had a significant benefit for both, coronal and axial orientations. The effect was more pronounced with coronal reformations and should be routinely applied to improve image quality.

• Phantom and cadaver measurements of dose and dose distribution in micro-CT of the chest in mice.

  Authors: Thomas Rodt, Matthias Luepke, Claudia Boehm, Christian von Falck, Georg Stamm, Jürgen Borlak, Hermann Seifert, Michael Galanski

  Acta radiologica (Stockholm, Sweden : 1987). 02/2011; 52(1):75-80.

  Micro-computed tomography (CT) allows high-resolution imaging of the chest in mice for small animal research with a significant radiation dose applied. To report on measurement of the appliedMicro-computed tomography (CT) allows high-resolution imaging of the chest in mice for small animal research with a significant radiation dose applied. To report on measurement of the applied radiation dose using different scan protocols in micro-CT of the chest in mice. Repetitive dose measurements were performed for four different micro-CT protocols (with/without respiratory gating) and for micro-CT fluoroscopy used for chest imaging. Measurements were carried out using thermoluminescence dosimeters (TLD) in mouse cadavers and in a PMMA phantom allowing measurement of the radiation dose in the direct path of rays and assessment of scattered radiation. The dose measured inside and outside the chests of the cadavers varied between 190 und 210 mGy, respectively. The expected mean doses in mice in the direct path of rays for the four examined micro-CT protocols varied between 170 and 280 mGy. The mean values for 1 and 5 minutes of fluoroscopy were 17 mGy and 105 mGy, respectively. The measured dose values are similar to the dose values for micro-CT of the chest reported so far. A relevant dose can be delivered by micro-CT of the chest, which could possibly interact with small animal studies. Therefore, the applied dose for a specific protocol should be known and adverse radiation effects be considered.

• Liver and renal failure due to thrombus arising from intraaortic balloon pump.

  Authors: Nawid Khaladj, Thomas Rodt, Sven Peterss, Christian Hagl, Axel Haverich, Malakh Shrestha

  Asian cardiovascular & thoracic annals. 02/2010; 18(1):91.

• Micro-computed tomography of pulmonary fibrosis in mice induced by adenoviral gene transfer of biologically active transforming growth factor-β1.

  Authors: Thomas Rodt, Christian von Falck, Sabine Dettmer, Roman Halter, Regina Maus, Kjetil Ask, Martin Kolb, Jack Gauldie, Florian Länger, Ludwig Hoy, Tobias Welte, Michael Galanski, Ulrich A Maus, Jürgen Borlak

  Respiratory research. 01/2010; 11:181.

  Micro-computed tomography (micro-CT) is a novel tool for monitoring acute and chronic disease states in small laboratory animals. Its value for assessing progressive lung fibrosis in mice has notMicro-computed tomography (micro-CT) is a novel tool for monitoring acute and chronic disease states in small laboratory animals. Its value for assessing progressive lung fibrosis in mice has not been reported so far. Here we examined the importance of in vivo micro-CT as non-invasive tool to assess progression of pulmonary fibrosis in mice over time. Pulmonary fibrosis was induced in mice by intratracheal delivery of an adenoviral gene vector encoding biologically active TGF-β1 (AdTGF-β1). Respiratory gated and ungated micro-CT scans were performed at 1, 2, 3, and 4 weeks post pulmonary adenoviral gene or control vector delivery, and were then correlated with respective histopathology-based Ashcroft scoring of pulmonary fibrosis in mice. Visual assessment of image quality and consolidation was performed by 3 observers and a semi-automated quantification algorithm was applied to quantify aerated pulmonary volume as an inverse surrogate marker for pulmonary fibrosis. We found a significant correlation between classical Ashcroft scoring and micro-CT assessment using both visual assessment and the semi-automated quantification algorithm. Pulmonary fibrosis could be clearly detected in micro-CT, image quality values were higher for respiratory gated exams, although differences were not significant. For assessment of fibrosis no significant difference between respiratory gated and ungated exams was observed. Together, we show that micro-CT is a powerful tool to assess pulmonary fibrosis in mice, using both visual assessment and semi-automated quantification algorithms. These data may be important in view of pre-clinical pharmacologic interventions for the treatment of lung fibrosis in small laboratory animals.

