iPad-assisted percutaneous nephrolithotomy (PCNL): a matched pair analysis compared to standard PCNL

PURPOSE

To compare iPad-assisted (Apple Inc., Cupertino, USA) percutaneous access to the kidney to the standard puncturing technique for percutaneous nephrolithotomy (PCNL).

METHODS

For the iPad-assisted PCNL, a computed tomography is performed prior to surgery, using fiducial radiopaque markers. The important anatomical structures (i.e. kidney, stones) are segmented using specific software enabling the superimposition of images semi-transparently on the iPad by marker-based navigation. Twenty-two patients underwent an iPad-assisted percutaneous puncture of the kidney for PCNL. Twenty-two patients of the clinical database from the Urological Department SLK Hospital Heilbronn, who underwent the standard puncturing technique, were matched to these patients. Matching criteria were age, gender, stone volume, body mass index, stone site and the absence of anatomical variation. Puncture time, radiation exposure and number of attempts for a successful puncture were evaluated. All procedures were performed by two experienced urologists. The standard puncturing method consisted of a combination of ultrasound and fluoroscopy guidance. Chi-square and t test were used to ensure that there was no difference in the matching criteria between the groups. To compare the two methods, U test, Kruskal-Wallis and Chi-square test were used.

RESULTS

Examination of radiation exposure showed a significant difference between the two groups in favour of the standard puncturing method (p < 0.01) and puncture time (p = 0.01). However, there was no significant difference in puncturing attempts (p = 0.45).

CONCLUSION

The iPad-assisted navigation, with the objective being to puncture the renal collecting system, represents a new technique (IDEAL criteria 2b), which proved to be applicable in clinical practice, but still has potential for technical improvement.

OpenHELP (Heidelberg laparoscopy phantom): development of an open-source surgical evaluation and training tool

Background

Apart from animal testing and clinical trials, surgical research and laparoscopic training mainly rely on phantoms. The aim of this project was to design a phantom with realistic anatomy and haptic characteristics, modular design and easy reproducibility. The phantom was named open-source Heidelberg laparoscopic phantom (OpenHELP) and serves as an open-source platform.

Methods

The phantom was based on an anonymized CT scan of a male patient. The anatomical structures were segmented to obtain digital three-dimensional models of the torso and the organs. The digital models were materialized via rapid prototyping. One flexible, using an elastic abdominal wall, and one rigid method, using a plastic shell, to simulate pneumoperitoneum were developed. Artificial organ production was carried out sequentially starting from raw gypsum models to silicone molds to final silicone casts. The reproduction accuracy was exemplarily evaluated for ten silicone rectum models by comparing the digital 3D surface of the original rectum with CT scan by calculating the root mean square error of surface variations. Haptic realism was also evaluated to find the most realistic silicone compositions on a visual analog scale (VAS, 0–10).

Results

The rigid and durable plastic torso and soft silicone organs of the abdominal cavity were successfully produced. A simulation of pneumoperitoneum could be created successfully by both methods. The reproduction accuracy of ten silicone rectum models showed an average root mean square error of 2.26 (0–11.48) mm. Haptic realism revealed an average value on a VAS of 7.25 (5.2–9.6) for the most realistic rectum.

Conclusion

The OpenHELP phantom proved to be feasible and accurate. The phantom was consecutively applied frequently in the field of computer-assisted surgery at our institutions and is accessible as an open-source project at www.open-cas.org for the academic community.

Using a shape prior for robust modeling of the mitral annulus on 4D ultrasound data

PURPOSE

Over 40,000 annuloplasty rings are implanted each year in the USA to treat mitral regurgitation. However, the used measuring techniques to select a suitable annuloplasty ring are imprecise and highly depending on the expert's experience. This can cause a re-occurrence of the mitral regurgitation or an annuloplasty ring dehiscence, and thus the necessity of a re-operation. We propose a method to create a 4D model of the mitral annulus from ultrasound data to enable precise measurement and patient-specific implant planning.

METHODS

An initial mitral annulus model is placed interactively in the 4D image data by defining commissure points and the annulus plane for one time step in diastole and systole. The model is automatically optimized using distinct image features. A shape and pose prior of the mitral annulus is used to compensate for artifacts and to enforce a plausible anatomical morphology, while a temporal alignment ensures a natural motion of the 4D model.

RESULTS

Ground truth data were created for 4D images of 42 patients with varying image quality. A parameter and shape prior training was performed on a third of the ground truth data, while the rest was used to validate the method. The average error of the resulting mitral annulus models was computed as 2.25 ( +/-0.38 ) mm. The average expert standard deviation was determined as 1.86 (+/-0.32 ) mm.

