Showing papers by "Andrea Schenk published in 2008"

Influence of intrahepatic vessels on volume and shape of percutaneous thermal ablation zones: in vivo evaluation in a porcine model.

Abstract: Objectives Aim of the study was to evaluate the precise influence of different intrahepatic vessels, vessel sizes, and distances from the applicator on volume and shape of hepatic laser ablation zones in an in vivo porcine model. Materials and methods The study was approved by the institutional animal care and use committee. Eighteen computed tomography-guided Nd:YAG laser ablations were performed in the livers of 10 pigs at varying distances from hepatic veins and portal fields. After hepatectomy the livers were cut into 2-mm slices perpendicular to the laser applicator axes. For each ablation zone the maximum achievable (ideal) volume, the segmented (real) volume, the maximum radius, and the radius at the position of adjacent hepatic vessels were determined. The shapes of the ablation zones were evaluated qualitatively. Comparative statistics using the unpaired t test and a multiple linear regression analysis were performed. Results Ideal and real ablation zone volumes differed by 27.3% (8.6 +/- 1.5 mL vs. 6.4 +/- 1.1 mL; P 0.05). When influencing, all hepatic veins showed a focal indentation whereas portal fields always showed broad flattening of the ablation zone. Conclusions Portal fields lead to more heat sink than hepatic veins. The effects decreased with the distance between vessel and applicator tip, but less so for portal fields. The 2 vessel types induced considerably different shape alterations of the ablation zones. These results were not dependent on vessel size. This should be considered in the planning of thermal tumor ablations.

Recovery of liver perfusion after focal outflow obstruction and liver resection.

Abstract: Background. Live liver donation requires extended liver resection in the donor with transection of the middle hepatic vein. This leads to focal outflow obstruction in the remnant liver or the partial graft. This study was designed to characterize the pathophysiological correlate of focal outflow obstruction in a small-for-size liver and its course of recovery in a rat model. Methods. Ligation of the right median hepatic vein was combined with 50% hepatectomy. Microcirculation was visualized by orthogonal polarization spectroscopy after each operative step and before killing on days 1, 2, and 7. Histologic evaluation included morphological assessment, immunohistochemical determination of proliferation using BrdU, and laminin and von Willebrand factor expression, which both indicate vascularization of sinusoids. Results. After ligation of the right median hepatic vein, congestion was visible and no sinusoidal blood flow was detected in the obstruction zone. By day 1 confluent centrilobular necrosis developed. Sinusoidal perfusion in the obstruction zone recovered partially. Many dilated vascularized sinusoidal canals connecting the obstruction zone with the normal zone were visible. Proliferative activity in the obstruction zone was markedly reduced compared with the normal zone. By day 7, liver parenchyma in the obstruction zone looked normal as did sinusoidal perfusion. In the border zone, few dilated vascular canals were apparent. Conclusion. Confluent centrilobular necrosis in the early postoperative phase, resulting from focal outflow obstruction, may be crucial for the development of a small-for-size syndrome. The exclusion of the outflow-obstructed zone from the functional liver mass during preoperative radiological risk assessment seems to be the logical consequence. Recovery of focal outflow obstruction occurs spontaneously by means of dilated sinusoids in the border zone, forming vascularized sinusoidal canals, which could serve as intrahepatic anastomosis.

Clinical relevance of model based computer-assisted diagnosis and therapy

Abstract: 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

Portal vein segmentation of a 3D-planning system for liver surgery--in vivo evaluation in a porcine model.

Abstract: Computer systems allow the planning of complex liver operations. The segmentation of intrahepatic vessels builds the basis for the calculation of liver segments and resection proposals. For surgical use, it is essential to know the capabilities and limitations of the segmentation. The aim of this study was to determine the sensitivity and precision of the portal vein segmentation of a computer planning system for liver surgery in vivo. Segmentations were performed with the software system HepaVision on computed tomography (CT) scan data of domestic pigs. An in situ corrosion cast of the portal vein served as the gold standard. The segmentation results of the portal vein and the corrosion cast were compared with regard to sensitivity, precision, and amount of short-circuit segmentations. The methodology demonstrated high resolution ex situ. The in vivo sensitivity of the portal vein segmentation was 100% for vessels of more than 5 mm in diameter and 82% for vessels of 3–4 mm. All segment branches were detected as well as 84% of the first subsegment branches with a diameter of more than 3 mm. The precision of the system was 100% for segment branches and 89% for the first subsegment vessels. The amount of internal short-circuit segmentations was less than 3.0%. No external short-circuits were found. The system has a high precision and sensitivity under clinical conditions. The segmentation is suitable for portal vein branches of the first and second order and for vessels of ≥3 mm in diameter.