• F-18 2-fluoro-2-deoxy-glucose positron emission tomography/computed tomography for the detection of radicular and peripheral neurolymphomatosis: correlation with magnetic resonance imaging and ultrasound.

  Authors: Christian von Falck, Thomas Rodt, Steffen Joerdens, Stephan Waldeck, Holger Kiesel, Wolfram H Knapp, Michael Galanski

  Clinical nuclear medicine. 09/2009; 34(8):493-5.

  Neurolymphomatosis is an uncommon extranodal manifestation of non-Hodgkin lymphoma. It may mimic a broad variety of neurologic conditions which renders clinical diagnosis challenging. As blind nerveNeurolymphomatosis is an uncommon extranodal manifestation of non-Hodgkin lymphoma. It may mimic a broad variety of neurologic conditions which renders clinical diagnosis challenging. As blind nerve biopsy is invasive and may be false negative, surrogate criteria for the diagnosis of neurolymphomatosis have been proposed based on magnetic resonance imaging/computed tomography findings. However, these morphologic modalities may suffer from limited sensitivity. Recently, a few reports have been published that discuss a possible advantage of F-18 2-fluoro-2-deoxy-glucose positron emission tomography/computed tomography (F-18 FDG PET/CT) in these patients.We report the case of a 41-year-old man who presented with progressive tetraparesis and dysaesthesia, in which F-18 FDG PET/CT aided to the diagnosis of neurolymphomatosis due to a large B-cell lymphoma. The patient received chemotherapy (R-CHOP) and the neurologic symptoms were clearly regressive. Three months after the end of systemic chemotherapy the patient presented again with progressive neurologic symptoms. A second PET/CT was performed and demonstrated disease recurrence in the right testis as well as widespread neurolymphomatosis. Additional ultrasound and magnetic resonance imaging examinations were performed and confirmed infiltration of the left brachial plexus, the right femoral, and the right sciatic nerve.We present this case to support the hypothesis that F-18 FDG PET/CT is a valuable imaging modality in patients with suspected neurolymphomatosis. It allows one to accurately determine the extent of the disease in a single whole-body examination.

• In vivo microCT quantification of lung tumor growth in SPC-raf transgenic mice.

  Authors: Thomas Rodt, Christian von Falck, Roman Halter, Kristina Ringe, Hoen-Oh Shin, Michael Galanski, Juergen Borlak

  Frontiers in bioscience : a journal and virtual library. 02/2009; 14:1939-44.

  Lung cancer is the most common cancer worldwide. Early detection might reduce morbidity. In this study we evaluate a microCT imaging algorithm to assess in-vivo tumour load and quantification ofLung cancer is the most common cancer worldwide. Early detection might reduce morbidity. In this study we evaluate a microCT imaging algorithm to assess in-vivo tumour load and quantification of tumour growth in a transgenic disease model of lung adenocarcinomas. MicroCT was carried out with n=10 SPC-raf transgenic mice without gating in spontaneously breathing and isoflurane anaesthetised animals. Segmentation of the air-filled spaces was obtained using a region growing algorithm by 3 independent observers. Inter- and intra-observer variability of the algorithm was determined and compared against an alternative region growing algorithm. Due to the multiple very small tumor nodules that occur and the low signal-to-noise ratio direct volumetric measurement of solitary tumor nodules is not feasible. However, tumor growth can be assessed by measuring the decrease in the segmented volume of the aerated lung areas. The presented algorithm can thus be used to evaluate therapeutic efficacies of novel treatment strategies. The imaging algorithm allows in vivo quantification of lung tumor load and tumor growth in transgenic mice with an acceptable intra- and interobserver variability.

• Combined microPET/CT for imaging of hepatocellular carcinoma in mice.

  Authors: Christian von Falck, Thomas Rodt, Roman Halter, Reinhard Spanel, Michael Galanski, Juergen Borlak

  Frontiers in bioscience : a journal and virtual library. 02/2009; 14:2193-202.

