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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.

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.

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.

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.

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].

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.

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.

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. 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.

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.

Background Although the consequences of partial venous outflow interruption have attracted only limited attention in liver surgery, maximal preservation of liver function after hepatic resection requires preservation of circulation in the remnant liver, especially hepatic vein drainage. Methods Data from 30 patients undergoing 3-dimensional imaging were analyzed to clarify the relationship between the area of the ventral right anterior section (RAS) and that drained by regional hepatic vein tributaries. The feasibility of our preliminary technique of right hemihepatectomy preserving the ventral RAS also was evaluated. Results The median estimated volume of the ventral RAS was 230 mL (range, 88–391). The average ratio of this estimated volume of the ventral RAS to total estimated liver volume was 18.0 ± 4.9%. The median volume of the territory served by middle hepatic vein (MHV) tributaries draining the ventral RAS, expressed as a percentage of the whole volume of the ventral RAS, was 82.5%. Findings in fusion images of portal and hepatic vein territories demonstrated an area of MHV tributaries comparable with the ventral RAS area in 73.3% of all cases. As for the results of right hemihepatectomy with the ventral RAS preserved, no tumor was exposed on transection surfaces, and no recurrence took place within the preserved ventral RAS of the remnant liver. Conclusion Procedures considering the importance of regional venous drainage offer the possibility of reducing the extent of surgery without loss of effectiveness.

In recent years the diagnosis of the coronary artery disease is supported by non-invasive imaging methods such as CT, MRI, PET or SPECT. Today, CT is the leading modality for morphology imaging of the heart. Moreover, iodine-based contrast agents enable a visualization of myocardial viability with CT. In this work, we present new software assistants, that enable a comprehensive result exploration of cause and effect of an ischemia from one imaging modality. Therefore, we adapted our current methods for the detection and segmentation of myocardial scars to CT data and compare the results with measurements from advanced coronary artery analysis. Results on several pig data demonstrate the ability to automatically detect infarctions and to relate them to the causative coronary arteries. Furthermore, preliminary results with two patient data sets illustrate that accurate patient-specific information can be achieved in addition to the standardized AHA 17-segment model.

A template tracking approach to the segmentation of small 3D vessel structures is presented. The main contributions are a general formulation of a vessel template function and a multiple hypotheses tracking framework that is shown to improve the tracking robustness. The methodology is demonstrated using CT angiography data of the liver to which a hybrid region growing and tracking segmentation is applied.

The diagnosis support in the field of coronary artery disease (CAD) is very complex due to the numerous symptoms and performed studies leading to the final diagnosis. CTA and MRI are on their way to replace invasive catheter angiography. Thus, there is a need for sophisticated software tools that present the different analysis results, and correlate the anatomical and dynamic image information. We introduce a new software assistant for the combined result visualization of CTA and MR images, in which a dedicated concept for the structured presentation of original data, segmentation results, and individual findings is realized. Therefore, we define a comprehensive class hierarchy and assign suitable interaction functions. User guidance is coupled as closely as possible with available data, supporting a straightforward workflow design. The analysis results are extracted from two previously developed software assistants, providing coronary artery analysis and measurements, function analysis as well as late enhancement data investigation. As an extension we introduce a finding concept directly relating suspicious positions to the underlying data. An affine registration of CT and MR data in combination with the AHA 17-segment model enables the coupling of local findings to positions in all data sets. Furthermore, sophisticated visualization in 2D and 3D and interactive bull's eye plots facilitate a correlation of coronary stenoses and physiology. The software has been evaluated on 20 patient data sets.

A major concern in adult-to-adult living donor liver transplantation is the selection of graft type; that is, is it is better to use the right lobe with or without the middle hepatic vein (MHV)? This choice has a considerable impact on donor safety, vascular reconstruction and graft function in the recipient. To facilitate making an appropriate choice, on the basis of a preliminary study (n = 17), we herein propose a graft selection algorithm using three parameters: graft-to-recipient body weight ratio (GRWR), percentage remnant liver volume (%RLV) and estimated congestion ratio (ECR). The algorithm was evaluated with 50 consecutive cases with respect to postoperative liver function of donors and recipients and survival of recipients. Postoperative recovery was comparable between the two groups (p = NS). The overall cumulative 18-month survival rate was 86.7% for the 'with MHV graft group', and 76.1% for the gwithout MHV graft grouph (p = NS). For 41 cases (82%), graft types were chosen according to the algorithm, whereas the remaining 9 cases (18%) needed detailed discussion of donor, recipient and operative factors. In conclusion, we constructed a graft selection algorithm based on congestion volume, which will contribute to objective graft-type selection in adult-to-adult LDLT.

