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SummaryThe vascular anatomy of the liver can be described at three different levels of complexity according to the use that the description has to serve. The first – conventional – level corresponds to the traditional 8-segments scheme of Couinaud and serves as a common language between clinicians from different specialties to describe the location of focal hepatic lesions. The second – surgical – level, to be applied to anatomical liver resections and transplantations, takes into account the real branching of the major portal pedicles and of the hepatic veins. Radiological and surgical techniques exist nowadays to make full use of this anatomy, but this requires accepting that the Couinaud scheme is a simplification, and looking at the vascular architecture with an unprejudiced eye. The third – academic – level of complexity concerns the anatomist, and the need to offer a systematization that resolves the apparent contradictions between anatomical literature, radiological imaging, and surgical practice. Based on the real number of second-order portal branches that, although variable averages 20, we submit a system called the “1-2-20 concept”, and suggest that it fits best the number of actual – as opposed to idealized – anatomical liver segments.

Objectives: Virtual imaging procedures have only rarely been analyzed in pediatric populations. We evaluated the role of CT-based virtual surgery planning in pediatric patients experiencing hepatic vascular malformations (HVM). Methods: We analyzed 12 children with complex hepatic vascular malformations. All of the children received multislice CT scans with contrast medium followed by virtual 3-dimensional reconstructions using the software assistants MeVis LiverAnalyzer and MeVis LiverExplorer. The impact on treatment planning and the correspondence to clinical findings was assessed. Results: Highest accuracies of virtual data were found in cases of intrahepatic portocaval shunt and persistent ductus venosus. Here, virtual data revealed congenital vascular conditions, which were not always seen using standard imaging diagnostics. In some patients with portalvenous thrombosis, virtual imaging provided important contributions to determining the feasibility of different shunt procedures. However, in some patients experiencing portalvenous thrombosis or liver diffuse hemangioma, virtual methods were not as accurate as standard diagnostic procedures. Nevertheless, these tools facilitated simultaneous and continuous illustrations ofthe different vascular systems. Conclusions: Virtual imaging and planning procedures had an important impact on treatment strategies and outcomes in children with HVM. Their use as standard diagnostic tools in selected cases of HVM should be considered.

To quantify the cooling effect of hepatic vessels on liver radiofrequency (RF) ablation ex situ. Bipolar RF applicators (diameter = 1.8 mm, electrode length = 30 mm) were inserted parallel to perfused glass tubes (diameter = 5 and 10 mm; flow = 250–1,800 ml/min) at distances of 5 and 10 mm in porcine livers ex vivo. RF ablation was performed at 30 W/15 kJ. RF lesions were analyzed by measuring the maximum (r max) and minimum radius (r min) and the lesion area. Glass tubes without flow showed no influence on RF lesions, whereas perfused glass tubes had a significant cooling effect on lesions. r min was reduced to 50% at 5 mm applicator-to-vessel distance and the lesion area was reduced from 407 to 321 mm2 (p

This article presents advanced algorithms for segmenting lung nodules, liver metastases, and enlarged lymph nodes in CT scans. Segmentation and volumetry are essential tasks of a software assistant for oncological therapy monitoring. Our methods are based on a hybrid algorithm originally developed for lung nodules that combines a threshold-based approach with model-based morphological processing. We propose extensions that deal with particular challenges of each lesion type: lung nodules that are attached to non-convex parts of the pleura, rim-enhancing and peripheral liver metastases and lymph nodes with an extensive contact to structures of similar density. We evaluated our methods on several hundred lesions in clinical datasets and the quality of segmentations was rated by radiologists. The results were classified as acceptable or better in 81% to 92% of the cases for the different algorithms and readers.