CONCLUSION

The proposed method enables the 4D modeling of mitral annuli based on ultrasound data in less than 2 min. The resulting models are comparable to manually delineated models and can be used for measurements of annular geometries and patient-specific annuloplasty treatment planning.

Magnetic tracking in the operation room using the da Vinci(®) telemanipulator is feasible

In recent years, robotic assistance for surgical procedures has grown on a worldwide scale, particularly for use in more complex operations. Such operations usually require meticulous handling of tissue, involve a narrow working space and limit the surgeon’s sense of orientation in the human body. Improvement in both tissue handling and working within a narrow working space might be achieved through the use of robotic assistance. Soft tissue navigation might improve orientation by visualizing important target and risk structures intraoperatively, thereby possibly improving patient outcome. Prerequisites for navigation are its integration into the surgical workflow and accurate localization of both the instruments and patient. Magnetic tracking allows for good integration but is susceptible to distortion through metal or electro-magnetic interference, which may be caused by the operation table or a robotic system. We have investigated whether magnetic tracking can be used in combination with the da Vinci^® (DV) telemanipulator in terms of stability and precision. We used a common magnetic tracking system (Aurora^®, NDI Inc.) with the DV in a typical operation setup. Magnetic field distortion was evaluated using a measuring facility, with the following reference system: without any metal (R), operation table alone (T), DV in standby (D) and DV in motion (Dm). The maximum error of the entire tracking volume for R, T, D and Dm was 9.9, 32.8, 37.9 and 37.2 mm, respectively. Limiting the tracking volume to 190 mm (from cranial to caudal) resulted in a maximum error of 4.0, 8.3, 8.5 and 8.9 mm, respectively. When used in the operation room, magnetic tracking shows high errors, mainly due to the operation table. The target area should be limited to increase accuracy, which is possible for most surgical applications. The use of the da Vinci^® telemanipulator only slightly aggravates the distortion and can thus be used in combination with magnetic tracking systems.

Image analysis and modeling in medical image computing. Recent developments and advances

BACKGROUND

Medical image computing is of growing importance in medical diagnostics and image-guided therapy. Nowadays, image analysis systems integrating advanced image computing methods are used in practice e.g. to extract quantitative image parameters or to support the surgeon during a navigated intervention. However, the grade of automation, accuracy, reproducibility and robustness of medical image computing methods has to be increased to meet the requirements in clinical routine.

OBJECTIVES

In the focus theme, recent developments and advances in the field of modeling and model-based image analysis are described. The introduction of models in the image analysis process enables improvements of image analysis algorithms in terms of automation, accuracy, reproducibility and robustness. Furthermore, model-based image computing techniques open up new perspectives for prediction of organ changes and risk analysis of patients.

METHODS

Selected contributions are assembled to present latest advances in the field. The authors were invited to present their recent work and results based on their outstanding contributions to the Conference on Medical Image Computing BVM 2011 held at the University of Lübeck, Germany. All manuscripts had to pass a comprehensive peer review.

RESULTS

Modeling approaches and model-based image analysis methods showing new trends and perspectives in model-based medical image computing are described. Complex models are used in different medical applications and medical images like radiographic images, dual-energy CT images, MR images, diffusion tensor images as well as microscopic images are analyzed. The applications emphasize the high potential and the wide application range of these methods.

CONCLUSIONS

The use of model-based image analysis methods can improve segmentation quality as well as the accuracy and reproducibility of quantitative image analysis. Furthermore, image-based models enable new insights and can lead to a deeper understanding of complex dynamic mechanisms in the human body. Hence, model-based image computing methods are important tools to improve medical diagnostics and patient treatment in future.

The extensible open-source rigid and affine image registration module of the Medical Imaging Interaction Toolkit (MITK)

Although non-rigid registration methods are available or under development for many specific problems in medicine, rigid and affine registration is an important task that is often performed for pre-aligning images before using non-rigid registration. In this paper, we present a free and open-source application for rigid and affine image registration, which is designed both for developers and for end-users. The application is based on the Medical Imaging Interaction Toolkit (MITK) and allows for inter-modality and intra-modality rigid 2D-2D and 3D-3D registration of medical images such as CT, MRI, or ultrasound. The framework as well as the application can be easily extended by adding new transforms, metrics and optimizers. Thus, developers of new algorithms are enabled to test and use their algorithms more quickly, spending less work on user interfaces. Additionally, the framework provides the possibility to use image masks to restrict the evaluation of metric values by the optimizer on certain areas of the images.

