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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.

Mithilfe neuer Softwaresysteme können sämtliche intrahepatischen vaskulären und kanalikulären Strukturen segmentiert, dreidimensional rekonstruiert sowie das ihnen zugehörige Territorium visualisiert und quantifiziert werden. Dies ermöglicht es, Leberoperationen unter Berücksichtigung der patientenindividuellen Leberanatomie virtuell durchzuführen und für jede frei wählbare Schnittführung sowohl das verbleibende Volumen als auch den Anteil des dabei devaskularisierten Lebergewebes zu berechnen. Somit kann die Notwendigkeit für intrahepatische Gefäßrekonstruktionen oder Erweiterungen des Resektionsausmaßes zur Vermeidung devaskularisierter Leberareale auf der Basis einer präoperativen vaskulären Risikoanalyse mit Volumenberechnung ermittelt werden. Diese Zusatzinformation ist aufgrund der großen Gefäßvariabilität im rechten Leberlappen, insbesondere vor erweiterten Linksresektionen sowie auch vor Rezidivresektionen wegen des durch die Voroperation oftmals erheblich veränderten intrahepatischen Gefäßsystems wertvoll. Für die Zukunft sind weitere Verbesserungen durch die Entwicklung von Navigationssystemen zur sicheren intraoperativen Steuerung und zuverlässigen Umsetzung der präoperativen Planungsdaten zu erwarten.

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.

The combination of modern scanner technology with advanced image postprocessing allows for high-fidelity three-dimensional imaging of pertinent patient anatomy. Currently available solutions provide not only precise qualitative but also advanced quantitative imaging, resulting in precise estimates of whole or partial organ or tumor volumes. Simulations of open surgical or percutaneous interventions are an important application of advanced image analysis. Image postprocessing may be performed locally or remotely using readily available Internet connectivity. Results can be offered to the treating physician in a very realistic format and can be made available in an interactive fashion, such as in the operating room. Clinically appropriate use of this powerful technology can alter the surgical approach to individual patients’ problems, help with preoperative feasibility and risk assessment, and ultimately may result in shorter and safer procedures.

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: Computed tomography has become the preferred method in detecting liver carcinomas. The introduction of spiral CT added volumetric assessment of intrahepatic tumors, which was unattainable in the clinical routine with incremental CT due to complex planimetric revisions and excessive computing time. In an ongoing clinical study, a new software tool was tested for the automatic detection of tumor volume and the time needed for this procedure. Materials and Methods: We analyzed patients suffering from hepatocellular carcinoma (HCC). All patients underwent treatment with repeated transcatheter chemoembolization of the hepatic arteria. The volumes of the HCC lesions detected in CT were measured with the new software tool in HepaVison (MeVis, Germany). The results were compared with manual planimetric calculation of the volume performed by three independent radiologists. Results: Our first results in 16 patients show a correlation between the automatically and the manually calculated volumes (up to a difference of 2 ml) of 96.8%. While the manual method of analyzing the volume of a lesion requires 2.5 minutes on average, the automatic method merely requires about 30 seconds of user interaction time. Conclusion: These preliminary results show a good correlation between automatic and manual calculations of the tumor volume. The new software tool requires less time for accurate determination of the tumor volume and can be applied in the daily clinical routine.

Enhanced Precision in Surgical Treatment Planning of Hilar Bile Duct Cancer: Initial Experiences with Computer-Assisted 3D CT Imaging Extended surgical resection until now provides

Background: The implementation of intraoperative navigation in liver surgery is handicapped by intraoperative organ shift, tissue deformation, the absence of external landmarks, and anatomical differences in the vascular tree. To investigate the impact of surgical manipulation on the liver surface and intrahepatic structures, we conducted a prospective clinical trial. Methods: Eleven consecutive patients [4 female and 7 male, median age=67years (range=54-80)] with malignant liver disease [colorectal metastasis (n=9) and hepatocellular cancer (n=2)] underwent hepatic resection. Pre- and intraoperatively, all patients were studied by CT-based 3D imaging and assessed for the potential value of computer-assisted planning. The degree of liver deformation was demonstrated by comparing pre- and intraoperative imaging. Results: Intraoperative CT imaging was successful in all patients. We found significant deformation of the liver. The deformation of the segmental structures is reflected by the observed variation of the displacements. There is no rigid alignment of the pre- and intraoperative organ positions due to overall deflection of the liver. Locally, a rigid alignment of the anatomical structure can be achieved with less than 0.5cm discrepancy relative to a segmental unit of the liver. Changes in total liver volume range from −13 to +24%, with an average absolute difference of 7%. Conclusions: These findings are fundamental for further development and optimization of intraoperative navigation in liver surgery. In particular, these data will play an important role in developing automation of intraoperative continuous registration. This automation compensates for liver shift during surgery and permits real-time 3D visualization of navigation imaging

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.