Ziel: Durch innovative Neuerungen im Bereich der Schichtbildverfahren gewinnt die Ganzkörperbildgebung, insbesondere zur Diagnostik systemischer Tumorerkrankungen, zunehmend an Bedeutung für die klinische Radiologie. Die erhebliche Zahl zu beurteilender Bilder bei zunehmender Arbeitsverdichtung stellt ein wachsendes Problem für den Radiologen dar. Ziel der Arbeit war die Entwicklung und Evaluierung eines Computer-unterstützten Befundungstools, das den Ablauf der Befunderstellung von Ganzkörper-MRT-Datensätzen automatisiert unterstützt. Material und Methoden: Es wurden 13 Ganzkörper-MRT-Datensätze von Patienten mit malignem Melanom sowohl mit konventioneller als auch mit workflowoptimierter Befundungssoftware im Rahmen einer Multireader-Analyse befundet. Zur quantitativen Auswertung wurden von den 3 geblindeten Readern jeweils die Zeiten zum Laden des Datensatzes, die Dauer der Auswertung einer Körperregion (jeweils Kopf, Hals, Thorax, Abdomen und Becken/Skelettsystem) sowie die Dauer zum Wiederauffinden eines vorbeschriebenen Befundes verglichen. Zusätzlich wurde ein Student-t-Test ausgeführt. Für die qualitative Auswertung wurden jeweils der Komfort beim Laden, die Hilfe beim Finden von Läsionen und der Bedienkomfort getrennt bewertet und der Kappa-Wert auf einer Skala von 0 - 4 (0 = schlecht, 4 = sehr gut) berechnet. Ergebnisse: Die Ladezeiten der Untersuchungen betrugen bei dem konventionellen Befundungssystem 39,7 s (± 5,5) und bei dem workflowoptimierten 6,5 s (± 1,4) (p < 0,01), dies entspricht einer durchschnittlichen Verkürzung der Ladezeiten um 83,6 %. In der Kopfregion konnte mittels Befundnavigator die Befundungszeit (konventionell/workflowoptimiert) bei Reader 1/2/3 um 35,9 % (p < 0,01)/49,9 % (p < 0,01)/54,3 % (p < 0,01), in der Halsregion um 48,5 % (p < 0,01)/ 52,6 % (p < 0,01)/59,4 % (p < 0,05), in der Thoraxregion um 59,1 % (p < 0,01)/56,2 % (p < 0,05)/62,1 % (p < 0,05), in der Abdomenregion um 61,9 % (p < 0,01)/62,7 % (p < 0,05)/47,9 % (p < 0,01) und in der Beckenregion um 73,1 % (p < 0,01)/63,7 % (p < 0,05)/ 55 % (p < 0,01) verkürzt werden. Zum Wiederauffinden eines vorbeschriebenen Befundes wurden 148,2 s (± 94,8) gegenüber 2,5 s (± 0,5) benötigt (p < 0,01). Mit und ohne Befundnavigator wurde dieselbe Anzahl an Metastasen gefunden (p < 0,01, k > 0,9). Die qualitative Analyse zeigte in allen Kategorien einen signifikanten Komfortgewinn (p < 0,01, k > 0,9). Schlussfolgerung: Durch den Einsatz der entwickelten Befundungssoftware kann eine signifikante Zeitersparnis bei der Befundung von Ganzkörper-MRT-Datensätzen bei gleichbleibender Befundungsqualität und signifikantem Komfortgewinn erzielt werden. Durch diese Workflowoptimierung erscheint eine breitere klinische Anwendung von Ganzkörperuntersuchungen hinsichtlich der Befundung sowie Befunddemonstration möglich zu werden.

Accurate knowledge of partial anatomy is essential in hepatic surgery but is difficult to acquire. We describe the potential impact of a new technique for constructing three-dimensional virtual images of the portal vein, hepatic artery, and bile ducts and present a representative case. An 80-year-old man was suspected of having papillary cholangiocarcinoma arising in S8 of the liver and extending to the hepatic hilum intraluminaly. Right hemihepatectomy with bile duct resection was planned. However, it was uncertain whether duct-to-duct biliary reconstruction would be possible based on the appearance of the confluence of the right and left hepatic ducts on cholangiogram and conventional computed tomograph. Virtual three-dimensional images of the liver were constructed and revealed vascular and biliary anatomy. They showed that the upper margin of bile duct excision would be 19 mm from the umbilical point of the left portal vein, and that the site of the left branch of the caudate lobe bile duct could be preserved. Based on this information, we performed a sphincter-preserving biliary operation safely without complications. Planning complex biliary surgery may be improved by the use of virtual three-dimensional images of the liver. This approach is especially useful in candidates for postoperative regional chemotherapy.

Volumetric growth assessment of pulmonary lesions is crucial to both lung cancer screening and oncological therapy monitoring. While several methods for small pulmonary nodules have previously been presented, the segmentation of larger tumors that appear frequently in oncological patients and are more likely to be complexly interconnected with lung morphology has not yet received much attention. We present a fast, automated segmentation method that is based on morphological processing and is suitable for both small and large lesions. In addition, the proposed approach addresses clinical challenges to volume assessment such as variations in imaging protocol or inspiration state by introducing a method of segmentation-based partial volume analysis (SPVA) that follows on the segmentation procedure. Accuracy and reproducibility studies were performed to evaluate the new algorithms. In vivo interobserver and interscan studies on low-dose data from eight clinical metastasis patients revealed that clinically significant volume change can be detected reliably and with negligible computation time by the presented methods. In addition, phantom studies were conducted. Based on the segmentation performed with the proposed method, the performance of the SPVA volumetry method was compared with the conventional technique on a phantom that was scanned with different dosages and reconstructed with varying parameters. Both systematic and absolute errors were shown to be reduced substantially by the SPVA method. The method was especially successful in accounting for slice thickness and reconstruction kernel variations, where the median error was more than halved in comparison to the conventional approach.

In this paper we present a method to automatically detect the coronary arteries in CT angiographic images after a single user click into the aorta. The algorithm consists of three steps: the masking of the aorta, the analysis of connected regions outside the aorta, and the vessel segmentation starting from the detected seed clusters. The aorta segmentation and the detection of voxel clusters at the coronary artery origins is based on a statistical analysis of regions segmented by a 2D region growing algorithm. The method has been tested with 61 data sets from different sites and different CT scanners including cases with abnormal anatomy or bad image quality Reasonable results were produced in all cases. In 57% of all cases, both coronary arteries were detected, while in 85% at least one coronary artery could be found. As the results can be easily extended manually by mouse clicks into arteries that were not detected automatically the presented method is appropriate as a first step in an advanced analysis of the coronary tree.

A software tool was developed for the volumetric measurement of lung nodules, liver metastasis and lymph nodes to support decision making in treatment planning and monitoring with respect to convenience, accuracy and time consumption.

