PubMed Health⌕ Search

Biomedical subjects

Hans-Peter Meinzer

Publications and source records attributed to Hans-Peter Meinzer.

At least 19 recordsLinked to original sources
PubMed2006

Imaging of aortopulmonary collateral arteries with high-resolution multidetector CT.

BACKGROUND: Precise visualization of the pulmonary vasculature is mandatory for adequate treatment of patients with pulmonary atresia and ventricular septal defect (PA-VSD). Aortopulmonary collateral arteries (APCs) can be visualized by selective injections of contrast agent in the catheterization laboratory. OBJECTIVE: To evaluate multidetector CT (MDCT) and different image postprocessing methods for analysis of complex pulmonary blood supply in patients with PA-VSD. MATERIALS AND METHODS: Eight patients (6 weeks to 27.8 years of age) with PA-VSD and APCs underwent MDCT and cardiac catheterization. Using multiplanar reformatting, volume rendering and semiautomatic segmentation algorithms, the aorta, pulmonary arteries and APCs were displayed. MDCT and cardiac catheterization were analyzed by two independent observers. RESULTS: MDCT accurately imaged central pulmonary arteries (n=8), aortopulmonary shunts (n=2), right ventricular to pulmonary artery conduits (n=2) and origin, course and intrapulmonary connections of APCs (n=25), compared to X-ray angiography. A high correlation was found between the MDCT vessel diameter measurements by two independent observers (n=70, r=0.96, P<0.01) and between MDCT and angiographic vessel diameter measurements (n=68, r=0.96, P<0.01). CONCLUSIONS: Using three-dimensional imaging software, a complex pulmonary blood supply can be non-invasively and accurately imaged with high-resolution MDCT. This technique may help to reduce the number of cardiac catheterizations or guide interventional or surgical therapy.

Adolescent↗
PubMed2006

A clinical study of annular geometry and dynamics in patients with ischemic mitral regurgitation: new insights into asymmetrical ring annuloplasty.

OBJECTIVE: Recent studies in animals showed that regional annulus distortion is a major determinant of ischemic mitral regurgitation (IMR) and accordingly suggested new surgical approaches with asymmetrical annuloplasty rings. As accurate measurement of annulus in patients is still a challenge, we performed this study to analyze the changes in three-dimensional annular geometry in patients with IMR compared to primary valvular lesions. METHODS: We studied 110 patients divided into three groups: (1) 30 with coronary artery disease without IMR, (2) 38 with chronic IMR, and (3) 42 with MR due to primary valvular lesions. Longitudinal and septal-lateral annulus diameters; global diastolic and systolic annular area and its percentual shortening, diastolic and systolic areas of six regions corresponding to the segmental Carpentier classification were measured by 3D-echocardiography. The degree of MR was assessed by three-dimensional color Doppler. Global and regional left ventricular geometry were assessed by sphericity index and by measuring anterior and posterior tethering of papillary muscles. RESULTS: Patients with significant IMR (group 2) showed larger longitudinal (52.7+/-3.9 mm vs 41.8+/-2.9 mm; p<0.01) and antero-lateral (31.8+/-3.5mm vs 26.7+/-2.8mm; p<0.01) annular diameters than the patients with MR due to primary valvular lesions (group 3). Diastolic (997.8+/-64.9 mm(2) vs 700.7+/-46.8mm(2); p<0.01) and systolic (894.9+/-57.3mm(2) vs 547.3+/-35.0mm(2); p<0.01) annular areas were larger in group 2 than in group 3. Annular area change was significantly lower in the group with ischemic mitral regurgitation than in the group with primary valvular lesions (10.3+/-1.1% vs 21.9+/-1.6%; p<0.01). Regional annular areas of the six sectors were homogeneously larger in group 2 than in group 3. The sector P3 did not show larger area than the other ones. The degree of MR, as assessed by the volumes of regurgitant jets, was higher in the group with primary valvular lesions than in the patients with IMR (32.6+/-13.4 cm(3) vs 23.1+/-11.1cm(3); p<0.01). CONCLUSIONS: This study showed that annular enlargement in patients with IMR affects the different annular regions to the same extent. An ideal surgical repair of IMR should be individually tailored after quantitative assessment measurement of geometry and function of each single component of the mitral valve complex.