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.

The ability to acquire and store radiological images digitally has made this data available to mathematical and scientific methods. With the step from subjective interpretation to reproducible measurements and knowledge, it is also possible to develop and apply models that give additional information which is not directly visible in the data. In this context, it is important to know the characteristics and limitations of each model. Four characteristics assure the clinical relevance of models for computer-assisted diagnosis and therapy: ability of patient individual adaptation, treatment of errors and uncertainty, dynamic behavior, and in-depth evaluation. We demonstrate the development and clinical application of a model in the context of liver surgery. Here, 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 2900 complex surgical cases have been analyzed since 2002.

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.

t ( 4 n t c R ( 74-year-old man presented with a solitary colorectal metasasis in the cranial part of the liver involving segments IVa/ Vb/VIII and the middle hepatic vein (MHV). CT (A-H) howed a small right hepatic vein (RHV) in the presence of an nferior right hepatic vein (G, H, red arrows). Left-lateral segents were only 12% of total liver volume, excluding right risectionectomy. The CT scan showed that tumor resection as possible by an extended left hepatectomy with preserva

Hypothesis Currently, standard planning for hepatic resection is based on the schematic description of the functional anatomy of the liver according to Couinaud, and on the evaluation of 2-dimensional computed tomographic imaging of the liver. Recent developments in image-based computer assistance allow patients’ individual functional liver anatomy to be computed from mathematical analysis of standard multidetector computed tomographic scans. An intended resection can be performed virtually under realistic anatomic conditions, and the influence of different resection planes on blood supply and drainage within the remaining liver parenchyma can be calculated by a computer-assisted risk analysis. We evaluated the impact of computer-assisted risk analysis on operation planning for major hepatectomies, in particular on extent of resection or need for vascular reconstruction. Design Prospective cohort study. Setting Academic tertiary care referral center. Patients Twenty-five consecutive patients admitted to the hospital for major hepatectomy, of whom 4 had tumors deemed unresectable by both methods. Interventions Two-dimensional computed tomography was used to calculate the volume of the future liver remnant with the intended resection line manually determined, and then the volume of the future liver remnant was calculated again by computer-assisted risk analysis as the remaining liver volume not being devascularized but having both portal venous blood supply and hepatic venous drainage. Main Outcome Measures The difference between the remaining functional liver volumes calculated by the 2 methods. Results The deviation between liver volumes determined by 2-dimensional computed tomography and by computer-assisted risk analysis was less than 20% in 14 of 21 patients, between 20% and 30% in 3, between 30% and 40% in 2, and 41% and 43% in 1 patient each. The most extensive deviations were found in extended left hepatectomy or when left hepatectomy was combined with additional wedge resection in the right lobe. In 7 cases, all with a deviation greater than 20%, the results of computer-assisted risk analysis led to a change of operation planning with regard to the extent of resection (n = 3) or the need for vascular reconstruction (n = 4), although in 1 of these cases resection was not performed because of peritoneal carcinomatosis. Conclusions Image-based computer assistance allows for areas at risk for devascularization or venous congestion to be identified and precisely calculated before resection. In selected cases with small liver remnants, operation planning may be improved substantially by preoperative computer-assisted risk analysis.

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.

Introduction For living donor liver transplantation (LDLT) accurate diagnostic workup is essential. Multiple imaging approaches are currently used. Problems arise in the assessment of vascular and bile duct anatomy, liver graft volume, and vascular territories involved. A 3D visualization system that improves anatomic assessment, allows interactive surgery planning, and acts as an intraoperative guide with enhanced precision is required. Refinements in computed tomography (CT) technology with the introduction of multidetector-row CT scanners and implementation of mathematical methods on computerized digital data has enabled CT-based 3D visualizations. Materials and Methods Sixteen LDLT candidates and three LDLT recipients were assessed by multislice CT examination. Image processing of the digital raw data for 3D visualization included segmentation and calculation of center lines. A hierarchical mathematical model representing the vascular and biliary tree was created. This allowed calculation of individual vascular territories. Results 3D CT-based visualization in LDLT facilitates diagnostic workup with high accuracy for analyses of vascular and bile duct variants, volumetry, and assessement of the optimal surgical splitting line of the living donor liver. Resultant areas of either arterial devascularization or venous congestion can be displayed and quantified preoperatively. The diagnostic method is of major impact on patient selection and directly influences intraoperative surgical guidance. The currently practiced “multiple imaging approach” approach, especially with regard to invasive diagnostics, can be avoided in the future.