Purpose Three-dimensional visualization of solid tumors is possible because of high-resolution computed tomography and magnetic resonance imaging scans. However, additional preoperative information is often desirable in complex malignancies. For the first time, the authors present a model of preoperative 3-dimensional visualization and virtual resections in pediatric solid tumors. Methods Image analysis of various pediatric tumors was performed using the research software HepaVision2 (MeVis, Bremen). Organs, tumors, and the vascular system were extracted from multislice computed tomography scans. After hierarchical analysis of the vascular system, territories supplied or drained by the major vascular branches were calculated. Results were explored and virtual resections of organs were carried out using the research software InterventionPlanner (MeVis, Bremen). Data were correlated to intraoperative findings. Results Four hepatic malignancies, 4 renal tumors, and 3 other neoplasms were analyzed. The technique of 3-dimensional visualization was feasible for all investigated children (mean age 5 years and 9 months). Spatial relations between physiological and pathological structures were identified, and anatomical structures (vessels, tumor tissue, and organ parenchyma) were determined using colorimetric encoding. Virtual simulations of tumor resection were used successfully for planning of surgical procedures in the hepatic and renal tumors. Conclusions The technique of 3-dimensional tumor visualization and virtual simulation of tumor resections provides the basis for a successful planning of complex tumor resections in children. The efficiency of these techniques should be further analyzed in series with higher numbers and differentiations of tumors.

PURPOSE A retrospective clinical-histological study to determine the diagnostic accuracy of mammography using conventional screen-film cassettes (hard copy), high-resolution digital phosphor storage plates (hard copy) and monitor display (soft copy) for microcalcifications and focal lesions (BI-RADS (TM) category 4 or 5). MATERIALS AND METHODS From April to November 2001, 76 patients underwent conventional film-screen mammography and, after diagnosis and preoperative wire localization, digital mammography with the same exposure parameters. Five investigators retrospectively determined the diagnosis after the operation from randomly distributed mediolateral views (hard-copy reading) and from the monitor display (soft-copy reading). These results were correlated with the final histology. RESULTS The accuracy of conventional screen-film mammography, digital mammography and monitor-displayed mammography was 67%, 65% and 68% for all findings, (n = 76), 59%, 59% and 68% for microcalcifications (n = 44) and 75%, 72% and 63% for focal lesions (n = 32). The overall results showed no difference. CONCLUSION Our findings indicate equivalence of conventional screen-film mammography, high-resolution digital phosphor storage plate mammography and monitor-displayed mammography.

New visualization techniques for the diagnosis of nodules in high-resolution thorax CT data from multi-slice scanners are presented. The techniques are based on segmentation of the lungs and multiple projection views as well as nonlinear reformatting of the data. In particular, the visibility of small nodules close to the pleura or mediastinum may be increased substantially.

The acceptance of computer assisted surgical planning was studied by polling 500 German surgeons. 500 questionnaires were sent, from which 105 have been returned, from which 102 could be analysed. The questionnaire consisted of 14 questions relating to the current practice of surgery planning as well as to desired improvements. In general, the computer assisted surgical planning was assessed as a promising tool in the future. 82 % of the surgeons expected a benefit by computer assisted surgical planning. Better assessment of resectability, better training of residents and more safety of surgical procedures were mentioned in the majority. Computer assisted surgical planning should focus on 3D visualization of spatial relations between lesions and vascular structures, on facilities for the preoperative trial of resection strategies and on the documentation of the planned procedure. The current version of a research prototype (Surgery-Planner) is presented which is dealing with these goals.

This paper presents image-guided therapies development and advantages using real time imaging modalities such as computed tomography, ultrasound imaging, and magnetic resonance imaging. The following are also highlighted: image-guided cancer interventions and image-guided cardiovascular interventions.

Run-length coding has attracted much attention in wavelet-based image compression because of its simplicity and potentially low complexity. The main drawback is the inferior RD-performance compared to the state-of-the-art-coder SPIHT. In this paper, we concentrate on the embedded progressive run-length code of Tian and Wells (1996, 1998). We consider significance sequences drawn from the scan in the dominant pass. It turns out that self-similar curves for scanning the dominant pass increase the compression efficiency significantly. This is a consequence of the correlation of direct neighbors in the wavelet domain. This dependence can be better exploited by using groups of coefficients, similar to the SPIHT algorithm. This results in a new and very fast coding algorithm, which shows performance similar to the state-of-the-art coder SPIHT, but with lower complexity and small and fixed memory overhead.

The carriers of the German Statutory Health Care System have recognized that only mammographic screening according to the European Guidelines for the Quality Assurance of Mammography Screening will permit early detection of breast cancer with an acceptable risk/benefit ratio. In the German pilot projects, regional mammography screening programmes according to the European guidelines are being tested in the framework of the German health care system. The European guidelines require comprehensive quality assurance of all relevant steps in the chain of events involved in screening, from invitation on to therapy and follow-up. Such comprehensive quality assurance involves several medical specialities and other professional groups dealing with out-patient and in-patient health care and requires long-term cooperation with public institutions (population registries, cancer registries). The objective of the pilot projects is to test the organizational and legal conditions essential to introduction of a mammographic screening programme according to the European quality assurance guidelines in Germany.