Aged↗
PubMed2006

Monitoring of lung motion in patients with malignant pleural mesothelioma using two-dimensional and three-dimensional dynamic magnetic resonance imaging: comparison with spirometry.

PURPOSE: To monitor lung motion in patients with malignant pleural mesothelioma (MPM) before and after chemotherapy (CHT) using 2-dimensional (2D) and 3-dimensional (3D) dynamic MRI (dMRI) in comparison with spirometry. METHODS AND MATERIALS: Twenty-two patients with MPM were examined before CHT, as well as after 3 and 6 CHT cycles (3 months and 6 months) using 2D dMRI (trueFISP; 3 images/s) and 3D dMRI (FLASH 3D, 1 slab (52 slices)/s) using parallel imaging in combination with view-sharing technique. Maximum craniocaudal lung dimensions (2D) and lung volumes (3D) were monitored, separated into the tumor-bearing and nontumor-bearing hemithorax. Vital capacity (VC) was measured for comparison using spirometry. RESULTS: Using 2D technique, there was a significant difference between the tumor-bearing and the nontumor-bearing hemithorax before CHT (P < 0.01) and after 3 CHT cycles (P < 0.05), whereas difference was not significant in the second control. In the tumor-bearing hemithorax, mobility increased significantly from the status before versus after 3 CHT cycles (4.1 +/- 1.1 cm vs. 4.8 +/- 1.4 cm, P < 0.05). Using 3D technique, at maximum inspiration, the volume of the tumor-bearing hemithorax was 0.6 +/- 0.4 L and of the nontumor-bearing hemithorax 1.25 +/- 0.4 L before CHT. In the follow-up exams, these volumes changed to 1.05 +/- 0.4 L (P < 0.05) and 1.4 +/- 0.5 L, respectively. Using spirometry, there was no significant change in VC (1.9 +/- 0.4 L vs. 2.2 +/- 0.7 L vs. 2.2 +/- 0.9 L). CONCLUSION: dMRI is capable of monitoring changes in lung motion and volumetry in patients with MPM not detected by global spirometry. Thus, dMRI is proposed for use as a further measure of therapy response.

Aged↗
PubMed2005

Assessment of reproducibility and stability of different breath-hold maneuvres by dynamic MRI: comparison between healthy adults and patients with pulmonary hypertension.

To assess the stability and reproducibility of different breath-hold levels in healthy volunteers and patients using dynamic MRI (dMRI). In ten healthy volunteers and ten patients with pulmonary hypertension (PH) and normal lung function craniocaudal intrathoracic distances (CCD) were measured during inspiratory and expiratory breath-hold (15 s) (in healthy volunteers additionally at a self-chosen mid-inspiratory breath-hold) using dMRI (trueFISP, three images/s). To evaluate stability and intraobserver reproducibility of the different breath-hold levels, CCDs, time-distance curves, confidence intervals (CIs), Mann-Witney U test and regression equations were calculated. In healthy volunteers there was a substantial decrease of the CCD during the inspiratory breath-hold in contrast to the expiratory breath-hold. The CI at inspiration was 2.84+/-1.28 in the right and 2.1+/-0.68 in the left hemithorax. At expiration the CI was 2.54+/-1.18 and 2.8+/-1.48. Patients were significantly less able to hold their breath at inspiration than controls (P<0.05). In patients CI was 4.53+/-4.06 and 3.46+/-2.21 at inspiration and 4.45+/-4.23 and 4.76+/-3.73 at expiration. Intraobserver variability showed no significant differences either in patients or in healthy subjects. Reproducibility was significantly lower at a self-chosen breath-hold level of the healthy volunteers. DMRI is able to differentiate stability and reproducibility of different breath-hold levels. Expiratory breath-hold proved to be more stable than inspiratory breath-hold in healthy volunteers and patients.