  The EGF-transgenic mouse is a genetic model of hepatocellular carcinoma that allows for a comprehensive study of signal pathways, molecular interactions and the evaluation of novel therapeuticThe EGF-transgenic mouse is a genetic model of hepatocellular carcinoma that allows for a comprehensive study of signal pathways, molecular interactions and the evaluation of novel therapeutic concepts. In this regard, non-invasive imaging tools for serial in-vivo monitoring of tumor load and growth are highly desirable. This study therefore aimed at demonstrating the feasibility of non-invasive in-vivo imaging of primary liver malignancies in mice using combined contrast-enhanced microCT and F-18 FDG microPET. In our murine disease model, microCT enabled imaging of primary liver tumors down to a lesional diameter of 0.9 mm. F-18 FDG tumor-to-non-tumor ratio of HCCs was observed to be dependent on lesion size and linked to overpression of glucose transporters and hexokinase isoenzymes as determined by gene expression studies. Histopathologic analyses indicated an increased cellular dedifferentiation with increase lesion size, as well.

• F-18 FDG PET imaging of fibrolamellar hepatocellular carcinoma.

  Authors: Christian von Falck, Thomas Rodt, Hoen-Oh Shin, Wolfram H Knapp, Michael Galanski

  Clinical nuclear medicine. 10/2008; 33(9):633-4.

• (68)Ga-DOTANOC PET/CT for the detection of a mesenchymal tumor causing oncogenic osteomalacia.

  Authors: Christian von Falck, Thomas Rodt, Herbert Rosenthal, Florian Länger, Thomas Goesling, Wolfram H Knapp, Michael Galanski

  European journal of nuclear medicine and molecular imaging. 06/2008; 35(5):1034.

• Expression of bcl-2 is associated with microvessel density in olfactory neuroblastoma.

  Authors: Marc Diensthuber, Marc Potinius, Thomas Rodt, Alexandru Stan, Hans Welkoborsky, Madjid Samii, Jonas Schreyögg, Thomas Lenarz, Timo Stöver

  Journal of neuro-oncology. 05/2008;

  Erythropoietin (Epo) expression is regulated via hypoxia-inducible factor (HIF)-1alpha-directed gene transcription. Activation of the erythropoietin receptor (EpoR) by Epo leads to elevatedErythropoietin (Epo) expression is regulated via hypoxia-inducible factor (HIF)-1alpha-directed gene transcription. Activation of the erythropoietin receptor (EpoR) by Epo leads to elevated expression of the anti-apoptotic protein, bcl-2, which has recently been shown to promote angiogenesis in malignant tumors. Expression of HIF-1alpha, Epo, EpoR, and bcl-2 was studied by immunohistochemistry in a series of 20 olfactory neuroblastoma (ONB) samples. Data were correlated with microvessel density, proliferative activity, and apoptosis in the specimens and survival analysis was performed to investigate the prognostic value of the examined factors. Immunohistochemical analysis revealed robust expression of HIF-1alpha, Epo, EpoR, and bcl-2 in ONB. Ninety percent of the samples showed HIF-1alpha immunoreactivity and in 60% of the cases, bcl-2 immunoreactivity was observed. A significant positive correlation between the expression levels of HIF-1alpha and bcl-2 and the microvessel density was found. Survival analysis did not reveal any prognostic significance for the tested factors. Expression of HIF-1alpha, Epo, Epo-R, and bcl-2 may play a functional role in ONB pathogenesis. Our data suggest that bcl-2 may act as a stimulator of angiogenesis in ONB, and thus represents a novel target for anti-angiogenic treatment strategies in the therapy of ONB.

• 3D visualization and simulation of frontoorbital advancement in metopic synostosis.

  Authors: Thomas Rodt, Arkadius Schlesinger, Alexander Schramm, Marc Diensthuber, Marion Rittierodt, Joachim K Krauss

  Child's nervous system : ChNS : official journal of the International Society for Pediatric Neurosurgery. 12/2007; 23(11):1313-7.