Intravenous 64-multi-detector row CT-cholangiography of porcine livers: a feasibility study with definition of the temporal window for optimal bile duct delineation

BACKGROUND/PURPOSE

To assess the feasibility of intravenous 64-multi-detector row computed tomography (CT)-cholangiography of porcine livers with definition of the temporal window for optimal bile duct delineation.

METHODS

Six healthy Landrace pigs, each weighing 28.97 +/- 2.99 kg, underwent 64-multi-detector row CT-cholangiography. Each pig was infused with 50 ml of meglumine iotroxate continuously over a period of 20 min and, starting with the initiation of the infusion, 18 consecutive CT scans of the abdomen at 2-min intervals were acquired. All series were evaluated for bile duct visualization scores and maximum bile duct diameters as primary study goals and bile duct attenuation and liver enhancement as secondary study goals.

RESULTS

Of the 16 analyzed biliary tract segments, maximum bile duct visualization scores ranged between 4.00 +/- 0.00 and 2.83 +/- 1.47. Time to maximum bile duct visualization scores ranged between 10 and 34 min. Average bile duct visualization scores for the 10- to 34-min interval ranged between 3.99 +/- 0.05 and 2.78 +/- 0.10. Maximum bile duct diameters ranged between 6.47 +/- 1.05 and 2.65 +/- 2.23 mm. Time to maximum bile duct diameters ranged between 24 and 34 min. Average bile duct diameters for the 10- to 34-min interval ranged between 6.00 +/- 0.38 and 2.40 +/- 0.13 mm.

CONCLUSIONS

Intravenous 64-multi-detector row CT-cholangiography of non-diseased porcine liver is feasible, with the best bile duct delineation acquired between 10 and 34 min after initiation of the contrast agent infusion.

Interactive segmentation framework of the Medical Imaging Interaction Toolkit

Interactive methods are indispensable for real world applications of segmentation in medicine, at least to allow for convenient and fast verification and correction of automated techniques. Besides traditional interactive tasks such as adding or removing parts of a segmentation, adjustment of contours or the placement of seed points, the relatively recent Graph Cut and Random Walker segmentation methods demonstrate an interest in advanced interactive strategies for segmentation. Though the value of toolkits and extensible applications is generally accepted for the development of new segmentation algorithms, the topic of interactive segmentation applications is rarely addressed by current toolkits and applications. In this paper, we present the extension of the Medical Imaging Interaction Toolkit (MITK) with a framework for the development of interactive applications for image segmentation. The framework provides a clear structure for the development of new applications and offers a plugin mechanism to easily extend existing applications with additional segmentation tools. In addition, the framework supports shape-based interpolation and multi-level undo/redo of modifications to binary images. To demonstrate the value of the framework, we also present a free, open-source application named InteractiveSegmentation for manual segmentation of medical images (including 3D+t), which is built based on the extended MITK framework. The application includes several features to effectively support manual segmentation, which are not found in comparable freely available applications. InteractiveSegmentation is fully developed and successfully and regularly used in several projects. Using the plugin mechanism, the application enables developers of new algorithms to begin algorithmic work more quickly.

Advances in medical image computing

OBJECTIVES

Medical image computing has become a key technology in high-tech applications in medicine and an ubiquitous part of modern imaging systems and the related processes of clinical diagnosis and intervention. Over the past years significant progress has been made in the field, both on methodological and on application level. Despite this progress there are still big challenges to meet in order to establish image processing routinely in health care. In this issue, selected contributions of the German Conference on Medical Image Processing (BVM) are assembled to present latest advances in the field of medical image computing.

METHODS

The winners of scientific awards of the German Conference on Medical Image Processing (BVM) 2008 were invited to submit a manuscript on their latest developments and results for possible publication in Methods of Information in Medicine. Finally, seven excellent papers were selected to describe important aspects of recent advances in the field of medical image processing.

RESULTS

The selected papers give an impression of the breadth and heterogeneity of new developments. New methods for improved image segmentation, non-linear image registration and modeling of organs are presented together with applications of image analysis methods in different medical disciplines. Furthermore, state-of-the-art tools and techniques to support the development and evaluation of medical image processing systems in practice are described.

CONCLUSIONS

The selected articles describe different aspects of the intense development in medical image computing. The image processing methods presented enable new insights into the patient's image data and have the future potential to improve medical diagnostics and patient treatment.