Adult↗
PubMed2005

Influence of different breathing maneuvers on internal and external organ motion: use of fiducial markers in dynamic MRI.

PURPOSE: To investigate, with dynamic magnetic resonance imaging (dMRI) and a fiducial marker, the influence of different breathing maneuvers on internal organ and external chest wall motion. METHODS AND MATERIALS: Lung and chest wall motion of 16 healthy subjects (13 male, 3 female) were examined with real-time trueFISP (true fast imaging with steady-state precession) dMRI and a small inductively coupled marker coil on either the abdomen or thorax. Three different breathing maneuvers were performed (predominantly "abdominal breathing," "thoracic breathing," and unspecific "normal breathing"). The craniocaudal (CC), anteroposterior (AP), and mediolateral (ML) lung distances were correlated (linear regression coefficient) with marker coil position during forced and quiet breathing. RESULTS: Differences of the CC distance between maximum forced inspiration and expiration were significant between abdominal and thoracic breathing (p < 0.05). The correlation between CC distance and coil position was best for forced abdominal breathing and a marker coil in the abdominal position (r = 0.89 +/- 0.04); for AP and ML distance, forced thoracic breathing and a coil in the thoracic position was best (r = 0.84 +/- 0.03 and 0.82 +/- 0.03, respectively). In quiet breathing, a lower correlation was found. CONCLUSION: A fiducial marker coil external to the thorax in combination with dMRI is a new technique to yield quantitative information on the correlation of internal organ and external chest wall motion. Correlations are highly dependent on the breathing maneuver.

Abdomen↗
PubMed2005

Improved correlation of histological data with DCE MRI parameter maps by 3D reconstruction, reslicing and parameterization of the histological images.

Due to poor correlation of slice thickness and orientation, verification of radiological methods with histology is difficult. Thus, a procedure for three-dimensional reconstruction, reslicing and parameterization of histological data was developed, enabling a proper correlation with radiological data. Two different subcutaneous tumors were examined by MR microangiography and DCE-MRI, the latter being post-processed using a pharmacokinetic two-compartment model. Subsequently, tumors were serially sectioned and vessels stained with immunofluorescence markers. A ray-tracing algorithm performed three-dimensional visualization of the histological data, allowing virtually reslicing to thicker sections analogous to MRI slice geometry. Thick slices were processed as parameter maps color coding the marker density in the depth of the slice. Histological 3D reconstructions displayed the diffuse angioarchitecture of malignant tumors. Resliced histological images enabled specification of high enhancing areas seen on MR microangiography as large single vessels or vessel assemblies. In orthogonally reconstructed histological slices, single vessels were delineated. ROI analysis showed significant correlation between histological parameter maps of vessel density and MR parameter maps (r=0.83, P=0.05). The 3D approach to histology improves correlation of histological and radiological data due to proper matching of slice geometry. This method can be used with any histological stain, thus enabling a multivariable correlation of non-invasive data and histology.

Algorithms↗
PubMed2005

The simplicity of metazoan cell lineages.

Developmental processes are thought to be highly complex, but there have been few attempts to measure and compare such complexity across different groups of organisms. Here we introduce a measure of biological complexity based on the similarity between developmental and computer programs. We define the algorithmic complexity of a cell lineage as the length of the shortest description of the lineage based on its constituent sublineages. We then use this measure to estimate the complexity of the embryonic lineages of four metazoan species from two different phyla. We find that these cell lineages are significantly simpler than would be expected by chance. Furthermore, evolutionary simulations show that the complexity of the embryonic lineages surveyed is near that of the simplest lineages evolvable, assuming strong developmental constraints on the spatial positions of cells and stabilizing selection on cell number. We propose that selection for decreased complexity has played a major role in moulding metazoan cell lineages.

