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Biomedical subjects

H P Meinzer

Publications and source records attributed to H P Meinzer.

At least 19 recordsLinked to original sources
PubMed2006

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.

Computer Simulation↗
PubMed2005

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.

Bone Cements↗
PubMed2005

[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.

Hepatectomy↗
PubMed2004

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.

Humans↗
PubMed2004

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.

Germany↗
PubMed2004

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.

Electronic Data Processing↗
PubMed2002

[Evaluation of CHILI teleradiology network 4 years after clinical implementation].

The CHILI teleradiology network has more than 60 installations in Germany and the USA. Radiological images and cardiological multiframe series are exchanged in clinical routine. This article investigates in what way and how often the system is used. This is done by means of accounting files that are produced automatically by the system. User functions, transmission protocols, data quantity, frequencies and time of data transmission and teleconferences are evaluated and discussed in this paper. Different application scenarios have been identified and are described and analyzed as well. An important result is, that the system is not merely an emergency system. Instead, it is used in daily routine as a multifunctional, multimodality workstation with advanced features for teleradiology and telecardiology.

Computer Communication Networks↗
PubMed2002

The effect of virtual reality and training on liver operation planning.

OBJECTIVE: The three-dimensional relation of a liver tumour to the intrahepatic vascular trees is basis of operation planning in liver surgery. Yet it has not been proven whether 3D reconstruction and further computerised processing will enhance precision of operation planning in liver surgery which has been based on the liver segment classification of Couinaud up to now. DESIGN: Our interdisciplinary group (department of Surgery, German Cancer Research Center and Department of Radiology) has developed a new interactive computer-based quantitative 3D operation planning system for liver surgery which is being introduced into the clinical routine. The system quantifies the organ structures semiautomatically, defines resection planes depending on safety margins and the vascular trees, and presents the data in digital movies as well as in quantitative reports. We conducted a clinical trial to evaluate whether 3D reconstruction will lead to an improved operation planning. Data of 7 virtual patients were presented to a total of 81 surgeons in different levels of training. The tumours had to be assigned to a liver segment and subsequently drawn together with the operation proposals into a liver model. The precision of both was measured quantitatively for each surgeon and stratified concerning 2D and different types of 3D presentations. RESULTS: The 3D anatomy can be visualised in high quality which results in good perception of the third dimension (depth). Tumour assignment to liver segments was significantly correlated to the level of training (p < 0.05). There was a significant increase (p < 0.001) in the precision of tumour localisation by 51% and resection proposal from 2D through 3D reconstructions by 13%-21%. Quantitative differences of the simplified Couinaud's classification of the liver segments compared to the true vascular anatomy of up to 40% were found. CONCLUSION: The impact of individual 3D-reconstruction on surgical planning has been proven to be significant and increases precision quantitatively. The merit of Couinaud's classification may be enhanced by individualisation of the segment borders in future.

Hepatectomy↗
PubMed2002

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.

Humans↗
PubMed2000

Three-dimensional color Doppler reconstruction of intracardiac blood flow in patients with different heart valve diseases.

An improved perception of the magnitude and dynamics of intracardiac flow disturbances has been made possible by the advent of 3-dimensional (3-D) color Doppler, a new diagnostic procedure developed at our institution. This study describes the new insights derived from 3-D reconstruction of color Doppler flow patterns in patients with different heart valve diseases. The color Doppler flow data from 153 multiplanar transesophageal or transthoracic echocardiographic examinations has been obtained from 133 patients with heart valve disease; 73 patients had mitral regurgitation, 15 had mitral stenosis, 18 had aortic regurgitation, 26 had aortic stenosis, and 21 patients had tricuspid regurgitation. Four patients had pulmonary regurgitation associated with mitral valve disease. The 3-D reconstructions of color Doppler flow signals were accomplished by means of the "Heidelberg Raytracing model," developed at our institution. The 3-D color Doppler reconstructions were obtained in all patients. The 3-D images revealed for the first time the complex spatial distribution of the blood flow abnormalities in the heart chambers caused by different heart valve diseases. New patterns of intracardiac blood flow disturbances were observed and classified. Three-dimensional color Doppler provides a unique noninvasive method that can be easily applied for studying intracardiac blood flow disturbances in clinical practice.

Aortic Valve Insufficiency↗
PubMed2000

The impact of 3-dimensional reconstructions on operation planning in liver surgery.