The analysis of myocardial tissue with contrast-enhanced MR yields multiple parameters, which can be used to classify the examined tissue. Perfusion images are often distorted by motion, while late enhancement images are acquired with a different size and resolution. Therefore, it is common to reduce the analysis to a visual inspection, or to the examination of parameters related to the 17-segment-model proposed by the American Heart Association (AHA). As this simplification comes along with a considerable loss of information, our purpose is to provide methods for a more accurate analysis regarding topological and functional tissue features. In order to achieve this, we implemented registration methods for the motion correction of the perfusion sequence and the matching of the late enhancement information onto the perfusion image and vice versa. For the motion corrected perfusion sequence, vector images containing the voxel enhancement curves' semi-quantitative parameters are derived. The resulting vector images are combined with the late enhancement information and form the basis for the tissue examination. For the exploration of data we propose different modes: the inspection of the enhancement curves and parameter distribution in areas automatically segmented using the late enhancement information, the inspection of regions segmented in parameter space by user defined threshold intervals and the topological comparison of regions segmented with different settings. Results showed a more accurate detection of distorted regions in comparison to the AHA-model-based evaluation.

Background Complex, highly variable, anatomic relationships in the portal hilum complicate the surgical management at hilar cholangiocarcinoma. Preoperative three-dimensional (3D) imaging to stage the tumor and define anatomy may help in planning for curative resection. Methods Between 2003 and 2006, 20 consecutive patients with hilar cholangiocarcinoma underwent preoperative multidetector row computed tomography (MDCT) cholangiography; 3D images of the portal vein, hepatic artery, and bile ducts were created and viewed simultaneously. Longitudinal tumor extension was evaluated by direct cholangiography and 3D cholangiography, and contiguous spread by 2D computed tomography (CT). Of 20 patients, 15 underwent surgical resection. Liver resection was planned based on 3D imaging that allowed visualization of the relationship between the tumor and the umbilical portion of the left portal vein, or the bifurcation of the anterior and posterior branch of the right portal vein. Preoperative and operative findings were compared. Results All patients tolerated 3D CT without serious complication. The accuracy rates of longitudinal tumor extension, using the Bismuth-Corlette classification system, were 85% (11/13) and 87% (13/15) with direct cholangiography and 3D cholangiography, respectively. The sensitivity, specificity, and accuracy rates were 100%, 80%, and 87% for portal invasion and 75%, 91%, and 87% for hepatic arterial invasion. The number of bile duct orifices in the cut end of the hilar plate was estimated correctly in 13 of 15 patients. There were no operative deaths. Potentially curative resection was achieved in 14 of 15 patients. Conclusions 3D images provide accurate information about the relationship between hilar cholangiocarcinoma and adjacent vessels. This technique is a powerful new tool for improving the proportion of potentially curative resection.

We present real-time vascular visualization methods, which extend on illustrative rendering techniques to particularly accentuate spatial depth and to improve the perceptive separation of important vascular properties such as branching level and supply area. The resulting visualization can and has already been used for direct projection on a patient's organ in the operation theater where the varying absorption and reflection characteristics of the surface limit the use of color. The important contributions of our work are a GPU-based hatching algorithm for complex tubular structures that emphasizes shape and depth as well as GPU-accelerated shadow-like depth indicators, which enable reliable comparisons of depth distances in a static monoscopic 3D visualization. In addition, we verify the expressiveness of our illustration methods in a large, quantitative study with 160 subjects.

Objective: The oncologically safe application of thermal in-situ ablation techniques is limited by a lack of precise prediction of the resulting destruction. The aim of the current study was to validate a 3D planning system for in-situ ablation of liver tumors with regard to the simulation of the cooling effect of intrahepatic vessels in vivo. Methods: A liver CT scan was performed on domestic pigs. Subsequently, an applicator for laser-induced thermotherapy (LITT) was introduced near a large intrahepatic vessel and LITT was performed (28 W, 20 min). The liver was removed and the lesion was digitally measured. On the basis of the CT scan a segmentation of the liver and intrahepatic vessels was performed and a simulation of the thermal lesion was carried out. The real and the simulated lesion were compared with regard to size and shape. Results: 12 thermal lesions were induced in 8 animals. The mean deviation of the real to the idealized lesion was 27.3%. The volume of lesions invivo was 7.39 ± 1.79 cm3, that of calculated lesions was 7.41 ± 1.68 cm3. The morphometric analysis showed a spatial correlation of 76% between real and simulated lesions. Conclusions: (1) A 3D computer planning system was developed for predicting thermal lesions resulting from in-situ ablation. (2) This system enables a calculation of the cooling effect of intrahepatic vessels for the first time. (3) The planning system facilitates a safer application of in-situ ablation techniques.