  OBJECTIVES: Current multislice computed tomography (CT) technology can be used for diagnosis and surgical planning applying computer-assisted three-dimensional (3D) visualization and surgicalOBJECTIVES: Current multislice computed tomography (CT) technology can be used for diagnosis and surgical planning applying computer-assisted three-dimensional (3D) visualization and surgical simulation. The usefulness of a technique for surgical simulation of frontoorbital advancement is demonstrated here in a child with metopic synostosis. MATERIALS AND METHODS: Postprocessing of multi-slice CT data was performed using the software 3D slicer. 3D models were created for the purpose of surgical simulation. These allow planning the course of the osteotomies and individually placing the different bony fragments by an assigned matrix to simulate the surgical result. Photo documentation was obtained before and after surgery. Surgical simulation of the procedure allowed determination of the osteotomy course and assessment of the positioning of the individual bony fragments. CONCLUSIONS: Computer-assisted postprocessing and simulation is a useful tool for surgical planning in craniosynostosis surgery. The time-effort for segmentation currently limits the routine clinical use of this technique.

• Erythropoietin and erythropoietin receptor expression in vestibular schwannoma: potential role in tumor progression.

  Authors: Marc Diensthuber, Torben Ilner, Thomas Rodt, Madjid Samii, Almuth Brandis, Thomas Lenarz, Timo Stöver

  Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 07/2007; 28(4):559-65.

  HYPOTHESIS: Hypoxia-inducible factor (HIF)-1alpha, erythropoietin (Epo), Epo receptor (EpoR), and bcl-2 are expressed in both sporadic unilateral vestibular schwannomas (VSs) and those associatedHYPOTHESIS: Hypoxia-inducible factor (HIF)-1alpha, erythropoietin (Epo), Epo receptor (EpoR), and bcl-2 are expressed in both sporadic unilateral vestibular schwannomas (VSs) and those associated with neurofibromatosis Type 2, and the expression data correlate with clinicopathological tumor features including microvessel density and Ki-67-labeling index. BACKGROUND: Erythropoietin expression is regulated by the transcription factor, HIF-1alpha. Erythropoietin signaling via EpoR results in stimulation of cell proliferation and elevated expression of the antiapoptotic protein, bcl-2, and then inhibition of apoptosis. Erythropoietin has been shown to be associated with Schwann cell proliferation, and a recent report suggested a role in VS growth. METHODS: Immunohistochemical analysis of HIF-1alpha, Epo, EpoR, and bcl-2 was performed on formalin-fixed paraffin-embedded archival surgical specimens. Microvessel density and Ki-67-labeling index of VS were analyzed and correlated with the immunoreactivity pattern of the examined factors. RESULTS: Immunoreactivity data demonstrate robust protein expression for HIF-1alpha, Epo, EpoR, and bcl-2 in VS. Sixty-six percent of the cases showed Epo expression, and EpoR was found in 85% of tumor samples. A significantly positive correlation of the immunoreactivity scores of Epo/EpoR and bcl-2 expression could be noted. In case of tumor specimens with high levels of HIF-1alpha expression, a significantly higher Ki-67-labeling index was observed. There was no correlation between the expression of HIF-1alpha, Epo, EpoR, and bcl-2 and microvessel density, tumor size, sex, and age. CONCLUSION: Expression of Epo and EpoR might suggest a functional role in VS biology. The observed correlation of Epo/EpoR and bcl-2 expression levels may suggest a proliferative and antiapoptotic role of the Epo/EpoR system in VS.

• Placement of intraventricular catheters using flexible electromagnetic navigation and a dynamic reference frame: a new technique.

  Authors: Thomas Rodt, Gregory Köppen, Martin Lorenz, Omid Majdani, Martin Leinung, Soenke Bartling, Jan Kaminsky, Joachim K Krauss

  Stereotactic and functional neurosurgery. 02/2007; 85(5):243-8.

  BACKGROUND: Catheterization of narrow ventricles may prove difficult resulting in misplacement or inefficient trials with potential damage to brain tissue. MATERIAL AND METHODS: The application of aBACKGROUND: Catheterization of narrow ventricles may prove difficult resulting in misplacement or inefficient trials with potential damage to brain tissue. MATERIAL AND METHODS: The application of a new module for navigated ventricular catheterization using flexible electromagnetic navigation and a dynamic reference frame is presented. RESULTS: Navigated catheter placement was successful and accurate in a pilot study. Electromagnetic interferences had to be taken into consideration. CONCLUSION: Flexible electromagnetic navigation with a dynamic reference frame is a useful tool for catheter placement as it reduces the risk of misplacement or repeated catheterization trials.