Towards a mixed reality environment for preoperative planning of cardiac surgery

We present a novel approach to studying physical heart models by coupling them with virtual 3D representations in a mixed reality environment. The limitations of standalone physical models (non-interactive, static) are overcome by the corresponding virtual models, which in turn become more natural to interact with. The potential of this approach is exemplified by a setup which enables cardiac surgeons to interactively trace the mitral annulus, a part of the cardiac skeleton playing a vital role in mitral valve surgery. We present results of a pilot study and discuss ways of improving and extending the system. The described mixed reality environment could easily be adapted to other fields and thus has the potential to become a new tool for investigating 3D medical data.

Development of a navigation system for minimally invasive esophagectomy

BACKGROUND

A major challenge of minimally invasive esophagectomy is the uncertainty about the exact location of the tumor and associated lymph nodes. This study aimed to develop a navigation system for visualizing surgical instruments in relation to the tumor and anatomic structures in the chest.

METHODS

An immobilization device consisting of a vacuum mattress fixed to a stretcher was built to decrease patient movement and organ deformation. Computer tomography (CT) markers were embedded in the stretcher at a defined distance to a detachable plate with optical markers on the side of the stretcher. A second plate of optical markers was fixed to the operating instrument. These two optical marker plates were tracked with an optical tracking system. Their positions were then registered in a preoperative CT data set using the authors' navigation software. This allowed a real-time visualization of the instrument and target structures. To assess the accuracy of the system, the authors designed a phantom consisting of a box containing small spheres in a specific three-dimensional layout. The positions of the spheres were first measured with the navigation system and then compared with the known real positions to determine the accuracy of the system.

RESULTS

In the accuracy assessment, the navigation system showed a precision of 0.95 +/- 0.78 mm. In a test data set, the instrument could be successfully navigated to the tumor and target structures.

CONCLUSION

The described navigation system provided real-time information about the position and orientation of the working instrument in relation to the tumor in an experimental setup. Consequently, it might improve minimally invasive esophagectomy and allow for surgical dissection in an adequate distance to the tumor margin and ease the location of affected lymph nodes.

Automatic generation of 3D statistical shape models with optimal landmark distributions

OBJECTIVES

To point out the problem of non-uniform landmark placement in statistical shape modeling, to present an improved method for generating landmarks in the 3D case and to propose an unbiased evaluation metric to determine model quality.

METHODS

Our approach minimizes a cost function based on the minimum description length (MDL) of the shape model to optimize landmark correspondences over the training set. In addition to the standard technique, we employ an extended remeshing method to change the landmark distribution without losing correspondences, thus ensuring a uniform distribution over all training samples. To break the dependency of the established evaluation measures generalization and specificity from the landmark distribution, we change the internal metric from landmark distance to volumetric overlap.

RESULTS

Redistributing landmarks to an equally spaced distribution during the model construction phase improves the quality of the resulting models significantly if the shapes feature prominent bulges or other complex geometry.

CONCLUSIONS

The distribution of landmarks on the training shapes is -- beyond the correspondence issue -- a crucial point in model construction.

[Three-dimensional echocardiography in cardiac surgery. Current status and perspectives]

Three-dimensional (3D) echocardiography is a new imaging technique that can provide useful information about cardiovascular morphology, pathology, and function. Recent refinements in instrumentation, data acquisition, post-processing, and computation speed allow 3D echocardiography to play an important role in cardiac imaging. These modalities provide comprehensive information on ventricular and valve morphology and function. Combined with 3D color Doppler sonography, further assessment of valvular function and determination of flow in the left ventricular outflow tract and cross-septal defects are now possible. Three-dimensional color flow imaging also makes echocardiography accurate for assessing the severity of mitral regurgitation. The purpose of this review is to describe technical developments in 3D echocardiography and its clinical application in cardiac surgery. Moreover, based on clinical studies at our centre, we describe the morphology of the mitral valve, its flow pattern, and function of the mitral annulus.