In planning of adult to adult living donor liver transplantation the knowledge about the functional graft volume excluding the parenchyma with an impaired venous outflow from the total graft volume is crucial. Between December 2002 and April 2004 101 consecutive donors from two hospitals were evaluated within the research project “SIMPL”. To estimate the functional graft volume for a right lobe graft without the middle hepatic vein (MHV) the hepatic venous territories in the graft were calcu-lated. The median relative graft volumes were 64% (Standard Deviation (SD) 4.9%) in the Kyoto University Hospital and 61% (SD 5.8%) in the Lahey Clinic Medical Center. Of these volumes 25% (SD 9.6%) and 23% (SD 9.5%), respectively, were drained via MHV branches and are therefore at risk of venous congestion. Preoperative estimation of functional graft volume is possible in clinical routine. It allows for a better patient individual planning since different resection strategies can be evaluated and associated risks can be assessed.

Objective: The oncologically safe application of thermal in-situ ablation techniques is limited by a lack of precise prediction and online monitoring of the resulting destruction. Knowledge about intrahepatic vessel structure is important for therapy planning. The aim of the current study was to validate in-vivo an interdisciplinary developed 3D planning system for the in-situ ablation of liver tumors with regard to intrahepatic vessel segmentation. Methods: 10 domestic pigs were used (40 kg, endotracheal anaesthesia, cross-laparatomy). After surgical preparation of the extra-hepatic vessels, an angiographie catheter was implanted in the portal vein. A computed tomography (CT, Siemens Somatom l6, 1 mm slices, DICOM2 data acquisition) was performed an each pig. The scans were carried out using a peripheral venous contrast medium (CM) and a selective CM-CT via the implanted portal vein catheter. After removal of the liver, a corrosion cast with acrylic resin via the portal vein catheter was prepared in-situ. The image data was transferred to the planning system and the vessel segmentation was carried out. The validation was performed by comparing the corrosion cast and the computed segmentation. Results: A segment classification of the pig liver was established. Standard CTs allowed for segmentation of the portal vein branches down to 3rd degree subsegment vessels. The comparison between the patterns of the corrosion cast and the peripheral veins and selective segmentation showed complete correlation to the 1st degree subsegment vessels and a correlation of 97% to the 2nd degree subsegment vessels. Incorrect segmentations, i.e. assignment of adjacent vessel systems, or aborts of segmentation were not abserved. Conclusions: 1.) A 3D computer planning system was developed for predicting thermal lesions resulting from in-situ ablation. 2.) The algorithms for vessel segmentation resulted in a precise depiction of the in-vivo intrahepatic vessel structure. 3.) This planning system facilitates the calculated use of thermal in-situ ablation techniques.

For liver surgical planning, the structure and morphology of the hepatic vessels and their relationship to tumors are of major interest. To achieve a fast and robust assistance with optimal quantitative and visual information, we present methods for a geometrical and structural analysis of vessel systems. Starting from the raw image data a sequence of image processing steps has to be carried out until a three-dimensional representation of the relevant anatomic and pathologic structures is generated. Based on computed tomography (CT) scans, the following steps are performed. 1) The volume data is preprocessed and the vessels are segmented. 2) The skeleton of the vessels is determined and transformed into a graph enabling a geometrical and structural shape analysis. Using this information the different intrahepatic vessel systems are identified automatically. 3) Based on the structural analysis of the branches of the portal vein, their vascular territories are approximated with different methods. These methods are compared and validated anatomically by means of corrosion casts of human livers. 4) Vessels are visualized with graphics primitives fitted to the skeleton to provide smooth visualizations without aliasing artifacts. The image analysis techniques have been evaluated in the clinical environment and have been used in more than 170 cases so far to plan interventions and transplantations.

HepaVision2, a user friendly software application for preoperative planning based on CT images in liver surgery is presented. It is intended for both, evaluation of potential donors in living-related liver transplantation and planning of oncologic resections. The planning takes into account the patient’s individual anatomy allowing for fully automatic calculation of individual resection proposals including volumetric analysis. The results are visualized in 3D, thus allowing the surgeon to choose the optimal strategy for each patient. The software was tested in over 50 cases by our clinical partners and our institution. Average time needed per case is below one hour, therefore allowing the use of the software application in clinical routine.