BACKGROUND: Operation planning in liver surgery depends on the precise understanding of the 3-dimensional (D) relation of the tumor to the intrahepatic vascular trees. To our knowledge, the impact of anatomical 3-D reconstructions on precision in operation planning has not yet been studied. HYPOTHESIS: Three-dimensional reconstruction leads to an improvement of the ability to localize the tumor and an increased precision in operation planning in liver surgery. DESIGN: We developed a new interactive computer-based quantitative 3-D operation planning system for liver surgery, which is being introduced to the clinical routine. To evaluate whether 3-D reconstruction leads to improved operation planning, we conducted a clinical trial. The data sets of 7 virtual patients were presented to a total of 81 surgeons in different levels of training. The tumors had to be assigned to a liver segment and subsequently drawn together with the operation proposal into a given liver model. The precision of the assignment to a liver segment according to Couinaud classification and the operation proposal were measured quantitatively for each surgeon and stratified concerning 2-D and different types of 3-D presentations. RESULTS: The ability of correct tumor assignment to a liver segment was significantly correlated to the level of training (P<.05). Compared with 2-D computed tomography scans, 3-D reconstruction leads to a significant increase of precision in tumor localization by 37%. The target area of the resection proposal was improved by up to 31%. CONCLUSION: Three-dimensional reconstruction leads to a significant improvement of tumor localization ability and to an increased precision of operation planning in liver surgery.

Computer Simulation↗
PubMed2000

[Volumetric analysis and visualization of cardiologic ultrasound data].

BACKGROUND: Echocardiography is a standard imaging technique for the assessment of heart valve disease. The good spatial and temporal resolution is the basis for different methods which provide information about the severity of such defects. Dynamic colour visualisation and volumetric measurements of regurgitant jets are a new evaluating tool for the assessment of heart valve insufficiencies. METHODS: The regurgitant jet volume of 58 patients was evaluated on an external work-station after segmentation of the left atrium and compared to regurgitant volume; the correlation was good. This result is valid for central jets as well as for eccentric jets. CONCLUSIONS: Measurement of regurgitant jet volume is a method which considers the three-dimensional shape of the examined volume. Real-time visualisation techniques which support the interactive clipping of morphological structures provide dynamic visualisation of intracardiac flow during the heart cycle. Dynamic colour visualisation of jets together with myocardial structures allows the assignment of intracardiac flow to morphological structures.

Computer Graphics↗
PubMed2000

[Computer-assisted oral, maxillary and facial surgery].

BACKGROUND: Methods from the area of virtual reality are used in oral and maxillofacial surgery for the planning and three-dimensional individual simulation of surgeries. SIMULATION: In order to simulate complex surgeries with the aid of a computer, the diagnostic image data and especially various imaging modalities (CT, MRT, US) must be arranged in relation to each other, thus enabling rapid switching between the various modalities as well as the viewing of mixed images. Segmenting techniques for the reconstruction of three-dimensional representations of soft-tissue and osseous areas are required. We must develop ergonomic and intuitively useable interaction methods for the surgeon, thus allowing for precise and fast entry of the planned surgical intervention in the planning and simulation phase. SURGERY: During the surgical phase, instrument navigation tools offer the surgeon interactive support through operation guidance and control of potential dangers. This feature is already available today. Future intraoperative assistance will take the form of such passive tools for the support of intraoperative orientation as well as so-called tracking systems (semi-active systems) which accompany and support the surgeons' work. The final form are robots which execute specific steps completely autonomously. DISCUSSION: The techniques of virtual reality keep gaining in importance for medical applications. Many applications are still being developed or are still in the form of a prototype. However, it is already clear that developments in this area will have a considerable effect on the surgeon's routine work.

Computer Simulation↗
PubMed2000

[Use of virtual reality for MRI data of complex vascular structures].

UNLABELLED: During the last years because of the progress in magnetic resonance imaging (MRI) magnetic resonance angiography (MRA) has become a serious alternative to conventional X-ray angiography. The potential of MRA in combination with methods for three-dimensional reconstruction will be presented and different methods for image post-processing are discussed based on a number of cases. The examinations were performed on a clinical 1.5 T magnetic resonance tomograph (Siemens Vision, Erlangen) using conventional MR angiography sequences. The different options of post-processing were carried out online on the console and offline using dedicated workstations (Siemens Virtuoso and CHILI). DISCUSSION: Complex post-processing procedures are applied to different areas like pulmonary vasculature, thoracic aorta, abdominal aorta, and renal transplant arteries. Different diagnostic values can be seen for the variety of three-dimensional reconstruction methods. According to our experience volume rendering has been selected as the method of choice due to the time needed for reconstruction and the information content of the resulting image.

Aortography↗