The description of the rescaled evolution set of p-Fermat cellular automata developed in the first part of this paper is applied for the calculation of the Hausdorff dimension of this set. The scaling procedure is analyzed and an appropriate scaling sequence for cellular automata with states in the integers modulo m is given. New proof of the main theorem of the first part of the paper is presented for the linear cellular automata with states in the integers modulo a power of prime number.

Die Bedeutung von VR-Anwendungen ergibt sich v.a. dadurch, dass neben dem geometrischen Modell auch ein funktionelles Modell erstellt wird, das Manipulationen erlaubt und quantitative Analysen einschliest.

Purpose We sought was to quantify and visualize the regeneration of the remnant liver after living donor liver transplantation using computed tomographic (CT) data. Methods For the evaluation of preoperative and follow-up data, we developed a software assistant that was able to compute the volume growth of the remnant liver and liver territories as well as visualize the individual growth of hepatic vessels over time. The software was applied to CT data of 20 donors who underwent right hepatectomy including the middle hepatic vein with at least 3 follow-up examinations in the first year after transplantation. Results After donation of a right lobe graft, the remnant liver regenerated by an average 77% of the original volume within the first 3 postoperative months and to 86% within the first year. The growth of the left lateral segments was increased compared with that of segment IV in all cases. The visualization showed the growth of the portal vein and the hepatic veins. With the simultaneous display of pre- and postoperative results, it was possible to detect the formation of collaterals between truncated segment IVb veins and the veins of segment IVa or of the left lateral lobe. Conclusion The software-assisted analysis of follow-up data yielded additional insight into territorial liver regeneration after living donor liver transplantation and allowed for reliable detection of relevant hepatic vein collaterals using CT data.

Purpose In a clinical study, the feasibility of using a mammography workstation for the display and interpretation of digital mammography images was evaluated and the results were compared with the corresponding laser film hard copies. Materials and methods Digital phosphorous plate radiographs of the entire breast were obtained in 30 patients using a direct magnification mammography system. The images were displayed for interpretation on the computer monitor of a dedicated mammography workstation and also presented as laser film hard copies on a film view box for comparison. The images were evaluated with respect to the image handling, the image quality and the visualization of relevant structures by 3 readers. Results Handling and contrast of the monitor displayed images were found to be superior compared with the film hard copies. Image noise was found in some cases but did not compromise the interpretation of the monitor images. The visualization of relevant structures was equal with both modalities. Altogether, image interpretation with the mammography workstation was considered to be easy, quick and confident. Conclusions Computer-assisted visualization and interpretation of digital mammography images using a dedicated workstation can be performed with sufficiently high diagnostic accuracy.

To evaluate qualitatively and quantitatively the current procedures for radiologic delineation of the segmental and subsegmental anatomy of the liver.Vascular casts of 10 livers were examined with helical computed tomography (CT). Liver segmental and subsegmental anatomy were determined on the CT scans according to customary radiologic practice guidelines. CT anatomic findings were compared with authentic anatomic territories seen at anatomic examination. The differences were assessed quantitatively in five of the 10 livers.For the marginal (cranial and caudal) portions of the liver, an average (+/- 1 standard deviation) of 17.3% +/- 6.5 of the hepatic area visualized on axial CT scans was attributed to an incorrect subsegment. For the central zones (those adjacent to the right and left branches of the portal vein), this error amounted to 51.6% +/- 19.9. Expressed in absolute numbers, the error amounted to 40 mm on axial CT scans.The radiologic determination of portal venous territories within the liver must be revised. The indirect landmarks currently used are not reliable for proper delineation. Only procedures that account for the portal venous distribution pattern, including peripheral branches, will result in correct depiction of the complex and variable anatomic reality.

We give a complete answer to the question whether a double sequence that is generated by a one-dimensional linear cellular automaton, and whose states are integers modulo m , is k -automatic or not.

Background Late Gadolinium enhancement (LGE) cardiovascular magnetic resonance (CMR) imaging can be used to visualise regions of fibrosis and scarring in the left atrium (LA) myocardium. This can be important for treatment stratification of patients with atrial fibrillation (AF) and for assessment of treatment after radio frequency catheter ablation (RFCA). In this paper we present a standardised evaluation benchmarking framework for algorithms segmenting fibrosis and scar from LGE CMR images. The algorithms reported are the response to an open challenge that was put to the medical imaging community through an ISBI (IEEE International Symposium on Biomedical Imaging) workshop. Methods The image database consisted of 60 multicenter, multivendor LGE CMR image datasets from patients with AF, with 30 images taken before and 30 after RFCA for the treatment of AF. A reference standard for scar and fibrosis was established by merging manual segmentations from three observers. Furthermore, scar was also quantified using 2, 3 and 4 standard deviations (SD) and full-width-at-half-maximum (FWHM) methods. Seven institutions responded to the challenge: Imperial College (IC), Mevis Fraunhofer (MV), Sunnybrook Health Sciences (SY), Harvard/Boston University (HB), Yale School of Medicine (YL), King’s College London (KCL) and Utah CARMA (UTA, UTB). There were 8 different algorithms evaluated in this study. Results Some algorithms were able to perform significantly better than SD and FWHM methods in both pre- and post-ablation imaging. Segmentation in pre-ablation images was challenging and good correlation with the reference standard was found in post-ablation images. Overlap scores (out of 100) with the reference standard were as follows: Pre: IC = 37, MV = 22, SY = 17, YL = 48, KCL = 30, UTA = 42, UTB = 45; Post: IC = 76, MV = 85, SY = 73, HB = 76, YL = 84, KCL = 78, UTA = 78, UTB = 72. Conclusions The study concludes that currently no algorithm is deemed clearly better than others. There is scope for further algorithmic developments in LA fibrosis and scar quantification from LGE CMR images. Benchmarking of future scar segmentation algorithms is thus important. The proposed benchmarking framework is made available as open-source and new participants can evaluate their algorithms via a web-based interface.