Implementation and evaluation of a new workflow for registration and segmentation of pulmonary MRI data for regional lung perfusion assessment

Recently it has been shown that regional lung perfusion can be assessed using time-resolved contrast-enhanced magnetic resonance (MR) imaging. Quantification of the perfusion images has been attempted, based on definition of small regions of interest (ROIs). Use of complete lung segmentations instead of ROIs could possibly increase quantification accuracy. Due to the low signal-to-noise ratio, automatic segmentation algorithms cannot be applied. On the other hand, manual segmentation of the lung tissue is very time consuming and can become inaccurate, as the borders of the lung to adjacent tissues are not always clearly visible. We propose a new workflow for semi-automatic segmentation of the lung from additionally acquired morphological HASTE MR images. First the lung is delineated semi-automatically in the HASTE image. Next the HASTE image is automatically registered with the perfusion images. Finally, the transformation resulting from the registration is used to align the lung segmentation from the morphological dataset with the perfusion images. We evaluated rigid, affine and locally elastic transformations, suitable optimizers and different implementations of mutual information (MI) metrics to determine the best possible registration algorithm. We located the shortcomings of the registration procedure and under which conditions automatic registration will succeed or fail. Segmentation results were evaluated using overlap and distance measures. Integration of the new workflow reduces the time needed for post-processing of the data, simplifies the perfusion quantification and reduces interobserver variability in the segmentation process. In addition, the matched morphological data set can be used to identify morphologic changes as the source for the perfusion abnormalities.

Stereolithographic reproduction of complex cardiac morphology based on high spatial resolution imaging

BACKGROUND

Precise knowledge of cardiac anatomy is mandatory for diagnosis and treatment of congenital heart disease. Modern imaging techniques allow high resolution three-dimensional (3D) imaging of the heart and great vessels. In this study stereolithography was evaluated for 3D reconstructions of multidetector computed tomography (MDCT) and magnetic resonance imaging (MRI) data.

METHODS

A plastinated heart specimen was scanned with MDCT and after segmentation a stereolithographic (STL) model was produced with laser sinter technique. After scanning the STL model with MDCT these data were compared with those of the original specimen after rigid registration using the iterative closest points algorithm (ICP). The two surfaces of the original specimen and STL model were matched and the symmetric mean distance was calculated. Additionally, the heart and great vessels of patients (age range 41 days-21 years) with congenital heart anomalies were imaged with MDCT (n=2) or free breathing steady, state free-precession MRI (n=3). STL models were produced from these datasets and the cardiac segments were analyzed by two independent observers.

RESULTS

All cardiac structures of the heart specimen were reconstructed as a STL model within sub-millimeter resolution (mean surface distance 0.27+/-0.76 mm). Cardiac segments of the STL patient models were correctly analyzed by two independent observers compared to the original 3D datasets, echocardiography (n=5), x-ray angiography (n=5), and surgery (n=4).

CONCLUSIONS

High resolution MDCT or MRI 3D datasets can be accurately reconstructed using laser sinter technique. Teaching, research and preoperative planning may be facilitated in the future using this technique.

Precision targeting of liver lesions with a needle-based soft tissue navigation system

In this study, we assessed the targeting precision of a previously reported needle-based soft tissue navigation system. For this purpose, we implanted 10 2-ml agar nodules into three pig livers as tumor models, and two of the authors used the navigation system to target the center of gravity of each nodule. In order to obtain a realistic setting, we mounted the livers onto a respiratory liver motion simulator that models the human body. For each targeting procedure, we simulated the liver biopsy workflow, consisting of four steps: preparation, trajectory planning, registration, and navigation. The lesions were successfully hit in all 20 trials. The final distance between the applicator tip and the center of gravity of the lesion was determined from control computed tomography (CT) scans and was 3.5 +/- 1.1 mm on average. Robust targeting precision of this order of magnitude would significantly improve the clinical treatment standard for various CT-guided minimally invasive interventions in the liver.

Reproducible Simulation of Respiratory Motion in Porcine Lung Explants

PURPOSE

To develop a model for exactly reproducible respiration motion simulations of animal lung explants inside an MR-compatible chest phantom.

MATERIALS AND METHODS

The materials included a piston pump and a flexible silicone reconstruction of a porcine diaphragm and were used in combination with an established MR-compatible chest phantom for porcine heart-lung preparations. The rhythmic inflation and deflation of the diaphragm at the bottom of the artificial thorax with water (1 - 1.5 L) induced lung tissue displacement resembling diaphragmatic breathing. This system was tested on five porcine heart-lung preparations using 1.5T MRI with transverse and coronal 3D-GRE (TR/TE = 3.63/1.58, 256 x 256 matrix, 350 mm FOV, 4 mm slices) and half Fourier T2-FSE (TR/TE = 545/29, 256 x 192, 350 mm, 6 mm) as well as multiple row detector CT (16 x 1 mm collimation, pitch 1.5, FOV 400 mm, 120 mAs) acquired at five fixed inspiration levels. Dynamic CT scans and coronal MRI with dynamic 2D-GRE and 2D-SS-GRE sequences (image frequencies of 10/sec and 3/sec, respectively) were acquired during continuous "breathing" (7/minute). The position of the piston pump was visually correlated with the respiratory motion visible through the transparent wall of the phantom and with dynamic displays of CT and MR images. An elastic body splines analysis of the respiratory motion was performed using CT data.