Hepatic Hilar and Sectorial Vascular and Biliary Anatomy in Right Graft Adult Live Liver Donor Transplantation

Abstract: Introduction The aim of this study was to analyze vascular and biliary variants at the hilar and sectorial level in right graft adult living donor liver transplantation. Methods From January 2003 to June 2007, 139 consecutive live liver donors underwent three-dimensional computed tomography (3-D CT) reconstructions and virtual 3-D liver partitioning. We evaluated the portal (PV), arterial (HA), and biliary (BD) anatomy. Results The hilar and sectorial biliary/vascular anatomy was predominantly normal (70%–85% and 67%–78%, respectively). BD and HA showed an equal incidence (30%) of hilar anomalies. BD and PV had a nearly identical incidence of sectorial abnormalities (64.7% and 66.2%, respectively). The most frequent “single” anomaly was seen centrally in HA (21%) and distally in BD (18%). A “double” anomaly involved BD/HA (7.2%) in the hilum, and HA/PV and BD/PV (6.5% each) sectorially. A “triple” anomaly involving all systems was found at the hilum in 1.4% of cases, and at the sectorial level in 9.4% of instances. Simultanous central and distal abnormalities were rare. In this study, 13.7% of all donor candidates showed normal hilar and sectorial anatomy involving all 3 systems. A simultaneous central and distal “triple” abnormality was not encountered. A combination of “triple” hilar anomaly with “triple” sectorial normality was observed in 2 cases (1.4%). A central “triple” normality associated with a distal “triple” abnormality occurred in 7 livers (5%). Conclusions Our data showed a variety of “horizontal” (hilar or sectorial) and “vertical” (hilar and sectorial) vascular and biliary branching patterns, providing comprehensive assistance for surgical decision-making prior to right graft hepatectomy.

A New Systematic Classification of Peripheral Anatomy of the Right Hepatic Duct: Experience From Adult Live Liver Donor Transplantation

Abstract: Objective The peripheral intrahepatic biliary anatomy, especially at the sectorial level on the right side, has not been adequately described. The purpose of our study was to systematically describe this complex anatomy in clinically applicable fashion. Patients and Methods We analyzed three-dimensional computed tomography (CT) imaging reconstructions of 139 potential living liver donors evaluated at our institution between January 2003 and June 2007. Results Eighty-nine (64%) donors had a normal right bile duct sectorial anatomy. In the other 50/139 (36%) cases, we observed abnormal sectorial branching patterns, with 45/50 abnormalities as trifurcations, whereas the remaining ones were quadrifurcations. In 22/50 (44%) abnormalities, a linear branching pattern (types B1/C1) and an early segmental origin off the right hepatic duct (types B3/C3) were present, a finding of particular danger when performing a right graft hepatectomy. In 2 cases, we noted a mixed type (B6/C6) of a rare complex anatomy. Conclusions Our proposed classification of the right sectorial bile duct system clearly displays the “area at risk” encountered when performing right graft adult live donor liver transplantation and tumor resections involving the right lobe of the liver.

Liver “Compliance”: A Previously Unrecognized Preoperative Predictor of Small-for-Size Syndrome in Adult Living Donor Liver Transplantation