A quantitative analysis of brain tumors is an important factor that can have direct impact on a patient’s prognosis and treatment. In order to achieve clinical relevance, reproducibility and especially accuracy of a proposed method have to be tested. We propose a framework for the generation of realistic digital phantoms of brain tumors of known volumes and their incorporation into an MR dataset of a healthy volunteer. Deformations that occur due to tumor growth inside the brain are simulated by means of a biomechanical model. Furthermore, a model for the amount of edema at each voxel is included as well as a simulation of contrast enhancement, which provides us with an additional characterization of the tumor. A “ground truth” is generally not available for brain tumors. Our proposed framework provides a flexible tool to generate representative datasets with known ground truth, which is essential for the validation and comparison of current and new quantitative approaches. Experiments are carried out using a semi-automated volumetry approach for a set of generated tumor datasets.

A quantitative analysis of small structures such as focal lesions in patients suffering from multiple sclerosis (MS) is an important issue in both diagnosis and therapy monitoring. In order to reach clinical relevance, the reproducibility and especially the accuracy of a proposed method has to be validated. We propose a framework for the generation of realistic digital phantoms of MS lesions of known volumes and their incorporation into an MR dataset of a healthy volunteer. Due to the absence of a “ground truth” for lesions in general and MS lesions in particular, phantom data are a commonly used validation method for quantitative image analysis methods. However, currently available lesion phantoms suffer from the fact that the embedding structures are only simplifications of the real organs. We generated 54 datasets from a multispectral MR scan with incorporated MS lesion phantoms. The lesion phantoms were created using various shapes (3), sizes (6) and orientations (3). Since the common gold standard in clinical lesion volumetry is based on manual volume tracing, an evaluation is carried out from both a manual analysis of three human experts and a semi-automated approach based on regional histogram analysis. Additionally, an intra-observer study is performed. Our results clearly demonstrate the importance of an improved gold standard in lesion volumetry beyond manual tracing and voxel counting.

VICORA was founded in November 2000 as a non-profit institute by six major radiological centers, MeVis, and the two industrial partners Siemens Medical Solutions and MeVis Technology. The mission of VICORA is to develop algorithms and applications for computer assistance in clinical radiology, to evaluate the applications in a clinical environment and to establish them in clinical routine. Initially, VICORA focuses on the development of applications in the areas of vessel analysis, dynamic MRI, and preoperative planning.

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.

Rationale and objectives Quantitative analysis of such small structures as focal lesions in patients with multiple sclerosis (MS) is an important issue in both diagnosis and therapy monitoring. To reach clinical relevance, the reproducibility and accuracy of a proposed method have to be validated. We propose a framework for the generation of realistic digital phantoms of MS lesions of known volumes and their incorporation into a magnetic resonance (MR) data set of a healthy volunteer. Materials and methods We generated 54 data sets from a multispectral brain scan of a healthy volunteer with incorporated MS lesion phantoms. Lesion phantoms were created using different shapes (three), sizes (six), and orientations (three). An evaluation is carried out from a manual analysis of three human experts and two different semiautomatic approaches, with and without explicit modeling of partial volume effects (PVEs). Results Intraobserver and interobserver studies were performed for the phantom data sets. All experts overestimated the true lesion volume for any phantom data set (median overestimation between 42.9% and 63.2%). Relative error and variability increased with decreasing lesion size. Similar results were obtained for the semiautomatic approach without PVE modeling. Only the approach with explicit PVE modeling was capable of generating accurate volumetric results with low systematic error. Conclusion The proposed framework based on realistic lesion phantoms incorporated into an MR scan allows for quantitative assessment of the accuracy of manual and automated lesion volumetry. Results clearly show the importance of an improved gold standard in lesion volumetry beyond voxel counting.