RESULTS

Visual evaluation of MRI and CT showed three-dimensional movement of the lung tissue throughout the respiration cycle. Local tissue displacement inside the lung explants was documented with motion maps calculated from CT. The maximum displacement at the top of the diaphragm (mean 26.26 [SD 1.9] mm on CT and 27.16 [SD 1.5] mm on MRI, respectively [p = 0.25; Wilcoxon test]) was in the range of tidal breathing in human patients.

CONCLUSION

The chest phantom with a diaphragmatic pump is a promising platform for multi-modality imaging studies of the effects of respiratory lung motion.

Three-Dimensional Assessment of Left Ventricular Geometry and Annular Dilatation Provides New Mechanistic Insights into the Surgical Correction of Ischemic Mitral Regurgitation

BACKGROUND

The aim of this study was to investigate the relationship between LV geometry, annular shape and the amount of regurgitation in patients with ischemic mitral regurgitation (group 1, n = 30) compared to patients with primary mitral valve lesions (group 2, n = 30).

METHODS

LV geometry was assessed by the sphericity index, i.e., LV volume divided by the volume of a sphere with a diameter equal to the longest axis. Annular geometry was evaluated by diameters, areas and their percentual shortening. The degree of mitral regurgitation was assessed as jet volumes by 3D-echocardiography.

RESULTS

Group 1 showed significantly larger longitudinal (54.3 +/- 3.1 vs. 40.9 +/- 2.6 mm) and antero-posterior (32.2 +/- 3.3 vs. 27.1 +/- 2.9 mm) annulus diameters and areas (993.3 +/- 66.6 vs. 702.1 +/- 47.9 mm (2)) than group 2. No asymmetric annular enlargement was found in either group. Annular enlargement correlated to the degree of mitral regurgitation in group 1 but not in group 2. Annular area shortening was significantly impaired in group 2 and the sphericity index was larger in group 1 than in group 2. In group 1, the sphericity index was significantly correlated to the degree of mitral regurgitation (r = 0.87; P < 0.001).

CONCLUSIONS

These findings suggest that ischemic mitral regurgitation was mostly associated with a global left ventricular enlargement, in which annulus dilatation and its reduced contraction play a significant role.

Branching patterns and drainage territories of the middle hepatic vein in computer-simulated right living-donor hepatectomies

Full right hepatic grafts are most frequently used for adult-to-adult living donor liver transplantation (LDLT). One of the major problems is venous drainage of segments 5 and 8. Thus, this study was designed to provide information on venous drainage of right liver lobes for operation-planning. Fifty-six CT data sets from routine clinical imaging were evaluated retrospectively using a liver operation-planning system. We defined and analyzed venous drainage segments and the impact of anatomic variations of the middle hepatic vein (MHV) on venous outflow from segments 5 and 8. MHV variations led to significant shifts of segment 5 drainage between the middle and right hepatic vein. In cases with the most frequent MHV branching pattern (n = 33), a virtual hepatectomy closely right to the MHV intersected drainage vessels that provided drainage for 30% of the potential graft, not taking into account potential veno-venous shunts. In individuals with inferior MHV branches that extend far into segments 5 and 6 (n = 10), the overall graft volume at risk of impaired venous drainage increased by 5% (p < 0.001). If this is confirmed in clinical trials and correlated with intraoperative findings, the use of liver operation-planning systems would be beneficial to improve overall outcome after right lobe LDLT.

MRT-Analyse der Bewegungen von Lungenrundherden

Visualization of pulmonary nodules using magnetic resonance imaging (MRI) plays a minor role compared with computed tomography (CT). Technical developments made it possible to apply MRI more and more frequently in functional imaging. Imaging of the motion of pulmonary nodules during respiration, e.g., to optimize high precision therapy techniques, is a new field of research. This paper describes developments in analysis and visualization of pulmonary nodules during respiration using MRI. Besides actual 2D techniques new 3D techniques to quantify motion of pulmonary nodules during respiration are presented.

Osseous integration of calcium phosphate in osteoporotic vertebral fractures after kyphoplasty: initial results from a clinical and experimental pilot study

INTRODUCTION

This study evaluated the radiological changes at the bone-cement interface of calcium phosphate cement (CPC) and polymethylmethacrylate (PMMA) 12 months after kyphoplasty. In a pilot experiment, we additionally performed a histomorphometric analysis in osteopenic foxhounds to analyze the process of osseous integration of CPC and PMMA.