• Increase of accuracy in intraoperative navigation through high-resolution flat-panel volume computed tomography: experimental comparison with multislice computed tomography-based navigation.

  Authors: Soenke H Bartling, Martin Leinung, Johannes Graute, Thomas Rodt, Christian Dullin, Hartmut Becker, Thomas Lenarz, Timo Stover, Omid Majdani

  Otology & neurotology : official publication of the American Otological Society, American Neurotology Society [and] European Academy of Otology and Neurotology. 02/2007; 28(1):129-34.

  HYPOTHESIS: High-resolution imaging, as provided by flat-panel-based volume computed tomography (fpVCT), could increase navigation accuracy and could therefore improve image-guided procedures or makeHYPOTHESIS: High-resolution imaging, as provided by flat-panel-based volume computed tomography (fpVCT), could increase navigation accuracy and could therefore improve image-guided procedures or make novel navigated surgery concepts possible. BACKGROUND: Intraoperative navigation is an accepted tool in head and neck surgery. However, its use is limited in the lateral cranial base because of its low surgical accuracy. Surgical accuracy is substantially influenced by the resolution of the underlying data set. The fpVCT offers a resolution of nearly two times higher than multislice computed tomography (MSCT). Target registration error (TRE), as a measurement for surgical navigation accuracy, should decrease when navigation is based on fpVCT data sets. METHODS: An acrylic glass phantom with 37 fiducial points was scanned in a current MSCT and in an experimental fpVCT. Both data sets were imported in an optical navigation system. Five fiducial points were used for registration, and seven points were used for measuring TRE. The distance between the indicated pointer tip and the corresponding fiducial point in data set was measured as TRE. Registration and TRE measurement were repeated five times for each computed tomographic data set. Average TREs were calculated, and results were compared using t-test. RESULTS: The average TRE using MSCT (0.82 mm [standard deviation, 0.35 mm]) was significantly higher than that using fpVCT (0.46 mm [standard deviation, 0.22 mm]) (p < 0.01). CONCLUSION: Submillimeter surgical navigation accuracy is possible using high-resolution fpVCT. This could be highly beneficial in cranial base surgery navigation.

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• A universal algorithm for an improved finite element mesh generation Mesh quality assessment in comparison to former automated mesh-generators and an analytic model.

  Authors: Jan Kaminsky, Thomas Rodt, Alireza Gharabaghi, Jan Forster, Gerd Brand, Madjid Samii

  Medical engineering & physics. 07/2005; 27(5):383-94.

  The FE-modeling of complex anatomical structures is not solved satisfyingly so far. Voxel-based as opposed to contour-based algorithms allow an automated mesh generation based on the image data.The FE-modeling of complex anatomical structures is not solved satisfyingly so far. Voxel-based as opposed to contour-based algorithms allow an automated mesh generation based on the image data. Nonetheless their geometric precision is limited. We developed an automated mesh-generator that combines the advantages of voxel-based generation with improved representation of the geometry by displacement of nodes on the object-surface. Models of an artificial 3D-pipe-section and a skullbase were generated with different mesh-densities using the newly developed geometric, unsmoothed and smoothed voxel generators. Compared to the analytic calculation of the 3D-pipe-section model the normalized RMS error of the surface stress was 0.173-0.647 for the unsmoothed voxel models, 0.111-0.616 for the smoothed voxel models with small volume error and 0.126-0.273 for the geometric models. The highest element-energy error as a criterion for the mesh quality was 2.61x10(-2) N mm, 2.46x10(-2) N mm and 1.81x10(-2) N mm for unsmoothed, smoothed and geometric voxel models, respectively. The geometric model of the 3D-skullbase resulted in the lowest element-energy error and volume error. This algorithm also allowed the best representation of anatomical details. The presented geometric mesh-generator is universally applicable and allows an automated and accurate modeling by combining the advantages of the voxel-technique and of improved surface-modeling.