Abstract: Background The purpose of this study was to investigate the effect of liver compliance on computed tomography (CT) volumetry and to determine its association with postoperative small-for-size syndrome (SFSS). Patients and methods Unenhanced, arterial, and venous phase CT images of 83 consecutive living liver donors who underwent graft hepatectomy for adult-to-adult living donor liver transplantation (ALDLT) were prospectively subjected to three-dimensional (3-D) CT liver volume calculations and virtual 3-D liver partitioning. Graft volume estimates based on 3-D volumetry, which subtracted intrahepatic vascular volume from the “smallest” (native) unenhanced and the “largest” (venous) CT phases, were subsequently compared with the intraoperative graft weights. Calculated (preoperative) graft volume–to–body weight ratios (GVBWR) and intraoperative measured graft weight–to–body weight ratios (GWBWR) were analyzed for postoperative SFSS. Results Significant differences in minimum versus maximum total liver volumes, graft volumes, and GVBWR calculations were observed among the largest (venous) and the smallest (unenhanced) CT phases. SFSS occurred in 6% (5/83) of recipients, with a mortality rate of 80% (4/5). In four cases with postoperative SFSS (n = 3 lethal, n = 1 reversible), we had transplanted a small-for-size graft (real GWBWR Conclusion The recognition and precise assessment of each individual's liver compliance displayed by the minimum and maximum GVBWR values is critical for the accurate prediction of functional liver mass and prevention of SFSS in ALDLT.

Automatic hepatocyte quantification from histological images: comparing pre-smoothing filters

Abstract: Quantity of hepatocytes in the liver can reveal a lot of information for medical researchers. In our project, it is needed for evaluation of the liver regeneration rate. In this paper, we present a processing pipeline for automatic counting of hepatocytes from images of histological sections. In particular, we propose to introduce a preprocessing step in form of image smoothing. We apply five different smoothing techniques, namely Gaussian smoothing, nonlinear Gaussian smoothing, median filtering, anisotropic diffusion, and minimum description length segmentation, and compare them to each other. The processing pipeline is completed by subsequent automatic thresholding using Otsu's method and hepatocyte detection using Hough transform. We compare the quantification results in terms of quality (sensitivity and specificity rates) against the manually specified ground truth. We discuss the results and limitations of the individual processing steps as well as of the overall automatic quantification approach.

Anatomical classification of the peripheral right hepatic duct: early identification of a preventable source of morbidity and mortality in adult live donor liver transplantation.

Abstract: Introduction The purpose of this study was to determine the impact of our classification on right graft adult live donor liver transplantation (ALDLT) outcomes. Methods Three-dimensional computed tomography (CT) reconstructions were used to classify the hilar and sectorial biliary anatomy of 71 consecutive live liver donors. Four possible clinical types were defined, based on the normal (N) or abnormal (A) features of the corresponding hilar/sectorial ducts: type I, N/N; type II, N/A; type III, A/N; and type IV, A/A. We subsequently performed an analysis of the operative outcomes based on the donor anatomy. Results Type I was encountered in 47.9% of cases, type II in 29.6%, type III in 19.7%, and type IV in 2.8%. The highest incidence of biliodigestive anastomoses was observed with type III (50%) and type IV (100%) variants. Type I was associated with the highest incidence of single anastomoses (single vs multiple, P = .001) and of single bile duct anastomoses (single vs multiple, P = .004). Type III was associated with more multi-duct reconstructions compared with types I and II (P = .002 and P = .05, respectively). There were no significant differences in early (P = .08) or late (P = .33) biliary complications, or deaths due to a biliary etiology (P = .55) among the 4 types. Conclusions Complex biliary anatomy in the right liver graft usually requires biliodigestive anastomoses, which are often associated with complicated procedures. The precise delineation of the intrahepatic biliary anatomy provided by our clinical classification may contribute to better morbidity and mortality rates, especially for grafts at greatest anatomical risk.

Intrahepatic Biliary Anatomy Derived From Right Graft Adult Live Donor Liver Transplantation

Abstract: Objective The successful management of the bile duct in right graft adult live donor liver transplantation requires knowledge of both its central (hilar) and distal (sectorial) anatomy. The purpose of this study was to provide a systematic classification of its branching patterns to enhance clinical decision-making. Patients and Methods We analyzed three-dimensional computed tomography (3-D CT) imaging reconstructions of 139 potential live liver donors evaluated at our institution between January 2003 and June 2007. Results Fifty-four (n = 54 or 38.8%) donor candidates had a normal (classic) hilar and sectorial right bile duct anatomy (type I). Seventy-eight (n = 78 or 56.1%) cases had either hilar or sectorial branching abnormalities (types II or III). Seven (n = 7 or 5.1%) livers had a mixed type (IV) of a rare and complex central and distal anatomy. Conclusions We believe that the classification proposed herein can aid in the better organization and categorization of the variants encountered within the right-sided intrahepatic biliary system.