METHODS

Twenty postmenopausal female patients with 46 vertebral compression fractures (VCF) were treated by kyphoplasty, utilizing CPC (N=28) or PMMA (N=18) for intravertebral stabilization. After a 12-month follow-up, we measured the density changes of border voxels at the bone-cement interface by computed tomography (CT) using dedicated software algorithms. We defined the border-voxel density (BVD) as a parameter of cement resorption at the interface. We also investigated the bone-implant interface in three osteopenic foxhounds by histomorphometry 3, 6, and 12 months after cement implantation.

RESULTS

Twelve months after kyphoplasty, only CPC showed a significant decrease of the BVD compared to PMMA (p<0.01), indicating a slow progress of resorption at the interface. Histomorphometry of the dog vertebrae showed near total bone coverage of CPC implants, whereas the PMMA surface exhibited only 30% direct bone contact (p<0.01). We also observed a time-dependent increase in the number of discernable osteons close to the interface of CPC, but no bone tissue within PMMA (p<0.01).

CONCLUSIONS

The decrease of the BVD 12 months after kyphoplasty may indicate osseous integration of CPC by: (1) the ingrowth of bone tissue and (2) osteonal penetration close to the interface.

[The role of 3-D imaging and computer-based postprocessing for surgery of the liver and pancreas]

Cross-sectional imaging based on navigation and virtual reality planning tools are well-established in the surgical routine in orthopedic surgery and neurosurgery. In various procedures, they have achieved a significant clinical relevance and efficacy and have enhanced the discipline's resection capabilities. In abdominal surgery, however, these tools have gained little attraction so far. Even with the advantage of fast and high resolution cross-sectional liver and pancreas imaging, it remains unclear whether 3D planning and interactive planning tools might increase precision and safety of liver and pancreas surgery. The inability to simply transfer the methodology from orthopedic or neurosurgery is mainly a result of intraoperative organ movements and shifting and corresponding technical difficulties in the on-line applicability of presurgical cross sectional imaging data. For the interactive planning of liver surgery, three systems partly exist in daily routine: HepaVision2 (MeVis GmbH, Bremen), LiverLive (Navidez Ltd, Slovenia) and OrgaNicer (German Cancer Research Center, Heidelberg). All these systems have realized a half- or full-automatic liver-segmentation procedure to visualize liver segments, vessel trees, resected volumes or critical residual organ volumes, either for preoperative planning or intraoperative visualization. Acquisition of data is mainly based on computed tomography. Three-dimensional navigation for intraoperative surgical guidance with ultrasound is part of the clinical testing. There are only few reports about the transfer of the visualization of the pancreas, probably caused by the difficulties with the segmentation routine due to inflammation or organ-exceeding tumor growth. With this paper, we like to evaluate and demonstrate the present status of software planning tools and pathways for future pre- and intraoperative resection planning in liver and pancreas surgery.

CT volumetry of intravertebral cement after kyphoplasty. Comparison of polymethylmethacrylate and calcium phosphate in a 12-month follow-up

This study was intended to measure the volume of intravertebral cement after balloon kyphoplasty with high resolution computed tomography (CT) and dedicated software. Volume changes of biocompatible calcium phosphate cement (CPC) were detected during a follow-up of 12 months. Measurements were compared with a control group of patients treated with polymethylmethacrylate (PMMA). Twenty-three vertebrae (14 CPC, 9 PMMA) of 12 patients were examined with CT using an identical imaging protocol. Dedicated software was used to quantify intravertebral cement volume in subvoxel resolution by analyzing each cement implant with a density-weighted algorithm. The mean volume reduction of CPC was 0.08 ml after 12 months, which corresponds to an absorption rate of 2 vol%. However, the difference did not reach significance level (P>0.05). The mean error estimate was 0.005 ml, indicating excellent precision of the method. CT volumetry appears a precise tool for measurement of intravertebral cement volume. CT volumetry offers the possibility of in vivo measurement of CPC resorption.