We address the question whether double sequences produced by one-dimensional linear cellular automata can also be generated by finite automata. A complete solution for binomial coefficients and Lucas′ numbers is given and some partial results for the general case are presented.

In this paper we present a benchmarking framework for the validation of cardiac motion analysis algorithms. The reported methods are the response to an open challenge that was issued to the medical imaging community through a MICCAI workshop. The database included magnetic resonance (MR) and 3D ultrasound (3DUS) datasets from a dynamic phantom and 15 healthy volunteers. Participants processed 3D tagged MR datasets (3DTAG), cine steady state free precession MR datasets (SSFP) and 3DUS datasets, amounting to 1158 image volumes. Ground-truth for motion tracking was based on 12 landmarks (4 walls at 3 ventricular levels). They were manually tracked by two observers in the 3DTAG data over the whole cardiac cycle, using an in-house application with 4D visualization capabilities. The median of the inter-observer variability was computed for the phantom dataset (0.77 mm) and for the volunteer datasets (0.84 mm). The ground-truth was registered to 3DUS coordinates using a point based similarity transform. Four institutions responded to the challenge by providing motion estimates for the data: Fraunhofer MEVIS (MEVIS), Bremen, Germany; Imperial College London - University College London (IUCL), UK; Universitat Pompeu Fabra (UPF), Barcelona, Spain; Inria-Asclepios project (INRIA), France. Details on the implementation and evaluation of the four methodologies are presented in this manuscript. The manually tracked landmarks were used to evaluate tracking accuracy of all methodologies. For 3DTAG, median values were computed over all time frames for the phantom dataset (MEVIS = 1.20 mm, IUCL = 0.73 mm, UPF = 1.10 mm, INRIA = 1.09 mm) and for the volunteer datasets (MEVIS = 1.33 mm, IUCL = 1.52 mm, UPF = 1.09 mm, INRIA = 1.32 mm). For 3DUS, median values were computed at end diastole and end systole for the phantom dataset (MEVIS = 4.40 mm, UPF = 3.48 mm, INRIA = 4.78 mm) and for the volunteer datasets (MEVIS = 3.51 mm, UPF = 3.71 mm, INRIA = 4.07 mm). For SSFP, median values were computed at end diastole and end systole for the phantom dataset(UPF = 6.18 mm, INRIA = 3.93 mm) and for the volunteer datasets (UPF = 3.09 mm, INRIA = 4.78 mm). Finally, strain curves were generated and qualitatively compared. Good agreement was found between the different modalities and methodologies, except for radial strain that showed a high variability in cases of lower image quality.

Since its introduction to hepatobiliary surgery, three-dimensional (3D) imaging has assumed a growing importance for the visualization of abdominal diseases. The main clinical applications include preoperative simulation for oncologic liver resection [1, 2], and living-donor liver transplantation [3, 4]. The advantages of 3D imaging are the exact visualization of vessels in areas with complex and variable vascular anatomy, determining possible resection margins, and predicting operative risks. Although hepatectomy is increasingly carried out, it is still one of the most difficult operative procedures because of the anatomical complexity and hepatic vascular variability [5]. Moreover, patients with hilar cholangiocarcinoma often have obstructive jaundice, and the impaired hepatic function restricts the volume of liver resection. In addition, a positive resection margin should be avoided in order to achieve a potential cure of the disease. Thus, exact preoperative information on the detailed topography and precise liver resection volume should be obtained for curative and harmless hepatectomy. Concerning hilar cholangiocarcinoma, a successful management requires the following three steps: accurate preoperative estimation of both the tumor extent and anatomical variations, appropriate planning and simulation of the operative procedures, and implementing the planned procedures securely [6–8].

Die SPIEGEL-Serie „Der Kult um das Chaos” [1] hat der Chaosforschung eine zweifelhafte Publicity verschafft. Zwar wurde in den drei Folgen eine Fulle von Material prasentiert, die aufwendige Recherche ist erkennbar, auch kritische Punkte wurden unbekummert angesprochen, aber dennoch entwertet sich die Darstellung durch ihren Grundtenor: Chaos gebe es uberhaupt nicht, es sei nur ein Artefakt des Computers. Der Versuch, diese These durch die Gegenuberstellung zweier Rechnungen zum Dreikorper-problem konkret zu verifizieren, fand inzwischen ein gerichtliches Nachspiel, wobei die verfugte Gegendarstellung im SPIEGEL jedoch keine inhaltliche Richtigstellung war. Die Physikalischen Blatter empfinden sich als das geeignete Forum, den angegriffenen Fachkollegen eine Klarstellung zu ermoglichen, nicht zuletzt auch deshalb, weil der SPIEGEL-Beitrag auch unter Physikern — Nicht-Chaosspezialisten — Verunsicherung hervorgerufen hat. — Einem (ungeschriebenen) Fairnesgebot im Fall einer personlichen Kontroverse folgend, hat die Redaktion beide Seiten zu Wort kommen lassen und ihnen die Texte vor Veroffentlichung zur Kenntnis gegeben.