• In Contrast to Multi-slice CT (MSCT)-based Navigation, High Resolution Flat-panel-based Volume-CT (fpVCT) Allows for Submillimetric Navigation Accuracy

  Authors: Soenke Bartling, Johannes Graute, Martin Leinung, Thomas Rodt, Christian Dullin, Omid Majdani

  RSNA, Chicago; 01/2005

  PURPOSE Intraoperative navigation based on MSCT datasets is a well established method in neurosurgery and ENT surgery. However, depending on registration method and navigation hardware used, noPURPOSE Intraoperative navigation based on MSCT datasets is a well established method in neurosurgery and ENT surgery. However, depending on registration method and navigation hardware used, no accuracy higher then 0,7-1 mm in average was yet reached. The resolution of the underlying dataset could be one significant influence factor to the navigation accuracy; therefore we wondered whether ultra high resolution imaging provided by flat-panel based Volume-CT translates to higher navigation accuracy. METHOD AND MATERIALS An acrylic glass phantom providing numerous navigation fiducial markers in form of inverted cones was designed. It was scanned in a in a state of the art MSCT (GE Lightspeed 16) and an experimental fpVCT (GE). MSCT scanning was performed to optimize the spatial resolution (120kV, 80 mA, 0,625 mm collimation) as were reconstruction (9,6 cm rFOV, 512*512 matrix, 0,3 mm z-spac, “boneplus” kernel). The fpVCT scanner consisted of one flat-panel detector mounted on a standard CT gantry. High resolution scanning (1000 projections, 140kV, 25 mA) and modified FDK reconstruction were performed. The navigation reference star was rigidly attached to the phantom. Both datasets were loaded into the VectorVision² (BrainLAB) optical navigation system. For registration, six corresponding cone tips have been identified in datasets as well as in the phantom using a standard pointer instrument. Target registration error (TRE) have been measured on 35 fiducial points. Average TRE was calculated, compared and two sided t-Test performed. RESULTS Average TRE using MSCT was 0.66 mm (SD 0.38) and therefore higher (p=0,007) then using fpVCT 0,41 (SD 0.12). CONCLUSION High resolution fpVCT could improve intraoperative navigation accuracy. This could be highly beneficial for skull base surgery, where precise image guided interventions such as cochleostomie or stereotactic drilling biopsies could become possible. These now available high resolution imaging methods urge for good registration methods together with precise navigation systems and/or robotic support to make this increased accuracy available for novel surgery concepts.

• Specially adapted interactive tools for an improved 3D-segmentation of the spine.

  Authors: Jan Kaminsky, Petra Klinge, Thomas Rodt, Martin Bokemeyer, Wolf Luedemann, Madjid Samii

  Computerized medical imaging and graphics : the official journal of the Computerized Medical Imaging Society. 05/2004; 28(3):119-27.

  For imaging purposes of the spine, segmented image data provides the basis for a variety of modern clinical applications. However, the anatomical complex structure of the spine as well as theFor imaging purposes of the spine, segmented image data provides the basis for a variety of modern clinical applications. However, the anatomical complex structure of the spine as well as the extensive degenerative bony deformations apparent in the clinical situation, generally complicate the application of a fully automated segmentation. To serve the special needs for image segmentation of the spine anatomy a newly developed software system is presented, that implements specially adapted interactive tools, taking its 'axis'-skeletal structure into account. A standardized protocol combines the newly developed interactive tools (rotation transformation, warped dissection plane) with standard segmentation tools to provide both a fast and accurate segmentation procedure. The introduced software environment has been valuable for the segmentation of cervical, thoracic and lumbar spines segments based on clinical routine and research images.

• 3D-Nachverarbeitung in der CT-Bildgebung des Felsenbeins.

  Authors: Thomas Rodt, Sönke Bartling, Hartmut Burmeister, Kersten Peldschuss, Peter Issing, Thomas Lenarz, Hartmut Becker, Herbert K. Matthies

  Bildverarbeitung für die Medizin 2003, Algorithmen - Systeme - Anwendungen, Proceedings des Workshops vom 9. bis 11. März 2003 in Erlangen; 01/2003