The integration of medical images with the electronic patient record and their web-based distribution

Medical images are currently created digitally and stored in the radiology department's picture archiving and communication system. Reports are usually stored in the electronic patient record of other information systems, such as the radiology information system (RIS) and the hospital information system (HIS). But high-quality services can only be provided if electronic patient record data is integrated with digital images in picture archiving and communication systems. Clinicians should be able to access both systems' data in an integrated and consistent way as part of their regular working environment, whether HIS or RIS. Also, this system should allow for teleconferencing with other users, eg, for consultation with a specialist in the radiology department. This article describes a web-based solution that integrates the digital images of picture archiving and communication systems with electronic patient record/HIS/RIS data and has built-in teleconferencing functionality. This integration has been successfully tested using three different commercial RIS and HIS products.

Internationalization of healthcare applications: a generic approach for PACS workstations

OBJECTIVES

Along with the revolution of information technology and the increasing use of computers world-wide, software providers recognize the emerging need for internationalized, or global, software applications. The importance of internationalization comes from its benefits such as addressing a broader audience, making the software applications more accessible, easier to use, more flexible to support and providing users with more consistent information. In addition, some governmental agencies, e.g., in Spain, accept only fully localized software. Although the healthcare communication standards, namely, Digital Imaging and Communication in Medicine (DICOM) and Health Level Seven (HL7) support wide areas of internationalization, most of the implementers are still protective about supporting the complex languages. This paper describes a generic internationalization approach for Picture Archiving and Communication System (PACS) workstations.

METHODS

The Unicode standard is used to internationalize the application user interface. An encoding converter was developed to encode and decode the data between the rendering module (in Unicode encoding) and the DICOM data (in ISO 8859 encoding). An integration gateway was required to integrate the internationalized PACS components with the different PACS installations. To introduce a pragmatic example, the described approach was applied to the CHILI PACS workstation.

RESULTS

The approach has enabled the application to handle the different internationalization aspects transparently, such as supporting complex languages, switching between different languages at runtime, and supporting multilingual clinical reports.

CONCLUSIONS

In the healthcare enterprises, internationalized applications play an essential role in supporting a seamless flow of information between the heterogeneous multivendor information systems.

Advances in biomedical image analysis--past, present and future challenges

Starting from raw data files coding eight bits of gray values per image pixel and identified with no more than eight characters to refer to the patient, the study, and technical parameters of the imaging modality, biomedical imaging has undergone manifold and rapid developments. Today, rather complex protocols such as Digital Imaging and Communications in Medicine (DICOM) are used to handle medical images. Most restrictions to image formation, visualization, storage and transfer have basically been solved and image interpretation now sets the focus of research. Currently, a method-driven modeling approach dominates the field of biomedical image processing, as algorithms for registration, segmentation, classification and measurements are developed on a methodological level. However, a further metamorphosis of paradigms has already started. The future of medical image processing is seen in task-oriented solutions integrated into diagnosis, intervention planning, therapy and follow-up studies. This alteration of paradigms is also reflected in the literature. As German activities are strongly tied to the international research, this change of paradigm is demonstrated by selected papers from the German annual workshop on medical image processing collected in this special issue.

ALES: cell lineage analysis and mapping of developmental events

MOTIVATION

Animals build their bodies by altering the fates of cells. The way in which they do so is reflected in the topology of cell lineages and the fates of terminal cells. Cell lineages should, therefore, contain information about the molecular events that determined them. Here we introduce new tools for visualizing, manipulating, and extracting the information contained in cell lineages. Our tools enable us to analyze very large cell lineages, where previously analyses have only been carried out on cell lineages no larger than a few dozen cells.

RESULTS

Ales (A Lineage Evaluation System) allows the display, evaluation and comparison of cell lineages with the aim of identifying molecular and cellular events underlying development. Ales introduces a series of algorithms that locate putative developmental events. The distribution of these predicted events can then be compared to gene expression patterns or other cellular characteristics. In addition, artificial lineages can be generated, or existing lineages modified, according to a range of models, in order to test hypotheses about lineage evolution.

AVAILABILITY

The program can run on any operating system with a compliant Java 2 environment. Ales is free for academic use and can be downloaded from http://mbi.dkfz-heidelberg.de/mbi/research/cellsim/ales.

Problems of interactive segmentation

Computer-assisted surgery makes a patient-individual treatment feasible, aiming at decreased surgical risk and reduced recovery time of patients. At present, in areas of application, e.g., heart surgery as well as craniofacial surgery, its use is still limited to complex cases due to the high effort. In surgical planning, it is caused by extensive medical image analysis, including tissue classification. Especially, the classification (or segmentation) requires a lot of manual intervention. For a long time research has been devoted solely to computational aspects of segmentation, where usability aspects has been out of scope. This article focuses on the major problems of interactive segmentation and provides consequences on the segmentation process towards a solution.