1- or 2-directional MRI blood flow mapping sequences are an integral part of standard MR protocols for diagnosis and therapy control in heart diseases. Recent progress in rapid MRI has made it possible to acquire volumetric, 3-directional cine images in reasonable scan time. In addition to flow and velocity measurements relative to arbitrarily oriented image planes, the analysis of 3-dimensional trajectories enables the visualization of flow patterns, local features of flow trajectories or possible paths into specific regions. The anatomical and functional information allows for advanced hemodynamic analysis in different application areas like stroke risk assessment, congenital and acquired heart disease, aneurysms or abdominal collaterals and cranial blood flow. The complexity of the 4D MRI flow datasets and the flow related image analysis tasks makes the development of fast comprehensive data exploration software for advanced flow analysis a challenging task. Most existing tools address only individual aspects of the analysis pipeline such as pre-processing, quantification or visualization, or are difficult to use for clinicians. The goal of the presented work is to provide a software solution that supports the whole image analysis pipeline and enables data exploration with fast intuitive interaction and visualization methods. The implemented methods facilitate the segmentation and inspection of different vascular systems. Arbitrary 2- or 3-dimensional regions for quantitative analysis and particle tracing can be defined interactively. Synchronized views of animated 3D path lines, 2D velocity or flow overlays and flow curves offer a detailed insight into local hemodynamics. The application of the analysis pipeline is shown for 6 cases from clinical practice, illustrating the usefulness for different clinical questions. Initial user tests show that the software is intuitive to learn and even inexperienced users achieve good results within reasonable processing times.

Manual delineations by experts are often used as reference standards for validating segmentation algorithms, although it is well known that they always show some degree of variability. Our goal is to estimate the effects of using a limited number of expert segmentations. Given ten manual delineations of 13 liver tumors, we analyzed the volume error made by randomly selecting subsets of the ten segmentations compared to the complete set. We found that when using just one segmentation the expected error was 17% with a maximum of 35%. This means that it is questionable whether a comparison with a single reference allows a reliable validation. When three segmentations are chosen, the error is halved, so this might be a reasonable compromise between accuracy and viability of evaluation studies.

Wenn es darum geht, die Sicherheit von Patienten in der klinischen Praxis zu erhöhen und Risiken und Schädigungen, die beispielsweise durch Operationen entstehen können, zu minimieren, sind Computerunterstützung und digitale medizinische Bildgebung Schlüsseltechnologien: Modellbasierte Planungswerkzeuge ermöglichen es, Wissen über biophysikalische Zusammenhänge und medizinische Erfahrung mit klinische Daten reproduzierbar zu einem patientenindividuellen Abbild zusammenzuführen. Sind gute und erfahrene Operateure in der Lage, auch in komplexen Situationen die vorliegenden z. T. unvollständigen Informationen zielführend zu interpretieren, so fehlt weniger erfahrenen Ärzten dieses Wissen. Mithilfe der modellbasierten Analyse- und Planungswerkzeuge können jedoch auch weniger erfahrene Chirurgen sicherer arbeiten: Die Auswirkungen unterschiedlicher therapeutischer Strategien können im Vorfeld des Eingriffs quantitativ gegeneinander abgewogen werden, sodass Ärzte die Risiken eines Eingriffs effektiv bewerten und eine erhöhte Sicherheit erhalten, Risiken, die nicht in Kauf genommen werden dürfen, zu vermeiden. Für die Umsetzung werden funktionale und anatomische Informationen kombiniert und sind für die bildgeführte Chirurgie verfügbar. Modellanalysen helfen zudem, die vorhandene Datenkomplexität auf wesentliche kritische Informationen zu reduzieren, um so Orientierungshilfen zur realisieren, die den in der intraoperativen Situation eingeschränkten kognitiven und interaktiven Möglichkeiten gerecht werden.

Since the discovery of the X-ray radiation by Wilhelm Conrad Roentgen in 1895, the field of medical imaging has developed into a huge scientific discipline. The analysis of patient data acquired by current image modalities, such as computerized tomography (CT), magnetic resonance tomography (MRT), positron emission tomography (PET), or ultrasound (US), offers previously unattained opportunities for diagnosis, therapy planning, and therapy assessment. Medical image processing is essential to leverage this increasing amount of data and to explore and present the contained information in a way suitable for the specific medical task. In this tutorial, we will approach the analysis and visualization of medical image data in an explorative manner. In particular, we will visually construct the image processing algorithms using the popular graphical data-flow builder MeVisLab, which is available as a free download for noncommercial research. We felt that it could be more interesting for the reader to see and explore examples of medical image processing that go beyond simple image enhancements. The part of exploration, to inspect medical image data and experiment with image-processing pipelines, requires software that encourages this kind of visual exploration.