Algorithms↗
PubMed2005

Intraoperative assessment of right ventricular volume and function.

OBJECTIVE: Right ventricular function is an important aspect of global cardiac performance which affects patients' outcome after cardiac surgery. Due to its geometrical complexity, the assessment of right ventricular function is still a very difficult task. Aim of this study was to investigate the value of a new technique for intraoperative assessment of right ventricle based on transesophageal 3D-echocardiography, and to compare it to volumetric thermodilution by using a new generation of fast response thermistor pulmonary artery catheters. METHODS: Twenty-five patients with coronary artery disease underwent 68 intraoperative measurements by 3D-echocardiography and thermodilution simultaneously. Following parameters were analysed: right ventricular end-diastolic volume (RVEDV), end-systolic volume (RVESV) and ejection fraction (RVEF). Pulmonary, systemic and central venous pressures were simultaneously recorded. Segmentation of right ventricular volumes were obtained by the 'Coons-Patches' technique, which was implemented into the EchoAnalyzer, a multitask system developed at our institution for three-dimensional functional and structural measurements. RESULTS: Right ventricular volumes obtained by 3D-echocardiography did not show significant correlations to those obtained by thermodilution. Volumetric thermodilution systematically overestimates right ventricular volumes. Significant correlations were found between RVEF measured by 3D-echocardiography and those obtained by thermodilution (r=0. 93; y=0.2+0.80x; SEE=0.03; P<0.01). Bland-Altmann analysis showed that thermodilution systematically underestimates RVEF. The bias for measuring RVEF was +15.6% with a precision of +/-4.3%. The patients were divided into two groups according to left ventricular function. The group of patients with impaired function showed significantly lower right ventricular ejection fraction (44.1+/-4.6 vs. 55.1+/-3.9%; P<0.01). CONCLUSIONS: Three-dimensional echocardiography provides a useful non-invasive tool for intraoperative and serial assessment of right ventricular function. This new technique, which overcomes the limitations of previous methods, may offer key insights into management and outcome of patients with severe impairment of cardiac function.

Aged↗
PubMed2005

The medical imaging interaction toolkit.

Thoroughly designed, open-source toolkits emerge to boost progress in medical imaging. The Insight Toolkit (ITK) provides this for the algorithmic scope of medical imaging, especially for segmentation and registration. But medical imaging algorithms have to be clinically applied to be useful, which additionally requires visualization and interaction. The Visualization Toolkit (VTK) has powerful visualization capabilities, but only low-level support for interaction. In this paper, we present the Medical Imaging Interaction Toolkit (MITK). The goal of MITK is to significantly reduce the effort required to construct specifically tailored, interactive applications for medical image analysis. MITK allows an easy combination of algorithms developed by ITK with visualizations created by VTK and extends these two toolkits with those features, which are outside the scope of both. MITK adds support for complex interactions with multiple states as well as undo-capabilities, a very important prerequisite for convenient user interfaces. Furthermore, MITK facilitates the realization of multiple, different views of the same data (as a multiplanar reconstruction and a 3D rendering) and supports the visualization of 3D+t data, whereas VTK is only designed to create one kind of view of 2D or 3D data. MITK reuses virtually everything from ITK and VTK. Thus, it is not at all a competitor to ITK or VTK, but an extension, which eases the combination of both and adds the features required for interactive, convenient to use medical imaging software. MITK is an open-source project (www.mitk.org).

Algorithms↗
PubMed2005

Evaluation of lung volumetry using dynamic three-dimensional magnetic resonance imaging.