Phase-Contrast (PC) MRI utilizes signal phase shifts resulting from moving spins to measure tissue motion and blood flow. Time-resolved 4D vector fields representing the motion or flow can be derived from the acquired PC MRI images. In cardiovascular PC MRI applications, visualization techniques such as vector glyphs, streamlines, and particle traces are commonly employed for depicting the blood flow. Whereas these techniques indeed provide useful diagnostic information, uncertainty due to noise in the PC-MRI measurements is ignored, which may lend the results a false sense of precision. In this work, the statistical properties of PC MRI flow measurements are investigated and a probabilistic flow tracking method based on sequential Monte Carlo sampling is devised to calculate flow uncertainty maps. The theoretical derivations are validated using simulated data and a number of real PC MRI data sets of the aorta and carotid arteries are used to demonstrate the flow uncert ainty mapping technique.

Background Recent advances in image-based computer assistance in the last ten years allow computerized preoperative simulations, giving a lot of advantages in the preoperative surgical planning of resections1. Preoperative simulation represents the prerequisite for navigated liver surgery. The aim of this study is to describe elementary technical aspects of a navigated approach to liver resections showing the advantages of navigation-system especially in the elderly.

CT scanning of the lungs is the standard procedure for preoperative evaluation of central lung tumors. The extent of the tumor and infiltration of central lung structures or lung segments are decisive parameters to clarify whether surgery is possible and the extent of resection. With computer-assisted methods for the segmentation of anatomical structures based on CT data (Fraunhofer MeVis, Bremen) an enhanced, three-dimensional selective visualization is now possible.From August 2007 through June 2009, 22 patients with central lung tumors were treated at the department of thoracic surgery, University of Schleswig-Holstein, campus Lübeck. There were 15 males and 7 females with a mean age of 60.2 years (range 41-74 years), 18 patients had a long history of smoking, while 4 patients had never smoked. Of the patients 20 had a primary lung carcinoma, 1 patient had local recurrent lung cancer after lobectomy and 1 patient had a central lung metastasis from a non-pulmonary primary carcinoma. A multi-slice detector computer tomogram (MSDCT) scan was performed in all cases. All data were three-dimensionally reconstructed and visualized using special computer-aided software (Fraunhofer MeVis, Bremen). Pulmonary lung function tests, computed postoperative lung volume, bronchoscopic findings, general condition of the patients and the three-dimensionally reconstructed CT data were used for an individual risk analysis and surgical planning.According to the risk analysis 14 out of the 22 patients were surgically treated, 7 patients were staged as functionally inoperable and 1 as technically inoperable. A pneumonectomy was performed in 5 cases, a lobectomy/bilobectomy in 4 cases, an extended lobectomy in 3 cases and 1 case each of a wedge resection and a sleeve resection. Of the 14 patients 2 were classified as stage Ia/b, 7 patients as stage IIa/b and 5 patients as stage IIIa. The median length of time spent in hospital was 8.5±33 days and the mortality rate was 0%. The three-dimensional visualization of the tumor and its anatomical relationship to central pulmonary vessels and the airway system was feasible in all cases. The three-dimensional reconstruction was confirmed in all cases by surgical exploration.Three-dimensional reconstruction of CT scan data is a new and promising method for preoperative presentation and risk analysis of central lung tumors. The three-dimensional visualization with anatomical reformatting and color-coded segmentation enables the surgeon to make a more precise strategic approach for central lung tumors.

Radiofrequency (RF) ablation is an image-guided minimally invasive therapy which destroys a tumor by locally inducing electrical energy into the malignant tissue through a radiofrequency applicator. Treatment success is essentially dependent on the accurate placement of the RF applicator. In the case of CT-guided RF ablation of liver tumors, a central problem during monitoring is the reduced quality and information content in the peri-interventional images compared to the images used for planning. Therefore, the question of how to effectively transf er information from the planning scan into the peri-interventional scan in order to support the interventionalist is of high interest. Key to such an enhancement of peri-interventional scans is an adequate registration of the pre- and peri-interventional image, which also needs to be fast since intervention duration is still a challenge. We present an approach for the fast and automatic registration of a high quality CT volume scan of the liver to a spiral CT scan of lower quality. Our method combines an approximate pre-registration to compensate large displacem ents and a rigid registratio n of a liver subvolume fo r further refinement. The method focuses on the position of the tumor to be ablated and the corresponding access path . Thereby, it achieves both fast and precise results in the region of interest. A preliminary evaluation, on 37 data sets from 20 different patients, shows that the registration is performed within a maximum of 18 seconds, while obtaining high accuracy in the relevant region of the liver comprising tu mor and the planned access path. Keywords: Image-guided Therapy, In tervention, Registration, Radiofrequency Ablation, Targeting Support, Liver

Purpose: To evaluate feasibility and effectivity of software-assisted monitoring of MR guided Radiofrequencyablation (RFA) of malignant liver tumors. Materials and Methods: MR-guided RFA of n=10 primary and n=18 secondary malignant liver tumors was performed for n=20 patients in an interventional MR unit (Magnetom Espree 1.5T, Siemens Medical Solutions, Forchheim). The tumor size was between 10 and 60 mm. Monopolar and bipolar internally-cooled MR compatible RF electrodes were used (Valleylab,Cool-tip, Burlington, MA and Celon AG, ProSurge, Teltow). Therapy monitoring was assisted by a software comparing tumor and tumor ablation state until complete tumor destruction within a given safety margin of 1 cm (MeVisSafir, Fraunhofer Mevis, Bremen). Therefore MR data were immediately transferred via DICOM to a MeVis workstation. Results: MRguided RF ablation by using MeVisSafir was technically successful in 20/20 (100%) patients as assessed at the end of each session. Complete coagulation was intended in 27/28 tumors by using the software-assistent. To achieve complete coagulation 1/28 tumors required a second session. MeVisSafir was able to monitor the extent of coagulation necrosis and to determine the safety margin. Furthermore, it was supportive in guiding overlapping ablations for complete tumor coagulation for larger livertumors (>30mm). Conclusions: Software-assisted MR-guided RFA of liver malignancies is feasible and effective, especially for the therapy monitoring of larger malignant liver tumors.

Deformable motion correction has become a fundamental image processing task for the quantitative analysis of dynamic contrast-enhanced breast magnetic-resonance imaging (MRI). However, although various non-linear image registration techniques are available, objective evaluation remains challenging. In this paper, we propose a biomechanical model of the breast based on a mass-spring system and an internal tetrahedron structure. We demonstrate how this model can be applied to clinical datasets to generate plausible breast deformations for the evaluation. For this purpose, we integrate a thin-plate spline image transformation into the model. Furthermore, we show how the specific model can be used to quantitatively evaluate breast MRI motion correction, and present preliminary registration results achieved with the proposed method.

Computational support in intervention planning promises to support the subjective interpretation of data with reproducible measurements. Moreover, it is possible to develop and apply models that provide additional information which is not directly visible in the data. Beside the ability of patient individual adaptation, proper treatment of errors and uncertainty is of crucial importance to assure the clinical relevance of models for computer-assisted diagnosis and therapy. In the context of image based planning for liver surgery, a model for intrahepatic vascular structures is combined with individual, but in the degree of vascular details limited anatomical information from radiological images. As a result, the model allows for a dedicated risk analysis and preoperative planning of oncologic resections as well as for living donor liver transplantations. The clinical relevance of the method was approved in several evaluation studies of our medical partners and more than 3500 complex surgical cases have been analyzed since 2002.

Computational support in intervention planning promises to support the subjective interpretation of data with reproducible measurements. Moreover, it is possible to develop and apply models that provide additional information which is not directly visible in the data. Based on computertomography multi-slice images of the liver, the planning software developed by MeVis Research offers tools to evaluate different interventional strategies preoperatively. In identifying patient individual risks, an optimized interventional plan is developed. In radiofrequency ablation of liver tumors, the treatment success highly depends on an effective placement of the radiofrequency applicators into the tumor to achieve sufficient coagulative necrosis. Beside tumor size and shape, the cooling effects of surrounding vessels are taken into account for a numerical estimation of the accessible thermal destruction. Based on this information, an optimized positioning can be obtained. In case of the surgical resection, removing the tumor together with a safety margin from the liver, requires transsection of local vascular structures that are supplying or draining a dedicated liver region. The identification and quantitative assessment of these regions, which are functionally endangered, guides the preoperative evaluation of surgical strategies. Subsequently proper visualizations of the planning data help to identify critical structures, and allow for a better control of the intraoperative situation. The planning data are matched with images from intraoperative ultrasound, and the aligned data are displayed in the operating theatre on monitors, which are placed directly the table. Moreover, an intraoperative adaption of the surgical planning is addressed: In oncologic liver surgery, additional tumors that were not visible in the preoperative images are often found during the intervention. With such findings, the resection strategy must be updated or completely revised. The planning software allows for an automated adaption of the surgical planning. The aim is to provide surgeons with an efficient tool for the quantitative assessment of planning, which is integrated in the workflow of oncologic liver interventions. To provide a meaningful procedural support of the surgical workflow, the cognitive needs of the surgeons have to be taken into account.

We present methods for intraoperative visualization of vascular structures in liver surgery. The underlying concept combines conventional augmented reality approaches with illustrative rendering techniques. Our methods reduce the visual complexity of vascular structures, and accentuate spatial relations. The proposed visualization techniques are embedded in a clinical prototype application that has already been used in the operating room for preliminary evaluations. To verify the expressiveness of our illustration methods, we performed a user study with controlled lab conditions. The study revealed a clear advantage in distance assessment for the proposed illustrative approach in comparison to conventional rendering techniques.

Current magnetic resonance imaging (MRI) technology allows the determination of patient-individual coronary tree structure, detection of infarctions, and assessment of myocardial perfusion. Joint inspection of these three aspects yields valuable information for therapy planning, e.g., through classification of myocardium into healthy tissue, regions showing a reversible hypoperfusion, and infarction with additional information on the corresponding supplying artery. Standard imaging protocols normally provide image data with different orientations, resolutions and coverages for each of the three aspects, which makes a direct comparison of analysis results difficult. The purpose of this work is to develop methods for the alignment and combined analysis of these images. The proposed approach is applied to 21 datasets of healthy and diseased patients from the clinical routine. The evaluation shows that, despite limitations due to typical MRI artifacts, combined inspection is feasible and can yield clinically useful information.