RATIONALE AND OBJECTIVES: We sought to investigate lung volume and surface measurements during the breathing cycle using dynamic three-dimensional magnetic resonance imaging (3D MRI). MATERIALS AND METHODS: Breathing cycles of 20 healthy volunteers were examined using a 2D trueFISP sequence (3 images/second) in combination with a model and segmented 3D FLASH sequence (1 image/second) MR images using view sharing. Segmentation was performed semiautomatically using an interactive region growing technique. Vital capacity (VC) was calculated from MRI using the model (2D) and counting the voxels (3D) and was compared with spirometry. RESULTS: VC from spirometry was 4.9+/-0.9 L, 4.4+/-1.2 L from 2D MRI measurement, and 4.7+/-0.9 L for 3D MRI. Using the 3D technique, correlation to spirometry was higher than using the 2D technique (r>0.95 vs. r>0.83). Using the 3D technique, split lung volumes and lung surface could be calculated. There was a significant difference between the left and right lung volume in expiration (P<0.05). CONCLUSIONS: Dynamic 3D MRI is a noninvasive tool to evaluate split lung volumes and lung surfaces during the breathing cycle with a high correlation to spirometry.

Adult↗
PubMed2004

Treatment of painful vertebral fractures by kyphoplasty in patients with primary osteoporosis: a prospective nonrandomized controlled study.

UNLABELLED: This study investigates the effects of kyphoplasty on pain and mobility in patients with osteoporosis and painful vertebral fractures compared with conventional medical management. INTRODUCTION: Pharmacological treatment of patients with primary osteoporosis does not prevent pain and impaired activity of patients with painful vertebral fractures. Therefore, we evaluated the clinical outcome after kyphoplasty in patients with vertebral fractures and associated chronic pain for >12 months. MATERIALS AND METHODS: Sixty patients with primary osteoporosis and painful vertebral fractures presenting for >12 months were included in this prospective, nonrandomized controlled study. Twenty-four hours before performing kyphoplasty, the patients self-determined their inclusion into the kyphoplasty or control group so that 40 patients were treated with kyphoplasty, whereas 20 served as controls. This study assessed changes in radiomorphology, pain visual analog scale (VAS) score, daily activities (European Vertebral Osteoporosis Study [EVOS] score), number of new vertebral fractures, and health care use. Outcomes were assessed before treatment and at 3 and 6 months of follow-up. All patients received standard medical treatment (1g calcium, 1000 IE vitamin D(3), standard dose of oral aminobisphosphonate, pain medication, physical therapy). RESULTS: Kyphoplasty increased midline vertebral height of the treated vertebral bodies by 12.1%, whereas in the control group, vertebral height decreased by 8.2% (p = 0.001). Augmentation and internal stabilization by kyphoplasty resulted in a reduction of back pain. VAS pain scores improved in the kyphoplasty group from 26.2 +/- 2 to 44.2 +/- 3.3 (SD; p = 0.007) and in the control group from 33.6 +/- 4.1 to 35.6 +/- 4.1 (not significant), whereas the EVOS score increased in the kyphoplasty group from 43.8 +/- 2.4 to 54.5 +/- 2.7 (p = 0.031) and in the control group from 39.8 +/- 4.5 to 43.8 +/- 4.6 (not significant). The number of back pain-related doctor visits within the 6-month follow-up period decreased significantly after kyphoplasty compared with controls: mean of 3.3 visits/patient in the kyphoplasty group and a mean of 8.6 visits/patient in the control group (p = 0.0147). CONCLUSIONS: The results of this study show significantly increased vertebral height, reduced pain, and improved mobility in patients after kyphoplasty. Kyphoplasty performed in appropriately selected osteoporotic patients with painful vertebral fractures is a promising addition to current medical treatment.

Adult↗
PubMed2004

Genetic networks in the early development of Caenorhabditis elegans.

One of the best-studied model organisms in biology is Caenorhabditis elegans. Because of its simple architecture and other biological advantages, considerable data have been collected about the regulation of its development. In this review, currently available data concerning the early phase of embryonic development are presented in the form of genetic networks. We performed computer simulations of regulatory mechanisms in embryonic development, and the results are described and compared with experimental observations.

Animals↗
PubMed2004

Implementing a full-feature PACS solution in accordance with the IHE technical framework: the CHILI approach.

RATIONALE AND OBJECTIVES: During the last 4 years, Integrating the Healthcare Enterprise (IHE) has worked in establishing a reliable integrated environment for medical imaging devices and other clinical information systems by using existing industry standards such as Digital Imaging and Communication in Medicine (DICOM) and Health Level Seven (HL7). Because IHE is organized and driven by professional organizations representing both buyers and vendors, it was able to define a common language for the various health care parties who are involved in the integration process. Thus IHE offers a rigorously organized technical framework that provides a comprehensive guide for a coordinated implementation of information standards. MATERIALS AND METHODS: A multistage plan for incorporating the IHE elements while scaling up general-purpose workstations with teleradiology functionalities to a full-feature picture archiving and communication system (PACS) solution was created. To introduce a pragmatic example, the plan approach was applied to the CHILI workstations (CHILI, Heidelberg, Germany). To implement the proposed plan in making various legacy systems comply with IHE, the effects of available resources and market needs on the plan are discussed. Most implementation challenges and problems were overcome using generic design approaches and well-designed DICOM utilities. RESULTS: On completion of the first stage, the PACS viewer and reporting workstations were IHE-compliant. In addition, the plan facilitates the conformance process while maintaining the planned software development cycle. CONCLUSION: Based on these positive results and the practical experience acquired during the first stage, further stages will be completed to provide the system with the required plug-and-play interoperability among systems from different vendors.

Data Display↗
PubMed2002

Navigation and image-guided HBP surgery: a review and preview.

Image-guided surgery and navigation have resulted from convergent developments in radiology, teletransmission, and computer science. Patient selection and preoperative planning in hepatobiliary-pancreatic (HBP) surgery rely on preoperative imaging. The operative procedure is finally led by the fusion of additional information gained by the palpating hand and intraoperative ultrasound. Despite advances in reducing morbidity and mortality, decisions are often hardly quantifiable and are restricted to super-specialists in HBP surgery. New developments in computed tomography (CT) and magnetic resonance imaging (MRI) technology have led to the possibility of the volumetric prediction of liver resections. These data can be shared via telemedicine and used for simulation and training. Three-dimensional (3D) reconstructions have led to a better topologic understanding of tumor-vascular tree relations in the individual patient. With the increasing use of ablative procedures and laparoscopy, intraoperative imaging and navigation will hold increasing significance for the HBP surgeon. Flat screen monitors adjacent to the surgical field present computer-generated 3D virtual liver resection proposals which can be transferred into the real liver. The main obstacles in HBP navigation are the flexibility and mobility of the target organ. Intrahepatic and surface markers seem to be mandatory for computer-navigated surgery. The first feasibility studies are promising.

Bile Ducts↗
PubMed2002

ROPES: a semiautomated segmentation method for accelerated analysis of three-dimensional echocardiographic data.

Echocardiography (cardiac ultrasound) is today the predominant technique for quantitative assessment of cardiac function and valvular heart lesions. Segmentation of cardiac structures is required to determine many important diagnostic parameters. As the heart is a moving organ, reliable information can be obtained only from three-dimensional (3-D) data over time (3-D + time = 4-D). Due to their size, the resulting four-dimensional (4-D) data sets are not reasonably accessible to simple manual segmentation methods. Automatic segmentation often yields unsatisfactory results in a clinical environment, especially for ultrasonic images. We describe a semiautomated segmentation algorithm (ROPES) that is able to greatly reduce the time necessary for user interaction and its application to extract various parameters from 4-D echocardiographic data. After searching for candidate contour points, which have to fulfill a multiscale edge criterion, the candidates are connected by minimizing a cost function to line segments that then are connected to form a closed contour. The contour is automatically checked for plausibility. If necessary, two correction methods that can also be used interactively are applied (fitting of other line segments into the contour and searching for additional candidates with a relaxed criterion). The method is validated using in vivo transesophageal echocardiographic data sets.

Algorithms↗